KIBOI MILKA NGONYO (BSe.) N5012120 112012
l'
r· \, •A Thesis Submitted in'Partial Fulfilment for the Degree of Master of Environmental Studies (Climate Change and Sustainability) in the School of
Environmental Studies of Kenyatta University
DECLARA TION
This thesis is my original work and has not been presented for a degree in any other university or any other award. 0part of this thesis may be reproduced without prior permission from the author.
Signed~ _
Milka Ngonyo Kiboi
Date_--cQ----'-(---'--1 o_q+---,--,,-I ~.:....>!,o_I.5__
DECLARA TION BY SUPERVISORS
We confirm that the work reported in this thesis was carried out by the candidate under our supervision.
Signed Mo~llth
Dr. Monicah Mucheru-Muna
Department of Environmental Science School of Environmental Studies Kenyatta University
Signed_--'I--~~-,---\-.f.L-.f-- __ Dr. Ngetich Kipc
Department
School of Agriculture Embu University College
Signed_-+-i+----4J~~~~_· _. _
DEDICATION
ACKNOWLEDGEMENTS
Ithank everyone who contributed to the writing of my thesis in one way or another. I express my deep gratitude to my supervisors; Dr. Monicah Mucheru-Muna, Dr. Ngetich Kipchirchir Felix and Dr. Daniel G. Mang'uriu for their academic guidance, advice and support throughout my studies. My special thanks go to Flemish Inter-University council (VLIR-UOS) through Prof. Daniel Mugendi (Principal Investigator), for offering me a comprehensive scholarship for my studies and research work. I specially thank Prof. Jan Diels, the Flemish University project promoter for his critical thinking in statistical analysis and contribution in my writing. Iam indebted to Dr. Jayne Mugwe, Prof. Chris Shisanya, and Dr. Stephen Wambugu fortheir input towards my work.
I also acknowledge Joseph Macharia, Esther Mugi, Irene Okeyo and David Njue for their advice and assistance in the course of my study. I am grateful to the field technicians; Boniface Murangiri and Silas Kiragu whose valuable help enabled me to conduct the fieldwork successfully. The farmers from Mbeere South and Meru South
I" sub-counties who agreed to offer plots for implementation of the strategies and recording the observations made as well as their responses. I wish to appreciate the patience and support of my family during my study period. I am grateful to the chairman and lecturers from the Department of Environmental Education for imparting into me necessary knowledge during my course work.
TABLE OF CONTENTS
DECLARATION ii
DEDICATION iii
LIST OF FIGURES ix
LIST OF PLATES x
LIST OF ACRYNOMS AND ABBREVIATIONS xi
ABSTRACT xii
CHAPTER 1 1
INTRODUCTION 1
1.1 Background of the Study 1
1.2.Problem statement and justification 3
1.3 Research questions 4
1.4 Research objectives 5
1.5 Research hypotheses : 5
1.6 Significance of the study 6
1.7 Conceptual framework 6
1.8 Limitation of the study 8
CHAPTER 2 10
I'
.LITERATURE REVIEW 10
2.1 Overview 10
2.2 Soil water conservation strategies 12
2.2.1 Mulching 13
2.2.2 Tied ridging 15
2.2.3 Minimum tillage 16
2.3 Rainfall distribution 18
2.5 Maize yield stability in farmer managed trials 22 2.6 Farmers' likelihood to take up soil water conservation strategies 24
2.7 Literature gaps : 27
CHAPTER 3 29
METHODOLOGY 29
3.1 Study area 29
3.2 Soil characteristics 30
3.3 Experimental design 31
3.4 Data collection 33
3.4.1 Maize harvesting 33
3.4.2 Soil sampling 33
3.4.3 Rainfall measurements 34
3.4.4 Interview schedule 35
3.5 Laboratory analysis 36
3.6 Data Analyses 37
CHAPTER 4 39
RESULTS AND DISCUSSION 39
4.1 Rainfall distribution in Mbeere South and Meru South sub-counties 39
4.2 Maize grain yield 42
4.3 Changes insoil organic matter. .47
4.4 Grain yield stability 51
4.5 Willingness totake-up soil water conservation strategies 55
4.5.1 Demographic characteristics 55
4.5.2 Awareness of soil water conservation strategies 57
4.5.4 Likelihood of Future utilization of Selected SWC strategies 64
CHAPTER 5 68
5.1 Summary of findings and conclusions 68
5.2 Recommendations 70
5.3Areas for further research 71
APPENDICES 92
Appendix 1:Experimental Layout in Mbeere South 92
Appendix 2: Experimental Layout inMeru South 93
Appendix 3: Interview schedules on assessment of the likelihood of farmers' to uptake the selected soil water conservation technologies in Embu and
LIST OF TABLES
Table 3.1: Description of themes of analysis 38
Table 4.1: Maize grain yield (Mg ha") under SWC strategies during short rains 2011, long rains 2012, short rains 2012, and long rains 2013 seasons in Mbeere
South and Meru South sub-county .43
Table 4.2:.Total organic matter at the beginning and end ofthe experiments in Mbeere
South and Meru South sub-counties .48
Table 4.3 Least square means of grain yields in Mg ha-1 under SWC strategies in
Mbeere South and Meru South sub-counties 53
Table 4.4 Social demographic characteristics of farmers implementing the on-farm trials in Mbeere South and Meru South sub-counties 56
Table 4.5 Mean scores of farmers on performance of SWC strategies based on their effects on maize grain yield in Mbeere South and Meru South sub-counties.
LIST OF FIGURES
Figure 1.1 Conceptual framework showing the interrelation among the variables 7
Figure 3.1: Map showing the study area (The on-farm trials were implemented within the red circle in Meru South and Mbeere South) 29
Figure 4.1: Cumulative rainfall at Mbeere South a) and Meru South b) during short rains 2011 and long rains 2012 seasons, and short rains 2012 and long rains
2013 seasons 40
LIST OF PLATES
Plate 3.1: Some selected SWC strategies: Plot with tied ridges (a) Mulched plot (b).32
AEZs ANOVA ASL C CA CT ENSO FAO FURP
ID-I
HHH IPCC LM LR LSD MC MG MT N P SAS I' SOC SOM SR SSA SWC TR UM UNESCO
LIST OF ACRYNOMS AND ABBREVIATIONS
Agro-ecological Zones
Analysis of Variance
Above Sea Level
Carbon
Conservation Agriculture
Conservation Tillage
El Nino/Southern Oscillation
Food and Agriculture Organization
Fertilizer Use Recommendation Project
Household
Household Head
Intergovernmental Panel on Climate Change
Lower Midland
Long Rains
Least Significance Difference
Mulching
Mega grams
Minimum Tillage
Nitrogen
Phosphorous
Statistical Analysis Software
Soil Organic Carbon
Soil Organic Matter
Short Rains
Sub-Saharan Africa
Soil Water Conservation
Tied ridging
Upper Midland
United Nations Educational Scientific and Cultural
ABSTRACT
1.1 Background of the Study
Agriculture provides 70% of employment and 35% of Sub-Saharan Africa's (SSA) gross domestic product (World Bank, 2000). Per capita food availability in SSA has decreased over time, and the region suffers from wide spread food insecurity
(Beintema & Stads, 2006). This is because small-scale farmers prevail in a climate of increasing population pressure, declining levels of agricultural productivity and rapid natural resource degradation together with decreased amounts of rainfall (Rockstrorn, 2000). The reliance on uncertain rainfall and exposure to climate risk characterize the livelihoods of roughly 70% of the region's population; and frustrate efforts to sustainably intensify agricultural production, reduce poverty and enhance food security (Hansen et al., 2011). In Mbeere South and Meru South sub-counties (Kenya) majority of the small-holder farmers depend on rain-fed agricultural production (Mugwe et al., 2009).
APproximately 65% of land in SSA is subjected to degradation resulting to low yield levels experienced by farmers oscillating around It ha" for major staple grains (Rockstrorn et al., 2009). Additionally, the rigorous soil preparation by hoe or plough together with the removal or burning of crop residues leaves the land exposed to climatic hazards such as rain and wind leading to land degradation causing low crop
yield levels (Benites et al., 1998). In the two sub-counties, in Embu and Tharaka
impoverishment caused by continuous cropping with inadequate addition of fertilizer
and/or manure, and soil erosion on steep slopes (Mugwe et al., 2004).
Drought is one of the main causes for low agricultural productivity in SSA (McCann,
2005). The impact of drought stress on crop productivity is severe when farmers have
no management alternatives (FAO, 2002) of soil moisture. Miriti et al. (2012)
suggests that soil water conservation strategies such as mulching and tied ridging are
possible strategies of rainwater conservation likely to improve agricultural
productivity. For example, tied ridging improves positive partitioning of rainwater for
better utilization by crops (Nuti et al., 2009) and enhances crop response to rainfall
and nutrient (Jensen et al., 2003). Wang et al. (2011) reported that water content at the 100-200 em soil depth was significantly higher for ridge tillage than for
flat-planting system because of improved runoff efficiency. In addition, the use of in-situ
practices such as conservation tillage and mulching has been recommended
(Stroosnijder, 2009). Straw mulch with the conventional planting system for maize
production showed some benefit in retaining soil water (Wang et al., 2011).
Therefore, soil water conservation is vital as majority of the population in SSA make ,
-a living from r-ain-fed -agriculture (FAO, 1995).
Soil organic matter is an important soil component, which can directly or indirectly
affect almost all the soil properties (Weil & Magdoff, 2004). Regular tillage breaks
down soil organic matter (SOM) through mineralization, more so in warmer climates
(Kirschbaum, 1995), thus contributing to deteriorating soil physical, chemical and
holding capacity and susceptibility to water erosion is increased through increased
runoff (Thierfelder & Wall, 2010). Declining SOM also diminishes the ability of the
soil to release nutrients in approximate synchrony with crop demand (Drinkwater &
Snapp, 2007). The physical effects of conventional tillage also adversely affect soil
structure, with consequences for water infiltration and soil erosion through runoff, and
create hardpans below the plough layer (Thierfelder &Wall, 2009).
There are many biophysical and socio-economic constraints to smallholder farmers in
adopting conservation agriculture (CA) (Giller et al., 2009) and it is necessary to
develop effective strategies to transfer the emerging technologies to them. Adoption
of a conservation practice is mainly influenced by the characteristics and
circumstance of the farmer, and the characteristics of the practice, majorly its
advantage over existing practices and farmer's ability to try the practice (Greiner et
aI., 2009). Results from on-farm research are reported to provide far more useful
information about the performance of a technology under real farm conditions
compared with results from on-station trials (Giller et al., 2009; Baudron et aI., 2012).
Therefore, there is need to examine performance of various soil water conservation
tillage systems under farmers' conditions and farmers likelihood to take up soil water
conservation measures.
1.2. Problem statement and justification
Farmers in Mbeere South and Meru South Sub-Counties have experienced a decrease
incrop yields in the recent decades (Mugwe et al., 2009). This has been as a result of
water storage (by the soils) and poor water harvesting techniques. These lead to high
rate of runoff generation, low soil profile water recharge, and loss of soil nutrients essential for crop growth hence decline in crop yield. The problem can be attributed to
climate variability and low adaptive capacity by farmers in different agro-ecological
zones (Jaetzold et al., 2007). To increase maize yield in the region and reduce
production risks, retention of soil water needs to be enhanced through use of SWC
strategies in farmers' fields.
During crop growth, soil moisture is one of the important agricultural inputs at key stages as nutrients can be added to soil using organic and inorganic fertilizer. Implementing SWC strategies has a potential of improving rainfall efficiency, increase and stabilize maize yields, and improve SOM. Some of these SWC strategies
are mulching tied ridging, and minimum tillage. However, their success depends on rainfall amounts, farmers' tillage practices, and practicing of the SWC strategies. In the study area, few studies have been carried out on the subject, and the performances
of these strategies under farmers' conditions are not well known/documented. The
I' study therefore sought to explore the influence of the selected SWC strategies on maize yields, yield stability and SOM under on-farm conditions and the likelihood of
farmers to take up the selected SWC strategies.
1.3 Research questions
The study sought to answer the following questions;
ii) How do the selected SWC strategies affect SOM in farmer managed trials
in different AEZs?
iii) How stable is the maize yield over time under the selected SWC strategies
in farmers' managed trials in different AEZs?
iv) What is the likelihood of taking up the selected SWC strategies by farmers
in Mbeere South and Meru South sub-Counties?
1.4Research objectives
The broad objective of the study was to assess effects of selected SWC strategies on
maize yield under on-farm conditions in Embu and Tharaka-Nithi counties in Kenya.
The study addressed the following specific objectives:
i) To determine the effect of the selected SWC strategies on maize yields under
farmers' conditions in different agro-ecological zones.
ii) To evaluate the effect of the selected SWC strategies on soil organic matter in
different AEZs.
iii) To evaluate maize yield stability under the selected SWC strategies in farmer
managed trials in different AEZs.
iv) To assess the likelihood of the farmers to take up the selected SWC strategies
in Mbeere South and Meru South sub-counties.
1.5 Research hypotheses
The study was guided by the following hypotheses:
i) The selected SWC strategies have a significant positive effect on maize
ii) The selected SWC strategies significantly increase SOM in the different
AEZs.
iii) The selected SWC strategies enhance maize yield stability under farmers'
conditions in different agro-ecological zones.
iv) Farmers are most likely to take up the selected SWC strategies in Meru
South and Mbeere South sub-counties.
1.6 Significance of the study
The findings from this study will contribute to scientific knowledge on effects of the
selected SWC options on maize yield and SOM, maize yield stability, and the
likelihood of the farmers to take up the SWC strategies. In addition the findings will
contribute scientific knowledge to the field of soil and water conservation research
and be used to recommend feasible coping mechanisms for future climate variability.
The findings will also contribute in choosing and implementation of the best fit SWC
option in SOM improvement, yields increment and stability by the farmers across the
two sub-counties that experience bimodal rainfall seasons. The results will be useful
to researchers and other stakeholders in recommending effective SWC strategies and
,-development of improved and sustainable production technologies.
1.7 Conceptual framework
A major problem being experienced in the study area is declining crop yields (maize
productivity) due to lack of SWC strategies, poor farming practices, worsened by
Poor farming practices Climate variability
(Rainfall)
• Reduced soil water content • Declining SOM and nutrients • High run off
Declining Maize yields
Selected SWC strategies Influence on maize yields
Effects of selected SWC on maize yield stability SWC effect on SOM
Uptake of SWC measures Increased maize yields
Figure 1.1 Conceptual framework showing the interrelation among the variables
Low and erratic rainfall with increased intensity leads to high runoff rates hence soil
loss. Poor farming practices and failure to practice SWC measures by smallholder
farmers also leads to soil loss, declining SOM, low inherent water storage in the soils
hence decline in maize yields (Figure 1.1). Runoff and soil loss are problems common to most cropland in the world, especially those with unstable aggregates in the surface
horizon both from the standpoint of sustainability and offsite environmental damage
(Rhoton et al., 2002). Implementing sound SWC measures can lead to a reduction in
runoff amounts, improve SOM and enhance maize yield stability (Figure 1.1).
reduction in soil loss, which in turn leads to reduced land degradation and reduced
crop water stress (Temesgen et al.,2009).
1.8 Limitation of the study
The main limitation of this study was the scanty availability of information on effects
of the selected SWC strategies on maize yield under on-farm conditions in SSA
tropical conditions. Hence the study heavily borrowed from on-site research stations
researcher managed field experiments findings and extrapolated in trying to
understand the on-farm conditions. Due to the limited number of researcher design
ed-farmer managed experiments, there was paucity of information on yield stability
1.9 Definition of terms
Agro-ecological zone: is a land resource mapping unit, defined in terms of climate,
landform and soils, and/or land cover, and having a specific range of
potentials and constraints for land use.
Agricultural drought: When there is insufficient soil moisture to meet the needs of a
particular (maize) crop at a particular time.
Climate variability: Fluctuations inelements of climate such as rainfall, temperature,
air pressure, wind flow patterns and ocean currents, and may be caused
by either anthropogenic activities or natural processes.
Conservation tillage: Collective umbrella term given to minimum-tillage, retention
of surface cover by residue and/or ridge-tillage, to denote that the
specific practice has a conservation goal of some nature.
Dry spells: Absence of rainfall in periods ranging between 10-28 days during crop
growing season.
Household: Persons living under the same roof and whose labour, income and
expenditures were considered as part of the household's economic
conditions
Meteorological drought: When cumulative rainfall for the growing season is below
the amount required to produce a crop and occurs for a period above
four weeks hence could result incomplete crop failure.
On-farm trials- A set of treatments being assessed over arange of environments
Runoff: The portion of rainwater not infiltrated into the soil during and after a
CHAPTER 2
LITERATURE REVIEW
2.1 Overview
Sub-Saharan Africa is one of the hydro climatic regions subject to extreme rainfall variability, water scarcity and a large dependence on soil moisture in the root zone
(Kaumbutho et al., 2009). Soil moisture depends on infiltrated rainfall that contributes to evapotranspiration flow in rain fed farming systems. When soil moisture is reduced
seedlings are less likely to develop and crop yield is negatively affected (Hassanli et
al., 2009; Jin et al., 2010). According to Gicheru et al. (2004) effective use of any
rainfall requires appropriate soil management practices and tillage methods that enhance rainfall penetration and conserve adequate soil water for plant growth. Water
availability is therefore critical to plant growth, thus changes in precipitation strongly
influence agricultural productivity.
Sub-Saharan Africa is highly vulnerable to extreme climate events such as dry spells and droughts, perhaps more so than any other region in the world (Taddele et al.,
2015). Farming systems practiced in areas such as in Mbeere South and Meru South; often suffer from agricultural droughts and dry spells caused by management induced water scarcity (Rockstrom et al., 2007). These agricultural droughts are much more common than meteorological droughts, and they have a number of different causes, including water losses from the field via run-off, drainage and evaporation
continuing to improve rain-fed dry-land agriculture with optimised water management
isa key priority to guarantee food security and sustainability (Bu et al., 2013).
Maize grain yields in smallholder farms in arid and semi-arid areas of Kenya are
below 1.0 Mega grams ha-J with frequent crop failures due to drought (Rockstrom et
al., 2009). To minimize effects of reduced maize yields and crop failure due to
droughts, there are calls to promote on field rainwater harvesting technologies to
subsistence farmers. Such technologies work by retaining surface runoff within the
field, thereby altering soil water status in the root zone (Wiyo et aI., 2000). Surface
runoff accounts for up to one quarter of rainfall as a result of crust and pan formation,
high intensity rainfall events and poor soil cover (Fowler & Rockstrom, 2001) while
evaporation losses account for half the rainfall which is worsened by intensity of
cultivation and soil degradation.
Besides controlling soil erosion and reducing loss of fertile top soil, application of soil
and water conservation measures, have a potential to increase soil organic carbon
(SOC) concentration and hence improve soil fertility (Srinivasarao et aI., 2013). Soil
organic matter sustains many key soil functions by providing the energy, substrates,
and biological diversity to support biological activity, which affects soil aggregation
and water infiltration (Franzluebbers, 2002). Biazin & Stroosnijder (2012) reported
that introduction and appropriate implementation of rainwater harvesting techniques
may encourage farmers to invest in soil improvements for improved crop production
performance of SWC measures in enhancing maize productivity in the study area that
is experiencing low and erratic rainfall.
2.2 Soil water conservation strategies
Implementation of soil water conservation strategies contributes to intensification of
agricultural systems, enhances food production and alleviates poverty (Adgo et a/.,
2013). For instance, minimum tillage and mulching strategies have been reported to
offer an opportunity for sustainable management of smallholder agro-ecosystems of
SSA since soil conditions are improved and crop yields increased (Mupangwa et al.,
2013). Rejani &Yadukumar (2010) found treatments with soil and water conservation
structures reduced erosion and soil loss. The threat of increasing dry-spell occurrences
suggest an urgent need to change from the traditional cultivation practices in SSA to
more efficient and robust approaches which promote soil and nutrient conservation
(Rockstrorn, 2003).
The semi-arid and dry sub-humid regions of SSA experience a problem of low yield
" levels averaging 20-50% below what is achievable (Enfors et a/., 2011). Water
shortage in the root zone during critical crop development stages has been a major
constraining factor (Sieger & Stroosnijder, 2008). It is ascribed to highly variable
rainfall regime, leading to frequent dry spells (Barron et al., 2003), large unproductive
flows inthe field water balance (Rockstrom & Falkenmark, 2000) which is related to
climatic factors, soil characteristics, and land management (Enfors et a/., 2011). In
Kenya, Maize (Zea mays L.) is an essential food crop but despite its importance, the
due to low and erratic rainfall, high evapotranspiration rates, low soil fertility and land
degradation (Jaetzold et al., 2007). Renewed efforts to address low crop production
through the introduction of soil and water conservation tillage into the production
systems have been suggested (Gachene and Kimaru, 2003; Jaetzold et a/., 2007;
Kaumbutho &Kienzle, 2007).
2.2.1 Mulching
Mulch impedes the evaporation of water from soil surface by protecting it from direct
solar radiation and by greater resistance to air flow across the soil surface (Dardanelli
et aI., 1994). This result in lower losses of moisture to evaporation in untilled soils
covered with mulch compared to tilled soils. Mulching shades the soil; serves as a
vapour barrier against moisture losses from the soil, slow surface runoff and increase
infiltration (Mulumba & Lal, 2008). It enhances soil water retention essential for
emergence and growth of crops. Several studies have revealed that mulching is an
effective method in manipulating crop growing environment to increase yield and
conserve soil moisture, enhance organic matter content, control weeds, reduce soil
erosion and improve soil structure (Opara-Nadi, 1993; Hochmuth et al., 2001;
"
Awodoyin & Ogunyemi, 2005).
Mulching as a S
we
strategy has been shown to be effective in reducing the risk ofcrop failure at field level in the semi-arid regions due to better capture and use of
rainfall (Bationo et al., 2007). Sharma & Acharya (2000) revealed that application of
mulch improved the seed-zone and root-zone moisture status, and raised the minimum
improved rainwater capture in Northern Ethiopia. Dahiya et al. (2007) reported a
reduction in soil water loss in the mulching treatment on an average by 0.39mm/d
compared to a control treatment therefore enhancing soil profile water shortage. The
water conserving effect of mulch on the surface of soil can therefore induce a
substantial yield increase when drought stress is an issue (Huang et al., 2008). There
is a major advantage of improving soil and surface conditions that allow for better
water infiltration through maintenance of crop residues on the surface soil as mulch,
especially insub humid and semi-arid regions (Unger, 1994).
Previous studies done in researcher managed experiments have also shown that
mulching can change crop water consumption patterns, thereby increasing the crop
yield and water use efficiency (Zhu et al., 2000; Fang et al., 2009). The presence of
crop residue mulch at the soil atmosphere interface has a direct influence on
infiltration of rainwater into the soil and evaporation from the soil (Erenstein, 2002)
leading to improved soil water supply for crops. A study conducted in Mbeere South
sub-county in on-site station showed that mulching and minimum tillage have great
effects on maize emergence and yield (Gicheru et al., 2004). Zhang &Yang (2008)
reported that the application of liquid film mulch increased maize yield by 17.4%
compared with the control treatment. However, Araya (2011) found that mulching
increased soil water but not crop yields. There exists little information on
performance of maize production under mulching strategy through farmer managed
2.2.2 Tied ridging
In tied ridging strategy, ridge furrows are blocked with earth ties spaced a fixed
distance apart to form a series of micro catchment basins in the field (Wiyo, 2000).
These created basins retain surface runoff within the field. Under erratic rainfall
conditions, the ridges harvest rainwater and store it in the maize root zone for use
during dry spell (Wiyo et al.,2000). In addition, incorporation of tied ridges in maize
areas has been reported as an effective practice to increase ground water recharge
(Hunink et al.,2012).
Several studies conducted in on-station sites have reported the significant role of
tied-ridges in improving water and crop productivity in arid and semi-arid regions
(Biamah et al., 1993; Jensen et al., 2003; Motsi et al., 2004; McHugh et al., 2007;
Araya & Stroosnijder, 2010). For instance, according to Jensen et al. (2003) 42%
increase in maize grain yield was obtained using tied ridging during normal to slightly
dry rainfall conditions without any nutrient inputs compared to control practice. Tied
ridges in Zimbabwe doubled yield in comparison to the conventional tillage without
ridges (Motsi et al., 2004). In a study by Araya & Stroosnijder (2010), tied ridging
I' reduced runoff and improved grain yield and rainwater use efficiency significantly in
below average rainfall conditions. The increase of the soil water in the root zone by at
least 13% resulted in a significant improvement in yield. Greater crop yields in ridge
tillage relative to conventional tillage have been reported in Ghana (Akinyemi et al.,
2003) and in Kenya (Miriti et al., 2005). In a study by Miriti et al. (2012) tied-ridge
tillage treatments recorded greatest soil water content due to the capture and storage
et al. (2008) showed that with various rainfall conditions, i.e., 230, 340, and 440 mm, the spring maize yield was increased with ridge and furrow rainfall harvesting
cultivation by 82.8, 43.4, and 11.2%, respectively when compared with flat cultivation.
However, some studies in researcher designed-researcher managed trials have shown
that crop response to ridge tillage can be both negative and positive depending on
rainfall characteristics (Jensen et al., 2003, Sijali & Kamoni, 2005). Ridges will take
longer to wet after a dry spell, and germination of a crop planted on ridges is quite
often observed to be slower than a crop planted on flat land (lbraimo &Munguambe,
2007). Another drawback of this strategy is that on clay soils, ridge tillage can induce
water logging, and later on followed by mass movement (FAD, 1993) leading to total
crop loss. In severe storms, poorly designed ridge-furrow systems may fail the row
catchments can over-top and the water flow unimpeded down the slope causing soil
loss (McHugh et al., 2007). These factors should be taken into consideration before
selecting tied ridging as a soil water conservation strategy in a given area.
2.2.3Minimum tillage
Minimum tillage (MT) is a practice in which the soil is tilled to some extent but not
fully inverted with the aim to maximize soil infiltration and soil productivity, and
minimize water losses while conserving energy and labour (Rockstrom et al.,
2002).The strategy typically implies that substantial amounts of residues remain as
mulch (Sullivan, 2003). The management of soil through MT affects the storage of
and on crop production (Wang et al., 2003; Huang et al., 2005; Lenssen et al., 2007).
A participatory on-farm experiments on conservation farming systems for smallholder
farmers carried out over 3-4 years (1999-2003) in Ethiopia, Kenya, Tanzania and Zambia showed a consistent maize grain yield increase for conservation farming
practices over conventional practices over time (Kaumbutho et al., 2009).
Under MT grain yield is affected by climate, crop type, and soil drainage (Liu et al., 2013). In Zambia, farmers adopted minimum tillage methods to trap moisture,
improve soil quality, and minimize soil erosion, resulting in a 10-fold yield increase
and decreased dependency on rain (Oxfam, 2006). Farmers in the United States
countries, Latin America, Europe and certain parts of South Asia adopted MT system,
as a means to improve soil conservation, reduce labour and energy needs and to
increase yield levels (Derpsch, 2001). However, according to Chen et al. (2011)
maize yields tend to be lower for minimum tillage relative to conventional tillage
when the soils are poorly drained or the climate is cool humid. Kassam et al. (2012)
showed that yields from conservation tillage can be greater when the soils are well
drained or the climate is warm-dry
Poor farming practices that reduce soil water content essential for crop growth in the
study area have lead to a substantial decline in maize grain yield. Therefore,
implementation of sound SWC strategies in the farmers' fields' is vital so that the
2.3 Rainfall distribution
Rainfall amount and distribution are key variables influencing crop productivity in
rain-fed farming (Srinivasarao et al., 2013). Highly erratic patterns of rainfall
distribution often lead to more extreme wet and dry cycles of soil water contents thus
limiting crop growth and productivity to some extent (Wang et al., 2011). Agriculture
in semi-arid areas suffers from strong annual variations in crop yield due to
dependence on rainfall volume and distribution during the growing season.
Expectations about future rainfall trends are greatly varying and uncertain (Doll,
2002) and this affects the forecasts about crop water use in future climate scenarios
since it strongly depend on rainfall trend and distribution. The frequency distribution
of rainfall and temperature may change as a result of climate change, including
changes in climate variability and the intensity of extreme events which may lead to
more severe droughts or flooding, depending on the timing and distribution of rainfall
(Chikozho, 2010). Long-term rainfall records from Eastern and Southern Africa
indicate that inherent replenishment of soil moisture storage may occur as a result of
rainfall (Cooper et al., 2008). According to Lobell &Field (2007), changes in climate
have already decreased crop yields in several regions and are estimated to have
I'
reduced global maize production by 12 Megatonnes (Mt) year" between 1981 and
2002. A study done in the region by Mucheru-Muna etal. (2010) showed that maize
yields were greatly affected by the amounts and distribution of rainfall. Hence intermittent and prolonged droughts are among major causes of yield reduction in
Soil water, whose major input is rainfall, is a basic requirement for crop growth from sowing to maturity (Khuram & Rasul, 2011). Conservation of soil water and improved crop water use efficiency can be achieved with conservation tillage (Lal, 1991; Carter, 1994; Tebrugge, 2001). Synchronizing maize growth with seasonal soil water supply is often the first and foremost step in rain-fed agricultural production. This has led to the promotion of on-field rainwater harvesting technologies such as tied ridging due to erratic rainfall and drought that have been experienced throughout the 1990's (Wiyo et al., 1999). Wang et al. (2011) concluded that rainwater conservation using furrow planting with straw mulching on the ridge system had the advantages of preserving rainwater storage and matching maize water use and soil water availability during the growing season. A study by Stephens & Hess (1999), found in wet years, maize yields were not affected by water harvesting, but declined
slowly with increasing proportion of rainfall lost as runoff. In dry years, the yields were very low because of severe drought, often as a result of extremely irregular rainfall events. Increase in the mean annual rainfall also increases
sa
c
stocks (Srinivasarao et al., 2013). Therefore, to build resilience for coping with future water related risks and uncertainties such as prolonged dry spells and droughts and secure I'the water required for food production, there is need for water management in rain fed agriculture (Rockstrorn et al., 2010).
climate variability (Ngetich et al., 2014). The high variability in rainfall has been
partly attributed to El-Nifio/Southern Oscillation (ENSO) which causes abnormally
wet or dry short periods (Camberlin et al., 2001).
2.4 Changes in soil organic matter
Soil organic matter represents the remains of roots, plant material and soil organisms
in various stages of decomposition and synthesis, and is variable in composition
though occurring in relatively small amounts (Ryan et al., 2001). Quantity and quality
ofSOM and its major component, humus, is influenced by soil management practices.
Therefore, SOM is critical for agricultural productivity and essential in controlling
erosion, water infiltration and conservation of nutrients (Franzluebbers, 2002).
Increased SOM improves nutrient (Mrabet et al., 2001) and water holding capacity of
the soil (Mrabet et al., 2003). Srinivasarao et al. (20l3) reported that maintaining or
improving SOC concentration in rain fed dry-land agro-ecosystems is a major
agronomic challenge. However, data from long-term experiments (Bolliger et al.,
2006; Menichetti et al., 20l3) show that increasing SOC concentration by C
sequestration and stabilization positively affects yields of several crops.
Addition of mulch to crop fields increases moisture retention in the short run and
contribute to higher levels of SOM over time which improves soil water holding
capacity (Giller et al., 2006). Soil organic matter maintenance and increase are more
pronounced in CA systems due to the retention of organic material as crop residues on
the soil surface (Thierfelder & Wall, 2009). Various studies have shown that
aI., 1990; Paustin et al., 1997; Saroa & La I, 2003). Organic matter levels build up
under conservation tillage, both as plant residues remain on the field and as organic
matter is not oxidized to the same degree when the soil is not inverted, improving the
soil's aggregate stability and potentially also its capacity to retain moisture ( Enfors et
a/., 2011). According to Hobbs (2007), mulch retention, combined with minimum
tillage could be the best management practice for SOM restoration and control of
erosion with astute fertilizer application presenting an opportunity for SOM build-up
in maize-based smallholder systems (Dube et aI., 2012) of the Eastern Cape.
Soil carbon storage helps to stabilize atmospheric CO2 concentrations and promotes
improved drainage; soil structure, water holding capacity, and other important soil
properties that. improve agricultural productivity (Lal et a/., 2004). In tied ridging
technology, any organic matter or fertilizer which is present at or near the soil surface,
gets concentrated in the ridge and thus be greater benefit to the crops (Meijer, 1992).
Results from Chivenge et al. (2007) showed that TR being a least disruptive tillage
practice had the greatest amounts of soil organic C, 20.4 mg C g ·1 soil for red clay
compared to clean ripping and CT technologies. I'
Soil organic matter and its different portions are essential in optimizing crop
production, minimizing negative environmental impacts and thus improving soil
quality. Tillage-based conventional agriculture is assumed to lead to SOM decline,
water runoff and soil erosion (Derpsch et al., 1991). Many studies have shown that
minimum tillage practices can result in greater aggregation and higher standing stocks
1990; Havlin et al., 1990, Kushwaha et al., 2001). No tillage impacts soil organic
carbon (SaC) stock by reducing disturbance which favours the formation of soil
aggregates and protects sac encapsulated inside these stable aggregates from rapid
oxidation (Six et al., 2000). Additionally, MT modifies the local edaphic
environment: bulk density, pore size distribution, temperature, water and air regime
that might restrict SaM biodegradation (Kay & Vanden-Bygaart, 2002). Work by
Bescansa et al. (2006), in semi-arid Spain linked higher available soil water content
with the greater SaM and changes in pore-size distribution under minimum tillage. A
continuous long term study by Jin et al. (2011) demonstrated that no tillage was
associated with a substantial and significant improvement in soil properties including
SaM and nutrient status in annual double cropping areas of North China Plain
compared toconventional tillage.
Soil organic matter deteriorates with continued poor tillage practices, therefore soil
and water management practices have to be implemented and adapted to ensure
cropping systems that add organic matter to the soil. There are few studies that have
I' been conducted in SSA as well as in the study area to investigate the effects of these
SWC strategies on SaM quantities over time under on-farm conditions.
2.5 Maize yield stability in farmer managed trials
Yield stability can be defined as either static or dynamic (Becker & Leon, 1988);
whereby in static stability, the performance of a crop remains unchanged regardless of
the environmental conditions and in dynamic stability, a crop performance changes in
relative performance of various SWC strategies, stability of yields over time is an
important attribute to consider. Several studies concentrate on average crops and
overlook yield stability which is one of the important factors for food security
(Piepho, 1998). The evaluation of crop yields should therefore incorporate yield
stability across variable climatic conditions (Swift, 1994) to make recommendations
precise.
Predicting and/or control of crop yield variability are challenges experienced in crop
production research (Batchelor et al., 2002). Stability of crop yield is influenced by
agricultural management and environmental factors (Berzsenyi & Dang, 2008).
According to Fikere et al. (2008) yield stability is perceived by farmers as the most
important socio-economic aim to minimize crop failure especially in marginal
environments. Crop yield stability with less risk of crop failure may provide incentive
to invest in crop management practices that improve yields (Barron, 2004) as it also
implies more predictable returns. The sustainability of a cropping system is most
effectively evaluated by long-term experiments that simulate management practices
and conditions encountered in farmers' fields (Singh &Pala, 2004).
Higher yield stability is associated with higher yields and decreasing variation in
yields. In Shukla's stability variance model (Shukla, 1972); treatment with a small
stability variance is considered as most stable. Conservation agriculture has been
suggested by its proponents to offer solutions that ensure higher and more stable
yields (Giller et al., 2009). More effective agricultural practices to utilize the rains,
are necessary. Padgham (2009) argues that opportunities for participatory research
exist that improve the relevance of technologies to local needs and marginal
environments to achieve higher and more stable yields. However, Tollenaar & Lee
(2002) found that high grain yield and yield stability are not mutually exclusive.
There is, therefore, need to evaluate yield stability under farmers conditions using
various SWC strategies.
On-farm trials are designed to test performance of agricultural technologies in
comparison with farmer's own practices, under real farm conditions and under farmer
management. Mutsaers et al. (1997) argued that trials conducted under maximum
farmer management are the only valid way of testing new technology provided the
farmers treat the trial fields in the same way as their other fields. From on-farm trials
increasing yields has been the major objective in most crop production systems,
improving yield stability is also an important objective of agricultural progress (Slafer
&Kernich, 1996). Little attention has been given on stability of maize yield infarmer
managed trials using the selected SWC strategies in SSA as well as inthe study area; ,.,
hence the need for this study.
2.6 Farmers' likelihood to take up soil water conservation strategies
The take up of soil water conservation strategy is the decision of the farmer to
implement it or not. Numerous challenges hinder smallholder farmers in taking up
SWC strategies thus it is necessary to implement on-farm trials so as to transfer the
emerging technologies to them (Johansen et al., 2012). To achieve substantial
innovations in SSA has been a challenge in recent decades, a trend that authors
attribute to low awareness, and negative attitudes among other factors (Khisa et al.,
2007; van Rijn et al., 2012). The traditional top-down extension approach has been
identified as one of the key factors hampering adoption of conservation tillage
(Nyagumbo, 1998; Shetto, 1998) and the best approach to transfer SWC strategies
involved participatory strategies including farmer managed trials. The low adoption
rates of SWC strategies has also been due to diverse perceptions of farmers regarding
the threat of soil erosion, household size, land and farm characteristics, technology
attributes, land quality differentials and tenure insecurity (Bekele &Holden, 1998).
The decision to take up an innovation is a risky choice for farmers' as they must make
a choice between alternatives whose consequences are uncertain and the attached
probabilities may not be known (Greiner et al., 2009). According to Abadi et al.
(2005), risk perceptions and risk preferences impact majorly on the information
acquisition and learning-by-doing process phase in the adoption process by farmers.
Technologies for improving maize yields have been developed in the past, but some
I' have not been adopted because they do not match with the maize production resource
base of farmers (Mokwunye et al., 1996). Possible determinants of adoption of SWC
technologies has been suggested by various studies to include technology
characteristics, farmers' attitudes toward risk, adoption costs, availability of capital
(human and social resources), labour availability, and land tenure (Sunding &
The impacts of conservation tillage such as increased soil moisture availability and
hence increased crop yields have facilitated its adoption by smallholder farmers in the
semi-arid area for example, Machakos district of Kenya (Muni, 2002). Adoption of
appropriate management practices can also lead to higher rates of organic carbon
particularly in high rainfall regions since soils of the tropical regions have low C
sequestration rate because of high temperatures (Srinivasarao et al., 2012). However,
it is a large challenge for agricultural development to facilitate the adoption of
conservation farming as past experiences have not shown any general guidance on
how and why adoption occurs (Knowler &Bradshaw, 2007). In SSA adoption of the
MT system is limited by the traditionally narrow focus of conservation farming on
minimum tillage system that minimize disturbance of soil (Dumanksi et al., 2006).
According to Johansen et al. (2012), the best way to change mind set towards
minimum tillage is through technology demonstration and evaluation on-farm carried
out in a multi-disciplinary mode and with farmers. Farmers' decisions on technology
adoption are often conditioned by attractive short-term crop yield responses. For
instance, tied ridging strategy is not likely to be taken up by smallholder farmers
unless it improves soil water status for the crop during dry or drought years and will
not lead to water logging, ridge destruction and excessive nutrient leaching in a wet
year (Wiyo et al., 2000). Globally TR is a widely adopted technique for rain-fed
agriculture and soil conservation (Nyakatawa et al., 2000; Zhang et al., 2007).
An on-farm action research approach experiment by Kaumbutho et al. (2009) proved
to be important in raising farmers' interest and commitment where they were involved
assessing results, and adapting the system. For this reason, it is vital to fully involve
farmers in implementation of SWC technologies. This will usually entail larger plots,
simplified trial designs and control treatments that reflect farm practice and respect
farmer knowledge, practices and conditions (Mashavira et al., 1995). A study done in
Ghana in farmer managed trials, increasing farmers' participation resulted in a high
rate of uptake of conservation tillage (Boa-Amponsem et al., 1998). A study done in
the central highlands of Kenya by Macharia (2012), found out that on-farm
demonstration was the most preferred and best delivery method for training farmers
on the soil fertility technologies. Also the Assessment Report Four (AR4) states that
the ability of agricultural communities in SSA to cope better with current climate
variability and adapt to future climate change must be enhanced (IPCC, 2007).
Therefore, farmers should be driven as much as possible by their own intrinsic
motivation to put effort in conducting and adapting SWC strategies which positively
influences their continued use. This requires a stepwise approach in SWC including
farmer to farmer training and on-farm trials (Kessler et al., 2008). In the study area,
the likelihood of the farmers' to take up the SWC strategies implemented in their
fields is not known. Thus it was paramount to understand the likelihood of farmers in
the study area to practice these strategies in order to promote uptake and utilization of
the strategies for sustainable agriculture.
2.7 Literature gaps
Studies on the effects of the selected soil water conservation strategies on maize
area it is not yet known. There are very few studies on effects of SWC strategies on
maize yield stability in researcher designed-farmer managed trials in SSA. The review
also identified that in the study area effects of the selected SWC on maize yield
stability strategies has not been researched and hence not known. Farmers' likelihood
to take up the selected SWC strategies in the study area is also unknown and thus the
3.1 Study area
CHAPTER 3
METHODOLOGY
The study
was carried out in Meru South and Mbeere South sub-counties (Figure
3.1).
Meru South sub-county
is located in the Upper Midland Zone two (UM2)
and Upper
Midland Zone three (UM3) agro-ecological zones,
on the eastern slopes of Mt.
Kenya
at an altitude of 1,500 m above sea level (a.s.l) with an annual mean temperature of
20°C and a total annual rainfall of 1,200-1,400 mm (Jaetzold
et a/.,2007). The
long
rains
(LR) lasts from March through June,
and short rains (SR) from October through
December.
It is a predominantly maize growing zone
with smallholdings ranging
from 0.1 to
2
ha with an average of 1.2 ha per household (Shisanya
et a/., 2009).•
..
,
•
.
.
I , I i Iii i I " o 1875375 750KiIomet«9
AEZs _IL5
Kamburu Dam
r:::::J
Kindsruma DamCJLH1
c=:J
lM3
c=:J
lM4
CJLM5•
.•
Masing Dam
'-..
•
.
.
•
•
..
.
•
i I I 5 1Q 20 Kilometerg
Figure .: Map of the study
area (The on-farm trials were implemented
within the red
Mbeere South sub-county lies in the Lower Midland Zone 4 (LM4) and Lower
Midland Zone five (LM5) agro-ecological zones, on the eastern slopes of Mt. Kenya
at an altitude of 700 to 1200 m a.s.! (Jaetzold et al., 2007) with the mean annual temperature ranging from 20.7° to 22.5°C with high evapotranspiration rates. The
average annual rainfall is between 700 to 900 mm and is bimodal with LRs lasting
from mid March to June and SRs from late October to December, hence two cropping
seasons per year. Cropping systems in Mbeere South are predominantly maize-based,
with beans as the preferred legume for intercrop, although cowpea, groundnut and
green grams are gaining importance.
3.2 Soil characteristics
The two sub-counties have contrasting soil fertility (Mucheru-Muna et al., 2010) as
they are located in different AEZs. The soils in Meru South are predominantly humic
Nitisols, a typical deep and weathered soil with moderate to high inherent fertility
(Jaetzold et al., 2007). These soils are of higher fertility hence better for agricultural
production compared to soils in Mbeere South. The humic Nitisols in Meru South
have an average rate of 0.15% of organic carbon, 0.02% of the total nitrogen, and
0.01 % of phosphorus (Jaetzold et al., 2007). Soil texture in Meru South is majorly
clay with the particle size distribution of clay being 72% and silt 20% (Ngetich,
2012).
The soils in Mbeere South are mostly plinthic Cambisols (FAa, 1988). Cambisols are
brown with cambic B horizons as the main feature, layers are differentiated and
weathered than most of the other soils of the humid tropics. Cambisols contain an
average of 0.04% of organic carbon, of total nitrogen 0.01%, and 0.001% of the total
phosphorus (Jaetzold et al., 2007). The soil texture in Mbeere South is sandy clay
with the particle size distribution ofclay being 41 % and silt 12% (Ngetich, 2012).
3.3 Experimental design
The experiments were set up In the farmers' fields whereby twelve farmers
implemented the trials from each sub-county. The trials were researcher designed and
farmer managed (Coe, 1997) hence allowing collection of biophysical data. Twelve
farmers' were selected in each sub-county guided by the proximity to the installed
automatic rain gauge in the nearby sites representative of the area. The trials were run
for four consecutive cropping seasons, short rains 2011 (SRI 1), long rains 2012
(LRI2), short rains 2012 (SR12), and long rains 20 13(LR13). Each farmer acted as an
experimental unit and they were blocked in threes based on agro-ecological similarity
and proximity to each other. Each selected farmer tested a different strategy against
the conventional practice. The experiments followed an unbalanced randomized ,.,
complete block design (RCBD) with three SWC treatments replicated four times
(Appendix 1and Appendix 2), while the control was implemented by every farmer.
The control was homogenous in the different farmers' fields whereby there was
continuous weeding and removal of crop residues. The SWC treatments were: tied
ridging (Plate 3.1a), mulching (plate 3.1b), and minimum tillage in each sub-county.
Maize (Zea mays L.) was the test crop. Maize variety planted in Meru South was
HSIS with a growing period of 120-1S0 days recommended for high-potential areas.
variety used
i
n Mbeere South was DR 04; a short duration seed with maturity between
85 to 100 da
y
s
.
The spacing was 0.90 m between maize rows by 0
.
60 m within
t
he
rows and being a semi-arid area the spacing was larger due to higher water
competition among the crops
.
Three maize seeds per hill were planted and thinned out
to two seedlings per hill two weeks after emergence.
Plate.:
Some selected SWC strategies
:
Plot with tied ridges (a) Mulched plot (b
)
Fertilizer was applied at the recommended rate of 60 kg N ha-
l(FURP
,
1987
).
Phosphorus was applied as Triple Super Phosphate (TSP) at planting at the rate of 90
kg N ha". Maize stover (residue) was used for mulching and applied immediately
I'
after germination at a rate of 5 Mg ha-
1(dry matter basis)
.
The farmers utilized mulch
obtained from preceding season since maize is commonly grown
i
n the area
.
Tied
r
i
dges were constructed at the beginning of the first cropping season and any damages
repaired accordingly for the following seasons. For the farmers undertaking minimum
tillage, no p
l
oughing was done on the plots
.
Instead
,
planting holes were only dug
where seeds were planted. Automatic rain gauge with a data logger had been installed
3.4 Data collection
The farmers implementing the experiment trials were trained on land preparation,
planting, weed control, standard agronomic practices and data collection at the start of
each cropping season. They were also provided with notebooks for recording the
observations made. Follow-up and monitoring visits on the observations recorded
were done fortnightly.
3.4.1 Maize harvesting
Maize grain and stover were harvested at maturity from a net area of24 m2and 21 m2
in Mbeere South and Meru South, respectively, after leaving out guard rows and the
first and last maize plants in each row to minimize the edge effect. The cobs in each
plot were separated from the stover and fresh weight determined. The cobs were then
air dried to 12.5% moisture content. Maize grains were then separated from the cobs
through hand shelling and weighed to give the net grain weight. Maize stover was cut
at ground level and total above ground fresh weight determined. Grain yield was
measured in Kg ha".
3.4.2 Soil sampling
Soil samples were obtained from the two sub plots (the SWC treatment plot and the
control plot) in the farmers' fields. The initial sampling was done in August 2011
before establishment of the experiments while the final sampling was done in August
2013 at the end of the experiments. The soil samples were collected using an Edelman
auger at a depth of 0-15cm. The soil samples were packed in plastic bags with marked
put in a freezer to minimize microbial activity and later on dried in an air-forced oven
at 30°C. When dry the soil samples were then cleaned off stones and plant residues.
Samples were then ground in a stainless steel soil grinder and passed through a 2-mm
sieve and analysed for organic carbon.
3.4.3 Rainfall measurements
Daily rainfall measurements were taken using an automatic rain gauge with a 0.2 mm
resolution installed at nearby sites representative of the area (Plate 3.2). The rain
gauge was mounted on a post in an open area so that there was no obstruction of rain
pattern. Measures were taken to ensure that it was on a level position and clear of
overhead structures. The stand on which it was mounted on was free from vibration.
Data logger in the rain gauge was launched, read out using HOBO ware Pro Version
3.2.2 and data exported to excel worksheets for further processing. The rain gauge
status was regularly checked to ensure proper functioning and exhausted batteries
Plate. An automatic rain gauge
3.4.4 Interview schedule
To determine the likelihood of farmers to take up the selected SWC strategies, the
study adopted a qualitative research approach due to their small number (24 farmers).
The targeted respondents were the farmers involved in the trainings' and implemented
the experiments and recording observations from the on-farm trials. A minimum data
set interview schedule (Appendix 3) was used to collect information on the
demographic characteristics of the households such as the farmers' age, gender,
education levels, and years of farming experience, total farm size and size of land
cultivated after the experimental period. Semi- structured in-depth interviews were
conducted to investigate on their awareness of SWC technologies, key factors in
choice of other SWC strategies they implement, benefits and challenges experienced
during implementation of SWC measures. Farmers' likelihood to take up the SWC .
implementing them in future and increment of acreage under the strategy (Appendix
3).
3.5 Laboratory analysis
Organic carbon was determined using modified Walkley and Black wet oxidation
method described by Ryan et al.(2001). One gram of air dried soil passed through 0.5 mm sieve were weighed into 500 ml wide mouth beaker and 10ml of 1 N potassium
dichromate added into the flasks using a burette. In a fume cupboard, 15 ml
concentrated sulphuric acid was rapidly added directing the stream into the
suspension. The flasks were swirled gently at first until all soil and reagents mixed
and then more vigorously for about one minute. They were then allowed to stand for
exactly 30 minutes. About 200 ml of distilled water was added and allowed to cool,
after which 10 ml 85% orthophosphoric acid and finally 10 drops diphenylamine
indicator were added. The solutions were titrated with 0.5 N ammonium ferrous
sulphate solution. Soil organic matter was then derived from the determined organic
carbon percentage and calculated as using Equation 1 and Equation 2.
0/0OrganicC arbon =....;~'lI:..:.!::.;al'l.:::'/{'--·":..:~-a:.:.:m.:.t:p.:.:[s'-X_.~f_:<_::I_X_l0_-_s_>(1_0_0
We [Equation 1]
Where: VBlank=Volume (ml) of ferrous ammonium sulphate solution required to titrate the blank
VSampl?=Volume (ml) of ferrous ammonium sulphate solution
required to titrate the sample
3 x 10-3=Equivalent weight of carbon
100=percentage
M=Molarity of ferrous ammonium sulphate solution (approximately
0.5M i.e. 10Nblank).
%Sell OrgClnic MrLtter (w/w) = 1.724 X% Tta! Organic Carbon
[Equation 2]
3.6 Data Analyses
Maize yield data and soil data were subjected to analysis of variance using the
General Linear Model (GLM) SAS 9.2 software (SAS Institute, 2004) to obtain an F
value of the effect of the model. Pair-wise comparison of soil organic matter content
differences between the start and the end of the experiments was analysed using t-test.
Differences between treatment means were examined using least significance
difference (LSD) atp= 0.05. Analysis of variance using the Mixed procedure in SAS
I' 9.2 was used to evaluate maize yield stability, in which the factors site (2 levels),
season (4 levels) and treatment (4 levels) and their interactions were considered as
fixed effects, while farmer nested within season was considered as a random effect
(block effect). Diagnostic plots and Levene's test were performed by subjecting the
absolute values of the residuals from the basic mixed model to a regular analysis of
variance with the fixed effect only (Littell et al., 2006). Then using a 'REPEATED'
statement procedure 'Mixed', Akaike's information criterion (Akaike, 1974) was
multiple comparison procedure. The different layers of variability were effectively
incorporated and accounted for by the mixed model. Mixed-model analysis allowed
multi-layered data information to be combined from multiple experiments conducted
over time and space (Virk et al., 2009).
3.7 Theme Analysis
Demographic characteristics data from the interview schedules were summarized
using descriptive statistics such as frequency, means, and cross tabulations. Themes of
analysis were searched within the data to explain farmers' likelihood to take up the
SWC strategies.
Themes
Table 3.1: Description of themes of analysis
Description Awareness of SWC strategies
Determinants oftaking up SWC strategies
I'
Likelihood of Future
utilization of Selected SWC strategies
This theme included the farmers' ability to mention the selected SWC strategy implemented in the study period and to give examples of other SWC technologies apart from what was implemented. It also focused on the decisive factors used by farmers in the choice of SWC measure to implement.
This theme included the benefits that farmers' gained from practicing SWC measures in comparison with the conventional tillage and the challenges experienced during the implementation. It also focused on whether the farmers found the implemented strategy worth.
CHAPTER 4
RESULTS AND DISCUSSION
4.1 Rainfall distribution in Mbeere South and Meru South sub-counties
There were disparities in total rainfall and distribution between seasons in both
sub-counties (Figure 4.1). Cumulatively, Meru South received higher amounts of rainfall
in all seasons compared to Mbeere South. In Mbeere South, cumulative rainfall for
SRI 1 and LRI2 seasons was 654 mm, whereby 358 mm was received during SRI 1,
11 mm during off season, and 285 mm during LRI2 (Figure 4.la). In Meru South cumulative rainfall received during SRI 1 and LR12 was 1519 mm, 874 mm received
700 (a)
~ 600
~
::
500
~
.5
::...
400=
.5
300=
~ \000200
.5
~ ~ 1000
1110112 1/12/12
._._
.
_
...•--SRII &.LRI2
_. - SR12&LR13
1/2/13 1/4/13 1/6/13
1600
~ 1400
~
~ 1200
:
.§
1000·s
800.5
600 400 200o
1110112--
~\000
.5
~ ~
Rainfall dates
(b)
/L- ~~--~~~---~
Figure 4.1: Cumulative rainfall at Mbeere South a) and Meru South b) during short
rains 2011 and long rains 2012 seasons, and short rains 2012 and long
rains 2013 seasons
During SR12 and LR13, Mbeere South cumulatively received 609 mm whereby
I
,.,.-331mm was received during SR12, 5mm during offseason and 273mm during LR13.
. - .- .- .- .- . - . -- SRI I&LR12
" .- - . - SR12&LR13
I
,
1/12112 112/13 1/4/13 1/6/13
Rainfall dates
In Meru South cumulative rainfall received during SR12 and LR13 was 970 mm,
total, during SR12 and LR 13 seasons both sub-counties received lesser amounts of
rainfall compared to SRI 1 and LRI2 seasons. Dry spells were also experienced in
both sites in other cropping seasons whereby, Meru South had a dry spell of 10 days
during SR II and 15 days during SR 12 season. Mbeere South had dry spells of 12 and
23 days during SRI 1 and 10 days during SRl2 season. The differences in rainfall
amounts and number of months the rain was received between short rains seasons and
long rains seasons within each sub-county indicates the distinction between the two
cropping seasons per year.
These semi-arid and sub-humid agro-ecosystems, suffer from high frequency of
droughts and dry spells (Barron et al., 2003; Rockstrom et al., 2010). A
meteorological drought was experienced during LR13 in both sites. Mbeere South
experienced a meteorological drought of 55 days while Meru South had a
meteorological drought of 57 days leading to a major decline in rainfall amount
during the season. A meteorological drought was defined as the absence of rainfall for
a period above four weeks during the growing season. Meru South also experienced a
I'
meteorological drought during LRl2 of 30 days at the beginning of the season while
Mbeere South had a dry spell of 25 days in the same season. Nevertheless, there was
still good harvest in Meru South since there was good distribution of the rainfall after
the drought in comparison to Mbeere South. According to Twomlow et al. (1999)
distribution and reliability are often more important than total rainfall. In addition,
soils in Meru South have better physical and chemical properties and characteristics
