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SOIL SUITABILITY EVALUATION FOR MAIZE PRODUCTION IN KENYA
A Report by National Accelerated Agricultural Inputs Access
Programme (NAAIAP) in collaboration with Kenya Agricultural
Research Institute (KARI)
Department of Kenya Soil Survey, February 2014
NAAIAP KARI EUROPEAN UNION WORLD BANK
REPUBLIC OF KENYA
MINISTRY OF AGRICULTURE, LIVESTOCK AND FISHERIES STATE
DEPARTMENT OF AGRICULTURE
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SOIL SUITABILITY EVALUATION FOR
MAIZE PRODUCTION IN KENYA
A Report by National Accelerated Agricultural Inputs Access
Programme (NAAIAP) in collaboration with Kenya Agricultural
Research Institute (KARI)
Department of Kenya Soil Survey, February 2014
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National Accelerated Agricultural Inputs Access Program
(NAAIAP)P. O. Box 30028, 00100NAIROBI.6th Floor, Hill Plaza Email:
[email protected]:www.naaiap.go.ke
© 2014
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Table of ContentsFORWARD
.......................................................................................................................
viPREFACE
........................................................................................................................
viiACKNOWLEDGEMENT
..............................................................................................
viii
1.0 INTRODUCTION
......................................................................................................
11.1 Background Information
.................................................................................................................
1
2.0 SOIL TYPES IN KENYA
............................................................................................
42.1 The Major Soil Types in Kenya
...............................................................................................
42.2 Characteristics of the Major Soil Types
..............................................................................
5
3.0 SOIL FERTILITY EVALUATION
..........................................................................
113.1 Soil Sample Analysis for Fertility Evaluation
.................................................................
11
4.0 SOIL FERTILITY RESULTS AND RECOMMENDATIONS
............................... 124.1 Kwale County
..............................................................................................................................
124.2 Kilifi County
.................................................................................................................................
164.3 Tana River County
.....................................................................................................................
234.4 Lamu County
...............................................................................................................................
264.5 Taita Taveta County
..................................................................................................................
294.6 Garissa County
...........................................................................................................................
354.7 Wajir County
...............................................................................................................................
384.8 Mandera County
........................................................................................................................
414.9 Marsabit County
........................................................................................................................
444.10 Isiolo County
............................................................................................................................
454.11 Meru County
.............................................................................................................................
474.12 Tharaka Nithi County
............................................................................................................
554.13 Embu County
............................................................................................................................
614.14 Kitui County
..............................................................................................................................
674.15 Machakos County
..................................................................................................................
714.16 Makueni County
......................................................................................................................
774.17 Nyandarua County
.................................................................................................................
844.18 Nyeri County
.............................................................................................................................
874.19 Kirinyaga County
...................................................................................................................
954.20 Muranga County
.....................................................................................................................
984.21 Kiambu County
.....................................................................................................................
1054.22 Turkana County
....................................................................................................................
1084.23 West Pokot County
..............................................................................................................
1134.24 Samburu County
..................................................................................................................
1154.25 Elgeyo/Marakwet County
................................................................................................
1184.26 Nandi County
.........................................................................................................................
123
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Table of Contents4.27 Baringo County
.....................................................................................................................
1284.28 Nakuru County
......................................................................................................................
1354.29 Narok County
.........................................................................................................................
1374.30 Kajiado County
......................................................................................................................
1414.31 Kericho County
.....................................................................................................................
1444.32 Bomet County
........................................................................................................................
1484.33 Kakamega County
................................................................................................................
1514.34 Vihiga County
........................................................................................................................
1604.35 Bungoma County
.................................................................................................................
1664.36 Busia County
..........................................................................................................................
1724.37 Siaya County
..........................................................................................................................
1784.38 Kisumu County
.....................................................................................................................
1844.39 Homa Bay County
................................................................................................................
1894.40 Migori County
.......................................................................................................................
1944.41 Kisii County
............................................................................................................................
2004.42 Nyamira County
....................................................................................................................
2074.43 Uasin Gishu County
............................................................................................................
2124.44 Trans Nzoia County
............................................................................................................
215
5.0 REFERENCES
......................................................................................................
220
ANNEX 1. DESCRIPTION OF MAJOR SOIL TYPES FOR COUNTIES
.................................... 221
ANNEX 2. SUMMARIZED FERTILIZER RECOMMENDATIONS PER SUB COUNTY
....... 286
ANNEX 3. LIST OF SAMPLED FARMERS
.................................................................................
293
ANNEX 4. LIST OF TRAINED AGRICULTURAL EXTENSION STAFF
.................................. 450
1. Nyanza and Western Regions
.........................................................................................................
451 2. Rift Valley Region
...................................................................................................................................
4523. Central and Upper Eastern Regions
..............................................................................................
4534. Lower Eastern and Coast Regions
..................................................................................................
4545. Rift Valley (RFI&RLP)
...........................................................................................................................
4556. Central, Rift Valley and Western Regions (January 2014)
.................................................. 456
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vi Enhancing Soil Fertility for Greater Productivity
A strong agricultural sector provides a sound foundation for a
prosperous country. From this recognition, the goal of the
government is expressed in Kenya Vision 2030; that is ‘a viable and
vibrant agricultural sector that is commercially oriented’ and can
compete at international level with more advanced world economies.
Agriculture is the backbone of our country and provides livelihood,
employment and generates income for the population. The sector is
among the key drivers envisaged to deliver the 10% annual economic
growth stipulated in the Economic Pillar of Vision 2030.
The sector, however, faces a number of challenges which include
reduced productivity, high cost of farm inputs, inefficient
utilization of inputs, poor adoption of mechanization, impacts of
climate change and lack of access to agricultural credit. In tandem
with the Vision of the Agricultural Sector Development Strategy
(ASDS); “A food secure and prosperous Nation”, the Ministry
established a program called the National Accelerated Agricultural
Inputs Access Programme (NAAIAP) to empower resource poor
smallholder farmers engaged in maize production through provision
of farm inputs grants to support their normal livelihood
activities. The program promotes sustainable public private sector
partnerships through subsidized credit aimed at ensuring that
smallholder farmers and businesses along the maize value chain
access farm inputs.
The country’s fertilizer market is fully liberalized with the
bulk of fertilizers imported and distributed by the private sector.
However, since 2008, the government through the fertilizer subsidy
program has procured 494,000 metric tonnes of fertilizer in support
of the agricultural sector. A vibrant network of over 5,000
agrodealers situated in major towns and market centres in the
country has developed, providing employment opportunities and
contributing towards food security for the nation.
The staple food crops in Kenya include maize, beans, rice,
potatoes and sorghum. The production of these crops is estimated as
follows; beans (7.3 million bags), rice (2.5 million (50kg) bags),
potatoes (5.6 metric tonnes), wheat (1.8 million bags), sorghum
(1.9 million bags), and millet (1 million bags). In the case of
maize, the estimated annual production is 40 million bags against a
national requirement of 42 million bags (Economic Survey 2013,
Kenya National Bureau of Statistics). The yields of food crops per
acre are on the decline due to adverse effects of climate change,
low adoption of quality farm inputs and continuous farming without
adequate soil nutrients replenishment. This calls for better soil
management practices through soil investigations that provide
farmers with soil amendment and management solutions that not only
increases crop productivity but also conserve the environment.
This report on soil suitability evaluation is a useful tool to
guide farmers, farmer groups, extension providers, dealers in
fertilizers and other stakeholders on the types and levels of
fertilizer application for different areas in the country. Farmers
and other stakeholders are encouraged to acquire the soil test
information and use the fertilizer recommendations to improve their
crop productivity and guide agro dealers in procurement of
fertilizer for various regions in the country. Further, the long
term goal is to encourage farmers to test their soils before
applying organic and inorganic fertilizers.
I take this opportunity to thank the staff in my ministry, KARI
and the Development partners, particularly European Union and World
Bank for their collaboration which has culminated in the production
of this Soil Suitability Evaluation Report.
Felix Koskei CABINET SECRETARYMINISTRY OF AGICULTURE LIVESTOCK
& FISHERIES
FORWARD
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viiUdongo Wenye Rotuba kwa Kuimarisha Uzalishaji
PREFACEThe National Agricultural Accelerated Input Access
program (NAAIAP) is a pro poor program in the State Department of
Agriculture that offers support to resource poor farmers through
fertilizer subsidy and an Agricultural Credit Guarantee Scheme. The
primary objective of NAAIAP is to improve the availability of farm
inputs to vulnerable households by offering start-up inputs grants
in the form of seeds and fertilizers for one acre of maize. The
targeted subsidy is intended to uplift beneficiaries out of the
vicious cycle of poverty and enable them to participate in
commercial agriculture through their own resource mobilization
initiatives and the credit guarantee scheme.
The program started in 2007/08 financial year and targeted to
reach 2.5 million resource poor farmers who own less than 1 hectare
of land country wide. It was envisaged that the increase in yield
and production would meet the household food security needs and
generate surplus income to enable re-investment in agriculture
which would in turn contribute to the national food security.
To ensure sustainability, affordable financial services are
incorporated in the program through the Agricultural Credit
Guarantee Scheme (ACGS). The scheme targets farmers already
involved in commercial agriculture but are constrained by lack of
basic inputs. It entails provision of affordable loans from
competitively procured financial institutions that government has
provided with a credit guarantee fund to cushion participating
banks at 10% against loss from loan default.
To maximize on inputs use, soil sampling and analysis was
incorporated in the program to provide information on the nutrient
status of soils to enable farmers apply the right types and
quantities of fertilizers to minimize problems of land degradation
through build up of soil acidity as a result of blanket fertilizer
recommendations. 9,600 soil samples from 4,800 farms spread in 164
sub counties have been analyzed.
This report provides recommendations on the most appropriate
fertilizer formulation or blend for maize. However, the farm
specific results may be interpreted for other crops. A data base
for soils in the sampled sub counties has been compiled and this
report will be uploaded on the ministry’s website www.kilimo.go.ke.
The report is an invaluable resource for use by farmers,
agricultural extension providers and stakeholders as a tool for
appropriate fertilizer use. The Ministry will continue to advocate
for more soil testing to cover as many farms, crops and regions as
possible.
Mrs Sicily Kariuki, MBSPRINCIPAL SECRETARYSTATE DEPARTMENT OF
AGRICULTURE
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viii Enhancing Soil Fertility for Greater Productivity
ACKNOWLEDGEMENT
The contribution of the following persons towards the completion
of the soil investigation exercise in the NAAIAP program areas is
gratefully appreciated.
Mrs Sicily K. Kariuki (MBS), Principal Secretary in the Ministry
of Agriculture, Livestock and Fisheries, State Department of
Agriculture (SDA), and The Director Kenya Agricultural Research
Institute (KARI), Dr Ephraim A. Mukisira for providing an enabling
environment to the respective officers that ensured the success of
the soil sampling and analysis and overseeing the exercise to
completion. The European Union, through the World Bank, is
sincerely appreciated for financing the exercise through the
project Enhancing Agricultural Productivity Project (EAPP). The
Task Team Leader, World Bank Dr. Andrew Karanja deserves special
mention for his facilitative role in the whole process which
culminated in the soil sampling and analysis exercise.
The Director Agribusiness Directorate (Mr. H. M. Mwangi (MBS)),
who provided valuable guidance during planning and execution of the
exercise. Dr Patrick Gicheru, Centre Director National Agricultural
Laboratories (NARL) is sincerely acknowledged for coordinating and
facilitating field and laboratory activities. KARI/Kenya Soil
Survey staff members who participated in the exercise and report
writing (G.N. Gachini, P.M. Maingi, A. Chek, C.R.K. Njoroge, P.N.
Macharia, N. Mukiira and F. Wandera) are acknowledged. The special
taskforce comprising of Agriculture Secretary, Ann Onyango (MBS),
Rose Mwangi, Mary Githaiga, Dixon Korir, Rymer Sikobe, Simon
Gakunyi, Peter Githuku, Monica Omoro, Francis Wekesa, Mary Karanja,
Lumumba Kokeyo, Josephine Mogere, Dr. Peter Macharia and Benard
Wanjohi are acknowledged for spearheading the launch of soil test
results and writing of this report.
The NAAIAP Secretariat – Rose Mwangi, National Program
Coordinator NAAIAP, Rymer Sikobe, Churchill Amatha, Zaweria Thuku,
Esther Musyoka, Jacob Mutua, Charles Lusweti and Dixon Korir; in
conjunction with support staff, Mary Mokogi, Christine Njeru,
Florence Akinyi, Angela Njue, John Magondu, John Somoni and Alex
Juma are acknowledged for working tirelessly to ensure that field
staff were trained and field and laboratory work was done; and for
ensuring that soil test results and recommednadtions report was
written and disseminated. In particular, Dixon Korir is
acknowledged for the liaison role he played between MoALF and KARI
and for organizing the logistics for the exercise.
We acknowledge NARL laboratory staff who worked tirelessly to
ensure soil analysis was completed on time. The Divisional
Extension Staff who participated in soil sampling exercise are
acknowledged for the rapid collection and delivery of the samples
to NARL. The Principals of three ATCs (Mabanga, Taita, Kaimosi) and
Manager of Caritas, Nyeri are acknowledged for availing training
facilities. Last but not least we most sincerely acknowledge the
farmers who provided us access to their farms to sample the soils
for their cooperation and enthusiasm that made the exercise
possible.
To all who contributed in one way or another towards this
exercise, we thank you most sincerely for ensuring this report is
produced in time for the launch of the soil test results.
Anne A. Onyango, MBSAg AGRICULTURE SECRETARYSTATE DEPARTMENT OF
AGRICULTURE
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1Udongo Wenye Rotuba kwa Kuimarisha Uzalishaji
1.0 INTRODUCTION
1.1 Background Information
Vision 2030’s Economic Pillar envisages the agricultural sector
among the six key growth drivers of the Kenyan economy. This calls
for an agricultural sector that is ‘viable, vibrant and
commercially oriented so as to compete at the international level’
with more advanced world economies. However, the productivity
levels of many crop enterprises is below potential while the yield
trends and value for the last few years have either remained
constant or are on the decline. To achieve sustainable agricultural
production, there is need to enhance the yields per unit of land
while at the same time conserving the soil resources. This is more
so because of the increasing pressure on the land due to rising
population and hence the need to utilize soils better than they
have been utilized in the past.
The National Accelerated Agricultural Input Access Program
(NAAIAP) is a pro-poor, food security and poverty alleviation
government initiative that is aligned with Vision 2030 and other
government policy documents. NAAIAP provides targeted agricultural
inputs subsidy to smallholder resource poor farmers. The program
has been operating for the last 7 years and has reached
beneficiaries in 164 Sub Counties, formerly known as Districts. The
core objective of NAAIAP is to improve farm inputs access and
affordability for small-scale farmers to enhance food security at
household level and generate incomes from sales of surplus produce.
The subsidized inputs kits are intended to promote adoption of new
technologies. In addition, targeted beneficiaries are supported
with extension services and linked to other service providers with
the objective of increasing agricultural productivity.
However, this noble effort faces challenges due to limited
information on crop nutrients requirements, characteristics of
soils and high level of variation in soil properties that are
experienced across many sub counties where the program operates.
This lack of information has made it difficult for program officers
and field staff to offer professional advice on Sub County specific
soil nutrient requirements. To maintain soil fertility, soil
investigations are the farmers’ best guide for any soil amendments
and efficient use of fertilizers. A soil investigation is the first
step in identification of soil related constraints with a goal to
achieving higher yields, maximum profit while utilizing the best
soil fertility management practices.
To mitigate these challenges, NAAIAP undertook to carry out soil
sampling, analysis and interpretation of 9,600 samples spread over
164 sub counties. The exercise was funded through the Enhancing
Agricultural Productivity Project (EAPP) financed by European Union
through World Bank. The following were the objectives of the
exercise:
1. Identification of key soil fertility constraints to improving
crop yield within the project areas and the development of a long
term soil fertility improvement strategy.
2. Provide diagnostic information on soil characteristics to
guide fertilizer application and management decisions.
3. Identify cause and effect relationships needed for primary
intervention and conditioning of affected areas.
4. Provide recommendations of most appropriate fertilizer
formulation/blend for the cropping systems and soil fertility
combinations.
5. Provide a scientifically sound baseline for monitoring
changes and impacts.6. Provide recommendations on liming rates as
soil acidity is a major crop yield limiting factor in many
Kenyan soils.
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2 Enhancing Soil Fertility for Greater Productivity
1.2 Importance of Soil Sampling and Analysis Kenya has 25 major
soil groups based on soil properties which are as a result of the
interaction between climate, topography, parent material, organisms
and time. Soil is the most valuable and widespread natural resource
which supports agricultural based livelihoods. However, there is a
general decline in land productivity due to declining soil
fertility arising from the following factors.
1. Continuous mining of soil nutrients by crops without adequate
replenishment;2. Inappropriate farming practices such as lack of
crop rotation, cultivation down the slope, etc;3. Soil compaction
due to mechanization;4. Land degradation due to erosion of fertile
top soils;5. Continuous use of acidifying fertilizers by farmers;6.
Inadequate knowledge on crop requirements and soil characteristics;
7. Inadequate use of farm inputs; 8. Blanket fertilizer
recommendations; among others.
On the other hand, many rural smallholder farmers and some field
extension agents (government and private sector) are not aware of
the opportunities available to enhance agricultural production
through soil investigations, carried out by sampling and laboratory
testing of the soils. Extension agents also require training to
enable them disseminate information and monitor impact indicators
after research interventions.
1.3 Methodology of Soil Sampling and Analysis ExerciseThe Kenya
Agricultural Research Institute (KARI) was contracted to carry out
soil sampling, analysis, interpretation of the results and make
recommendations for maize production 4,800 smallholder farms in the
country. These farms are located in 164 sub counties where the
project has been implemented. The following were the terms of
reference (TORs).
1. To provide guidance on the selection of representative
farmers/soils within the sub counties based on soil types, cropping
systems, etc.
2. To carry out soil sampling and/or training the ministry’s
field staff to collect soil samples. 3. To provide GPS referencing
of all sample locations.4. To collect samples to a central location
for analysis using a uniform protocol for all districts.5. To
conduct laboratory analysis for major and micro elements, pH, and
organic matter content.6. To interpret the laboratory data and
provide recommendations.7. To develop a training and dissemination
programme for staff in NAAIAP and Farm Inputs Sub-
division.8. To develop a data base for possible up loading to
the Kilimo website.
1.3.1 Training of Trainers (ToT) on Soil Sampling and Delivery
ProtocolsFor efficiency and uniformity in conducting soil sampling
and consistency of the results and recommendations, field extension
staff of MOALF in NAAIAP operational sub counties were trained on
soil sampling and collection of samples. The Kenya Soil Survey of
the National Agricultural Research Laboratories (NARL) conducted
six Training of Trainers (TOT) seminars for the divisional
extension staff. The extension staff who participated came from 161
sub counties out of the expected 164 sub counties.
Three trainings were held at Mabanga (Bungoma) Agricultural
Training Centre (ATC), one session each at Taita (Ngerenyi) and
Kaimosi ATCs, and one session at Caritas, Nyeri. After the
training, it was expected that the ToTs would train other field
staff in their respective sub counties to enable them collect soil
samples in the shortest time possible before the March/April 2012
and March/April 2014 long rains commenced. The following topics
were covered.
1. Introduction to soil testing2. Soil types common in the
county3. Global farms selection
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3Udongo Wenye Rotuba kwa Kuimarisha Uzalishaji
4. Selection of sampling units at farm level5. Factors
considered when sampling soils6. Composite soil sampling7. Soil
sampling patterns and procedures8. Collection of representative
composite soil samples9. Labelling and geo-referencing sampling
points using global positioning system (GPS)10. Soil sampling in
greenhouses11. Sampling plant materials
During training, participants were cautioned against collection
of samples from sites near the roadside, fence, old farmstead,
trash lines or where trash was burnt recently. This is because such
areas were likely to contain elevated levels of essential elements
and may not be representative of a crop growing field.
To back-up classroom theory, practical soil sampling
demonstrations were done in the farms at the three training venues.
The participants were also taken through the process of data
interpretation and fertilizer recommendations based on the
laboratory analytical data in relation to critical soil nutrient
levels (Mehlich et al., 1962; Muriuki and Qureshi, 2001).
1.3.2 Collection of composite soil samplesDuring collection of
representative composite soil samples, the following factors were
considered: soil type, drainage condition, topsoil colour,
topography, crop appearance (performance), hot spots (e.g. saline
areas), management practices (fertilizer and manure application),
rockiness, different cropping patterns, soil moisture status and
cultural practices. In every farm, areas with similar
characteristics were delineated as sampling units (Muriuki and
Qureshi, 2001; Gachene and Kimura, 2003). Two composite soil
samples were then collected in the two biggest sampling units
following the zigzag method based on stratified random sampling for
routine soil fertility evaluation as shown in Figure 2.
1, 2, 3 - Sampling points in the fieldFigure 1:A diagrammatic
representation of the zigzag sample collection method
In every selected sampling unit, six to ten sub-samples were
collected at 0-30 cm depth and thoroughly mixed on a gunny bag or
plastic sheet of paper to form a composite sample. About ¼ to ½ Kg
of the composite soil sample was scooped, placed in a polythene
bag, tied and labelled for ease of identification and then put in a
gunny bag or carton. Two composite soil samples were collected from
each farm based on the farm variability and other factors. Thus
sixty composite soil samples were collected from each sub county
soil analysis, interpretation and fertilizer recommendations.
Samples were collected in March 2012 and January 2014.
X1 X7 X13 X2 X6 X8 X12 X14
X3 X5 X9 X11 X15
X4 X10 X16
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4 Enhancing Soil Fertility for Greater Productivity
Figure 1 shows the major soil types in Kenya. The description of
the soil types is shown in Table 1. The soils description has been
done according to Sombroek et al. (1982) while soil classification
is according to FAO (2006). Additional soil characteristics may be
found in any Farm Management Handbook of Kenya series e.g. Jaetzold
et al. (2009).
Figure 2: Major soils in Kenya
2.0 SOIL TYPES IN KENYA
2.1 The Major Soil Types in Kenya
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5Udongo Wenye Rotuba kwa Kuimarisha Uzalishaji
2.2 Characteristics of the Major Soil Types The following
characteristics of the major soil types have been described
according to Muchena et al. (1982) and FAO (2006). Additional soil
characteristics may be found in any Farm Management Handbook of
Kenya series e.g. Jaetzold et al. (2009). The major soil types of
the counties where soil sampling was done is shown as annex 1.
ACRISOLS (Very acid soils)These are soils with an ABC sequence
of horizons, of which the A-horizon (topsoil) is relatively low in
organic matter and/or is acid. The B-horizon (subsoil) is
characterized by illuviation of silicate clay minerals (argillic
horizon). Usually the horizon has an angular blocky structure, in
which clay skins are present on at least some of the ped faces and
in the fine pores. The illuviation usually shows a distinct
increase of texture over a relatively short distance. Acrisols are
strongly weathered soils with a low pH (very acid) and a base
saturation of less than 50%. Chemically they are poor. Their cation
exchange capacity (CEC) is usually greater than 16me/100g clay. The
moist consistence is normally friable to firm and the structural
stability is moderate. Some Acrisols contain large amounts of
indurated plinthite.
Preservation of the surface soil with its all-important organic
matter and preventing erosion are preconditions for farming on
Acrisols. Acidity-tolerant cash crops such as pineapples, cashew
and tea can be grown with some success.
ANDOSOLS (Volcanic soils)These are soils that are formed from
recent volcanic material. They are soils with a thick, loose,
granular, dark grey to black A-horizon over a yellowish brown or
brownish C horizon. These soils may be coarse or fine textured but
has usually high silt content. They are very porous, have a low
bulk density (less than 0.85g/cm3), high organic matter content and
a high water storage capacity. The clay is characterized by the
dominance of allophane (amorphous hydrated alluminium silicates of
varying composition). Although differences in parent material may
influence the fertility of the Andosols, they have in general a
high natural fertility and good physical characteristics. However,
phosphate fixation and problems with micronutrients do occur.
The strong phosphate fixation of Andosols (caused by active Al
abd Fe) is a problem. Ameliorative measures to reduce this effect
include application of lime, silica, organic material and phosphate
fertilizer.
ARENOSOLS (Sandy soils)Arenosols are weakly developed soils with
an ABC sequence of horizons. They are characterized by a sandy
texture with less than 15% clay. These soils commonly occur on
quartz-rich crystalline or sedimentary rocks or unconsolidated
sediments derived from them. The topsoil is low in organic matter
content. The soils have a very low cation exchange capacity and a
low moisture storage capacity. The natural fertility of these soils
is in general very low. All Arenosols have common characteristics
such as coarse texture, accounting for their generally high
permeability and low water and nutrient storage capacity. On the
other hand, Arenosols offer ease of cultivation, rooting and
harvesting of root and tuber crops.
CALCISOLS (Calcium rich soils)These soils have substantial
secondary accumulation of lime. They are common in highly
calcareous parent materials and widespread in arid and semi-arid
environments. Vast areas of natural Calcisols are under shrub,
grasses and herbs and are used for extensive grazing.
Drought-tolerant crops (e.g. sunflower) can be grown under rain-fed
conditions. Some vegetables have been grown successfully on
irrigated Calcisols when fertilized with nitrogen, phosphorus and
trace elements (iron and zinc). Furrow irrigation is superior to
basin irrigation on slaking Calcisols because it reduces surface
crusting/cracking and seedling mortality.
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6 Enhancing Soil Fertility for Greater Productivity
CAMBISOLS (Young soils) These are “young” and little weathered
soils. They have an ABC sequence of horizons, the B-horizon being
“Cambic”. The B-horizon is an altered horizon which shows already a
soil structure with significant amounts of weatherable primary
minerals. Cambisols have a relatively high natural fertility. They
have in general a CEC of more than 24 me/100g clay. The texture of
these soils is variable but usually finer than sandy loam.
Cambisols generally make good agricultural land and are used
intensively.
CHERNOZEMS (Dark coloured soils rich in organic matter)These are
soils with dark coloured topsoil that is relatively rich in organic
matter and is non-acid. The subsoil (B-horizon) is usually dark
brown and has an accumulation of free carbonates, increasing with
depth. The topsoil has a granular structure while the subsoil has a
blocky structure. These soils are little weathered and have a high
natural fertility. In general they have a CEC of more than 24
me/100 g clay. The texture is usually clay. The preservation of the
favorable soil structure through timely cultivation and careful
irrigation at low watering rates prevents ablation and erosion.
FERRALSOLS (Highly weathered soils)These are mineral soils with
an “Oxic” B-horizon from which weathering has removed or altered a
large part of the silica. The result of the weathering is the
concentration of clay-sized minerals consisting of sesquioxides (Fe
+ Al oxides) mixed with varying amounts of silicate clays having a
1:1 lattice (e.g. kaolinite). These soils are strongly weathered,
strongly leached and have an indistinct soil horizon
differentiation. The oxic B-horizon has more than 15% clay-sized
particles (texture of sandy loam or finer). The colour of the oxic
horizon is widely variable: from dark red to brown. They are very
friable, highly porous and permeable. The structure is weakly
coherent massive to subangular blocky and is characteristically
stable (high flocculation index).
These soils have very low cation exchange capacities (CEC less
than 16 me/100g clay) and low base saturation. Weatherable minerals
like feldspars, mica and ferromagnesian minerals are nearly absent.
Chemically these soils are poor. The natural fertility of many of
these soils is restricted to the A-horizon and related to the
organic matter content.
Maintaining soil fertility by manuring, mulching and/or adequate
(i.e. long enough) fallow periods or agroforestry practices, and
prevention of surface soil erosion are important management
requirements. Further, fertilizer selection and the mode and timing
of fertilizer application determines to a greater extent the
success of agriculture on Ferralsols.
FLUVISOLS (Alluvial soils)These are young soils that have
developed on alluvium of recent origin. They do not include soils
developed from old alluvial deposits that now reflect the influence
of climate and vegetation. They have no horizon differentiation due
to soil forming processes but they show stratification due to
sedimentary deposition. They have an organic matter content that
decreases irregularly with depth and they receive fresh sedimentary
material at regular intervals. The fertility of these soils varies
widely, depending on their texture and on the nutrient content of
soils and rocks in the watershed from which the alluvial deposits
originate. However, in general most of the Fluvisols are well
supplied with plant nutrients. Paddy rice cultivation is widespread
on tropical Fluvisols with satisfactory irrigation and drainage.
Many dry land crops are grown on Fluvisols as well, normally with
some form of water control.
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7Udongo Wenye Rotuba kwa Kuimarisha Uzalishaji
GLEYSOLS (Poorly drained soils)These are poorly drained mineral
soils which are periodically waterlogged. Periodic or permanent
saturation by groundwater is reflected by greyish colours or
prominent mottling. These soils have B-horizons that are weakly
developed (cambic rather than argillic). They have no clear
textural differentiation. The fertility of these soils is widely
variable. Some of these soils have high contents of organic matter
in the topsoil and therefore are relatively fertile, whereas others
are very acid. The main obstacle to utilization of Gleysols is the
necessity to install a drainage system to lower the groundwater
table. Liming of drained Gleysols that are high in organic matter
and/or of low pH value creates a better habitat for micro- and
meso-organisms and enhances the rate of decomposition of soil
organic matter and the supply of nutrients.
GREYZEMS (Soils rich in organic matter having a grey
colour)These are soils with an ABC sequence of horizons, of which
the A horizon is dark coloured and relatively rich in organic
matter. The B-horizon usually has a prismatic or angular blocky
structure showing bleached coatings on the ped surfaces. The
texture ranges from friable clay loam in the topsoil to very firm,
cracking clay in the subsoil. They have a moderate to high natural
fertility.
HISTOSOLS (Bog and Marsh soils)These are poorly drained soils
with thick topsoil that contains a high percentage of fresh or
partly decomposed organic matter. The topsoil (Histic horizon) is
at least 40 cm thick and is dark coloured (sometimes black). The
physical and chemical characteristics of these soils are strongly
determined by the environment and the type of plants that
accumulated to give rise to the organic matter content. It is
desirable to protect and conserve fragile peat lands because of
their intrinsic value, especially their common function as sponges
in regulating stream flow and unique species of animal(s). Their
prospects for sustained agricultural use are meager.
LEPTOSOLS (Soils with hard rock at very shallow depth)These are
shallow soils with an AR sequence of horizons. The topsoil is not
rich in organic matter and there is no B-horizon of any kind. These
soils have continuous coherent and hard rock (R-horizon) within 10
cm of the surface. Most of the Lithosols are found in hilly and
mountainous areas on slopes with excessive and often erosive
run-off. The fertility of these soils is widely variable, depending
on the parent material. Erosion is the greatest threat to Leptosol
soils, particularly on sloping populated lands. Steep slopes with
shallow and stony soils can be transformed into cultivated land
through terracing, the removal of stones by hand and their use as
terrace fronts.
LITHOSOLS- LEPTOSOLS (Soils with hard rock at very shallow
depth)These are shallow soils with an AR sequence of horizons. The
topsoil is not rich in organic matter and there is no B-horizon of
any kind. These soils have continuous coherent and hard rock
(R-horizon) within 10 cm of the surface. Most of the Lithosols are
found in hilly and mountainous areas on slopes with excessive and
often erosive run-off. The fertility of these soils is widely
variable, depending on the parent material. Erosion is the greatest
threat to Leptosol soils, particularly on sloping populated lands.
Steep slopes with shallow and stony soils can be transformed into
cultivated land through terracing, the removal of stones by hand
and their use as terrace fronts.
LIXISOLS (Highly weathered and poor soils)They comprise soils
that have higher clay content in the subsoil than in the topsoil as
a result of clay migration. They have a high base saturation and
low activity clays at certain depths. Preservation of surface soil
with its all important organic matter is of utmost importance.
Tillage and erosion control measures such as terracing, contour
ploughing, mulching and use of cover crops help to conserve the
soil. Growing of perennial crops is preferred to annual crops,
particularly on sloping land. Rotation of annual crops with
improved pasture is recommended in order to maintain or improve the
content of soil organic matter.
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8 Enhancing Soil Fertility for Greater Productivity
LUVISOLS (Soils with illuvial accumulation of clay)These are
soils with an ABC sequence of horizons, of which the A-horizon is
relatively low in organic matter. Luvisols have similar
morphological characteristics as the Acrisols. They are separated
from each other solely on the base saturation of the lower part of
the B-horizon. The Luvisols have a base saturation of more than 50%
whereas the Acrisols have a base saturation of less than 50%.
Luvisols are moderately to strongly weathered soils. Due to
their relatively high base saturation and the presence of
weatherable primary minerals, they have a moderate natural
fertility. They have a tendency to form a strong sealing on the
surface which may cause a strong run-off of water leading to severe
erosion. Most Luvisols are fertile soils and are suitable for a
wide range of agricultural uses. Luvisols on steep slopes require
erosion control measures.
NITISOLS (Deep, red friable clays)Nitisols accommodate those
soils that are more than 150 cm deep, show evidence of clay
movement and have conspicuous shiny ped surfaces throughout the
subsoil (B-horizon). They have a clay texture and show gradual to
diffuse soil horizon boundaries. The colour is often dark red,
dusky red or dark reddish brown. These soils show a very gentle
clay illuviation resulting in a gentle clay bulge over a traject of
at least 150 cm. They usually have topsoil with a moderate to
strong sub-angular blocky structure underlain by subsoil with a
moderate angular blocky structure. The soils are friable or vey
friable and are porous throughout. They have marked structure
stability. The chemical properties of these soils vary widely. The
organic matter content, cation exchange capacity (CEC) and
percentage base saturation range from low to high. The soils are
known to have a high degree of phosphorus sorption.
Nitisols are among the most productive soils of the humid
tropics. The deep and porous solum and the stable soil structure of
Nitisols permit deep rooting and make these soils quite resistant
to erosion. High P sorption calls for application of P fertilizers,
usually provided as slow-release, low-grade phosphate rock (several
tones per acre, in maintenance, doses every few years) in
combination with smaller applications of better soluble phosphate
for short term response by the crop.
PHAEOZEMS (Dark coloured soils rich organic matter)These are
soils with dark coloured topsoil (mollic A-horizon) that is
relatively high in organic matter and is non-acid. The base
saturation of the topsoil is over 50%. These soils usually have an
ABC sequence of horizons. The subsoil (B-horizon) usually has a
well developed blocky structure with a high porosity. These soils
have a high natural fertility due to the high organic matter
content and an abundant supply of mineral nutrients. Their CEC is
usually over 24 me/100g clay. Phaeozems are porous, fertile soils
and make excellent farmland. Wind and water erosion are serious
hazards if they are left uncontrolled.
PLANOSOLS (Vlei soils)These are imperfectly drained soils with a
pronounced and abrupt transition between relatively light textured
topsoil, part of which is whitish (“albic or E-horizon”) and a
heavy textured, compact and hard B-horizon. They have a very slow
vertical and horizontal drainage and are therefore often
waterlogged. The natural fertility varies widely, depending on
texture and organic matter content of the topsoil. Natural
Planosols areas support sparse grass vegetation, often with
scattered shrubs and trees that have shallow root systems and can
cope with temporary water-logging. Vast areas of Planosols are used
for extensive grazing.
RANKERS (Shallow, acid soils rich in organic matter)Rankers are
shallow soils with an ACR or AR sequence of horizons, on siliceous
parent material. They are acid and rich in organic matter. They are
usually associated with steep slopes. The texture and natural
fertility vary widely, both depending on parent material and degree
of weathering.
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9Udongo Wenye Rotuba kwa Kuimarisha Uzalishaji
RENDZINAS (Shallow soils over limestone, rich in organic
matter)These soils are developed form calcareous material. Calcium
carbonate (CaCo3) usually occurs throughout the soil profile. They
have an AC sequence of horizons. The A-horizon is dark coloured,
rich in organic matter and is not more than 50 cm thick. Its
thickness and organic matter content is greater than that of
Lithosols and Regosols developed from calcareous material. The
A-horizon contains or overlies calcareous material, with a calcium
carbonate equivalent of more than 40%. The soils have a high base
saturation and are relatively fertile.
REGOSOLS (Weakly developed soils of loose material)These are
shallow soils with an AC sequence of horizons. The topsoil is low
in organic matter and there is no B-horizon of any kind. Directly
below the A-horizon is a weathering rock material that is
unconsolidated (C-horizon). Very often, these soils are stony and
rocky. Their natural fertility varies widely, depending on the
parent material. Many Regosols are used for extensive grazing.
Others are planted with small grain variety crops and fruit trees.
Regosols in mountainous regions are delicate and best left under
forest.
SOLONETZ (Alkali soils)These are soils with an ABC sequence of
horizons characterized by the presence of a natric B-horizon. A
high level of sodium on the exchange complex causes the clay to
disperse and to move from the A to the B-horizon. Usually a
characteristic columnar structure develops. Upon wetting, this
natric B-horizon becomes virtually impermeable. The soils have a pH
between 8.5 and 10. Their natural fertility is low to moderate, due
to relatively low organic matter content in the topsoil. The deeper
subsoils are often saline.
Most reclamation attempts start with incorporation of gypsum or
exceptionally calcium chloride in the soil. Traditional reclamation
strategies begin with planting of a sodium-resistant crop, e.g.
Rhodes grass, to gradually improve the permeability of the soil.
Once a functioning pore system is in place, Na ions are carefully
leached from the soil with good-quality (Ca-rich) water.
SOLONCHAKS (Strongly saline soils)These soils contain a lot of
soluble salts that are harmful to the growth of agricultural crops,
mainly because of the high osmotic pressure of the soil solution,
which reduces the availability of water. Soils that have an
electrical conductivity of the saturation extract (ECe) greater
than 15 mmhos/cm are considered to be Solonchaks.
Solonchaks usually occur in association with saline-alkali
soils. Saline-alkali soils are characterized by an electrical
conductivity of the saturation extract of more than 4 mmhos/cm
(saline) combined with an exchangeable sodium percentage (ESP) of
more than 15 (alkali). Their pH may vary widely, but usually is
between 8.0 and 8.5. The clay disperses easily upon wetting.
Solonchaks are used for extensive grazing of sheep, goats, camels
and cattle, or are left as idle land.
VERTISOLS (Dark coloured, strongly cracking clay soils)These
soils are popularly known as “Black cotton soils”. The texture is
clay throughout (more than 35% clay) and the clay minerals are of
the montmorillonite type. This is reflected in great plasticity and
stickiness of the soils when they are wet and a pronounced hardness
when dry. They are usually imperfectly drained or poorly
drained.
A sticking feature of these soils is their capacity to expand
and contract with changes in moisture content. During the dry
season, they shrink markedly and large cracks develop sometimes up
to a depth of 1 metre. As a result of these soil movements,
slickensides (large, shiny, grooved ped surfaces) develop in the
subsoil and gilgai micro-relief (small mounds) is formed at the
surface. The natural fertility of these soils is moderate. Physical
properties are adverse: low infiltration rate, low permeability and
difficult tillage.
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10 Enhancing Soil Fertility for Greater Productivity
These soils have considerable agricultural potential, but
adapted management is a precondition for sustained production.
Their physical soil characteristics and, notably, their difficult
water management is a cause of tillage problems. Building and other
structures on Vertisols are at risk, and engineers have to take
special precautions to avoid damage. Cotton is known to perform
well on Vertisols, allegedly because cotton has a vertical root
system that is not damaged severely by cracking of the soil. Tree
crops are generally less successful because tree roots find it
difficult to establish themselves in the subsoil and are damaged as
the soil shrinks and swells.
XEROSOLS (Soils with an aridic soil moisture regime)These are
soils developed under dry climatic conditions. They have a weak
A-horizon which is low in organic matter. The drainage condition of
these soils ranges from well drained to poorly drained. Most of
these soils are calcareous and have textures ranging from loamy
sand to clay. In many places, these soils are saline and/or
sodic.
2.3 Optimal Conditions for Maize GrowthMaize can be grown on a
wide range of soils but performs best on well-drained, well aerated
and deep soils containing adequate organic matter content and well
supplied with available nutrients (Landon, 1991). High yields of
maize results in heavy drain on soil nutrients and therefore
requires regular replenishment with soil nutrients to replace
nutrients taken up after every harvest. To sustain yields at a
certain level, nutrients out of soil must always be almost equal to
nutrients applied within a growing period taking into consideration
nutrient losses through harvested materials, leaching,
volatilization, and erosion. For optimum production, factors such
as soil moisture, temperature, pests and diseases, weed control,
and soil chemical and physical conditions must be taken into
consideration.
Maize crop grows generally well in soils with a pH range of 5.0
to 8.0 with an optimum pH range for growth at 5.5 to 7.0. The pH
outside this range usually makes certain elements more or less
available, so toxicity or deficiency develops and growth rates of
the crops is reduced. It is very important to maintain the pH as
close to the optimum range as possible because below a soil pH of
5.0, alluminium and manganese toxicities may occur and deficiencies
of P, Mg and Ca become common. At pH above 8.0, deficiencies of Fe,
Mn, Zn and P tend to occur. For example if pH is lower than 6.0, P
starts forming insoluble compounds with iron (Fe) and aluminum (Al)
and if pH is higher than 7.5, P starts forming insoluble compounds
with calcium (Ca) making it unavailable to the plants (Biswas and
Mukherjee, 1992).
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11Udongo Wenye Rotuba kwa Kuimarisha Uzalishaji
3.0 SOIL FERTILITY EVALUATION
3.1 Soil Sample Analysis for Fertility EvaluationThe samples
delivered at NARL were analysed for available macro and micro
nutrients following the methods of Hinga et al. (1980). The
nutrient elements analysed included N, P, K, Ca, Mg, Mn, Fe, Zn,
Cu, total nitrogen and exchangeable acidity where the pH of the
soil was ≤ 5.5. The total organic carbon (C) was determined as
described by Anderson and Ingram, 1993. Other analysis conducted
was on soil pH and available trace elements.
The analytical data was compared with the critical nutrient
levels of maize to come up with a recommendation for maize
production in the sub counties. Farm specific results and
fertilizer recommendations are provided in a CD.
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12 Enhancing Soil Fertility for Greater Productivity
4.0 SOIL FERTILITY RESULTS AND RECOMMENDATIONS4.1 Kwale
County4.1.1 Kinango Sub CountyIn Kinango Sub county, the soil pH
ranges from moderately acid (5.50) to moderately alkaline (7.80)
(Refer to Table 4.1.1). All the 60 farms sampled have their soil pH
within the maize growing range (5.0-8.0) and therefore suitable for
the growth of maize. It is important for the farmers in this region
to apply manure or compost regularly to maintain and sustain the
organic matter content and maintain the pH of the soil within this
range. This will also alleviate aluminium toxicity thereby
increasing availability of phosphorus. This is through organic
colloids preventing dissolved phosphate from coming into contact
(being fixed) with free aluminium and iron (Muller-Samann and
Kotschi, 1994). To maintain the pH within the maize growing range
and prevent further rising of pH acidifying fertilizers such as
Diammonium phosphate (DAP), Monoammonium phosphate, Ammonium
sulphate, urea, etc should be applied in farms with pH greater than
6.5. Farms with pH ≤ 6.5 neutral fertilizers such as triple super
phosphate (TSP), single super phosphate (SSP), compound fertilizers
N:P:K 17:17:17, 15:15:15, 23:23:0, 20:20:0, calcium ammonium
nitrate (CAN) and mavuno should be preferred for application.
In the Sub county, the soil organic matter content ranges from
(0.43% Total Organic Carbon (TOC)) to (2.11% TOC) as shown in Table
4.1.1. 100% of all farms have TOC at low levels and therefore
inadequate soil organic matter content. The inadequate soil organic
matter content results in low water holding capacity and low water
infiltration rate which may result in soil erosion by runoff
surface water during the rains. Soil organic matter impacts
positively on the microbial activities in the soil. Application of
well rotten manure or compost will improve the organic matter
content in all the farms in this Sub County. This will also
supplement the soil nutrients and improve soil structure, water
retention capacity and soil microbial activities.
Table 4.1.1 show the most limiting nutrients are nitrogen with
98%, phosphorus with 87%, calcium 50% and potassium with 32% of the
farms with below adequate levels. Where nitrogen, phosphorus,
calcium and potassium are low, fertilizers containing these
nutrients should be applied to supplement what is available in the
soil.
Table 4.1.1 Soil fertility status of Kinango Sub County
Soil Parameter Min Max Target (critical) level
Samples with below adequate level
% of 60 samples (30 farms)
pH 5.50 7.80 ≥ 5.5 (< 5.5) 0 0Total Organic Carbon (%) 0.43
2.11 ≥ 2.7 60 100Total Nitrogen (%) 0.05 0.21 ≥ 0.2 59 98Available
P (ppm) 1 80 ≥ 30.0 52 87Potassium (me%) 0.10 1.22 ≥ 0.24 19
32Calcium (me%) 0.7 4.7 ≥ 2.0 30 50Magnesium (me%) 1.07 7.93 ≥ 1.0
0 0Manganese (me%) 0.04 0.34 ≥ 0.11 12 20Copper ppm 0.09 1.82 ≥ 1.0
2 3Iron ppm 4.46 61.5 ≥ 10.0 12 20Zinc ppm 0.53 17.3 ≥ 5.0 1 2
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13Udongo Wenye Rotuba kwa Kuimarisha Uzalishaji
As regards manganese, and iron they are inadequately supplied in
the soil in some of the farms. However to maintain adequate levels
of nutrients, regular applications of organic and inorganic inputs
to replenish the removed nutrients through crop harvest and
nutrients lost through avenues such as leaching, vaporization etc.
is encouraged. The micro nutrient zinc is low in 2 % of the farms.
According to the International Zinc Association, maize yields are
reduced by zinc deficiency and may result in reductions in yields
of up to 40% without the appearance of distinct leaf symptoms
(www:zinc.org/crops/resourceserve/zinc facts_sheet_maize, Landon,
1991).
It is recommended that during application of fertilizers in zinc
depleted soils, application of zinc fertilizers or using
zinc-fortified NPK fertilizers is an important practice for maize
growth to maintain high yields and profitability. Salts containing
zinc micro element like zinc sulphate 5-10 kg/ha may be mixed with
other fertilizers during application. Foliar fertilizers containing
this element may also be applied especially for agri-business (high
value) crops. Modification of pH closer to the optimum pH may
render the micro elements which were otherwise unavailable
available. However, most nutrient deficiencies can be avoided in
soils of pH ranges of 5.5 to 7.0, provided that the soil minerals
and organic matter contain the essential nutrients.
In Kinango Sub County, non-acidifying and acidifying fertilizers
are recommended for application because most of the farms have
their pH above 6.0. Non acidifying fertilizers such as Triple Super
Phosphate (TSP), Single Super Phosphate (SSP), compound fertilizers
N:P:K such as 23:23:0, 20:20:0, 17:17:17, Calcium ammonium nitrate
(CAN) and mavuno are recommended for areas with pH below 6.5 and
fertilizers such as DAP, urea, ammonium sulphate (AS) in areas with
pH above 6.5. This Sub County has nitrogen, phosphorus, calcium and
potassium inadequately supplied by the soil. Farmers are encouraged
to carry out regular soil testing to monitor the pH and plant
nutrients trends for future soil fertility management. This will
also give a direction into specific types of fertilizers suitable
for individual farms in future.
Sub County general fertilizer recommendationsManure: 8
t/haPlanting: 200 kg/ha DAPTop dressing: 200 kg/ha CAN in 2 splits
application
4.1.2 Kwale Sub CountyIn Kwale Sub county, the soil pH ranges
from moderately acid (5.35) to moderately alkaline (7.80) (Refer to
Table 4.1.2). All the 60 farms sampled have their soil pH within
the maize growing range (5.0-8.0) and therefore suitable for the
growth of maize. It is important for the farmers in this region to
apply manure or compost regularly to maintain and sustain the
organic matter content and maintain the pH of the soil within this
range. This will also alleviate aluminium toxicity thereby
increasing availability of phosphorus. This is through organic
colloids preventing dissolved phosphate from coming into contact
(being fixed) with free aluminium and iron (Muller-Samann and
Kotschi, 1994). To maintain the pH within the maize growing range
and prevent further rising of pH acidifying fertilizers such as
Diammonium phosphate (DAP), Monoammonium phosphate, Ammonium
sulphate, urea, etc should be applied in farms with pH greater than
6.5. Farms with pH ≤ 6.5 neutral fertilizers such as triple super
phosphate (TSP), single super phosphate (SSP), compound fertilizers
N:P:K 17:17:17, 15:15:15, 23:23:0, 20:20:0, calcium ammonium
nitrate (CAN) and mavuno should be preferred for application.
In the sub county, the soil organic matter content ranges from
(0.16% Total Organic Carbon (TOC)) to (2.77% TOC) as shown in Table
4.1.2, 98% of all farms have TOC at low levels and therefore
inadequate soil organic matter content. The inadequate soil organic
matter content results in low water holding capacity and low water
infiltration rate which may result in soil erosion by runoff
surface water during the rains. Soil organic matter impacts
positively on the microbial activities in the soil. Application of
well rotten manure or compost will improve the organic matter
content in all the farms in this Sub County. This will also
supplement the soil nutrients and improve soil structure, water
retention capacity and soil microbial activities.
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14 Enhancing Soil Fertility for Greater Productivity
Table 4.1.2 show the most limiting nutrients are nitrogen with
93%, phosphorus with 70%, potassium with 62% and calcium with 60%
of the farms with below adequate levels. Where nitrogen,
phosphorus, potassium and calcium are low, fertilizers containing
these nutrients should be applied to supplement what is available
in the soil
Table 4.1.2: Soil fertility status of Kwale Sub County.
Soil Parameter Min Max Target (critical) level
Samples with below adequate level
% of 60 samples (30 farms)
pH 5.35 7.80 ≥ 5.5 (< 5.5) 2 3Total Organic Carbon (%) 0.16
2.77 ≥ 2.7 59 98Total Nitrogen (%) 0.02 0.28 ≥ 0.2 56 93Available P
(ppm) 1 177 ≥ 30.0 42 70Potassium (me%) 0.04 2.63 ≥ 0.24 37
62Calcium (me%) 0.3 10.7 ≥ 2.0 36 60Magnesium (me%) 0.22 9.80 ≥ 1.0
11 18Manganese (me%) 0.11 0.57 ≥ 0.11 0 0Copper ppm 0.07 7.06 ≥ 1.0
47 78Iron ppm 2.40 52.6 ≥ 10.0 24 40Zinc ppm 0.13 8.04 ≥ 5.0 57
95
As regards Magnesium, copper, iron and zinc they are
inadequately supplied in the soil in some of the farms. However to
maintain adequate levels of nutrients, regular applications of
organic and inorganic inputs to replenish the removed nutrients
through crop harvest and nutrients lost through avenues such as
leaching, vaporization etc. is encouraged. The micro nutrient zinc
and copper are low in 95% and 78% of the farms respectively.
According to the International Zinc Association, maize yields are
reduced by zinc deficiency and may result in reductions in yields
of up to 40% without the appearance of distinct leaf symptoms
(www:zinc.org/crops/resourceserve/zinc facts_sheet_maize, Landon,
1991).
It is recommended that during application of fertilizers in zinc
depleted soils, application of zinc fertilizers or using
zinc-fortified NPK fertilizers is an important practice for maize
growth to maintain high yields and profitability. Salts containing
zinc micro element like zinc sulphate and copper element like
copper sulphate at 5-10 kg/h may be mixed with other fertilizers
during application. Foliar fertilizers containing these elements
may also be applied especially for agri-business (high value)
crops. Modification of pH closer to the optimum pH may render the
micro elements which were otherwise unavailable available. However,
most nutrient deficiencies can be avoided in soils of pH ranges of
5.5 to 7.0, provided that the soil minerals and organic matter
contain the essential nutrients.
In Kwale Sub county, non-acidifying and acidifying fertilizers
are recommended for application because most of the farms have
their pH above 6.0. Non acidifying fertilizers such as Triple Super
Phosphate (TSP), Single Super Phosphate (SSP), compound fertilizers
N:P:K such as 23:23:0, 20:20:0, 17:17:17, Calcium ammonium nitrate
(CAN) and Mavuno are recommended for areas with pH below 6.5 and
fertilizers such as DAP, urea, ammonium sulphate (AS) in areas with
pH above 6.5. This Sub County has nitrogen, phosphorus, potassium
and calcium inadequately supplied by the soil. Farmers are
encouraged to carry out regular soil testing to monitor the pH and
plant nutrients trends for future soil fertility management. This
will also give a direction into specific types of fertilizers
suitable for individual farms in future.
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15Udongo Wenye Rotuba kwa Kuimarisha Uzalishaji
Sub County general fertilizer recommendationsManure: 8
t/haPlanting: 200 kg/ha N: P: K 23:23:0Top dressing: 125kg/ha
CAN
4.1.3 Msambweni Sub CountyIn Msambweni Sub County, the soil pH
ranges from strongly acid (4.70) to moderately alkaline (7.79)
(Refer to Table 4.1.3). 95% of all the farms sampled have their
soil pH within the maize growing range (5.0-8.0) and therefore
suitable for the growth of maize. It is important for the farmers
in this region to apply manure or compost regularly to maintain and
sustain the organic matter content and maintain the pH of the soil
within this range. This will also alleviate aluminium toxicity
thereby increasing availability of phosphorus. This is through
organic colloids preventing dissolved phosphate from coming into
contact (being fixed) with free aluminium and iron (Muller-Samann
and Kotschi, 1994). To maintain the pH within the maize growing
range and prevent further rising of pH acidifying fertilizers such
as Diammonium phosphate (DAP), Monoammonium phosphate, Ammonium
sulphate, urea, etc should be applied in farms with pH greater than
6.5. Farms with pH ≤ 6.5 neutral fertilizers such as triple super
phosphate (TSP), single super phosphate (SSP), compound fertilizers
N:P:K 17:17:17, 15:15:15, 23:23:0, 20:20:0, calcium ammonium
nitrate (CAN) and mavuno should be preferred for application.
In the Sub county, the soil organic matter content ranges from
(0.36% Total Organic Carbon (TOC)) to (4.73% TOC) as shown in Table
4.1.3. 90% of all farms have TOC at low levels and therefore
inadequate soil organic matter content. The inadequate soil organic
matter content results in low water holding capacity and low water
infiltration rate which may result in soil erosion by runoff
surface water during the rains. Soil organic matter impacts
positively on the microbial activities in the soil. Application of
well rotten manure or compost will improve the organic matter
content in all the farms in this Sub County. This will also
supplement the soil nutrients and improve soil structure, water
retention capacity and soil microbial activities.
Table 4.1.3 show the most limiting nutrients are nitrogen with
77%, phosphorus with 82%, potassium with 33% and calcium with 30%
of the farms with below adequate levels. Where nitrogen,
phosphorus, potassium and calcium are low, fertilizers containing
these nutrients should be applied to supplement what is available
in the soil
Table 4.1.3: Soil fertility status of Msambweni Sub County
Soil Parameter Min Max Target (critical) level
Samples with below adequate
level
% of 60 samples
pH 4.70 7.79 ≥ 5.5 (< 5.5) 3 5Total Organic Carbon (%) 0.36
4.73 ≥ 2.7 54 90Total Nitrogen (%) 0.04 0.48 ≥ 0.2 46 77Available P
(ppm) 1 153 ≥ 30.0 49 82Potassium (me %) 0.08 1.23 ≥ 0.24 20
33Calcium (me %) 1.0 4.7 ≥ 2.0 18 30Magnesium (me %) 0.59 10.2 ≥
1.0 4 7Manganese (me %) 0.05 0.93 ≥ 0.11 3 5Copper ppm 0.01 7.15 ≥
1.0 56 93Iron ppm 2.86 309 ≥ 10.0 40 67Zinc ppm 0.48 21.6 ≥ 5.0 55
92
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16 Enhancing Soil Fertility for Greater Productivity
As regards, copper, iron and zinc they are inadequately supplied
in the soil in most of the farms. However to maintain adequate
levels of nutrients, regular applications of organic and inorganic
inputs to replenish the removed nutrients through crop harvest and
nutrients lost through avenues such as leaching, vaporization etc.
is encouraged. The micro nutrient copper, iron and zinc are low in
93 %, 67 and 92 % of the farms respectively. According to the
International Zinc Association, maize yields are reduced by zinc
deficiency and may result in reductions in yields of up to 40%
without the appearance of distinct leaf symptoms
(www:zinc.org/crops/resourceserve/zinc facts_sheet_maize, Landon,
1991).
It is recommended that during application of fertilizers in zinc
depleted soils, application of zinc fertilizers or using
zinc-fortified NPK fertilizers is an important practice for maize
growth to maintain high yields and profitability. Sulphate salts
containing copper, iron and zinc micro elements at 5-10 kg/h may be
mixed with other fertilizers during application. Foliar fertilizers
containing these elements may also be applied especially for
agri-business (high value) crops. Modification of pH closer to the
optimum pH may render the micro elements which were otherwise
unavailable available. However, most nutrient deficiencies can be
avoided in soils of pH ranges of 5.5 to 7.0, provided that the soil
minerals and organic matter contain the essential nutrients.
In Msambweni Sub county, non-acidifying and acidifying
fertilizers are recommended for application because most of the
farms have their pH above 6.0. Non acidifying fertilizers such as
Triple Super Phosphate (TSP), Single Super Phosphate (SSP),
compound fertilizers N:P:K such as 23:23:0, 20:20:0, 17:17:17,
Calcium ammonium nitrate (CAN) and Mavuno are recommended for areas
with pH below 6.5 and fertilizers such as DAP, urea, ammonium
sulphate (AS) in areas with pH above 6.5. This Sub County has
nitrogen, phosphorus, potassium and calcium inadequately supplied
by the soil. Farmers are encouraged to carry out regular soil
testing to monitor the pH and plant nutrients trends for future
soil fertility management. This will also give a direction into
specific types of fertilizers suitable for individual farms in
future.
Sub County general fertilizer recommendationsManure: 6
t/haPlanting: 250 kg/ha N: P: K 23:23:0Top dressing: 125kg/ha
CAN
4.2 Kilifi County 4.2.1 Ganze Sub CountyIn Ganze Sub county, the
soil pH ranges from extremely acid (4.22) to slightly alkaline
(7.09) (Refer to Table 4.2.1). Of the 30 farms sampled, 11 farms
(37%) have their soil pH below 5.5 and, therefore, not very
suitable for maize growth. Five farms have their pH below the most
critical pH of 5.0 for growth of maize. Where pH is below the most
critical pH, it should be raised with application of manures or
compost annually and avoidance of application of acidic
fertilizers. However, to prevent further reduction in pH,
application of acidic fertilizers such as DAP, Urea, Ammonium
sulphate, etc should be avoided in farms with pH < 5.5
In the Sub county, the soil organic matter content ranges from
low (0.12% Total Organic Carbon (TOC) to moderate (1.99% TOC) as
shown in Table 4.2.1. All farms have TOC below adequate level and,
therefore, low soil organic carbon matter content. The low soil
organic matter content results in low water holding capacity and
may lead to soil erosion by runoff water during the rains. This can
also impact negatively on the microbial activities in the soil.
Application of well rotten manure or compost will improve the
organic matter content in the soil. This will supplement the soil
nutrients and improve soil structure, water retention capacity and
soil microbial activities.
Table 4.2.1 shows the most limiting nutrients are nitrogen (100%
of farms), phosphorus (43% of farms), potassium (50% of farms) and
calcium (62% of farms) which are below adequate levels. Also
magnesium (28% of farms) is below adequate level in few farms.
Where macro nutrients are low, fertilizers containing those
nutrients should be applied to supplement what is available in the
soil.
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17Udongo Wenye Rotuba kwa Kuimarisha Uzalishaji
Table 4.2.1: Soil fertility status of Ganze Sub County.
Soil Parameter Min Max Target (critical) level
Samples with below
adequate levels
% of 60 samples
(30 farms)
pH 4.22 7.09 ≥ 5.5 22 (< 5.5) 37Total Organic Carbon (%) 0.12
1.99 ≥ 2.7 60 100Total Nitrogen (%) 0.04 0.19 ≥ 0.2 60 100Available
P (ppm) 5 123 ≥ 30.0 26 43Potassium (me %) 0.08 1.29 ≥ 0.24 30
50Calcium (me %) 0.9 6.9 ≥ 2.0 37 62Magnesium (me %) 0.11 7.13 ≥
1.0 17 28Manganese (me %) 0.02 0.89 ≥ 0.11 16 27Copper ppm 0.14
3.75 ≥ 1.0 48 80Iron ppm 4.06 34.1 ≥ 10.0 28 47Zinc ppm 0.52 73.1 ≥
5.0 49 82
As regards to manganese and iron, they are deficient in some
farms. Zinc is low in 82% and copper is low in 80% of farms.
According to the International Zinc Association, maize yields are
reduced by zinc deficiency and may result in reductions in yields
of up to 40% without the appearance of distinct leaf symptoms
(www:zinc.org/crops/resourceserve/ zinc_facts_sheet_maize; Landon,
1991).
It is recommended that during application of fertilizers in zinc
depleted soils, application of zinc fertilizers or using
zinc-fortified NPK fertilizers is an important practice for maize
growth to maintain high yields and profitability. Salts containing
the two micro elements like copper sulphate and zinc sulphate 5-10
kg/ha may be mixed with other fertilizers during application.
Foliar fertilizers containing these elements may also be applied
especially for agri-business (high value) crops. Modification of pH
closer to the optimum pH may render the micro elements which were
otherwise unavailable available. However, most nutrient
deficiencies can be avoided in soils of pH ranges of 5.5 to 7.0,
provided that the soil minerals and organic matter contain the
essential nutrients.
In Ganze Sub county, non acidic and acidic fertilizers are
recommended for application. 63% of farms in the Sub County have pH
between 6.5 and 7.09. Fertilizers such as N: P: K 23:23:0, 20:20:0,
17:17:17, Calcium ammonium nitrate, Diammonium phosphate (DAP),
etc. are recommended for application in this Sub County. The Sub
County also requires application of fertilizers with zinc
micro-nutrient which is low in majority of soils.
Sub County general fertilizer recommendationsManure: 8
t/haPlanting: 250 kg/ha N:P:K 23:23:0Top dressing: 125kg/ha CAN
4.2.2 Kaloleni Sub CountyIn Kaloleni Sub county, the soil pH
ranges from moderately acid (5.5) to moderately alkaline (7.65)
(Refer to Table 4.2.2). Of the 21 farms sampled, only 1 farm has
its soil pH above 7.0 and, therefore, not very suitable for maize
growth. No farms have their pH lower the most critical pH of 5.0
for growth of maize. Where pH is above the optimum pH of 7.0,
acidic fertilizers such as DAP, Urea, Ammonium Sulphate, should be
used.
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18 Enhancing Soil Fertility for Greater Productivity
In the Sub County, the soil organic matter content is low and
ranges from 0.3% Total Organic Carbon (TOC) to 1.12% TOC as shown
in Table 4.2.2. All farms have TOC below adequate level and,
therefore, low soil organic carbon matter content. The low soil
organic matter content results in low water holding capacity and
may lead to soil erosion by runoff water during the rains. This can
also impact negatively on the microbial activities in the soil.
Application of well rotten manure or compost will improve the
organic matter content in the soil. This will supplement the soil
nutrients and improve soil structure, water retention capacity and
soil microbial activities.
Table 4.2.2 shows the most limiting nutrients are nitrogen (100%
of farms), phosphorus (80% of farms), potassium (73% of farms) and
calcium (60% of farms) which are below adequate levels. Also
magnesium (27% of farms) is below adequate level in few farms.
Where macro nutrients are low, fertilizers containing those
nutrients should be applied to supplement what is available in the
soil.
Table 4.2.2: Soil fertility status of Kaloleni Sub County
Soil Parameter Min Max Target (critical) level
Samples with below
adequate levels
% of 30 samples
(21 farms)
pH 5.50 7.65 ≥ 5.5 < 5.5 0Total Organic Carbon (%) 0.30 1.12
≥ 2.7 30 100Total Nitrogen (%) 0.03 0.11 ≥ 0.2 30 100Available P
(ppm) 7 96 ≥ 30.0 24 80Potassium (me %) 0.10 0.51 ≥ 0.24 22
73Calcium (me %) 1.3 5.1 ≥ 2.0 18 60Magnesium (me %) 0.26 6.13 ≥
1.0 8 27Manganese (me %) 0.12 0.66 ≥ 0.11 0 0Copper ppm 0.71 1.63 ≥
1.0 21 70Iron ppm 5.72 58.4 ≥ 10.0 7 23Zinc ppm 0.62 30.6 ≥ 5.0 29
97
As regards to manganese, it is adequately supplied in the soil.
However, the micro nutrients such as copper, iron and zinc are
deficient in majority of farms. Zinc is low in 97% of farms.
According to the International Zinc Association, maize yields are
reduced by zinc deficiency and may result in reductions in yields
of up to 40% without the appearance of distinct leaf symptoms
(www:zinc.org/crops/resourceserve/ zinc_facts_sheet_maize; Landon,
1991).
It is recommended that during application of fertilizers in zinc
depleted soils, application of zinc fertilizers or using
zinc-fortified NPK fertilizers is an important practice for maize
growth to maintain high yields and profitability. Salts containing
the two micro elements like copper sulphate and zinc sulphate 5-10
kg/ha may be mixed with other fertilizers during application.
Foliar fertilizers containing these elements may also be applied
especially for agri-business (high value) crops. Modification of pH
closer to the optimum pH may render the micro elements which were
otherwise unavailable available. However, most nutrient
deficiencies can be avoided in soils of pH ranges of 5.5 to 7.0,
provided that the soil minerals and organic matter contain the
essential nutrients.
In Kaloleni Sub county, non acidic and acidic fertilizers are
recommended for application because some of the soils in the Sub
County have pH below 6.5 with only 1 farm with pH above 7.0.
Fertilizers such as N:P:K 23:23:0, 20:20:0, 17:17:17, Calcium
ammonium nitrate, etc. are recommended for application in this Sub
County. The Sub County also requires application of fertilizers
with zinc micro-nutrient which is low in majority of soils.
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19Udongo Wenye Rotuba kwa Kuimarisha Uzalishaji
Sub County general fertilizer recommendationsManure: 7
t/haPlanting: 250 kg/ha N:P:K 17:17:17Top dressing: 125 kg/ha
CAN
4.2.3 Kilifi Sub CountyIn Kilifi Sub County, the soil pH ranges
from moderately acid (5.52) to moderately alkaline (7.8) (Refer to
Table 4.2.3). Of the 29 farms sampled, only 7 farms (24%) have
their soil pH above 7.0 and, therefore, not very suitable for maize
growth. No farms have their pH above the most critical pH of 8.0
for growth of maize. Where pH is above the optimum pH of 7.0,
acidic fertilizers such as DAP, Urea, Ammonium Sulphate, etc.
should be used
In the Sub County, the soil organic matter content ranges from
low (0.2% Total Organic Carbon (TOC) to moderate (1.81% TOC) as
shown in Table 4.2.3. All farms have TOC below adequate level and,
therefore, low soil organic carbon matter content. The low soil
organic matter content results in low water holding capacity and
may lead to soil erosion by runoff water during the rains. This can
also impact negatively on the microbial activities in the soil.
Application of well rotten manure or compost will improve the
organic matter content in the soil. This will supplement the soil
nutrients and improve soil structure, water retention capacity and
soil microbial activities.
Table 4.2.3 shows the most limiting nutrients are nitrogen (100%
of farms), phosphorus (93% of farms) and potassium (74% of farms)
which are below adequate levels. Also calcium (11% of farms) is
below adequate level in few farms. Where macro nutrients are low,
fertilizers containing those nutrients should be applied to
supplement what is available in the soil.
Table 4.2.3: Soil fertility status of Kilifi Sub County
Soil Parameter Min Max Target (critical) level
Samples with below
adequate levels
% of 57 samples
(29 farms)pH 5.52 7.80 ≥ 5.5 0 (< 5.5) 0Total Organic Carbon
(%) 0.20 1.81 ≥ 2.7 57 100Total Nitrogen (%) 0.03 0.18 ≥ 0.2 57
100Available P (ppm) 1 92 ≥ 30.0 53 93Potassium (me %) 0.06 0.50 ≥
0.24 42 74Calcium (me %) 1.1 5.9 ≥ 2.0 6 11Magnesium (me %) 1.03
8.39 ≥ 1.0 0 0Manganese (me %) 0.11 0.57 ≥ 0.11 0 0Copper ppm 0.26
5.88 ≥ 1.0 30 53Iron ppm 2.82 42.5 ≥ 10.0 37 65Zinc ppm 0.84 31.4 ≥
5.0 47 83
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20 Enhancing Soil Fertility for Greater Productivity
As regards to manganese, it is adequately supplied in the soil.
However, the micro nutrients such as copper, iron and zinc are
deficient in majority of farms. Zinc is low in 83% of farms.
According to the International Zinc Association, maize yields are
reduced by zinc deficiency and may result in reductions in yields
of up to 40% without the appearance of distinct leaf symptoms
(www:zinc.org/crops/resourceserve/ zinc_facts_sheet_maize; Landon,
1991).
It is recommended that during application of fertilizers in zinc
depleted soils, application of zinc fertilizers or using
zinc-fortified NPK fertilizers is an important practice for maize
growth to maintain high yields and profitability. Salts containing
the two micro elements like copper sulphate and zinc sulphate 5-10
kg/ha may be mixed with other fertilizers during application.
Foliar fertilizers containing these elements may also be applied
especially for agri-business (high value) crops. Modification of pH
closer to the optimum pH may render the micro elements which were
otherwise unavailable available. However, most nutrient
deficiencies can be avoided in soils of pH ranges of 5.5 to 7.0,
provided that the soil minerals and organic matter contain the
essential nutrients.
In Kilifii Sub County, non acidic and acidic fertilizers are
recommended for application because some of the soils in the Sub
County have pH below 6.5 with only 7 farms with pH above 7.0.
Fertilizers such as N:P:K 23:23:0, 20:20:0, 17:17:17, Calcium
ammonium nitrate, Diammonium phosphate (DAP), etc. are recommended
for application in this Sub County. The Sub County also requires
application of fertilizers with zinc micro-nutrient which is low in
majority of soils.
Sub County general fertilizer recommendationsManure: 8
t/haPlanting: 250 kg/ha N: P: K 17:17:17Top dressing: 125 kg/ha
CAN
4.2.4 Malindi Sub CountyIn Malindi Sub county, the soil pH
ranges from strongly acid (4.93) to moderately alkaline (7.76). Of
the 30 farms sampled, only 4 farms (13 %) have their soil pH below
5.5 and, therefore, not very suitable for maize growth. One farm
have soil pH below the most critical pH of 5.0 for growth of maize.
Where pH is below the most critical pH, it should be raised with
application of manures or compost annually and avoidance of
application of acidic fertilizers. However, to prevent further
reduction in pH, application of acidic fertilizers such as DAP,
Urea, Ammonium sulphate, etc should be avoided in farms with pH
< 5.5. In the Sub County, the soil organic matter content ranges
from low (0.29% Total Organic Carbon (TOC) to moderate (1.77% TOC)
as shown in Table 4.2.4. All farms have TOC below adequate level
and, therefore, low soil organic carbon matter content. The low
soil organic matter content results in low water holding capacity
and may lead to soil erosion by runoff water during the rains. This
can also impact negatively on the microbial activities in the soil.
Application of well rotten manure or compost will improve the
organic matter content in the soil. This will supplement the soil
nutrients and improve soil structure, water retention capacity and
soil microbial activities.
Table 4.2.4 shows the most limiting nutrients are nitrogen (100%
of farms), phosphorus (88% of farms), potassium (48% of farms),
calcium (80% of farms) and magnesium (63% of farms) which are below
adequate levels. Where macro nutrients are low, fertilizers
containing those nutrients should be applied to supplement what is
available in the soil.
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21Udongo Wenye Rotuba kwa Kuimarisha Uzalishaji
Table4.2.4: Soil fertility status of Malindi Sub County.
Soil Parameter Min Max Target (critical) level
Samples with below
adequate levels
% of 60 samples
(30 farms)pH 4.93 7.76 ≥ 5.5 8 (< 5.5) 13Total Organic Carbon
(%) 0.29 1.77 ≥ 2.7 60 100Total Nitrogen (%) 0.03 0.18 ≥ 0.2 60
100Available P (ppm) 0.1 193 ≥ 30.0 53 88Potassium (me %) 0.06 0.81
≥ 0.24 29 48Calcium (me %) 0.5 8.5 ≥ 2.0 48 80Magnesium (me %) 0.04
5.04 ≥ 1.0 38 63Manganese (me %) 0.01 0.60 ≥ 0.11 12 20Copper ppm
0.20 5.40 ≥ 1.0 49 82Iron ppm 2.24 126 ≥ 10.0 43 72Zinc ppm 0.24
6.74 ≥ 5.0 52 87
As regards to manganese, copper, iron and zinc they are
deficient in majority of farms. Zinc is low in 87% and copper is
low in 82% of farms. According to the International Zinc
Association, maize yields are reduced by zinc deficiency and may
result in reductions in yields of up to 40% without the appearance
of distinct leaf symptoms (www:zinc.org/crops/resourceserve/
zinc_facts_sheet_maize; Landon, 1991).
It is recommended that during application of fertilizers in zinc
depleted soils, application of zinc fertilizers or using
zinc-fortified NPK fertilizers is an important practice for maize
growth to maintain high yields and profitability. Salts containing
the two micro elements like copper sulphate and zinc sulphate 5-10
kg/ha may be mixed with other fertilizers during application.
Foliar fertilizers containing these elements may also be applied
especially for agri-business (high value) crops. Modification of pH
closer to the optimum pH may render the micro elements which were
otherwise unavailable available. However, most nutrient
deficiencies can be avoided in soils of pH ranges of 5.5 to 7.0,
provided that the soil minerals and organic matter contain the
essential nutrients.
In Malindi Sub County, non acidic and acidic fertilizers are
recommended for application. 87% of farms in the Sub County have pH
above 6.5 where 14 farms have soils with pH above 7.0. Fertilizers
such as N: P:K 23:23:0, 20:20:0, 17:17:17, Calcium ammonium
nitrate, Diammonium phosphate (DAP), etc. are recommended for
application in this Sub County. The Sub County also requires
application of fertilizers with zinc micro-nutrient which is low in
majority of soils.
Sub County general fertilizer recommendationsManure: 8
t/haPlanting: 250 kg/ha N: P: K 23:23:0Top dressing: 125kg/ha
CAN
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22 Enhancing Soil Fertility for Greater Productivity
4.2.5 Rabai Sub CountyIn Rabai Sub County, the soil pH ranges
from moderately acid (5.5) to slightly acid (6.92) (Refer to Table
4.2.5). All sampled farms have their soil pH within an optimum
range of 5.5 to 7.0 and, therefore, suitable for maize growth. The
optimum soil pH range should be maintained with application of
manures or compost annually and avoidance of acidic fertilizers
such as DAP, Urea, Ammonium sulphate.
In the Sub County, the soil organic matter content ranges from
low (0.42% Total Organic Carbon (TOC) to moderate (2.24% TOC) as
shown in Table 4.2.5. All farms have TOC below adequate level and,
therefore, low soil organic carbon matter content. The low soil
organic matter content results in low water holding capacity and
may lead to soil erosion by runoff water during the rains. This can
also impact negatively on the microbial activities in the soil.
Application of well rotten manure or compost will improve the
organic matter content in the soil. This will supplement the soil
nutrients and improve soil structure, water retention capacity and
soil microbial activities.
Table 4.2.5 shows the most limiting nutrients are nitrogen (93%
of farms), phosphorus (80% of farms) and potassium (50% of farms)
which are below adequate levels. Also calcium (23% of farms) is
below adequate level in few farms. Where macro nutrients are low,
fertilizers containing those nutrients should be applied to
supplement what is available in the soil.
Table 4.2.5: Soil fertility status of Rabai Sub County
Soil Parameter Min Max Target (critical) level
Samples with below adequate
levels
% of 60 samples
(17 farms)
pH 5.50 6.92 ≥ 5.5 < 5.5 0Total Organic Carbon (%) 0.42 2.24
≥ 2.7 30 100Total Nitrogen (%) 0.05 0.22 ≥ 0.2 28 93Available P
(ppm) 5 60 ≥ 30.0 24 80Potassium (me %) 0.06 0.57