Browsing by Author "Yegon, Rebecca"
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Item Determinants for rainwater harvesting adoption: a case study of smallholder farmers in Murang’a County, Kenya(UoEm, 2024-05-17) Itemo Irungu, Francis; Yegon, Rebecca; Milkah Muniale, FaithRainwater harvesting has been practiced among smallholder farmers for centuries in many parts of the world. Recently, it has gained more attention due to the reported increasing water demand and the need for sustainable water management. Drawing on data from a cross sectional survey of 384 household heads (HH), the research study explored the determinants for rainwater harvesting among smallholder farmers in Murang’a County, Kenya. Multistage random sampling technique was employed during the survey using KOBO collect software for data collection. The fndings revealed that socio-economic, socio-demographic and institutional factors signifcantly infuenced the adoption of rooftop RWH, mulching, terraces, infltration pits, retention ditches, water bunds, water pans, dams, furrows, negarims and deep ploughing among HH in Murang’a County. The multivariate probit model results showed that household head’s access to credit facilities, land ownership, age, level of income, education level, gender, family size, source of income, membership to farmers’ groups and access to training services positively infuenced rainwater harvesting (RWH) adoption. Similarly, HH membership to farmers group(s) had merits including: social ties, source of information and source of credit which were also key determinants to RWH adoption in the area. The fndings of the present study recommends the relevant stakeholders to carry out training to HH on RWHTs, creation of awareness among youths on merits for RWH adoption, encourage HH to join farmers’ groups and encourage partnership with credit facilities in RWHTs adoption among HH in the region. Results of the present study provide valuable insights into the determinants for rainwater harvesting among smallholder farmers in Murang’a County which can be used to inform policy and practice for widespread adoption.Item Economics of Planting Pits under Sorghum and Pigeon Pea in Semi-Arid Areas of Eastern Kenya.(2020-01) Yegon, Rebecca; Isaboke, Hezron N.; Mrema, Geoffrey Christoper; Mtakwa, PeterRainwater 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.Item Effect of decomposition intensity of incorporated chickpea manure on stability and saturated hydraulic conductivity of a clay loam and clay soil(Academic Journals, 2011-03-04) Wakindiki, I.C; Yegon, RebeccaThe role of organic matter (OM) in soil aggregation and saturated hydraulic conductivity (Ksat) has long been recognised but their depedence on the intensity of decay is less studied. The objective of this study was to determine the effect of decomposition intensity of incorporated chickpea manure on soil aggregate stability and Ksat. Samples of a clay loam and clay soil were collected from the top 15 cm layer and amended with chickpea green or mature dry manure and incubated at 30°C and ~60% water holding capacity. Decomposition intensity was determined by measuring CO2 evolution using NaOH traps, aggregate stability by wet sieving and Ksat by the constant head method. All determinations were made 3, 7 and 30 days after incubation and the data analysed following the general linear model for a 2 × 3 × 3 factorial in randomised complete block design. Evolution of CO2 in both soils and manure was highest on day 7 compared to day 3 and 30. In both soils >60% of the soil aggregates were macroaggregates >0.5 mm but the relative proportion of microaggregates <0.5 mm increased from ~10 to ~20% in the control and to ~15% in the amended cay loam soil in the day 30 treatments. Decomposition intensity was increased by incorporating chickpea manure which resulted in improved soil aggregate stability and Ksat especially in soil with low clay content. CO2 which is a simple product of decomposition may be used as a rapid indicator of soil aggregate stability and water movement in agricultural soils.Item A Guide for Soil Health and Fertility for Maize production in Kenya(UoEm, 2023) Nyaga, Patrick; Yegon, Rebecca; Laub, Moritz; Six, JohanThe health of your soil is a fundamental aspect of successful farming. However, many arable soils in Kenya have degraded and lost fertility over recent decades1. This is expected because many soils were recently transformed from more permanent land uses, which always leads to soil fertility losses2. However, this soil fertility loss is largely avoidable with best management practices that replenish soil organic matter and soil nutrient resources3,4.Item Inoculated Soybean Yields Response to Nitrogen and Phosphorus Application(SCIENCEDOMAIN international, 2016) Phiri, Austin T.; Muindi, Esther M.; Omollo, Jacob Omondi; Yegon, Rebecca; Kausiwa, DanielInherent low soil nitrogen (N) and phosphorus (P) is one of the major hindrances of increased soybean productivity in Malawian soils. Although, inoculation of legumes with rhizobia, has been advocated for decades as a way of boosting leguminous crops’ productivity through biological nitrogen fixation (BNF), the effectiveness of this strategy, has been low. An experiment was carried out to investigate the effect of the application of small doses of N and P to inoculated soybean. It was laid out in a complete block design (CBD) replicated three times and the treatments included: 1. Soybean only, 2. Inoculated soybean, 3. Inoculated soybean + 30 kg N ha-1, 4. Inoculated soybean + 30 kg N ha-1 + 25 kg P ha-1, 5. Inoculated soybean + 30 kg N ha-1 + 35 kg P ha-1. The soybean in all treatment plots except for treatment 1 was inoculated with 30 kg N ha-1 applied as urea to treatment plots 3, 4 and 5. Phosphorus as TSP was applied to treatment 4 and 5 at the rate of 25 and 35 kg P ha-1. Data collected included; selected soil physical and chemical properties,biomass and pod yields. Data obtained were subjected to Analysis of Variance (ANOVA) using the GenStat statistical package and treatment effects tested for significance using the F-test at 5% level of significance. Means were separated using the least significant difference (P<0.05). Results indicate that inoculating soybean with rhizobia and inoculating soybean with rhizobia plus applying 30 kg N ha-1 did not significantly increase biomass yields. However, inoculating soybean plus the combined application of 30 kg N ha-1 and, 25 kg P ha-1 or / and 35 kg P ha-1 increased the soybean biomass yields by 54% and 70% respectively above control. The lack of significant response when N was applied without P points to the significant role played by phosphorus in root development and energy transfer processes within the plant. Effective nodulation, however, was significantly higher (p<0.05) above the control where inoculation was combined with the application of 30 kg N ha-1 and 35 kg P ha-1, hence underlining the role played by phosphorus in nodule development and the role of starter N in soils low in N.Item Modeling integrated soil fertility management for maize production in Kenya using a Bayesian calibration of the DayCent model.(UoEm, 2024-07-04) Laub, Moritz; Wanjiku Mucheru-Muna, Monicah; Necpalova, Magdalena; Broek, Marijn Van de; Corbeels, Marc; Mathu Ndungu, Samuel; Mugendi, Daniel; Yegon, Rebecca; Waswa, Wycliffe; Vanlauwe, Bernard; Six, JohanSustainable intensification schemes such as integrated soil fertility management (ISFM) are a proposed strategy to close yield gaps, increase soil fertility, and achieve food security in sub-Saharan Africa. Biogeochemical models such as DayCent can assess their potential at larger scales, but these models need to be calibrated to new environments and rigorously tested for accuracy. Here, we present a Bayesian calibration of DayCent, using data from four long-term field experiments in Kenya in a leave-one-site-out cross-validation approach. The experimental treatments consisted of the addition of low- to high-quality organic resources, with and without mineral nitrogen fertilizer. We assessed the potential of DayCent to accurately simulate the key elements of sustainable intensification, including (1) yield, (2) the changes in soil organic carbon (SOC), and (3) the greenhouse gas (GHG) balance of CO2 and N2O combined. Compared to the initial parameters, the cross-validation showed improved DayCent simulations of maize grain yield (with the Nash–Sutcliffe model efficiency (EF) increasing from 0.36 to 0.50) and of SOC stock changes (with EF increasing from 0.36 to 0.55). The simulations of maize yield and those of SOC stock changes also improved by site (with site-specific EF ranging between 0.15 and 0.38 for maize yield and between −0.9 and 0.58 for SOC stock changes). The four cross-validation-derived posterior parameter distributions (leaving out one site each) were similar in all but one parameter. Together with the model performance for the different sites in cross-validation, this indicated the robustness of the DayCent model parameterization and its reliability for the conditions in Kenya. While DayCent poorly reproduced daily N2O emissions (with EF ranging between −0.44 and −0.03 by site), cumulative seasonal N2O emissions were simulated more accurately (EF ranging between 0.06 and 0.69 by site). The simulated yield-scaled GHG balance was highest in control treatments without N addition (between 0.8 and 1.8 kg CO2 equivalent per kg grain yield across sites) and was about 30 % to 40 % lower in the treatment that combined the application of mineral N and of manure at a rate of 1.2 t C ha−1 yr−1. In conclusion, our results indicate that DayCent is well suited for estimating the impact of ISFM on maize yield and SOC changes. They also indicate that the trade-off between maize yield and GHG balance is stronger in low-fertility sites and that preventing SOC losses, while difficult to achieve through the addition of external organic resources, is a priority for the sustainable intensification of maize production in Kenya.Item Performance of vermicomposted wastes for tomato (Lycopersicon Esculentum Mill.), production: A case study of Embu, Kenya(2021-10) Mochache, Miriam Ogake; Yegon, Rebecca; Ngetich, OnesmusPurposeTo investigate the effect of vermicomposted kitchen, market and tea wastes on tomato growth and yield and assess the benefits and costs that arise. Method A field experiment arranged in the randomized complete block design with five experimental treatments: vermicomposted kitchen, market, tea wastes, NPK fertilizer and a control, replicated thrice was conducted. Data were collected on plant height, number of leaves, number of branches, number of flower stalks, fruit number, fruit weight, above-ground biomass, marketable tomato yield, soil nutrient content, pH, texture and exchangeable acidity. Data obtained were analyzed using SAS version 9.4 by subjecting to one-way Analysis of Variance (ANOVA). Biophysical crop data means were separated using Tukey’s Studentized Range (HSD) test at p=0.05 significance level. T-test was used to determine the difference in soil nutrient content (Nitrogen (N), Phosphorus (P), Potassium (K), and Carbon (C)) at the beginning and end of the study. The benefits and costs were analyzed using the benefit-cost ratio formula. ResultsThe three vermicomposts had a similar effect (p>0.05) in influencing most of the tomato crop variables such as plant height, leaves number, branch number and flower stalks number. Tea waste vermicompost and kitchen waste vermicompost gave significantly high tomato yields of 115 t ha -1 and 113 t ha -1 at p=0.0001 as well as the highest benefit-cost ratio of 1.4:1. Conclusion Tea, market and kitchen wastes have a potential for use in the production of high-quality vermicompost that can be used as a soil amendment to enhance tomato performance.Item Planting Pits’ Effects on Soil Nutrients in a Sorghum and Pigeon Pea Rotation in Semi-arid Areas of Eastern Kenya(Science Domain International, 2016-12) Yegon, Rebecca; Mtakwa, Peter W.; Mrema, Geoffrey C.; Ngetich, Felix K.Planting pits are rain water harvesting structures that trap water and nutrients in surface runoff and rain water falling directly into the pits. Planting pits have been promoted for improving crop yields without considering the nutrient dynamics. To contribute to this knowledge, a study was conducted to determine the soil nutrient content after four seasons of growing sorghum and pigeon pea in rotation in “Chololo” and “Five by Nine” pits. Two planting pits; “Five by Nine” and “Chololo” with a control without water harvesting replicated three times were arranged in a randomised complete block design. The study was done for four seasons in Embu and Tharaka-Nithi counties in semiarid Eastern Kenya. Soil pH, total organic carbon, total nitrogen, available phosphorus, exchangeable potassium, calcium, magnesium and sodium were determined. “Chololo” pits significantly increased total organic carbon by 0.06 mg kg-1 and total nitrogen by 0.4 mg kg-1 relative to without water harvesting in Machang’a. The potassium content significantly increased by 0.4 cmolc kg-1 and 0.54 cmolc kg-1 in “Five by Nine” and “Chololo” pits in Machang’a relative to without water harvesting. There was an insignificant effect on soil phosphorus, calcium, magnesium and sodium. After four seasons of planting pits, total nitrogen, potassium and calcium increased in both soils and phosphorus in Machang’a relative to the beginning of the study. Total organic carbon significantly decreased in “Chololo” pits and without water harvesting in Machang’a. Phosphorus significantly decreased in Nkarini whereas magnesium and pH decreased in both soils. Nutrients in “Five by Nine” and “Chololo” pits depended on the soils and crops grown and should thus be promoted together with periodic soil testing.Item Shifting focus from external to in situ organic resources The redesign of four tropical long-term experiments(UoEM, 2024-07) Laub, Moritz; Corbeels, Marc; Ndungu, Samuel Mathu; Mucher-uMuna, Monicah Wanjiku; Mugendi, Daniel; Yegon, Rebecca; Waswa, Wycliffe; Vanlauwe, Bernard; Six, JohanLong-term experiments (LTEs) are critical for evaluating strategies that can maintain or increase crop yields, soil fertility and soil organic carbon (SOC), and help adapt to climate change. Yet, scientific knowledge is advancing and research questions are evolving. Therefore, it is important to review the objectives of LTEs over time. A change in their design may be necessary to keep the experimental treatments scientifically interesting, innovative, and relevant in the context of evolving agricultural challenges. Here, we describe the process of redesigning four LTEs in Kenya. These LTEs are unique in that they represent four different pedoclimatic conditions but with identical experimental treatments across sites. Initially, they focused on investigating how to maintain or increase SOC and maize yields over time by applying a combination of mineral nitrogen (N) and external organic resources. Specifically, the experimental treatments consisted of maize monoculture with different rates (1.2 and 4 t C ha−1 yr−1) and qualities of organic resources, either with or without mineral N fertilizer input. After about 20 years, it became clear that SOC was lost in most treatments. Therefore, continuing with the current experimental design was not an option. Taking advantage of the fact that the different former treatments led to different levels of soil degradation, we redesigned the LTEs to study the effectiveness of regenerative cropping strategies in rebuilding SOC and increasing crop yields starting from the different levels of soil degradation. The focus shifted from external to in situ organic inputs by increasing the root biomass of the cultivated crops. The newly established cropping system treatments are maize-legume rotation, maize-legume intercropping (double row configuration) and relay intercropping of maize with forage grass. A key finding from the previous phase of the experiments, namely, that external organic inputs with low C:N ratios are most efficient in building SOC, has been incorporated into the redesign. The relative contribution of external versus in situ organic resources is tested by splitting the cropping system treatments into those receiving either farmyard manure or green manure in the form of Tithonia diversifolia prunings and those receiving no external inputs. Split-plot treatments with and without mineral N were retained. The overall objective of studying mechanisms of tropical soil fertility maintenance and, more specifically, SOC formation, remained unchanged. However, the redesign aligned the LTEs with the current state of knowledge and pressing research questions, specifically focusing on the relative effectiveness of in-situ versus external organic inputs in SOC formation.Item Staff Profile - Dr. Rebecca Yegon(University of Embu, 2015-07) Yegon, RebeccaMs. Yegon holds a PhD from Sokoine University of Agriculture, Tanzania. Studied the effect of water harvesting on sorghum and Pigeon pea yields, soil water and soil Carbon and Nitrogen in Mbeere and Tharaka Kenya. She holds a Msc. Soil Science degree and a Bsc. Agriculture degree both of Egerton University, Njoro. Ms. Yegon teaches soil science and sustainable Agriculture courses in the department of Land and Water Management