i PRODUCTIVITY OF SUNFLOWER HYBRIDS AS INFLUENCED BY SULPHUR-NITROGEN NUTRITION AND VARYING PLANT POPULATION By MUHAMMAD ISHFAQ M.Sc. (Hons.) Agricultue A thesis submitted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY IN AGRONOMY FACULTY OF AGRICULTURE UNIVERSITY OF AGRICULTURE FAISALABAD, PAKISTAN 2010
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i
PRODUCTIVITY OF SUNFLOWER HYBRIDS AS INFLUENCED BY SULPHUR-NITROGEN
NUTRITION AND VARYING PLANT POPULATION
By
MUHAMMAD ISHFAQ
M.Sc. (Hons.) Agricultue
A thesis submitted in partial fulfillment of the requirements for the degree of
DOCTOR OF PHILOSOPHY
IN
AGRONOMY
FACULTY OF AGRICULTURE UNIVERSITY OF AGRICULTURE
FAISALABAD, PAKISTAN 2010
ii
To
The controller of Examinations, University of Agriculture, Faisalabad
We the supervisory committee, certify that contents and form of thesis
submitted by Mr. Muhammad Ishfaq have been found satisfactory and recommend
that it be processed for evaluation by the external Examiner(s) for the award of degree.
SUPERVISORY COMMITTEE
CHAIRMAN ______________________ (DR. ASGHAR ALI) MEMBER _______________________ (DR. ABDUL KHALIQ)
MEMBER ________________________ (DR. MUHAMMAD YASEEN)
iii
DECLARATION
I hereby declare that the contents of the thesis, “Productivity of sunflower hybrids as
influenced by sulphur-nitrogen nutrition and varying plant population” are product of
my own research and no part has been copied from any published source (except the
references, standard mathematical or genetic models/equations/formulate/protocols
etc.). I further declare that this work has not been submitted for award of any other
diploma/degree. The university may take action if the information provided is found
inaccurate at any stage. (In case of any default, the scholar will be proceeded against as
per HEC plagiarism policy).
Signature of the Student
Muhammad Ishfaq
85-ag-1479 Ph. D student
Dept. Agronomy
iv
DADICATED TO
my parents
my wife
my kids
(Talha Sandhu, Hamza Sandhu and Mashaf Ishfaq)
v
ACKNOWLEDGEMENTS
Allah Almighty the eternal of the universe. All worships and praises are only for the Lord of creation, the most Merciful, Beneficent, Gracious and Compassionate whose numerous blessings enabled me to pursue and perceive higher ideas of life. I offer my humblest thanks to the Holy Prophet Muhammad (S.A.W.) who is forever a torch of guidance and knowledge for the humanity as a whole.
I feel highly honored to express the deep sense of gratitude to my supervisor Professor Dr. Asghar Ali, Department of Agronomy, University of Agriculture, Faisalabad, under whose kind supervision, sincere help and inspiring guidance the research work presented in this dissertation was carried out.
Special thanks are extended to the Supervisory Committee Members Associate Professor Dr. Abdul Khaliq, Department of Agronomy whose animate directions, observant pursuit, scholarly criticism, cheering perspective and enlightened supervision not improved the quality of this exposition but also my overall understanding of this research project, and Associate Professor Dr. Muhammad Yaseen, Institute of Soil and Environmental Sciences for their precious advice and energizing support during the course of present studies.
I extend my admirations and appreciation to my friends, Dr.Arif Raza, Dr.Ishtiaq Hassan, Dr. Arif Rehman, Dr. Azhar Mahmood and Dr.Muhammad Akram who gave me not only their excellent cooperation but also a lot of smiles and enjoyable moments throughout my study period. I owe a special gratitude to my fellow Dr. Manzoor Ahmad Gill who very graciously extended all help and cooperation in carrying out trials and managing this manuscript.
I owe a debt to my cooperating/inspiring wife whose moral support and patience has been invaluable in aiding me to complete this thesis.Finally, I extend my heartiest and sincere sense of gratitude to my loving mother, brothers, sisters, , beloved sons (Talha) and Hamza) daughter (Mashaf Ishfaq) for their prayers for my success. (MUHAMMAD ISHFAQ)
vi
TABLE OF CONTENTS
CHAPTER TITLE PAGE ACKNOWLEDGEMENTS v CONTENTS vi LIST OF TABLES xi LIST OF FIGURES xiv ABSTRACT xvi 1 INTRODUCTION 1-5 2 REVIEW OF LITERATURE 6-26 2.1. Nitrogen in relation to plant growth 6 2.1.1. N nutrition of sunflower 7 2.1.1.1. Nitrogen in relation to yield and yield components 8 2.1.1.2. Nitrogen in relation to achene-oil quality 9-10 2.2.. Sulphur and plant growth 11 2.2. 1 Sulphur nutrition of sunflowers 12 2.2.1.1. Agronomic and yield traits 12-13 2.2.1.2. Sulphur and achene-oil quality 14 2.3. Interactive effects of N and sulphur 15 2.4. Nutrient uptake by sunflower 16 2.5. Performance of diverse sunflower hybrids 17-19 2.6. Row spacing and plant density 20-21
2.7. Canopy development, light interception and radiation use efficiency
22-23
2.8 Oil yield and its composition in sunflower seed 24-26 3 MATERIALS AND METHODS 27-37 3.1 Site and soil 28 3.1.1 Mechanical analysis. 28 3.1.2. Chemical analysis 28 3.1.2.1. pH of saturated soil paste 28 3.1.2.2 Electrical conductivity of saturated soil extracts( ECe ) 28 3.1.2.3. Organic Matter 28 33.1.2.4 Total Nitrogen 28 3.1.2.5. Available Phosphorus 28 3.1.2.6 Available sulphur 28 3.2 Metrological data 29 3.3 Experimental details 30
3.3.1 Experiment1Response of agro-physiological traits of autumn planted sunflower grown under varying sulphur-nitrogen nutrition.
30
3.3.2 Experiment II: Radiation interception, radiation use 31
vii
efficiency and productivity of different genotypes of sunflower under varying row spacing/planting densities
3.3.3 Crop husbandry 31 3.4. Data recorded 32 3.4.1. Agronomic and yield related traits 32-33 3.4.2. Growth and development 33 3.4.2.1 Sampling 34 3.4.2.2. Leaf area index (LAI) 34 3.4.2.3. Leaf area duration (days) 34 3.4.2.4. Crop growth rate (g m-2 day-1) 34 3.4.2.5. Net assimilation rate (g m-2 day-1) 34 3.4.2.6. Light interception (MJm-2 ) 35 3.4.2.7. Radiation use efficiency (g MJ-1) 35 3.4.3. Achene oil quality traits 35 3.4.3.1 Achene oil content (%) 35 3.4.3.2. Protein content (%) 35 3.4.3.3. Achene fatty acid profile (%) 35 3.4.4 Nutrient uptake pattern (kg ha-1) 36 3.4.4.1 Sample preparation: 36 3.4.4.2. Nitrogen uptake(kg ha-1) 36 3.4.4.3. Phosphorus uptake (kg ha-1) 36 3.4.4.4. Potassium uptake (kg ha-1) 36 3.4.4.5. Determination of sulphur uptake (kg ha-1) 37 3.5. Statistical analysis 37
4 RESULTS AND DISCUSSION 38-176
4.1
Experiment1:Response of agro-physiological traits of autumn planted sunflower grown under varying sulphur-nitrogen nutrition
38
4.1.1. Agronomic and yield related traits 38 4.1.1.1. Number of plants m-2 38 4.1.1.2 Plant height at maturity 38 4.1.1.3 Stem diameter 41 4.1.1.4 Head diameter 43 4.1.1.5 Number of achenes head-1 45 4.1.1.6. 1000 achene weight 49 4.1.1.7. Stover yield 51 4.1.1.8 Achene yield 51 4.1.1.9. Harvest index (%) 58 4.1. 2. Growth 58 4.1.2.1 Leaf area index 58
4.2 Experiment II: Radiation interception, radiation use efficiency and productivity of different genotypes sunflower under varying row spacing/planting densities
121
4.2.1 Agronomic traits 121 4.2.1.1 Number of plants m-2 121 4.2.1.2 Number of days taken to maturity 121 4.2.1.3 Plant height 124 4.2.1.4 Stem diameter 124 4.2.1.5 Head diameter 127 4.2.1.6 Number of achenes per head 129 4.2.1.7 Number of achenes m-2 131 4.2.1.8 1000-achene weight 133 4.2.1.9 Achene yield 135 4.2.1.10 Stover yield 137 4.2.1.11. Harvest Index (%) 137 4.2.2 Growth 140 4.2.2.1. Leaf area index 140 4.2.2.2 Crop growth rate 143 4.2.2.3 Net assimilation rate 148 4.2.2.4 Dry matter accumulation 148 4.2.2.5 Leaf area duration 154
Textural class of the soil was examined by Bouyoucos hydrometer method and the
international triangle was used to determine the soil textural class (Moodie et al., 1959).
3.1.2. Chemical analysis:
Analysis of the soil was carried out to record the chemical characteristics by following
standard procedures ( Homer and Pratt ,1961).
3.1.2.1. pH of saturated soil paste:
About 250 g of soil was saturated with distilled water. The paste was allowed to
stand for 1 h and pH was recorded by pH meter (Kent Eil 7015) with glass electrode
using buffer of 4 and 9 pH as standards (Method 21a).
3.1.2.2. Electrical conductivity of saturated soil extracts (ECe):
Saturated soil extract was taken by using vacuum pump (Method 3a) and its
electrical conductivity was measured using digital conductivity meter (Model Jenway
4070).
3.1.2.3. Organic matter:
One gram of soil sample was mixed with 10 ml 1 N potassium dichromate
solution and 20 ml concentrated H2SO4 (commercial). To this, 150 ml of distilled water
and 25 ml of 0.5 N FeSO4 solutions were added and the excess was titrated with 0.1 N
potassium permanganate solutions to pink end point (Moodie et al., 1959).
3.1.2.4 Total nitrogen:
Nitrogen was determined by Gunning and Hibbard’s method of H2SO4 digestion
and distillation of NH3 into 4% H3BO4 by macro Kjeldahl apparatus (Jackson, 1962).
3.1.2.5. Available phosphorus:
Phosphorus was determined by taking 5 g soil and 10 ml N NaHCO3 solution
adjusted at pH 8.5. Five milliliter of clear filtrate was taken in 25 ml volumetric flask and
potassium tartrate and sulphuric acid were added. Color intensity was measured on
spectrophotometer at 880 nm (Watanade and Olsen, 1965).
3.1.2.6 Available sulphur:
Available sulphur (SO4) was determined following the procedure of Beardsley and
Lancaster (1960).
29
3.2 METROLOGICAL DATA:
Climatic data as temperature, rainfall, humidity, and net radiation for the both
cropping seasons were collected from the metrological station located at University of
Agriculture, Faisalabad. Weather summary for the growing years i.e 2006-07 is exhibited
in Fig. 3.1.
a.
Tem
pera
ture
(C
)
Weeks of the month
b.
Tem
pera
ture
(C
)
Weeks of the month
R.H
. (%
), R
ainf
all (
mm
)
Fig. 3.1. Meteorological data during year (a) 2006 (b) 2007.
30
3.3. EXPERIMENTAL DETAILS
A set of two experiments was conducted to study the influence of varying levels
of sulphur and nitrogen nutrition on autumn planted hybrid sunflower in Experiment I,
and to quantify the developmental and agronomic traits of three sunflower hybrids when
sown in different planting densities under varying row spacing (Experiment II). Both the
studies were carried out for two years (2006 and 2007). The crop was planted on 15th.of
August during year 2006 and on 16th August during 2007. Experimental details for both
the studies are given as under.
3.3.1. Experiment 1: Response of agro-physiological traits of autumn planted sunflower grown under varying sulphur-nitrogen nutrition
In this experiment four levels of each sulphur and nitrogen fertilizers were tested
as per following treatments.
Treatments:
A. Sulphur (kg ha-1):
S1 = 0 (control)
S2 = 40
S3 = 80
S4 = 120
B. Nitrogen (kg ha-1):
N1 = control
N2 = 100
N3 = 140
N4 = 180
The experiment was laid out in randomized complete block design with factorial
arrangement and replicated thrice. Net plot size was 4.5 m x 7.0 m.
31
3.3.2 Experiment II: Radiation interception, radiation use efficiency and productivity of different genotypes of sunflower under varying row spacing/planting densities
In this experiment, three sunflower hybrids owing to different maturity groups
were grown at different row spacing. The treatments were as under:
A. Hybrids (main plots):
H1 = FH-331 (early maturing)
H2 = SF-187 (medium maturing)
H3 = Hysun-33 (late maturing)
B. Row spacing (sub plots):
S1= 45 cm apart rows (98765 plants ha-1)
S2= 60 cm apart rows (74074 plants ha-1)
S3 = 75 cm apart rows (59259 plants ha-1)
Three sunflower hybrids were selected on the basis of their maturity as noted in
the parenthesis with respective hybrids. SF-187 (medium maturing) hybrid is on US
origin, while Hysun-33 (late maturing) is Australian origin. FH-331 (early maturing) is
locally developed hybrid. Seeds of all the hybrids were purchased from local
representatives of the companies marketing these hybrids in the country. The experiment
was laid down in randomized complete block design with split plot arrangement and
replicated three times. Six rows of each hybrid were sown at row spacing of 45 cm
(98765 plants ha-1), 60 cm (74074 plants ha-1) and 75 cm (59259 plants ha-1) with a
uniform plant to plant distance of 22.5 cm in all row spacing.
3.3.3 CROP HUSBANDRY
For the preparation of seed bed, pre-soaking irrigation of 10 cm was applied. For
the achievement of excellent germination of sunflower seed, soil was cultivated 4 times
with tractor mounted cultivator each followed by planking. Dibbler was used for seed
placement of the seeds at proper depth in the field. At 4-leaf stage extra plants were
uprooted to maintain plant to plant distance of 22.5 cm.. In Experiment I, fertilizer dose
of P2O5 and K2O was applied at 100 and 60 kg ha-1, respectively in the form of di-
ammonium phosphate and murate of potash. Sulphur and nitrogen were applied in the
form of urea and gypsum (20% S) as per treatment. For experiment II, recommended dose
of NPK (140-100-60 kg ha-1) was applied. and plant population was maintained as per
32
treatments. In each case, half of N and all phosphorus, potash and sulphur were applied at
sowing, while remaining nitrogen was applied with 2nd irrigation. A uniform and
recommended production package for sunflower crop was applied for all the treatments.
3.4. DATA RECORDED
Data on various growth, developmental, agronomic and yield traits were recorded
in due course of studies to quantify the response of sunflower to different treatments. The
detailed procedures are given as under.
3.4.1. Agronomic and yield related traits:
Following agronomic and yield traits were observed during both the years.
1. Number of plants at maturity (m-2)
2. Plant height at maturity (cm)
3. Stem diameter (cm)
4. Head diameter (cm)
5. Number of achenes per head
6. 1000-achene weight (g)
7. Achene yield (kg ha-1)
8. Oil yield (kg ha-1)
9. Stover yield (kg ha-1)
10. Harvest index (%)
The procedures adopted for recording data on various agronomic and yield
related parameters are described as under:
a. Number of plants per plot at maturity:
Total numbers of plants was counted at harvest in each plot and are reported m-2
basis.
b. Plant height (cm):
Ten randomly selected plants were selected from each plot and their height was
measured with tape was averaged to represent plant height.
c. Stem diameter (cm):
At final harvesting, vernier caliper was used to determine stem diameter of ten
randomly selected plants at base, middle and top of each stem and then was averaged to
compute stem diameter in cm.
33
d. Head diameter (cm):
Diameter of 10 randomly selected heads were measured in cm with the help of a
measuring tape and then averaged.
e. Number of achenes per head:
After manual threshing, the heads of 10 randomly chosen plants were separated
and accounted for total achenes in these heads.
f. 1000-achene weight (g):
From the seed lot of every plot five samples, each of 1000-achenes were randomly
selected and then recorded their weight and mean 1000-achene weight was computed.
g. Achene yield (kg ha-1):
Central two rows from each experimental unit were harvested at physiological
maturity and the heads were separated from stalks. Then achene yield was recorded after
sun-drying and then with manual threshing of the crop. The random achene samples were
taken from each plot to determine the Achene-moisture contents were recorded with a
moisture meter and then 10% moisture content was adjusted for presentation of final
achene yield in kg ha-1.
h. Oil yield (kg ha-1):
Oil content (%) determined for each experimental unit was multiplied with achene yield
of respective plot to compute the oil yield on ha basis.
i. Stalk yield (kg ha-1):
Two central rows leaving the border from both sides were selected and then weighed all the stalks for recording of the stalk yield.
j. Harvest index (%)
Harvest index was computed as the ratio of achene yield to biological yield and
calculated as follows.
Harvest index (%) = (Achene yield/biological yield) x 100
3.4.2. GROWTH AND DEVELOPMENT:
Data were recorded to compute the following parameters.
1. Leaf area index (LAI)
2. Leaf area duration (days)
3. Crop growth rate (g m-2 day-1)
4. Mean net assimilation rate (g m-2 day-1)
34
5. Light interception (MJm-2)
6. Radiation use efficiency (g MJ-1)
3.4.2.1. Sampling:
Plant sampling was done fortnightly starting from 30 days after sowing and total five
harvests were made. After leaving appropriate borders, five plants representing each plot
were clipped from ground surface, and leaves, stem and head (when appeared) were
separated and their fresh weights recorded. After this, samples were oven dried to a
constant dry weight at 75 °C. The procedure for computing various attributes are
described below.
3.4.2.2. Leaf area index (LAI):
From above sampling (Section 3.4.2.1) leaves were separated, fresh weight
recorded at each sampling and a sub-sample of 20 g was used to measure leaf area by a
leaf area meter (DT Area Meter, model MK2). Total leaf area was computed after making
calculations of total leaf dry weight/s. Leaf area index (LAI) was calculated by using the
formula given by Watson (1947).
LAI = Leaf area/land area 3.4.2.3. Leaf area duration (days):
LAD (leaf area duration) was measured by using the formulae suggested by Hunt
(1978) as under:
LAD = (LAI1 + LAI2) x (t2-t1)/2, where, LAI1 and LAI2 are leaf area indices at
times t2 and t1, respectively.
3.4.2.4. Crop growth rate (g m-2 day-1):
Total dry weight of periodic samples was used to estimate crop growth rate as
proposed by Hunt (1978).
CGR = (W2-W1)/(t2-t1), where W1 and W1 are total dry weight per unit land area (g m-2) at time t1 and t2,respectively.
3.4.2.5. Net assimilation rate (g m-2 day-1):
Net assimilation rate was determined by using the formula given by Hunt (1978).
NAR = TDM/ LAD where TDM is total dry matter, and LAD is seasonal leaf area duration.
35
3.4.2.6. Light interception (MJm-2):
The fraction of radiation intercepted (Fi) by the green leaf area of the crop was
calculated for each plot using the exponential attenuation equation as suggested by
Monteith and Elston (1983).
Fi = 1-exp (-K x LAI) MJ m-2
where K is an extinction coefficient for total solar radiation. The K value of 0.75 was
used for sunflower (Lemeur, 1973). Values of Fi were multiplied with daily incident PAR
(Si) during the season to determine the amount of intercepted PAR (Sa).
Sa = Fi x Si Mj m-2
The amount of total PAR intercepted by the crop was calculated by multiplying Fi with
0.5 PAR of incident radiation (Szeiez, 1974).
3.4.2.7. Radiation use efficiency (g MJ-1):
Radiation use efficiency for TDM (RUE TDM) and grain yield (RUEGY) were
calculated as the ratio of total biomass and grain yield to cumulative intercepted PAR
(∑Sa).
RUETDM = TDM/∑Sa gMJ-1
RUEGY = Grain Yield/∑Sa gMJ-1
3.4.3. Achene oil quality traits:
Chemical analyses of achenes were carried out for determining the following
quality parameters.
1. Oil content (%)
2. Protein content (%)
3. Fatty acid profile
3.4.3.1 Achene oil content (%)
Achene oil content was determined by Soxhlet Fat Extraction method (AOAC,
1990).
3.4.3.2. Achene protein content (%):
Nitrogen in achenes was determined according to Kjeldahl method (Bremner,
1964) and then protein percentage was worked out as under:
Crude protein percentage=percent nitrogen multiplied by 6.25
3.4.3.3. Achene fatty acid profile (%):
Fatty acids were identified by Shamadzo Gas Liquid Chromatograph(GLC).
36
3.4.4 Nutrient uptake pattern (kg ha-1):
Leaf, stem and head at physiological maturity were analyzed chemically to
determine N, P K and S content for computing nutrient uptake by the crop under varying
growing conditions.
1. Nitrogen uptake in plant (kg ha-1)
2. Phosphorus uptake in plant (kg ha-1)
3. Potash uptake in plant (kg ha-1)
4. Sulphur uptake in plant (kg ha-1)
3.4.4.1 Sample preparation:
Oven dried plant samples of leave; stem and head were ground with an electric
grinder and then stored in clean dry plastic bags for further processing. The procedures
adopted for determination of the nutrients are summarized as under.
3.4.4.2. Nitrogen uptake (kg ha-1):
The nitrogen concentration (%) in leaves, stem and head were recorded separately by
micro Kjeldahl method (AOAC, 1990). The nitrogen uptake was then, calculated by
multiplying its concentration with dry matter of each of the leave, stem and head and then
total nitrogen uptake (kg ha-1) was computed.
3.4.4.3. Phosphorus uptake (kg ha-1):
Spectrophotometer was used to record the phosphorus concentration. The standard
curve was formed to determine phosphorus concentration (%) of each fraction of the plant
and then it was converted into plant uptake by multiplying it with dry weight of each part
(leave, stem and head). Finally, total phosphorus uptake (kg ha-1) was computed from
these parts.
3.4.4.4. Potassium uptake (kg ha-1):
Potassium was determined by flame photometer (Janway PEP-7).The
concentration of every plant part was multiplied with dry weight of respective fraction to
determine potassium uptake (kg ha-1). By adding uptake from all the three parts (leave,
head and stem), total potassium uptake was calculated.
3.4.4.5. Determination of sulphur uptake (kg ha-1):
A common procedure followed wet ashing (diacid digestion) of the plant parts
was practiced and the sulphate content in the digested material was determined by barium
sulphate turbidimetric method.
37
3.5. STATISTICAL ANALYSIS:
Data collected were statistically analyzed by using the Fisher’s analysis of
variance technique (Steel et al., 1997) and LSD test at 5% probability was used to
compare the difference/s among treatment’s means. Regression analysis was done to
estimate the existence of relationship between various traits and to quantify the same.
38
CHAPTER-IV
RESULTS AND DISCUSSION
4.1. Experiment 1: Response of agro physiological traits of autumn planted
sunflower (Helianthus annuus L.) grown under varying sulphur-nitrogen nutrition.
4.1.1. Agronomic and yield related traits
4.1.1.1. Number of plants m-2
Plant population per unit area provides basis for yield comparisons under variable
management systems. Number of plants at the time of harvest (Table 4.1) indicated that
different levels of sulphur and nitrogen fertilization did not alter plant population at
harvest during both years of experimentation. On an average plant population ranged
from 5.80 to 5.84 plants m-2.
Different combinations of sulphur and nitrogen fertilizers also showed non
significant influence of plant population at harvest (Table 4.1).
Uniform plant population at harvest under all treatment combinations may be
attributed to an even germination that is characteristic of present-day sunflower hybrids.
These findings are in confirmatory to the results of Saleem and Malik (2004) and Iqbal
(2008) who reported that fertilizer application did not influence final plant population of
sunflower. Uniform plant population at harvest under all treatment combinations may be
attributed to an even germination that is characteristic of present-day sunflower hybrids.
4.1.1.2 Plant height at maturity (cm)
Data regarding plant height as influenced by various treatments at maturity are
presented in Table 4.2.Sulphur application did not influence plant height of sunflower
significantly (P≤0.05) at maturity during both the years in these studies (Table 4.2).
However, there was an increasing trend with addition of sulphur over control. On an
average, plant height was 153.08 cm in plots without S as compared with 158.92 cm tall
plants recorded with 120 kg ha-1 S. Budhar et al. (2003) also reported non-significant
influence of sulphur application on plant height of sunflower, while Reddy and Singh
(1996) and Sing et al. (2000) stated that increasing levels of sulphur significantly
increased the plant height in sunflower.
39
Table 4.1. Influence of sulphur and nitrogen nutrition on plant population (m-2)
of sunflower.
Treatments 2006 2007 Mean
Sulphur levels (S)
S1= Control 5.87 5.88 5.88
S2= 40 kg ha-1 5.83 5.86 5.85
S3= 80 kg ha-1 5.85 5.85 5.85
S4= 120 kg ha-1 5.88 5.84 5.86
LSD at 5% NS NS
Nitrogen levels (N)
N1= Control 5.88 5.86 5.87
N 2= 100 kg ha-1 5.86 5.83 5.85
N 3= 140 kg ha-1 5.85 5.89 5.87
N 4= 180 kg ha-1 5.85 5.85 5.85
LSD at 5% NS NS
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
40
Table 4.2. Influence of sulphur and nitrogen nutrition on plant height (cm) of
Sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 157.55 151.08 153.08
S2= 40 159.94 154.72 157.33
S3= 80 162.93 155.62 159.28
S4= 120 161.92 155.91 158.92
LSD at 5% NS NS
Nitrogen (kg ha-1)
N1= Control 129.50 c 128.07 d 128.79
N 2= 100 161.33 b 153.44 c 157.39
N 3= 140 173.00 a 163.62 b 168.31
N 4= 180 178.00 a 172.19 a 175.10
LSD at 5% 5.24 7.04
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
41
Increasing levels of nitrogen enhanced plant height significantly (P≤0.05) over
control during both the years (Table 4.2). On an average, application of 100 kg ha-1 N
increased plant height by 22% while the increase was 31% for 140 kg ha-1 N over control.
Plant height did not increase further to significant extent with additional N application
during 2006 but increased significantly during 2007. Malik et al. (2004) and Ozer et al.
(2004) also observed increase in plant height with higher N doses, while Herdem (1999)
and Killi (2004) indicated non-significant impact of N application on plant height of
sunflower. Nitrogen plays a significant role in vegetative growth and development of
sunflower plant, and the positive response of plant height to N application has been
reported by Poonia (2002), Arif et al. (2003) and Akhtar (2004).
A non-significant interaction between sulphur and nitrogen fertilization was
observed during both the years, which showed that positive response of plant height to
nitrogen nutrition was not dependent on sulphur application.
4.1.1.3 Stem diameter (cm)
Stem diameter increased significantly with sulphur application only at medium
(80 kg ha-1) level during both the years of experimentation (Table 4.3). Response to S
application at low level (40 kg ha-1) was non-significant. Similarly stem diameter also
could not increase beyond medium S application level during both the years. On an
average, S application increased stem diameter by 6-8 percent over control.
Nitrogen application significantly increased stem diameter of sunflower (Table
4.3). On an average 28, 38 and 37 percent increase in stem diameter was recorded with
the application of N at 100, 140 and 180 kg ha-1, respectively. In fact, stem diameter did
not increase significantly (P≤0.05) beyond 140 kg ha-1 N during both years.
Different combinations of S and N fertilizer had a significant (P≤0.05) influence
on stem diameter of sunflower only during 2007 (Table 4.3). The thickest stems were
recorded with the application of ≥80 kg ha-1 S and ≥140 kg ha-1 N. The increase in stem
thickness with the increasing levels of nitrogen was also reported by Akhtar (2004) and
Khaliq (2004) who noted the maximum stem diameter with 150 and 200 kg ha-1 nitrogen
application, respectively. Iqbal (2008) also reported increase in stem girth as a
consequence of nitrogen application.
42
Table 4.3. Influence of sulphur and nitrogen nutrition on stem diameter (cm) of
sunflower
Treatments 2006 2007 Mean Sulphur (kg ha-1)
S1= Control 1.69 b 1.65 b 1.67
S2= 40 1.72 b 1.69 b 1.70
S3= 80 1.79 a 1.75 a 1.77
S4= 120 1.82 a 1.78 a 1.80
LSD at 5% 0.05 0.02
Nitrogen (kg ha-1)
N1= Control 1.40 c 1.37 c 1.38
N 2= 100 1.78 b 1.75 b 1.76
N 3= 140 1.92 a 1.89 a 1.90
N 4= 180 1.91 a 1.88 a 1.89
LSD at 5% 0.05 0.02
Interaction (S x N) NS
S1N1 1.35 1.32 i 1.34
S1N2 1.70 1.66 g 1.68
S1N3 1.87 1.83 cde 1.85
S1N4 1.83 1.80 def 1.82
S2N1 1.38 1.35 hi 1.37
S2N2 1.75 1.72 fg 1.77
S2N3 1.88 1.85 bcde 1.87
S2N4 1.87 1.84 bcde 1.86
S3N1 1.47 1.43 h 1.45
S3N2 1.78 1.75 efg 1.77
S3N3 1.95 1.92 abc 1.94
S3N4 1.94 1.91 abc 1.93
S4N1 1.41 1.37 hi 1.39
S4N2 1.89 1.86 abcd 1.88
S4N3 1.97 1.94 ab 1.96
S4N4 1.99 1.96 a 1.98
LSD at 5% NS 0.09
Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
43
4.1.1.4 Head diameter (cm)
Among different components, head diameter is of prime importance for yield
determination. Production potential of sunflower crop is determined by its head size.
Volume of the sunflower head contributes considerable share in final achene yield as it
influences both the number and weight of achenes.
Sulphur application significantly (P≤0.05) influenced the head diameter during
both the years (Table 4.4). During both the years head diameters increased initially with
sulphur application up to 80 kg ha-1 S but exhibited a declining trend with further increase
in S levels. On an average, head diameter increased by 6, 13 and 10 percent over control
with application of 40, 80 and 120 kg ha-1 sulphur, respectively.
Larger heads harvested with S application were associated with more number of
grains thus giving more yield (Hassan et al., 2007). In contrary, less number of grains
developed on smaller heads would not have faced any competition for assimilates thus
produced heavier individual grain weight. Singh (2000), Bhaghat et al. (2005) and Hassan
et al. (2007) also reported increasing trend of sunflower head diameters with increasing
sulphur fertilization.
Nitrogen application also increased head diameter of sunflower in these studies
during both the years (Table 4.4). However, the response was non significant beyond 140
kg ha-1 N during both the years. Application of 100, 140 and 180 kg ha-1 N recorded 51,
62 and 63 percent increase in head diameter, respectively over control during both the
years. On an average head diameter ranged from 10.98 cm to 17.91 cm. comparatively
smaller heads were produced during 2007.
Interactive effect of different combinations of sulphur and nitrogen nutrition was
significant only during 2007. Highest head diameter (18.73 cm) was produced with the
combination of sulphur and nitrogen at the rate of 80 kg ha-1and 140 kg ha-1 respectively.
Head diameters produced with the application of sulphur and nitrogen at 80 kg ha-1 each
were statistically at par with the former combination. The crop grown without sulphur and
nitrogen nutrition failed to achieve remarkable size of head and that was the minimum
size of head (9.34 cm). Overall, head diameter was in the range 9.36 cm to 18.73 cm.
There was a optimistic association between number of achene per head and head diameter
(cm) of the sunflower crop (Fig 4.1) and the common regression accounted for 95%
(95.34-94.83) of the variation in number of achenes per head owing to head diameter.
44
Table: 4.4. Influence of sulphur and nitrogen nutrition on head diameter (cm) of
sunflower hybrid.
Treatments 2006 2007 mean
Sulphur (kg ha-1)
S1= Control 14.68 c 14.78 b 14.73
S2= 40 15.94 b 15.31 b 15.63
S3= 80 16.92 a 16.32 a 16.62
S4= 120 16.46 ab 16.08 a 16.27
LSD at 5% 0.56 0.54
Nitrogen (kg ha-1)
N1= Control 11.25 c 10.71 c 10,98
N 2= 100 16.75 b 16.32 b 16.54
N 3= 140 17.94 a 17.70 a 17.82
N 4= 180 18.05 a 17.76 a 17.91
LSD at 5% 0.56 0.54
Interaction (S x N) NS
S1N1 9.50 9.43 i 9.47
S1N2 15.61 15.25 f 15.43
S1N3 16.79 17.12 cde 16.96
S1N4 16.82 17.34 cd 17.08
S2N1 11.00 9.97 hi 10.49
S2N2 16.57 16.10 ef 16.34
S2N3 18.00 17.29 cd 17.65
S2N4 18.18 17.87 abc 18.03
S3N1 12.00 10.60 h 11.30
S3N2 17.83 17.45 bcd 17.64
S3N3 18.83 18.73 a 18.78
S3N4 19.00 18.50 ab 18.75
S4N1 12.51 12.83 g 12.67
S4N2 16.99 16.48 de 16.74
S4N3 18.13 17.68 abc 17.91
S4N4 18.21 17.33 cd 17.77
LSD at 5% NS 1.08
Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
45
4.1.1.5. Number of achenes per head
Number of achenes per head has a direct bearing on final achene yield of
sunflower. Data (Table 4.5) showed that sulphur fertilization during 2006 did not
influence number of achenes per head. However, during 2007, S application increased the
number of achenes by 3% over control and the difference between lower S levels being
non-significant over control. Budhar et al. (2003) observed significant influence of
sulphur application on number of achenes in sunflower. The results of Bhaghat et al.
(2005) also supported the findings of present work. Larger heads harvested with S
application were associated with more number of grains thus giving more yield (Hassan
et al., 2007). In contrary, less number of grains developed on smaller heads would not
have faced any competition for assimilates thus produced heavier individual grain weight.
Data (Table 4.5) exhibited that number of achenes per head was positively
influenced by nitrogen application during both the years. During both the years,
application of 140 and 180 kg ha-1 N recorded highest and similar (P≤0.05) number of
achenes per head. On an average, N fertilization @at 100, 140 and 180 kg ha-1, increased
number of achenes by 20, 27 and 28 percent over control, respectively. Crop grown
without N developed very low number of achenes per head (615).
Different combinations of S and N did not vary significantly (P≤0.05) for number
of achenes per head during both years of experimentation in present studies. (Table 4.5).
Quantity of achenes per head is also optimistically linked with head size and
ultimately contributing towards final grain yield. Privileged grain yields designed for
greater N treatments are connected by means of higher grain number (Zubillaga et al.,
2002). There was an optimistic association between number of achenes per head and head
diameter of the sunflower crop (Fig 4.2) and the common regression accounted for 95%
(95.34-94.83) of the variation in number of achenes per head owing to head diameter.
Number of achenes per head was also positive associated with oil yield of sunflower (Fig.
4.3), and regression accounted for 86% (90-82) of the variation in oil yield of sunflower
owing to difference/s in number of achenes produced under various treatments in these
studies.
46
N
umbe
r of
ach
ene
per
head
y = 25.137x + 362.61
R2 = 0.9534
0
100
200
300
400
500
600
700
800
900
0 5 10 15 20
y = 21.425x + 362.41
R2 = 0.9483
0
100
200
300
400
500
600
700
800
900
0 5 10 15 20
Head diameter
Head diameter (cm)
Fig. 4.1. Relationship between number of achene per head and head diameter (cm) a) 2006, b) 2007
a
(b)
47
A
chen
e yi
eld(
kg h
a -1
)
y = 224.08x - 1279.9
R2 = 0.9223
0
500
1000
1500
2000
2500
3000
3500
0 5 10 15 20
y = 229.25x - 1385.3
R2 = 0.9232
500
1000
1500
2000
2500
3000
3500
5 10 15 20
Head diameter
Head diameter (cm)
Fig. 4.2. Relationship between achene yield and head diameter (cm) a) 2006, b) 2007
(a)
(b)
48
Table 4.5. Influence of sulphur and nitrogen nutrition on number of achenes
head-1 of sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 752 685 b 718
S2= 40 767 695 ab 731
S3= 80 772 701 ab 737
S4= 120 769 708 a 739
LSD at 5% NS 17.95
Nitrogen (kg ha-1)
N1= Control 640 c 590 c 615
N 2= 100 774 b 697 b 736
N 3= 140 818 a 748 a 783
N 4= 180 827 a 753 a 790
LSD at 5% 30.25 17.95
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
49
4.1.1.6. 1000 achene weight (g) Weight of individual achenes expresses the magnitude of achene development is
one of the most important determinants of seed yield and seed quality. Application of
sulphur significantly (P≤0.05) influenced 1000-achene weight of sunflower during both
the years (Table 4.6). Heaviest 1000-achenes (53.94 g) were produced with sulphur
application at 80 kg ha-1, which was 20.48% more than that (44.77 g) without sulphur
fertilization. Further enhancement in sulphur dose up to 120 kg ha-1 resulted in non-
significant (P≤0.05) increase in 1000-achene weight. On an average, 1000-achene weight
increased by 10, 21 and 16 percent over control with the application of 40, 80 and 120 kg
ha-1 S, respectively. Several authors (Singh et al., 2000; Poonia, 2000; Nasreen and Haq,
2002; Khan et al., 2003; Bhagat et al., 2005; Hassan et al., 2007) have reported
encouraging response of achene weight to sulphur application in sunflowers.
Nitrogen application also had a constructive behavior for 1000-achene weight
during both the years (Table 4.6). During 2006, maximum 1000-achene weight (55.89 g)
was recorded with application of 180 kg ha-1 nitrogen which was 48.52% higher than
control (no nitrogen). Nitrogen at 140 kg ha-1 exhibited similar achene weight as former
treatment. Similar trend was observed during 2007. On an average, application of 100,
140 and 180 kg ha-1 N increased 1000-achene weight by 29, 47 and 50 percent,
respectively over control. Several other authors (Ahmad et al., 2005; Ozer et al., 2004;
Poonia, 2000) observed a progressive and reliable raise in achene weight with addition in
N dose up to 160 kg ha-1.
Different combinations of sulphur and nitrogen exhibited significantly different
achene weight only during 2007 (Table 4.6) Maximum (60.53 g) 1000-achene weight was
recorded for 140 kg ha-1 nitrogen and 80 kg ha-1 sulphur. This treatment was statistically
at par with 1000-achene weights of 60.02 and 57.60 g recorded with application of
sulphur and nitrogen application at 80, 40 and 180 kg ha-1, respectively. The significant
interactive effect of sulphur and nitrogen nutrition on test weight of sunflower was also
reported by Sing (2000) and Sofi et al., (2004). 1000-achene weight was positively
associated with oil yield of sunflower (Fig. 4.4), and regression accounted for 93% (90-
96) of the variation in oil yield of sunflower owing to difference/s in achene weight
recorded under various treatments in these studies.
50
Table 4.6. Influence of sulphur and nitrogen nutrition on 1000-achene weight (g)
of sunflower.
Treatments 2006 2007 mean Sulphur (kg ha-1) S1= Control 44.77c 42.55 c 43.66 S2= 40 48.44 b 47.55 b 48 S3= 80 53.94 a 51.88 a 52.91 S4= 120 52.26 a 48.95 b 50.61
LSD at 5% 2.15 1.98
Nitrogen (kg ha-1) N1= Control 37.63 c 36.43 c 37.03
N 2= 100 49.54 b 46.15 b 47.85
N 3= 140 55.37 a 53.47 a 54.42
N 4= 180 55.89 a 54.88 a 55.39
LSD at 5% 2.15 1.98
Interaction (S x N) NS
S1N1 32.07 30.75 i 31.41
S1N2 43.40 42.40 g 42.90
S1N3 50.44 47.47 ef 48.96
S1N4 53.17 49.57 de 51.37
S2N1 37.97 37.23 h 37.60
S2N2 47.92 43.97 fg 45.95
S2N3 52.71 51.40 cde 52.06
S2N4 55.17 57.60 ab 56.39
S3N1 40.93 37.73 h 39.33
S3N2 54.02 49.23 de 51.63
S3N3 60.11 60.53 a 60.32
S3N4 60.71 60.02 a 60.36
S4N1 39.53 40.00 gh 39.77
S4N2 52.80 49.00 de 50.90
S4N3 58.22 54.47 bc 56.35
S4N4 58.51 52.33 cd 55.42
LSD at 5% NS 3.97 Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
51
4.1.1.7. Stover yield (kg ha-1) Increasing levels of sulphur application enhanced the stover yield (Table 4.7)
during both the years that could reach level of significance (P≤0.05) only during 2007.
Sulphur application at 40 kg ha-1 increased stover yield by only 3 % over control that was
13% with application of 80 kg ha-1 S. A further increase in S level did not enhance stover
yield significantly over the former treatment. Poonia et al. (2000) and Khan et al. (2002)
have also reported improvement in stover yield of sunflower with increase in sulphur
application rates.
Application of nitrogen significantly improved stover yield (Table 4.7) during
both the years of experimentation. Highest stover yield (7981-8358 kg ha-1) was recorded
with the application of 180 kg ha-1 N during both years. On an average, application of
100, 140 and 180 kg ha-1 enhanced stover yield by 47, 64 and 87 percent, respectively
over control. Different combinations of sulphur and nitrogen did not influence stover
yield significantly (P≤0.05) during both the years (Table 4.7) depicting an independent
response of both the nutrients in terms of vegetative growth.
4.1.1.8 Achene yield (kg ha-1)
Final achene yield is the function of combined effect of all the yield components
under the influence of particular set of environmental conditions. Application of sulphur
enhanced achene yield significantly (P≤0.05) during both years of experimentation (Table
4.8). During 2006, maximum achene yield (2620 kg ha-1) was recorded with application
of 80 kg ha-1 S and declined thereafter. Although the trend was same during 2007 but the
decline was non-significant (P≤0.05). On average, achene yield increases of 25, 39 and 32
percent were observed with application of 40, 80 and 120 kg ha-1 S, respectively over
control. Doubling sulphur application over 40 kg ha-1 enhanced achene yield by 12% but
declined by 5% when S level was doubled further. Lega and Giri (1999), Sarkar et al.
(1999) and Hitsuda et al. (2005) also reported positive impact of sulphur fertilization on
achene yield of sunflower.
Nitrogen application also enhanced achene yield significantly (P≤0.05) over
control and a yield plateau was achieved with application of 140 kg ha-1 during both the
years (Table 4.8). Application of 100 kg ha-1 enhanced achene yield by 88% over control
that was 126% when N application was increased by 40 kg ha-1. Achene yield was
increased by 134% over control with application of 180 kg ha-1 N (Table 4.8).
52
Table 4.7. Influence of sulphur and nitrogen nutrition on stover yield (kg ha-1) of
sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 6539 5876 b 6207
S2= 40 6665 6073 b 6369
S3= 80 7000 6631 a 6816
S4= 120 6789 6598 a 6694
LSD at 5% NS 408
Nitrogen (kg ha-1)
N1= Control 4585 d 4128 a 4357
N 2= 100 6651 c 6175 c 6413
N 3= 140 7400 b 6893 b 7147
N 4= 180 8358 a 7981 a 8170
LSD at 5% 388 408
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
53
Table 4.8. Influence of sulphur and nitrogen nutrition on achene yield (kg ha-1)
of sunflower.
Treatments 2006 2007 mean
Sulphur (kg ha-1)
S1= Control 1804 d 1833 c 1819
S2= 40 2322 c 2217 b 2270
S3= 80 2620 a 2425 a 2523
S4= 120 2474 b 2311 ab 2393
LSD at 5% 96.43 119.46
Nitrogen (kg ha-1)
N1= Control 1320 c 1087 c 1204
N 2= 100 2321 b 2202 b 2262
N 3= 140 2750 a 2696 a 2723
N 4= 180 2830 a 2800 a 2815
LSD at 5% 96.43 119.46
Interaction (S x N)
S1N1 838 i 767 j 803
S1N2 1683 j 1732 h 1708
S1N3 2133 f 2250 fg 2192
S1N4 2517 e 2583 de 2550
S2N1 1300 h 1133 i 1217
S2N2 2288 f 2117 g 2203
S2N3 2800 cd 2700 cde 2750
S2N4 2900 bc 2917 abc 2909
S3N1 1580 g 1250 i 1415
S3N2 2667 de 2483 ef 2575
S3N3 3167 a 3000 a 3084
S3N4 3069 ab 2967 ab 3018
S4N1 1517 g 1200 i 1359
S4N2 2647 de 2477 ef 2562
S4N3 2900 bc 2833 abc 2867
S4N4 2833 cd 2733 bcd 2783
LSD at 5% 192.87 239 Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
54
Zubillaga et al. (2002) recorded maximum achene yield with application of 150
kg ha-1 nitrogen while Arif et al. (2003) and Ozer et al. (2004) also recorded substantial
increase in achene yield with N application. Vegetative and generative growth of plant.
reduces during N deficiency and premature senescence also occurs, consequently
decreasing yield (Narwal and Malik, 1985; Khokani et al., 1993; Legha and Giri, 1999
and Tomar et al., 1999).
Increase in achene yield can be attributed to improvement in light interception
(Table 4.14 ) and improved leaf area indices (Table4.10) resulting in better crop growth
rates (Table 4.12 ) recorded with higher doses of nitrogen. Increase in nitrogen
availability resulted in higher achene yield was closely related to the improvement in
yield components such as head diameter (Tomer (1997), Sadiq et al (2000), number of
achenes/head (Zubillaga et al.2002) and 1000 seed weight (Hocking et al.(1987), Mahal
et al.(1998), Georgio et al(1990), and Killi (2004).
Interactive effect of different combinations of S and N was significant (P≤0.05) in
enhancing achene yield of sunflower (Table 4.8). During both the years, highest achene
yield (3084-3018 kg ha-1) was recorded with the application of S and N at 80 and 140 kg
ha-1. Similar (P≤0.05) achene yield levels were recorded with lower S application (40 kg
ha-1) but when N application rates was increased upto 180 kg ha-1 showing that S and N
levels interacted to increase the efficiency of these nutrients in terms of achene yield.
There was a positive and linear relationship between head diameter and achene
yield during 2006 and 2007 (Fig 4.2) and regression accounted for 92% of the variance in
yield. Achene yield was also positively related to the number of achenes per head (Fig
4.3) and 1000-achene weight (Fig 4.4) and regression accounted for 89.62 and 95.04%
variance in achene yield, respectively. Such close association between the yield
contributing parameters under discussion and achene yield was also reported by
Cantagallo et al. (1997), Mercau et al. (2001), Khaliq (2004) and Hussain (2008).
55
Ach
ene
yiel
d(kg
ha
-1)
y = 224.08x - 1279.9
R2 = 0.9223
0
500
1000
1500
2000
2500
3000
3500
0 5 10 15 20
y = 229.25x - 1385.3
R2 = 0.9232
500
1000
1500
2000
2500
3000
3500
5 10 15 20
Head diameter
Head diameter (cm)
Fig. 4.3. Relationship between achene yield and head diameter (cm) a) 2006, b) 2007
(b)
a
56
A
chen
e yi
eld
(Kg
ha-1
)
y = 8.3771x - 4101.3
R2 = 0.8542
100
600
1100
1600
2100
2600
3100
3600
300 400 500 600 700 800 900
y = 10.504x - 5126
R2 = 0.9381
500
1000
1500
2000
2500
3000
3500
500 550 600 650 700 750 800
Number of achene per head
Fig. 4.4. Relationship between achene yield and number of achene per head a)
2006, b) 2007
(a)
(b)
57
A
chen
e yi
eld
(Kg
ha-1
)
y = 79.826x - 1674.5
R2 = 0.9675
0
500
1000
1500
2000
2500
3000
3500
0 20 40 60 80
y = 83.907x - 1808.6
R2 = 0.933
50
550
1050
1550
2050
2550
3050
3550
20 30 40 50 60 70
1000-grain weight
Fig. 4.5. Relationship between achene yield and 1000-achene weight a) 2006, b) 2007
(a)
(b)
58
4.1.1.9. Harvest index (%)
Harvest index (HI) indicates the balanced distribution of assimilates into
economic yield. Sulphur nutrition had a significant (P≤0.05) and positive bearing on
harvest index (Table 4.9). Highest HIs (27.0-26.3) were recorded with application of 80
kg ha-1 S during 2006 and 2007, respectively and had a decreasing trend with increasing S
level further. On an average, sulphur dose of 40 and 80 kg ha-1 improved HI by 18 and 21
percent, respectively over control.
Nitrogen application also improved harvest index significantly (P≤0.05) over
control during both the years of experimentation (Table 4.9). Harvest index increased
initially with N application so that maximum values (27-28 %) were recorded with 140 kg
ha-1 N and declined by about 7 % with increasing N to 180 kg ha-1. On an average, N
application at 100 and 140 kg ha-1 improved HI by 21 and 28 percent. The decrease in
harvest index with the higher nitrogen application might be due to changing the stability
between vegetative and reproductive growth towards unnecessary vegetative growth, and
hence, in reduced achene yields (Fara et al., 1981; Hocking et al., 1987).
Data (Table 4.9) revealed that different combinations of S and N had an
interactive effect on harvest index during both years. Although highest HI values were
recorded with application of 80 and 140 kg ha-1 S and N, respectively but these were at
par (P≤0.05) with those recorded with increasing S level to 120 kg ha-1 with a
concomitant decrease in N to 100 kg ha-1. Similarly, increase/decrease in level of either S
or N compensated equilaterally to achieve similar level of harvest indices in these studies.
4.1. 2.Growth
4.1.2.1 Leaf area index
Sulphur application enhanced development of leaf area indices (LAI) during both
the years (Fig. 4.5). LAI did not vary significantly (P≤0.05) amongst different levels of S
at 30 days after sowing (DAS) that started getting significant with the advancement in
developmental stage and became prominent at 60 DAS. Highest LAIs (4.22-4.28) were
recorded with application of 80 and 120 kg ha-1 S during 2006. However, during 2007,
maximum LAI was recorded with application of 80 kg ha-1 S and declined thereafter with
higher level of S (Table 4.10). Application of 40, 80 and 120 kg ha-1 S improved LAI by
5 and 10 percent, respectively during both years of experimentation.
59
Table 4.9. Influence of sulphur and nitrogen nutrition on harvest index (%) of sunflower.
Treatments 2006 2007 mean
Sulphur (kg ha-1)
S1= Control 21.07 c 22.95 c 22.01 S2= 40 25.58 b 26.36 a 25.97 S3= 80 27.00 a 26.29 a 26.65
S4= 120 26.60 ab 25.45 b 26.03
LSD at 5% 1.13 0.75
Nitrogen (kg ha-1) N1= Control 22.18 c 20.79 c 21.49
N 2= 100 25.73 b 26.21 b 25.97
N 3= 140 27.02 a 28.08 a 27.55
N 4= 180 25.32 b 25.98 b 25.65
LSD at 5% 1.13 0.75
Interaction (S x N)
S1N1 17.28 h 18.09 h 17.69
S1N2 20.53 g 22.09 fg 21.31
S1N3 22.75 fg 25.87 e 24.31
S1N4 23.70 ef 25.75 e 24.73
S2N1 22.99 f 23.08 f 23.93
S2N2 25.89 cde 26.87 cde 26.38
S2N3 27.85 abc 29.07 ab 28.46
S2N4 25.59 de 26.42 de 26.01
S3N1 23.89 ef 21.37 g 22.63
S3N2 28.02 abc 27.93 bc 27.98
S3N3 29.48 a 29.71 a 29.60
S3N4 26.58 bcd 26.15 e 26.37
S4N1 24.55 def 20.62 g 22.59
S4N2 28.47 ab 27.95 bc 27.71
S4N3 27.98 abc 27.65 bcd 27.82
S4N4 25.40 de 25.59 e 25.50
LSD at 5% 2.26 1.50
Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
60
During 2007, maximum value for leaf area index (4.21) was recorded with 80 kg
ha-1 S application and was 16.62% higher over control. LAI declined after 75 DAS in
treatments during both the years.
Sing et al. (2000) reported that increasing sulphur levels from zero to 45 kg ha-1
enhanced the leaf area index significantly over control. Ahmad and Abdin (2000) also
supported the positive effect of sulphur on leaf area. The increase in LAI might be
credited to the contribution of sulphur in the synthesis of chlorophyll and being the
component of amino acids- cystin, cystein and methionine (Marschnar, 1995).
Nitrogen application recorded significantly (P≤0.05) different leaf area indices
throughout crop growth period during both the years (Fig. 4.6). In contrary to S,
significant differences amongst different N levels were depicted at earlier stage and were
also more pronounced than those recorded for S. Highest LAI values (4.96) were
recorded with application of 180 kg ha-1 N during both the years (Table 4.10). On an
average, 54, 77 and 89 percent higher LAIs were recorded with application of 100, 140
and 180 kg ha-1 N, respectively over control. The increase in LAI was sharper from 0 to
100 kg ha-1 N and became less steeper for next level (140 kg ha-1) and ultimately achieved
a plateau for 180 kg ha-1 N. LAI declined steadily after 75 DAS during both the years
achieving almost similar (P≤0.05) values at 90 DAS for all N-applied plots. However,
LAI in control plots declined only to slight extent (Fig.4.6 ). Different combinations of S
and N did not reflect significant differences for LAI during both the years of
experimentation (Table 4.10).
The correlation analysis showed a strong and positive association of the leaf area
index with number of achenes per head (Fig 4.7), 1000-achene weight (Fig 4.8), crop
growth rate (Fig 4.9) and achene yield (Fig 4.10). The common regression accounted for
95.73% (96.32-95.13%) variation in number of achenes per head and 89.43% (92.73-
86.13%) variance in 1000-achene weight. While regression accounted for 98.33% (98.95-
97.84%) variation in crop growth rate and 92.37% (90.01-94.74%) for variance in achene
yield owing to differences in LAI.
61
Lea
f ar
ea in
dex
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
30 45 60 75 90
S1 S2 S3 S4
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
30 45 60 75 90
S1 S2 S3 S4
Days after sowing
Fig. 4.6. Pattern of leaf area index with time as influenced by sulphur nutrition during (a) 2006 and (b) 2007 ±SD
S1= Control, S2= 40 kg ha-1, S3= 80 kg ha-1, S4= 120 kg ha-1
(a) 2006
(b) 2007
62
Lea
f ar
ea in
dex
0.0
1.0
2.0
3.0
4.0
5.0
6.0
30 45 60 75 90
N1 N2 N3 N4
0.0
1.0
2.0
3.0
4.0
5.0
6.0
30 45 60 75 90
N1 N2 N3 N4
Days after sowing
Fig. 4.7: Pattern of leaf area index with time as influenced by nitrogen
nutrition during (a) 2006 and (b) 2007 ±SD N1= Control, N2= 100 kg ha-1, N3= 140 kg ha-1, N4= 180 kg ha-1
(a) 2006
(b) 2007
63
Table 4.10. Influence of sulphur and nitrogen nutrition on leaf area index (75
DAS) of sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 4.03 b 3.61 d 3.82
S2= 40 4.09 b 3.95 c 4.02
S3= 80 4.22 a 4.21 a 4.22
S4= 120 4.28 a 4.10 b 4.19
LSD at 5% 0.11 0.10
Nitrogen (kg ha-1)
N1= Control 2.87 d 2.36 d 2.62
N 2= 100 4.13 c 3.94 c 4.04
N 3= 140 4.67 b 4.60 b 4.64
N 4= 180 4.96 a 4.96 a 4.96
LSD at 5% 0.11 0.10
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
64
N
umbe
r of
ach
ene
per
head
y = 141.39x + 379.74
R2 = 0.9632
400
450500
550600
650
700750
800850
900
0.00 1.00 2.00 3.00 4.00
y = 114.66x + 409.33
R2 = 0.9513
400
450
500
550
600
650
700
750
800
850
0 1 2 3 4
Leaf area index
Fig. 4.8. Relationship between number of achene per head and leaf area
index a) 2006, b) 2007
(a)
(b)
b
65
1000
-gra
in w
eigh
t (g)
y = 15.494x + 7.661
R2 = 0.9273
0
10
20
30
40
50
60
70
0 1 2 3 4
y = 13.62x + 13.543
R2 = 0.8613
0
10
20
30
40
50
60
70
0 1 2 3 4
Leaf area index
Fig. 4.9. Relationship between 1000-grain weight and leaf area index a) 2006, b) 2007
(a)
(b)
66
Cro
p gr
owth
rat
e (g
m-2
d-1
)
y = 7.258x - 7.3411
R2 = 0.9895
0
2
4
6
8
10
12
14
16
18
0 1 2 3 4
y = 6.3594x - 4.1038
R2 = 0.9784
0
24
6
810
12
1416
18
0 1 2 3 4
Leaf area index
Fig. 4.10 Relationship between crop growth rate and leaf area index a) 2006, b) 2007
(a)
(b)
67
A
chen
e yi
eld
(kg
ha-1
)
y = 1238.8x - 1068.4
R2 = 0.9001
0
500
1000
1500
2000
2500
3000
3500
0 1 2 3 4
y = 1240.9x - 918.47
R2 = 0.9474
0
500
1000
1500
2000
2500
3000
3500
0 1 2 3 4
Leaf area index
Fig. 4.11 Relationship between achene yield (kg ha-1) and leaf area index a) 2006, b) 2007
(a)
(b)
68
4.1.2.2 Leaf area duration
Sulphur nutrition enhanced leaf area duration (LAD) over control and the pattern
was same during both years of experimentation (Table 4.11). During 2006 highest and
similar LAD were recorded with application of 80 and 120 kg ha-1 S while during 2007
significantly lower LAD was recorded with later dose of S. On an average, S application
at 40, 80 and 120 kg ha-1 enhanced LAD by 7, 12 and 10 percent, respectively over
control. Comparatively lesser LAD was recorded during 2007 and might be attributed to
higher rains (Fig. 3.1) and hence higher soil moisture available for better leaf area
development (Fig. 4.5) throughout the season.
Nitrogen application significantly (P≤0.05) increased the leaf area duration over
control plots and maximum LAD (210.65-193.10 d) was recorded with 180 kg ha-1
nitrogen during both years. Similar patterns of LAD increase were recorded for different
N levels. On an average, application of 100, 140 and 180 kg ha-1 N gave an LAD
advantage of 48, 47 and 75 percent, respectively over control. Khaliq (2004) and Iqbal
(2008) also concluded that nitrogen application improved leaf area duration of sunflower.
Different combinations of S and N had a non significant impact on LAD in present
studies during both the years (Table 4.11).
4.1.2.3 Crop growth rate
Periodic data at fortnight interval (Fig. 4.11 & 4.12) revealed that crop growth rate
(CGR) of sunflower crop progressively increased and achieved maximum value (21.21 g
m-2 d-1) at 75 DAS and declined sharply thereafter; reaching a value of 6.63 g m-2 d-1 at 90
DAS during 2006. Similar trend was observed during 2007 for this hybrid. Pattern of crop
growth rate as influenced by sulphur and nitrogen nutrition has been illustrated in figures
4.11 and 4.12 respectively. Sulphur application improved seasonal crop growth over
control during both years of experimentation (Table 4.12) however, the differences
amongst different S levels remained non-significant (P≤0.05). On an average, sulphur
application at 40, 80 and 120 kg ha-1 improved seasonal crop growth rate by 9, 13 and 12
percent over control. Crop growth rates were in the range of 11.21 to 12.70 g m-2 d-1.
Mean seasonal crop growth was significantly influenced by nitrogen application
rates during both years (Table 4.12). Mean crop growth rate improved with each
incremental level of N. During both the years nitrogen applied at 180 kg ha-1 recorded
highest CGR (16.11-15.54 g m-2 day-1) that was , on average, 7.40% more than that
(15.00 g m-2 day-1) recorded with the application of 140 kg ha-1 nitrogen.
69
Table 4.11. Influence of sulphur and nitrogen nutrition on leaf area duration
(days) of sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 168.38 c 147.64 c 158.01
S2= 40 176.00 b 162.27 b 169.14
S3= 80 183.11 a 171.15 a 177.13
S4= 120 182.23 a 164.04 b 173.14
LSD at 5% 5.43 6.89
Nitrogen (kg ha-1)
N1= Control 123.62 d 107.50 d 115.56
N 2= 100 175.78 c 166.40 c 171.09
N 3= 140 199.67 b 178.11 b 188.89
N 4= 180 210.65 a 193.10 a 201.88
LSD at 5% 5.43 6.89
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
70
Cro
p gr
owth
rat
e (g
m-1
d-1
)
0
5
10
15
20
25
45 60 75 90
S1 S2 S3 S4
0
5
10
15
20
25
45 60 75 90
S1 S2 S3 S4
Days after sowing
Fig. 4.11: Pattern of crop growth rate with time as influenced by sulphur nutrition during (a) 2006 and (b) 2007 ±SD S1= Control, S2= 40 kg ha-1, S3= 80 kg ha-1, S4= 120 kg ha-1
(a) 2006
(b) 2007
71
Cro
p gr
owth
rat
e (g
m-1
d-1
)
0
5
10
15
20
25
30
45 60 75 90
N1 N2 N3 N4
0
5
10
15
20
25
30
45 60 75 90
N1 N2 N3 N4
Days after sowing Fig. 4.12: Pattern of crop growth rate with time as influenced by nitrogen nutrition during (a) 2006 and (b) 2007 ±SD N1= Control, N2= 100 kg ha-1, N3= 140 kg ha-1, N4= 180 kg ha-1
(a) 2006
(b) 2007
72
Table 4.12. Influence of sulphur and nitrogen nutrition on seasonal crop growth
rate (g m-2 d-1) of sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 11.70 b 10.72 b 11.21
S2= 40 12.42 ab 11.91 a 12.17
S3= 80 13.00 a 12.40 a 12.70
S4= 120 12.58 a 12.41 a 12.50
LSD at 5% 0.88 0.78
Nitrogen (kg ha-1)
N1= Control 6.37 d 6.28 d 6.33
N 2= 100 12.21 c 11.51 c 11.86
N 3= 140 15.00 b 14.12 b 14.56
N 4= 180 16.11 a 15.54 a 15.83
LSD at 5% 0.88 0.78
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
73
Sunflower crop grown without nitrogen fertilization exhibited lowest mean CGR
(6.37 g m-2 day-1) that was 135.47% and 91.67% lower, when crop was sown with 140
and 100 kg ha-1 nitrogen rate respectively. Approving results were recorded by Khaliq
(2004) who concluded that nitrogen rate of 200 kg ha-1 presented highest mean crop
growth rate in sunflower crop.
Non significant differences were recorded regarding interactive effect of sulphur
and nitrogen on mean CGR of sunflower crop during both years. Different combinations
of these nutrients gave mean CGR in the range between 5.92 and 15.58 g m-2 day-1.
There was a positive and linear relationship between crop growth rate and achene
yield (Fig 4.13) during both the years of study and regression accounted for 91% (86.64-
94.70%) variation in achene yield.
4.1.2.4 Net assimilation rate
. Sulphur application exhibited a non-significant (P≤0.05) effect on net
assimilation rate of sunflower during both years of experimentation (Table 4.13).
Nitrogen application significantly increased NAR over control during both the years so
that highest and similar NAR values (5.07-5.01 g m-2 d-1) were recorded for 180 and 140
kg ha-1 N over control. On an average, N rates of 100, 140 and 180 kg ha-1 improved
NAR by 19, 32 and 33 percent, respectively over control. Shabeer (2009) reported similar
range of NAR (4.75-4.5 g m-2 d-1) for sunflowers grown under similar environments
Different combinations of S and N also depicted non-significant differences for
NAR in these studies (Table 4.13).
4.1.2.5 Cumulative light interception
Sulphur application enhanced amount of intercepted radiation significantly
(P≤0.05) during both years of study (Table 4.14). During both the years, highest and
similar cumulative intercepted radiation was observed with the application of 80 and 120
kg ha-1 S which was about 5% higher over control. Application of 40 kg ha-1 S enhanced
cumulative radiation interception only by 3% over control. The enhancement in
cumulative light interception was expected because of improvement in LAI (Table 4.10)
with increasing sulphur application rates which concomitantly is associated with increase
in intercepted photosynthetically active radiation (Olsen et al., 2000). ). Higher
interception of radiation was recorded during 2006 that might be attributed to better
climatic conditions conducive for development of higher intercepting surfaces of crop
canopy (Fig. 4.5).
74
A
chen
e yi
eld(
kg
ha-1
)
y = 166.58x + 235.65
R2 = 0.8664
0
500
1000
1500
2000
2500
3000
3500
0 5 10 15 20
y = 192.96x - 91.932
R2 = 0.947
0
500
1000
1500
2000
2500
3000
3500
0 5 10 15 20
Crop growth rate
crop growth rate (g m-2 d-1) Fig. 4.13. Relationship between achene yield and crop growth rate (g m-2 d-1) a)
2006, b) 2007
(a)
(b)
75
Table 4.13. Influence of sulphur and nitrogen nutrition on net assimilation rate (g m-
2 d-1) of sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 4.66 4.74 4.68
S2= 40 4.52 4.76 4.64
S3= 80 4.55 4.63 4.59
S4= 120 4.1 4.85 4.48
LSD at 5% NS NS
Nitrogen (kg ha-1)
N1= Control 3.58 c 4.06 c 3.82
N 2= 100 4.56 b 4.56 b 4.56
N 3= 140 4.86 a 5.16 a 5.01
N 4= 180 4.93 a 5.20 a 5.07
LSD at 5% 0.28 0.30
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
76
Nitrogen application resulted in better cumulative radiation interception during
both the years in these studies (Table 4.14). Maximum light interception (536.14-503.22
MJ m-2) was recorded with 180 kg ha-1 nitrogen application during both years which was
24 and 20 percent higher than respective control values during 2006 and 2007.Nitrogen
application at 100 and 140 kg ha-1 recorded radiation interception of 489.58 and 510.76
MJ m-2, respectively which was 14.98 and 19.96 percent more than control. Higher mean
values during 2006 were recorded owing to higher extent of leaf expansion.
Cumulative PAR interception during whole growing season by maize, sunflower and
soybean recorded was 820, 700 and 720 M. J m-2 (Andrade, 1995). Improvement in
radiation interception as a consequence of nitrogen fertilization has been reported in many
of previous studies. Hall et al. (1995) reported that total cumulated intercepted radiation
by sunflower crop increased by 6% (from 928 to 971 MJ m-2), with increasing nitrogen
from zero to 50 kg ha-1. Positive impact of nitrogen application on radiation interception
has been reported by Khaliq (2004) under similar environments. Fernando and Miralles
(2008) reported 20 and 7% increase in intercepted photosynthetic active radiation in
wheat crop with nitrogen and sulphur addition, respectively.
Different combinations of S and N recorded significantly (P≤0.05) different
radiation interception values only during 2007 (Table 4.14). A critical perusal of data
revealed that application of higher N rates (180 kg ha-1) without sulphur application
recorded as high levels of radiation interception as was recorded with application of 140
kg ha-1 N in combination with 40, 80 and/or 120 kg ha-1 S. It may not be impertinent to
mention that N had a predominating role in canopy development that is crucial in
radiation interception. So where the critical threshold levels of LAIs were achieved with
ample N in the absence of S, the later did not contribute much towards radiation
interception.
There was a optimistic and linear association between cumulative intercepted
PAR and LAI (Fig 4.14) and regression accounted for 96.36% (96.76-95.97 %) of
variance in PAR owing to differences in LAI. There also existed a similar relationship
between cumulative radiation interception and achene yield (Fig 4.15) and regression
accounted for 93.56% (91.79-95.34 %) variance in achene yield.
77
Table 4.14. Influence of sulphur and nitrogen nutrition on cumulative radiation
interception (M.J.m-2) of sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 480.84 c 460.94 c 370.89
S2= 40 499.10 b 473.28 b 486.19
S3= 80 507.64 a 478.96 ab 493.30
S4= 120 508.48 a 482.32 a 495.40
LSD at 5% 8.42 7.31
Nitrogen (kg ha-1)
N1= Control 431.96 d 419.58 d 425.77
N 2= 100 501.92 c 477.25 c 489.58
N 3= 140 526.04 b 495.47 b 510.76
N 4= 180 536.14 a 503.22 a 519.68
LSD at 5% 8.42 7.31
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
78
C
umul
ativ
e in
terc
epte
d ra
diat
ion
(MJ
m-2
)
y = 79.836x + 281.61
R2 = 0.9676
300
350
400
450
500
550
600
1.0 1.5 2.0 2.5 3.0 3.5
y = 59.33x + 324.95
R2 = 0.9597
200
250
300
350
400
450
500
550
0 1 2 3 4
Leaf area index
Fig. 4.14. Relationship between cumulative intercepted radiation (MJ
m-2)and leaf area index a) 2006, b) 2007
(a)
(b)
79
A
chen
e yi
eld
Kg
ha-1
)
y = 15.414x - 5386.7
R2 = 0.9179
100
600
1100
1600
2100
2600
3100
3600
300 350 400 450 500 550 600
y = 3.2843x - 1131.1
R2 = 0.9534
100
150
200
250
300
350
400
450
500
550
600
300 350 400 450 500 550
Cumulated intercepted radiation
Cumulative intercepted radiation (MJ m-2)
Fig. 4.15. Relationship between achene yield (kg ha-1) and cumulative intercepted radiation (MJ m-2) a) 2006, b) 2007
(a)
(b)
80
.4.1.2.6 Radiation use efficiency (TDM)
Translation of intercepted photosynthetically active radiation into new biomass is
termed as radiation use efficiency (Sinnclair and Muchow, 1999) and help measure net
carbon assimilation of a crop. Sulphur application exhibited significant (P≤0.05)
influence on RUE(TDM) only during 2007 (Table 4.15). Application of sulphur enhanced
RUE(TDM) by 8-10 percent over control, while the differences amongst different sulphur
levels were non-significant. On an average, RUE(TDM) was 1.653 g MJ-1. Fernando and
Miralles (2008) recorded increase in RUE of wheat crop with increasing rates of sulphur
nutrition that might be attributed to increase in photosynthesis with increased sulphur
application (Terry, 1976).
Nitrogen application had a significant (P≤0.05) influence on RUE(TDM) during both
years (Table4.15 ). Application of increasing levels of nitrogen improved RUE(TDM) upto
140 kg ha-1 N during 2006 with a non significant increase with 180 kg ha-1 N. However,
during 2007, RUE(TDM) increased steadily with each incremental level of N so that highest
(1.995 g MJ-1) was recorded with the application of 180 kg ha-1 N. On an average,
application of 100, 140 and 180 kg ha-1 N improved the RUE(TDM) by 55, 79 and 91
percent, respectively over control (Table 4.15).
Hall et al. (1995) also concluded that nitrogen supply influenced RUE of
sunflower and it increased from 1.01 g MJ-1 to 1.18 g MJ-1 with the increase in nitrogen
rate from zero to 50 kg ha-1. The values of RUE for sunflower in the study under
discussion are in confirmatory to those reported by Kiniry et al. (1989), Khaliq (2004)
and Iqbal (2008). The values of RUE for sunflower as reported by Connor et al. (1985),
Cox and Jolliff (1986) and Champan et al. (1993) for above ground dry matter were 1.75,
2.79, and 1.05 g MJ-1, respectively. Sinclair and Horie, (1989)reported that nitrogen
increased Rubisco activity in leaves and resulted an improvement in radiation use
efficiency (RUE),which is reliant on net CO2 assimilation(Loomis and Amthor, 1999).
Different combinations of N and S did not influence RUE (TDM) in these studies.
(Table 4.15)
81
Table 4.15. Influence of sulphur and nitrogen nutrition on radiation use efficiency TDM (g M.J -1) of sunflower
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 1.567 1.509 b 1.538
S2= 40 1.601 1.632 a 1.617
S3= 80 1.640 1.667 a 1.654
S4= 120 1.593 1.661 a 1.627
LSD at 5% NS 0.108
Nitrogen (kg ha-1)
N1= Control 1.023 1.035 d 1.029
N 2= 100 1.594 1.588 c 1.591
N 3= 140 1.844 1.850 b 1.847
N 4= 180 1.939 1.995 a 1.967
LSD at 5% 0.108 0.108
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5% probability level; NS = Non-significant
82
4.1.2.7 Radiation use efficiency (grain)
Sulphur application influenced RUE grain significantly (P≤0.05) during both
years of experimentation (Table 4.16). During 2006, maximum radiation use efficiency
for grain (0.51 g MJ-1) was recorded when sunflower crop was fertilized with 80 kg ha-1
sulphur. It was 11.35% higher than that recorded for 40 kg ha-1 sulphur, and was 39%
higher over control. Similar trend was observed during 2007. On an average, application
of 40, 80 and 120 kg ha-1 S improved RUE for grain by 22, 34 and 26 percent,
respectively over control.
Radiation use efficiency for grain under study was markedly influenced with
different nitrogen levels during both years (Table 4.16). Increasing levels of N enhanced
RUE for grain that did not increase significantly (P≤0.05) beyond 140 kg ha-1 N during
both years of experimentation. Application of N @ 100, 140 and 180 kg ha-1, improved
RUEgrain by 64, 86 and 92 percent, respectively over control (Table 4.16). Almost similar
values of radiation use efficiency for grain (achene) were reported earlier by Iqbal (2008)
under similar environmental conditions.
Non-significant (P≤0.05) interaction between sulphur and nitrogen nutrition for
RUEgrain was recorded during both years of experimentation in present studies (Table
4.16).
4.1.3 Quality parameters
4.1.3.1 Achene protein contents (%)
Data (Table 4.17) revealed that sulphur application improved achene-protein
content during both the years. During 2006, maximum and similar (P≤0.05) achene-
protein (21.66-21.21 %) was recorded with the application of 80 and 120 kg ha-1 sulphur,
while a minimum (16.09%) was observed in control plots. Similar trend was observed
during 2007. Increase in achene-protein contents with sulphur application is in
confirmatory to previous reports of Bhagat et al. (2005) and Sreenamannarayana et al.
(1998) who concluded that sulphur nutrition had a positive bearing on achene-protein
content. Poonia (2003) also recorded an increase in protein contents of sunflower in
response to sulphur application.
Application of nitrogen significantly (P≤0.05) enhanced achene-protein content
during both the years (Table 4.17). The maximum protein concentration (22.87-23.07-%)
was recorded with application of 180 kg ha-1 during 2006 and 2007. Achene-protein
improved with application of all N levels over control in these studies. When averaged
83
Table 4.16. Influence of sulphur and nitrogen nutrition on radiation use efficiency
grain (g M.J -1) of sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 0.366 c 0.388 c 0.377
S2= 40 0.458 b 0.461 b 0.460
S3= 80 0.510 a 0.498 a 0.504
S4= 120 0.480 a 0.473 ab 0.423
LSD at 5% 0.026 0.026
Nitrogen (kg ha-1)
N1= Control 0.306 a 0.258 0.282
N 2= 100 0.462 b 0.462 0.462
N 3= 140 0.522 a 0.525 0.524
N 4= 180 0.525 a 0.558 0.542
LSD at 5% 0.026 0.026
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
84
Table 4.17. Influence of sulphur and nitrogen nutrition on achene protein
contents (%) of sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 16.22 c 16.09 d 16.16
S2= 40 19.03 b 19.35 c 19.19
S3= 80 21.44 a 21.66 a 21.55
S4= 120 21.20 a 21.21 b 21.21
LSD at 5% 0.30 0.24
Nitrogen (kg ha-1)
N1= Control 14.41 d 14.27 d 14.34
N 2= 100 18.72 c 18.84 c 18.78
N 3= 140 21.88 b 22.12 b 22.00
N 4= 180 22.87 a 23.07 a 22.97
LSD at 5% 0.30 0.24
Interaction (S x N)
S1N1 11.60 j 11.12 l 11.36
S1N2 15.55 h 15.41 j 15.48
S1N3 18.25 g 18.35 h 18.30
S1N4 19.46 f 19.46 g 19.46
S2N1 14.02 l 14.23 k 14.35
S2N2 18.50 g 18.67 h 18.59
S2N3 21.12 d 21.72 e 21.42
S2N4 22.50 c 22.79 d 22.65
S3N1 16.11 h 16.11 i 16.11
S3N2 20.65 de 20.86 f 20.76
S3N3 24.23 ab 24.40 bc 24.32
S3N4 24.75 a 25.25 a 25.00
S4N1 15.90 h 15.63 j 15.77
S4N2 20.18 e 20.42 f 20.30
S4N3 23.93 b 24.03 c 23.98
S4N4 24.77 a 24.77 b 24.77
LSD at 5% 0.59 0.47 Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
85
across years, N rates of 100, 140 and 180 kg ha-1 improved achene-protein percentage by
31, 53 and 60 percent, respectively over control. Previous findings of Malhi and Leach
(2000), Khaliq (2004), Kuchar (2005) and Ahmad (2007) also supported the results under
discussion.
Different combinations of S and N had a significant (P≤0.05) influence on achene-
protein content and the trend was same during both the years (Table 4.17). Application of
80 kg ha-1 S with 140 and/or 180 kg ha-1 N recorded as good achene-protein content as
was recorded with application of 120 kg ha-1 S in combination with 180 kg ha-1 N (Table
4.17). Lower achene-protein content was recorded with highest levels of either of the
nutrients under study in present investigations, revealing that there was a strong
interactive effect of both S and N in improving achene-protein content in sunflowers.
4.1.3.2. Achene oil content (%)
Quality of sunflower seed is determined from its oil content. Data (Table 4.18)
indicated a significantly (P≤0.05) positive influence of sulphur application so that highest
achene-oil content (44.17-44.04 percent) was recorded during two years of study with the
application of 120 kg ha-1 S. Sunflower grown without S application exhibited 38.38%
achene-oil content, while application of 40, 80 and 120 kg ha-1 S improved achene-oil
content by 6, 13 and 15 percent, respectively over control.
The higher oil contents recorded with increasing sulphur levels is in line with the
results obtained by Ahmad et al.(1999). Poonia (2003) reported significant influence of
sulphur application on sunflower oil contents. The increasing trend of oil concentration
with sulphur application in present studies is in line with the findings of (Hassan et al.
(2007) who concluded that different levels of sulphur (0, 10, 15, 20 kg ha-1) improved the
oil contents of the autumn planted sunflower from 38.1 to 45.1 %. Baghat et al. (2005)
recorded highest oil contents (41.72%) with 40 kg ha-1 sulphur.
Nitrogen application had a negative (P≤0.05) bearing on oil contents (Table 4.18) so that
lowest achene-oil content (39.82-39.77 percent) was noted with application of 180 kg ha-1
N during both years of experimentation. Sunflower crop grown without nitrogen
application exhibited highest achene-oil content (43.81 and 43.56 percent) during 2006
and 2007, respectively. On an average application of 100, 140 and 180 kg ha-1 N recorded
2.8, 7.3 and 9.9 percent reduction in achene-oil content, respectively over control. Several
authors (Schneiter et al., 2002; Ali et al., 2004; Ozer et al., 2004; Al-Thabet, 2006) have
reported negative influence of N on seed oil concentration. Concentration of protein in the
86
kernels as recorded by Ivanov and Stoyanova (1978) ranged from 17 to 36%, while
Khaliq (2004) recorded comparatively lower achene protein concentration that ranged
from 12 to 16% under similar environments. The significant negative relationship
between seed oil content and high nitrogen fertilization could be probably attributed to
the sugar translocation effecting oil synthesis (Salisbury & Ross, 1994). Kutcher et al.
(2005) attributed such negative relationship to the diluting effect of higher seed yield at
higher N application and the opposite relationship between protein and oil content.
Different combinations of S and N exhibited non-significant (P≤0.05) influence
on achene-oil content of sunflowers grown during both the years (Table 4.18).
4.1.3.3 Oil yield (kg ha-1)
The ultimate objective in oilseed crop production is the oil yield, which is a
product of achene yield and achene oil contents in case of sunflower. Data (Table 4.19)
indicated that oil yield of sunflower increased with S fertilization and maximum (1139-
1041 kg ha-1) was recorded with the application of S @ 80 Kg ha-1 during 2006 and
2007, respectively. A further increase in S level did not bring a significant (P≤0.05)
increase in oil yield. On an average, S application at 40, 80 and 100 kg ha-1 resulted in 33,
58 and 52 percent increase in oil yield, respectively over control. The effect of sulphur
application on the oil yield which is a product of oil contents and achene yield was also
studied by Poonia (2003) and Bhaghat (2005) and they recorded positive and significant
effect.
Nitrogen application also exhibited significant (P≤0.05) improvement in oil yield
of sunflower during both years of experimentation (Table 4.19). Highest oil yield (1136
kg ha-1) was recorded with application of 140 kg ha-1 N during 2006 that reached to
highest value (1115 kg ha-1) with further increased level (180 kg ha-1) of N during 2007.
Two years average data indicated the oil yield increased by 83, 110 and 111 percent with
N dose of 100, 140 and 180 kg ha-1 N, respectively over no nitrogen treatment...
Different combinations of S and N exhibited a non significant (P≤0.05) difference
in oil yield during both the years (Table 4.19).
There was positive relationship between achene yield and oil yield (Fig 4.16) and
regression accounted for 96 % variance in oil yield of sunflower.
87
Table 4.18. Influence of sulphur and nitrogen nutrition on achene oil contents (%)
of sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 38.58 c 38.18 d 38.38
S2= 40 40.95 b 40.64 c 40.80
S3= 80 43.70 a 43.23 b 43.47
S4= 120 44.17 a 44.01 a 44.09
LSD at 5% 1.35 0.73
Nitrogen (kg ha-1)
N1= Control 43.81 a 43.56 a 43.70
N 2= 100 42.79 a 42.25 b 42.52
N 3= 140 40.97 b 40.49 c 40.73
N 4= 180 39.82 b 39.72 d 39.77
LSD at 5% 1.35 0.73
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
88
Table 4.19. Influence of sulphur and nitrogen nutrition on achene oil yield (kg ha-1)
of sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 686.90 c 689.20 c 688.05
S2= 40 940.20 b 888.90 b 914.55
S3= 80 1139.20 a 1040.86 a 1090.03
S4= 120 1083.86 a 1008.00 a 1045.93
LSD at 5% 62.93 70.19
Nitrogen (kg ha-1)
N1= Control 584.40 c 477.70 c 531.05
N 2= 100 1001.70 b 936.70 b 969.20
N 3= 140 1135.81 a 1097.90 a 1116.86
N 4= 180 1128.29 a 1114.60 a 1121.45
LSD at 5% 62.93 70.19
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
89
O
il y
ield
(kg
ha-1
)
y = 0.4122x + 12.291
R2 = 0.9529
0
200
400
600
800
1000
1200
1400
1600
0 1000 2000 3000 4000
y = 0.4008x + 26.519
R2 = 0.9601
0
200
400
600
800
1000
1200
1400
0 500 1000 1500 2000 2500 3000 3500
Achene yield
Achene yield (kg ha-1) Fig. 4.16 Relationship between oil yield (kg ha-1) and achene yield (kg ha-
1)a) 2006, b) 2007
(a)
(b)
90
4.1.3.4 Fatty acid profile
Relative proportion of different fatty acids in edible oil, determines the superiority
of that oil and the oil that possesses higher percentage of poly-unsaturated fatty acids for
lowering cholesterol level in human body is considered of good quality (Cunnae ;1995).
Utilization of oils having larger proportion of un-saturated fatty acids has been found to
have constructive consequences on human health (Jing et al., 1997; Hu et al., 2001).
Some of the important fatty acids present in sunflower achene oil are discussed in this
portion.
4.1.3.4.1 Oleic acid concentration (%)
Concentration of oleic acid (18:1) in achene oil of sunflower varied significantly
(P≤0.05) under different sulphur levels (Table 4.20). During first year, maximum oleic
acid concentration (12.14%) was recorded when crop was grown without sulphur
application and it decreased progressively with increasing levels of sulphur so that
minimum oleic acid concentration (10%) was exhibited with the application of sulphur
@120 kg ha-1.Similar trend was recorded during 2007 but oleic acid concentration did not
vary amongst different S levels to significant (P≤0.05) extent. Manaf and Hassan (2006)
and Ahmad and Abidin (2000) recorded inconsistent response of oleic acid to sulphur
levels. These results are contradictory to the findings of Misra et al. (2002).
Application of nitrogen had a significantly (P≤0.05) negative influence on oleic
acid (18:1) (mono-unsaturated fatty acid) concentration (Table 4.20) during both the years
of experimentation. During 2006, sunflower grown without nitrogen application exhibited
maximum (17.25%) oleic acid concentration in achene oil and minimum (7.35%) was
recorded for 180 kg ha-1 nitrogen fertilization. Increasing nitrogen levels from 100 to 140
kg ha-1 resulted in significant (P≤0.05) decrease (28.38%) in concentration of oleic acid in
achene oil. It was further decreased by 12.65% with the highest level (180 kg ha-1) of
nitrogen application. Almost similar trend was recorded for 2007.
Khaliq (2004) and Iqbal (2008) also reported negative impact of nitrogen on oleic
acid contents of sunflower under similar environmental conditions. These results are also
in line with finding of Ahmad and Abdin (2000).
Interactive effects of nitrogen and sulphur application on the oleic acid concentration
were found to be non significant (P≤0.05) during both the years of study.
91
Table 4.20. Influence of sulphur and nitrogen nutrition on oleic acid
concentration (%) of sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 12.14 a 11.80 a 11.97
S2= 40 11.00 b 10.50 b 10.75
S3= 80 10.38 bc 10.13 b 10.26
S4= 120 10.00 c 10.00 b 10
LSD at 5% 0.67 0.69
Nitrogen (kg ha-1)
N1= Control 17.25 a 16.17 a 16.71
N 2= 100 10.63 b 10.54 b 10.59
N 3= 140 8.28 c 8.24 c 8.26
N 4= 180 7.35 d 7.48 d 7.42
LSD at 5% 0.67 0.69
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
92
4.1.3.4. 2. Linoleic acid concentration (%)
Sulphur application had a significant (P≤0.05) bearing on linoleic acid (18:2)
concentration in sunflower achene oil only during 2006 (Table 4.21). However, the
differences amongst sulphur levels were non-significant. On an average, sulphur
application at 40, 80 and 120 kg ha-1 improved linoleic content by 2.3, 3 and 3.5 percent,
respectively over control. This increasing trend in linoleic acid concentration with sulphur
application is in line with the findings of Misra et al. (2002), while Ahmad and Abidin
(2002) reported contradictory results in brassica species. During both the years, linoleic
acid concentration varied significantly (P≤0.05) under different levels of nitrogen
application as compared with control (Table 4.21). It increased gradually with increasing
levels of nitrogen so that application of 140 and 180 kg ha-1 N recorded highest and
similar (P≤0.05) values of 80.5 and 81.4 percent during both years. The minimum
(72.01%) linoleic acid concentration was realized without nitrogen application, while
application of 100, 140 and 180 kg ha-1 N improved it by 7, 12 and 13 percent,
respectively over the former treatment (control). These results are in line with those
reported by Steer and Sailor (1990), Khaliq (2004).
Different combinations of S and N recorded a significant (P≤0.05) influence on
linoleic acid concentration in achene-oil of sunflower only during 2006 (Table 4.21).
Highest concentrations of this fatty acid were recorded where either both S or N or any
one of these was used at its higher application rate. For example, combination
of S and N at 0+180, 40+140, 40+180 kg ha-1 recorded as high concentration as was
realized with combined application of 120+80, 120+180, 80+180, 80+140 kg ha-1 of S
and N, respectively (Table 4.21). This implied that the maximum concentration of linoleic
acid was developed in achene-oil when either of these nutrients touched its so called
saturation level, and that it was not dependent on any specific one used in present studies.
4.1.3.4.3. Palmitic Acid concentration (%)
Data (Table 4.22) revealed that sulphur application did not influence the palmitic
acid (16:1) concentration to significant extent (P≤0.05) during both the years. Palmitic
acid concentration was in the range of 4.96 to 5.20%.
Palmitic acid concentration increased significantly (P≤0.05) with the application of
nitrogen over control during both years (Table 4.22). During 2006, maximum
concentration (6.19%) was recorded by the application of 180 kg ha-1 nitrogen. It was
followed by 5.94% and 5.72% with 140 and 100 kg ha-1 N and the difference between
93
these being non-significant (P≤0.05). Average of two year data revealed that palmitic acid
concentration improved by 11, 15 and 20 percent with application of 100, 140 and 180 kg
ha-1 N, respectively over control. The increase in palmitic acid concentration with
increasing nitrogen levels confirms the findings of Steer and Seiler (1990) and Khaliq
(2004).
A non-significant (P≤0.05) difference among combinations of various sulphur and
nitrogen levels was recorded for both years of experimentation (Table 4.22)
4.1.3.4.4. Stearic acid (%)
Stearic acid is categorized as saturated fatty acid, and is an undesirable oil quality
characteristic. The perusal of the analyzed data (Table 4.23) revealed that neither sulphur,
nor nitrogen nutrition influenced the concentration of stearic acid during 2006 & 2007 to
significant (P≤0.05) level over control. Non-significant effect of nitrogen application on
stearic acid concentration of sunflower was also recorded by Iqbal (2008) under similar
climatic conditions. Valtcho et al. (2009) reported a decrease in stearic acid concentration
in sunflower when it was fertilized with 0 and 64 kg ha-1 N as compared to 134 and 202
kg ha-1 N application. Valchovski (2002) also reported similar results for N application.
Different combinations of S and N also had a non-significant (P≤0.05) influence
on stearic acid concentration in sunflower achene-oil (Table 4.23).
94
Table 4.21. Influence of sulphur and nitrogen nutrition on linoleic acid
concentration (%) of sunflower achene oil.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 76.17 b 76.58 76.38
S2= 40 78.06 a 78.21 78.14
S3= 80 78.55 a 78.92 78.74
S4= 120 79.14 a 79.06 79.10
LSD at 5% 1.70 NS
Nitrogen (kg ha-1)
N1= Control 72.07 c 71.81 c 71.94
N 2= 100 78.40 b 78.58 b 78.49
N 3= 140 80.39 a 80.63 ab 80.51
N 4= 180 81.05 a 81.75 a 81.40
LSD at 5% 1.70 2.19
Interaction (S x N) NS
S1N1 72.32 g 70.07 71.32
S1N2 76.18 f 75.71 75.95
S1N3 79.17 cd 78.73 78.95
S1N4 80.42 abc 80.15 80.28
S2N1 76.35 ef 71.00 73.68
S2N2 79.30 bcd 78.90 79.10
S2N3 80.43 abc 80.67 80.55
S2N4 81.11 a 81.67 81.39
S3N1 77.99 de 72.33 75.16
S3N2 80.05 abc 79.00 79.53
S3N3 80.85 abc 81.21 81.03
S3N4 81.03 a 81.67 81.35
S4N1 76.24 f 74.89 75.57
S4N2 79.69 abc 80.00 79.85
S4N3 80.97 ab 80.93 80.95
S4N4 81.00 ab 80.73 80.87
LSD at 5% 1.72 NS Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
95
Table 4.22. Influence of sulphur and nitrogen nutrition on palmatic acid
concentration (%) of sunflower achene oil.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 5.77 4.60 5.19
S2= 40 5.76 4.63 5.20
S3= 80 5.76 4.61 4.96
S4= 120 5.78 4.62 5.20
LSD at 5% NS NS
Nitrogen (kg ha-1)
N1= Control 5.22 c 4.07 4.65
N 2= 100 5.75 b 4.59 5.17
N 3= 140 5.94 b 4.79 5.37
N 4= 180 6.19 a 5.01 5.60
LSD at 5% 0.24 NS
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
.
96
Table 4.23. Influence of sulphur and nitrogen nutrition on stearic acid concentration
(%) of sunflower achene oil.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 4.81 3.81 4.31
S2= 40 4.83 3.84 4.34
S3= 80 4.85 3.86 4.36
S4= 120 4.86 3.87 4.37
LSD at 5% NS NS
Nitrogen (kg ha-1)
N1= Control 4.83 3.84 4.34
N 2= 100 4.83 3.85 4.34
N 3= 140 4.84 3.85 4.35
N 4= 180 4.85 3.83 4.34
LSD at 5% NS NS
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
97
4.1.4 Nutrient uptake
Information on nutrient uptake of the crop is crucial in determining the fertilizer
use efficiency, and also helpful in devising fertilizer management strategies for achieving
yield targets in a crop. Following section discusses the nutrient uptake by sunflower
grown on various S and N nutrition.
4.1.4.1 Nitrogen uptake (kg ha-1)
Sulphur application increased nitrogen uptake significantly (P≤0.05) during both
the years (Table 4.24). During 2006, maximum and similar (P≤0.05) nitrogen uptake
(105.9 and 102.7 kg ha-1) was recorded with 120 and 80 kg ha-1 sulphur fertilization,
respectively. Application of sulphur at 40 kg ha-1 recorded 92.6 kg ha-1 N uptake by the
crop. Similar pattern for N uptake was observed during 2007, but was in lesser quantity
than the previous year that might be attributed to due to more rain, and higher soil
moisture regimes during periods of active growth in that year (Fig. 3.1). Application of N
uptake was improved by 13 % when S rate was increased from 40 to 80 kg ha-1, and
increased slightly (by only 2%) when S application was further increased to 120 kg ha-1.
Data (Table 4.24) revealed that nitrogen application significantly (P≤0.05)
enhanced N uptake by the crop. During 2006, highest N uptake (140 kg ha-1) was
recorded with application of 180 kg ha-1 N. It was 12% higher than that recorded for 140
kg ha-1 N application and 59% higher than that recorded for plots fertilized at 100 kg ha-1
N. Almost similar trend for N uptake in response to nitrogen application was recorded
during 2007. Crop grown without N fertilization recorded only 27 kg ha-1 N.
The significant difference for removal of nutrients by sunflower is dependent on
yield produced by the crop and positive regression accounted for (90-94%) for the years
2006 and 2007 (Fig 4.17) Angelova and Christov (2003) observed that variation in achene
yield from 500 to 3500 kg ha-1 resulted in an increase in N uptake from 8.8 to 197.4 kg
ha-1. Almost same trend of yield and nutrient uptake was recorded in present studies.
Different combinations of S and N fertilizer exhibited a significant (P≤0.05) influence on
N uptake by the crop during both years of experimentation (Table 4.24). A careful perusal
of data indicated that application of higher levels (140, 180 kg ha-1) of nitrogen resulted in
increased N uptake in combination with either lower (40 kg ha-1) or higher (120 kg ha-1)
levels of sulphur application.
98
Table 4.24. Influence of sulphur and nitrogen nutrition on total nitrogen uptake
(kg ha-1) of sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1)
S1= Control 78.07 c 71.43 c 74.75
S2= 40 92.63 b 88.25 b 90.44
S3= 80 102.69 a 101.83 a 102.26
S4= 120 105.87 a 101.96 a 103.85
LSD at 5% 6.90 6.83
Nitrogen (kg ha-1)
N1= Control 26.93 d 26.39 d 26.66
N 2= 100 87.98 c 83.44 c 85.71
N 3= 140 124.33 b 117.94 b 121.14
N 4= 180 140.02 a 135.69 a 137.86
LSD at 5% 6.90 6.83
Interaction (S x N)
S1N1 21.40 f 21.56 g 21.48
S1N2 72.23 e 64.13 f 68.18
S1N3 98.14 d 89.82 e 93.98
S1N4 120.50 c 110.21 c 115.36
S2N1 26.20 f 27.94 g 27.07
S2N2 86.56 d 83.58 e 85.07
S2N3 117.60 c 107.60 cd 112.6
S2N4 140.15 b 133.89 b 137.02
S3N1 29.94 f 27.52 g 28.73
S3N2 98.53 d 94.18 de 96.36
S3N3 140.25 b 133.07 be 136.66
S3N4 154.74 a 152.53 a 153.64
S4N1 30.18 f 28.56 g 29.37
S4N2 94.58 d 91.87 e 93.23
S4N3 141.31 ab 141.26 ab 141.29
S4N4 144.69 ab 146.14 ab 145.42
LSD at 5% 13.81 13.66
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
99
A
chen
e yi
eld
(Kg
ha-1
)
y = 14.37x + 942.76
R2 = 0.9049
0
500
1000
1500
2000
2500
3000
3500
0 50 100 150 200
y = 15.818x + 759.09
R2 = 0.9377
0
500
1000
1500
2000
2500
3000
3500
0 50 100 150 200
Nitrogen uptake
Nitrogen uptake (Kg ha-1 Fig. 4.17. Relationship between achene yield (Kg ha-1)and nitrogen uptake a)
2006, b) 2007
(a)
(b)
100
Application of only 40 kg ha-1 S exhibited a fairly good N uptake only when accompanied
by a higher level (180 kg ha-1) of nitrogen. On the other hand, crop grown without S
fertilization in combination with 140 kg ha-1 N also failed to achieve fairly good N uptake
levels suggesting a synergistic effect of both nutrients in enhancing N uptake in
sunflowers.
Fig (4.17) revealed that there was a positive correlation between achene yield and
nitrogen uptake by sunflower crop during both the years and regression accounted for
(90-94 %) variance in achene yield.
4.1.4.2 Phosphorus uptake (kg ha-1)
Sulphur application had a pronounced (P≤0.05) effect on total P uptake by
sunflower crop during both years of experimentation (Table 4.25). Increasing levels of S
up to 80 kg ha-1 resulted in corresponding increase in P uptake that did not increase
further with next level of S in these studies. Similar trend was observed for both the years
for P uptake, so that application of 40, 80 and 120 kg ha-1 S improved total P uptake by
13, 23 and 20 percent, respectively over control.
Agarwal et al. (2000) recorded an increase in phosphorus uptake with sulphur
application at the rate of 40 kg ha-1. Nasreen and Haq (2002) reported synergistic effect of
sulphur on P uptake and recorded an increase in P uptake upto 35 kg ha-1 with increasing
level of sulphur application upto 80 kg ha-1 in sunflower crop. Sing and Chaudhuri (1996)
recorded similar results in groundnut. Singh and Singh(2007) also recorded positive
response of P uptake by linseed with increasing sulphur application rate.
Increasing levels of nitrogen fertilization significantly (P≤0.05) enhanced total P
uptake in sunflower during both years of experimentation (Table 4.25). During 2006,
highest phosphorus uptake (50.40 kg ha-1) was recorded in the plots where nitrogen was
applied at 180 kg ha-1, and it was 197.97% higher than that recorded for control plots
(16.78 kg ha-1 P). Increasing nitrogen application from 100 to 140 kg ha-1 improved
nitrogen uptake from 34.64 to 45.42 kg ha-1 which was 10.96% lower than that obtained
with the highest dose of nitrogen in present studies. Almost similar trend was observed
during 2007.
Different combinations of S and N exhibited a non-significant (P≤0.05) influence
on total P uptake in sunflower during both years of experimentation (Table 4. 25).
Regarding relationship between phosphorus uptake and achene yield (Fig.4.18),
there was a optimistic correlation and regression accounted for (87-93%) for two years of
study.
101
Table 4.23. Influence of sulphur and nitrogen nutrition on total phosphorus uptake
(kg ha-1) of sunflower.
Treatments 2006 2007 Mean
Sulphur (kg ha-1) 33.21 c 30.51 c 31.86
S1= Control 36.60 b 35.07 b 35.84
S2= 40 39.93 a 38.31 a 39.12
S3= 80 39.49 ab 37.10 ab 38.30
S4= 120 6.83 2.60
LSD at 5%
Nitrogen (kg ha-1) 16.78 d 16.48 d 16.63
N1= Control 34.64 c 32.78 c 33.71
N 2= 100 45.42 b 42.97 b 44.20
N 3= 140 50.40 a 48.76 a 49.58
N 4= 180 6.83 2.60
LSD at 5% 6.83 2.60
Interaction (S x N) NS NS
Means having different letters within a column differ significantly from each other at 5%
Sulphur nutrition enhanced leaf area duration (LAD) over control and the pattern
was same during both years of experimentation (Table 4.11). Comparatively lesser LAD
was recorded during 2007 and might be attributed to higher rains (Fig. 3.1) and hence
higher soil moisture available for better leaf area development (Fig. 4.5) throughout the
season. Nitrogen application significantly (P≤0.05) increased the leaf area duration over
control plots and maximum LAD (210.65-193.10 d) was recorded with 180 kg ha-1
nitrogen during both years. Khaliq (2004) and Iqbal (2008) also concluded that nitrogen
application improved leaf area duration of sunflower. Different combinations of S and N
had a non significant impact on LAD in present studies during both the years (Table
4.11). Periodic data at fortnight interval (Fig. 4.11 & 4.12) revealed that crop growth rate
(CGR) of sunflower crop progressively increased and achieved maximum value (21.21 g
m-2 d-1) at 75 DAS and declined sharply thereafter; reaching a value of 6.63 g m-2 d-1 at 90
DAS during 2006. Similar trend was observed during 2007 for this hybrid. Pattern of crop
growth rate as influenced by sulphur and nitrogen nutrition has been illustrated in figures
4.11 and 4.12 respectively. Sulphur application improved seasonal crop growth over
114
control during both years of experimentation (Table 4.12). Mean crop growth rate
improved with each incremental level of N. Sunflower crop grown without nitrogen
fertilization exhibited lowest mean CGR (6.37 g m-2 day-1) that was 135.47% and 91.67%
lower, when crop was sown with 140 and 100 kg ha-1 nitrogen rate respectively.
Approving results were recorded by Khaliq (2004) who concluded that nitrogen rate of
200 kg ha-1 presented highest mean crop growth rate in sunflower crop. There was a
positive and linear relationship between crop growth rate and achene yield (Fig 4.13)
during both the years of study and regression accounted for 91% (86.64-94.70%)
variation in achene yield.
Sulphur application exhibited a non-significant (P≤0.05) effect on net assimilation
rate of sunflower during both years of experimentation (Table 4.13). Nitrogen application
significantly increased NAR over control during both the years so that highest and similar
NAR values (5.07-5.01 g m-2 d-1) were recorded for 180 and 140 kg ha-1 N over control.
On an average, N rates of 100, 140 and 180 kg ha-1 improved NAR by 19, 32 and 33
percent, respectively over control. Shabeer (2009) reported similar range of NAR (4.75-
4.5 g m-2 d-1) for sunflowers grown under similar environments.
The total amount of incident photosynthetically active radiation received during
2006 and 2007 was 695 and 681 MJ m-2, respectively. Sulphur application enhanced
amount of intercepted radiation significantly (P≤0.05) during both years of study (Table
4.14). The enhancement in cumulative light interception was expected because of
improvement in LAI (Table 4.10) with increasing sulphur application rates which
concomitantly is associated with increase in intercepted photosynthetically active
radiation (Olsen et al., 2000). Maximum light interception (536.14-503.22 MJ m-2) was
recorded with 180 kg ha-1 nitrogen application during both years which was 24 and 20
percent higher than respective control values during 2006 and 2007. Cumulative PAR
interception during whole growing season by maize, sunflower and soybean recorded was
820, 700 and 720 M. J m-2 (Andrade, 1995). Improvement in radiation interception as a
consequence of nitrogen fertilization has been reported in many of previous studies. Hall
et al. (1995) reported that total cumulated intercepted radiation by sunflower crop
increased by 6% (from 928 to 971 MJ m-2), with increasing nitrogen from zero to 50 kg
ha-1. Positive impact of nitrogen application on radiation interception has been reported
by Khaliq (2004) under similar environments. Fernando and Miralles (2008) reported 20
and 7% increase in intercepted photosynthetic active radiation in wheat crop with
nitrogen and sulphur addition, respectively.
115
Hocking and Steer (1989) stated that N deficiency during early growth stages of
sunflower may reduce the leaf score and restricts their expansion, consequently reduction
in LAI and light interception may occur. An environmental stress has more pronounced
effect on foliar expansion than photosynthetic capacity of the crop (Fitter and Hay, 2002),
therefore, the crop grown under nitrogen and sulphur deficiency is expected to experience
decrease in LAI and intercepted photosynthetically active radiation. Kiniry et al. (2004)
also concluded that nitrogen deficiency reduced LAI of sunflower crop which is typically
associated with concomitant decrease in intercepted photosynthetically active radiation.
There was a optimistic and linear association between cumulative intercepted PAR and
LAI (Fig 4.14).
Translation of intercepted photosynthetically active radiation into new biomass is
termed as radiation use efficiency (Sinnclair and Muchow, 1999) and help measure net
carbon assimilation of a crop. Application of sulphur enhanced RUE(TDM) by 8-10 percent
over control, while the differences amongst different sulphur levels were non-significant.
Fernando and Miralles (2008) recorded increase in RUE of wheat crop with increasing
rates of sulphur nutrition that might be attributed to increase in photosynthesis with
increased sulphur application (Terry, 1976). Application of increasing levels of nitrogen
improved RUE(TDM) upto 140 kg ha-1 N during 2006 with a non significant increase with
180 kg ha-1 N (Table4.15 ). Hall et al. (1995) concluded that nitrogen supply influenced
RUE of sunflower and it increased from 1.01 g MJ-1 to 1.18 g MJ-1 with the increase in
nitrogen rate from zero to 50 kg ha-1. The values of RUE for sunflower in the study under
discussion are in confirmatory to those reported by Kiniry et al. (1989), Khaliq (2004)
and Iqbal (2008). The values of RUE for sunflower as reported by Connor et al. (1985),
Cox and Jolliff (1986) and Champan et al. (1993) for above ground dry matter were 1.75,
2.79, and 1.05 g MJ-1, respectively. Sinclair and Horie, (1989) reported that nitrogen
increased Rubisco activity in leaves and resulted an improvement in radiation use
efficiency (RUE), which is reliant on net CO2 assimilation (Loomis and Amthor, 1999).
Variation in leaf photosynthetic capability coupled by means of the translocation of N
from green leaves to grain (Sinclair and Horie, 1989), and rise in crop respiratory mass
for each constituent of leaf area (Whitfield et al., 1989) might be conscientious for
difference in RUE under varying nitrogen application rates. Different combinations of N
and S did not influence RUE (TDM) in these studies (Table 4.15).
Maximum and similar (P≤0.05) achene-protein (21.66-21.21 %) was recorded with the
application of 80 and 120 kg ha-1 sulphur, while a minimum (16.09%) was observed in
116
control plots (Table 4.17). Increase in achene-protein contents with sulphur application is
in confirmatory to previous reports of Bhagat et al. (2005) and Sreenamannarayana et al.
(1998) who concluded that sulphur nutrition had a positive bearing on achene-protein
content. Poonia (2003) also recorded an increase in protein contents of sunflower in
response to sulphur application. Sulphur being an integral part of S-containing amino
acids, viz. cystein, cystine and methionine, also improved protein as well as oil synthesis
in (Tisdale et al., 1985) enhanced protein as well as oil synthesis in seeds. Sexton et al.
(1998) also supported the significant influence of sulphur on seed protein contents by
stating that protein quality of soybean seed could be enhanced by increasing the
concentration of S- containing amino acids. Maximum protein concentration (22.87-
23.07-%) was recorded with application of 180 kg ha-1 during 2006 and 2007. Achene-
protein improved with application of all N levels over control in these studies. Findings of
Malhi and Leach (2000), Khaliq (2004), Kuchar (2005) and Ahmad (2007) also supported
the results under discussion. Abundant supply of nitrogen enhances protein precursors
that are rich in N and there is strong tendency of photosynthates to be utilized for protein
formation and lesser of these are available for fat synthesis (Holmes, 1980). The inter-
relationships of the regulation of NO3- and SO4
2- assimilation might be an effective reason
to enhance net protein synthesis (Reuveny et al., 1980). The metabolic coupling between
N and sulphur has been reported by other authors(Blagrove et al., 1976; Randall et al.,
1979; Sexton et al., 1998),who found that relative sulphur-rich seed protein decreased in
crop raised with ample N but limited sulphur supply, and vice versa. Sofi et al. (2004)
reported similar findings while Ahmad et al. (2007) reported non-significant interactive
effect of sulphur and nitrogen on protein contents of canola. Fazli et al. (2008) concluded
that combined application of S and N enhanced the uptake and assimilation of nitrate,
thereby increased total nitrogen contents and finally resulted in an improvement in protein
contents.
Highest achene-oil content (44.17-44.04 percent) was recorded during two years
of study with the application of 120 kg ha-1 S (Table 4.18). Sunflower grown without S
application exhibited 38.38% achene-oil content, while application of 40, 80 and 120 kg
ha-1 S improved achene-oil content by 6, 13 and 15 percent, respectively over control.
The higher oil contents recorded with increasing sulphur levels is in line with the results
obtained by Ahmad et al.(1999). Poonia (2003) reported significant influence of sulphur
application on sunflower oil contents. Hassan et al. (2007) concluded that different levels
of sulphur (0, 10, 15, 20 kg ha-1) improved oil contents of the autumn planted sunflower
117
from 38.1 to 45.1 %. Baghat et al. (2005) recorded highest oil contents (41.72%) with 40
kg ha-1 sulphur. Lowest achene-oil content (39.82-39.77 percent) was noted with
application of 180 kg ha-1 N. Relationship between the level of N application and seed oil
content has usually been shown to be inversely correlated (Xie and Zhou, 2003). Several
authors (Schneiter et al., 2002; Ali et al., 2004; Ozer et al., 2004; Al-Thabet, 2006) have
reported negative influence of nitrogen on seed oil concentration. Concentration of
protein in the kernels as recorded by Ivanov and Stoyanova (1978) ranged from 17 to
36%, while Khaliq (2004) recorded comparatively lower achene protein concentration
that ranged from 12 to 16% under similar environments. The significant negative
relationship between seed oil content and high nitrogen fertilization could be probably
attributed to the sugar translocation effecting oil synthesis (Salisbury & Ross, 1994).
Kutcher et al. (2005) attributed such negative relationship to the diluting effect of higher
seed yield at higher N application and the opposite relationship between protein and oil
content.
Oil yield of sunflower increased with S fertilization and maximum (1139-1041 kg
ha-1) was recorded with the application of S @ 80 Kg ha-1 during 2006 and 2007,
respectively (Table 4.19). The effect of sulphur application on the oil yield which is a
product of oil contents and achene yield was also studied by Poonia (2003) and Bhaghat
(2005) and they recorded positive and significant effect. Highest oil yield (1136 kg ha-1)
was recorded with application of 140 kg ha-1 N during 2006 that reached to highest value
(1115 kg ha-1) with further increased level (180 kg ha-1) of N during 2007.
Relative proportion of different fatty acids in edible oil, determines the superiority
of that oil and the oil that possesses higher percentage of poly-unsaturated fatty acids for
lowering cholesterol level in human body is considered of good quality (Cunnae ;1995).
Utilization of oils having larger proportion of un-saturated fatty acids has been found to
have constructive consequences on human health (Jing et al., 1997; Hu et al., 2001).
Some of the important fatty acids present in sunflower achene oil are discussed in this
portion. Concentration of oleic acid (18:1) in achene oil of sunflower varied significantly
(P≤0.05) under different sulphur levels (Table 4.20). Manaf and Hassan (2006) and
Ahmad and Abidin (2000) recorded inconsistent response of oleic acid to sulphur levels.
These results are contradictory to the findings of Misra et al. (2002). Application of
nitrogen had a significantly (P≤0.05) negative influence on oleic acid (18:1) (mono-
unsaturated fatty acid) concentration (Table 4.20). Khaliq (2004) and Iqbal (2008) also
reported negative impact of nitrogen on oleic acid contents of sunflower under similar
118
environmental conditions. These results are also in line with finding of Ahmad and Abdin
(2000). Application of sulphur and nitrogen increased the percentage of poly unsaturated
fatty acid (linoleic) and decreased mono unsaturated fatty acid (oleic) and hence
improved the quality of sunflower oil. Such inverse relationship between
monounsaturated (oleic acid) and polyunsaturated (linoleic acid) in sunflower has been
reported by Flageella et al. (2002).and Roberson (1981). While, Manaf and -Hasan (2006)
listed inconsistent differences for oleic acid and linoleic acid in Brassica. Moreover, there
is a strong negative association between oleic and linoleic acid so that a phenotype low in
oleic would definitely be high in linoleic one (Demurin et al., 2000). Sulphur application
had a significant (P≤0.05) bearing on linoleic acid (18:2) concentration in sunflower
achene oil only during 2006 (Table 4.21). However, the differences amongst sulphur
levels were non-significant. Increasing trend in linoleic acid concentration with sulphur
application in present studies is in line with the findings of Misra et al. (2002), while
Ahmad and Abidin (2002) reported contradictory results.
Data (Table 4.22) revealed that sulphur application did not influence the palmitic
acid (16:1) concentration to significant extent (P≤0.05) during both the years. Palmitic
acid concentration was in the range of 4.96 to 5.20%. Palmitic acid concentration
increased significantly (P≤0.05) with the application of nitrogen. The increase in palmitic
acid concentration with increasing nitrogen levels confirms the findings of Steer and
Seiler (1990) and Khaliq (2004). Momoh et al. (2004) also support the positive influence
of nitrogen application on palmitic acid concentration. However, Valtcho et al. (2009)
recorded that nitrogen rates within different planting dates of same hybrids had little or no
effect on palmitic acid concentration.
Sulphur application increased nitrogen uptake significantly (P≤0.05) during both
the years (Table 4.24). Application of N uptake was improved by 13 % when S rate was
increased from 40 to 80 kg ha-1, and increased slightly (by only 2%) when S application
was further increased to 120 kg ha-1. Bhaghat et al. (2005) observed an increase in
nitrogen uptake with sulphur application in sunflower crop that might be attributed to
synergistic effect of sulphur and nitrogen. Khandkar (1991), Sreemannarayana et al.
(1989) and Mrinalini et al. (1998) reported similar results that confirm the findings of
present work. Nitrogen application significantly (P≤0.05) enhanced N uptake by the crop.
Jackson (2000) reported that nitrogen application increased N contents in sunflower plant
and seed. Zubillaga et al. (2002) recorded an increase in N uptake up to 138 kg ha-1 with
increasing nitrogen fertilization up to 138 kg ha-1. Singh et al. (2005) reported a
119
significant increase in total biomass and total nitrogen uptake by sunflower with
increasing nitrogen rate up to 90 kg ha-1. Combined effect of sulphur and nitrogen in
increasing total nitrogen uptake was also reported by Nabi et al.(1995) and Fazli et al.
(2008) who attributed this increase to the increase in nitrate reductase activity, that
regulate NO3-N into the amino acids. The increase in total nitrogen (kg ha-1) by rapeseed
and mustard with the combined effect of nitrogen and sulphur has also been reported by
other workers (Brown et al., 2000; Ahmad et al., 2001; Abdin et al., 2001). Fig (4.17)
revealed that there was a positive correlation between achene yield and nitrogen uptake
by sunflower crop during both the years and regression accounted for (90-94 %) variance
in achene yield.
Sulphur application had a pronounced (P≤0.05) effect on total P uptake by
sunflower crop during both years of experimentation (Table 4.25). Increasing levels of S
up to 80 kg ha-1 resulted in corresponding increase in P uptake that did not increase
further with next level of S in these studies. Agarwal et al. (2000) recorded an increase in
phosphorus uptake with sulphur application at the rate of 40 kg ha-1. Nasreen and Haq
(2002) reported synergistic effect of sulphur on P uptake and recorded an increase in P
uptake upto 35 kg ha-1 with increasing level of sulphur application upto 80 kg ha-1 in
sunflower crop. Sing and Chaudhuri (1996) recorded similar results in groundnut. Singh
and Singh (2007) also recorded positive response of P uptake by linseed with increasing
sulphur application rate. Increasing levels of nitrogen fertilization significantly (P≤0.05)
enhanced total P uptake in sunflower (Table 4.25). Sreemannarayana et al. (1998)
recorded an increase in phosphorus uptake by sunflower with an increase in nitrogen
application (from zero to 100 kg ha-1). The significant increase in P2O5 uptake (2.4 to 78
kg ha-1) with enhancement in achene yield from 500 to 3500 kg ha-1 in sunflower crop
was reported by (Angelova and Christov, 2003).
Sulphur fertilization showed significant (P≤0.05) influence on total K uptake by
the crop during both the years (Table 4.26). Application of 120 kg ha-1 S resulted in
highest total K uptake 135-129 kg ha-1) during two years of study. However, a lower dose
of S (80 kg ha-1) exhibited similar (P≤0.05) level of total K uptake. Sreemannarayana et
al. (1998) recorded an increase in potash uptake by sunflower with an increase in sulphur
application (from zero to 60 kg ha-1). Increase in potash uptake by sunflowers with
increasing sulphur application levels was also recorded by Nasreen and Haq (2002), while
Singh and Chaudhary (1996) reported similar results for groundnuts. Nitrogen application
120
resulted in significant (P≤0.05) increase in total K uptake by sunflower during both the
years.
Application of sulphur enhanced S-uptake significantly (P≤0.05) over control
(Table 4.27) and the differences were also significant amongst the S levels used. Bhagat
et al. (2005) also recorded significant increase in total sulphur uptake by the sunflower
crop with increase in sulphur application. Screemannarayana et al. (1998) and Mrinalini
et al. (1998) confirmed the positive response of sulphur uptake with application of
sulphur nutrition. S-uptake was also improved significantly (P≤0.05) with nitrogen
nutrition (Table 4.27).
121
4.2: Experiment II: Radiation interception, radiation use efficiency and productivity of different genotypes of sunflower under varying row spacing/planting densities
4.2.1. Agronomic Traits
4.2.1.1. Number of plants m-2
A good crop stand per unit area established by optimum plant population leads to
higher crop yield of sunflower. As regards hybrids of different maturity groups under
study, there was a non-significant (P≤0.05) difference among the hybrids (Table 4.28)
during both the years. This might be attributed to uniform germination and seedling
establishment of the three hybrids as well as absence of lodging in any of the hybrids used
in these studies. Saleem (2004) and Iqbal (2008) also recorded non-significant differences
in final number of plants per unit area for various sunflower hybrids.
Plant population at harvest varied significantly (P≤0.05) with change in row
spacing (Table4.28) during both years of study. At a constant plant to plant distance of
22.5 cm used in these experiments, widening the row spacing from 45 to 60 cm resulted
in 33% decrease in plan density that declined further by 24% when the crop was sown at
75 cm row spacing (Table 4.28). The change in number of plants m-2 was also recorded
by Iqbal (2008) with variation in row to row distance.
The interaction among hybrids and row spacing was found to be non-significant
during both the years depicting that plant density varied owing to row spacing
irrespective of hybrids used.
4.2.1.2 Number of days taken to maturity (d)
As regards hybrids of different maturity groups under study, there was a
significant (P≤0.05) difference among the hybrids (Table 4.29). During both the years,
Hysun-33 took 102 days to reach its maturity and statistically was different with rest of
the hybrids (SF-187 and FH-331) which were statistically at par with each other (Table
4.29). Steer and Hocking (1987) reported that there were small differences in time taken
from sowing to maturity among short stature (early maturity) and taller (late maturity)
hybrids. Johnson and Schneiter (1998) reported hybrids representing the greatest
available diversity for maturity and plant height The differential response of sunflower
hybrids regarding time taken to maturity may attributed to variable genetic character for
the respective hybrids to this trait. Iqbal (2008) also recorded significant difference
among the hybrids for time taken to maturity.
122
Table 4.28 Influence of different row spacing on number of plants m-2 of diverse
sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 7.58 7.57 7.58
H2= SF-187 7.54 7.59 7.57
H3= Hysun-33 7.59 7.58 7.59
LSD at 5% NS NS
Row spacing (S)
S1= 45 cm 9.63 a 9.63 a 9.63
S 2= 60 cm 7.26 b 7.24 b 7.25
S 3= 75 cm 5.84 c 5.86 c 5.85
LSD at 5% 0.03 0.06
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
123
Table 4.29. Influence of different row spacing on number of days taken to
maturity (days) of diverse sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 91.67b 91.00b 92
H2= SF-187 95.44b 94.89b 94
H3= Hysun-33 102.10 a 101.19 a 102
LSD at 5% 4.19 4.71
Row spacing (S)
S1= 45 cm 96.78 96.78 96
S 2= 60 cm 95.67 94.56 95
S 3= 75 cm 96.6 95.67 96
LSD at 5% N.S N.S
Interaction (H x S) N.S N.S
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
124
Sunflower crop sown at varying row spacing did not effect the time taken to
maturity and results depicted in Table 4.29 showed non- significant (P≤0.05) difference
for the time taken to maturity among different planting densities.
4.2.1.3 Plant height
Plant height is a function of both genetic constitution of a plant and the
environmental conditions under which it is grown. Differences in plant height among
different hybrids were significant (P≤0.05) during both the years. During both the years,
tallest plants (176 and 180 cm) were produced by Hysun-33 and plant height of this
hybrid was 28% higher than that of SF-187 and FH-331. SF-187 (141 cm) and FH-331
(140 cm) were statistically at par with each other (Table 4.30). The differential response
of sunflower hybrids regarding plant height may attributed to variable genetic potential
for the respective hybrids to this trait.Johnson and Schneiter (1998) reported hybrids
representing the greatest available diversity for maturity and plant height.
Varying row spacing (plant population) had a significant (P≤0.05) effect on plant
height during both years of experimentation (Table 4.30) and tallest plants (157.67 cm)
were produced when crop was sown in 45 cm apart rows (98765 plants ha-1) and shortest
plants (149.44 cm) were recorded in 75 cm row spacing (59259 plants ha-1), the later was
statistically at par with the plants grown at 60 cm apart.
Higher plant populations produced taller plants and more yield than lesser plant density
(Beg et al., 2007).These results are in agreement with the findings of Sedghi et al. (2008)
and Iqbal (2008), and opposite to those of Van Deynze et al. (1992).
4.2.1.4. Stem diameter
Different hybrids showed significant (P≤0.05) differences in stem diameters during 2006
only (Table4.31). SF-187 and Hysun-33 produced the thickest and similar stems as
compared with FH-331 (1.67 cm). In the year 2007, non significant results were found
regarding stem diameter that ranged from 1.71 to 1.77 cm. The significant differences for
stem diameter between the hybrids have also been reported by Ozer (2004), while the
non-significant differences regarding stem girth among the hybrids were reported by
Tunio et al. (1999.
Widening the row spacing increased the stem diameter significantly during both
the years of investigation (Table 4.31). On an average, minimum (1.67 cm) stem diameter
was recorded when the crop was sown at 45 cm apart row spacing that improved by 5%
and 11% when the crop was sown at 60 and 75 cm apart rows, respectively.
125
Table 4.30. Influence of different row spacing on plant height (cm) of diverse
sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 139.60 b 141.11 b 140.36
H2= SF-187 140.70 b 137.67 b 139.19
H3= Hysun-33 180 a 176.33 a 178.17
LSD at 5% 3.43 6.69
Row spacing (S)
S1= 45 cm 157.70 a 156.67 a 157.19
S 2= 60 cm 153.10 ab 151.22 ab 152.16
S 3= 75 cm 149.40 b 147.22 b 148.31
LSD at 5% 5.36 5.46
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
126
Table 4.31. Influence of different row spacing on stem diameter (cm) of diverse
sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 1.67 b 1.70 1.69
H2= SF-187 1.88 a 1.77 1.83
H3= Hysun-33 1.79 ab 1.76 1.78
LSD at 5% 0.14 NS
Row spacing (S)
S1= 45 cm 1.68 b 1.66 b 1.67
S 2= 60 cm 1.76 b 1.75 ab 1.76
S 3= 75 cm 1.90 a 1.82 a 1.86
LSD at 5% 0.10 0.11
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
127
Higher plant populations produced thinner stems, more yield than lesser plant
density (Beg et al., 2007).An increasing trend in stem diameter with decreasing plant
population was however, reported by Ekin et al. (2005), Al-Thabat (2006) and Sedghi et
al. (2008). Different combinations of hybrids and row spacing depicted a non-significant
influence on stem diameters of the used hybrids in these studies (Table 4.31) during both
the years of experimentation.
4.2.1.5 Head diameter
Head diameter contributes substantially to achene yield of sunflower because of its
contribution towards number of achenes per head and achene size. Different sunflower
hybrids produced heads that varied significantly (P≤0.05) in diameter (Table 4.32).
During both the years, SF-87 recorded maximum (18.57-18.14 cm) head diameter and
was followed by Hysun-33 (16.86-16.65 cm) and FH-331(16.10-15.87 cm). SF-187
recorded head diameter that was 15 % larger than that of FH-331 and 5 % larger than that
of Hysun-33. Variation in head size of hybrids of different genetic background was also
reported by Tunio et al. (1999), Reddy et al. (2002), Khaliq (2004) and Iqbal (2008).
Row spacing also significantly affected head diameter and similar trend for both
years was recorded (Table 4.32). On an average, maximum head diameter (18.02 cm) was
recorded for sunflower planted on 75 cm apart rows. Narrowing the row spacing from 75
to 45 cm resulted in 14% decrease in head diameter. Increasing row spacing from 45 to
60 cm produced 9% larger heads and further increase in row spacing (75 cm) further
increased head diameter by 4%.
Different sunflower hybrids planted on variable row spacing depicted significantly
(P≤0.05) different head diameters during both years of experimentation (Table 4.32). SF-
187 recorded the largest head diameter when planted at all row spacings. It was followed
by FH-331 at 45 cm row spacing and Hysun-33 at 60 and 75 cm apart rows. Head
diameter of FH-331 improved to greater extent when row spacing increased from 45 to 60
cm and did not improve with further widening of row spacing. Similarly, head size of SF-
187 showed lesser flexibility to changing row spacing. On the other hand, head diameter
of Hysun-33 showed greatest flexibility to varying row spacing especially when it was
increased from 45 to 60 cm (14.70 vs. 17.5 cm head diameter) that did not improve
anymore by further widening the row spacing.
128
Table 4.32. Influence of different row spacing on head diameter (cm) of diverse
sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 16.10 c 15.87 c 15.99
H2= SF-187 18.57 a 18.14 a 18.36
H3= Hysun-33 16.86 b 16.65 b 16.76
LSD at 5% 0.55 0.60
Row spacing (S)
S1= 45 cm 15.83 c 15.76 c 15.80
S 2= 60 cm 17.49 b 17.08 b 17.29
S 3= 75 cm 18.22 a 17.82 a 18.02
LSD at 5% 0.69 0.46
Interaction (H x S)
H1S1 15.13 ef 15.00 f 15.07
H1S2 16.27 de 15.80 e 16.04
H1S3 16.90 cd 16.80 d 16.85
H2S1 17.77 bc 17.43 bcd 17.60
H2S2 18.40 ab 18.20 ab 18.30
H2S3 19.55 a 18.78 a 19.17
H3S1 14.58 f 14.83 f 14.71
H3S2 17.80 bc 17.25 cd 17.53
H3S3 18.20 b 17.87 bc 18.04
LSD at 5% 0.39 0.80
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
129
Variation in head size of hybrids of different genetic background was also
reported by Tunio et al. (1999), Reddy et al. (2002), Khaliq (2004) and Iqbal (2008).
Row spacing also significantly affected head diameter and similar trend for both years
was recorded (Table 4.32). On an average, maximum head diameter (18.02 cm) was
recorded for sunflower planted on 75 cm apart rows. Narrowing the row spacing from 75
to 45 cm resulted in 14% decrease in head diameter. Increasing row spacing from 45 to
60 cm produced 9% larger heads and further increase in row spacing (75 cm) further
increased head diameter by 4%.
Plants planted at higher plant populations produced lighter seeds, thinner stems,
taller plants and more yield than lesser plant density (Beg et al., 2007).
Different sunflower hybrids planted on variable row spacing depicted significantly
(P≤0.05) different head diameters during both years of experimentation (Table 4.32). SF-
187 recorded the largest head diameter when planted at all row spacings. It was followed
by FH-331 at 45 cm row spacing and Hysun-33 at 60 and 75 cm apart rows. Head
diameter of FH-331 improved to greater extent when row spacing increased from 45 to 60
cm and did not improve with further widening of row spacing. Similarly, head size of SF-
187 showed lesser flexibility to changing row spacing. On the other hand, head diameter
of Hysun-33 showed greatest flexibility to varying row spacing especially when it was
increased from 45 to 60 cm (14.70 vs. 17.5 cm head diameter) that did not improve
anymore by further widening the row spacing.
4.2.1.6 Number of achenes per head
Number of achenes per head differed significantly (P≤0.05) among the three
hybrids during both years of experimentation (Table 4.33). During both the years, FH-331
and SF-187 recorded similar number of achenes per head (657 vs. 678) that was out
yielded by those of Hysun-33 with 789 achenes per head. Hysun-33 recorded 16 and 20
percent higher number of achenes per head than SF-187 and HS-331, respectively.Several
other authors (Ahmad et al. 1997, Saleem and Malik, 2004 and Iqbal (2008) have
reported such significant differences among various hybrids.
Row spacing also had a significant (P≤0.05) bearing upon number of achenes per
head. During 2006, widening the rows from 45 cm to 75 cm, improved achenes per head
by about 12% that was only 8% when rows were widened upto 60 cm and the difference
between 60 and 75 cm was non-significant (P≤0.05). During 2007, the crop that was
130
Table 4.33. Influence of different row spacing on number of achenes head-1 of
diverse sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 655.69 b 657.67 b 657
H2= SF-187 673.80 b 682.68 b 678
H3= Hysun-33 793.80 a 783.33 a 789
LSD at 5% 28.54 26.63
Row spacing (S)
S1= 45 cm 664.09 b 657.83 c 661
S 2= 60 cm 718.20 a 710.78 b 714
S 3= 75 cm 741.00 a 754.83 a 748
LSD at 5% 28.90 27.02
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
131
planted at 75 cm apart rows recorded maximum number of achenes. Narrowing the width
between rows had an oppressive effect on the number of achenes per head and it declined
by 6% and 15% at time when row spacing was decreased to 60 and 45 cm. respectively.
Different sunflower hybrids sown at varying plant spacing showed non-significant
(P≤0.05) differences in number of achenes per head in these studies, during both years of
experimentation. (Table 4.33) Diepenbrock et al. (2001) reported that number of achenes
per head was reduced with decreasing row spacing from 50 to 75 cm, but the quantity of
achenes m-2 increased significantly with decreasing row spacing. These results suggested
that number of achenes per head increased with increasing head size. Nawaz et al. (2001)
also confirmed that number of achenes per head and 1000-achene weight was greater with
the plants sown in wider rows.
4.2.1.7 Number of achenes m-2
Although number of achenes per head gives an insight into the ability of individual plants
towards yield formation but in field crops it is more common to look for management
options where more number of achenes are harvested per unit area. During 2006, FH-331
and SF-187 produced similar (P≤0.05) number of achenes m-2 that were, however, 20 and
17 percent higher than the former hybrids, respectively (Table 4.34). During 2007, the
difference between FH-331 and SF-187 was significant with 4% higher achenes recorded
for later hybrid and Hysun-33 again out yielded both the former hybrids in producing
higher achenes.
Differential response of hybrids to produce achenes per unit area might be
attributed to their genetic variability. Diepenbrock et al. (2001) reported that number of
achenes per head was reduced with decreasing row spacing from 50 to 75 cm, but the
quantity of achenes m-2 increased significantly with decreasing row spacing.
Different row spacing (plant population) had a significant influence on number of
achenes m-2 produced during both years of study (Table 4.34). Narrowing row spacing
(increasing plant population) had a positive bearing on the number of achenes m-2. Crop
planted on 75 cm apart rows recorded lowest number of achenes m-2 that was improved
by 19 and 45% when row spacing was narrowed down to 60 and 45 cm, respectively.
Increase in achenes per unit area was attributed primarily to higher planting density
(Table 4.34), and hence more achenes per unit areas in crop sown at narrow row spacing
132
Table 4.34. Influence of different row spacing on number of achenes m-2 of diverse
sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 4934 b 4935 c 4935
H2= SF-187 5074 b 5126 b 5100
H3= Hysun-33 5914 a 5849 a 5882
LSD at 5% 205.20 173.7
Row spacing (S)
S1= 45 cm 6390 a 6338 a 6364
S 2= 60 cm 5209 b 5244 b 5227
S 3= 75 cm 4323 c 4428 c 4376
LSD at 5% 215.4 227
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
133
as compared with wider row plantation. .Diepenbrock et al. (2001) also reported that
achene number m-2 increased significantly with increasing planting density from 40,000
to 120,000 plants ha-1. Borous et al. (2004) and Calvino et al. (2004) also reported more
achenes per unit area owing to higher planting densities in sunflowers.
Different combinations of sunflower hybrids and row spacing had a non
significant (P≤0.05) influence on number of achenes per m-2 (Table 4.34) revealing that
achenes per unit area increased with narrowing row spacing irrespective of the hybrid.
4.2.1.8 1000-achene weight
Extent of development of achenes under any agronomic practice or of various
hybrids is evaluated on basis of 1000-achene weight, which plays a leading role in yield
formation of sunflower. Achene weight of the three hybrids varied significantly (P≤0.05)
and during both the years of experimentation, FH-31 produced the lightest achenes (Table
4.35). SF-187 recorded maximum achene weight that was 13, and 8 percent higher than
that recorded for FH-331 and Hysun-33, respectively. Although Hysun-33 produced more
number of achenes per head (Table 4.33) than SF-187 but the later had higher head
diameter (Table 4.30) as compared with Hysun-33 implying better development of fewer
achenes in wider head spacing in SF-187. Differential response of sunflower hybrids to
1000-achene weight was also reported by Ahmad et al. (1997), Behrooznia et al. (1999).
Khaliq (2004) and Ekin et al. (2005) reported similar results.
Row spacing (plant population) had also significant (P≤0.05) effect on 1000-
achene weight of sunflower (Table 4.35) during both years of experimentation. On an
average maximum 1000-achene weight (57 g) was recorded when the crop was sown at
75 cm apart row spacing. Achene weight was reduced by 11 and 33 % when row spacing
was decreased to 60 and 45 cm, respectively.
Different combinations of sunflower hybrids and row spacing influenced achene
weight to significant (P≤0.05) level only during 2006. Although achene weight was
improved with reducing planting density (widening row spacing) in all the hybrids but the
response was different. Achene weight of Hysun-33 was improved by 32% when row
spacing was increased from 45 to 60 cm while further improvement was only 8% when
row spacing was increased to 75 cm. In contrary to this, the achene weight of FH-331
improved by only 13% when row spacing was increased from 45 to 60 cm that was 23%
for SF-187. Highest improvement in achene weight was also recorded for the later hybrid
when row spacing was increased from 60 to 75 cm.
134
Table 4.35. Influence of different row spacing on 1000-achene (g) weight of
diverse sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 47.86 c 46.82 c 47.34
H2= SF-187 54.06 a 52.57 a 53.32
H3= Hysun-33 50.06 b 48.67 b 49.37
LSD at 5% 1.23 1.08
Row spacing (S)
S1= 45 cm 42.76 c 42.18 c 42.47
S 2= 60 cm 51.95 b 49.88 b 50.92
S 3= 75 cm 57.28 a 55.99 a 56.64
LSD at 5% 1.72 3.30
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
135
4.2.1.9 Achene yield (kg ha-1)
Achene yield (Table 4.36) of hybrids under study differed significantly (P≤0.05)
during both the years. During 2006, Hysun-33 and SF-187 recorded highest and similar
achene yield (2856 and 2588 kg ha-1) that were 24 and 12 percent higher than that
recorded for FH-331. During 2007, Hysun-33 out yielded both the hybrids by recoding
2741 kg ha-1 achene yield that was 21% higher than achene yield of FH-331 (2256 kg ha-
1) and 9% higher than SF-187 (2519 kg ha-1). Studies have shown that hybrids vary in
their potential to perform under variable environments and yields are different even under
similar conditions. Andrade et al. (2002) reported differential response of Zenit (short
season) and Ramcull (long season) hybrids to yield.
Row spacing significantly influenced achene yield of hybrid sunflower during
both the years of study (Table 4.36). Crop planted in 45 and 60 cm apart rows recorded
highest and similar achene yield during 2006 than that planted in 75 cm apart rows.
However, during 2007, the wider row plantation (75 cm) recorded as good achene yield
as was recorded with 60 cm wide row plantation. The later row distance in turn recorded
achene yield that was similar to that recorded for crop planted at 45 cm apart rows. On an
average, increasing row spacing from 45 cm to 60 and 75 cm reduced achene yield by 4
and 12 percent, respectively, and the difference between later two being 12%.
The response of hybrids to varying row spacing (Table 4.36) was significantly
different (P≤0.05) in terms of achene yield. Achene yield of FH-331 decreased by 14%
when row to row distance was increased from 45 to 60 cm and the reduction was by 23%
when it was increased to 75 cm. SF-187 also recorded decrease in achene yield by
increasing row spacing but the magnitude of decrease was almost 50% than that recorded
for preceding hybrid. In contrary to both of these hybrids, Hysun-33 exhibited increase in
yield by 10% when row distance was increased from 45 to 60 cm that was only 1% when
row distance was widened to 75 cm. However, the achene yield was similar (P≤0.05) at
the three row spacing in this hybrid.
Andrade et al. (2002) reported that the response of Zenit (short season) and
Ramcull (long season) hybrids was encouraging to contracted rows in expressions of
proportionate raise in light interception and achene yield of the sunflower hybrids.
Maximum radiation interception at blossoming in spacious rows was achieved with the
extended season hybrid (Ramcull), and rejection to positive response of achene yield to
contracted rows was experienced, that is contrary to observations of Zaffaroni and
Schneiter (1991).
136
Table 4.36. Influence of different row spacing on achene yield (kg ha-1) of diverse
sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 2311 b 2256 c 2284
H2= SF-187 2588 a 2519 b 2554
H3= Hysun-33 2856 a 2741 a 2799
LSD at 5% 272 217
Row spacing (S)
S1= 45 cm 2722 a 2630 a 2676
S 2= 60 cm 2628 a 2524 ab 2576
S 3= 75 cm 2405 b 2362 b 2384
LSD at 5% 187 166
Interaction (H x S)
H1S1 2633 bc 2533 bcd 2583
H1S2 2267 de 2233 de 2250
H1S3 2033 e 2000 e 2017
H2S1 2783 ab 2740 ab 2762
H2S2 2583 bcd 2450 bcd 2517
H2S3 2398 cd 2367 cd 2383
H3S1 2750 ab 2617 abc 2684
H3S2 3033 a 2888 a 2961
H3S3 2783 ab 2717 ab 2750
LSD at 5% 324 287
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
137
4.2.1.10 Stover yield (kg ha-1)
The three hybrids produced significantly different (P≤0.05) stover yield during
both the years (Table 4.37). Highest stover yield during both the years (8030-7579 kg ha-
1) was recorded for Hysun-33 that was, on an average, 24% higher than stover yield of
FH-331 and 14% higher than that recorded for SF-331. This differential behavior of
varying maturing hybrids was due to inherited capacity of each hybrid. Higher stover
yields of the hybrids are attributed to their respective plant heights which contribute a
large towards stover of sunflower crop. Khaliq (2004) also reported variable stover yield
of sunflower hybrids with different morphological characters.
During 2006, maximum (7621 kg ha-1) stover yield (Table 4.37) was produced
when the sunflower was sown at 45 cm apart rows (98765 plants ha-1). Increasing row
spacing from 45 to 60 cm, resulted in 9% decrease in stover yield that was further
decreased by 7% when crop was planted in 75 cm spaced rows. Almost similar trend of
increasing stover yield with increasing plant population was realized during second year
of experimentation. More stover yield in narrow row plantations was due to taller plants
(Table 4.30) recorded at narrow row spacing.
The three hybrids grown in variable row distances showed a non-significant (P≤0.05)
difference in stover yield during both years of experimentation (Table 4.37).
4.2.1.11. Harvest index (%)
A harvest index (H.I) show the ratio of economic yield to biological yield and is
indicative of the proportionate translocation of assimilates into economic yield. Data
(Table 4.38) exhibited that harvest indices of the three hybrids in present studies did not
vary to significant (P≤0.05) level. Harvest indices were in range of 25.98 to 27.41
percent. Miralles et al. (1997) also reported the non-significant differences in H.Is of
various sunflower hybrids, while Saleem (2004) and Iqbal (2008) reported that H.Is of
different sunflower hybrids varied significantly. Non significant differences in hybrids of
different plant heights might be attributed to concomitant higher achene yields
(Table4.36) associated with taller (long duration) plants thereby resulting in non-
significant H.Is.
Varying row spacing also depicted non-significant (P≤0.05) differences in HIs in
these studies (Table 4.38). Steer et al. (1986) and Diepenbroke et al. (2001) reported that
increasing plant population resulted in decline in H.I. This decrease might be due to more
stover yield (Table 4.37) produced in narrow row spacing (increased plant population).
138
Table 4.37. Influence of different row spacing on stover yield (kg ha-1) of diverse
sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 6117 c 6444 b 6281
H2= SF-187 7028 b 6646 b 6837
H3= Hysun-33 8030 a 7579 a 7805
LSD at 5% 558 660
Row spacing (S)
S1= 45 cm 7621 a 7466 a 7544
S 2= 60 cm 6991 b 6854 ab 6923
S 3= 75 cm 6563 b 6349 b 6456
LSD at 5% 553 710
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
139
Table 4.38. Influence of different row spacing on harvest Index (%) of diverse
sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 27.41 25.98 26.70
H2= SF-187 26.96 27.53 27.25
H3= Hysun-33 26.35 26.67 26.51
LSD at 5% NS NS
Row spacing (S)
S1= 45 cm 26.52 26.16 26.34
S 2= 60 cm 27.34 26.93 27.14
S 3= 75 cm 26.85 27.08 26.96
LSD at 5% NS NS
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
140
4.2.2 Growth
4.2.2.1. Leaf area index
Patterns of development of leaf area index (LAI) are presented in Fig.4.21a&b.
During both the years, leaf area index increased slowly in the beginning of crop season
and crop started fast accumulation of LAI at 45 days after sowing that reached to its
maximum value at 75 days after sowing and started declining thereafter. The differences
amongst the hybrids remained non-significant (P≤0.05) upto 60 days after sowing beyond
which the difference/s in LAIs were more evident. The highest values of LAIs were
reached at flowering stage. Long season hybrid Hysun-33 exhibited highest LAI (5.10),
followed by SF-187 (4.49), which was statistically at par with FH-331 (4.32). Zaffaroni
and Schneiter (1991) reported that semi dwarf and medium stature sunflower hybrids
grown at different row arrangements had non-significant differences in leaf area index
(LAI).
The differences in LAI of sunflowers planted at different row spacing were
significant (P≤0.05) throughout the growing season (Fig.4.22a&b.). During 2006, highest
LAI (5.20) was recorded for the crop sown at 60 cm apart rows that declined to 4.50 and
4.32 for 45 and 75 cm apart rows, respectively. During 2007, maximum LAI (5.01) was
observed when the crop was sown at 45 cm apart row spacing and was statistically at par
with that of the crop planted at 60 cm apart rows, while the lowest (4.46) was recorded at
75 cm apart rows. Similar patterns of LAI for these row spacing were recorded during the
second year. Time of achieving maximum leaf area indices corresponded to their
flowering times in respective row spacing. Zaffaroni and Schneiter (1991) reported that
semi dwarf and medium stature sunflower hybrids grown at different row arrangements
had non-significant differences regarding leaf area index (LAI).
An optimistic and compareable association was observed between LAI and achene
yield of sunflower (Fig. 4.20) and the regression accounted for 77% variance in achene
yield owing to difference in LAIs
141
Lea
f ar
ea in
dex
0
1
2
3
4
5
6
30 45 60 75 90
FH 331 SF 187 Hysun 33
0
1
2
3
4
5
6
30 45 60 75 90
FH 331 SF 187 Hysun 33
Days after sowing
Fig. 4.21: Patterns of leaf area index with time: comparison of different sunflower hybrids during (a) 2006 and (b) 2007 ±SD
(a) 2006
(b) 2007
142
Lea
f ar
ea in
dex
0
1
2
3
4
5
6
30 45 60 75 90
45 cm 60 cm 75 cm
0
1
2
3
4
5
6
30 45 60 75 90
45 cm 60 cm 75 cm
Days after sowing
Fig. 4.22: Patterns of leaf area index with time: comparison of different row spacing during (a) 2006 and (b) 2007
(a) 2006
(b) 2007
143
4.2.2.2 Crop growth rate
Periodic data at fortnight intervals (Fig. 4. 23a&b) revealed that crop growth rate
(CGR) of Hysun-33 progressively increased and achieved maximum value (21.21 g m-2 d-
1) at 75 DAS and declined sharply thereafter; reaching a value of 6.63 g m-2 d-1 at 90 DAS
during 2006. Similar trend was observed during 2007 for this hybrid. Early maturing
hybrid FH-331 recorded maximum CGR (19.30 g m-2 d-1) at 60 DAS that declined
slightly (16.75 g m2 d-1) at 75 DAS and reached lower level (1.85 g m-2 d-1) at 90 DAS.
Almost the same trend was exhibited by SF-187 and the maximum (20.45 g m-2 d-1) and
the minimum (3.81 g m-2 d-1) CGRs were recorded at 60 and 90 DAS, respectively.
During 2007, SF-187 showed slight increase (19.89 to 20.10 g m-2 d-1) in CGR from 60 to
75 DAS and then reached to its minimum (2.47 g m-2 d-1) level at 90 DAS, while FH-331
recorded the similar trend during both years.
Regarding row spacing, crop planted at 45 cm apart rows showed maximum CGR
throughout the growing season as compared to plants grown at 60 and 75 cm apart rows
for both the years.(Fig.4. 24a&b)
Apart from periodic crop growth rates, there were significant differences observed
for hybrids in their mean seasonal crop growth rates (Table4.39). Highest mean seasonal
crop growth rate (14.10-15.67 g m-2 d-1) was recorded for Hysun-33 during both the years
that was followed by SF-187 (12.45-13.81 g m-2 d-1) with the lowest values (10.99-12.04
g m-2 d-1) observed for FH-33. On an average, Hysun-33 exhibited 30 and 13 % higher
seasonal crop growth rate than FH-331 and SF-187, respectively Widening the row
spacing (decreasing plant population) resulted in decrease in mean seasonal crop growth
rate during both the years (Table 4.39). Seasonal crop growth rate was decreased by 8%
when row distance was increased from 45 cm to 60 and declined further up to 24% at 75
cm apart rows of sunflowers.
A non significant interaction between hybrids of different stature under discussion
(Table 4.39) was also in line with the findings of Zaffaroni and Schneiter (1991),who
reported that semi dwarf and medium stature sunflower hybrids grown at different row
arrangements had non-significant differences in relative growth rate
An optimistic and significant association was observed between leaf area index
and crop growth rate of sunflower (Fig. 4. 25) and the regression accounted for 89-94%
variance in crop growth rate owing to differences in leaf area indices.
144
Cro
p gr
owth
rat
e (g
m-1
d-1
)
0
5
10
15
20
25
30
45 60 75 90
FH 331 SF 187 Hysun 33
0
5
10
15
20
25
30
45 60 75 90
FH 331 SF 187 Hysun 33
Days after sowing
Fig. 4.23: Pattern of crop growth rate with time: comparison of different sunflower hybrids during (a) 2006 and (b) 2007 ±SD
(a) 2006
(b) 2007
145
Cro
p gr
owth
rat
e (g
m-1
d-1
)
0
5
10
15
20
25
30
45 60 75 90
45 cm 60 cm 75 cm
0
5
10
15
20
25
45 60 75 90
45 cm 60 cm 75 cm
Days after sowing Fig. 4.24: Pattern of crop growth rate with time: comparison of different row spacing during (a) 2006 and (b) 2007 ±SD
(a) 2006
(b) 2007
146
Table. 4.39 Influence of different row spacing on seasonal crop growth rate (g m-2
day -1) of diverse sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 12.04 c 10.99 c 12.29
H2= SF-187 13.81 b 12.45 b 14.15
H3= Hysun-33 15.67 a 14.10 a 16.02
LSD at 5% 0.65 0.41
Row spacing (S)
S1= 45 cm 15.32 a 13.60 a 15.54
S 2= 60 cm 14.15 b 12.65 b 14.38
S 3= 75 cm 12.55 c 11.29 c 12.55
LSD at 5% 0.45 0.40
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
147
C
rop
grow
th r
ate
(g m
-2 d
-1)
y = 6.002x - 4.4111
R2 = 0.9404
0
2
4
6
8
10
12
14
16
0 1 2 3 4
y = 8.8081x - 11.491
R2 = 0.8926
0
2
4
6
8
10
12
14
16
18
20
1 2 3 4
Leaf area index
Fig. 4.25. Relationship between crop growth rate (g m-2 d-1) and leaf area index a) 2006, b) 2007
(a)
(b)
148
4.2.2.3 Net assimilation rate
Net assimilation rate (NAR) is the net gain of photosynthetic assimilates per unit
of assimilatory surface and time. Data on NAR (Table 4.40) revealed that seasonal NAR
differed significantly (P≤0.05) for different hybrids. Maximum and similar NAR were
observed for Hysun-33 and SF-187 (4.98 vs. 4.88 g m-2 d-1) as compared with FH-187
(4.47 g m-2 d-1) during both the years. On an average, SF-187 and Hysun-33 recorded 9
and 11 percent higher seasonal net assimilation rate, respectively than FH-331. Zaffaroni
and Schneiter (1991) reported that semi dwarf and medium stature sunflower hybrids
grown at different row arrangements had non-significant differences net assimilation rate
(NAR).
Regarding row spacing, there was significant (P≤0.05) decrease in net assimilation
rate with widening the row spacing (increase in plant population). Maximum mean NAR
(5.00 g m-2 d-1) was recorded when the crop was grown at row spacing of 45 cm and it
was 10% higher than that recorded for crop planted in 75 cm apart rows. The three
hybrids sown at varying row spacing exhibited similar (P≤0.05) responses in terms of
mean net assimilation rate (Table4.40).
4.2.2.4. Dry matter accumulation
The patterns of total dry matter (TDM) accumulation in different hybrids
throughout the crop growth period during both the years of experimentation are presented
in Fig 4.26. Three hybrids accumulated total dry matter to similar extent until 45 days
after sowing after which the differences among Hysun-33, SF-187 and FH-331 became
significant (P≤0.05) till harvest and the differences grew to the maximum at 90 DAS.
Hysun-33, SF-187 and FH-331 produced 1004,890 and 783 g m-2 TDM during 2006 and
the corresponding values for the year 2007 were 909,807 and 719 g m-2 (Table 4.41). On
an average, Hysun-33 recorded 12% more TDM than SF187 that was also 27% higher
than that observed for FH-331.The higher TDM production by Hysun-33 may be
attributed to its higher plant height as compared with rest of the hybrids (Table4.41).
Lower biomass production by the short duration hybrid (FH-331) might be due to low
quantity of radiation potentially available over the crop growth duration. Miralles et al.
(1997), Angadi and Entz (2001) and Khaliq (2004) also recorded significant differences
for TDM production by hybrids of different stature. Seasonal accumulation of total dry
matter was, in general, slow until 45 DAS in all the planting densities (Fig 4.27) and
subsequent increase in TDM was sharper and it reached to its maximum at 90 DAS.
Significant differences were recorded for TDM among varying row spacing (Table4.41).
149
Table 4.40. Influence of different row spacing on net assimilation rate (g m-2 day-1)
of diverse sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 4.71 b 4.22 b 4.47
H2= SF-187 5.06 a 4.69 a 4.88
H3= Hysun-33 5.07 a 4.88 a 4.98
LSD at 5% 0.21 0.24
Row spacing (S)
S1= 45 cm 5.15 a 4.84 a 5.00
S 2= 60 cm 4.98 b 4.66 b 4.82
S 3= 75 cm 4.69 c 4.29 c 4.49
LSD at 5% 0.17 0.14
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS= Non-significant
150
Tot
al d
ry m
atte
r (g
m-1
)
0
200
400
600
800
1000
1200
30 45 60 75 90
FH 331 SF 187 Hysun 33
0100
200300
400500600
700800
9001000
30 45 60 75 90
FH 331 SF 187 Hysun 33
Days after sowing
Fig. 4.26: Pattern of total dry matter accumulation with time: comparison of different sunflower hybrids during (a) 2006 and (b) 2007 ±SD
(a) 2006
(b) 2007
151
Tot
al d
ry m
atte
r (g
m-1
)
0
200
400
600
800
1000
1200
30 45 60 75 90
45 cm 60 cm 75 cm
0
100
200
300
400
500
600
700
800
900
1000
30 45 60 75 90
45 cm 60 cm 75 cm
Days after sowing
Fig. 4.27: Patterns of total dry matter with time: comparison of different row spacing during (a) 2006 and (b) 2007 ±SD
(a) 2006
(b) 2007
152
Table 4.41 Influence of different row spacing on total dry matter (g m-2) of diverse
sunflower hybrids.
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significance
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 783 c 719 c 751
H2= SF-187 890 b 807 b 848
H3= Hysun-33 1004 a 909 a 956
LSD at 5% 40.98 25.76
Row spacing (S)
S1= 45 cm 987 a 884 a 935
S 2= 60 cm 912. b 820 b 866
S 3= 75 cm 778 c 732 c 755
LSD at 5% 25 23.71
Interaction (H x S)
H1S1 882d 794 d 838
H1S2 783 e 715 e 749
H1S3 684 f 648 f 660
H2S1 972 c 883 c 928
H2S2 903 d 813 d 858
H2S3 795 e 727 e 762
H3S1 1107 a 973 a 1040
H3S2 1050 b 932 b 991
H3S3 855 d 820 d 837
LSD at 5% 44.57 41.07
153
A
chen
e yi
eld
(kg
ha-1
)
y = 2.602x + 472.6
R2 = 0.8056
0
500
1000
1500
2000
2500
3000
3500
0 200 400 600 800 1000 1200
y = 1.6889x + 997.69
R2 = 0.6718
0500
1000150020002500
30003500
200 400 600 800 1000 1200
Total dry weight
Total dry weight (kg ha-1) Fig. 4.28 Relationship between achene yield (kg ha-1)and dry weight (g m-2)
a) 2006, b) 2007
(a)
(b)
154
Increase in row spacing resulted in decrease in TDM production during both the
years of experimentation. On an average highest TDM (935.52 g m-2) was produced when
the sunflower crop was sown at 45 cm apart rows. TDM decreased by 8 and 24 % when
row distance was increased to 60 and 75 cm, respectively.
Hall et al.(1995) recorded an increase in total biomass yield of sunflower from
794 to 906 g m-2 by increasing plant population from 2.4 to 4.8 plants m-2.Ferreira and
Abreu (2001) also reported similar findings regarding total dry mater production under
varying planting densities.
Different sunflower hybrids planted at varying row spacing recorded significant
(P≤0.05) differences in total dry mater production during both the years of
experimentation (Table 4.41). Total dry matter production in all the hybrids decreased as
row to row spacing was increased but the pattern of decrease was quite different in the
three hybrids. Widening row spacing from 45 to 60 cm (decreasing planting density)
decreased TDM in FH-331, SF-187 and Hysun-33 by 11, 8 and 5 percent, respectively
which was reduced further by 12, 11 and 15 percent when row spacing was increased up
to 75 cm.Data depicted a significant and positive correlation between achene yield and
total dry weight (Fig. 4.28). Regression accounted for 74 % variance in yield owing to
differences in TDM. Such positive and significant correlation between TDM and
sunflower achene yield has also been reported by Pathak(1974) and Zaffaroni and
Schneiter (1991).
4.2.2.5. Leaf area duration
Differences in maximum leaf area indices may not explain precisely the variation in
total dry matter and achene yield in response to agronomic treatments. Therefore,
sometimes leaf area duration (LAD) accounts for differences in yield in response to
different treatments. LAD expresses the number of days that a square meter of leaf
surface covered a square meter of ground. At any particular moment e.g. pace of
establishment, extent and rate of regression, all the settings of photosynthesizing system
are taken into account by LAD (Miralles et al., 1997). To observe the significance of
photosynthetic vicinity throughout growth (appearance to maturity) LAD was estimated
(Table 4.42) There were significant differences among the hybrids under study during
both the years. Hysun-33 showed maximum (205.54 d) LAD that was 3 and 10 % higher
than that observed for SF-187 and FH-331, respectively. Hysun-33, which has longer
155
Table 4.42. Influence of different row spacing on leaf area duration (days) of
diverse sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 185.22 c 176.22 c 180.68
H2= SF-187 189.44 b 184.00 b 186.68
H3= Hysun-33 205.33 a 205.78 a 205.54
LSD at 5% 1.95 7.12
Row spacing (S)
S1= 45 cm 203.78 a 197.56 a 200.67
S 2= 60 cm 195.00 b 189.56 b 192.28
S 3= 75 cm 181.22 c 178.89 c 180.05
LSD at 5% 5.11 3.50
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
156
growth period (Table 4.29) than the other two hybrids, stood out for its maximum LAD
(205.54 d) due to the highest maximum LAI (Fig.4.21), which also coincides with
thehighest values of TDM (Table 4.41 ).Miralles et al. (1997) and Khaliq (2004) also
recorded similar results for LAD of sunflower hybrids of varying maturity and
morphophysiological traits.
There was significant difference in LAD when sunflower was sown at different
row spacing (planting density). Maximum LAD was recorded when the crop was sown at
45 cm apart rows and progressively decreased with widening row spacing (Table4.42).
On an average, LAD decreased by 4 and 11 percent when row spacing was increased
from 45 to 60 and 75 cm, respectively. This decrease in LAD for the sunflower crop sown
in wider rows (low planting density) might be attributed to relatively lower LAIs (leaf
area per unit of land area). Khaliq (2004) reported similar ranges of LADs for sunflowers
grown under similar set of environmental conditions.Different sunflower hybrids
recorded similar (P≤0.05) leaf area durations when planted under varying row spacing
during both years of experimentation (Table 4.42)
4.2.2.6 Cumulative radiation interception
Leaf area index and canopy architecture determine the extent to which a crop can
intercept photosynthetically active radiation which, in turn is instrumental in determining
crop biomass accumulation and its partitioning within the plant (Van der Werf, 1996).
Data presented in Table 4.43 reflects the effect of hybrids of varying maturity
groups sown in different row spacing on accumulated radiation interception (AIR).
During both the years Hysun-33 recorded highest values for AIR (517.6-527.7 MJm-2)
and was followed by SF-187 (505.3-5138 MJm-2). On an average, AIR by Hysun-33 was
4% higher than that recorded for FH-331 and 2% higher than that for SF-187. Dosio et al.
(2000) reported variation in photosynthetically active radiation intercepted by two
genetically different hybrids (Dekalb and NKT). Khaliq (2004) and Iqbal (2008) reported
similar findings for radiation interception by hybrids of varying maturity under similar
environmental conditions.
Row spacing and planting density may be used as a management tool to optimize
the time required for a crop to fully intercept available light (Ball et al., 2000). Increasing
row spacing (decreased planting density) exhibited an antagonistic influence of radiation
interception during both years of experimentation (Table 4.45). Maximum radiation
interception (527 MJ m-2) was the outcome of sunflower planted at 45 row spacing and it
157
Table 4.43. Influence of different row spacing on cumulative radiation interception
(M.J.m-2) (cm) of diverse sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 502.8 c 497.6 c 500.2
H2= SF-187 513.80 b 505.3 b 509.55
H3= Hysun-33 527.70 a 517.6 a 522.65
LSD at 5% 2.92 4.13
Row spacing (S)
S1= 45 cm 527 a 517.8 a 522.4
S 2= 60 cm 514.2 b 506 b 510.1
S 3= 75 cm 503.10 c 496.70 c 499.9
LSD at 5% 4.54 4.13
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
158
Cum
ulat
ive
inte
rcep
ted
radi
atio
n (M
J m
-2)
y = 51.953x + 368.27
R2 = 0.8959
400
420
440
460
480
500
520
540
560
0 1 2 3 4
y = 0.0177x - 6.0856
R2 = 0.9577
2.00
2.20
2.40
2.60
2.80
3.00
3.20
3.40
480 490 500 510 520 530
Leaf area index
Fig. 4.29. Relationship between cumulative intercepted radiation (MJ m-2) and leaf area index a) 2006, b) 2007
(a)
(b)
159
A
chen
e yi
eld
(kg
ha-1
)
y = 18.179x - 6772.6
R2 = 0.794
0
500
1000
1500
2000
2500
3000
3500
450 470 490 510 530 550
y = 18.722x - 6983.7
R2 = 0.7499
0
500
1000
1500
2000
2500
3000
3500
420 440 460 480 500 520 540
Cumulative intercepted radiation
Fig. 4.30. Relationship between achene yield (kg ha-1)and cumulated intercepted radiation (MJ m-2)a) 2006, b) 2007
was 4.75% higher of the crop grown at 75 cm row distance. Andrade et al. (2002) also
recorded an increase in light interception by the sunflower crop sown with reduced row
spacing (higher planting density).
All the hybrids under study exhibited similar (P≤0.05) levels of radiation interception
when planted under varying row spacing (Table 4.43).
There was a positive and linear relationship between LAI and cumulative
radiation interception (Fig. 4.29) and regression accounted for 89-96 % variance during
both years of study. The dependence of fractional intercepted radiation on leaf area index
(a)
(b)
160
was also recorded by Ferreira and Abreu (2001). A positive and linear relationship was
also observed between cumulative light interception and achene yield of sunflowers (Fig.
4.30) and regression accounted for 74-79 % of variance in achene yield owing to
accumulated intercepted radiation by the crop. Such positive response was also reported
by Ferreira and Abreu (2001).
4.2.2.7 Radiation utilization efficiency (RUETDM)
Extent of dry matter accumulation and its partitioning within the plant are
important determinants of crop yields (Werf, 1996). Rate and extent of dry matter
accumulation by the crop depends on ability of the crop canopy to intercept incident
photosynthetically active radiation (IPAR) and the efficiency with which this radiation
can be converted into new biomass i.e. radiation use efficiency (Sinclair and Muchow,
1999).. Radiation use efficiency is a conservative quantity (Monteith and Elson, 1983).
The perusal of data realized that the hybrids differed significantly (P≤0.05) in radiation
use efficiency for TDM (Table 4.44). Hysun-33 utilized radiation more efficiently (1.98-
1.94 g MJ-1) for total dry matter accumulation, which was, 22% greater than the early
maturing hybrid (FH-331) and 9% higher than the mid season hybrid (SF-187)..
Decreasing plant population (increasing row spacing) showed a depressing effect
on radiation use efficiency on unit area basis. (Table 4.44). Maximum radiation utilization
(1.92 g MJ-1) for TDM buildup was observed for the crop sown at narrow (45 cm) row
spacing. Increasing the row spacing from 45 to 60 cm recorded 5% decrease in RUETDM
and further widening the row spacing from 60 to 75 cm further experienced a 12%
decrease in RUETDM.
The interactive influence of hybrids and row spacing on RUETDM was significant
(P≤0.05) only during 2007 wherein Hysun-33 planted in 45 and 60 cm apart rows
recorded the highest RUE that declined significantly when row spacing was increased to
75 cm. Minimum RUETDM (1.40 g M.J-1) was realized by FH-331 planted at row spacing
of 75 cm. Khaliq (2004) and Iqbal (2008) also reported similar findings for sunflower in
the same environmental conditions.
161
Table 4.44. Influence of different row spacing on radiation use efficiency (tdm) (gMJ-
1) of diverse sunflower hybrids.
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 1.65 c 1.57 c 1.61
H2= SF-187 1.81 b 1.76 b 1.79
H3= Hysun-33 1.98 a 1.94 a 1.96
LSD at 5% 0.06 0.09
Row spacing (S)
S1= 45 cm 1.93 a 1.90 a 1.92
S 2= 60 cm 1.83 b 1.80 b 1.82
S 3= 75 cm 1.67 c 1.56 c 1.62
LSD at 5% 0.06 0.05
Interaction (H x S)
H1S1 1.78 1.73 cd 1.76
H1S2 1.66 1.58 f 1.62
H1S3 1.51 1.40 g 1.46
H2S1 1.93 1.88 b 1.91
H2S2 1.82 1.79 c 1.81
H2S3 1.67 1.61 ef 1.64
H3S1 2.08 2.11 a 2.10
H3S2 2.02 2.03 a 2.02
H3S3 1.83 1.68 c 1.75
LSD at 5% NS 0.08
162
4.2.2.8. Radiation use efficiency for grain (RUEGrain)
Table 4.45 showed that radiation use efficiency for grain yield (RUEGrain) varied
significantly (P≤0.05) among different sunflower hybrids for both the years. During 2006,
Hysun-33 and SF-187 recorded maximum and similar (P≤0.05) RUEGrain (0.54 and 0.50 g
MJ-1) as against the minimum (0.46 g MJ-1) recorded for FH-331. The later hybrid was
also at par with SF-187. Similar trend was observed during 2007, except that FH-331 had
lowest RUEGrain in this year. On an average, Hysun-33 recorded 17 and 9 percent higher
RUEGrain as compared with FH-331 and SF-187, respectively.
Sunflowers planted at variable row spacing exhibited non-significant (P≤0.05)
differences for RUEGrain during both years of experimentation (Table 4.45).
Different sunflower hybrids exhibited differential response towards RUEGrain
when planted at variable row spacing (Table 4.46). Both FH-331 and SF-187 observed a
decline (18 and 9 %, respectively) in RUEGrain with widening the rows from distance of
45 cm to 60 cm. In contrary, Hysun-33 exhibited a 12% gain in RUEGrain for same
increase in row spacing. By further widening the rows from 60 to 75 cm, decline in
RUEGrain resulted in all the hybrids under study. Again, when RUEGrain was compared for
45 and 75 cm spaced planting, FH-331 and SF-187 showed a decline of 18 and 9 percent,
respectively while Hysun-33 recorded a gain of 6%.
An optimistic and noteworthy association was experienced between (RUEGrain)
and achene yield of sunflower (Fig. 4.31) and the regression accounted for 98% variance
in achene yield owing to difference in radiation use efficiency.
4.2.3 Quality Characteristics
4.2.3.1 Achene oil content
Achene oil contents differed significantly ,when diverse hybrids were studied
(Table4.46). During first year, maximum and comparable (P≤0.05) achene-oil content
(42.89-42.56 %) was recorded for hybrids Hysun-33 and FH-331. Comparatively lower
(by 6%) achene-oil content was observed for SF-187. Same tendency was observed
during second year, with oil content being relatively on upper side in this year.
Ahmad and Hassan,(2000) reported that oil contents in sunflower hybrids
maturing and harvested at higher temperature (June) were comparable with those
maturing and harvested in April (Hassan, 2000). Higher achene-oil content in late
maturing hybrid is in agreement with previous findings (Dubbelde, 1989; .El-Hinnaway
et al., 1981) who reported increase in oil contents of sunflower with increase in maturity.
163
Table 4.45. Influence of different row spacing on radiation use efficiencygrain
(gMJ-1) of diverse sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 0.46 b 0.45 b 0.46
H2= SF-187 0.50 ab 0.50 a 0.5
H3= Hysun-33 0.54 a 0.53 a 0.54
LSD at 5% 0.059 0.041
Row spacing (S)
S1= 45 cm 0.52 0.50 0.51
S 2= 60 cm 0.51 0.49 0.5
S 3= 75 cm 0.48 0.47 0.47
LSD at 5% NS NS
Interaction (H x S)
H1S1 0.51 bc 0.50 bc 0.5
H1S2 0.45 cd 0.45 cd 0.45
H1S3 0.42 d 0.41 d 0.41
H2S1 0.53 ab 0.53 ab 0.53
H2S2 0.50 bc 0.49 bc 0.49
H2S3 0.48 bc 0.48 bc 0.48
H3S1 0.51 bc 0.50 abc 0.5
H3S2 0.57 a 0.56 a 0.56
H3S3 0.54 ab 0.53 ab 0.53
LSD at 5% 0.018 0.056
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
164
Ach
ene
yiel
d (k
g ha
-1)
y = 6367.4x - 606.05
R2 = 0.9806
0
500
1000
1500
2000
2500
3000
3500
0.0 0.2 0.4 0.6 0.8
y = 6126.5x - 518.57
R2 = 0.9807
0
500
1000
1500
2000
2500
3000
3500
0.0 0.1 0.2 0.3 0.4 0.5 0.6
RUEgrain
Fig. 4.31. Relationship between achene yield (kg ha-1)and radiation use efficiency (RUEGrain) a) 2006, b) 2007
(a)
(b)
165
Varying row spacing (different planting densities) had significant (P≤0.05)
influence on the oil content of sunflower during 2006&2007(Table 4.46). Sunflower
grown in narrow rows exhibited more achene-oil content than that sown in wider rows.
Maximum oil content (43.22%) was gained, when the crop was sown at 45 cm row
spacing. It was followed by the crop sown at row spacing of 60 and 75 cm apart rows
with achene-oil content of 41.78 % and 40.78 % (Table 4.46). Stear et al. (1986) stated
that oil yield per plant was reduced by rising plant density; while the percentage of oil in
seed was not exaggerated by dense population.
Different hybrids grown under varying row spacing exhibited similar response
with reference to their achene-oil concentration (Table 4.46)
4.2.3.2 Oil yield (kg ha-1)
The ultimate objective in oilseed crop production is the oil yield, which is a
product of achene yield and achene oil contents in case of sunflower. Sunflower has been
rightly named as an oil-crop owing to its higher oil harvested per unit area. Data (Table
4.47) indicated that oil yield of sunflower hybrids differed significantly (P≤0.05) during
both years. Hysun-33 recorded highest oil yield (1214 kg ha-1) that was 13% more than
oil yield of SF-187 (1062 kg ha-1) and 24% higher than that of FH-331 (922 kg ha-1).
Comparably higher oil yield in Hysun-33 may be explained by its higher achene yield
(Table 4.36) and achene-oil content (Table 4.46) in this hybrid as compared with the other
hybrids.
Although oil yield of sunflower planted in varying row spacing differed
significantly (P≤0.05) during 2006 but the magnitude of such differences was not as high
as was observed for those recorded in hybrids. Similar oil yield was recorded in crop
planted in 45 and 60 cm rows. The later row spacing also yielded similar oil as was
recorded for crop sown in 75 cm row. In contrary to this, the sunflowers planted in
varying row spacing exhibited non-significant (P≤0.05) differences during 2007.
Regarding interaction between hybrids and row spacing (Table 4.47), it was found
to be non-significant during 2006 and significant differences (P≤0.05) were recorded for
the year 2007.The combination of Hysun-33 and 60 cm row spacing produced the highest
(1265 Kg ha-1) oil yield and was statistically at par with the oil yield (1216 Kg ha-1)
produced by the same hybrid sown at 75 cm apart rows. On the other hand, remaining
both hybrids (SF-187 and FH-331) exhibited significantly higher oil yields on narrow (45
and 60 cm) row spacing as compared to wider (75 cm) row spacing. The lowest oil yield
166
Table 4.46. Influence of different row spacing on achene oil contents (%) of diverse
sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 42.56 a 42.78 ab 42.67
H2= SF-187 40.33 b 41.24 b 40.79
H3= Hysun-33 42.89 a 43.69 43.29
LSD at 5% 1.33 1.73
Row spacing (S)
S1= 45 cm 43.22 a 44.06 a 43.64
S 2= 60 cm 41.78 b 42.24 b 42.01
S 3= 75 cm 40.78 b 41.41 b 41.10
LSD at 5% 1.37 0.98
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
167
Table 4.47. Influence of different row spacing on oil yield (kg ha-1) of diverse
sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 924 c 919 c 922
H2= SF-187 1066 b 1058 b 1062
H3= Hysun-33 1228 a 1200 a 1214
LSD at 5% 133 114.4
Row spacing (S)
S1= 45 cm 1105 a 1087 1096
S 2= 60 cm 1092 ab 1069 1081
S 3= 75 cm 1021 b 1021 1021
LSD at 5% 83 NS
Interaction (H x S) NS
H1S1 1132
1008 cd 1070
H1S2 1060
914 de 962
H1S3 1005
836 e 921
H2S1 1156
1133 bc 1145
H2S2 1304
1028 cd 1166
H2S3 1223
1012 cd 1118
H3S1 1027
1120 bc 1074
H3S2 910
1265 a 1088
H3S3 834
1216 ab
LSD at 5% NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
168
(836 kg ha-1) was recorded by the hybrid FH-331 sown at the row spacing of 45 cm.
4.2.3.3 Achene protein content
Achene protein content varied significantly among the different hybrids (Table
4.48). SF-187 had highest achene protein content (20.97%) as compared with the lowest
(19.03%) for Hysun-33. The local hybrid FH-331 accumulated as high protein (20.13%)
as was recorded for SF-187. During 2007, FH-331 and SF-187 recorded similar (P≤0.05)
achene-protein concentration. Opposite trend of oil and protein content in different
hybrids may be the explanation for this lesser amount of protein in Hysun-33 hybrid. The
inverse relationship between oil and protein concentration in seed has also been recorded
by Goffner et al. (988) and Singh et al. (1988) and the major cause of this inverse
relationship is the continuing deposition of oil, which has diluting effects on protein in
such hybrids.
The significant differences in protein contents of diverse sunflower hybrids have
also been reported by Khaliq (2004), Saleem (2004) and Iqbal (2008).
Widening the row spacing (increasing plant population) affected the protein
contents negatively during both years (Table 4.48). During 2006, highest protein content
(22.28%) was registered with the crop sown in wider (75 cm) rows. Corresponding values
for crop planted at 60 and 45 cm wide rows were 21.25% and 20.68%, respectively
(Table4.48). Similar trend was observed during 2007. Means of two years revealed 3 and
8 percent increase in achene-protein when row spacing was increased from 45 to 60 and
75 cm, respectively.Non-significant (P≤0.05) differences were recorded in achene-protein
concentration under varying row spacing during both the years of experimentation (Table
4.48) indicating similar response of hybrids to varying plant density.
4.2.3.4 Fatty acid profile
4.2.3.4.1. Palmitic acid concentration (%)
Data (Table 4.49) revealed that palmitic acid concentration did not vary
significantly (P≤0.05) for FH-331 and SF-187 (5.67 vs 5.46 %) and was higher than that
recorded for Hysun-33 (4.90%). On an average FH-331 and SF-187 recorded 14 and 4
percent higher palmitic acid concentration than Hysun-33.
The supporting results were achieved by Ahmad (1999) and Khaliq (2004) who
conducted the experiment under similar environmental conditions. Contrary to this,
Saleem (2004), Cecarmi et al. (2004) and Iqbal (2004) reported non-significant
differences among various hybrids for their palmitic acid concentration in the achene-oil.
169
Table 4.48. Influence of different row spacing on protein contents (%) of diverse
sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 21.02 a 20.13 a 20.58
H2= SF-187 22.61 a 20.97 a 21.79
H3= Hysun-33 20.59 b 19.03 b 19.81
LSD at 5% 0.84 0.86
Row spacing (S)
S1= 45 cm 20.68 a 19.34 c 20.01
S 2= 60 cm 21.25 b 19.96 b 20.61
S 3= 75 cm 22.28 a 20.83 a 21.55
LSD at 5% 0.73 0.43
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
170
Table 4.49. Influence of different row spacing on palmitic acid concentration (%)
of oil of diverse sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 5.94 a 5.41 a 5.68
H2= SF-187 5.79 a 5.13 a 5.46
H3= Hysun-33 5.38 b 4.42 b 4.90
LSD at 5% 0.18 0.33
Row spacing (S)
S1= 45 cm 5.63 4.93 5.28
S 2= 60 cm 5.73 5.01 5.37
S 3= 75 cm 5.76 5.01 5.39
LSD at 5% NS NS
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
171
Qadir et al. (2006) reported that in autumn, Hysun-33 produced significantly highest oil
contents (49.65%), as compared to Award (44.66%) and there were significant
differences observed for fatty acid composition.
Varying row spacing had non-significant (P≤0.05) bearing upon palmitic acid
concentration in achene-oil of sunflowers during both years of experimentation (Table
4.49).Non-significant differences (P≤0.05) were also observed for palmitic acid
concentration in achene-oil of different hybrids planted at varying row spacing (Table
4.49).
4.2.3.4.2. Stearic acid concentration (%)
Stearic acid is categorized as saturated fatty acid, and is an undesirable oil quality
characteristic. The perusal of data (Table 4.50) revealed that different hybrids showed
significant (P≤0.05) difference for the stearic acid concentration in sunflower oil during
both year of experimentation. Hysun-33 recorded highest (3.97%) stearic acid
concentration as compared with FH-331(3.67%) and SF-187 (3.61%) which revealed
non-significant difference between them. Ahmad (1999) and Iqbal (2008) reported non-
significant differences among various hybrids, while the results recorded by Khaliq
(2004) are in line with the differential behavior of diverse sunflower hybrids under
discussion.
Sunflower crop sown at different row spacing (plant density) showed non-
significant (P≤0.05) effect on stearic acid concentration of its achene-oil (Table4.50).
Similarly interaction between hybrids and row spacing was found to be non-significant
during both years of study.
4.2.3.4.3 Oleic acid concentration (%)
Concentration of oleic acid (18:1) in achene oil of sunflower varied significantly
(P≤0.05) among hybrids (Table 4.51) and was in order of Hysun-33>FH-331>Sf-187
during both years of experimentation. On an average Hysun-33 recorded highest
(10.70%) oleic acid concentration that was 7% and 22% higher than that exhibited by FH-
331 (9.96%) and SF187 (8.80%), respectively. Skoric et al. (1978), Ahmad et al. (1999)
and Khaliq (2004) also reported variation in oleic acid concentration of oil of different
sunflower hybrids.
Sunflowers planted at variable row spacing exhibited non-significant (P≤0.05)
differences for oleic acid concentration during both years of experimentation (Table
4.51).
172
Table 4.50. Influence of different row spacing on stearic acid concentration (%) of
oil of diverse sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 3.72 b 3.63 b 3.67
H2= SF-187 3.65 b 3.57 b 3.61
H3= Hysun-33 3.94 a 4.01 a 3.97
LSD at 5% 0.12 0.10
Row spacing (S)
S1= 45 cm 3.74 3.57 3.65
S 2= 60 cm 3.79 4.01 3.90
S 3= 75 cm 3.77 3.63 3.70
LSD at 5% NS NS
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
173
Table 4.51. Influence of different row spacing on oleic acid concentration (%) of
oil of diverse sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 10.08 b 9.84 b 9.96
H2= SF-187 8.89 c 8.71 c 8.80
H3= Hysun-33 10.82 a 10.58 a 10.70
LSD at 5% 0.38 0.39
Row spacing (S)
S1= 45 cm 9.84 9.61 9.73
S 2= 60 cm 9.94 9.72 9.83
S 3= 75 cm 10.02 9.79 9.91
LSD at 5% NS NS
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
174
Interactive effects of hybrids and different row spacing on the oleic acid concentration
were also found to be non significant (P≤0.05) during both the years of study.
4.2.3.4. 4. Linoleic acid concentration (%)
During both the years, linoleic acid concentration did not vary significantly
(P≤0.05) among different hybrids (Table 4.52). Ahmad et al. (1997), Saleem (2004) and
Iqbal (2008) also recorded non-significant differences among hybrids of different
maturity and plant height, while Khaliq (2004) recorded significant differences in linoleic
acid content of various sunflower hybrids.
Different combinations of hybrids and row spacing also showed a non-significant
(P≤0.05) influence on linoleic acid concentration in achene-oil of sunflower during both
years of study (Table 4.52).
175
Table 4.52. Influence of different row spacing on linoleic acid concentration (%)
of diverse sunflower hybrids.
Treatments 2006 2007 Mean
Hybrids (H)
H1= FH-331 79.14 80.00 79.57
H2= SF-187 80.04 81.78 80.91
H3= Hysun-33 77.67 78.67 78.67
LSD at 5% NS NS
Row spacing (S)
S1= 45 cm 78.89 80.11 79.50
S 2= 60 cm 79.19 80.67 79.93
S 3= 75 cm 78.76 79.67 79.22
LSD at 5% NS NS
Interaction (H x S) NS NS
Means having different letters within a column differ significantly from each other at 5%
probability level; NS = Non-significant
176
DISCUSSION
There was a non-significant (P≤0.05) difference in final plant population among
the hybrids (Table 4.28) which might be attributed to uniform germination and seedling
establishment of the three hybrids as well as absence of lodging in any of the hybrids used
in these studies. Saleem (2004) and Iqbal (2008) also recorded non-significant differences
in final number of plants per unit area for various sunflower hybrids. At a constant plant
to plant distance of 22.5 cm used in these experiments, widening the row spacing from 45
to 60 cm resulted in 33% decrease in plan density that declined further by 24% when the
crop was sown at 75 cm row spacing (Table 4.28).Change in the number of plants m-2
was also recorded by Iqbal (2008) with variation in row to row distance. During both the
years, Hysun-33 took 102 days to reach its maturity and was different with rest of the
hybrids (SF-187 and FH-331) which were statistically at par with each other (Table 4.29).
Steer and Hocking (1987) reported that there were small differences in time taken from
sowing to maturity among short stature (early maturity) and taller (late maturity) hybrids.
Johnson and Schneiter (1998) reported hybrids representing the greatest available
diversity for maturity and plant height The differential response of sunflower hybrids
regarding time taken to maturity may attributed to variable genetic character for the
respective hybrids to this trait. Iqbal (2008) also recorded significant difference among
the hybrids for time taken to maturity. Sunflower crop sown at varying row spacing did
not affect the time taken to maturity and results depicted in Table 4.29 showed non-
significant (P≤0.05) difference for the time taken to maturity among different planting
densities.
Varying row spacing (plant population) had a significant (P≤0.05) effect on plant
height (Table 4.30) and tallest plants (157.67 cm) were produced when crop was sown in
45 cm apart rows (98765 plants ha-1) as against the shortest (149.44 cm) recorded in 75
cm row spacing (59259 plants ha-1). These results reflected that plant height increased
with decrease in row spacing (increasing planting density) and vice versa. This may be
attributed to better utilization of light, moisture and more competition within plants into
crop canopy in case of narrow spaced plants as compared to wider spaced plants. Higher
plant populations produced taller plants and more yield than lesser plant density (Beg et
al., 2007). These results are in agreement with the findings of Sedghi et al. (2008) and
Iqbal (2008), and opposite to those of Van Deynze et al. (1992). Inter-plant competition
for radiation and other aerial resources by the plants may be the reason for taller plants at
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higher plant densities (Gubbel and Dedio, 1988). The maximum existing range for
maturity and plant stature were also recorded by Johnson and Schneiter (1998) who
reported that plant height was inclined by inter hybrid antagonism.
SF-87 recorded maximum (18.57-18.14 cm) head diameter and was followed by
Hysun-33 (16.86-16.65 cm) and FH-331(16.10-15.87 cm) during both the years (Table
4.32). Variation in head size of hybrids of different genetic background was also reported
by Tunio et al. (1999), Reddy et al. (2002), Khaliq (2004) and Iqbal (2008). Narrowing
the row spacing from 75 to 45 cm resulted in 14% decrease in head diameter (Table 4.32).
Increasing row spacing from 45 to 60 cm produced 9% larger heads and a further increase
in row spacing (75 cm) improved head diameter by 4%. Beg et al. (2007) reported that
dense plantations produced lighter seeds, thinner stems, taller plants and more yield than
lesser plant density. Negative effect of increasing plant population on head diameter
recorded in the experiment under study is in agreement with findings of Ahmad and
Quresh (2000), Killi (2004) and Al-Thabat (2006). During both the years, FH-331 and
SF-187 recorded similar number of achenes per head (657 vs. 678) that was out yielded
by those of Hysun-33 with 789 achenes per head (Table 4.33). Hysun-33 recorded 16 and
20 percent higher number of achenes per head than SF-187 and HS-331, respectively.
Albeit higher head diameter of SF-187 (Table 4.33), the number of achenes per head were
more in Hysun-33 that may be attributed to better seed set in the later hybrid. Villalobos
et al. (1994) reported that response to biomass, seed number and yield to variable plant
population depended on hybrids. Several other authors (Ahmad et al. 1997, Saleem and
Malik, 2004 and Iqbal (2008) have reported such differences amongst hybrids. Widening
the rows from 45 to 75 cm, recorded 12% more achenes per head and the advantage was
only 8% when rows were widened upto 60 cm. Diepenbrock et al. (2001) reported that
increasing row spacing from 50 to 75 cm decreased number of achenes per head, but the
quantity of achenes m-2 increased significantly with decreasing row spacing. These results
suggested that number of achenes per head increased with increasing head size. Nawaz et
al. (2001) confirmed that number of achenes per head and 1000-achene weight was
greater with the plants sown in wider rows. There may be grain abortion due to
oppressive influence of shared shading at contracted row spacing and hence reduce
number of achenes per head (Andrade et al., 1993). The reciprocal association of number
of achenes per head for the planting density was recorded by Barros et al. (2004) who
observed that number of achenes per head decreased with increase in planting density.
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In field crops it is more common to look for management options where more
number of achenes is harvested per unit area. During 2006, FH-331 and SF-187 produced
similar (P≤0.05) number of achenes m-2 which was 20 and 17 percent higher than the
former hybrids, respectively (Table 4.34). The difference between FH-331 and SF-187
was non-significant during 2007. Diepenbrock et al. (2001) reported that number of
achenes per head was reduced with decreasing row spacing from 50 to 75 cm, but the
quantity of achenes m-2 increased significantly with decreasing row spacing. Narrowing
row spacing (increasing plant population) had a positive bearing on the number of
achenes m-2. Crop planted on 75 cm apart rows recorded lowest number of achenes m-2
that was improved by 19 and 45% when row spacing was narrowed down to 60 and 45
cm, respectively. Borous et al. (2004) and Calvino et al. (2004) also reported more
achenes per unit area owing to higher planting densities in sunflowers.
Weight of achenes plays a leading role in yield formation of sunflower. FH-331
produced the lightest achenes (Table 4.35) while SF-187 recorded maximum achene
weight that was 13, and 8 percent higher than that recorded for FH-331 and Hysun-33,
respectively. Although Hysun-33 produced more number of achenes per head (Table
4.33) than SF-187 but the later had higher head diameter (Table 4.30) as compared with
Hysun-33 implying better development of fewer achenes in wider head spacing in this
(SF-187) hybrid. Differential response of sunflower hybrids to 1000-achene weight was
also reported by Ahmad et al. (1997), Behrooznia et al. (1999). Khaliq (2004) and Ekin et
al. (2005) reported similar results. The maximum 1000-achene weight (57 g) was
recorded when the crop was sown at 75 cm apart row spacing. Achene weight was
reduced by 11 and 33 % when row spacing was decreased to 60 and 45 cm, respectively.
Reduction in achene weight at narrow row spacing (higher planting densities) might be
attributed to lesser nutritional area available for growth and development of the crop at
higher densities and is supported by the findings of Johnson (2003).
During 2006, Hysun-33 and SF-187 recorded highest and similar achene yield
(2856 and 2588 kg ha-1) that were 24 and 12 percent higher than that recorded for FH-331
(Table 4.36). During 2007, Hysun-33 out yielded both the hybrids by recoding 2741 kg
ha-1 achene yield that was 21% higher than achene yield of FH-331 (2256 kg ha-1) and 9%
higher than SF-187 (2519 kg ha-1). Variation in yield potential amongst hybrids under
variable environments is not uncommon; rather yields might differ even under similar
conditions. Andrade et al. (2002) reported differential response of Zenit (short season)
and Ramcull (long season) hybrids to yield. The significant differences among the
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hybrids of different maturity groups of sunflower were also reported by Khaliq (2004)
and Iqbal (2008) under same set of environmental conditions. In contrast, Tunio et al.
(1999) reported superior yield production by medium stature hybrids due to improved
reproductive development as compared to semi-dwarf varieties. The highest achene yield
of Hysun-33 is the outcome of more number of achenes per head (Table 4.33), higher
light interception (Table 4.43) by the plants as a consequence of prolonged growth
duration (Table 4.29), as well as relatively higher crop growth rate (Table4.39. Crop
planted in 45 and 60 cm apart rows recorded highest and similar achene yield during 2006
than that planted in 75 cm apart rows. However, during 2007, the wider row plantation
(75 cm) recorded as good achene yield as was recorded with 60 cm wide row plantation.
Increasing row spacing from 45 cm to 60 and 75 cm reduced achene yields by 4 and 12
percent, respectively. Jose et al. (2004) suggested that the number of achenes per head
and 1000 achene weight decreased significantly with increment in plant density, but the
number of achenes m-2 and higher mean seed weight were sufficient to compensate the
concomitant decrease. However, the studies by Zaffaroni and Schneiter (1989) gave
inconsistent results for achene yield by increasing row spacing. Diepenbrock et al. (2001)
reported that the yield was consistently higher at 75 cm rather than at 50 cm row spacing.
Harvest indices of the three hybrids in present studies did not vary to significant (P≤0.05)
extent (Table 4.38) and were in the range of 25.98 to 27.41 percent. Miralles et al. (1997)
reported non-significant differences in HIs of various sunflower hybrids, while Saleem
(2004) and Iqbal (2008) reported that HIs varied significantly amongst hybrids. Varying
row spacing also depicted non-significant (P≤0.05) differences in HIs in these studies
(Table 4.38). Steer et al. (1986) and Diepenbroke et al. (2001) reported that increasing
plant population resulted in decline in HI. This decrease might be due to more stover
yield (Table 4.37) produced in narrow row spacing (increased plant population).
Patterns of development of leaf area index (LAI) as presented in Fig.4.21a&b.
revealed that during both the years, leaf area index increased slowly in the beginning of
crop season and crop started fast accumulation of LAI at 45 days after sowing and
reached to the maximum at 75 days after sowing, and started declining thereafter. The
differences amongst the hybrids remained non-significant (P≤0.05) upto 60 days after
sowing after which the difference/s in LAIs were more pronounced. Long season hybrid
Hysun-33 exhibited highest LAI (5.10), followed by SF-187 (4.49), which was
statistically at par with FH-331 (4.32). Zaffaroni and Schneiter (1991) reported that semi
dwarf and medium stature sunflower hybrids grown at different row arrangements had
180
non-significant differences in leaf area index (LAI). Miralles et al. (1997) reported that a
longer season hybrid (SH-222) stood out for its maximum LAI and crop growth rate
(CGR) and dry matter than the other hybrids. Differential leaf area indices of hybrids
have also been reported by Saleem and Malik (2004) and Khaliq (2004). Patterns of leaf
area indices for sunflower planted with increasing population were quite opposite to that
for leaf area per plant so that LAI was always greater in plots with higher population than
that of lower planting densities (Ferreira and Abreu, 2001). An optimistic and comparable
association was observed between LAI and achene yield of sunflower (Fig. 4.20).
Periodic data at fortnight intervals (Fig. 4. 23a&b) revealed that crop growth rate
(CGR) of Hysun-33 progressively increased and achieved maximum value (21.21 g m-2 d-
1) at 75 DAS and declined sharply thereafter; reaching a value of 6.63 g m-2 d-1 at 90 DAS
during 2006. Early maturing hybrid FH-331 recorded maximum CGR (19.30 g m-2 d-1) at
60 DAS that declined slightly (16.75 g m2 d-1) at 75 DAS and reached lower level (1.85 g
m-2 d-1) at 90 DAS. Almost the same trend was exhibited by SF-187 and the maximum
(20.45 g m-2 d-1) and the minimum (3.81 g m-2 d-1) CGRs were recorded at 60 and 90
DAS, respectively. Variation in CGR of different hybrids is attributed to their different
maturity periods. The highest CGR in Hysun-33 was due to its higher leaf area index.
Miralles et al. (1997) also reported that a longer season hybrid (SH-222) had the highest
CGR which was the consequence of its higher leaf area index. Crop planted at 45 cm
apart rows showed maximum CGR throughout the growing season as compared to plants
grown at 60 and 75 cm apart rows for both the years.(Fig.4. 24a&b). Widening the row
spacing (decreasing plant population) resulted in decrease in mean seasonal crop growth
rate during both the years (Table 4.39). Seasonal crop growth rate was decreased by 8%
when row distance was increased from 45 cm to 60 and declined further up to 24% at 75
cm apart rows of sunflowers. Decreasing crop growth rates at wider row spacing might be
attributed to lesser dry matter accumulation per unit area by low plant populations at such
row spacing. Seasonal net assimilation rate (NAR) differed significantly (P≤0.05) for
different hybrids (Table 4.40). Maximum and similar NAR were observed for Hysun-33
and SF-187 (4.98 vs. 4.88 g m-2 d-1) as compared with FH-187 (4.47 g m-2 d-1) during
both the years. Zaffaroni and Schneiter (1991) reported that semi dwarf and medium
stature sunflower hybrids grown at different row arrangements had non-significant
differences net assimilation rate (NAR). Maximum mean NAR (5.00 g m-2 d-1) was
recorded when the crop was grown at row spacing of 45 cm and it was 10% higher than
that recorded for crop planted in 75 cm apart rows. The three hybrids sown at varying row
181
spacing exhibited similar (P≤0.05) responses in terms of mean net assimilation rate
(Table4.40).
All hybrids accumulated total dry matter (TDM) to similar extent until 45 days
after sowing after which the differences became significant (P≤0.05) till harvest (Fig
4.26). Hysun-33, SF-187 and FH-331 produced 1004, 890 and 783 g m-2 TDM during
2006 and the corresponding values for the year 2007 were 909,807 and 719 g m-2 (Table
4.41). Hysun-33 recorded 12% more TDM than SF187 which, in turn was 27% higher
than that observed for FH-331. The higher TDM production by Hysun-33 may be
attributed to its higher plant height as compared with rest of the hybrids (Table4.41).
Lower biomass production by the short duration hybrid (FH-331) might be due to low
quantity of radiation potentially available over the crop growth duration. Miralles et al.
(1997), Angadi and Entz (2001) and Khaliq (2004) also recorded significant differences
for TDM production by hybrids of different stature. Fereres et al. (1986) and Schneiter
(1992) attributed the differences for production of TDM by different genotypes to crop
duration and maturity ranking of sunflower. The differences among the hybrids in TDM
yields in these studies were outcome of the shortened crop duration. Values of total
biomass recorded in present studies were similar to other reports (Anderson et al., 1985;
Connor et al., 1985 and Khaliq, 2004).
Leaf area duration (LAD) accounts for differences in yield in response to different
treatments. At any particular moment e.g. pace of establishment, extent and rate of
regression, all the settings of photosynthesizing system are taken into account by LAD
(Miralles et al., 1997). Hysun-33 showed maximum (205.54 d) LAD that was 3 and 10 %
higher than that observed for SF-187 and FH-331, respectively (Table 4.42). Hysun-33
stood out for its maximum LAD due to the highest maximum LAI (Fig.4.21), which also
coincides with the highest values of TDM (Table 4.41 ). Miralles et al. (1997) and Khaliq
(2004) also recorded similar results for LAD of sunflower hybrids of varying maturity
and morphophysiological traits. Maximum LAD was recorded when the crop was sown at
45 cm apart rows and progressively decreased with widening row spacing (Table4.42).
On an average, LAD decreased by 4 and 11 percent when row spacing was increased
from 45 to 60 and 75 cm, respectively. This decrease in LAD for the sunflower crop sown
in wider rows (low planting density) might be attributed to relatively lower LAIs (leaf
area per unit of land area). Khaliq (2004) reported similar ranges of LADs for sunflowers
grown under similar set of environmental conditions.
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Leaf area index and canopy architecture determine the extent to which a crop can
intercept photosynthetically active radiation which, in turn is instrumental in determining
crop biomass accumulation and its partitioning within the plant (Van der Werf, 1996).
Hysun-33 recorded highest values for accumulated radiation interception (517.6-
527.7 MJ m-2) and was followed by SF-187 (505.3-5138 MJ m-2). Dosio et al. (2000)
reported variation in photosynthetically active radiation intercepted by two genetically
different hybrids (Dekalb and NKT). Calvino et al. (2004) also recorded that light
interception and yield of sunflower were subjected to cultivar features including time to
maturity and plant stature and concluded that short season hybrid (Zenit) consistently
intercepted less radiation than long season hybrid (Sucrofer). Khaliq (2004) and Iqbal
(2008) reported similar findings for radiation interception by hybrids of varying maturity
under similar environmental conditions.
Row spacing and planting density may be used as a management tool to optimize
the time required for a crop to fully intercept available light (Ball et al., 2000). Maximum
radiation interception (527 MJ m-2) was the outcome of sunflower planted at 45 row
spacing and it was 4.75% higher of the crop grown at 75 cm row distance (Table 4.45).
Andrade et al. (2002) also recorded an increase in light interception by the sunflower crop