effect of blended nps fertilizer rates on yield, yield

EFFECT OF BLENDED NPS FERTILIZER RATES ON YIELD, YIELD

RELATED TRAITS AND TUBER QUALITY OF POTATO (Solanum

tuberosum L.) VARIETIES AT HARAMAYA, EASTERN ETHIOPIA

MSc THESIS

ABRAHAM GUDETA

JUNE 2019

HARAMAYA UNIVERSITY, HARAMAYA

2

Effect of Blended NPS Fertilizer Rates on Yield, Yield Related Traits and

Tuber Quality of Potato (Solanum tuberosum L.) Varieties at Haramaya,

eastern Ethiopia

A Thesis Submitted to Postgraduate Program Directorate

(School of Plant Science)

HARAMAYA UNIVERSITY

In Partial Fulfillment of the Requirements for the Degree of

MASTER OF SCIENCE IN AGRICULTURE

(HORTICULTURE)

Abraham Gudeta

June 2019

Haramaya University, Haramaya

3

POSTGRADUATE PROGRAM DIRECTORATE

HARAMAYA UNIVERSITY

We hereby certify that we have read and evaluated this thesis entitled “Effect of Blended NPS

Fertilizer Rates on Yield, Yield Related Traits and Tuber Quality of Potato (Solanum

tuberosum L.) Varieties at Haramaya, eastern Ethiopia” prepared under our guidance by

Abraham Gudeta. We recommend that the thesis be accepted as fulfilling the thesis

requirement.

Wassu Mohammed (PhD)

Major-Advisor

Signature

Date

Prof. Nigussie Dechassa (PhD)

Co-Advisor

Signature

Date

As members of the Board of Examiners of the M.Sc. thesis open defense examination of

Abraham Gudeta, we certify that we have read and evaluated the thesis and examined the

candidate. We recommend that the thesis be accepted as it fulfills the requirements for the award

of the Degree of Master of Science in Agriculture (Horticulture).

Chairperson

Signature

Date

Internal Examiner

Signature

Date

External Examiner

Signature

Date

Final approval and acceptance of the thesis is contingent upon submission of a final copy of the

thesis to the Council of Graduate Studies (CGS) through the School Graduate Committee (SGC)

of the candidate’s major school.

4

DEDICATION

This thesis dedicated to my father Gudeta Dida, my mother Joro Nagawo and all my brothers

and sisters for the all-rounded and unconditional support rendered to me for the betterment of my

life.

5

STATEMENT OF THE AUTHOR

First, I declare that this thesis is my bonafide work and all sources of materials used for this

thesis have been duly acknowledged. This thesis has been submitted in partial fulfillment of the

requirements for M.Sc. degree at the Haramaya University and is deposited at the University

Library to be made available to borrowers under rules of the library. I declare that this thesis is

not submitted to any other institution anywhere for the award of any academic degree, diploma,

or certificate.

Brief quotations from this thesis are allowable without special permission provided that an

accurate acknowledgement of the source is made. Requests for permission for extended

quotation from or reproduction of this manuscript in whole or in part may be granted by the

Head of the Department of Plant Sciences or the Dean of the School of Graduate Studies when

the proposed use of material is in the interests of scholarship. In all other instances, however,

permission must be obtained from the author.

Name: Abraham Gudeta

Signature:

Date of submission:

School: School of Plant science

6

BIOGRAPHICAL SKETCH

The author, Abraham Gudeta Dida, was born in Dagam Woreda, Ali doro Keble, North Shoa

Zone of Oromia Regional State in Ethiopia in 1994 G.C. He attended elementary school

education at Seyoum Demisew and high school and preparatory at Gerba Guracha. In 20014

G.C, he joined Mizan-Tepi University and graduated with the Degree of Bachelor of Science in

Horticulture in July 2016 G.C. After graduation, he was employed Mizan-Tepi University as

graduate assistance. Then after one year he joined the School of Graduate Studies Haramaya

University in 2018 G.C to pursue a study leading to the Degree of Master of Science in

Agriculture (Horticulture).

7

ACKNOWLEDGMENTS

First and foremost, I would like to praise and glorify the supreme my family, next to Almighty

God for providing me with the strength and patience that I required to complete the study.

I would also like to express my deepest and heartfelt thanks as well as my most sincere

appreciation and gratitude to my major advisor Dr. Wassu Mohammed and my co-adviser Prof.

Nigussie Dechassa for their keen interest, dedicated and meticulous supervision, for amicably

motivating and scientifically supporting me during the whole period of the study. I also thank

them for genuinely and constructively criticizing my work from the time of inception of the

research work up to its completion and thesis write-up. The visits they made to my research field

on a number of occasions and the scientific discussions I held with them in the research

undertaking were exemplary and worthy of deepest gratitude.

I also remain thankful to all the enumerators who assisted me in data collection with patience,

commitment and dedication. Their cooperation was not on the basis of their material benefit but

is really their own commitment to help me. I am grateful to farm management of Raare site, who

responded to all questions with patience and gave necessary information for this research work. I

would like also to thank for providing me with all the relevant secondary information. Finally I

thank Haramaya University institution, Technical assistance of Horticulture staff for they support

me through their effort.

8

LIST OF ACRONYMS AND ABBREVIATIONS

ECSA Ethiopia Central Statistical Agency

FAO Food and Agriculture Organization

FAOSTAT Food and Agriculture Organization Corporate statistical Database

MoA Ministry of Agriculture

NGO Non-Governmental Organization

PH Power of Hydrogen

SAS Statistical Analysis Software

CIMMYT Centro International de major amento de maize Y Trigo

EIAR Ethiopian Institute of Agriculture Research

Ethio SIS Ethiopian soil information system

IAR Institute of Agricultural Research

LSD Least significant difference

CV Coefficient of Variation

ANOVA Analysis of Variance

MRR Marginal Rate of Return

ETB Ethiopian Birr

NPS Nitrogen, phosphorus and Sulfur

9

TABLE OF CONTENTS

STATEMENT OF THE AUTHOR v

BIOGRAPHICAL SKETCH 5i

ACKNOWLEDGMENTS 7

LIST OF ACRONYMS AND ABBREVIATIONS 8

LIST OF TABLES

11

LIST OF TABLES IN THE APPENDIX xii

ABSTRACT xiii

1. INTRODUCTION

14

2. LITRATURE REVIEW

17

2.1. Botany, Origion and Distribution of potato 17

2.2. Utilization and Economic Importance of Potato 17

2.3. Ecology and Major Production Areas of Potato in Ethiopia 19

2.4. Cultural Requirements 20

2.5. Role of Nitrogen Fertilizer in Potato Productivity and its Nutrition 21

2.6. Role of Phosphorus Fertilizer in Potato Productivity and its Nutrition 22

2.7. Effect of Nitrogen on Crop Phenology Parameters 23

2.8. Effect of Nitrogen and Phosphorus on Potato growth Parameters 24

2.8.1. Number of Main stems 11

2.8.2. Plant Height 11

2.9. Yield Components of Potato and Their Response to NP Fertilizers 25

2.9.1. Tuber Number per hill 26

2.9.2.Tuber Weight and Tuber Size Distribution 27

2.10. Tuber Quality Parameters 27

2.10.1. Specific Gravity 27

10

2.10.2. Dry Matter Content 28

2.11. Importance of sulphur in Combination with other Nutrients 29

2.12. Effect of Sulphur on Yield and Quality of Potato 31

TABLE CONTENTS (Continued)

3. MATERIALS AND METHODS 33

3.1. Description of the Study Site 33

3.2. Description of Experimental Materials 33

3.3. Treatments and Experimental Design 34

3.6.1. Phenology and Growth Parameters 37

3.6.2. Yield Components and Tuber Yield 37

3.6.3. Tuber Quality Related Traits 38

3.8. Data Analysis 40

4. RESULTS AND DISCUSSION 41

4.1. Soil Physico-chemical Properties of the Experimental Site 41

4. 2. Phenology and Growth of potato 42

4.2. 1. Phenology 42

4.2. 2. Growth Traits 35

4.3. Yield Components and Tuber Yield 48

4.3.1. Average Tuber Number and Weight 48

4.3.2. Distribution of Tubers in Different Size Categories 38

4.3.3. Marketable, Unmarketable and Total Tuber Yield 51

4.4. Tuber Quality Related Traits 54

4.5. Partial Budget Analysis 54

5. SUMARRY AND CONCLUSION 59

6. REFERENCE 61

7. APPENDICES 71

11

LIST OF TABLES

Table Page

1 Amount of mineral nutrient contents in seven rates of blended NPS fertilizer set

as combination of treatments

35

2 Selected soil phsico-chemical properties of the experimental site 42

3 Effect of potato variety on days to 50% emergency and maturity at Haramaya

during 2018 cropping season

43

4 Effect of blended NPS fertilizer on days to 50% maturity of potato varieties at

Haramaya during 2018 cropping season

44

5 Interaction effect of blended NPS fertilizer and variety on days to 50 %

flowering of potato at Haramaya during 2018 cropping season

45

6 Effect of variety on growth of potato at Haramaya during 2018 cropping season 46

7 Effect of blended NPS fertilizer on plant height of potato varieties at Haramaya

during 2018 cropping season

47

8 Interaction effect of blended NPS fertilizer and variety on average tuber number

and tuber weight of potato varieties at Haramaya during 2018 cropping season

48

9 Interaction effect of blended NPS fertilizer and variety on large tuber size and

medium size proportion (%) at Haramaya during 2018 cropping season

51

10 Main effect of blended NPS fertilizer and variety on marketable and total tuber

yield at Haramaya during 2018 cropping season

53

11 Interaction effect of blended NPS fertilizer and variety on unmarketable tuber

yield at Haramaya during 2018 cropping season

54

12 Table 12. Percent advantage of marketable tuber yield due to blended NPS

fertilizer over potato production without fertilizer at Haramaya in 2018

55

13 Partial budget analysis of seven rates of blended NPS fertilizer rates in

combination with three potato varieties in Haramaya 2018

46

12

LIST OF TABLES IN THE APPENDIX

Table Page

1 Mean squares from analysis of variance for phenology, growth, yield

components, tuber yield and tuber quality related traits of three potato varieties

as influenced by rates of blended NPS fertilizer at Haramaya in 2018

82

2 Mean values of traits due to potato varieties and rates of NPS fertilizer at

Haramaya in 2018

83

3 Mean marketable total tuber yields of potato due to interaction of varieties and

rates of blended NPS fertilizer at Haramaya in 2018

83

13

Effect of Blended NPS Fertilizer Rates on Yield, Yield Related Traits and

Tuber Quality of Potato (Solanum tuberosum L.) Varieties at Haramaya,

eastern Ethiopia

ABSTRACT

Potato (Solanum tuberosum L.) is an important food and export crop in East Hararghe. The

limiting macro and micronutrients were identified for the production of crops in Haramaya

districts, but the rates of these nutrients for high potato yield are not yet determined. Therefore,

this research was conducted to determine the effect of blended NPS fertilizer rates on yield

related, yield and tuber quality traits of potato varieties, and to estimate economically feasible

blended NPS fertilizer rate for potato production at Haramaya, East Hararghe. The experiment

was conducted as factorial combination of seven rates of blended NPS fertilizer (0, 50, 100, 150,

200, 250,300 kg ha-1) and three potato varieties (Bubu, Belete, and Shangi) in a Randomized

Complete Block Design with three replications. The results revealed that variety and blended

NPS fertilizer had significant effect on crop phenology, growth, tuber yield and yield components

except proportion of medium size tubers not influenced by the two main factors and blended NPS

fertilizer had nonsignificant effect on days to 50% emergence, number of main stem/hill and

proportion of large size tubers. Neither the two main factors (variety and blended NPS fertilizer)

nor their interaction influenced tuber quality related traits. Variety and blended NPS fertilizer

interacted to influence days to 50% flowering, average tuber weight (g), average tuber number,

unmarketable tuber yield, and proportion of small, medium and large size tubers. The highest

marketable tuber yield (30.74 t ha-1) and total tuber yield (32.16 t ha-1) was obtained by the

application of NPS fertilizer at the rate of 300 kg ha-1 which was followed by the application of

250 kg ha-1. Bubu (29.52 t ha-1) and Belete (29.48 t ha-1) produced significantly higher

marketable tuber yield than Shangi variety. The net benefit obtained from Bubu and Belete

varieties was determined by about 72.06 (R2=0.07206) and 81.92% (R2=0.08192), respectively,

and the relationship between rates of NPS fertilizer and the net benefit obtained from potato

production was linear and significant. The highest MRR (marginal rate of return) of 1802.35%

was also obtained from Bubu variety with the application of 50 kg ha-1 NPS fertilizer. However,

the highest net benefit of 166175.5 obtained from Bubu followed by 158899 Birr ha-1 from Belete

varieties with the acceptable MRR of 1434.17 and 760.27%, respectively, due to the application

of highest NPS fertilizer rate of 300 kg ha-1. Therefore, growing of the two varieties at highest

rates of NPS fertilizer could be recommend for producers because of the high economic returns.

Keywords: Crop phenology, Marginal rate of return, Net benefit, Proportion of large, medium

and small size tubers.

14

1. INTRODUCTION

Potato (Solanum tuberosum L.) is consumed worldwide and it one of the most important cold

season vegetables. It is considered as inexpensive and nutritive food security crop, as it produces

more dry matter, protein and calories per unit area and time than the major cereal crops (Rai and

Yadav, 2005). Globally, potato is the third most important food crop in terms of consumption

after rice and wheat (Hielke et al., 2011; Birch et al., 2012; Hancock et al., 2014). The annual

world potato production is estimated to 376 million tons in 2013 (FAOSTAT, 2015). The global

annual production is about 381.7 million tons (FAOSTAT, 2017). In 2013, the Africa’s potato

production reached over 30 million tons (FAOSTAT, 2015).The production of potato in Ethiopia

is in increasing trend where it is concentrated mostly in mid altitudes and highlands of the

country. Potato ranks first among root and tuber crops in Ethiopia both in volume of production

and consumption followed by cassava, sweet potato and yam where smallholder farmers are the

major producers as food, and cash crop (CSA, 2016).

Northwest, Central, Eastern, South Eastern and Southern areas are the dominant potato

production areas in the country. Potato production has shown a spectacular increase during the

past one and a half decades in area of production from 0.16 to 0.3 million hectare, volume of

production from 974 000 thousands MT to over 3 660 000 million MT, and number of growing

households from 1.8 million to over 5 million households (EIAR, 2016). Oromia National

Regional State is a leading producer where potato is used as co-staple food in some zones, such

as East Hararghe (ORARI, 2007). East Hararghe, potato is grown by 52,710 farmers with a total

area of 2,507.12 hectares in 2013/2014 Meher season. The average yield is about 19.3 t ha-1 in

East Hararghe (CSA, 2013).which is by far higher than national average yield of 12.66 t ha-1 in

2015 (CSA, 2017).but not reach to the crop potential (40 t ha-1) at research centres. In Hararghe,

potato is the second most advantageous crop next to khat (Chata edulis) in supporting farmers’

welfare with 759% increase in income over sorghum (Mulatu et al., 2006). Compared to the

other areas of potato production, this area is characterized by export market oriented production

particularly to Djibouti and Somalia (Mulatu et al., 2005; Hirpa et al., 2010).

15

In eastern Ethiopia, potato is not only grown during main cropping season (June to October) but

also it is grown under irrigation in the dry season (December to April) because of low disease

pressure and relatively high prices and in the belg (February to May) season (Eshetu et al,

2007b). Most farmers grow the cultivars with short tuber dormancy period such as Batte, Jarso,

and Dedefa, though considerable numbers of farmers are producing improved varieties.

However, farmers’ cultivars are susceptible to late blight [Phytophthora infestans (Mont.) de

Bary] resistant (Wassu, 2014) and only used for the production under irrigation and belg season

where the disease pressure is low (Dendena, 2013). Therefore, the use of resistant varieties

during meher season is indispensible to obtain high potato yield. Moreover, the introduction of

varieties having short tuber dormancy period and resistant tolerate blight in the region is more

advantageous since the farmers could produce potato throughout the year from farm saved seed

tubers. In this regard, the effort made by Haramaya University to introduce Shangi variety

(resistant to late blight and sprouting of tubers not required more than a month) may favor

farmers of eastern Ethiopia. The variety is under adaptation and yield evaluation process (Potato

Research Program of Haramaya University).

Soil fertility status and management are among other factors that limit the yield potential of

various crops including potato (Benepal, 1967). Potato is naturally a heavy feeder crop. Potato

has high phosphorus requirement for optimum growth and yield; thus, when grown on

phosphorus deficient soils, considerable yield losses are apparent (Dechasa et al., 2003)

Unfortunately, phosphorus is one of the least accessible nutrients in most soil especially under

tropical conditions where low phosphorus availability is a big challenge to agricultural

production (Kochiannet et al.,2004). Nitrogen is another essential element for plant growth and

yield that different cultivars have different rates of nitrogen requirement for maximum tuber

yields (Molerhagen, 1993). Berga et al., 1994) recommended 165/90 N/P2O5 ha-1 as feasible rate

for the central Shewa, and this recommendation has been used as blanket recommendation

throughout the country. In the same way, 146/138 N/P2O5 ha-1 was recommended as economic

and agronomic rate of fertilizer for the highlands of Hararghe (Teriessa,1995).These

recommendations may not work for the current market, soil fertility status, and other climatic

variables.

16

The sources of plant nutrients for Ethiopian agriculture over the past five decades have been

limited to Urea and Diammonium Phosphate (DAP) fertilizers which contain only nitrogen and

phosphorus. Shiferaw, (2014) reported that Ethiopian soils lack most of the macro and

micronutrients that are required to sustain optimal growth and development of crops. The soils in

East Hararghe area were identified deficient not only nitrogen and phosphorus but also sulfur

(ATA, 2014). This indicates that the application of nitrogen and phosphorus do not satisfy the

nutrient requirements of the crops including potato. It has been also reported that the fertilizer

rates used in Ethiopia are below international and regional standards (AGP, 2013). To avert the

situation the Ministry of Agriculture of Ethiopia has been recently introduced a new

blended NPS fertilizer containing nitrogen, phosphorous and sulfur with the ratio of 19% N, 38%

P2O5 and 7% S. This fertilizer is used as a substitute of DAP in crop production system as main

source of phosphorous (MoANR, 2013).

In East Hararghe, particularly at Haramaya, studies on the response of varied potato varieties to

nitrogen and phosphorous containing fertilizers have been conducted. However, the effect of

blended NPS fertilizer on tuber yield and yield related traits of potato varieties resistant to late

blight has not been studied. Moreover, the tuber yield of Shangi variety at varied rates of blended

NPS fertilizer has not been determined. Therefore, it is necessary to conduct research in the area

to assess the response of potato varieties to the newly introduced blended fertilizers and to

identify rate of this fertilizer to obtain both high tuber yield and profit from the production of

potato. This is because, fertilizer requirement of crops varies across locations and economically

feasible fertilizer rate also varies with soil type, fertility status, moisture amount, other climatic

variables, variety, crop rotation, and crop management practices (Zelalem et al., 2009).This

research is therefore, initiated to achieve the following objectives:

o to assess effect of blended NPS fertilizer rate on yield, yield related traits and tuber

quality of potato varieties; and

o to estimate the cost-benefit of blended NPS fertilizer rates for potato production.

17

2. LITRATURE REVIEW

2.1. Botany, Origion and Distribution of potato

Potatoes are a member of the Solanaceae family. Contrary to popular belief the potato is not a

storage root, but rather a specialized underground stem. Potato (Solanum tuberosum L.) plants

produce rhizomes (often called stolon) that have rudimentary leaves and are typically hooked

at the tip. They originate from the basal stem nodes, typically below ground, with up to three

rhizomes per node (Struik, 2007). Tubers, spherical to ovoid in shape, are swellings of the

rhizome. The flesh of the tubers varies in color from white to yellow to blue and the skin varies

from white through yellow to tan and from red through blue. The color of the flesh may or may

not correspond to the color of the skin. The texture of the surface may vary from smooth to net or

russetted (Spooner and Salas, 2006). On the surface of the tuber are auxiliary buds with scars of

scale leaves that are called eyes (Struik, 2007). When tubers are planted, the eyes develop into

stems to form the next vegetative generation

The Potato has its origin in the high lands of South America and was first cultivated in the

Andes in the vicinity of Lake Titicaca near the present border of Peru and Bolivia (Horton,

1987). From Europe, Solanum tuberosum was transported to North America. Solanum tuberosum

may first have been transported from England to Bermuda in 1613 and then from Bermuda to the

North American mainland in 1621, a hypothesis favored by Laufer, (1938) and Hawkes, (1990).

S. tuberosum was present in India by 1610 and mainland China by 1700 (Sauer, 1993). S.

tuberosum was taken to New Zealand in 1769 by Captain Cook and gained agronomic

significance for the native Maori by 1840 (Sauer 1993). Missionaries may have played a crucial

role in the distribution of S. tuberosum from Europe throughout the world (Laufer 1938; Sauer

1993). It was introduced to Ethiopia in 1858 by the German Botanist, Schimper (Pankhurst,

1964).

18

2.2. Utilization and Economic Importance of Potato

Potato (Solonaum tuberosum L.) is the most important food crop, after cereals, in human diet

in developed as well as in developing countries (Wheeler, 2009; Kushwaha et al., 2014). It

exceeds wheat (Triticum aestivum L), rice (Oriza sativa L.) and corn (Zea mays L.) in the

production of dry matter and protein per unit of area (Romero-Lima et al., 2000). It is grown

in about 140 countries, more than 100 of which are located in the tropical and sub-tropical region

(Beukema and Van der Zaag, 1990). The nutritional value of potato tubers is a key factor for its

progressive production, along with the economic benefits that potato cultivation can bring to

developing countries (Van Gijessel, 2005; McGregor, 2007).

The relatively high carbohydrate (82%) and low fat content (less than 1%) of the potato makes

it an excellent energy source for human consumption (WPC, 2003). Moreover, the potato crop

provides more nutritious food per unit land area, in less time, and often under more adverse

conditions than other food crops (Yigzaw et al., 2008; Hirpa et al., 2010). It is said to be one of

the most efficient crops in converting natural resources, labor and capital into a high quality food

with wide consumer acceptance; hence the Ethiopian government has identified as one of the

priority crops of the agricultural growth programmed (EIAR, 2003; Tesfaye et al., 2010).

In Ethiopia, the majority of potatoes produced are used for preparation of different kinds of

traditional foods. Although, there are some food processing industries in the country, none of

them are involved in the processing of potatoes. Moreover, consumption of potato chips is not

common in the country except in the big hotels and restaurants. Small scale potato chips

processors are flourishing in cities and big towns (Elfinesh, 2008). It is a very important food

and cash crop in Ethiopia, especially in the high and mid altitude areas. It has a promising

prospect in improving the quality of the basic diet in both rural and urban areas of the country.

As a food crop, it has a great potential to supply high quality food within a relatively short

period and is one of the cheapest sources of energy. Moreover, the protein from potato is of

good composition with regard to essential amino acids in human nutrition. Potato also has

substantial amounts of vitamins, minerals and trace elements. Such a crop undoubtedly is very

important for countries like Ethiopia, where inadequate protein and supplies of calories are the

apparent nutritional problems (Berga et al., 1994). Furthermore, the production period is about

19

90 days, enabling optimum use of the available agricultural land (Solomon, 1985).

2.3. Ecology and Major Production Areas of Potato in Ethiopia

The natural environment in Ethiopia is very suitable for year round production of potato using

rain-fed and irrigated systems. The main production season for potato in Ethiopia in areas with

altitude higher than 2500 m runs from June to September while the off-season slot starts in April

and ends in August. The altitude between 1800 and 2200 m is suitable for growing seed and table

potatoes in Ethiopia and 70% of the agricultural land is located at that elevation (Bezabih and

Mengistu, 2011).The favorable climate at higher elevations, fertile soils and availability of

irrigation in many areas such as the South-Central Rift Valley provide suitable conditions for

potato (Haverkort et al., 2012; and Asrat, 2014).

Potato (Solanum tuberosum L.) is a weather sensitive crop with a wide variation among cultivars.

It is a crop of temperate climate and it is moderately tolerant to frost (Rezaul Karim et al., 2011).

Potato grows well and produces yields at an altitude of over 1000 metres above sea level,

although some produced cultivars perform well at low elevations ranging from 400 to 2000

metres above sea level in tropical highlands (Levy and Veilleux, 2007). In Ethiopia, the altitude

between 1800 to 2500 metres above sea level is regarded as suitable for seed and ware potatoes

growth (Bezabih and Mengistu, 2011). The highland areas of Ethiopia (defined as land above

1,500 masl) where the potato is generally well suited, cover 44 percent of the nation's area, but

include 88 percent of its population and 95 percent of its cropped area (Grepperud 1996).

There are five major potato production regions in Ethiopia: Central Ethiopia, Eastern Hararghe,

North West Ethiopia, South Ethiopia and Western Ethiopia (Kassa and Beyene, 2001). Which to

gether constitute approximately 83% of the potato farmers in the country (CSA, 2009). The

Eastern area of potato production in Ethiopia mainly covers the Eastern highlands, especially

East Hararghe zone (CSA, 2009). The most important feature of potato production in this region

is that the potatoes produced are market oriented with considerable amounts being exported to

20

Djibouti and Somalia (Adane et al., 2010). In this region, potato is mainly grown under irrigation

in the dry season (December to April) because of low disease pressure and relatively high prices.

The crop is also produced in the belg (February to May) season and the meher (June to October)

seasons (Eshetu et al., 2005b).

Potato is one of the tuber crops growing in Ethiopia. It is grown by approximately 1,197,018

farmers (CSA, 2017). Among African countries, Ethiopia has possibly the greatest potential for

potato production (Firew et al., 2016). At present, potatoes are still widely regarded as a

secondary crop, and annual per capita consumption is estimated at 5 kg. The production of potato

is expanding at a faster rate than other food crops in developing countries, including Ethiopia.

The crop has also proved that it has great potential for adaptation to the diverse growing

conditions of the tropics where the majority of the developing countries are located. According

to CSA, (2017) report potato production area in Ethiopia decreased from 70131.32 ha in 2016 to

66,923.33ha in 2017, but average potato yield ton ha-1 increased in 2017, from 13.5 ton/ha in

2016 to 13.8 ton/ha in 2017.

2.4. Cultural Requirements

Potatoes grow well at a higher soil pH, but scab can be a problem. If it is not practical to

maintain a low pH, scab resistant cultivars must be grown. A well-drained fertile soil with a pH

of 5.5 to 6.5 is necessary. The rate of Nitrogen fertilization is a key consideration in managing

fertility, because excessive applications delay maturity and reduce the partitioning of dry matter

to the tubers, not to mention possible adverse effects on processing quality and on the

environment (Ewing, 1997).

Seed tubers that are plant too deep will be slow to emerge and may be more subject to attack

by various diseases. Very shallow planting of seed tubers may result in inadequate soil moisture

around the seed piece and in production of tubers so close to the soil surface that greening caused

by exposure to light is more of a problem. Planting should be deeper on lighter soils than on

heavy ones. Many growers like to plant seed tubers relatively deep but then cover them with only

a shallow layer of soil. More soil covering will then be added as the plant develops. A good rule

21

of thumb is never to have more than 10 cm of soil above the tip of the developing sprout

(Ngungi, 1982).

Soils should be ridged up along the potato row to provide extra cover for the developing tubers.

This tends to reduce the number of tubers that stick out of the soil and are exposed to light. Even

diffuse light filtering down through the cracks in the soil will cause tubers to turn green and to

develop a bitter flavor. Tubers that turn green in the field are called sun burned and are unfit for

consumption. Secondary benefits of ridging up the soil are that it facilitates harvest and provides

weed control (Thompson and Kelly, 1983).

Generally cultural practices are the first line of defense against potato disease like late blight of

potato. Before planting, growers should take several measures to control late blight. Shifting

planting date of potato is important component in the control of late blight that has received little

attention in Ethiopia. (Bekele and Gebremedhin, 2000).Genetic resistance is one of the best

options for managing disease in potato. There are several potato cultivars with measurable levels

of resistance to late blight that are now part of production systems in different parts of the world.

Nonetheless many susceptible cultivars are still being grown and there are cultural and economic

factors that can restrict adoption of new, resistant ones (Walker et al., 1999).

Bacterial wilt caused by (Ralstonia solanacearum) is also regarded as an important disease

contributing to yield reduction (Mureithi, 2000; Otipa et al., 2003; Kaguongo et al., 2008). It

is considered more problematic than late blight since it has no known chemical control

procedures and many farmers do not know how to control it. While it could be controlled

through crop rotation, however, this is not feasible due to small farm sizes which hinder effective

rotation programmes. The disease has been reported to cause losses ranging between 30-70% at

altitudes ranging 1800-2800 m (Otipa et al., 2003).

2.5. Role of Nitrogen Fertilizer in Potato Productivity and its Nutrition

Nitrogen is the most limiting nutrient in crop production and is higher in concentration than all

other mineral nutrients in most plants (Foth and Ellis, 1996). It makes up 1 to 4 percent of dry

matter of the plant. Nitrogen is taken up from the soil in the form of nitrate (NO3-1) or

ammonium (NH4+). In the plant N combines with compounds produced by carbohydrate

22

metabolism to form amino acids and proteins. Being the essential constituent of proteins, it is

involved in all the major processes of plant development and yield formation. A good supply of

nitrogen stimulates root growth and development as well as the uptake of other nutrients (Brady

and Weil, 2002). Plants obtain readily available N forms from different sources. Potato at the

beginning of its growth requires a lot of available nitrogen. Nitrogen is needed to take up carbon.

Sufficient nitrogen increases both plant growth and leaf surface and tuber size and causes crop to

become tolerant to leaf blot disease (Hassanpanah et al., 2009). Potato is sensitive both to N

deficiencies and excesses. Effective fertility management is critical to profitable production of

potatoes. The crop is highly responsive to N fertilizer, but N fertilizer use efficiency is low

(Rourke, 1985; Porter and Sisson, 1991).

Optimum use of N by plant decreases leaching of nitrogen and improves tuber germination and

steady leaf area. Excess nitrogen at the last stage of growth causes development of stem and

leaves instead of tubers as a result of high amounts of amino acids and amides, not changing to

protein. Excess nitrogen has negative effect on tuber yield and quality; deficiency the

photosynthesis decreases because lower leaves of plant become yellow and falls (Hassanpanah et

al., 2009). According to Hopkins et al. (2008) also reported that Potatoes require a steady supply

of nutrients. Deficiencies or fluctuations of soluble nutrients (especially N) cause poor vine

health, increased pathogen and insect susceptibility, reduced tuber yields, and diminished tuber

quality. Potatoes require high amounts of fertilizer not only because of high nutrient demand, but

also because they have a shallow, inefficient rooting system to explore soil nutrient from wider

surface area.

2.6. Role of Phosphorus Fertilizer in Potato Productivity and its Nutrition

Phosphorus is claimed to be the second most often limiting plant nutrient (Tisdale et al., 1995). It

is an essential component of deoxyribonucleic acid (DNA), the seat of genetic inheritance, and of

ribonucleic acid (RNA), which directs protein synthesis in both plants and animals.

Phospholipids, which play critical roles in cellular membranes, are another class of universally

important phosphorus-containing compounds. For most plant species, the total P content of

healthy leaf tissue is not high, usually comprising only 0.2 to 0.4% of the dry matter (Brady and

Weil, 2002). Plants absorb phosphorus in the form of HPO4-2 and H2PO4 (Tisdale et al., 1995).

23

The physical and chemical properties of soils influence the solubility of phosphorus and its

absorption reactions in soils. These include the nature and amount of soil minerals, soil pH,

cations effect and anion effect, extent of phosphorus saturation, reaction time and temperature,

flooding and fertilizer management (Tisdale et al., 1995). Moreover, availability of phosphorus

from fertilizers may be affected by the soil reaction, the degree of soil phosphorus deficiency,

rate and method of application, needs of the specific crops, certain soil differences. The

maximum availability of phosphorus for plant utilization is known to occur at soil pH between

6.5 and 7.5 (Mengel and Kirkby, 1987).

Phosphorus deficiency is one of the largest constraints to crop production in many tropical soils,

owing to low native content and high P fixation capacity of the soil (Barber, 1995; Fairhust et al.,

1999). P is essential for root development and when the availability is limited, plant growth is

usually reduced. The movement of P in soils is very low and its uptake generally depends on the

concentration gradient and diffusion in the soil near to roots (Marschner, 1995). Biswas, and

Mukherjee, (1993); Miller and Donahue, (1995) and Tisdale et al. (1995) have reported that the

use of P fertilizer becomes imperative because the concentration of P in many soils is very low

and it is also liable to different chemical reactions that make it unavailable to plants. Plants

supplied with adequate amount of P were reported to form good root system, strong stem, mature

early and give high yield whereas plants grown on P deficient soils showed stunted growth, low

shoot to root ratio, poor fruit and seed formation, purpled colored leaves with reddish coloration

of the stem. Biochemically, deficiency causes changes in functions of the plant including

accumulation of sucrose and reducing sugars and sometimes of starch (Rending and Taylor,

1989).

2.7. Effect of Nitrogen on Crop Phenology Parameters

2.7.1. Days to Emergency, Flowering, and Maturity

The variation in emergence among the varieties may be attributed to the phenomenon that days

to emergence are mainly influenced by the physiological age of the tubers, which is a varietal

characteristic, but not by external supply of nutrients such as nitrogen. Mulubrhan (2004) who

stated that emergence depends on the soil condition and stored food in the tubers not by

24

nutrition. The uniform emergence in all N treatments and different among varieties might be

attributed to the fact that germination process is mainly controlled by viability of seeds, adequate

moisture, proper temperature and good aeration and least by soil fertility. Jan et al. (2002) also

stated that embryo grows at the expense of stored food materials and did not require any external

nutrition.

The function of nitrogen is to stimulate plant growth and enlarge leaves and tubers. Such

prolonged vegetative growth may delay reproductive stage. The delaying of days to 50% flower

initiation with the increasing application rates of N might be attributed to the positive effect of N

that stimulated growth and prolonged vegetative phase thus, delaying the reproductive phase of

plants (Tisdale et al., 2003; Khan et al., 2009). Nitrogen fertilizer treatment highly significantly

prolonged both the days to flowering and physiological maturity (Mulubrhan, 2004).

Alemayehu et al. (2015) have also reported the interaction of planting density and nitrogen rates

as significantly influenced days required for flowering at Haramaya. They further justify that

high N fertilizer increased the leaf area which increases the amount of solar radiation intercepted

and consequently prolongs days to flowering. Other researchers also reported similar results in

some other parts of the country (Zelalem et al., 2009; Israel et al., 2012). Furthermore NPS

fertilizer prolonged days to flowering and maturity of different vegetables including potato in

different agro-ecologies (Ayichew et al., 2009; Gebremeskel, 2016; Mekashaw, 2016; Yosef,

2016). Belete variety flowered and matured after 84, and 112 days of planting, respectively,

when potato plants were applied with 272 kg ha-1 of NPS fertilizer (Jemberie, 2017).

2.8. Effect of Nitrogen and Phosphorus on Growth of Potato Parameters

2.8.1. Number of Main Stems

A comprehensive understanding of this concept can be used to manipulate the production of

ware and seed potatoes (Admire et al., 2014a). The general crop performance, harvestable yield

and tuber size are strongly influenced by stem number per hectare (shayanowako et al., 2014).

The number of stems per plant is reported to be under the influence of storage condition of tubers

and number of sprouts (Allen, 1978), physiological age of the seed tuber (Iritani, 1968), variety

(Lynch and Tai, 1989) and tuber size (Harris, 1978; Gulluoglu and Arıoglu, 2009). Iritani et al.

25

(1972) also reported increase in stems per plant with increases in seed size. Beukema, and Zaag,

(2001) reported that the number of main stem arising from a seed is important because it

influences the number and size of tubers at harvest.

Gray and Hughes (1978) observed close relationships between the number of main stems or

aboveground stems and total yields and graded tuber yields. These investigators claimed that

high stem number per plant favored high tuber yield through effect on haulm growth and tuber

number per plant. Hassanpanah et al., (2009) also observed main stem number per plant had

positive correlation with marketable tuber weight. Despite the fact that stem density is one of the

most important yield components in potato; it was not significantly influenced by mineral

nutrients. This could be due to the fact that the trait is much influenced by the inheritance of the

potato crop (Mulubrhan, 2004; Zelalem et al., 2009). This showed a mix picture when suggestion

from Hossain et al., (2003) and Hassanpanah et al.(2009) who reported the increase in stem

number due to applying nitrogen fertilizer is taken into account.

2.8.2. Plant Height

Plant height increased with rate of fertilizer application, this could be attributed to the enhanced

availability of nutrients to the crop which may have resulted in increased photosynthetic

efficiency and increased metabolic activities of the plant with an increase in fertilizer level.

Sharma et al. (2014) reported that plant height increased with increasing fertilizer levels of

nitrogen and phosphorus. Jamaati-e-Somarin et al. (2009) and Yibekal (1998) have also reported

that, the highest rate of 200 kg N ha-1 gave the highest plant height of potato, as it was observed

in the present experiment that application of the highest nitrogen and phosphorus rate gave the

highest plant height (71.6cm) than those of other rates NPS fertilizer applied. Mulubrhan (2004)

and Zelalem et al. (2009) have also reported that increasing application of nitrogen and

phosphorus highly significantly increased the height of potato plants. Plant heights and leaf

numbers increased as rates of NPS fertilizer application increased on other vegetable crops

including cabbage, onion and garlic (Yayeh et al., 2017). Additionally Sulfur plays an essential

role in chlorophyll formation and many reactions of living cells Tisdale et al. (1995).

26

2.9. Effect of Nitrogen and Phosphorus on Yield Components of Potato

Fertilizer responses of crops vary with the crop varieties used and climatic conditions of the

production areas (Singh, 1993 and Tisdale, 1995). In this regard, various researches have been

conducted throughout Ethiopia with the objectives of determining the fertilizer requirements of

potato. An experiment conducted on clay soil in the eastern part of Ethiopia indicated that

application of 87 kg N and 46 kg P2O5 per hectare was needed for optimum yield of potato

(Beyene and Getu, 1998).

According to Bereke Tsehai (1988) application of 150/66 kg ha-1 of N/P2O5 under rain-fed

condition resulted in a yield advantage of 32% over the unfertilized control. According

to Mulubrhan (2004), the application of 165 kg N ha-1 and 90 kg P2O5 ha-1 is needed for

optimum potato production on vertisols of Mekelle area. Zelalem et al. (2009) found in their

study conducted on response of potato to different fertilizer levels under rain fed highland

situation at Deber Berhan area and 207 kg N ha-1 and 90 kg P2O5 ha-1 gave optimum tuber yield.

2.9.1. Tuber Number

Nitrogen application to potatoes before tuber initiation increases the number of tubers per plant

and mean fresh tuber weight (Kanzikwera et al., 2001). Sharifi et al. (2005) and Zelalem et al.

(2009) also reported that there was a significant tuber number increase in response to N

application. Similarly, Jenkins and Mahamood (2003) observed that the number of tubers varied

considerably as a result of N fertilization, and doubled when N level was increased to higher

levels.

Shahzad et al. (2010) in their research on yield and yield component of potato tuber as affected

by nitrogen fertilizer and plant density showed that there was a significance difference in number

of tubers per m2 with in different rates of nitrogen. The authors stated that there was an increase

in number of tubers with increasing nitrogen rates up to 160 kg N ha-1 beyond which the result

showed a decrease in number of tubers. The highest tuber number of 96.83 and the lowest of

72.52 per m2 were recorded at 160 and zero kg N ha-1, respectively.

https://scialert.net/fulltextmobile/?doi=ijss.2012.146.156#42000_con

https://scialert.net/fulltextmobile/?doi=ijss.2012.146.156#12843_tr

https://scialert.net/fulltextmobile/?doi=ijss.2012.146.156#947162_ja

27

Mulubirhane (2004) in his research on the effects of nitrogen, phosphorus, and potassium

fertilization on the yield and yield components of potato stated that there were highly significant

differences in total tuber number due to the increased application of N and P. Increasing the

application of N from 0 to 165 kg N ha-1 increased total tuber number per hill significantly from

8.44 to 9.84. Zelalem et al. (2009) in their research on response of potato to different rates of

nitrogen and phosphorus fertilization indicated nitrogen fertilization had a significant effect on

tuber number of potato. The result also showed that increasing the level of N increased the

number of tubers. Comparing to the zero level of N 207 kg N ha-1 had 32.9 % more number of

tubers. Increasing the N level from 0 to 207 Kg ha-1 increased the number of tubers per hill from

11.49 to 15.27.

2.9.2. Average Tuber Weight and Tuber Size Distribution

Tuber weight is reported to be affected by variety and growth conditions. Environmental

factors that favor cell division and cell expansion such as mineral nutrition, optimum water

supply, etc. were reported to enhance tuber size (Reeve et al., 1973). The result of a study

conducted by Dela Morena et al. (1994) showed that variation in tuber yield due to Nitrogen

treatments were related to the tuber weight increment. Similarly, other studies indicated that

the potato yield component most affected by N and K application was the mean tuber weight

(Harris, 1978; Giardini, 1992). Sharma, and Arora, 1987 from their investigations on the

effect of mineral nutrition on size categories of the potato tuber, showed that increase in the

yield of tubers with applied N and K nutrients was associated with increase in the number of

tubers in the medium and large grades at the expense of small tubers.

Furthermore application of N has been reported to increase the size of tubers (Reddy and Rao,

1968; Herlihy and Carroll, 1969). This was attributed to the increase in the weight of individual

tubers. Sharma and Arora, 1987 indicated that the increase in the weight of tubers with the

supply of fertilizer nutrients could be due to more luxurious growth, more foliage and leaf area

and higher supply of phtosynthates that helped in producing bigger tubers resulting in higher

yields. N and K application were also noted to extend the canopy life there by prolonging the

duration of tuber bulking (Harris, 1978; Peter and Hruska, 1988).

28

2.10. Tuber Quality Related Traits Parameters

2.10.1. Specific Gravity

According to Warren and Woodman, (1974) specific gravity has been considered the most

practical index of mealiness in potatoes. Similarly, Tesfaye et al.( 2013) reported that specific

gravity is the measure of choice for estimating dry matter content (DMC) and starch content

(SC) and ultimately for determining the processing quality of potato varieties. Potatoes of high

dry matter contents, more typically expressed as high specific gravity, are important in

processing industry in terms of finished product yield, oil uptake and quality (Sayre et al. 1975).

Painter and Augustine, (1976) and Kleinkopf et al. (1981) reported that the specific gravity of

tubers decreased with increasing rates of N fertilizer. Similar result was reported by (Mulubrhan,

2004) that increasing the application of N from 0 to 165 kg ha-1 reduced specific gravity from

1.076 to 1.069.

On the other hand, Robert and Cheng (1988) and Simret et al. (2010) noted that non-significant

difference in specific gravity of tubers due to nitrogen treatment. Conflicting results have been

reported regarding the effect of P fertilization on tuber specific gravity of potato. Human (1961)

noted an increase in specific gravity in response to an increase in applied P. However, Zandstra

et al. (1969) reported a reduction in specific gravity as the rate of phosphorus fertilizer increased.

As opposed to the above findings, Lujan and Smith, (1994) and Zelalem et al. (2009) reported

non-significant effect of phosphorus on the specific gravity of tubers. Similarly Adhikari and

Sharma (2004) and (Dubetz and Bole 1975) reported that high levels of P did not influence

specific gravity.

2.10.2. Dry Matter Content

Dry matter is one of the important traits after yield, since the genotypes, which have more dry

matter percentage have more importance for the industrial, economical purposes and also storage

property. The dry matter content of potato tubers determines suitability for chip processing

purposes by influencing the chip yield, texture flavor, final oil content and process efficiency

(Kumlay et al., 20002; Kaber et al., 2001). Potato chips processing requires tubers with dry

matter content of greater or equal to 20% and specific gravity of greater or equal to 1.080

29

(Kabira and Lemaga, 2006). No consistent effect of phosphorus fertilization on the nitrogen

containing components of potato tubers has been observed. Mulder and Bakema (1956) have

found that non-protein nitrogen content was higher with phosphorus deficiency, while

Marchenko (1959) has found that P and K fertilization had little effect on nitrogen content.

Kandi (2011) reported a reduced percent dry matter of potato tubers as nitrogen rates increased.

Similar findings were reported by Wilcox and Hoff (1970) and Painter and Augustine (1976).

Similarly, Asefa (2005) has indicated that increasing rate of nitrogen and phosphorous

application significantly decreased specific gravity and dry matter content of potato tuber. Other

finding reported by Cucci, and Lacolla (2007) that dry matter percentage increased shifting from

the control to the application of 200 kg N ha-1 and 50 kg P ha-1 from 23.0 to 26.2% and decreased

at the highest N level, without any difference being observed with the change in the P rate.

Additionally,(sparrow et al., 1992) who have observed non-significant reduction in percent dry

matter of tubers due to increased P application and (Zelalem et al., 2009), have also, suggested

that phosphorus fertilization did not significantly influence tuber specific gravity and dry matter

content.

2.10.3. Starch Content

Starch content represents dry matter content of potatoes (Hogy and Fangmeier, 2009); therefore,

the variety and plots that produced tubers with highest dry matter content also had highest starch

content. Positive linear correlations among tuber specific gravity, dry matter and starch content

have been reported by different researchers (Burton, 1966; Schippers, 1976). Accordingly, the

observed differences in starch content of tubers among different varieties could be related to

differences in specific gravity. The relationship between specific gravity, dry matter and starch

contents of potatoes has been developed by several workers and associations (Fitzpatrick et al.,

1969; Kleinkopf et al., 1987; Hassel et al., 1997). Similarly, the relationship among internal

tuber quality traits has been found to vary with variety, location, season and year of cultivation

(Verma et al., 1972).

2.11. Importance of Sulphur in Potato Production

2.11.1. Role of Sulphur in Combination with other Nutrients

30

A number of experiments have demonstrated that sulphur fertilization significantly changes the

chemical composition of crops. The availability of sulphur determines the efficient use of

nitrogen by plants and consequently affects plant composition and quality (Krauze, and Bowszys

2000; Wielebski and Muśnicki, 1998a; Podleśna, 2003). Nitrogen content in tested plants is

significantly modified by the content of sulphur in soil available to plants. (Koter and Grzesiuk,

1966) demonstrated that fertilization with calcium sulphate increased the content of protein

nitrogen, which indicated better uptake of nitrogen by red clover and the total nitrogen content in

plants also increased. Lack of sulphur did not inhibit nitrogen uptake by plants, and it was

accumulated in non-protein compounds Koter, and Grzesiuk, 1966. Similar findings were made

by (Uziak, and Szymańska, 1969; Goźliński, 1970a; Uziak, and Szymańska, 1987), who, having

applied increasing doses of sulphur in the form of potassium sulphate, achieved an increase in

the content of protein nitrogen in harvested crops.

Sulphur starvation limited the accumulation of Protein nitrogen in crops, but increased the

content of asparagines, glutamine and aspartic acid in leaves. The researchers indicated that

legume plants could bind large amounts of nitrogen if the level of supplied sulphur is sufficient.

The most important impact of sulphur on plant growth is observed for plants growing on soils

rich in bioavailable nitrogen. Sulphur deficiency results in inhibited photosynthesis, and this is

reflected in an increased content of non-protein nitrogen. In plants suffering from severe sulphur

starvation this form of nitrogen accounted for up to 70% of the total nitrogen content, while in

plants sufficiently supplied with sulphur protein nitrogen dominated. This indicates that role of

sulphur in protein synthesis (Grzesiuk, 1965). Lack of Sulphur limited bioassimilation of

nitrogen, promoting an increase in the concentration of nitrate nitrogen and organic non-protein

nitrogen (Koter and Benedycka, 1984).

A study carried out by (Pyś and Pucek, 1993a, c) revealed that fodder rye, oats, wheat and barley

grown near sulphur land sites contained a high proportion of protein nitrogen to total nitrogen,

suggesting the high nutritional value of crops. The mean total nitrogen content was 1.13-1.73%

d.m. for rye, 1.15-2.05% d.m. for wheat, and 1.83-2.36% d.m. for barley. The use of sulphur for

plant fertilization generally promotes an increase in the total nitrogen content, as indicated by

(Koter and Grzesiuk, 1966; Seidler 1975; Uziak and Szymańska, 1987; Koter and Benedycka

1984; Wielebski and Muśnicki 1998b; Barczak and Nowak, 2010; Wielebski 2011). Sulphur

31

fertilization enhances the content of exogenous amino acids, in particular the component

containing amino acids: methionine, cysteine and cysteine dimmer being cysteine (Horodyski,

krzywińska, 1979). This was confirmed in studies by (Barczak, 2010), who found that sulphur

fertilization, in comparison to non-fertilized (controls), usually caused a significant increase in

the content of most amino acids in proteins, as well as the indicators of protein biological value,

i.e. chemical store index (CSI) and essential amino acids index (EAAI).

Sulphur fertilization significantly increased the indices of protein nutritional value net protein

uptake (NPU), biological value (BV) and protein efficiency ratio (PER) of spring barley kernels.

The analysis of index values demonstrated the leading role of sulphur in maintaining a positive

nitrogen balance in experimental animals, improving the efficiency of animal feeding. Sulphur

fertilization induces changes in the content of total sulphur and sulphates in plants. Generally, it

increases the content of total sulphur, organic sulphur and sulphates (Koter, and Grzesiuk, 1966;

Babuchowski, 1971; Uziak, and Szymańska, 1979; Benedycka 1983; Uziak, and Szymańska,

1987; Krauze, and Bowszys, 2000; Podleśna, 2004; Barczak, and Nowak 2015).

Plants grown under conditions of low sulphur supply without sulphur fertilization contain low

amounts of total sulphur and trace levels of sulphates. A negligible content of inorganic sulfur in

this case is a good indicator of sulphur starvation in plants Grzesiuk, 1965. Sulphur

supplementation has a positive effect on crop quality by increasing the content of organic sulphur

compounds. At good levels of sulphur supply to plants, the share of sulphates in different

vegetative organs may reach 50-80% of its total level, but its large share has no longer any

positive or negative effects on plant growth. When the supply of sulphur was insufficient, the

content of total sulphur decreased to about 0.1% in straw and to 0.05-0.07% in stems. Under

conditions of sulphur shortage, the intensity of its uptake by roots and transport to aerial parts

were much higher than in sufficiently nourished plants (Goźliński, 1965). Seidler 1975 observed

a clearly antagonistic interaction between chlorine and sulphur. In all experiments, an addition of

chlorine caused a reduction in the content and uptake of sulphur by plants, indicating the

inhibitory effect of chlorine on sulphur uptake. The content of sulphur in protein, and thus the

amount of deficient sulphur-containing amino acids, evidently increased when plants were

fertilized with potassium sulphate (Benedycka, 1983).

32

2.11. 2. Effect of Sulphur on Yield and Tuber Quality of Potato

Genetically make up has great influence on yield and quality of potato tubers. Various varieties

of potato having wide variation in their yield potential and quality attributes have been evolved

(Marwaha et al., 2010). These varieties further show variation in their attributes under different

agro climatic conditions. The influence of location and cultivars on quality of potato tubers have

been reported by researchers (Uppal, and Paul, 2001; Kumar et al., 2003). Sulphur is one of

sixteen essential nutrient elements and fourth major nutrient after NPK, required by plants for

proper growth and yield as it is known to take part in many reactions in all living cells Sud, and

Sharma, 2002. Sulphur deficient plants had poor utilization of nitrogen, phosphorus and potash

and a significant reduction of catalase activities at all age (Nasreen et al., 2003).

Intensive cropping and use of high-grade fertilizers have caused the depletion of sulphur in soils.

Decrease in tuber dry matter yield and concentrations of dry matter, starch and essential amino

acids particularly cysteine and leucine were observed with sulphur deficiency Eppendorfer and

Eggum, 1994a; Petitte and Ormrod, 1988. Sulphur has a direct effect on soil properties as it

may reduce Ph which improves the availability of microelements such as Fe, Zn, Mn and Cu as

well as crop yield and its related characteristics (Tantawy et al., 2009). The need of application

of sulphur along with its beneficial effects on yield and quality has been reported by earlier

workers (Chettri et al., 2002; Prakash et al., 1997; Singh et al., 1995). Sud and Sharma 2000 who

reported that increase in tuber yield with increasing sulphur levels may be attributed to its role in

better partitioning of the photosynthesis in the shoot and tubers. Similarly, Lalitha et al.

2002 have also reported significant effect on grade wise tuber yield and increase in bulking rate

with sulphur application. But heavy applications of sulphur can result in yield reductions Eddins,

1934. These findings are also in agreement with those of (Nasreen et al., 2007) in onion.

Quality parameters, i.e., dry matter, specific gravity, total sugar content, starch content were

observed and found that they were differed significantly with potato varieties. Ramamurthy, and

Devi, 1982 also reported significant increase in dry matter content in tuber with sulphur

application. However, they did not find any significant effect on specific gravity, starch and total

sugar content. Sulphur deficiency reduced the starch content of potatoes Eppendorfer, and

https://scialert.net/fulltextmobile/?doi=ijar.2011.143.148#595385_ja



https://scialert.net/fulltextmobile/?doi=ijar.2011.143.148#20187_bc



http://www.scialert.net/asci/result.php?searchin=Keywords&cat=&ascicat=ALL&Submit=Search&keyword=dry+matter


http://www.scialert.net/asci/result.php?searchin=Keywords&cat=&ascicat=ALL&Submit=Search&keyword=amino+acid

http://www.scialert.net/asci/result.php?searchin=Keywords&cat=&ascicat=ALL&Submit=Search&keyword=amino+acid




http://www.scialert.net/asci/result.php?searchin=Keywords&cat=&ascicat=ALL&Submit=Search&keyword=principal+component+analysis

http://www.scialert.net/asci/result.php?searchin=Keywords&cat=&ascicat=ALL&Submit=Search&keyword=soil+pH












33

Eggum 1994b. (Singh et al., 1995) also found significant increase in dry matter content in

potato tuber with sulphur application.

3. MATERIALS AND METHODS

3.1. Description of the Study Site

The experiment was conducted on the end of June 2018 under rain fed condition at Raare,

Haramaya University’s research field.The University is located at latitude of 9o 24‟10.8‟‟ N,

longitude of 42o 3‟30.07‟‟E and at altitude of 2006 meter above sea level (m.a.s.l) (Habtamu et

al., 2016). Agro-ecologically the area is classified as semi-arid tropical belt of eastern Ethiopia

and is characterized by a sub-humid type of climate. Data recorded from meteorology station

located at Haramaya university, indicates that, the mean annual (2005-2014) rainfall of the area

is about 839.9 mm. The study area is characterized by a bimodal rainfall distribution pattern. The

short rainy season locally, called Badheessa, usually starts in March and extends to May, while

the main/long rainy season, called Ganna, stretches from end of June to September (Kibebew,

2014). The mean annual temperature is 16.9oC with mean minimum and maximum temperature

of 3.8 and 25oC, respectively. The mean relative humidity is 50%, varying from 20 to 81% and

the soil type of the area is well-drained deep alluvial sandy loam that contains 14 g/kg organic

matters, 1.14 g/kg total nitrogen, 0.01g/kg available phosphorus, 0.47 g/kg total potassium and

pH of 7.2 (Tekalign, 2013) and percent sand, silt, and clay contents of 63, 20, and 17,

respectively (Simret, 2010).

3.2. Description of Experimental Materials

Three potato varieties, namely Bubu (CIP-384321.3), Belete (CIP-393371.58) and Shangi were

used in this experiment. Variety, Bubu was released by Haramaya University in 2011 and said to



34

be adapted to the altitude of 1650-2330 m.a.s.l., with annual total rain fall of 700-800 mm. Bubu

is high yielding and resistant to late blight (MARD, 2012). Bubu is a medium maturing variety

(99 days to maturity) and had a yield of 32-40 and 25-35 t/ha at research and farm field,

respectively. Belete was released in 2009 by Holeta Agriculture Research Center and it was

recommended for mid and high land areas (1600 to 2800 m.a.s.l.) and had a yield potential of

47.2 and 33.8 t/ha at research and farmers field, respectively. Belete has large tuber size and

resistant to late blight. Shangi is recently introduced as resistant variety to late blight disease and

having short tuber dormancy period. The variety was evaluated for three cropping seasons of

which the two and one experiments were under irrigation and rain fed conditions, respectively.

The variety produced average total and marketable tuber yields of 35.47 and 33.02 t ha-1,

respectively. It has tuber dormancy period of one month and evaluated as moderately resistant

variety to late blight disease at Haramaya condition in 2017 (Msc Thesis of Haramaya University

student).

3.3. Treatments and Experimental Design

The experiment was consisted of three potato varieties (Bubu, Belete and Shangi) and seven

rates of blended NPS fertilizer (0, 50, 100, 150, 200, 250 and 300 kg ha-1). The rates of blended

NPS fertilizer were arranged as the substitute of DAP fertilizer at the rate of 200 kg (92 kg P2O5)

ha-1 that was used for potato production as recommendation of Haramaya University. The total

quantity of NPS fertilizer was applied at the time of planting at the depth of 10 cm below the

seed tuber. The recommended Urea (100 kg ha-1) fertilizer by Haramaya University was applied

7-10 cm away from the plant as two side dressings for in split application (50% and 50% at 30

and 50 days after planting, respectively) uniformly on all plots except the control. The rates of

fertilizer and amount of mineral nutrient contents in seven levels of blended NPS fertilizer are

presented in (Table 1).

The experimental design was randomized complete block design (RCBD) with three replications

in factorial arrangements. Each treatment combination was assigned in one plot of each

replication with the plot size of 3.60 x 4.50 meters (16.2 m2). The spacing between plants in a

row and between rows was 0.3 and 0.75m, respectively, in which one plot was consisted of six

rows each with 12 plants and a total of 72 plants per plot. Well sprouted seed tubers of potato

35

were planted at the spacing of 75 cm between rows and 30 cm between plants. The spacing

between plots and blocks was one meter and one and half meters, respectively. Other cultural

practices like weeding, earthing up, and cultivation and plant protection methods are done

uniformly for all experimental plots as recommendation of Haramaya University and EIAR

(2007) for the crop.

Table 1. Amount of mineral nutrient contents in seven rates of blended NPS fertilizer set as

treatments

No.

Blended NPS

fertilizer rate

kg ha-1

Nutrient contents from blended

NPS fertilizer kg ha-1

N from

Urea kg ha-1 Total

N kg ha-1 N P2O5 S N

1 0 0 0 0 0 0

2 50 9.5 19 3.5 46 55.5

3 100 19 38 7 46 65

4 150 28.5 57 10.5 46 74.5

5 200 38 76 14 46 84

6 250 47.5 95 17.5 46 93.5

7 300 57 114 21 46 103

3.4. Experimental Procedures

Land preparation: Land was ploughed to a depth of 25 to 30 cm by a tractor; then after it was

leveled and ridges were made by hand.

Planting: A Medium sized (39-75 g) and well sprouted seed tubers were planted at the sides of

the ridges at the end of June, 2018 during starting of the rainy season. The tubers were planted at

5 cm depth as recommended (Mahamood et al., 2001).

Other cultural practices: weeding and cultivation (earthing up) were done at the appropriate

time to facilitate root, stolon and tuber growth.

Harvesting: When the plants reached physiological maturity or when yellowing or apparent

senescence was observed on the lower leaves, the haulm was mowed two weeks before

harvesting to check tuber periderm to avoid bruising and skinning during harvesting and

36

postharvest handling. The plants growing in the two border rows as well as those growing at both

ends of each row was not harvested as experimental materials to avoid edge effects.

3.5. Soil Sampling and Analysis

A soil sample was taken in zigzag pattern before planting randomly from the experimental site at

a depth of 0-30 cm using an auger at the interval of 5-10 meters. The sample was mixed

thoroughly to produce one representative composite sample. About one kilogram of composite

sample was taken using polyethylene bag and was given to Haramaya University Soil

Laboratory. The composite soil sample was analyzed for selected physicochemical properties

mainly soil texture (sand, silt and clay %), soil pH, total nitrogen (N), available sulphur (S),

organic carbon (OC), available phosphorus (P), Exchangeable potassium (K) ,Electrical

conductivity and cations exchange capacity (CEC) (c mol kg-1) using the appropriate laboratory

procedures.

Total N in the soil was determined by the Kjeldahl method (Dewis and Freitas, 1975). Organic

carbon content of the soil was determined by reduction of potassium dichromate by organic

carbon compound and determined by reduction of potassium dichromate by oxidation

reduction titration with ferrous ammonium sulfate (Walkley and Black, 1934). Particle size

distribution was determined by hydrometer method (FAO, 2008). Available P was determined

by the Olsen's method using a spectrophotometer (Olsen et al., 1954). Cation exchange

capacity (CEC) was determined after saturating the soil with 1N ammonium acetate

(NH4OAc) and displacing it with 1N NH4OAc (Chapman 1965). The pH of the soil was

determined using 1:2 (weight volume-1) soil to CaCl2 solution ratio and a glass electrode

attached to digital pH meter (FAO 2008). Available sulfur (S) was measured using turbic metric

method (EthioSIS, 2014).

37

3.6. Data Collection and Measurements

Data on crop phenology, yield, and yield components was collected on plot basis while growth

and tuber quality related traits was collected from sample plants and tubers, respectively. The

data collection and measurements was accomplished as per the procedures for standard

evaluation trials of advanced potato clones established by the National Potato Research Program

and International Potato Center (CIP, 2010). The description of data collection and

measurements for each trait is presented in subsequent sub-titles as follows.

3.6.1. Phenology and Growth Parameters

Days to 50% emergence: It was recorded when 50% of the plants in each plot sprouted and

emerged.

Days to 50% flowering: It was recorded by counting the number of days from planting to

50% of the plant populations in each plot produced flowers.

Days to 50% maturity: It was recorded by counting the number of days from planting to

haulms (vines) of 50% of the plant population becomes yellow or starting senescence.

Plant height (cm): The height of 10 randomly selected plants from the central rows was

measured at physiological maturity stage from ground surface to the tip of the main stem and

averaged to get the mean plant height.

Stem number per hill: The total numbers of main stems that arose from the ground was counted

using five randomly selected plants from the central rows in each plot and the mean number

of stem per hill was calculated. Only stems arising from the mother tuber was considered as main

stems.

3.6.2. Yield Components and Tuber Yield

Average tuber weight (g): It was recorded by dividing total fresh weight of tubers by the total

number of fresh tubers per plot.

38

Tuber number per hill: Mean number of tubers produced from the middle rows, was counted

at harvest and expressed as number of tubers per hill.

Marketable tuber yield (t ha-1):

Mean weight of marketable tubers produced from the middle rows, was recorded at harvest by

weighing tubers which were healthy and greater than 20g. The value were taken in kg/plot and

converted to t ha-1.

Unmarketable tuber yield (t ha-1):

Mean weight of unmarketable tubers produced from middle rows was recorded at harvest and

those rotten, turned green and less than 20g, were considered to determine unmarketable tuber

yield, (kg/plot) and converted in to t ha-1.

Total tuber yield (t ha-1):

It was recorded as the sum of both marketable and unmarketable tuber yields. The total tuber

yield (kg/plot) was weighed and converted to t ha-1.

Tuber size grades (%):

Tuber size distribution in weight (%): it is the proportional weight of tubers size categories

which was taken at harvest. All tubers from plants in the central rows of each plot were

categorized into small (< 39 g); medium (40-75 g), and large (> 75 g) according to Lung’aho et

al. (2007). Then each of these categories was counted, and the proportion of the weight of each

tuber category was expressed as a percentage.

3.6.3. Tuber Quality Related Traits

Tuber dry matter content (%): five fresh tubers were randomly selected from each plot

and washed, weighed and sliced at harvest, sun dried for seven days and further dried in an

oven at 75 0C for 48 hours until a constant weight will be obtained. Finally, dry matter percent

39

was calculated according to the formula given by William and Woodbury, (1968).

𝐃𝐫𝐲 𝐦𝐚𝐭𝐭𝐞𝐫 (%) =weight of sample after drying (g)

initial weight of sample (g) 𝑥100

Specific gravity of tubers (gcm-3): This was determined by the weight in air/weight in water

method. Five kg tubers of all shapes and sizes were randomly taken from each plot. The selected

tubers were washed with water. The samples were then be first weighed in air and then re-

weighed suspended in water. Specific gravity was then calculated using the following formula

(Kleinkopf et al, 1987). Specific gravity of tubers (gcm-3) was determined using the method

described by Fong and Redshaw, (1973) as:

𝐒𝐩𝐞𝐜𝐢𝐟𝐢𝐜 𝐆𝐫𝐚𝐯𝐢𝐭𝐲 =weight in air

weight in air – weight in waterx100

Total starch content (g/100 g): Percentage of starch in tubers was calculated from the specific

gravity where specific gravity. Starch (% or g/100 g) =17.546 +199.07 × (specific gravity-

1.0988) (Smith and Talburt, 1959as cited by Yildrim, and Tokuşoğlu, 2005).

3.7. Partial Budget Analysis

Partial budget analysis was carried out as per the methodology described in CIMMYT (1988).

Data like, cost incurred for buying blended NPS and Urea fertilizers labor cost for application of

fertilizers, cultivation and harvesting and the price of the marketable yield of potato varieties

after harvest was taken in to account to undertake cost-benefit analysis. The partial budget

analysis was generally carried out on the basis of the formula developed by CIMMYT (1988) as

follows.

Gross marketable tuber yield (kg ha-1) (MTY): is marketable tuber yield of each treatment per

hector.

Adjusted yield (AjY): is the average yield adjusted downward by a 10% to reflect the difference

between the experimental yield and yield of farmers.

AjY = AvY- (AvY*0.1)

40

Gross field benefit (GFB): It was computed by multiplying field/farm gate price that farmers

receive for the crop when they sale it as adjusted yield.

GFB = AjY*field/farm gate price for the crop

Total cost: is the cost of fertilizers and other treatments for the experiment. The costs of other

inputs and production practices such as labor cost for land preparation, planting, weeding, and

harvesting was considered remain the same or considered as insignificant among treatments.

Net benefit (NB): was calculated by subtracting the total costs from gross field benefits for each

treatment.

NB = GFB – total cost

Marginal rate of return (MRR %): was calculated by dividing change in net benefit by change

in cost.

X 100

Where; MRR = Marginal rate of return in percent, ∆NB and ∆TC= change in net benefit and

change in total cost, respectively.

3.8. Data Analysis

All the measured parameters are subjected to analysis of variance (ANOVA) appropriate

to factorial experiment in RCBD according to the General Linear Model (GLM) of Gen

Stat 16th edition (GenStat, 2016) and the interpretations was made following the procedure

described by Gomez and Gomez (1984). Least Significance Difference (LSD) test at 5%

probability level was used for mean comparison following the significant differences results

from the ANOVA.

41

4. RESULTS AND DISCUSSION

4.1. Soil Physico-chemical Properties of the Experimental Site

The results of the laboratory analysis of some selected soil physical and chemical properties of

the experimental site before planting are presented in Table 2. The soil textural class of the

experimental site was identified as clay soil with a particle size distribution of 74.8, 22.65 and

2.53% clay, silt and sand, respectively. The pH of the soil was 8.4, which could be categorized

under moderate alkaline (Tekalign, 1991). The soil of the study site had 1.4% of organic carbon

(OC), which could be classified as low according to the rating of Tekalign (1991), indicating low

potential of the soil to supply nitrogen to plants through mineralization of organic carbon.

Tekalign et al. (1991) has classified soil total N content of < 0.05 as very low, 0.05-0.12% as

poor, 0.12-0.25% as moderate and > 0.25% as high. According to this classification, the soil

sample of the experimental site was found to have moderate level of total N (0.23%) indicating

that the nutrient to be a limiting factor for potato production in the study area.

Indicative ranges of available phosphorus have been established by Olsen et al. (1954) classified

available phosphorus <5 mg kg-1 as very low, 5-15, 15-25 and >25 mg kg-1 as low, medium and

high, respectively. Thus the soil of experimental site was considered as low in available

phosphorus content which was 8.8 mg kg-1. The low phosphorus content of the soil is probably

attributed to high phosphorus fixing capacity of the soil (Wakene et al., 2002). Such properties

indicate that the experimental soil has some limitation with regard to its use for crop production.

The findings signify that the soils require external application of nutrients according to

42

recommendation for the crops grown. The analysis for available sulfur also indicated that the

experimental soil had values of 20.0 mg/kg which was low according to Ethiosis (2014).

London (1991) classified that top soil having CEC greater than 40cmol (+) kg-1 are rated as very

high and 25-40 cmol (+) kg-1 as high, while) 15-25, 5-15 and <5 cmol (+) kg-1 of CEC soil are

classified as medium, low and very low, respectively., According to this classification, the soil of

experimental site had high CEC, which was 38.36 cmol (+) kg-1, indicating its high capacity to

retain cations. The soils with high CEC are suitable for potato production. High CEC coupled

with light texture such as clay loam soil is believed to be suitable for crop production (Manjulav,

Nathan. 2009). According to Hazelton and Murphy (2007), who described that soil salinity effect

below 2.0 ds /m is mostly negligible for most crops thus the soil of experimental site had no

salinity problem as the electrical conductivity of the soil was about 0.76 ds/m (Table 2).

Table 2. Selected soil phsico-chemical properties of the experimental site

Parameter Values Rating Reference

Soil texture Clay (%) 74.82 Silt (%) 22.65

Sand (%) 2.53

Textural class Clay

Electrical Conductivity (ds/m) 0.76

PH (1:2.5 H20) 8.4 alkaline Tekalign (1991)

Total N (%) 0.23 Medium Tekalign (1991)

Organic carbon (%) 1.4 Low Tekalign (1991)

CEC [Coml.(+) kg-1 soil] 38.4 High London (1991)

Available phosphorus (mg/kg) 8.8 Low Cottenie (1980)

Available Sulfur (mg/kg) 20 Low Ethiosis (2014)

Exchangeable Potassium cmol.(+) /kg soil 0.48 Medium FAO (2006)

43

4. 2. Phenology and Growth of potato

4.2. 1. Phenology

All phenology traits viz. days to 50% emergence, flowering and maturity were significantly

influenced by variety, and blended NPS fertilizer had significant effect on days to 50% flowering

and maturity. The interaction of variety x NPS fertilizer significantly influenced days to 50%

flowering, but the two main factors interaction had nonsignificant effect on days to 50%

emergency and maturity (Appendix Table 1).

Shangi had significantly delayed days to 50% emergence and maturity. Belete also had

significantly delayed days to 50% emergency as Shangi variety (Table 3). The presence of

significant differences among varieties for days to 50% emergence may be attributed by genetic

variations of cultivars and influenced by the physiological age of the tubers, but not by external

supply of nutrients. Lung’aho et al. (2007) stated that physiologically old tubers take relatively

short times whereas physiologically young tubers take longer times to emerge from the soil. This

is consistent with the suggestion of Mulubirhane (2004) that emergence depends on the soil

condition and stored food in the tubers not by nutrition. This is also consistent with the

suggestion of Jan et al. (2002) that embryo grows at the expense of stored food materials and did

not require any external nutrition.

Table 3. Effect of potato variety on days to 50% emergence and maturity at Haramaya during

2018 cropping season

Variety Days to 50%

emergence

Days to 50%

maturity

Bubu 12.90b 87.29b

Belete 13.24ab 86.52b

Shangi 13.81a 90.19a

LSD (5%) 0.602 1.063

Mean values followed by the same letter(s) within columns (each trait) had nonsignificant

difference at 5% probability level. LSD (5%) = least significant difference at P < 0.05.

The maturity of potato varieties was delayed as the varieties supplied by the increased rates of

NPS fertilizer (Table 4). The delayed days to 50% maturity (91.78 days) was observed at the

highest rate of 300 kg ha-1 NPS fertilizer whereas the shortest days to 50% maturity (84.78 days)

was registered in plots that did not receive fertilizer. The application of 250 kg ha-1 NPS fertilizer

44

also significantly delayed the maturity of potato varieties. The growing of plants without

fertilizer application and the effect of 50 and 100 kg ha-1 NPS fertilizer on the maturity of potato

varieties had nonsignificant difference.

The delayed days to maturity of potato varieties due to the application of NPS fertilizer at the

highest rates might be due to the three nutrients interaction and synergetic effect of the three

nutrients. Nitrogen is involved in all major processes of plant development and yield formation.

Besides a good supply of Nitrogen to the plant stimulates root growth and development as well

as uptake of other nutrients (FAO, 2000; Brady and Weil, 2002). An adequate supply of N is

associated with high photosynthetic activity, vigorous vegetative growth, and dark green color as

result it delayed the crop maturity. The result is consistent with the findings of other researchers

where a crop with high nitrogen application mature later in the season than a crop with less

nitrogen (Beukema and Zaag, 1979). Application of nitrogen fertilizer prolonged the canopy life

of the plant, which enabled potato plants to maintain physiological activity for an extended

period, there by continuing photosynthesis. Therefore, the supply of crop with more nitrogen

mature later in the season than a crop with less nitrogen supply because of the extended

vegetative growth is related to excessive haulm development (Barbara, 2007; Israel et al., 2012).

The results of the present study are generally in agreement with the findings of various

researchers where increasing fertilizer rates, including NPS prolonged days to flowering and

maturity of different vegetable crops including potato in different agro-ecologies (Ayichew et al.,

2009; Gebremeskel, 2016; Mekashaw, 2016; Yosef, 2016 ; Jemberie, 2017).

Table 4. Effect of blended NPS fertilizer on days to 50% maturity of potato varieties at


Blended NPS fertilizer (kg ha-1) Days to 50% maturity

0 84.78e

50 85.11e

100 85.89de

150 87.78cd

200 89.33bc

250 91.33ab

300 91.78a

45

LSD (5%) 1.623

Mean values followed by the same letter(s) within column had nonsignificant difference at 5%

probability level. LSD (5%) = least significant difference at P < 0.05.

The three varieties in plots that did not receive fertilizer had significantly early flowering without

significant difference among varieties. Shangi variety observed in plots which received 300 kg

NPS ha-1 showed delayed days to 50% flowering, however, the effect of this rate had

nonsignificant difference with the effect of all rates of fertilizer except with the application of 50

kg NPS ha-1 on the same variety. The application of lower rates (50, 100 and 150 kg NPS ha-1)

had nonsignificant effect on growing of Bubu variety without fertilizer application. All rates of

fertilizer had been observed in plots which received 300 kg NPS ha-1.The application of all rates

of NPS fertilizer had nonsignificant difference on days to 50% flowering of Belete which all

resulted about 52 and 53 days of flowering (Table 5).

The delayed days to 50% flower of varieties towards the higher rates of NPS fertilizer might be

due to the higher rates of N supplied to plants. The higher rates of N from higher rates of NPS

fertilizer might have a positive effect to stimulate growth and prolonged vegetative phase thus,

delaying the reproductive phase of plants (Tisdale et al., 2003; Khan et al., 2009). Alemayehu et

al. (2015) also reported that the interaction of planting density and nitrogen rates had significant

influence on days required for flowering at Haramaya. They further justify that high N fertilizer

increased the leaf area which increases the amount of solar radiation intercepted and

consequently prolongs days to flowering. Zelalem et al. (2009) and Israel et al. (2012) also noted

that excessive vegetative growth and delayed flowering due to the application of high rates of

nitrogen. Similarly, Israel et al. (2012) reported that increased phosphorus application prolonged

the days to 50% flowering. The results of the present study are generally in agreement with the

findings of various researchers where increasing fertilizer rates, including NPS prolonged days to

flowering and maturity of different vegetable crops including potato in different agro-ecologies

(Ayichew et al., 2009; Gebremeskel, 2016; Jemberie, 2017; Mekashaw, 2016; Yosef, 2016).

Table 5. Interaction effect of blended NPS fertilizer and variety on days to 50 % flowering of

potato at Haramaya during 2018 cropping season

Blended NPS fertilizer (kg ha-1)

Variety

Belete Bubu Shangi

46

0 50.89 h 52fgh 50.67gh

50 52.67efg 54bcdef 53.33def

100 52fgh 54bcdef 55bcde

150 53.67cdef 54bcdef 56abc

200 53.33def 54.67abcde 55abcde

250 53.33def 55.33abcd 56.33ab

300 53.33def 55abcde 57a

LSD (5%) 1.339

Mean values followed by the same letter(s) in columns and rows had nonsignificant difference at

5% probability level. LSD (5%) = least significant difference at P < 0.05.

4.2. 2. Growth Traits

The height of plants was significantly affected by variety and blended NPS fertilizer while

number of main stem/hill was significantly influenced only by variety. The interaction of variety

x NPS fertilizer had nonsignificant effect on growth (plant height and number of main stem) of

potato (Appendix Table 1).

Belete had significantly highest number of main stem/hill and tallest plant height. Bubu had

significantly higher number of main stem/hill than Shangi variety. The plant height of Bubu and

Belete had nonsignificant differences, but the plant height of both varities was significantly

highest than Shangi (Table 6).

This result is in agreement with the findings of Mulubrhan (2004), Zelalem et al. (2009) and

Israel et al. (2012) who reported that mineral fertilizers like nitrogen and phosphorus did not

affect the number of main stem of potato. Consistent with the result of this study, Assefa (2005)

reported that stem number per hill was not significantly affected with the application of different

N and P rates. Simret (2010) also reported that different rates of nitrogen and phosphorus did not

affect the stem number of potato.

Table 6. Effect of variety on growth of three potato varities at Haramaya during 2018 cropping

season

Variety Plant height (cm) Number of main stem/hill

Belete 70.14a 6.75a

Bubu 69.63a 5.31b

47

Shangi 66.56b 3.09c

LSD (5%) 2.896 0.725

Mean values followed by the same letter(s) within columns (each trait) had nonsignificant


The shortest plants were observed in plots that did not receive fertilizer whereas the tallest plants

were observed in plots that received the highest rate of (300 kg ha-1 NPS) fertilizer application.

The height of plants without fertilizer application and the effect of 50, 100 and 150 kg ha-1 NPS

fertilizer had nonsignificant difference (Table 7).

Sharma et al. (2014) reported that plant height increased with increasing fertilizer levels of

nitrogen and phosphorus. This could be attributed to the enhanced availability of nutrients to the

crop which may have resulted in increased photosynthetic efficiency and increased metabolic

activities of the plant with an increase in fertilizer level. Jamaati-e-Somarin et al. (2009) and

Yibekal (1998) have also reported that, the highest rate of 200 kg N ha-1 gave the highest plant

height of potato, as it was observed in the present experiment that application of the highest

nitrogen and phosphorus rate gave the highest plant height (71.6cm) than those of other rates

NPS fertilizer applied. Mulubrhan (2004) and Zelalem et al. (2009) have also reported that

increasing application of nitrogen and phosphorus highly significantly increased the height of

potato plants. Plant heights and leaf numbers increased as rates of NPS fertilizer application

increased on other vegetable crops including cabbage, onion and garlic (Yayeh et al., 2017).

Additionally Sulfur plays an essential role in chlorophyll formation and many reactions of living

cells Tisdale et al. (1995). The results of the present study are in line with the findings of various

researchers where potato plant heights and stem shoot numbers were increased with the

application of sulfur containing fertilizers (Chettri, Mondal, and Roy, 2002; Choudhary, 2013;

Sharma, 2015).

Table 7. Effect of blended NPS fertilizer on plant height of potato varieties at Haramaya during

2018 cropping season

Blended NPS fertilizer (kg ha-1) Plant height (cm)

0 64.31c

50 65.29bc

100 68.04abc

48

150 69.2abc

200 70.96ab

250 71.24ab

300 72.41a

LSD (5%) 7.661

Mean values followed by the same letter(s) within columns had nonsignificant difference at 5%


4.3. Yield Components and Tuber Yield

4.3.1. Average Tuber Number per hill and Weight

The main effect of variety and blended NPS fertilizer and the interaction of the two factors had

significantly influenced average tuber number and average tuber weight. (Appendix Table1).

Average tuber number per hill increased as the rate of blended NPS fertilizer increased; The

highest tuber number per hill was obtained from Bubu at fertilizer application of 300 kg NPS

ha1, which was (12.73) higher than the lowest tuber number (4.03) per hill produced by Shangi

with fertilizer application of 150 kg of NPS ha-1 (Table 8). The increment due to increasing rates

of fertilizer was not more than seven tubers per hill for all the three varieties.

The increment of total tuber number per hill with increasing nitrogen fertilizer levels could be

explained by the maintenance of photo-synthetically active leaves for longer duration and the

formation of more new leaves than with lower or no nitrogen supply (Millard and Marshall,

1986). Increase in photosynthetic activity and translocation of photosynthesis to the sink might

have helped in the initiation of more tubers. As reported elsewhere, nitrogen application to

potatoes before tuber initiation increases the number of tubers per plant and mean fresh tuber

weight (Kanzikwera et al., 2001).

The current results are similar with the findings of (Mahmoodabad et al., 2010; Israel et al.,

2012; Birtukan, 2016) who reported that increasing the application of nitrogen and phosphorus

increased total tuber number per hill. In fact increasing combined application of nitrogen and

49

phosphorus from zero to full recommended NP fertilizers rate increased number of tuber per hill.

Plot treated with 200% NPSB with adjusted N ha-1 recorded highest tuber number per hill. There

are controversial reports regarding the influences of nutrition effect on potato tuber number.

Tuber number is not an important yield limiting component while studying mineral nutrition

(Lynch and Rowberry, 1997), which could be due to the inverse association between tuber

number and average tuber weight (De La Morena et al., 1994).

Increased rates of blended NPS fertilizer increased average tuber weight for all varieties. The

highest values for Belete, Bubu and Shangi was recorded (90.64 g), (71.82g) and (76.65g)

respectively at rate of 300 NPS kg ha-1 and the lowest was recorded at unfertilized plots and at

lower rates of blended NPS fertilizer application (Table 8).

The increase in average tuber weight of potato with the supply of fertilizer nutrients could be due

to more luxuriant growth, more foliage and leaf area and higher supply of photosynthesis, which

helped in producing bigger tubers, hence resulting in higher yields. In agreement with the present

finding, Mulubrhan (2004); Guler (2009); Jamaati-e-Somarin et al. (2010) and Israel et al.

(2012) have reported a significant increase in average tuber weight in response to nitrogen

application. Jamaati-e-Somarin et al. (2010) have also showed that variation in tuber yield due to

nitrogen treatments was related to the tuber weight increment. Similarly, Mulubrhan (2004) and

Israel et al. (2012) have reported that average tuber weight increased in response to the

application of phosphorus.

Table 8. Interaction effect of blended NPS fertilizer and variety on average tuber number per hill

and tuber weight of potato varieties at Haramaya during 2018 cropping season

Blended NPS

fertilizer (kg

ha-1)

Average tuber number Average tuber weight (g)

Variety Variety Belete Bubu Shangi Belete Bubu Shangi

0 9abcd 7.53abcd 4.97bcd 62.91cde 42.98e 60.87cde

50 7.78abcd 10.8abc 4.93bcd 61.21cde 69.28abcd 61.68cde

100 7.93abcd 10.27abcd 4.6cd 69.76abcd 57.03de 73.47abcd

150 7.77abcd 10.53abcd 4.03d 82.96abc 64.55cde 65.07cde

200 8.99abcd 10.3abc 5bcd 65.28cde 71.63abcd 58.39de

250 9.62abcd 11.23ab 5.23bcd 88.44ab 61.44cde 68.14bcd

50

300 12.23a 12.73a 11.01ab 90.64a 71.82abcd 76.65abcd

LSD (5%) 3.393 4.199 Mean values followed by the same letter(s) in columns and rows of each traits had nonsignificant


4.3.2. Distribution of Tubers in Different Size Categories

The proportion of large size tubers was significantly influenced by the main effect of variety and

by the interaction of two factors but not by the main effect of blended NPS factor, and small

tuber size was significantly influenced by both main effect of blended NPS fertilizer and variety

and by the interaction of the two factors. However medium tuber size was only significantly

influenced by the interaction of two factors but not by both main effect of variety and blended

NPS fertilizer (Appendix Table1).

As the rate of blended NPS rates increased, the proportion of large tuber size increased in variety

Belete, Bubu and Shangi by 37.1%, 9.2%, and 0.1% at highest rate of 300 NPS kg ha-1 fertilizer

application respectively as compared to unfertilized plots. Similarly as the rate of blended NPS

fertilizer increased, Shangi and Bubu variety increased the percent of medium tuber size by

6.21% and 1.46 % at highest rate of 300 Kg NPS ha-1 fertilizer application respectively, than

plots not received fertilizer. Whereas Belete variety decreased the percent of medium tuber size

by 8.35 % at 300 Kg NPS ha-1 fertilizer application than plots not received fertilizer (Table 9).

This could be due to the interaction of nutrients in blended fertilizer and remobilization of stored

food from tubers because of fast growth of aboveground biomass due to increased rates of

nitrogen fertilizer. It is also due to the presence of relatively better nutrient supply which results

in production of large and medium tuber production.

The results of the study are in agreement with the findings of Sharma and Arora (1987), who

found a significant increase in the yield of medium and large tuber sized due to N application.

This result also agrees with the results reported by Tafi et al. (2010) that the production of large

sized tubers and medium sized tubers increased due to less competition for nutrients and

moisture. Many researchers reported that applied phosphorus increased the proportion of large

tubers harvested (Benepal 1967; Freeman et al., 1998). Other researchers observed the increase

51

in the number of small tubers was offset by a decrease in number of large tubers (Jenkins and

Ali, 2000; Rosen and Bierman, 2008).

As the rate of blended NPS fertilizer increased, the percent of small size tubers decreased by

16.77%, 15.13% and 5.74% at highest rate of 300 Kg NPS ha-1 fertilizer application for Belete

Bubu and Shangi respectively, as compared to unfertilized plots (Table 9). Generally, the present

result showed that increasing the rate of blended NPS fertilizer application decreases the

proportion of small-size tubers. This indicates that phosphorus is a critical nutrient in

determining tuber size of potato varieties. This may be attributed to the enhanced metabolic role

the nutrient plays in tuber cell growth and development (Marschner, 1995). The result of the

present finding similar with authors, Sharma and Arrora (1987) who stated that increased in

yield of tubers with increase in applied nitrogen was associated with increases in the number of

tubers in the medium and large categories at the expense of the small ones due to increase in the

weight of individual tubers.

Table 9. Interaction effect of blended NPS fertilizer and variety on proportion of large, medium

and small size tubers at Haramaya during 2018 cropping season

Blended NPS

(kg ha-1)

Large size tubers (%) Medium size tubers (%) Small size tubers (%)

Belete Bubu Shangi Belete Bubu Shangi Belete Bubu Shangi

0 43.72c 65.7abc 72ab 23.47ab 17.84bcde 13.38de 20.88a 19.22a 10.7b

50 71.53ab 64.3abc 76.1ab 17.42bcde 19.04abcde 16.43cde 10.3b 10.3b 7.48bcd

100 68.3abc 79.7ab 69.7ab 20.9abc 13.21de 15.42cde 10.48b 7.18bcd 9.93bc

150 72.4ab 76.9ab 54.8bc 20.69abc 16.27cde 19.66abcd 5.8bcdef 6.54bcde 6.44bcde

200 86.1a 78.5ab 73.6ab 12.28e 17.66bcde 24.7a 1.32f 3.83def 1.6ef

250 74.4ab 77.1ab 73.7ab 16.63cde 18.34abcde 20.92abc 8.38bcd 4.61def 5.08cdef

300 80.8a 74.9ab 72.1ab 15.12cde 19.3abcd 19.59abcd 4.11def 4.09def 4.96def

LSD (5%) 13.44 6.765 2.623

Mean values followed by the same letter(s) in columns and rows of each traits had nonsignificant


4.3.3. Marketable, Unmarketable and Total Tuber Yield

Marketable tuber yield and total tuber yield was significantly influenced both by main effect of

blended NPS fertilizer and variety but, not significantly influenced by interaction of the two

52

factors. Moreover unmarketable tuber yield was significantly influenced by both main effects of

variety and blended NPS fertilizer and interaction of the two factors (Appendix Table 1).

Increasing blended NPS fertilizer application generally increased marketable tuber yields and

total tuber yields of the tested potato varieties. The highest marketable tuber yield and total tuber

yields of 30.74 t ha-1and 32.25 t ha-1 was recorded at the rate of 300 kg NPS ha-1 fertilizer

application respectively. But the lowest marketable tuber yield and total tuber yield of 18.24 t ha-

1 and 24.03 t ha-1 was recorded from unfertilized plots respectively (Table10).

Results of the present study revealed that application of blended NPS fertilizer increase

marketable and total tuber yields of Potato varieties. The increased in yield of tubers with

increase in applied nitrogen was associated with increases in the number of tubers in the medium

and large categories at the expense of the small ones due to increase in the weight of individual

tubers (Sharma and Arrora, 1987). Potato yield increment could be due to increment in

metabolism rate by the supplied nitrogen to the plant, where more carbohydrate is synthesized,

which might have increased tuber weight and, thus, increased total and marketable yields.

Similar to the result of the present study, Abraha et al. (2013) have also observed significant

increment in yield of bulbs of onion by applying blended fertilizer. The results are generally in

agreement with the findings of different researchers who reported positive response of potato

varieties for tuber yields with increasing levels of NPS fertilizer rates at different areas (Abewa

and Agumas, 2012; Boke, 2014; Jemberie, 2017; Mekashaw, 2016). Positive influence of NPS

fertilizer and other sulfur-containing fertilizer at optimum level have been also recorded on

various vegetable crops (Gebremeskel, 2016; Yayeh et al., 2017; Yosef, 2016,). Application of

sulfur containing fertilizers like NPS improves availability of micronutrients by amending the

soil pH (Marschner, 1995) that may in turn increase yields of vegetable crops including potato.

The varieties exhibited differential yielding ability in the study area. Belete and Bubu produced

significantly higher total tuber yield (32.41 and 31.07 t ha-1) than Shangi (15.98 t ha-1) varities.

Similarly Bubu, and Belete produced highest Marketable tuber yield (29.52, 29.48 t ha-1),

respectively, than Shangi (14.30 t ha-1) varieties (Table 10).

53

The variation in total yield of potato genotypes may be due to differences in response to the

growing environmental factors. This is in agreement with finding of other authors, who reported

that yield differences among genotypes were attributed both to the inherent potential of

genotypes and growing environment as well as to the interaction of genotype x environment

(Asmamaw, 2007; Elfinesh, 2008, Habtamu et. al., 2016).

Table 10. Main effect of blended NPS fertilizer and variety on marketable and total tuber yield at


Blended NPS fertilizer

(kg ha-1)

Marketable tuber yield

(t ha-1)

Total tuber yield

(t ha-1)

0 18.24c 23.77b

50 23.31bc 24.85b

100 24.74b 26.08b

150 24.32b 25.61b

200 22.90bc 24.82b

250 26.78ab 28.10ab

300 30.7a 32.16a

LSD (5%) 4.008 4.021

Variety

Bubu 29.52a 31.98a

Belete 29.48a 32.41a

Shangi 14.30b 15.98b

LSD (5%) 2.624 2.633

Mean values followed by the same letter(s) within columns had nonsignificant difference at 5%


54

The highest unmarketable tuber yield of Belete (6.70 t ha-1), Shangi (5.12 t ha-1) and Bubu (4.77 t

ha-1) was obtained from the plots that did not receive fertilizer application (Table 11). The result

shows those unmarketable tuber yields were decreased significantly when the rate of blended

NPS rate was increased. This may due to the decreased the level of phosphorus, might have

decreased the growth above ground biomass, tuber growth, leading to reduced tuber size and

there by high unmarketable tuber yield.

In this experiment, unmarketable tuber refers to diseased, insect attacked and undersized tubers

(less than 20 g). Thus, most of the tubers that were discarded as unmarketable tubers included the

ones that were too small in size and rotten. This indicates that factors that increase percentages of

small sized tubers would significantly increase unmarketable tuber yield. Small-sized tubers can

be unmarketable and their increment in number would significantly increase unmarketable tuber

yields. Highly and positive association were reported between the proportion of small sized tuber

yield and unmarketable tuber yield (Helen, 2012). Unmarketable tuber yield might be controlled

more importantly by manipulating other factors such as disease incidence, harvesting practice,

etc. other than mineral nutrition (Berga et al., 1994).

Table 11. Interaction effect of blended NPS fertilizer and variety on unmarketable tuber yield at


Blended NPS

fertilizer (kg ha-1)

Variety

Belete Bubu Shangi

0 6.70a 4.77b 5.12b

50 2.88cd 0.64gh 1.10fgh

100 1.38fgh 1.34fgh 1.31fgh

150 2.08cdef 0.72gh 1.09fgh

200 1.79defg 1.55efgh 0.93fgh

250 2.64cde 0.56h 0.78gh

300 3.09c 1.28fgh 1.39fgh

LSD (5%) 0.6514

Mean values followed by the same letter(s) in columns and rows of each trait had nonsignificant


55

4.4. Tuber Quality Related Traits

The analysis of variance result revealed that both the main effect of blended NPS rate and variety

and their interaction did not significantly influence dry matter, specific gravity and starch content

of potato tubers (Appendix Table 1). The result was in agreement with the findings of Sparrow

et al.(1992) that observed nonsignificant reduction in percent dry matter of tubers due to

increased P2O5 application and Zelalem et al. (2009) who have suggested that phosphorus

fertilization did not significantly influence tuber specific gravity and dry matter content.

4.5. Partial Budget Analysis

The two varieties, Bubu and Belete produced the lowest marketable tuber yield of 17.42 and

24.68 t ha-1, respectively, while Shangi produced lowest MTY (t ha-1) at 150 kg ha-1 NPS

fertilizer. Bubu, Belete and Shangi varieties produced the higher marketable yield of 37.29,

35.82 and 19.1 t ha-1, respectively, at application of highest rates of 300 kg ha-1 NPS fertilizer

(Appendix Table 12). Bubu, Belete and Shangi varieties had marketable tuber yield advantage of

114.06, 105.63 and 51.32%, respectively, at 300 kg ha-1 NPS fertilizer over yield obtained

without fertilizer application. The marketable tuber yields advantage of Bubu and Belete

varieties increased linearly starting 100 kg ha-1 NPS fertilizer over yields produced without

fertilizer application except MTY of Bubu and Belete at 100 and 200 kg ha-1 NPS fertilizer,

respectively (Table 12).

Table 12. Percent advantage of marketable tuber yield due to blended NPS fertilizer over potato

production without fertilizer at Haramaya in 2018

Blended NPS kg ha-1 Bubu Belete Shangi

56

50 67.53 53.16 11.52

100 58.53 58.96 -89.41

150 83.79 70.84 -11.46

200 81.57 60.16 16.46

250 80.54 94.20 19.41

300 114.06 105.63 51.32

The highest marginal rate of return (MRR) of 18.02 (1802.35%) followed by 15.88 (1587.78%)

and 14.34 (1434.17%) obtained from Bubu variety with the application of 50, 150 and 300 kg ha-

1 NPS fertilizer, respectively. The lower MRR of 10.97 (1097.1%) obtained from Bubu with the

application of 250 kg ha-1 NPS fertilizer. The tubers production of Belete with the application of

300 and 250 kg ha-1 NPS fertilizer had MRR of 7.6 (760.27%) and 6.81 (680.91%), respectively.

The lowest MRR of 2.07 (207.11%) obtained from Belete variety with application of 200 kg ha-1

NPS fertilizer. On the other hand, <1 (100%) MRR was obtained from Shangi with the

application of 100, 150 and 200 kg ha-1 NPS fertilizer. The MRR of 1.09 (109.09%), 1.35

(135.1%) and 4 (400.15%) obtained from Shangi with 250, 50 and 300 kg ha-1 NPS fertilizer,

respectively (Table 13). The results of cost benefit analysis indicated that the farmers could

obtain a minimum and maximum of 2.07 and 18.02 Birr, respectively, from Belete and Bubu

varieties when farmers cost 1 Birr for fertilizer purchasing. This suggested that the application of

fertilizer on the two varieties was acceptable since if farmers obtained additional 1 Birr (100%)

from the input cost 1 Birr. (However, the application of 100-200 kg ha-1 NPS fertilizer on Shangi

variety did not satisfy farmers since the farmers could not obtain additional 1 Birr (100%) by 1

Birr cost of the application of NPS fertilizer.

The benefit-cost ratio of Bubu variety with all rates of NPS fertilizer not lower than the benefit-

cost ratio of the variety without application of fertilizer, however, the benefit-cost ratio of Belete

and Shangi varieties with all rates of NPS fertilizer was lower than the benefit-cost ratio of the

varieties without application of fertilizer (Table 13). The highest MRR of 18.02 (1802.35%) was

also obtained from Bubu variety with the application of the lowest rate (50 kg ha-1) of NPS

fertilizer suggested the production of tubers from Bubu variety with lowest rate of fertilizer

application seem benefit more than other rates of fertilizer application and production of the

other two varieties. However, the producers not only focused the maximum MRR by introducing

new technologies but also the magnitude of net benefit (NB). In this regard the highest NB of

57

166175.5 Birr ha-1 was computed for Bubu variety with the application of highest NPS fertilizer

rates of 300 kg ha-1, the second and third higher NB of 158899 and 149658.5 Birr ha-1 obtained

from Belete with the application of 300 and 250 kg ha-1 NPS fertilizer, respectively.

The relationship between the application of NPS fertilizer (kg ha-1) and net benefit (Birr ha-1)

obtained from three potato varieties indicated that as the rates of fertilizer increased so did the

magnitude of net benefit from Bubu and Belete varieties. The magnitude of net benefit from

Bubu and Belete varieties was determined by the application of NPS fertilizer. The net benefit

obtained from Bubu and Belete varieties was determined by about 72.06 (R2=0.07206) and

81.92% (R2=0.08192), respectively, with the application of NPS fertilizer. However, the net

benefit obtained from Shangi variety was determined by about 35.79% (R2=0.03579). The net

benefit obtained from Bubu and Belete varieties and application of NPS fertilizer had positive

and strong correlation (r=0.8489 and r=0.9051) and the relationship was linear and significant,

but this is not true in the production of Shangi variety (Figure 1). The highest NB of 166175.5

Birr ha-1 followed by 158899 Birr ha-1 was computed from Bubu and Belete varieties,

respectively, with the application of highest NPS fertilizer rate of 300 kg ha-1. The two varieties;

Bubu and Belete also had acceptable MRR of 1434.17 and 760.27%, respectively, with the

application of highest NPS fertilizer rate of 300 kg ha-1. Therefore, the growing of Bubu and as

second option Belete variety with the application of highest NPS fertilizer rate could be

recommended in the study area.

According to CIMMYT (1988), the minimum acceptable marginal rate of return should be

between 50% and 100%. The current study indicated that the marginal rate of return was found

to be >207.11% for all treatment combinations of NPS fertilizer rates (50-300 kg ha-1) with Bubu

and Belete varieties and the chance of obtaining higher net benefit (Birr) was towards to higher

rates of fertilizer. This suggested the production of tubers from these two varieties at higher rates

of NPS fertilizer could be attractive for producers because of the high economic returns.

Table 13. Partial budget analysis of seven rates of blended NPS fertilizer in combination with

three potato varieties at Haramaya in 2018

Blended

NPPS

(kg ha-1) Variety

AMTY

(kg ha-1)

AdMTY

(kg ha-1)

GFB

(Birr)

TVC

(Birr)

NB

(Birr) MRR MRR (%) BCR

0 Bubu 17423.333 15681 86245.5 12000 74245.5 6.19

58

50 Bubu 29183.333 26265 144457.5 15060 129397.5 18.02 1802.35 8.59

100 Bubu 27616.667 24855 136702.5 15670 121032.5 12.75 1274.85 7.72

150 Bubu 32016.667 28815 158482.5 16280 142202.5 15.88 1587.78 8.73

200 Bubu 31630 28467 156568.5 17190 139378.5 12.55 1254.97 8.11

250 Bubu 31450 28305 155677.5 17800 137877.5 10.97 1097.10 7.75

300 Bubu 37290 33561 184585.5 18410 166175.5 14.34 1434.17 9.03

0 Belete 24680 22212 122166 12000 110166 9.18

50 Belete 26680 24012 132066 15060 117006 2.24 223.53 7.77

100 Belete 27690 24921 137065.5 15670 121395.5 3.06 305.98 7.75

150 Belete 29760 26784 147312 16280 131032 4.88 487.52 8.05

200 Belete 27900 25110 138105 17190 120915 2.07 207.11 7.03

250 Belete 33830 30447 167458.5 17800 149658.5 6.81 680.91 8.41

300 Belete 35820 32238 177309 18410 158899 7.60 760.27 8.63

0 Shangi 12620 11358 62469 12000 50469 4.21

50 Shangi 14073.333 12666 69663 15060 54603 1.35 135.10 3.63

100 Shangi 13360.333 12027 66148.5 15670 50478.5 0.00 0.26 3.22

150 Shangi 11173.333 10056 55308 16280 39028 -2.67 -267.31 2.40

200 Shangi 14696.667 13227 72748.5 17190 55558.5 0.98 98.06 3.23

250 Shangi 15070 13563 74596.5 17800 56796.5 1.09 109.09 3.19

300 Shangi 19096 17187 94528.5 18410 76118.5 4.00 400.15 4.13

AMTY (kg ha-1) =Average Marketable Tuber Yield, AdMTY (kg ha-1) =Adjusted Marketable

Tuber Yield, GB (Birr) = Gross Benefit, TVC (Birr) = Total Variable Cost, NB (Birr) = Net

Benefit, MRR= Marginal Rate of Return, MRR (%) =Percentage of Marginal Rate of Return,

BCR= Benefit Cost Ratio.

Purchasing cost of blended NPS fertilizer and Urea were estimated at Birr 12.2 kg ha-1 and 14

Birr per kilogram, respectively. For one time application of 50-150 and 200-300 kg fertilizer cost

350 and 500 Birr, respectively. The other cultivation cost per hectare was estimated 12000 Birr

for all plots considering the cost differences of cultivation for plots received different rates is

negligible. Sale price of marketable tubers was 5.50 ETB kg-1 for all varieties during the

harvesting time.

59

Figure 1. Scatter plot showing the relationship between the application of NPS fertilizer (kg ha-1)

and net benefit (Birr ha-1) obtained from three potato varieties.

5. SUMMARY AND CONCLUSION

Potato (Solanum tuberosum L.) is an important food and export crop in East Hararghe. The

limiting macro and micronutrients were identified for the production of crops in Haramaya

districts, but the rates of these nutrients for high potato yield are not yet determined. Therefore,

this research was conducted to determine the effect of blended NPS fertilizer rates on yield, yield

related and tuber quality related traits of potato varieties, and to estimate economically feasible

blended NPS fertilizer rate for potato production at Haramaya, East Hararghe.

60

Three potato varieties, namely Bubu (CIP-384321.3), Belete (CIP-393371.58) and Shangi were

used in this experiment in 2018 cropping season as experimental material. Seven rates of blended

NPS fertilizer (0, 50, 100, 150, 200, 250 and 300 kg ha-1) was used. The experiment was tested in

factorial arrangement in randomized block design with three replications. The experiment was

conducted at Raare, in Haramaya, East Hararghe, Oromia Zone, and Eastern Ethiopia during

2018 main cropping season.

The results revealed that days to 50% maturity, plant height, marketable tuber yield, and total

tuber yield were significantly affected by the main effects of blended NPS rates and potato

variety. Significantly delayed 50% maturity (91.78 days) and tallest plant height (72.41cm)

recorded at highest (300 NPS kg ha-1) rate of fertilizer. The highest marketable tuber yield (30.74

t ha-1) and total tuber yield (32.16 t ha-1) was recorded at rate of (300 NPS kg ha-1). But Days to

50% emergency and main stem number was significantly affected only by main effect of variety.

Bubu took the least days to 50% emergence (12.9 days) over the other two varieties while Belete

and Shangi took the longest days to 50% emergence (13.24 days) and (13.81days) respectively

without significant difference between the latter two. Belete and Bubu produced significantly

higher number of main stems (6.75, 5.31) per hill respectively than Shangi (3.09).

The interaction of blended NPS rate and potato variety also significantly affected days to 50%

flowering, average tuber number, average tuber weight, large tuber size, medium tuber size,

small tuber size and unmarketable tuber yield. Significantly delayed 50% flowering of Belete

(53.33 days), Bubu (55 days), and Shangi (57 days) was recorded at highest (300 NPS kg ha-1)

rate of fertilizer. Highest average tuber number of Belete (12.27), Bubu (12.73) and Shangi

(11.01) was recorded at rate of (250,200,300 NPS kg ha-1) of fertilizer application without

significant difference among them. The highest average tuber weight of Belete (90.64g), and

Bubu (71.82g) was recorded at highest rate of (300 NPS kg ha-1), and (76.65g) was recorded for

Shangi at rate of (200 NPS kg ha-1) fertilizer. The highest proportion of large tuber size (80.8%)

were obtained from Belete variety interacted with (300 NPS kg ha-1) fertilizer application, while

the highest proportion of medium (24.7%) were obtained from Shangi variety at rate of (200

NPS kg ha-1) and small tuber size (20%) were obtained from Belete varieties, without fertilizer

application. But all quality parameters (dry matter, specific gravity and starch content) were not

significantly affected by neither main effect of both factors nor the interaction of two factors.

61

The economic analysis revealed that, the application of highest rates of 300 kg ha-1 NPS fertilizer

produced the higher marketable yield of 37290, 35820 and 19096 kg ha-1 from Bubu, Belete and

Shangi varieties, respectively. The relationship between the application of NPS fertilizer

(kg ha-1) and net benefit (Birr ha-1) obtained from three potato varieties indicated that as the rates

of fertilizer increased so did the magnitude of net benefit from Bubu and Belete varieties.

The net benefit obtained from Bubu and Belete varieties was determined by about 72.06

(R2=0.07206) and 81.92% (R2=0.08192), respectively, with the application of NPS fertilizer.

However, the net benefit obtained from Shangi variety was determined by about 35.79%

(R2=0.03579). The net benefit obtained from Bubu and Belete varieties and application of NPS

fertilizer had positive and strong correlation (r=0.8489 and r=0.9051) and the relationship was

linear and significant, but this is not true in the production of Shangi variety. The highest NB of

166175.5 Birr ha-1 followed by 158899 Birr ha-1 was computed from Bubu and Belete varieties,

respectively, with the application of highest NPS fertilizer rate of 300 kg ha-1. The two varieties;

Bubu and Belete also had acceptable MRR of 1434.17% and 760.27%, respectively, with the

application of highest NPS fertilizer rate of 300 kg ha-1. Therefore, the growing of Bubu and as

second option Belete variety with the application of (300 NPS kg ha-1) highest fertilizer rate

could be recommended in the study area. However, since the experiment was conducted for one

season at one location, it suggested that the experiment has to be repeated over seasons and

locations using this and other improved potato varieties in order to give a comprehensive

recommendation.

6. REFERENCE

Abewa Aregahagn and Birhanu Agumas. 2012. Response of irrigated potato (Solanum tuberosum L.) to

nitrogen fertilizer at Koga Irrigation Scheme, West Gojjam. In Gizaw, D. (Eds), Proceedings of

the First Workshop on Agricultural Water Management Research and Development in Amhara

Region. Bahir Dar, Ethiopia.

Abraha Gebrekiros, Solomon Habtu and Yirga Weldu. 2013. Response of onion (Allium cepa L.) growth

and yield to different combinations of N, P, S, Zn fertilizers and compost in northern Ethiopia.

International Journal of Science and Research Index Copernicus Value, 6:14

62

Adane Hirpa, Miranda, P.M., Agajie Tesfaye, Willemien, J.M. Lommen, Alfons OudeLansink, Admasu

Tsegaye and Paul, C.S. 2010. Analysis of Seed Potato Systems in Ethiopia. American Journal of

Potato Research, 87: 537-552.

Adhikari, R. C., and Sharma, M. D. 2004. Uses of chemical fertilizers on potatoes in sandy loam soil

under humid sub-tropical condition of Chit wan. Nepal Agric. Res. J, 5(4), 123- 126.

Admire A.R., Dangler, L.A., Crawford, G.B., Uslu, B.U., Borrero, J.C., Greer, S.D. and Wilson, R.I.,

2014. Observed and modeled currents from the Tohoku-oki, Japan and other recent tsunamis in

northern California. Pure and Applied Geophysics, 171(12), 3385-3403.

AGP (Agriculture Growth Program). 2013. From sample blended fertilizers to ample yields. Retrieved

from http://ethioagp.Org/from-sample-blended-fertilizers-to-ample-yields/.

Alemayehu Tilahun, Nigussie Dechassa and Tamado Tana. 2015. Response of Potato (Solanum

tuberosum L.) Yield and Yield Components to Nitrogen Fertilizer and Planting Density at

Haramaya, Eastern Ethiopia. Journal of Plant Sciences, 3(6): 320- 328.

Allen, E. J. 1978. Plant density: In the potato crop: The scientific basis for improvement of the potato

crop. Harris, P. M. (Eds), Champman and Hall,

Allison, M.F., Fowler, J.H. and Allen, E.J. 2001. Factors affecting the magnesium nutrition of potatoes

(Solanum tuberosum L). Journal of Agricultural Science, 137: 397-409.

Asmamaw Yeshanew. 2007. Postharvest quality of potato (Solanum tuberosum L.) cultivars as

influenced by growing environment and storage period. An M.Sc. Thesis presented to the School

of Graduate Studies of Haramaya University, Ethiopia, pp. 41-44.

Asrat Amele. 2014. Improving the process of potato breeding in east Africa.

Assefa Nuru. 2005. Response of two improved potato (Solanum tuberosum L.) varieties to nitrogen and

phosphorus application. An MSc thesis presented to the School of Graduate Studies of Harmaya

University, Ethiopia. 101p.

Astley, S.B. 2003. Dietary antioxidants past, present and future. Food Science and Technology Journal,

14: 93-98.

Atkinson, D., B. Geary, J. Stark, S. Love and J. Windes, 2003.Potato Varietal Responses to Nitrogen

Rate and Timing. Presented at the Idaho Potato Conference, January 22, 2003.

Babuchowski k. 1971. Study of the effect of sulfur fertilization on the technological value of seeds,

rapeseed meal and oil.Zesz.Nauk. WSR Olszt, 5 Suppl. A, ss. 52. (In Polish).

http://ethioagp/

63

Baligar, V. C. and Bennelt, O. L. 1986. Outlook on fertilizer use efficiency in the tropics. Fertilizer

Research, 10: 83-96.

Barber, J. 1995. Nutrient deficiency and symptoms of plant. 2nd edition. London:

Barczak . Nowak K. 2015.Effect of sulphur fertilization on the content of macro elements and their ionic

ratios in potato tubers. J. Elem., 20 (1): 37-47. DOI: 10.5601/jelem.2014.19.1.471.

Baye Berhanu and Gebremedhin Woldegiorgis. 2013. Potato variety development strategies and

methodologies in Ethiopia. In: Gebremedhin Woldegiorgis, S. Schulz and Baye Berhanu (Eds.).

Bekele Kassa and Gebremedhin G, 2000. Effect of planting dates on late blight severity and tuber yield

of different potato varieties. Pest Management Ethiopia Journal.41 (1-2): 51-63.

Bekele Kassa and Hailu Beyene. 2001. Efficacy and economics of fungicide spray in the

control of late blight of potato in Ethiopia. Code Number: CS01054. African Crop

Science Journal, 9 (1): 245-250.

Belay Semane, WortmannW. and HoogenboomG. 1998. Haricot bean agro ecology in Ethiopia:

definition using agro climatic and crop growth simulation models. African Crop Journal. 6 (1):

9–18.

Benedycka Z. 1983. Response of radish to potassium chloride versus potassium sulphate under field

conditions. Part II. Effect on chemical composition. Zesz. Nauk. ART Olszt. Rol. 36: 205-212.

(in Polish).

Benepal, P. S. 1967. Interrelations among plant nutrients application levels on yield of potatoes.

American Potato Journal, 44(6), 187–194.

Bereke Tsehai., 1988. Potato research and future improvement prospects. Proceedings of the 19th

National Crop Improvement Conference, April 22-26, 1987, Institute of Agricultural Research,

Adis Ababa, Ethiopia.

Berga Lemaga, Gebremedhin Woldegiorgis, Teriessa Jalleta and Bereke Tsehai Tuku. 1994.

Horticulture Research and development in Ethiopia. pp. 101-119. In: Edward, H. and Lemma

Desalgne (eds.), Proceedings of the 2nd National Horticulture Workshop of Ethiopia, 1-3 Dec.

1992.

Beukema, H.P., and VanderZaag, D.E. 1990. Introduction to Potato Production. PudocWageningen,

Netherlands. pp 92-95.

64

Beyene Getu. 1998. Yield, quality and nitrogen uptake of potato (Solanum tuberosum L) as influenced

by rate and time of N application (MSc thesis). Alemaya University, Ethiopia.

Bezabih Emana and Mengistu Nigussie. 2011. Potato Value Chain Analysis and Development in

Ethiopia: Case of Tigray and SNNP Regions. International Potato Centre (CIP), Ethiopia.

Birch, P.R.J., Bryan, G., Fenton, B., Gilroy, E., Hein, I., Jones, J.T., Prashar, A., Taylor, M.A.,

Torrance, L. and Toth, I.K. 2012. Crops that feed the world. Potato: are the trends of increased

global production sustainable? Food Security 4:477-508.

Biswas, T.D., and Mukherjee, S.K. 1993. Text Book of Soil Science. 5th (Eds.). Tata Mc Graw.

Boke, S. 2014. Effects of organic and inorganic fertilizer application on potato yield and soil properties

on Alisols of Chencha. Africa Journal of Science, 2(8), 123-132.

Boreczek b. 2001. The use of plant tests for the estimation of plants sulphur supply. Fragm.Agron.

18(4): 136-146. (In Polish).

Bowen, W.T., 2003.Water productivity and potato cultivation. Available on-line at

http://www.iwmi.cgiar.org/pubs/Book/CA_CABI_Series/Water_Productivity/Protected/0

51996698ch14.pdf.Accessed on 27 April 2011.

Brady, N.C and R.R . Weil, 2002. The nature and properties of soil. 13th (Eds). Person Education Ltd.

USA.621p.

Birtukan Belachew.2016. Effect of nitrogen and phosphorus rates on growth, yield, yield components

and quality of potato (Solanum tuberosum L.) at Dedo, South West Ethiopia. An M.Sc Thesis

Presented to School of Graduate Study of Jimma University, Ethiopia.

Burton, W.G. 1966. The Potato; a Survey of Its History and of the Factors Influencing Its Yield,

Nutritive Value, Quality and Storage.Veenmand and Sonen, N.V, Wageningen. 521p.

CSA (Central Statistical Agency) 2009. Agricultural Sample Survey 2009/2010. Volume I. Report on

area and production of crops: Private peasant holdings, Meher season. Statistical Bulletin 446.

Addis Ababa.

CSA (Central Statistic Agency). 2016 .Agricultural sample survey: Area and production of major crops.

Addis Ababa: Central Statistic Agency.

Chapman, T., 1965. Experiments with Irish potatoes (Solanum tuberosum L.) in Trinidad. Tropical

Agriculture, (Trin.) 42: 189-197.

http://www.iwmi.cgiar.org/pubs/Book/CA_CABI_Series/Water_Productivity/Protected/0

65

Chettri, M., Mondal, S., and Roy, B. 2002. Influence of potassium and sulphur with and without FYM

on growth, productivity and diseases index of potato in soil of West Bangal. Journal of Indian

Potato Association, 29(3), 61–69.

Choudhary, R. 2013. Impact of nitrogen and sulfur fertilization on yield, quality and uptake of nutrient

by Maize in Southern Rajasthan. Annals of Plant and Soil Research, 15(2), 118–121.

CIMMYT (Centro International de Majoramento de Maize Y Trigo).1988. Farm Agronomic to farmer’s

recommendation. An Economic Training Manual. Completely revised edition.D.F.Mexico.51p.

CIP. 2010. The contribution of potatoes to global food security. International potato center. September

2010.Europe.

Cole, C.S. 1975. Variation in Dry matter between and within potatoes. Potato Res.18:28-37.

CSA (Central statistical agency). 2014. Agricultural sample survey 2013/2014. Vol. III. Report on farm

management practices (private peasant holdings, meher season). Statistical Bulletin 532, Central

Statistical Agency. Addis Ababa, Ethiopia.

CSA (Central statistical agency). 2017. Agricultural sample survey 2016/2017. Vol. I. Report on farm

management practices (private peasant holdings, meher season). Statistical Bulletin 584, Central

Statistical Agency. Addis Ababa, Ethiopia.

Cucci, G., and Lacolla, G. 2007. Effects of different fertilizing formulae on potato. Italian Journal of

Agronomy, 2(3), 275-280.

Dela Morena, I., Guillén, A., and Del Moral, G. L. F. 1994. Yield development in potatoes as influenced

by cultivar and the timing and level of nitrogen fertilizer. American Potato Journal, 71, 165–173.

Dandena. 2013, Term paper on Potato (Solanum tuberosum L.) Seed Production Technology.

Dewis, J., and Freitas, P.1975. Physical and Chemical Methods of Soil and Water Analysis. FAO.

Bullet, Rome, 10: 275.

Dubetz, S., and Bole, J. B. 1975. Effect of nitrogen, phosphorus, and potassium fertilizers on yield

components and specific gravity of potatoes. American Potato Journal, 52(12), 399-405.

Eddins, A.H., 1934. Effect of inoculated sulphur, lime and mercury compounds on the yield of

potatoes. Am. J. Potato Res., 11: 295-302.

Eshetu Mulatu, O. Ibrahim and E. Bekele, 2005a. Improving potato seed tuber quality and producers

livelihoods in Hararghe, Eastern Ethiopia. New Seeds Journal. 7(3): 31-56.

66

Eshetu Mulatu, O. Ibrahim and E. Bekele, 2005b. Policy challenges to improve vegetable production and

seed supply in Hararghe, Eastern Ethiopia. Vegetable Science Journal 11(2): 81-106.

Ewing, E.E. 1997. Potato. In: The Physiology of Vegetable Crops (ed.), CAB International, U.K.PP,

295-344.

EIAR (Ethiopian Institute of Agriculture Research). 2003. Potato production guide. (un published).

EIAR (Ethiopian Institute of Agricultural Research). 2016. National Potato Research Program, Research

Project for the Period 2017-2019 GC. January 2017, Addis Ababa.

Elfinesh Firdissa. 2008. Processing Quality of Improved potato (Solanum tuberosum L.) Varieties as

Influenced by Growing Environment, Genotype and Blanching. MSc. Thesis submitted to school

of plant sciences, Haramaya University, Ethiopia.

Ellis, B., and Foth, H. 1996. Soil fertility.CRC Press.

Eppendorfer, W.H. and B.O. Eggum, 1994b. Sulphur deficiency of potatoes as reflected in chemical

composition and in some measures of nutritive value. Norwegian J. Agric. Sci., 15:127-134.

Eshetu Mulatu, Ibrahim, O. and Etenesh Bekele 2005b. Policy changes to improve vegetable production

and seed supply in Hararghe, Eastern Ethiopia. Vegetable Science Journal, 11(2):81–106.

Ethiopia Institute of Agricultural Research. 2007. Crop Technologies Guideline. Addis Ababa:

Ethiopian Institute of Agricultural Research.

EthioSIS (Ethiopian Soil Information System). 2014. Soil Fertility Status and Fertilizer recommendation

Atlas for Tigray Regional State. ATA, Addis Ababa, Ethiopia.

Fairhust, T., Lefroy, R., Mutert, E., and Batjes, N.1999.The importance, distribution and causes of

phosphorus deficiency as a constraint to crop production in the tropics. In Agro forestry Forum

(Vol. 9, No. 4, 2-8).

FAO (Food and Agricultural Organization of the united Nation). 2001. Agricultural Investment and

Productivity in Developing Countries. Economic and Social Development paper, 148, Rome,

Italy.

FAO (Food and Agriculture Organization of the Unite Nation). 2000. Fertilizer and their use.4th (Eds)

International Ferilizer Industry Association. Food and Agricultural organizationof the United

Nations. Rome Italy.FAO (Food and Agriculture Organization). 2008. Potato World: Africa-

International Year of the Potato.

67

FAO (Food and Agriculture Organization). 2006. Plant nutrition for food security: A guide for

integrated nutrient management. FAO, Fertilizer and Plant Nutrition Bulletin 16, Rome.

FAO (Food and Agriculture Organization). 2009. International year of the potato

2008. Newlightona hidden treasure. An end-of-year review. International year of the

potato to 2008. Food and Agricultural Organization of the united Nation, Rome 2008.

FAO (Food and Agriculture Organization). 2010. World food and Agricultural Organization data of

statistics. Rome, Italy. Accessed on June, 2012.

FAOSTAT (Food and Agricultural Organization Statistic). 2010. World food and agricultural

organization data of statistics. Rome, Italy. FAO, Bulletin, Rome, 10:275.

FAOSTAT. 2017. Statistical database. Rome: Food and Agricultural Organization of United Nations.

FAOSTAT. 2015. Statistical database. Rome: Food and Agricultural Organization of United Nations.

Firew Gebremariam, Nigussie Dechassa and Wassu Mohammed. 2016. Response of potato (solanum

tuberosum L.) to the application of mineral nitrogen and phosphorus under irrigation in Dire

Dawa, Eastern Ethiopia. Journal of Natural Sciences Research. ISSN 2224-3186 (Paper) Vol.6,

No.7, 2016.

Fitzpatrick, J.J., Porter, W.L. and Houghland, V.C. 1969. Continued studies of the relationship of

specific gravity to total solids of potato. American Potato Journal, 46: 120-127.

Freeman, K.L., P.R. Franz and R.W. de Jong, 1998. Effect of phosphorus on the yield, quality, and petiolar

phosphorus concentrations of potatoes (cv. Russet Burbank and Kennebec) grown in the krasnozem

and duplex soils of Victoria. Australian Exp. Agri. Journal, 38: 83-93.

Gardner, B.R., Jones, J.P. 1975. Petiole analysis and the nitrogen fertilization of Russet Burbank

potatoes. American Potato Journal, 52:195-200.

Gebremedhin W/Giorgis and Bekele Kassa. 2000. Effect of planting date on late blight severity and

tuber yields of different potato varieties. Pest Mgt. J. Eth. (1and2):51-63.

Gebremedhin Woldegiorgis, Endale Gebre, Kiflu Bedane, Bekele Kassa. 2001. Country Profile on

Potato Production and Utilization: Ethiopia. Ethiopian Agricultural Research Organization

(EARO), Holeta Agricultural Research Centre, National Potato Research Program.

Gebremeskel, D. K. 2016. Assessment of production practices and effect of N: P2 O5: S rates on yield

and yield components of head cabbage (Brassica oleracea var. capitata) under irrigation

68

conditions in Lay Armachio District, Amhara Region, Ethiopia. (MSc Thesis). Bahir Dar

University, Ethiopia.

Getachew Tesfaye and Awole Mela. 2000. The role of SHDI in potato seed production in Ethiopia:

Experience from Alemaya integrated rural development project. Proceedings of the 5th African

Potato Association Conference, Volume 5, May 29-June 2, 2000, Kampala, Uganda,pp: 109-

112.

Getu Beyene, 1998. Yield, quality, and nitrogen uptake of potato as influenced by rate and time of

nitrogen. MSc Thesis Submitted to School of Plant Sciences, Haramaya University, Ethiopia.

Giardini, L. 1992. Effects of poultry manure and mineral fertilizers on the yield of crops. Journal of

Agricultural Sciences. 118: 207-213.

Goźliński H.1970a. Sulphur (SO4-2) fertilizing effect at different nitrogen fertilization levels. Oat and

barley trials. Rocz. Nauk Rol., a, 96(4): 133-149. (In Polish).

Gray, D. and Hughes, J.C. 1978. Tuber Quality. In: The potato Crop: The Scientific Basis for

improvement (P.M. Harris, Eds).

Grepperud, S. 1996. Population Pressure and Land Degradation: The Case of Ethiopia.

Journal of Environmental Economics and Management, 30:18-33.

Grzesiuk w. 1965. Studies on the effect of sulphur fertilization on the yield and chemical composition of

spring rape. Zesz.Nauk. WSR Olszt. 20(3): 343-355. (in Polish).

Guler, S. 2009. Effect of nitrogen on yield and chlorophyll of potato (Solanum tuberosum L.) cultivars.

Bangladish.J.Bot.38 (2):163-169.

Gulluoglu, L., and Arıoglu, H. 2009. Effects of seed size and in-row spacing on growth and yield of

early potato in a Mediterranean-type environment in Turkey.

Habtamu Gebreselassie, Wassu Mohamed and Beneberu Shimelis. 2016. Evaluation of Potato (Solanum

tuberosum L.) Varieties for Yield and Yield Components in Eastern Ethiopia. Journal of

Biology, Agriculture and Health care, 6:5.

Habtamu Terefe, Chemeda Fininsa, Samuel Sahile and Kindie Tesfaye. 2016. Effect of integrated

climate change resilient cultural practices on faba bean rust (Uromyces viciae-fabae) epidemics

in Hararghe highlands, Ethiopia. Journal of Plant Pathology & Microbiology,

7:8DOI:10.4172/2157-7471.1000373

69

Hancock, R.D., Morris, W.L., Ducreux, L.J.M., Morris, J.A., Usman, M., Verrall, S.R., Fuller, J.,

Simpson, C.G., Zhang, R., Hedley, P.E. and Taylor, M. A. 2014. Physiological, biochemical and

molecular responses of the potato (Solanum tuberosum L.) plant to moderately elevated

temperature. Plant Cell Environment, 37:439-450.

Hanley, F., Jarvis, R. and Ridgman, W. 1965. The effect of fertilizers on the bulking of Majestic

potatoes. Journal of Agricultural Science, 65: 159-169.

Harris, P. 1978. Mineral Nutrition. In: The Potato Crop: The scientific Basis for Improvement, Harris,

P.M. (Eds). Chapman and Hall, London.

Hassanpanah, D., 2010. Evaluation of potato cultivars for resistance against water deficit stress under in

vivo conditions. Potato Research. 53: 383-392.

Hassanpanah, D., Hosienzadeh, A. A., Dahdar, B., Allahyari, N., and Imanparast, L. 2009. Effects of

different rates of nitrogen and phosphorus fertilizers on yield and yield components of Savalan

potato cultivar mini-tubers. Journal of Food, Agriculture and Environment, 7(2), 415-418.

Hassel, R. L., Kelly, D. M., Wittmeyer, E. C., Wallace, C., Grassbaugh, E. M., Elliott, J. Y. and

Wenneker, G. L. 1997. Ohio potato cultivar trials.Ohio State University Horticulture Series

No.666.

Haverkort, A., Koesveld, F.V., Schepers, H., Wiljnands, J., Wustman, R.,Zhang, X. Y. 2012. Potato

prospects for Ethiopia: on the road to value addition. Lelystad: PPO-AGV, 2012 (PPO

publication 528). 66p.

Hawkes, J.C. 1990. The Potato: Evolution

Hawkes, J.C. 1990. The Potato: Evolution, Biodiversity, and Genetic Resources. Belhaven Press,

London. pp. 259.

Helen Teshome. 2012. Evaluation of agronomic performance of improved and local potato (Solanum

tuberosum L.) cultivars grown in eastern Ethiopia. MSc. Thesis submitted to school of plant

sciences, Haramaya University, Ethiopia.

Herlihy, M. and P.J. Carroll. 1969. Effects of N, P, and K and their interactions on yield, tuber Reddy,

S.N. and Rao, R.S. 1968. Response of potato to different levels of nitrogen,

phosphorus and potassium in a sandy loam soil in Hyderabad. Indian Journal of

Agricultural Sciences, 38: 577–588.

70

Hielke, De Jong, Joseph, B. Sieczka and Walter De Jong. 2011. The complete book of potatoes what

every grower and gardener needs to now.pp.11.

Hogy, P. and Fangmeier, A. 2009. Atmospheric CO2 enrichment affects potatoes: 2. Tuber quality traits.

Hopkins, B. G., Rosen, C. J., Shiffler, A. K., and Taysom, T. W. 2008. Enhanced Efficiency Fertilizers

for Improved Nutrient Management: Potato. Crop Management, 7(1), 0-0.

Horton, D. 1987. Potatoes: Production, Marketing and Programs for Developing Countries. West view

Press. Boulder.

Hossain, S.A., M.A. Hakim and J.M. Onguso, 2003. Effect of manure and fertilizers on growth and yield

of potato. Pak.j. Biol. Sci. 6(14):1243-1246.

Human, J.J. 1961. The effect of fertilizer levels on yield and specific gravity of potatoes. Biological

Abstracts. 39: 278.

IAR (Institute of Agricultural Research), 2000. Holetta Genet Research Station Progress Report, Addis

Ababa, Ethiopia.

Iritani, W.M. 1968. Factors affecting physiological ageing (degeneration) of potato.

Iritani, W. M., Thornton, R., Weller, L., and O’Leary, G. 1972. Relationships of seed size, spacing, stem

numbers to yield of Russet Burbank potatoes. American Potato Journal, 49(12), 463-469.

Israel Zewde, Ali Mohammed and Solomon Tulu. 2012. Effect of different rate of nitrogen and

phosphorus on yield and yield components of potato (solanum tuberosum L.) at Masha District,

South western Ethiopia. International Journal Soil Science, 7(4):146- 156.

Iwama, K., 2008. Physiology of the potato: New insights into root system and repercussions for crop

management. Potato Research.51 (3-4): 333-353.

Jamaati-e-Somarin, S., S. Hokmalipour., M.Shiri-e-Janagrad., A. Abbasi. 2009. Vegetative growth of

potato (Solanum tuberrosum L.) cultivars under the effects of different level of nitrogen

fertilizer. Payam Noor University, Iran. Research Journal of Biological Science 4(7):807-814.

Jamaati-e-Somarin, S., Zabihi-e-Mahmoodabad, R., & Yar, A. 2010. Response of agronomical,

physiological, apparent recovery nitrogen use efficiency and yield of potato tuber (Solanum

tuberosum L), to nitrogen and plant density. American-Eurasian J Agric Environ Sci, 9(1), 16-

21.

71

Jemberie Minwyelet . 2017. Effects of NPS fertilizer rate and irrigation frequency determination method

on the growth and tuber yield of potato (Solanum tuberosum L) in Koga Irrigation Scheme,

Northwestern Ethiopia (M.Sc. Thesis). Bahir Dar University, Ethiopia.

Jenkins, P.D. and H. Ali, 2000. Phosphorus supply and progeny tuber numbers in potato crops. Ann. App.

Biol., 136: 41-6

Jenkins, P.D. and S. Mahmood, 2003.Physiology of vegetable crops. In: nutrient use of potato.

Kabira, J.N., M., Wagoire, P., Gildemacher and B. Lemaga. 2006. Guidelines for the production of

healthy seed potatoes in East and Central Africa. Kenya Agricultural Research Institute, Nairobi,

Kenya, 28p.

Kaguongo, W., Gildemacher, P., Demo, P., Wagoire, W., Kinyae, P., Andrade, J., Forbes, G.,Fuglie, K.

and Thiele, G. 2008.Farmer practices and adoption of improved potato varieties in Kenya and

Uganda. International Potato center (CIP), Lima, Peru. Social Sciences Working Paper, 2008-5.

85 p

Kandi, M.A.S., A.Tobeh, A. Gholipoor, S. Jahanbakhsh, D. Hassanpanah and O. Sofalian, 2011. Effects

of different nitrogen fertilizer rate on starch percentage, soluble sugar, dry matter, yield and yield

components of potato cultivars. University of Mohagheghe Ardabili, Ardabil, Iran.Austr. J. of

Basic and Applied Sciences, 5(9): 1846-1851.

Kanzikwera, C.R., J.S. Tenywa, D.S.O. Osiru, E. Adipala and A.S. Bhagsari. 2001. Interactive effect of

Nitrogen and Potassium on dry matter and nutrient partitioning in true potato seed mother plants.

African Crop Science Journal. 9: 127-146.

Karlsson, B.H., Palta, J.P. and Crump, P.M. 2006. Enhancing tuber calcium concentration may reduce

incidence of black spot bruise injury in potatoes. Horticultural Science, 41: 1213–1221.

Kassa, B., and Beyene, H. 2001. Efficacy and economics of fungicides spray in the control of late blight

of potato in Ethiopia. African Crop Science Journal, 9 (1): 245-250.

Khan, A. A., Jilani, G., Akhtar, M. S., Naqvi,S. S. and Rasheed, M. 2009. Phosphorus solubilizing

bacteria: occurrence, mechanisms and their role in crop production. Journal of Agricultural

Biology Science, 1:48–58.

Kleinkopf, G. E. and D. T. Westermann, 1987. Specific Gravity of Russet Burbank Potatoes. American

Potato Journal.64: 579-587.

Kleinkopf, G. E., Westermann, D. T., and Dwelle, R. B. 1981. Dry matter production and nitrogen

utilization by six potato cultivars. Agronomy Journal, 73(5), 799-802.

72

Kochian, L.V., Hoekenga, O.A. and Pineros, M.A., 2004. How do crop plants tolerate acid soils

Mechanisms of aluminium tolerance and phosphorus efficiency? Annual Review of Plant

Biology 55:459-493.

Kolech, S.A., Halseth, D., De Jong, W. Am. J. 2015. Potato Variety Diversity, Determinants and

Implications for Potato Breeding Strategy in Ethiopia. American Journal of Potato Research,

92(5):551–566.

Koter M., Benedycka Z. 1984. Effect of differentiated mineral fertilization on yield and chemical

composition of common radish. Part I. Response of common radish to fertilization with chloride

and potassium sulphate in a pot experiment.Biul.Warzyw. 27: 317-337. (In Polish).

Koter M., Grzesiuk W. 1966. The influence of sulphur (CaSO4) fertilizing upon the yield of crops and

their chemical composition. Rocz. Nauk Rol., A-92(1): 43-52. (in Polish).

Krauze A., Bowszys T. 2000. Effect of applying different technologies of sulfur fertilizer application on

yield and quality of winter and spring rape. Fol. Univ. Stetin., Agric., 204(81): 133-142. (In

Polish).

Kumar, D., R. Ezekiel and S.M.P. Khurana, 2003. Effect of location, season and cultivar on the

processing quality of potatoes. J. Indian Potato Assoc., 30:247-251.

Kushwaha, P., Jaiswal, R.K., Gupta, N.K. and Sharma, S.K. 2014. Performance of potato genotypes for

morphological parameters and tuber yield under Malwa region of Madhya Pradesh. Annuals of

Plant and Soil Research, 16(4): 376-377.

Labarta, R., Malwa, C., Schulte-Geldermann, E., Borus, D. and Lemaga, B. 2011. Adoption of seed

quality improvement strategies among potato producers in Kenya. International Conference on

Increasing Agricultural Productivity and Enhancing Food Security in Africa: New Challenges

and Opportunities Addis Ababa, November 1-3, 2011.

Laufer, B. 1938. The American plant migration: Part I: The potato. Publications of the Field Museum of

Natural History Anthropological Series 28(1):1-132.

Lemaga Burga, 1983. Country Program Report on Ethiopian Potato Research Activities. Presented at

the Regional Workshop on Potato Development and Transfer of Technologies in Tropical Africa,

Addis Ababa, Ethiopia.

Levy D. 1986. Genotypic variation in the response of potatoes (Solanum tuberosum L.) to high ambient

temperatures and water deficit. Field Crops Research. 15:85-96.

73

Levy, D. and Veilleux, R.E. 2007. Adaptation of potato to high temperatures and salinity a review.

American Journal of Potato Research, 84: 487-506.

Lung’aho, C., B. Lemaga, M. Nyongesa,M, P. Gildemacher, P. Kinyale, P. Demo and J. Kabira,

2007. Commercial seed potato production in eastern and central Africa. Kenya Agricultural

Institute, Kenya. 140p.

Lujan, L., & Smith, O. (1964). Potato quality XXV. Specific gravity and after-cooking darkening of

Katahdin potatoes as influenced by fertilizers. American Potato Journal, 41(9), 274-278.

Lynch, D. R., and Tai, G. C. 1989. Yield and yield component response of eight potato genotypes to

water stress. Crop Science, 29, 1207–1211.

Lynch, D.R. and R.G. Rowberry.1997. Population density studies with Russet Burbank potatoes. II. The

effect of fertilization and plant density on growth, development, and yield. American Potato

Journal, 54: 57-71.

Mahmoodabad, R., S. Somarin, M. Khayatnezhad and G. Roza. 2010. Quantitative and qualitative yield

of potato tuber by used of nitrogen fertilizer and plant density. Am.-Eur. J.Agric. Environ. Sci., 9:

310-318.

Maity, K., and Arora, P. N. 1980. Effects of varieties, levels and Sources’ of potash on potassium

composition and uptake in potato. Indian Journal of Agronomy, 25(1), 1–8.

Marchenko, H. 1959. Mineral nutrition of higher plants, second edition. Academic press Inc, Sand

Diego. 889pp.

Marschner, H. 1995. Mineral nutrition of higher plants 2nd (Eds.). London, New York: Academic Press.

Marwaha, R.S., S.K. Pandey, D. Kumar, S.V. Singh and P. Kumar, 2010. Potato processing

scenario in India: Industrial constraints, future projections, challenges ahead and

remedies-A review. J. Food Science Technology., 47: 137-156.

McGregor, I. 2007. The fresh potato market.pp.3-36. In: Vreugdenhil, D. (Eds), Potato Biology and

Biotechnology. Elsevier, Amsterdam.

Manjula, V.N. 2009. Soil, Plant, Nutrient Management.

Medhin Gebre, Solomon Asefa, Endale Gebre, Bekele Kassa. 2000. Multi location testing of clones in

Ethiopia', Ethiopian Agricultural Research Organization, Progress Report.

74

Medhin, Gebremedhin W/ Giorgis, Endale Gebre, Kiflu Bedane, Bekele Kassa. 2001. Country Profile

on Potato Production and Utilization: Ethiopia. Ethiopian Agricultural Research Organization

(EARO), Holeta Agricultural Research Centre, National Potato Research Program.

Mekashaw, M. 2016. Assessment of farmer’s production practices and effects of different rates of NPS

fertilizer on yield and yield components of potato (Solanum tuberosum L) variety under irrigated

farming system in Dessie Zuria District, Amhara Region, Ethiopia (MSc Thesis). Bahir Dar

University, Ethiopia.

Mekonen Shiferaw, Tameru Alemu, Bekele Kassa and Forbes, G. 2011. Evaluation of contact fungicide

sprays regimes for control of late blight (Phytophthora infestans) in southern Ethiopia using

potato cultivars with different levels of host resistance. Tropical Plant Pathology, 36: 21-27.

Mengel, K. and Kirkby, E. A. 1996. Principles of plant nutrition. Panimo published corporation, New

Delhi, India.

Millard, P., and Marshall, B. 1986. Growth, nitrogen uptake and partitioning within the potato (Solanum

tuberosum L.) crop, in relation to nitrogen application. The Journal of Agricultural Science,

107(02), 421-429.

Miller, R.W. and Donahue, R.L. 1995. Soils in our Environment7th (Eds). Prentice-Hall of India private

limited, New Delhi. pp. 261-289.

Ministry of Agriculture and Natural Resource, 2013. Ethiopia is transitioning into the implementation of

soil test based fertilizer use system.

MOA (Ministry of Agriculture), 2013. Plant Variety Release, Protection and Seed Quality Control

Directorate, Crop Variety Register Issue No.1 6, pp.161-164. , Addis Ababa, Ethiopia.

Molerhagen, P.J., 1993.The influence of nitrogen fertilizer application on tuber yield and quality in three

potato varieties grown at different locations in Norway. Norsk - land bruks for sking.7 :479-296.

Mulatu Eshetu, Osman E. Ibrahim and Etenesh Bekele, 2005. Improving potato seed tuber quality and

producers’ livelihoods in Hararghe, Eastern Ethiopia. Journal of New Seeds.7 (3): 31–56.

Mulatu Eshetu, Osman E. Ibrahim and Etenesh Bekele, 2006. Policy Changes to Improve Vegetable

Production and Seed Supply in Hararghe, Eastern Ethiopia. In: Mulatu Eshetu, Osman E.

Ibrahim and Etenesh Bekele, 2005. Improving potato seed tuber quality and producers’

livelihoods in Hararghe, Eastern Ethiopia. Journal of New Seeds.7 (3): 31–56.

75

Mulubrhan Haile. 2004. The effects of nitrogen, phosphorus and potassium fertilization on the yield and

yield components of potato (Solanum tuberosum L.), Grown on vertisols of Mekelle area

Ethiopia. MSc. Thesis, School of Graduate Study Alemaya University, Ethiopia, Pages: 83

Mureithi, L.M., T.K. Wanyoike, K. Kamau and L.K. Kariuki, 2000. Current status of potato seed tubers

and soils as major sources of bacterial wilt infection around the slopes of Mount Kenya. Paper

No. 49. 7th KARI Biennial Scientific Conference held at KARI Head quarters, Nairobi, Kenya

13-17 November, 2000.

Murphy, H. F. 1968. A report on fertility status and other data on some soils of Ethiopia. Experimental

Station Bulletin No. 44. Hailesilassie College of Agriculture. Oklahoma State University, 551P.

Nasreen, S., S.M.I. Haq and M.A. Hossain, 2003. Sulphur effects on growth responses and yield

of onion. Asian J. Plant Sci., 2: 897-902.

Nelson, D. C., and Shaw, R. 1976. Effect of planting and harvest dates, location in the hill and tuber size

on sugar content of Kennebec potatoes. American Potato Journal, 53(1), 15-21.

Ngungi, D.N., 1982. Agronomic concept of potato with reference to increasing the potential yield under

Tropical condition. pp. 13-16. In: Nganga, S. and F. Shielder (Eds.). Potato seed production for

Tropical Africa.CIP, Lima and Peru.

Nigussie Dechassa, Schenk, M.K. and Steingrobe, N. 2003. Phosphorus efficiency of cabbage (Brassica

oleraceae L. var. capitata), carrot (Daucus carota L.), and potato (Solanum tuberosum L). Plant

and Soil, 250: 215-224.

Olsen, S.R., Cole, V., Walanbe, C.V. and Dean, L.A. 1954. Estimation of Available phosphorus in soils

by extraction with Sodium Bicaarbonate.USA Circular NO 939.

ORARI (Oromia Regional Agricultural Research Institute). 2007. Crop research thematic area for

2008/2009, October 2007, Addis Ababa.

Otipa, M.J., M.W. Wakahiu, P.M. Kinyae, D.M. Thuo and J.I. Kinoti, 2003. Survey of the Bacterial wilt

of potatoes caused by Ralstonia solanacearum and its spread in major potato growing areas of

Kenya. Task force Report to the Director-KARI.

Painter, C. G., and Augustin, J. 1976. The effect of soil moisture and nitrogen on yield and quality of the

Russet Burbank potato. American Potato Journal, 53(8), 275-284.

Pankhurst, R. 1964. Notes for a history Ethiopian Agriculture. Ethiopian Observer, 7: 210–240.

76

Petitte, J.M. and D.P. Ormrod, 1988. Effects of sulphur dioxide and nitrogen dioxide on shoot

and root growth of Kennebec and Russet Burbank potato plants. Am. J. Potato Res., 65:

517-527.

Peter, V. and Hruska, C.L. 1988. Yield Formation in Potatoes. In: Yield Formation in Main Field Crops.

Elsevier Science Publishers. B.V. Amsterdam, The Netherlands. pp. 268- 330.

Podleś Naa. 2003. Preliminary estimation of sulfur fertilization requirements of winter oilseed rape.

Rośl.Oleiste - Oilseed Crops, 24(2): 641-649. (In Polish).

Podleś Naa. 2004. The effect of sulfur fertilization on concentration and uptake of nutrients by winter

oilseed rape. Rośl. Oleiste - Oilseed Crops, 25: 628-636. (in Polish).

Porter, G. A., & Sisson, J. A. 1993. Yield, market quality and petiole nitrate concentration of non-

irrigated Russet Burbank and Shepody potatoes in response to side dressed nitrogen. American

Potato Journal, 70(2), 101-116.

Prakash, O., S. Singh and V. Singh, 1997. Status and response of sulphur in alluvial soils for

higher yields of vegetable crops. Fertilizer News, 42: 23-24.

Rai, N., and Yadav, D. S. 2005 Advances in vegetable production. New Delhi, India: Research co Book

Centre.

Ramamurthy, N. and L.S. Devi, 1982. Effect of different sources of sulphur on the yield and

quality of potato. J. Ind. Soc. Soil Sci., 30: 405-407.

Reddy, S.N. and Rao, R.S. 1968. Response of potato to different levels of nitrogen, phosphorus and

potassium in a sandy loam soil in Hyderabad. Indian Journal of Agricultural Sciences, 38: 577–

588.

Reeve, H.M., Timm, H. and Weaver, M. I. 1973. Parenchyma Cell Growth in Potato Tubers. American

Potato Journal, 50: 50-58.

Rendig, V. V., and Taylor, H. M. 1989. Principles of soil-plant interrelationships. Mc Graw-Hill

Publishing Company.

Rezaul Karim, M., R. Hafizur, A., Tanziman, M.S.T., Rehena Khatun, M., Monzur Hossain A.K.M.,

Rafiul Islam. 2011. Yield potential study of meristem derived plantlets of ten

potato varieties (Solanum tuberosum L.). International Biosciences Journal, 1(2): 48-53.

Roberts, S., and H.H. Cheng. 1988. Estimation of critical nutrient range of petiole nitrate for sprinkler

irrigated potatoes. American Potato Journal. 65: 119 – 124.

77

Rocha, F.A.T., Fontes, P.C.R., Fontes, R.L.F., and Reis, F.P. 1997. Critical phosphorus concentrations

in potato plant parts at two growth stages. Journal of Plant Nutrition 20:573-579

Romero-Lima, M.R, Santos, A. T., Garcia-Espinosa, R. and Ferrera Cerrato, R. 2000. Yield of Potato

and soil microbial biomass with organic and mineral fertilizers. Pbcado Com Articulo

Agrociencia, 34: 261-26.

Rosen, C.J. and P.M. Bierman, 2008. Potato yield and tuber set as affected by phosphorus fertilization.

American Potato Journal, 85: 110-120.

Rourke, R. V. 1985. Soil solution levels of nitrate nitrogen in a potato-buckwheat rotation. American

potato journal, 62(1), 1-8.

Sanchez, C. A., Lockhart, M., and Porter, P. S. 1991. Response of radish to phosphorus and potassium

fertilization on Histosols. Hort Science, 26(1), 30-32.

Sauer, J. D. 1993. Historical geography of crop plants: A select roster. CRC Press, Boca Raton, FL

(Florida).

Sayre, R. N., Nonaka, M., and Weaver, M. L. 1975. French fry quality related to specific gravity and

solids content variation among potato strips within the same tuber. American Potato Journal,

52(3), 73-82.

Schippers, P.A. 1976. The relationship between specific gravity and percentage dry matter in potato

tubers.Scientific Basis for Improvement. pp. 292-330. 2nd Edition. Chapman and Hall,

London.security.

Schulte-Geldermann, E., Wachira, G. and Ouma, A. E. 2010. Assessing the potential of applying

phosphonite fungicides to enhance host tolerance in potato to late blight. 8th African potato

association conference, 5-9 December 2010, Cape Town, South Africa.

Seidler m. 1975. Effect of chlorine and sulphur on Oat, Buck wheat, Mustard and Serradela.

Sharifi, M., Zebarth, B. J., Hajabbasi, M. A., & Kalbasi, M. 2005. Dry matter and nitrogen accumulation

and root morphological characteristics of two clonal selections of ‘Russet Norkotah’potato as

affected by nitrogen fertilization. Journal of plant nutrition, 28(12), 2243-2253.

Sharma, D. 2015. Effect of sulfur on growth, yield and economic of potato cultivar. Annuals of Plant

and Soil Research, 17(1), 45–49.

78

Sharma, S.P., A.S. Sandhu, R.D. Bhutani, and S.C. Khurana, 2014. Effects of planting date and fertilizer

dose on plant growth attributes and nutrient uptake of potato (Solanum tuberosum

L.).Int.J.Agr.Sci .Hisar, India.4 (5): 196-202.

Sharma, V.C. and Arora, B.R. 1987. Effects of nitrogen, phosphorus, and potassium application on the

yield of potato (Solanum tuberosum L.) tubers. Journal of Agricultural Sciences, 108: 321-329.

Shayanowako, A., Mangani, R., Mtaita, T., and Mazarura, U. 2015. Influence of Main Stem Density on

Irish Potato Growth and Yield: A Review. Annual Research and Review in Biology, 5(3), 229.

Shiferaw, H. 2014. Digital soil mapping: Soil fertility status and fertilizer recommendation for

Ethiopian agricultural land (Conference paper). Addis Ababa, Ethiopia.

Simret Burga, 2010. Influence of inorganic nitrogen and potassium fertilizers on seed tuber yield and

size distribution of potato (Solanum tuberosum L.). An. M. Sc Thesis Presented to the School of

Graduate Studies of Haramaya University, Ethiopia. 65p.

Simret Burga, Nigussie Dechassa, and TekalignTsegaw, 2010. Influence of inorganic nitrogen and

potassium fertilizers on seed tuber yield and size distribution of potato. Proceedings of the

National Workshop on Seed Potato Tuber Production and Dissemination, 12-14 March 2012,

Singh, J., Singh, M., Saimbani, M. S., and Kooner, K. S. 1993. Growth and yield of potato cultivars as

affected by plant density and potassium levels. Journal of Indian Potato Association, 20(3-4),

279–282.

Singh, J.P., R.S. Marwaha and O.P. Srivastava, 1995. Processing and nutritive qualities of

potato tubers as affected by fertilizer nutrients and sulphur application. J. Indian Potato

Assoc., 22: 32-37.

Solomon Yilma, 1985. Review of potato research in Ethiopia. Vol.III.pp.294-307. In proceedings of

First Ethiopian Horticultural workshop. Godefrey Sam Aggrey W. and Bereke Tshai Tuku

(Eds.). February 20-22, 1985. FAO.ILCA.IAR. Addis Ababa, Ethiopia.

Sommerfeld, T. and Knutson, K. 1965. .Effects of nitrogen and phosphorus on the growth and

development of Russet Burbank Potatoes grown in the Southeastern Idaho. American Potato

Journal, 42: 351-360.

Sparrow, L. A., K. S. R. Chapman, D. Parsly, P. R. Hardman and B. Cullen, 1992. Response of potatoes

(Solanum tuberosum L. and Russet Burbank) to band-placed and broadcast high cadmium

phosphorus fertilizer on heavily cropped North-Western Tasmania. Australian Journal of

Agriculture. 32: 113-119.

79

Spooner, D. M. and Salas, A. 2006. Structure, biosystematics, and genetic resources. Pages 1- 39 in J.

Gopal, S. M. P. Khurana, eds. (editions) Handbook of potato production, improvement and

postharvest management. Food Products Press, Binghamton, NY (New York).

Storey, R. M. J., and Davies, H. V. 1992.Tuber quality. In The potato crop (507-569). Springer

Netherlands.

Struik, P. C. 2007. Above-ground and below-ground plant development. Pages 219-236 in

D.Vreugdenhil, J. Bradshaw, C. Gebhardt, F. Govers, D. K. L. Mackerron, M. A.

Sud, K.C. and R.C. Sharma. 2002. Sulphur Needs of Potato under Rain fed Conditions in Shimla

Hills. In: Potato Global Research and Development, Paul Khurana, S.M., G.S

Shekhawat, S.K. Pandey and B.S. Singh (Eds.). Vol. 2. Indian Potato Association, Shimla, pp:

889-899.

Tafi M, Siyadat S.A, Radjabi R, Majadam M., 2010. The effect of earthing up on the potato yield in Dezful

(Khouzestan,Iran) weather condition. Middle East journal of scientific research, 5(5): pp.392-393.

Tamire Hawando, 1973. Characterization of Haramaya Soils. Soil Science Paper, Series No.1. p. 45.

Tantawy, E. and E.M. El-Beik and A.K. El-Beik, 2009. Relationship between growth, yield and

storability of Onion (Alliums cepa L.) with fertilization of nitrogen, sulphur and copper

under calcareous soil conditions. Res. J. Agric. Biological Sci., 5: 361-371.

Taylor. A. Ross, (Eds) Potato biology and biotechnology: Advances and perspectives. Elsevier Science

B.V., Amsterdam.

Tekalign Mamo, Haque, L. and Aduay, E.A. 1991. Working document: Soil, Plant, Fertilizer, Animal

Manure and Compost Analysis Manual. International Livestock center for Africa, No. B13,

Addis Ababa, Ethiopia.

Tekalign, T, 2006. Response of potato to Paclobutrazol and manipulation of reproductive growth under-

tropical conditions (PhD desertation).University of Pretoria, Pretoria, South Africa.

Tekalegn Tsegaw. 2013. Genotype x environment interaction for root yield of elite sweet potato

(Ipomoea batatas (L) lam.) Genotypes. South African Journal of Plant and Soil, 24:144-146.

Teressa, 1995. Sustainable Potato Production. Vol. 15, No. 9.

Tesfaye, A., Yigzaw, D., and Ermias, A. 2008. Crop management research and achievement on potato in

Amhara Region with special reference to western Amhara parts. Proceeding of the 1st Amhara

80

Region workshop on potato Research Development: achievements, transfer experiences and

future directions.20-21 Dec. 2007 Bahirdar. Amhara Region Agricultural Research Institute.

Tesfaye Abebe, Lemega, B., Mwakasendo, J.A., Nzohabonayoz, Z., Mutware, J., Wando, K.Y., Kinyae,

P.M., Ortiz, O., Crissman, C. and Thiele, G. 2010. Markets for fresh and frozen potato chips in

the ASARECA region and the potential for regional trade: Ethiopia, Tanzania, Rwand, Kenya,

Burundi and Uganda, Lima. International Potato Center (CIP).

Thompson, R. and W.J. Kelly, 1983.Vegetable crops.5th (Eds). McGraw Hill Book Co.

Timm, H. and Flocker, W.J. 1966. Response of potato plants to fertilization and soil moisture tension

under induced soil compaction. Agronomy Journal, 77: 616-621.

Tisdale, S. L., Nelson, W. L., Beaton, J. D. and Havlin, J. L. 1995. Soil Fertility and Fertilizers.5th.

Macmillan, New York.

Tisdale, S. L., Nelson, W. L., Beaton, J. D. and Havlin, J. L. 2003. Soil Fertility and Fertilizers, 5th

(Eds), Pearson Education, Inc. New Jersey. P634.

Uppal, D.S. and S.M.P. Khurana, 2001. Chipping performance of potato varieties grown at

different locations. J. Indian Potato Assoc., 28: 233-236.

Uziak Z., Szymańska m. 1979. The influence of sulphur on the utilization of nitrogen by oilseed rape

plants. Ann. UMCS Lublin, Sect. E, 24: 187-201. (In Polish).

Uziak Z., Szymańska m. 1987. The effect of sulphur on the chemical composition of sun power and

serradela. Pam. Puł., 89: 131-142. (In Polish).

Van Gijessel, J. 2005. The potential of potatoes for attractive convenience food: focus on

product quality and nutritional value. pp. 27-32. In: Haverkort, A.J. and Struik, P.C.

(Eds.), Potato in Progress Science Meets Practices. Wageningen Academic Publishers,

Wageningen, the Netherlands.

Vander Schoot, C. 1996. Dormancy and symplasmic networking at the shoot apical meristem.pp. 59-81.

In: Lang, G.A. (ed.), and Plant Dormancy: Physiology, Biochemistry and Molecular Biology.

Wallingford: ACB International.

Verma, S.C, T.R. Sharma and S.M. Verma, 1971. Effects of extended high temperature storage on

weight losses and sugar content of potato tubers. Indian Journal Agricultural Science. 44:702-

706.

81

Verma, S.C.K, Joshi, C., Sharma,T.R. and Malhotra, V.P. 1972. Relation between specific gravity,

starch and nitrogen content of potato tubers

Walker, T.S., P.E. Schmiediche and R.J. Hijmans, 1999. World trends and patterns in the potato Crop:

an economic and geographic survey. Potato Research.42: 241-364.

Walkey, A. and Black, A.C. 1934. An examination of the degtjareff method for western Potato

Council.2003.Botany of the potato plant. Adaptation from Guide to Commercial Potato

Production on the Canadian Prairies. Walling Ford Oxon. The University press, Cambridge.

Warren, D. S., and Woodman, J. S. 1974. The texture of cooked potatoes: A review Journal of the

Science of Food and Agriculture, 25(2), 129-138.

Wassu Mohammed. 2014. Genetic variability in potato (Solanum tuberosum L.) genotypes for late blight

[Phytophthora infestans (Mont.) de Bary] resistance and yield at Haramaya, Eastern Ethiopia.

East African Journal of Sciences, 8(1):13-28.

Wheeler, R.M. 2009. Potatoes for Human Life Support in Space. pp. 485-495. In: Singh, J. and Kaur, L.

(eds.), Advanced in Potato Chemistry and Technology. Academic Press, Burlington, VT.

Wielebski F., muśnicki c. 1998. Effect of increasing doses of sulphur and its application method on the

yield and content of glucosinolates in seeds of two winter oilseed rape cultivars in field

experiments. Rocz. AR Poznań, Rol. 51: 129-147. (In Polish).

Wilcox, G. E. and Hoff, J. 1970. Nitrogen fertilization of potatoes for early summer harvest. American

Potato Journal, 47: 99-102.

William, M.A. and Woodbury, G.W. 1968. Specific gravity dry matter relationship and reducing sugar

changes affected by potato variety, production area and storage. American Potato Journal, 45(4):

119-131.

WPC (Western Potato Council). 2003. Guide to commercial potato production on the Canadian Prairies.

Winnipeg: Western Potato Council.

Wroniak, J. 2006. Nutritional benefits of potato. Ziemn.Pol. 2, 17-20 in Polish.

Yayeh, S. G., Alemayehu, M., Hailesilassie, A., and Yigzaw, D. 2017. Economic and agronomic

optimum rates of NPS fertilizer for irrigated garlic (Alliums sativum L) production in the

highlands of Ethiopia. Cogent Food and Agriculture, 3, 1333666.

82

Yibekal Alemayehu. 1998. The effect of nitrogen and phosphorus on yield and yield components, and

some quality traits of potato (Solanum tuberosum L.) grown on soils of Wendo Genet area. MSc

Thesis. Haramaya University, Ethiopia. 84p.

Yigzaw Dessalegn, Fentahun Mengistu and Tesfaye Abebe. 2008. Performance stability analysis of

potato varieties under rain fed and irrigated potato production systems in North-western Ethiopia.

Ethiopian Journal of Science and Technology, 5(2): 90-98.

Yildrim, Z. and Tokuşoğlu, O. 2005. Some analytical quality characteristics of potato (Solanum

tuberosum L.). Mini tubers developed via in-vitro cultivation, Electronic Journal of

Environmental, Agricultural and Food Chemistry, ISSN: 1579-4377.

Yosef, M. N. 2016. Assessment of onion production practices and effects of N: P2O5: S fertilizers rates

on yield and yield components of onion (Allium cepa L) under irrigated farming system in

Dembiya District, Amhara Region, Ethiopia (MSc thesis). Bahir Dar University, Ethiopia.

Zandstra, H. G., Anderson, R. H., and Dawley, W. K. 1969. Effects of fertilizer on yield and quality of

nor land potatoes in north eastern Saskatchewan. American Potato Journal, 46(3), 69-74.

Zelalem Aychew, Tekalign Tsegaw, Nigussie Dechassa. 2009. Response of potato (Solanum tuberosum

L.) to different rates of nitrogen and phosphorus fertilization on vertisols at Debre Berhan, in the

central highlands of Ethiopia. African Journal Plant Science, 3:16-24.

7. APPENDICES

83

Appendix Table 1. Mean squares from analysis of variance for phenology, growth, yield

components, tuber yield and tuber quality related traits of three potato varieties as influenced by

rates of blended NPS fertilizer at Haramaya in 2018

Trait Variety (V) (2) Blended NPS (6) V x NPS (12) Error (42) CV (%)

Days to 50% emergency 4.3968* 1.5344NS 1.3598NS 0.9325 7.3

Days to 50% flowering 25.5397** 19.0688** 1.6878* 0.6587 0.4

Days to 50% maturity 78.619** 75.593** 3.156NS 2.902 0.2

Plant height (cm) 78.81* 85.3* 27.76NS 21.55 4.6

Number of main stem/hill 71.454** 2.906NS 1.636NS 1.351 23

Average tuber weight (g) 763.88** 363.97** 281.38** 52.89 10.7

Average tuber number 125.682** 12.623* 9.763* 4.228 24.4

Large tuber size (%) 345.67** 75.27NS 233.74** 66.52 11.4

Medium tuber size (%) 5.44NS 7.72NS 47.75* 16.8 22.8

Small tuber size (%) 203.690** 24.938** 16.898** 2.534 20.5

Marketable tuber yield (t ha-1) 1615.87** 130.90** 23.96NS 17.7 17.2

Unmarketable tuber yield (t ha-1) 12.3403** 21.5627** 0.6837** 0.1558 19.2

Total tuber yield (t ha-1) 1749.04** 72.78* 26.95NS 17.82 15.9

Tuber dry matter (%) 21.53NS 18.1NS 11.34NS 19.18 3.7

Specific gravity (%) 0.000117NS 0.0002012NS 0.0001059NS 0.0001878 0.6

Starch content (%) 4.726NS 8.737NS 5.229NS 8.047 8.4

NS,*, and **, nonsignificant, significant at P<0.05 and P<0.01, respectively, and CV (%) =

coefficient of variation in percent. Number in parenthesis in each source of variation represents

degree of freedom.

84

Appendix Table 2. Mean values of traits due to potato varieties and rates of NPS fertilizer at

Haramaya in 2018

Treatment

Days to 50%

flowering

Average tuber

weight (g)

Average tuber

number

Large size

tubers (%)

Small size

tubers (%)

Unmarketable

tuber yield (t ha-1)

Belete 52.62a 74.46b 5.68a 71 8.75 2.935b

Bubu 54.14b 62.68a 9.26b 73.9 7.97 1.551a

Shangi 54.76c 66.32a 10.36b 70.3 6.60 1.672a

LSD (5%) 0.506 1.587 1.282 5.11 1.002 0.2462

Blended NPS

kg ha-1

0 50.89a

55.59a 7.17a 60.5 16.93 5.53c

50 53.33b 64.06ab 7.73b 70.6 9.36 1.54a

100 53.67bc 66.75b 7.73ab 72.6 9.20 1.34a

150 54.56bcd 70.86b 7.83ab 68 6.26 1.30a

200 54.33cd 71.19b 8.41ab 79.4 2.25 1.42a

250 55d 72.67b 10ab 75.1 6.02 1.33a

300 55.11d 73.62b 10.17b 75.9 4.39 1.92b

LSD (5%) 0.773 2.424 1.959 NS 1.531 0.3761

Mean values followed by the same letter(s) in each column (trait) and each treatment had

nonsignificant difference at P < 0.05. LSD (5%) = least significant difference at P < 0.05.

Appendix Table 3. Mean marketable total tuber yields of potato due to interaction of varieties

and rates of blended NPS fertilizer at Haramaya in 2018

Blended NPS

kg ha-1

Marketable tuber yield t ha-1 Total tuber yield t ha-1

Bubu Belete Shangi Bubu Belete Shangi

0 17.42 24.68 12.62 22.95 30.21 18.15

50 29.18 26.68 14.07 30.72 28.22 15.61

100 27.62 27.69 13.4 28.96 29.03 14.74

150 32.02 29.76 11.17 33.32 31.06 12.47

200 31.63 27.90 14.70 33.05 29.32 16.12

250 31.45 33.83 15.07 32.78 35.16 16.4

300 37.29 35.82 19.10 39.21 37.74 21.02

LSD (5%) NS NS

LSD (5%) = least significant difference at P < 0.05 and NS= nonsignificant difference at P <

0.05 among mean values of interaction of variety and NPS fertilizer in each trait.

85

effect of blended nps fertilizer rates on yield, yield

Documents