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
Obanyi S.N., Muya E. Dub G. and Radiro M.
INTRODUCTION
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Over reliance rain-fed agriculture is a contributor to
food shortage and insecurity
Frequent and prolonged droughts, farmers are turning
to irrigation as a way of increasing agricultural
production in ASALS
High population growth rate of 3% has resulted in
increased land pressure and migration of farmers to
the ASAL = need for increased food production
Change of land use from pastoralism to irrigated
farming without adequate capacity to face the
challenges of sustainable irrigation production
Statement of the problem
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The Kalacha irrigation scheme – reduced crop productivity
by 80% between 1984 and 2005
Largely attributed to increased sodium, poor soil structure
and loss of plant nutrients
Abandoning crop production for pasture and trees
A similar scenario is repeated in many other irrigation
schemes in the ASAL
Statement of the problem cont…
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Crop production decline and this can be reversed if the soil
problems are addressed
There is imbalance of cations such as Ca, Mg and K leading to
artificial deficiency
Low organic matter as farmers do not apply any manure and the
stover is fed to livestock
About 40% or about 25 million ha of the land of Kenya is covered
by soils that have salinity and/or sodicity problem(s) with saline,
saline-sodic and sodic soils, covering 2.9, 14.0 and 8.2 million ha
respectively (Wamicha et al., 1986; Muchangi, 2005; Ngigi, 2002;
Muchena, 1987)
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 (Muchangi, 2005; Ngigi, 2002)
Statement of the problem cont…
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High sodium leads to soil dispersion, collapse of soil
structure, blockage of soil pores, low water infiltration,
water logging, poor aeration resulting in poor crop
growth and can lead to complete crop failure (Landon,
1991)
Degraded systems: A case for Hareri scheme, Mandera
Justification of the study
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Vision 2030 emphasizes improving agricultural sector, the driving
force of Kenyan economy. Expansion of irrigation at a rate of
4,000ha per year to have 1million acres under irrigation
Spices are low volume high value crops that can be produced as
cash crops and can contribute to reducing the high poverty levels
(65%)
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Spices can be value added and have a long shelf life, they are also
less susceptible to wildlife damage
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Increase farmer income thus help alleviate poverty one of the
MDGs
Justification of study cont..
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The area has a high potential for spices production and
there exists a big market potential as all spices used in
the area are imported
The imported spices for manufacturing are also
produced in areas with almost similar biophysical
characteristics as the study site
Kenya’s onion production has stagnated at about 11t/ha
(FAO, Statistics 2002) top producing countries such as
South Korea produce up to 46 t/ha and Tanzania is
about 35t/ha.
Kenya has potential to produce over 20 t/ha under
irrigation.
OBJECTIVES OF STUDY
The study will have three main objectives:
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To test different soil management options for the improvement
of saline-sodic soils. This will include 6 soil amendments i.e.
gypsum, vermicompost, compost manure, fortified farm yard
manure and crop based options (grasses and legumes) as green
manure
To develop sustainable and economically viable production
systems through testing high value crops suitability for Kalacha.
To disseminate results to the community and other
development agencies so that they can make informed decisions
on saline/sodic soils management in other irrigation schemes
METHODOLOGY
The study area location
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Kalacha
Irrigation
Scheme
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Kalacha irrigation scheme in
Marsabit District
lies between Longitude 2° 30’
N and Latitude 37° 30’ E.
300 meters above sea level,
temperatures of
approximately 300C
Bi-modal rainfall averaging
225mm per year
Wind speed is over 4m/s
Evaporation is about
2280mm/year
surrounded by Maikona, Asie
and Kargi hills and drains to
Chalbi desert
Soils
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Developed on lacustrine plain and
limestone sediments
Broadly classified into four soil
units with variations in depth,
aggregate stability, infiltration
rates and soil moisture holding
capacity
Generally they have low
aggregate stability of <50% at
10% within the top 10cm (Table
1)
Water holding capacity is low in
the sub-soil possibly due to
development of a hard pan
Table 1. Soil physical properties
Soil depth
(mm)
0-10
10-20
20-30
30-60
Aggregate
stability
(%)
10
9
9
5
Hydraulic
conductivity
(mm/hr)
10.7
9.6
6.3
4.8
Available
water
holding
capacity
8.8
7.6
7.1
3.4
Table 2. Soil chemical properties
Soil depth mm
Values at different depths
0-10
10-20 20-30 30-40 40-60
8.4
8.6
9.3
9.3
10.1
Electrical conductivity mS/cm 1.03
1.38
1.49
1.61
2.2
Carbon %
0.89
0.61
0.2
0.17
0.11
Nitrogen %
0.18
0.13
0.05
0.05
0.01
Phosphorous ppm
20
20
12
9
7
Potassium m.e.%
3.4
3.7
3.2
3.6
3.8
Calcium m.e. %
32.7
28.9
22.7
24.6
28.6
Magnesium m.e %
11.1
10.1
6.4
6.7
6.5
Sodium m.e %
6.4
9.6
12.6
14.7
12.9
Sum
53.6
52.3
44.9
49.6
51.8
ESP (Exchangeable Sodium
Percentage)
11.9
18.35 28.1
29.6
24.9
Soil pH-H2O (1:2.5)
Soil chemical properties
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The pH increases down the profile above 8.2 that
is used to classify sodic soils (FAO, 1988)
Chemical properties show low carbon and nitrogen
(Table 2)
Phosphorus levels decrease down the profile,
Calcium and Magnesium levels are high compared
to the critical levels
Electrical conductivity (ECe) increases with depth
being highest at 40-60cm but below 4 ds/cm
ESP % is high down the profile, soil is sodic
Methodology cont….
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1.
2.
The study will therefore have 3 main strategies in
achieving this:
Plant-based approach, a deep rooted legume to
address the soil hard-pan and a shallow rooted grass
Organic manure, vermicompost and compost will
address low organic matter, soil aggregate stability,
water holding capacity, available nutrients
3.
Water use efficiency and leaching of sodium salts
4.
Drip and furrow irrigation will be used
Parameters to be measured
 Crop yields under the different management
options and identifying the best options
 Quantifying the hydraulic conditions of the
soil to provide data for calculating the
irrigation water application rate and time
setting.
 Evaluating the different spices for adaptability
to the climatic and soil conditions
Soil moisture measurement
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neutron probe, moisture read at 4 depths = access
installed to 60 cm
Monitoring the soil water status on a regular basis
can identify soil structural problems, causing low
crop water use and consequently a poor yield
Neutron probe will be calibrated for the soil type
Measurements will be at 4 depths on selected plots
where soil analysis will be done
manure and compost making
 Manure/compost will be made using plant
materials, ash and animal manure as
described in IIRR, 2002
 When the manure is ready it will be
sampled and analysed to know its
nutritional value.
 Vermicompost will be made using locally
sourced earthworms
 Methods of analysis are described in
Okalebo et al., 2002.
Experimental Design and Treatments
Experiment 1
 2 irrigation methods (furrow or drip)
 Cover crop type – shallow and deep rooted
 Soil amendments – gypsum, vermicompost,
compost manure, farm yard manure and crop based
options (grasses and legumes) as green manure
 There will be 3 replications (blocks) = 12 plots
 Split plot design with irrigation methods as main plot
grass and legume treatments being main sub-plots
and amendments being sub-sub plots
 Test crop - onion
Experiment 2
The performance of 4 levels of vermin-compost
 The parameters that will be studies will be:
 The effects of vermicompost on soil
aggregate formation and stabilization.
 The effects of vermicompost on salinity and
sodicity levels.
 The hydraulic conductivity of the different
soils under the different vermicompost levels
 4 replications, RCBD
Experimental layout
Block 1
Block 2
V1
V3
V3
V2
V2
V4
V1
V4
Block 3
Block 4
V3
V2
V4
V3
V1
V4
V2
V1
Experiment 3
 5 spices will be tested under the current
soil conditions
 The spices include Garlic, onion, ginger,
Chilli and Tumeric
 The 5 spices will be replicated three
times
 RCBD
Statistical Data Analysis
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Treatment effects on sodium and salt control and
onion yield will be examined by ANOVA using the
general linear model
Statistical Analysis System (SAS) version 8.1 of
the SAS institute Inc. Cary, NC, USA
Treatments found to be significantly different will
be separated by Least Significance Differences
(LSD) (Steel and Torrie, 1960)
All tests will be performed at the 0.05
significance level.
Expected Outputs
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Salinity and sodicity at Kalacha through use of
different crop types, organic and inorganic soil
amendments controlled.
Higher spice yields and hence higher incomes for
the farmer realized
Better management of saline-sodic soils through
improved technologies and knowledge attained.
Farmers capacity built to produce and market
spices
Estimated budget: 1.418m