Semi-arid Eastern Kenya Research Articles

Farmyard manure and arbuscular mycorrhiza fungi inoculation enhanced growth and fruit fibre productivity of Calotropis procera in semi-arid eastern Kenya

A greenhouse experiment was conducted at the South Eastern Kenya University (SEKU) to determine the effects of farmyard manure (FYM) and arbuscular mycorrhiza fungi (AMF) inoculation on growth, vigor, shoot nutrient uptake (SNU) and AMF root colonization percentage (RC%) of potted Calotropis procera (Calotropis) seedlings. A field trial was laid out to determine the effects of the treatments on growth and fruit fibre productivity of the transplanted seedlings. The experiments were laid out in a split-split-plot design with a 2*2*2 factorial arrangement and 3 replications. The main plot factor constituted 2 Kenyan Calotropis provenances, Kibwezi and Tharaka. The sub-plot factor comprised of FYM and without FYM application while the sub-sub-plot factor involved inoculation with mixed strains of commercial AMF and without inoculation. Farmyard manure (FYM) and the integration of FYM and AMF inoculation (FYM*AMF) significantly improved Calotropis seedlings’ growth, vigor, SNU and AMF RC% in the greenhouse. However, FYM*AMF was comparatively superior to solely FYM and AMF. There were positive correlations of AMF RC% with growth, shoot dry weight (SDW) and SNU of the seedlings at the end of the greenhouse experiment. Under field conditions, FYM and FYM*AMF significantly enhanced growth and fruit fibre productivity of Calotropis plants than the controls, barring a few cases. The study recommends the use of FYM and FYM*AMF in Calotropis seedlings’ production in the drylands of Kenya. Future research should investigate the persistence of the introduced commercial AMF strains in the soil using molecular techniques.

Striving to be resilient: the role of crop-poultry integrated system as a climate change adaptation strategy in semiarid eastern Kenya

Climate change continues to pose significant challenges to food security and livelihoods of smallholder farmers specifically in semi-arid regions. One approach that holds prospects for climate risk management is climate-smart agriculture (CSA). CSA has concentrated on crop practices with little attention to livestock especially indigenous (village) chickens as a potential practice that can be combined with crop agriculture. This study considers the adoption of three CSA practices: improved maize seeds (IS), soil management (SM), indigenous chicken (IC) enterprise and their various combinations. Using survey data collected from 300 farming households in semiarid Kenya, we estimate the impact of integrated crop-poultry system adoption on food security and farm income using multinomial endogenous treatment effect models. Robustness checks are conducted using alternative identification strategies. Results show that, generally, the adoption of IS, SM, IC and their combinations reduces the number of months without enough food and increases farm income. When we consider the magnitude of the impacts, interesting results emerge when a combination of the CSA practices are considered. The highest impact is observed with the joint adoption of SM & IC and IS &IC. Broadly, the empirical findings suggest that integrated systems (in our case crop-poultry integration), deserve both policy and research attention as they provide synergistic benefits that improve climate resilience and household welfare.

The potential of conservation agriculture to improve nitrogen fixation in cowpea under the semi-arid conditions of Kenya

Low-cost but productive crop intensification options are needed to assist smallholder farmers in the tropics to move away from poverty. This study assessed the capacity of cowpea (Vigna unguiculata (L.) Walp.) to perform biological N fixation (BNF) under no-tillage practices, crop residue cover and intercropping with maize (Zea mays L.). The study was performed during the long rains of 2017 at Kiboko experimental station, located in semi-arid eastern Kenya. The research field trials had been running for three years (6 cropping seasons) by the time the sampling took place. The experimental set up was a split-plot design: main plots being tillage system (no till + maize stover retention (CA), and conventional tillage to 15 cm depth without mulch retention (CT)), sub-plot being cropping system (maize-cowpea intercrop, maize monocrop, and cowpea monocrop). Cowpea plants were sampled at 50% flowering stage and at physiological maturity to investigate biomass production and %N derived from the atmosphere (%Ndfa) through the 15N natural abundance technique, using maize as a reference control. Results showed that the number of nodules per plant was higher in CA treatments rather than in CT although not significant (p>0.05). Mean cowpea grain yield at harvest varied between 472 – 590 kg ha‐1 in intercrops whereas grain yield in monocrops was between 1465 - 1618 kg ha-1. Significant differences were however recorded between treatments with CT monocropped cowpea at flowering recording the highest mean %Ndfa (62%) and CT intercrop the lowest (52%). At harvest stage CA inter recorded the highest %Ndfa (54%) while CT intercrop the lowest (41%). The %Ndfa was higher (p<0.05) at flowering (between 57- 69%) compared with 45 - 64 % at harvest stage. Overall cowpeas in intercrops derived between 17.8 - 22.8 kg ha-1 of their total N from atmospheric dinitrogen fixation while monocrops between 54.9 - 55.2 kg ha-1. The effect of CA on BNF was positive but not significantly different from CT. These results suggest that CA has the potential to enhance the BNF process but there is a need to explore in future alternative spatial arrangement and variety choice in intercropping of cowpea and maize to optimize the BNF process.

ASSESSMENT OF SOIL MOISTURE AND NUTRIENTS ON TERRACE SLOPE OF HARD-SETTING SOILS IN SEMI-ARID EASTERN KEN

<p><strong>Background:</strong> Terraces are structures consisting of ditches and embankments used to control erosion and increase land productivity. There is, however, little emphasis on the effects of the ditch dimensions on soil moisture and nutrient dynamics. <strong>Objective:</strong> To determine the effect of varying ditch depths on soil moisture and nutrient quantities and their variability within the terrace slope on hard-setting soils. <strong>Methodology:</strong> Soil samples were collected seasonally in 2014 and 2015 from terraces with different ditch depths (60, 30, and 0 [control] cm) for the determination of soil moisture content (SMC). The samples were collected from the upper, middle and lower slope positions of each terrace. Soil from the three slope positions of each terrace was also sampled at the end of the study and analyzed for total nitrogen (%TN), available phosphorous (Av. P), exchangeable potassium (K<sup>+</sup>) and % organic carbon (OC) contents. Data were subjected to a two-way analysis of variance and differences in means determined at a 95% level of confidence. <strong>Results:</strong> Significant interactions (P<0.001) in SMC were observed between seasons, ditch depths and slope positions. Higher SMC was found in treatments with 30 and 60 cm ditch depths in all the slope positions and seasons compared to the control. Soil moisture contents in the lower and upper slope positions were significantly different between the terraces with 30 and 60 cm ditch depths when rainfall was high and evenly distributed, but non-significant in poorly distributed rainfall seasons. Significant differences (P ≤ 0.05) in contents of total nitrogen and available phosphorous were found between the upper and lower slope positions of the terraces with ditches. <strong>Implications: </strong>The effect of ditch depths on moisture, total nitrogen and available phosphorous contents and their variability within the slope depended on the amount and distribution of rainfall. <strong>Conclusion: </strong>Construction of terraces with shallow ditch depths (of 30 cm) is recommended to conserve soil moisture and nutrients nitrogen and phosphorous on hard-setting soils in the marginal areas of semi-arid Eastern Kenya. </p>

Characterization and diversity of native Azotobacter spp. isolated from semi-arid agroecosystems of Eastern Kenya.

Declining food production in African agroecosystems is attributable to changes in weather patterns, soil infertility and limited farming inputs. The exploitation of plant growth-promoting soil microbes could remedy these problems. Such microbes include Azotobacter; free-living, nitrogen-fixing bacteria, which confer stress tolerance, avail phytohormones and aid in soil bioremediation. Here, we aimed to isolate, characterize and determine the biodiversity of native Azotobacter isolates from soils in semi-arid Eastern Kenya. Isolation was conducted on nitrogen-free Ashby's agar and the morphological, biochemical and molecular attributes evaluated. The isolates were sequenced using DNA amplicons of 27F and 1492R primers of the 16S rRNA gene loci. The Basic Local Alignment Search Tool (BLASTn) analysis of their sequences revealed the presence of three main Azotobacter species viz., Azotobacter vinelandii, Azotobacter salinestris and Azotobacter tropicalis. Kitui County recorded the highest number of recovered Azotobacter isolates (45.4%) and lowest diversity index (0.8761). Tharaka Nithi County showed the lowest occurrence (26.36%) with a diversity index of (1.057). The diversity was influenced by the soil pH, texture and total organic content. This study reports for the first time a wide diversity of Azotobacter species from a semi-arid agroecosystem in Kenya with potential for utilization as low-cost, free-living nitrogen-fixing bioinoculant.

MORE CROP PER DROP: THE MAGIC OF SWEET POTATO (Ipomoea batatas L.)

<p><strong>Background:</strong> Water is the most valuable resource in agriculture. Agricultural development in semi-arid eastern Kenya is essentially dependent on intermittent rainfall. An accurate estimate of sweet potato water usage and productivity is considered a significant feature of conservation agriculture under such climatic conditions. <strong>Methodology:</strong> The research was conducted for two seasons, from December 2018 to April 2019 and October 2019 to March 2020, with the aim of quantifying the water use efficiencies of two sweet potato varieties, Kabode and Bungoma. Assuming that there were no variations in water-use efficiency between the two varieties. The experiment was established as RCBD for the two seasons. Treatments comprised of sole sweet potato varieties of Kabode and Bungoma, together with their intercrops with common beans. <strong>Results:</strong> Seasonal effective rainfall values were 302 and 639.2 mm, whereas the mean saturation pressure deficit recorded was 2.5 and 2.4 Kpa for S (I) and S (II), respectively. This presented S(I) with 815.1 mm ET<sub>crop</sub> demanding 622.1 mm irrigation water, whereas S(II) envisaged a 3.3% decrease in ET<sub>crop</sub> values; 788 mm and requiring 427.6 mm of supplemental irrigation water to attain optimal sweet potato yields. Similarly, the test crops paraded WUE values of 39.8 and 30.0 kg ha<sup>-1 </sup>mm<sup>-1 </sup>and water productivity indices based on rain water were 1.11 and 0.95 kg m<sup>−3</sup> for Kabode and Bungoma varieties, respectively. HI for S (I) were 40.8 and 35.4% whilst 54.2 and 46.8 % for Kabode and Bungoma varieties, respectively. <strong>Implications:</strong> WUE values of the sweet potato crop increased from warm-dry season S (I) to the warm-wet season S (II), as Kabode portrayed a higher adaptability. These results provide an acumen for decision making in the setting of climate change.<strong> Conclusions:</strong> Kabode variety differed significantly with Bungoma variety in their abilities to efficiently use water, thus portraying its adaptability in such a peculiar environment. The climatic environment: dew point temperatures and saturation pressure deficit had no significant impact on sweet potato water use efficiency.</p>

ECONOMICS OF PLANTING PITS UNDER SORGHUM AND PIGEON PEA IN SEMI-ARID AREAS OF EASTERN KENYA

Rainwater harvesting (RWH) is promoted in arid and semi-arid areas for increased yields. Planting pits are RWH systems that are used for collecting rainwater and runoff. Recently, there has been increased interest in economic and environmental benefits of agricultural technologies for sustainable development. To contribute to this knowledge, economics of Chololo and Five by Nine planting pits and sorghum and pigeon pea mulch was investigated at two sites in semi-arid Eastern Kenya for four seasons. The experiments were in a randomized complete block design in three replicates. Returns of planting pits and mulch were calculated by evaluating the benefit-cost (B: C) ratios and net present values (NPV) while considering water as an economic good. Planting pits were profitable for sorghum and unprofitable for pigeon pea production. The outcome differed with sites and seasons depending on rainfall availability. Chololo pits earned US$ 92 to US$ 786 per hectare whereas Five by Nine pits earned US $ 59 to US$ 955 per hectare. Mulches were beneficial for sorghum and pigeon pea production at Nkarini and unprofitable at Machang’a with the yield differing with seasons depending on rainfall availability. This study recommends Five by Nine and Chololo pits for sorghum production at Nkarini where it was economically viable in three out of four seasons.

Yield Stability and Farmer Preference of Cowpea (Vigna Uncuilata) Lines in semi-arid Eastern Kenya


 
 
 Stability in yields of agronomically acceptable cultivars is generally regarded as the ultimate goal in cowpea improvement. Nine advanced cowpea lines and 3 local checks were evaluated for grain yield in eastern Kenya with the aim of identifying stable genotypes and integrating farmer preferences. The study was conducted in 3 locations over 2 years under a randomized complete block design with 3 replications. Stability was estimated using additive main effects and multiplicative interaction (AMMI) and genotype by environment (GGE) models. There was variation among genotypes, locations and their interactions for grain yield. Genotype G5, G9 and G2 were found to be stable and high yielding. Environments Kit16 and Kit15 were considered as the most suitable for selecting superior genotypes for adaptability and stability. Farmers’ criteria for selecting genotypes included early maturing, pod length, disease tolerant and high yielding varieties. Cowpea performance for grain yield was greatly influenced by inherent genotypic factors, environment and their interaction effects.
 KEY WORDS: COWPEA, ENVIRONMENT, GENOTYPE BY ENVIRONMENT INTERACTION, STABILITY, GRAIN YIELD
 
 

Yield Stability and Farmer Preference of Cowpea (Vigna Unguiculata) Lines in Semi-Arid Eastern Kenya

Stability in yields of agronomically acceptable cultivars is generally regarded as the ultimate goal in cowpea improvement. Nine advanced cowpea lines and 3 local checks were evaluated for grain yield in eastern Kenya with the aim of identifying stable genotypes and integrating farmer preferences. The study was conducted in 3 locations over 2 years under a randomized complete block design with 3 replications. Stability was estimated using additive main effects and multiplicative interaction (AMMI) and genotype by environment (GGE) models. There was variation among genotypes, locations and their interactions for grain yield. Genotype G5, G9 and G2 were found to be stable and high yielding. Environments Kit16 and Kit15 were considered as the most suitable for selecting superior genotypes for adaptability and stability. Farmers’ criteria for selecting genotypes included early maturing, pod length, disease tolerant and high yielding varieties. Cowpea performance for grain yield was greatly influenced by inherent genotypic factors, environment and their interaction effects.

Effects of Nitrogen and Phosphorus Application Rates on Growth and Yield of Two Sorghum Cultivars in Semi-Arid Eastern Kenya Case Study of Machakos County

Effects of Nitrogen and Phosphorus Application Rates on Growth and Yield of Two Sorghum Cultivars in Semi-Arid Eastern Kenya Case Study of Machakos County

On developing a scale to measure chronic household seed insecurity in semi-arid Kenya and the implications for food security policy

Seed security is complementary and relational to food security; having access to seed that produces meaningful and resilient yields of culturally appropriate food is an integral aspect of food security for smallholder farmers. However, essential components of smallholder seed security continue to be underemphasized in food and seed policy. In this study, we analyze household and farm-level characteristics that may predict chronic seed insecurity in semi-arid eastern Kenya. In the process, we also present and test the Household Seed Insecurity Assessment Scale (HSIAS) designed to measure household chronic seed insecurity. Results suggest that mild chronic seed insecurity continues to be a problem in most households, hampering their ability to produce food. We found that older and more experienced farmers were more seed insecure and that farmer adoption of new varieties was associated with seed insecurity. Obtaining seed through local markets and informal giving was done evenly by all farmers while using agroshops was associated with greater seed insecurity in some instances. Key attributes of household seed (in)security identified in this study are used to inform seed and food policies that better support smallholder farmers in Kenya. With further development, the HSIAS has the potential to enhance local monitoring systems and government food and seed policy responses.

Exploring Niches for Short-Season Grain Legumes in Semi-Arid Eastern Kenya - Coping with the Impacts of Climate Variability.

Climate variability is the major risk to agricultural production in semi-arid agroecosystems and the key challenge to sustain farm livelihoods for the 500 million people who inhabit these areas worldwide. Short-season grain legumes have great potential to address this challenge and help to design more resilient and productive farming systems. However, grain legumes display a great diversity and differ widely in growth, development, and resource use efficiency. Three contrasting short season grain legumes common bean (Phaseolus vulgaris L.), cowpea (Vigna unguiculata (L.) Walp.] and lablab [Lablab purpureus (L.) Sweet] were selected to assess their agricultural potential with respect to climate variability and change along the Machakos-Makueni transect in semi-arid Eastern Kenya. This was undertaken using measured data [a water response trial conducted during 2012/13 and 2013/14 in Machakos, Kenya] and simulated data using the Agricultural Production System sIMulator (APSIM). The APSIM crop model was calibrated and validated to simulate growth and development of short-season grain legumes in semi-arid environments. Water use efficiency (WUE) was used as indicator to quantify the production potential. The major traits of adaptation include early flowering and pod and seed set before the onset of terminal drought. Early phenology together with adapted canopy architecture allowed more optimal water use and greater partitioning of dry matter into seed (higher harvest index). While common bean followed a comparatively conservative strategy of minimizing water loss through crop transpiration, the very short development time and compact growth habit limited grain yield to rarely exceed 1,000 kg ha−1. An advantage of this strategy was relatively stable yields independent of in-crop rainfall or season length across the Machakos-Makueni transect. The growth habit of cowpea in contrast minimized water loss through soil evaporation with rapid ground cover and dry matter production, reaching very high grain yields at high potential sites (3,000 kg ha−1) but being highly susceptible to in-season drought. Lablab seemed to be best adapted to dry environments. Its canopy architecture appeared to be best in compromising between the investment in biomass as a prerequisite to accumulate grain yield by minimizing water loss through soil evaporation and crop transpiration. This lead to grain yields of up to 2,000 kg ha−1 at high potential sites and >1,000 kg ha−1 at low potential sites. The variance of observed and simulated WUE was high and no clear dependency on total rainfall alone was observed for all three short-season grain legumes, highlighting that pattern of water use is also important in determining final WUEbiomass and WUEgrain. Mean WUEgrain was lowest for cowpea (1.5–3.5 kggrain ha−1 mm−1) and highest for lablab (5–7 kggrain ha−1 mm−1) reflecting the high susceptibility to drought of cowpea and the good adaptation to dry environments of lablab. Results highlight that, based on specific morphological, phonological, and physiological characteristics, the three short-season grain legumes follow different strategies to cope with climate variability. The climate-smart site-specific utilization of the three legumes offers promising options to design more resilient and productive farming systems in semi-arid Eastern Kenya.

Understanding growth and development of three short-season grain legumes for improved adaptation in semi-arid Eastern Kenya

Short-season grain legumes play an important role in smallholder farming systems as source of food and to improve soil fertility through nitrogen fixation. However, it is not clearly understood how these diverse legumes contribute to the resilience of such systems in semi-arid environments. We describe the growth, development and resource-use efficiency (focusing on radiation, RUE) of three promising short-season grain legumes: common bean (Phaseolus vulgaris L.), cowpea (Vigna unguiculata (L.) Walp.) and lablab (Lablab purpureus (L.) Sweet). Two field experiments were conducted during the short rains of 2012–13 and 2013–14 in Eastern Kenya. In the first experiment, the legumes were grown at three plant densities (low, medium, high); in the second experiment, they were subjected to three water regimes (rainfed, partly irrigated, fully irrigated). Phenological development was monitored and biomass accumulation, leaf area index and fractional radiation interception were measured repeatedly during growth; grain yield was measured at maturity. Harvest index and RUE were calculated from these data. Common bean had the shortest growing period (70 days), the most compact growth habit and relatively high RUE but limited grain yield (1000–1900 kg ha–1), thereby proving more suitable for cultivation in areas with restricted cropping windows or in intercropping systems. Cowpea had a longer growing period (90 days) and a spreading growth habit leading to high light interception and outstanding grain yields under optimal conditions (1400–3050 kg ha–1). Lablab showed stable RUE values (0.76–0.92 g MJ–1), was relatively unaffected by limited water availability and had a comparatively long growing period (100 days). Lablab grain yields of ~1200–2350 kg ha–1 were obtained across all water regimes, indicating a high potential to cushion climatic variability. Planting density strongly influenced the production success of cowpea and lablab, with high plant densities leading to vigorous growth habit with low podset establishment. Such information on temporal and spatial differences in growth, development and resource-use efficiency is highly valuable for crop-modelling applications and for designing more resilient farming systems with short-season grain legumes.

The quantity and quality of feed available to indigenous chickens under the scavenging system in semi-arid Eastern Kenya

ABSTRACTFree range indigenous chickens suffer from low productivity due to inadequate quantity and quality of feed, high predation and high mortality rates. The aim of the study was to establish the nutritional gaps in the free range chickens’ diets. A total of 40 farmers from two locations participated in the study. The study used 548 chickens aged 7–8 months purchased from farmers. The experimental chickens were slaughtered before weighing the carcass and crop content. The weight of the gastro-intestinal tract, heart and liver was also recorded. The crop contents were analysed after drying in the oven for 48 hours at 60 °C to determine what was consumed. The mean live weight of the experimental chickens was 1443 ± 296 g. The chickens mainly fed on maize, which accounted for over 80% of their diet. The estimated metabolizable energy (ME) of the crop contents for the study chickens was 2887.8 Kcal/kg. Although the chickens from Kionyweni had significantly (P<0.05) higher ME than those from Kilome, it was ...

Changing rainfall patterns and farmers’ adaptation through soil water management practices in semi-arid eastern Kenya

ABSTRACTThere is limited documentation of soil and water management technologies that enhance adaptation to climate change in drylands of Kenya. Rainfall patterns were analyzed in the semi-arid Machakos and Makueni counties of eastern Kenya using historical data. A total of forty-three smallholder farmers implementing soil water management practices were sampled, and an estimate of the seasonal water budget for current crop and livestock production systems computed. Analysis of rainfall amounts and distribution shows increasing variability, with the average annual total amounts decreasing over the past 50 years. Furthermore, the number of rainy days within the March-April-May season that can support crop growth is gradually decreasing. These decreases are however not significant at P < 0.05. There were more seasons with low rainfall amounts compared to those with high rainfall amounts. All these subject the smallholder crop and livestock production system to limited soil moisture. Farmers address the risk by harnessing and utilizing green (rainfall stored in soil) and blue (rainfall collected into storage tanks) water technologies. The study found that farmers in these semi-arid counties practice fifteen diverse soil and water management interventions on their farms. The most popular practices are cut-off drains, retention ditches, terracing, run-off harvesting, and agroforestry. The estimated seasonal water budget indicates the need for integrated soil and water management interventions to address the crop and livestock production constraints.

Assessment of climate variability and change in semi-arid eastern Kenya

A study was conducted to investigate the intra-seasonal climate variability and change in semi-arid eastern Kenya and also assessed the ability of the households to discern trends in climate and how the perceived trends converge with actual long term weather observations. The study utilised long term climatic data and data collected through interviews of 200 households using a structured questionnaire. The survey data was analysed through descriptive statistics using the Statistical Package for Social Sciences (SPSS) version 12.0. The results of long term climatic data indicated high year-to-year variation in seasonal rainfall with 49.0% and 58% negative anomalies observed in the long and short rainfall seasons respectively. No discernible increasing or decreasing trend in the long- seasonal rainfall was observed over the period of study. However, Long-term temperature data showed high year-to-year variation in annual mean maximum and minimum temperatures with maximum temperature increasing during the period. Long term rainfall data (51 years) showed that 31.4 and 35.3% of the long rains would be classified as good and failed seasons respectively, with the remaining percentage classified as moderate seasons. For the short rains, 15.7 and 43.1 % would be classified as good and failed seasons respectively, with the remaining percentage classified as moderate seasons. Farmers interviewed were able to recollect the past seasons fairly accurately especially the ‘good’ and ‘failed’ seasons which corroborated well with the meteorological records. Indigenous knowledge on weather forecasting was reported by 81% of farmers to be helpful in farming decision making especialy on the types of crops to be planted. A better understanding of farmers’ perceptions of climate change, ongoing adaptation measures, and the decision-making process would important to inform policies aimed at promoting sustainable adaptation of the agricultural sector.

Can Short-season Grain Legumes Contribute to More Resilient and Productive Farming Systems in Semi-arid Eastern Kenya?

Lately grain legumes have come out of the shadows in research and extension because of their highly valued and multiple benefits for the farmer and the farming systems across the developing world. For semi-arid regions in particular, inadequate and highly variable rainfall and short growing periods limit yield potential and create a risky primary production environment. However, short-season crop varieties offer a promising option for farming with increased uncertainties. Against this background, the aim of this work was to collect field trial data for multiple seasons in Eastern Kenya to better calibrate the existing APSIM (Agricultural Production System sIMulator) legume models for short-season varieties of common bean (Phaseolus vulgaris L.)., cowpea (Vigna unguiculata (L.) Walp.) and lablab (Lablab purpureus (L.) Sweet) and to evaluate the performance of the adapted models in terms of biomass production and yield. Finally with the use of a simulation study, the impact of management options (e.g. sowing time, planting density) and future climate predictions on the overall production potential of the different short-season grain legumes was explored. Results indicate that decisions on optimal sowing times will become more important with shortened growing periods to take full advantage of in-season rainfall. Short-season cultivars of beans were advantageous in extreme short growing periods with external droughts due to their very short maturity time. Lablab seemed to cope best with high in season rainfall variability producing stable yields across a range of rainfall scenarios independent of future climate predictions. Cowpea instead was out yielding beans and lablab in wet years and had a very high biomass production. Consequently, using the full diversity of available short-season legumes can function as an essential part of a sustainable risk management strategy to design more resilient farming systems and increase food security in semi-arid Eastern Kenya. Finally, if well calibrated and tested, simulations models have proved to be an excellent tool for ex-ante assessment of agricultural management interventions in the view of future climate change.

Short Term Leguminous Trees-Tillage Interactions and Their Effect on Soil-Water Content in a Semi-Arid Agroforestry Parkland

Agricultural activities that encourage slashing, burning and ploughing greatly affect the soil structure and soil organic matter on which soil water retention depends. In this study, we hypothesized that inclusion of rotational leguminous tree species improves soil water retention in a semi-arid conservation agriculture system. In a study done in Kibwezi, semi-arid eastern Kenya, results showed that the amount of water retained in the different soil strata from plots with different tree species and tillage practices was highly significant (P = 0.032). Plots with planting basins and Gliricidia sepium and Faidherbia albida tree species retained more water in both the upper and lower strata. Plots with G. sepium tree species under planting basins and zero tillage under F. albida had significantly higher soil organic carbon levels than plots that were managed under ridges and ploughing (P = 0.002). On the other hand, bulk density in plots with planting basins and zero tillage and ridges ranged between 1.35 g/cm3 and 1.53 g/cm3. Conventional tillage plots had bulk density values of 1.65 g/cm3 and 1.72 g/cm3 in the upper and lower strata respectively. The time-dependent nature of rotational leguminous tree species on soil organic matter and soil water retention in the semi-arid conservation agriculture system highlights the importance of considering these species for improving organic carbon and water retention for improved crop production.

The potential role of sorghum in enhancing food security in semi-arid eastern Kenya: A review

Successive droughts in Kenya compounded with other socio-economic constraints have led to persistently unstable and declining agricultural productivity in semi-arid eastern Kenya. This has given rise to the need to find coping strategies that would include growing alternative crops that are drought tolerant and thus suitable for the areas. Research in Kenya and elsewhere has shown that sorghum (Sorghum bicolor L. Moench) has the potential to end severe food insecurity in ASALs due to its tolerance to drought and ability to thrive under a wide range of soils. However, research and government policy in Kenya have shown a continual inclination to maize production in these areas though the crop is regarded a high risk option due to poor adaptation especially to the low rainfall. This paper reviews the potential of sorghum for improving food security in ASALs of Kenya with specific focus on semi-arid eastern Kenya. This will contribute to the ongoing debate to inform private and public sector policy and investments for increasing production of sorghum and other drought tolerant crops in the ASALs as a way of alleviating food insecurity and poverty.Key words: ASALs, drought, sorghum, food security, poverty

Yield and water use efficiencies of maize and cowpea as affected by tillage and cropping systems in semi-arid Eastern Kenya

Soil water conservation through tillage is widely accepted as one of the ways of improving crop yields in rainfed agriculture. Field experiments were conducted between 2007 and 2009 to evaluate the effects of conservation tillage on the yields and crop water use efficiency of maize (Zea mays L.) and cowpea (Vigna unguiculata L.) in eastern Kenya. Experimental treatments were a combination of three tillage practices and four cropping systems. Tillage practices were tied-ridges, subsoiling-ripping and ox-ploughing. The cropping systems were single crop maize, single crop cowpea, intercropped maize–cowpea and single crop maize with manure. The treatments were arranged in split plots with tillage practices as the main plots and cropping systems as the sub-plots in a Randomized Complete Block Design (RCBD). The results showed that tied-ridge tillage had the greatest plant available water content while subsoiling-ripping tillage had the least in all seasons. Averaged across seasons and cropping season, tillage did not have a significant effects on maize grain yield but it did have a significant effect on crop grain and dry matter water use efficiency (WUE). Nevertheless, maize grain yields and WUE values were generally greater under tied-ridge tillage than under subsoiling-ripping and ox-plough tillages. The yields and WUE of cowpea under subsoiling-ripping tillage were less than those of ox-plough tillage. When averaged across the seasons and tillage systems, the cropping system with the manure treatment increased (P≤0.05) maize grain yield, grain WUE and dry matter WUE by 36%, 30%, 26% respectively, compared to treatments without manure. Maize and cowpea when intercropped under ox-plough and ripping tillage systems did not have any yield advantage over the single crop.