A PROPOSAL TO STUDY DIFFERENT SOIL ORGANIC AND INORGANIC
AMENDMENT OPTIONS FOR THE MANAGEMENT OF SALINE/SODIC
SOILS AND TEST HIGH VALUE CROP SUITABILITY FOR KALACHA
IRRIGATION SCHEME
1
TABLE OF CONTENTS
1.0
INTRODUCTION ............................................................................................................. 3
1.1
GENERAL BACKGROUND ......................................................................................... 3
1.2
STATEMENT OF THE PROBLEM .............................................................................. 4
1.3
JUSTIFICATION OF THE STUDY .............................................................................. 5
FIRST EXPERIMENT ................................................................................................................... 6
Table 1. Experimental layout .......................................................................................................... 7
SECOND EXPERIMENT .............................................................................................................. 7
THIRD EXPERIMENT .................................................................................................................. 8
STATISTICAL ANALYSIS .......................................................................................................... 8
REFERENCES ............................................................................................................................... 9
ANNEX1 BUDGET ABD WORKPLAN……………………………………………………… 10
2
1.0
1.1
INTRODUCTION
GENERAL BACKGROUND
Sporty agricultural research work in arid and semi-arid has been done, yet this area forms a fifth
of the county’s food production zone (Chepchirchir et al 1996). Over reliance on rain-fed
agriculture is identified as a contributor to food shortage and insecurity (GoK, 2002). However, a
high population growth rate of 2.9% (GoK, 2002) has resulted in increased land pressure that has
caused migration of farmers to the Arid and Semi-arid Lands (ASAL). Owing to frequent
prolonged droughts, farmers are turning to irrigation as a way of increasing agricultural
production in ASALS. . The problems emanate from the change of land use from pastoralism to
irrigated farming without adequate capacity to face the challenges of sustainable irrigation
development (Muchangi et al., 2005). This has resulted in farming being carried out on this
fragile land, with little knowledge or skills on its management. Soils in arid and semiarid regions
are characterized by relatively low organic matter (OM) content, high levels of salinity and
sodicity, high percentages of expandable clay minerals, and low vegetative cover; all which
decrease the stability of the soil structure (Ben-Hur, 2007, Wakindiki et al., 2001). About 40% or
about 25 million ha of the land of Kenya is covered by soils that have salinity and/or sodicity
problem(s). Of the area under irrigation, more than 50% is undergoing severe land degradation
through secondary salinisation and sodification mainly due to improper irrigation and soil
fertility management practices (Ngigi, 2002)
Many workers (Withers and Vipond, 1974, Mugwanja et al., 1995) stipulate that the success or
failure of any irrigated agriculture is determined by the extent to which salt and sodium problems
are controlled. Such soils frequently produce serious agricultural and management problems. Not
only do they bring the problem of toxicity, but also reduce soil quality, hence soil productivity.
Doran et. al., (1999) define soil quality as the capacity of the soil to function in sustaining
biological productivity, maintaining environmental quality and promoting plant and animal
health. In this context, understanding the effects of salt and sodium concentration on soil quality
within the root zone is imperative to ensure sustainable soil quality management under irrigated
agriculture (Bernstein and Ogada, 1966). Low irrigation efficiency can create high water table,
particularly in restricted drained conditions, thereby causing excessive accumulation of sodium
(Bui et al., 1996). In Addition, decline in soil organic matter and nutrient status of these soils
requires judicious management strategies for sustained productivity (Mugendi et al., 1999.
Success stories on rehabilitation of saline soils for crop production are few and studies show that
many irrigation schemes in Taveta area in the coast region have been out of operation since 1996
due to salinity and sodicity problems (Mugwanja, 1995). The management techniques that have
been experimented on are leaching, planting methods and use of different crops. Leaching and
drainage showed that crop production greatly improved in areas which had otherwise been
abandoned due to salinisation and sodification (Muchena, 1985; Mugwanja, 1997).However
these management specifications were not being followed due to high costs resulting in further
deterioration of soil physical conditions and poor crop yields. This necessitates research to come
up with cheaper strategies of management for these soils. Use of gypsum and organic manures
were seen to improve sodicity at Bura irrigation scheme; however the results were inconclusive
as the appropriate levels of application were not determined (Muchena, 1987). It was therefore
concluded that the irrigation scheme partly failed due to deteriorating soil conditions owing to
lack of proper soil amendments. These studies therefore indicate that a study of the degree and
necessary remedial measures of soil structure deterioration on irrigated saline and sodic soils is
required (Wanjogu et al., 2001). Other soil structural characteristics such as water infiltration rate
increased with any amendment containing gypsum, Effects of combining gypsum and FYM are
expected to give better results and will be tested in this study.
3
This study will therefore have four main strategies in addressing the management of saline and
sodic soils in Kalacha irrigation scheme in northern Kenya. These will be 1). Irrigation methods
where furrow and drip will be used. Alternate furrow irrigation moves the salt to un-irrigated
furrows away from the root zone while drip irrigation will be used to leach the salt below the
root zone 2). Plant-based approach using velvet bean (Mucuna pruriens) legume for N-fixation,
organic matter increase to improve soil structure and nutrient cycling 3) Fortified compost
organic input to improve the soil organic matter content, soil aggregate stability, available water
holding capacity and infiltration rate (IR) and 4) Use of gypsum to enhance sodium removal and
improve on soil chemical balances.
1.2
STATEMENT OF THE PROBLEM
The Kalacha irrigation scheme has seen agricultural production reducing by over 80% between
1984 and 2005 and currently its virtually non existent. This could be attributed to increased salt
and sodium concentrations in the soil. Currently, farmers are hesitant to grow crops in the
scheme, because they claim that water disappears before reaching the crops. They describe the
soils as soapy and smeary when wet, and extremely hard when dry. These soils have poor
structure, very high pH, which is too alkaline for crop growth, low organic matter content, high
electrical conductivity and high Exchangeable Sodium Percentage (ESP), suggesting extreme
saline-sodic conditions. Research results into management of saline soils in Kenya are not
documented and yet a study of some of the soils in these areas shows that salinity is a major
problem (Mugwanja, 1995, Muchena, 1989). The farmers are aware of soil salinity and its bad
effects. The problem is more pronounced in recent years leading to some farmers abandoning
farming altogether while others are growing forages under irrigation (Muya et al. 2009).
Increased salinization, loss of nutrients through leaching of N and degraded soil structure are
serious problems affecting crop productivity at Kalacha irrigation scheme. Consequently,
farmers are abandoning crop farming for fodder grass production at the schemes in Marsabit,
Kenya. A similar scenario is seen at irrigation projects that had been initially successful and have
in many cases declined in productivity and, in some cases, have been abandoned (Muchangi et
al., 2005; Ngigi, 2002). Salinity and sodicity are serious problems considering that over 40% of
Kenya’s land area is occupied by saline, saline-sodic and sodic soils, covering 2.9, 14.0 and 8.2
million ha respectively.
Onion (Allium Cepa) is one of the most potential export crops (Currah and Proctor, 1990;
HCDA, 2003) that can be grown under irrigation at the Kalacha irrigation scheme. Bulb onion is
considered to be the most important species of the Allium genus and is the third in terms of
vegetable production (Brewester, 1994). The production levels in Kenya are low averaging 11
t/ha as compared to Korea whose production is at 46 t/ha.
The main cause of decline in agricultural productivity in the scheme was found to be increased
salinization, loss of nutrients through leaching of N and degraded soil structure as a result of
wrong choice of irrigation methods and practices (Muya et al., 2009). Past studies in the area
indicate that the soils are high in sodium and salt concentrations (Muya et al 2009; Ngigi, 2002;
Mugwanja et al., 1995; Muchena, 1987). High sodium levels in the soil leads to the collapse of
the soil structure and blockage of soil pores. The accumulation of salts in the root zone could be
due to poor irrigation water, unsuitable irrigation methods and scheduling that does not take into
consideration soil type and infiltration capacity of the soil. This leads to poor soil aeration, poor
permeability and water logging thus not allowing leaching of these salts beyond the crop rooting
zone. The ultimate result is poor crop growth or complete crop failure (Landon, 1991). There is
also an imbalance of cations such as Ca, Mg and K ratios leading to artificial deficiency of these
4
cations. This could partly be attributed to the low water quality that is used for irrigation. Soil
analysis shows a high pH and low soil organic matter. It has been observed that farmers in the
scheme do not apply any organic fertilizers to the soil and the stover from the crops grown is fed
to livestock leaving little chance for organic matter to accumulate in the soil. The soil
amendments suggested in this study are aimed at addressing these problems.
1.3
JUSTIFICATION OF THE STUDY
Kenya’s onion production has stagnated at about 11t/ha for a long period (FAO, Statistics 2002)
while the top producing countries such as South Korea produce up to 46 t/ha. Kenya has
potential to produce up to 20 t/ha under irrigation. Production of high value crops such as onion
can earn the farmers some income and help alleviate poverty which is one of the Millenium
Development Goals (MDG) that the Government of Kenya (GoK) aims to achieve by 2015. This
is also in line with the vision 2030 which emphasizes on the need to improve the agricultural
sector which is the driving force of the Kenyan economy.
Irrigation activities were at their peak in Kalacha in the 1980s before a myriad of problems led to
the decline in agricultural production. Onion is important as a cash crop for this scheme as it is
less vulnerable to wildlife destruction compared to other crops. It is a potential crop for export
(Currah and Proctor, 1990) but little has been done in Kenya to increase its production levels.
Currently there is increased demand for onion following increased awareness of its medicinal
properties and reduction of imports from Tanzania and Eritrea. There is mounting evidence that
all members of the onion family have a positive effect in lowering incidences of heart disease.
Trials in the mid-nineties showed a drop in cholesterol levels of a test group when given garlic
powder. Nutritionally an average size raw onion contains 1.8g protein, 11.9g carbohydrates, 5g
sodium and 38g calcium per 100g.
Onions have a long shelf-life and can keep for up to 3 months after harvest when well dried and
aerated. They are also of high value, of short duration and with good planning one can have 3
crops per year. Under good management yields of up to 10 tons per acre can be obtained in
Kenya. Higher yields of to 23 tons per acre have been reported in Korea (FAO, 2002) and at Ksh
40 per kilogram in Marsabit town can fetch up to Ksh 400,000 per growing period. Onions can
be easily transported over large distances with minimum damage making marketing less of a
problem in its production.
The crop is therefore suitable as a cash crop for areas such as Kalacha that have poor
infrastructure and high levels of poverty. Production of this crop is however a challenge under
the saline – sodic soils of the area. Under the current production system at the site, farmers have
indicated that they are not sure of the crop varieties that are suitable for the area, hence the
decline in production.
This study will therefore address soil management and suitability of high value crops at the site
under the current climatic and appropriate irrigation conditions. There will be three main
approaches in addressing the salinity and sodicity of Kalacha irrigation scheme soils: (1) plantbased approach (including legumes for N-fixation, and deep roots to break soil hard pan and
grass shallow rooted) to improve soil structure and nutrient cycling, (2) organic inputs and
chemical amendments to improve the organic matter content, soil aggregate stability, soil water
holding capacity, soil quality and availability of nutrients to the crop (3) monitoring of water use
efficiency and leaching for salinity / sodicity management through the use of drip and furrow
irrigation.
OBJECTIVES OF STUDY
The study will have two main objectives:
5
1. To test different soil management options for the improvement of saline-sodic soils. This
will include soil amendments especially gypsum, vermicompost, compost manure,
fortified farm yard manure and crop based options (barley and mucuna) as green manure
2. To develop the sustainable and economically viable production systems through testing
high value crops suitability for Kalacha. Among the crops that are recommended from the
study are garlic, chilli, ginger, tumeric and onions that have a good local and national
market
Among the parameters that will be measured are:
1. To quantify the hydraulic conditions of the soil to provide data for calculating the
irrigation water application rate and time setting.
2. Crop yields under the different management options and identifying the best options
3. Evaluating the different for adaptability to the climatic and soil conditions
There will be 3 experiments in total. The objective of the first experiment is:
To compare the performance of onion under the different soil amendments for the improving
saline/sodic soils of Kalacha under two irrigation methods; drip and furrow.
FIRST EXPERIMENT
The study will investigate the effects of the following factors/ treatments
1. 2 irrigation methods (furrow or drip)
2. Cover crop type – shallow and deep rooted
Soil amendment – basically fortified compost (with gypsum, at rates determined in the
laboratory). 9 treatment combinations (gypsum fortified compost. Fortified compost at 3 rates
and gypsum at 4 rates, giving the following treatment combinations: (1) C0G0 (2) C0G25 (3)
C0G50 (4) C10G0 (5) C10G25 (6) C10G50 (7) C15G0 (8) C15G2.5 (9) C15G5 (10) C0G7.5
(11) C10G7.5 (12) C15G7.5); where C and G stand for compost and Gypsum, respectively. The
levels of gypsum that will be used in compost fortification will be determined in a laboratory
protocol by incubation of soils from the study site. The treatments will be arranged in a split-split
plot design. The 2 irrigation methods will be assigned to the main plots. The cover crop types
will be assigned to sub-plots while the soil amendments (12 treatment combinations) will be
assigned to sub-sub-plots. The sub-sub plots will measure 3m x 3m with 1m between plots. The
treatments will be replicated 3 times. Onion will be the test crop and at planting basal
phosphorus at a level of 50kg/ha will be applied. Soil moisture monitoring will be carried out in
treatments with compost levels at 0, 10 and 15 t/ha while other soil physical and chemical
analysis will be carried out in treatments with gypsum levels at 0, 2.5, 5 and 7.5 t/ha,
respectively.
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Table 1. Experimental layout
BLOCK
1
BLOCK
2
BLOCK
3
Furrow irrigation
9
1
5
7
3
10
12
4
11
6
2
8
Barley
Mucuna
2
10
5
6
3
12
8
9
4
1
7
11
Barley
Barley
11
1
2
9
4
12
5
6
3
8
Mucuna
6
8
5
10
7
1
12
2
Barley
2
4
10
9
7
1
3
11
Mucuna
Mucuna
Drip irrigation
4
7
1
10
9
8
11
6
12
2
5
3
1
4
10
8
3
7
5
11
12
6
2
9
Mucuna 12
2
8
3
9
10
1
5
6
4
7
11
11
3
4
9
Barley
6
5
7
10
8
3
11
2
12
4
9
1
12
5
8
6
Mucuna 11
1
2
5
4
10
3
7
9
8
6
12
Barley
5
11
4
8
1
3
7
12
7
10
2
1
7
4
10
6
5
8
3
9
11
12
One block will measure 77m long by 21m wide.
9
6
2
10
SECOND EXPERIMENT
Objective of this experiment is to evaluate the following:
The performance of different levels of vermin-compost on the quality and quantity of onion
under different levels of salinity.
The parameters that will be studies will be:
(a)
The effects of vermicompost on soil aggregate formation and stabilization.
(b)
The effects of vermicompost on salinity and sodicity levels.
(c)
The hydraulic conductivity of the different soils under the different vermicompost
levels
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Four levels of vermicompost will be tested, randomized and replicated 4 times in 4 blocks. Four
soil blocks will be used as per the level of salinity and sodicity as determined during the site
characterization.
Block1
Block2
V1
V3
V3
V2
V2
V4
V1
V4
Block 3
Block 4
V3
V2
V4
V3
V1
V4
V2
V1
THIRD EXPERIMENT
The third experiment will be done to determine the most suitable high value crops under the
climatic conditions of the area. 5 spices will be tested under the most promising soil amendment
practices. The 5 spices will be replicated three times at 4 sites.
STATISTICAL ANALYSIS
Data will be examined by ANOVA using the general linear model using the Statistical Analysis
System (SAS) version 8.1 of the SAS institute Inc. Cary, NC, USA. Separation of means will be
subjected to Tukey’s honestly significant difference test (Steel and Torrie, 1960). All tests will
be performed at the 0.05 significance level.
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(ed.) Climatic changes and water resources in the Middle East and North Africa. SpringerVerlag, Berlin.
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Currah, L and Proctor, FJ (1990) Onions in tropical regions. Natural Resources Institute Bulletin
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Doran J.W., Jones, AJ, Arshad, M.A. and Gilley, J.E. (1999). Determination of soil quality and
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and Maingi, P (2009). Characterization Of Mountains And Oasis Areas Of Kenya Arid And
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