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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

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

National Accelerated Agricultural Inputs Access Program (NAAIAP)P. O. Box 30028, 00100NAIROBI.6th Floor, Hill Plaza Email: [email protected]:www.naaiap.go.ke

© 2014

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

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

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

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

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

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.

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


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


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


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.


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.


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.


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.


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.


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).


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.


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


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.


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.


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.


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


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


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.


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.


Table 4.2.1: Soil fertility status of Ganze Sub County.


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.


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


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).


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.


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


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


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).


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.


Table4.2.4: Soil fertility status of Malindi Sub County.


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).


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.



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


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

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