Articles: Department of Water and Agricultural Resources Management

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Depth effects of long-term organic residue application on soil organic carbon stocks in central Kenya
(UoEm, 2025-06-17) Müller, Claude Raoul; Six, Johan; i Njiru, Daniel Mugend; Vanlauwe, Bernard; Broek, Marijn Van de;
In arable soils, a substantial portion of soil organic carbon (SOC) is stored below the plough layer. To develop sustainable soil management strategies, it is important to assess how they affect the quantity of SOC stored in the subsoil. Therefore, we investigated the impact of organic and inorganic nutrient inputs on SOC stocks down to 70 cm depth in a long-term field trial in Embu, Kenya. There were three organic input treatments (manure, Tithonia diversifolia residues, and maize stover) and a control treatment, each with and without the application of mineral nitrogen. These different treatments were applied to a maize monoculture over 38 growing seasons (19 years). Our results show that manure application had the largest positive impact on SOC stocks compared to the control; this effect was observed down to 60 cm depth. In contrast, Tithonia diversifolia and maize stover application led to significantly larger SOC stocks compared to the control, although this was only within the top 20 cm and 40 cm, respectively. Among the three organic residue treatments, only the application of manure had a significant effect on the SOC stock of the subsoil (i.e. the 30–70 cm depth layer). However, when considering the whole measured profile (i.e. 0–70 cm), all treatments led to significantly higher SOC stocks compared to the 91 ± 12 t C ha−1 of the control: manure had the highest stocks (120 ± 24 t C ha−1), followed by maize stover (112 ± 17 t C ha−1) and Tithonia diversifolia (105 ± 11 t C ha−1). Mineral nitrogen application did not have a significant impact on SOC stocks down to 70 cm depth. Our findings demonstrate that SOC in the subsoil comprised 48.5 % ± 1.7 % of the total SOC stocks across the 0–70 cm soil profile; however, only manure application affected subsoil OC levels, whereas other organic amendments solely increased SOC in the surface layer. Our results imply that gathering knowledge on the soil below the typically studied 0–30 cm depth layer will improve the overall assessment of agroecosystem properties, which is necessary to optimize soil system resilience, limit organic matter losses, and improve crop productivity.
Physicochemical and Heavy Metal Characterization of River Kapingazi in Embu County, Kenya
(UoEm, 2025-07-04) Yego, Naomy Chepkirui; Nyambane, Charles Onyari; Yegon, Rebbecca; Kiprotich, Shadrack
Surface water provides crucial support to the aquatic ecosystem and humans in numerous ways. However, its quality is paramount in determining its impact on the health of the aquatic ecosystem and humans. Currently, the malady of pollution arising from anthropogenic activities poses a significant threat to the quality of most rivers. The quality of water in the Kapingazi river in Embu County has received limited attention which is a concern that needs to be addressed. This study therefore, sought to investigate the status of water quality in river Kapingazi. The study analyzed 96 samples from four locations in a span of eight months which combined the dry and wet seasons of the year. Parameters measured in-situ included turbidity, pH, total dissolved solids (TDS), temperature, dissolved oxygen (DO) and electrical conductivity (EC) while ex-situ parameters were phosphates, nitrates and concentrations of heavy metals: iron and manganese. Results showed that Water Quality Index (WQI) during the drought period was74.05, suggesting that the water quality is only recommended for agricultural and industrial applications. During wet season, the water quality index was 89.67, reflecting a poor status, as more contaminants were likely introduced through surface runoff. Overall, the WQI averaged to 88.02. This study concludes that water in River Kapingazi is not suitable for human consumption; therefore, appropriate treatment is essential prior to its use. Similarly, the findings indicate that both rainy and drought periods significantly affect water quality, presenting challenges for its use for various purposes. It is recommended that the allocation of resources towards water treatment facilities and regulation of pollution sources should be enforced to ensure the safety of river water for diverse applications
Diversity analysis and genome‑wide association studies of seed weight trait in Bambara groundnut (Vigna subterranea (L.) Verdc.) using diversity array technology sequence derived single nucleotide polymorphism markers
(UoEm, 2025-02-22) Muturi, Phyllis; Kyallo, Martina; Gasura, Edmore; Yao, Nasser
Bambara groundnut is an indigenous drought tolerant legume cultivated in Africa. In Kenya, the crop is grown by women and the diver- sity of the accessions grown is unknown. Lack of information on the crop’s diversity and population structure make genetic improvement of the crop dif- fcult. The objectives of this study were to: (i) deter- mine the genetic diversity and population structure of 86 Bambara groundnut accessions from Kenya using 4,399 SNP markers and, (ii) identify SNPs associated with the seed weight of the Bambara groundnut col- lection. The DArT complexity reduction approach in combination with Illumina short-read sequencing (HiSeq 2000) was applied. Population structure anal- ysis suggested three genetic clusters. Accessions from the same county grouped into diferent clusters with exception of accessions from Kilif that distinctly fell into the same cluster. Analysis of molecular vari- ance indicated that 0.16% of the variance was due to genetic diferentiation among the populations, 19% of the variance was as a result of diferentiation among individuals within populations, and 81% variation was within individuals in a population. The study suggested signifcant DArTseq derived SNP mark- ers (p<0.05) distributed across Bambara groundnut contigs 1, 2, 3, and 5 associated with hundred seed weight, though the identifed SNPs were not vali- dated. This study provided an important foundation by ofering valuable insights into the genetic diversity of Bambara groundnut in traditional cultivation areas in Kenya. These fndings can serve as a starting point for further validation and application in Bambara groundnut breeding programs.
Introgressing Photoperiod/Thermo-sensitive Genic Male Sterile Gene into Basmati 370 Rice
(UoEm, 2025-01-08) Nyankemba, Beatrice Nyarangi; Arunga, Edith Esther; Nthakanio, Paul Njiruh
The emasculation of male gametes in pollen-recipient parents among self-pollinated crops (rice) is key to producing quality hybrid rice seeds. One of the emasculation tools in rice breeding is the photoperiodthermo sensitive genic male sterility (P/TGMS) method, which ultimately requires long daylight length and high-temperature growth conditions to induce male gametes sterility. Using the P/TGMS method to produce hybrid Basmati rice seeds has been slow because no commercial line has been developed. Crossing the Basmati rice line with a non-aromatic rice line produces F1 with non-basmati quality traits. This study aimed to introgress the p/tgms12-1 gene into Basmati 370 by treating P/TGMS lines (IR7327-2376-157S and IR-75589-31-27833S) with daytime temperatures (>33ºC) under a polythene greenhouse to emasculate pollen and cross-pollinating them with Basmati 370. Marker-assisted backcrossing was used to develop the BC1F2 Basmati breeding lines evaluated for pollen sterility and agro-morphological traits. Pollen sterility was tested by staining with 1% iodine potassium-iodide solution (I2KI), in which fertile and sterile pollen grains were stained with blue-black and yellow-pink dyes, respectively. The acquisition of near-complete pollen sterility among female parents is a manifestation of the greenhouse temperatures effectively emasculating pollen in P/TGMS parents and BC1F2. Analysis of variance on agro-morphological data showed significantly better agro-morphological traits in BC1F2 than the parents and significantly higher pollen sterility in P/TGMS lines than Basmati 370 (P≤0.05). The presence of the fgr gene in BC1F2 lines was confirmed using SSR markers, and the hybrids had both homozygous aromatic and heterozygous non-aromatic traits, the successful development of BC1F2 with p/tgms12-1 and fgr genes. The results obtained from this study are a major milestone towards improving Basmati rice yields in Kenya using hybrid seeds
Exploring Socio-Economic Characteristics on Adoption Intensity of Biochar Among Farming Households in Sub-Humid Regions of Western Kenya
(UoEm, 2025-01-08) Kyalo, Annastacia Maitha; Mogaka, Hezron; Kirimi, Florence Kaumi; Kizito, Kwena; Ndirangu, Samuel Njiri; Onyari, Charles Nyambane; Muriithi, Lydia; Elvin, Otara Nyaboe; Mutungi, Scholastica Katava; Kiprotich, Shadrack; Njiru, Moses Muchangi; Kamau, Ezekiel Areri;
Agriculture is a cornerstone of Kenya's economy, yet declining soil fertility and low adoption of sustainable agricultural technologies, such as biochar, have hindered productivity among smallholder farmers. Biochar is perceived to be a costeffective technology especially among resource constraint farming households. Despite many smallholder farmers acknowledging the importance of biochar as a soil amendment, most farmers face socio-economic barriers that hinder its adoption at scale. This study focused on how socio-economic factors influence adoption intensity of biochar, with a focus on the farming households in the sub-humid regions of Western Kenya. Employing a multistage stratified sampling procedure and Heckman selection model, the study reveals that awareness of biochar, access to credits, total land used in farming and education level positively and significantly influences adoption of biochar while total land owned in acres negatively and significantly influences adoption of biochar. Similarly, awareness of biochar, access to credits, and education level positively and significantly influences adoption intensity of biochar while terms of land ownership negatively and significantly influence adoption intensity of biochar. The study identifies awareness of biochar, education, credit access, and land ownership as key factors influencing its adoption by smallholder farmers. Promoting biochar as a soil amendment and carbon sequestration technique for farmers should be the main goal of the government, non-governmental organizations, and development organizations. Promoting the advantages of biochar for crop yields and soil fertility should be spearheaded by the Ministry of Agriculture's Extension Department. While development organizations offer financial assistance and training to promote adoption, policymakers should push farmer cooperatives to reduce the cost of biochar production and implementation
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, Johan
Sustainable 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.
QTL mapping for pod quality and yield traits in snap bean (Phaseolus vulgaris L.)
(UoEm, 2024-08-12) Njau, Serah Nyawira; Gepts, Paul; Parker, Travis A.; Duitama, Jorge; Arunga, Edith Esther
Pod quality and yield traits in snap bean (Phaseolus vulgaris L.) inﬂuence consumer preferences, crop adoption by farmers, and the ability of the product to be commercially competitive locally and globally. The objective of the study was to identify the quantitative trait loci (QTL) for pod quality and yield traits in a snap × dry bean recombinant inbred line (RIL) population. A total of 184 F6 RILs derived from a cross between Vanilla (snap bean) and MCM5001 (dry bean) were grown in three ﬁeld sites in Kenya and one greenhouse environment in Davis, CA, USA. They were genotyped at 5,951 single nucleotide polymorphisms (SNPs), and composite interval mapping was conducted to identify QTL for 16 pod quality and yield traits, including pod wall ﬁber, pod string, pod size, and harvest metrics. A combined total of 44 QTL were identiﬁed in ﬁeld and greenhouse trials. The QTL for pod quality were identiﬁed on chromosomes Pv01, Pv02, Pv03, Pv04, Pv06, and Pv07, and for pod yield were identiﬁed on Pv08. Co-localization of QTL was observed for pod quality and yield traits. Some identiﬁed QTL overlapped with previously mapped QTL for pod quality and yield traits, with several others identiﬁed as novel. The identiﬁed QTL can be used in future marker-assisted selection in snap bean.
A Diallel Cross-Based Analysis of the Genetic Basis of Pod Quality and Pod Yield in Snap Bean
(UoEm, 2024-07-27) Njau, Serah N.; Arunga, Esther; Otsyula, R
Snap bean (Phaseolus vulgaris L.) is among the leading vegetables in Kenya that is mainly grown for export with the potential to increase household income. There are few programs in Kenya that focus on breeding new cultivars for increased production. The development of snap bean varieties that are resilient to the changing climate is crucial for sustainable agriculture in Kenya. To achieve this, knowledge of gene action, trait expression, and heritability is vital in effective breeding for quantitative traits like pod quality and yield. A study was conducted to investigate the inheritance of pod quality and yield traits in snap beans, which can inform the breeding of snap beans. A half diallel cross involving two indeterminate dry beans (G2333 and MCM 5001) and five determinate snap beans (Amy, Moonstone, Seagull, Serengeti and Vanilla) varieties was conducted. Data on pod traits (pod weight per plant, pod number per plant, pod length, pod diameter, pod wall fiber and pod suture string) were collected from 21 F1s and 7 parents grown in two locations (Embu and Kirinyaga Counties) in Kenya. The results showed significant genotypic and environmental effects (P < 0.001) for all traits, with significant genotype by environment (G × E) interactions for most traits. Additionally, general combining abilities (GCA) and specific combining abilities (SCA) were significant for all traits evaluated. The significance of GCA and SCA indicated the importance of both additive and non-additive gene effects in controlling the traits, although the additive gene effects were predominant. The study revealed that Vanilla and Serengeti had the highest GCA estimate for pod quality traits, while G2333 and MCM5001 had the highest GCA estimate for pod yield traits. Snap bean pod yield and quality are quantitative traits controlled by multiple genes and influenced by the environment. Therefore, the predominance of additive gene effects suggests that selection for these traits in segregating generations could yield satisfactory gains. The results of this study could impact the development of snap bean varieties that are more resilient to the effects of climate change. Thus, improving the sustainability and productivity of the agriculture sector in Kenya.
Inoculum sources and management of bean scab caused by Elsinoë phaseoli
(UoEm, 2024-06-24) Masheti, Yona; Muthomi, James W.; Muiru, William M; Arunga, Esther E.; Gepts, Paul
Bean scab caused by Elsinoë phaseoli is a major challenge to common bean cultivationin Kenya. However, knowledge about its epidemiology and management is limited.This study conducted three experiments in Kakamega, Kenya, evaluating scab inocu-lum sources and control options. The first experiment evaluated three different inoc-ulum sources over two seasons; bean crop residue caused the highest scab incidencein both the 2021 (62.1%) and 2022 (81.1%) seasons. The second experiment assessedthe effect of rotation history on scab over three seasons. Scab incidence consist-ently surpassed 90% within the first 30 days after planting in half-yearly rotated fieldsacross all seasons, while the disease was absent after planting in fields with no recenthistory of legumes. Fields rotated out of legumes consistently had the highest grainyield, averaging 1.5 t ha−1 over the seasons. Additionally, the rotation land treatmentdisplayed significantly more pods per plant during the 2021 (9.7), 2022a (9.8), and2022b (12.5) seasons. In the third experiment, the impact of five fungicides and fourcropping systems on bean scab was investigated over two seasons. Neither fungicidetreatments nor cropping systems had an effect on bean scab incidence even whenonly severe symptoms were considered. Carbendazim had the highest yield (1.9 t ha−1)outperforming the unsprayed control only in the 2022 season while none of the otherfungicides outperformed the control treatment in yield parameters in either season.This study emphasizes the challenge of managing bean scab without proper crop rota-tion and underscores the role of crop residue as a critical inoculum source.
Efficacy of Metarhizium anisopliae against the Greater Pumpkin Fly Dacus bivitattus
(UoEm, 2023-07-01) Dubois, Thomas; Onsongo, Susan K.; Omuse, Evanson R.; Odhiambo, Joseph A.; Akutse, Komivi S.; Mohamed, Samira A.
The greater pumpkin fly Dacus bivittatus (Bigot) is a fruit fly indigenous to Africa, which causes extensive damage to Cucurbitaceae. To control this pest, farmers rely on synthetic chemicals, often organophosphates, which have negative effects on human health and the environment. However, the sustainable management of D. bivittatus may be obtained through integrated pest management (IPM) practices, with the use of biopesticides as a key component. In this study, the effect of nine isolates of the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) Sorokin (ICIPE 18, ICIPE 20, ICIPE 30, ICIPE 48, ICIPE 62, ICIPE 69, ICIPE 84, ICIPE 91 and ICIPE 94) was directly evaluated on adult D. bivittatus mortality. Adult flies were allowed to walk for 5 min on 0.3 g of dry conidia of each isolate and monitored daily for 10 days. We also evaluated the effect of sand inoculated with M. anisopliae on larval and pupal mortality and adult eclosion and mortality in three replicated experiments. Larvae were exposed to the same isolates at a concentration of 1 × 107 conidia/mL in sterile sand, and adult eclosion and mortality were monitored for 15 days. The median lethal time (LT50) of adults after direct exposure was shortest for ICIPE 18, ICIPE 20, ICIPE 30 and ICIPE 69 (3.11–3.52 days). In infested sand, larval mortality was highest for ICIPE 18 and ICIPE 20 (≥42.50%), while pupal mortality was highest for ICIPE 30 (≥41.25%). The lowest eclosion was observed for ICIPE 18, ICIPE 20, ICIPE 30 and ICIPE 69 (≤40.00%). The LT50 of adults eclosed from infested sand was shortest for ICIPE 18, ICIPE 20 and ICIPE 30 (4.48–6.95 days). ICIPE 18, ICIPE 20, ICIPE 30 and ICIPE 69 are, therefore, potential isolates for subsequent field testing on D. bivittatus populations.
A Guide for Soil Health and Fertility for Maize production in Kenya
(UoEm, 2023) Nyaga, Patrick; Yegon, Rebecca; Laub, Moritz; Six, Johan
The 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.
Identification of Elsinoë phaseoli causing bean scab in Kenya and evaluation of sporulation using five adapted techniques
(UoEm, 2024-06-07) Masheti, Y. O.; Muthom, J. W.; Muiru, W. M.; Arunga, E. E.; Gepts, P.
This research addresses the presence of Elsinoë phaseoli in Kenya, where information on the biology of this pathogen remains scarce. Employing a multifaceted approach, the study demonstrates the steps taken to isolate, identify, and characterize E. phaseoli as the pathogen responsible for scab on common bean. Field observations confirmed scab symptoms, particularly the prominent pod lesions. Elsinoë phaseoli was isolated from common bean using a targeted streaking method on older acervulus-bearing lesions. Morphological examinations revealed a notable diversity within E. phaseoli colonies, consistent with the characteristics of the genus. Molecular identification through ITS-rDNA sequencing confirmed isolate AscoSK1 obtained in this study as belonging to E. phaseoli, offering a robust species differentiation method. Assessing conidium production required the implementation of five different culture methods. An adaptation of the Scheper et al. (2013) method yielded the highest quantity of conidia from 25 colonies spaced at 1 cm apart, with a conidial yield of 5.0 × 106 conidia per 9-cm-diameter Petri dish. A higher conidial yield was attained after the colonies were pre-incubated on potato dextrose agar in the dark at room temperature for 28 days, followed by a transfer to corn meal agar for an additional 2 days at 20°C. This emphasizes the pivotal influence of incubation duration and pre-culture conditions on the process. This research provides insights into the biology of E. phaseoli and introduces an improved method for enhancing in vitro sporulation of the pathogen, setting groundwork for future research and handling.
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, Faith
Rainwater 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.
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, Johan
Long-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.
Garden Project Bears Fruit in School Display
(UoEm, 2023-11-11) Special to the Commercial; Yegon, Dr. Rebecca; Harris, Professor Karleah
Pine Bluff Junior High School recently displayed its garden during a visit by Karleah Harris, assistant professor for the Department of Human Sciences at the University of Arkansas at Pine Bluff, along with UAPB alumni and guests from West Memphis and Kenya. The purpose of this visit was to see the school's garden, a key component of the UAPB Project coordinated by the UAPB Department of Human Sciences. The UAPB Project partnered with PBJHS, according to a news release. PBJHS Principal Arnold Robertson shared the vision behind this collaboration. "The project involved the installation of raised beds in one of the school's courtyards, thus fostering an environment where scholars gained a deeper understanding of the origins of their food, embraced the importance of healthy eating, and actively engaged in planting, nurturing, and harvesting vegetables such as lettuce, tomatoes, cabbage, and bell peppers," Robertson said. In addition, Robertson said this partnership with UAPB has been thriving for the past two years. Students were given the opportunity to cultivate and prepare vegetables within their classrooms. "This hands-on experience not only enriched their education but also facilitated valuable cross-curricular connections in the classroom," according to the release. The program has other benefits. "Overall, PBJHS-UAPB's gardening project has the potential to be a valuable educational tool that exposes scholars to diverse career opportunities and fosters a broader mindset," according to Robertson. School officials were proud to display the garden project. "The school had been handpicked for this special tour, and Mr. Robertson appeared happy and proud as he witnessed the guests' deep admiration for the incredible work achieved in the garden. The guests were also impressed by the enormous steps taken to make healthy eating education culturally relevant. The future looks bright for these young minds, thanks to the exciting initiatives brought to life by this wonderful collaboration," according to the release.
Restoring soil nutrient stocks using local inputs, tillage and sorghum-green gram intercropping strategies for drylands in Eastern Kenya
(UoEm, 2023) Njiru, L.G.; Yegon, J.R.; Mwithiga, G.; Micheni, A.; Gitari, N.J.; Mairura, F.S.
Soil macronutrient and micronutrient availability is particularly critical in semi-arid agro- ecological zones that are characterized by poor soil fertility and low rainfall regimes. An experiment was initiated in Siakago, Embu County to investigate the effects of tied-ridges, conventional tillage and input applications on soil nutrient fertility using a randomized complete block design with a split-split plot arrangement for 4 seasons (2018–2021). The treatments comprised of two main plot tillage systems, three cropping systems allocated to the sub-plots and four soil input management treatments assigned to sub-sub plots. ANOVA was used to test the effects of different treatments including tillage, crop system and soil fertility management using Genstat software. The data was also subjected to Principal Component Analysis procedures using R ("FactoMineR" and "factoextra") to examine the inter-relationship patterns between different soil fertility parameters and to reduce the data into independent soil fertility components. There were significant main effects due to crop system (Soil Mn), tillage and crop system interaction (SOC and TSN) and soil fertility management (TOC, TSN, Ca, Zn). Soil inputs significantly influenced soil carbon concentrations (p = 0.002), with the lowest values observed in the control (0.2 %), followed by sole fertilizer (0.35 %), manure + fertilizer (0.41 %) and the fully decomposed manure treatment (0.61 %). The soil-extracted manganese values recorded significant effects due to crop system, while soil-extracted Zn values were significant due to soil fertility management. Multivariate analysis results revealed the structure of soil nutrient distribution. Tied ridging can improve soil micronutrient availability through reduced soil erosion, conservation of soil organic matter, which can improve soil micronutrient availability. Soil conservation practices such as tied-ridging integrated with organic input applications can enhance multiple nutrient availability for improved crop performance and human nutrition in dryland farming systems where farmers lack soil moisture, technologies and resources to enhance crop nutrient availability.
Efficacy of Metarhizium anisopliae (Mechnikov) Sorokin ICIPE 69 against the melon fly Zeugodacus cucurbitae (Coquillett) infesting courgette (Cucurbita pepo L.) in field cages
(UoEm, 2023-07-21) Dubois, Thomas; Onsongo, Susan K.; Omuse, Evanson R.; Akutse, Komivi S.; Mohamed, Samira A.
Effective integrated pest management (IPM) of the melon fly Zeugodacus cucurbitae (Coquillett), a devastating pest threatening horticultural production in Africa, is urgently needed. In this study, a caged field experiment was implemented in Thika, Kenya to test the efficacy of Metarhizium anisopliae (Mechnikov) Sorokin ICIPE 69 for Z. cucurbitae control in courgette Cucurbita pepo L. Treatments included: (1) dry conidia of M. anisopliae ICIPE 69 applied in an autodissemination device (fungus); (2) dry conidia of M. anisopliae ICIPE 69 in an autodissemination device combined with cuelure, a male attractant (fungus + cuelure); (3) a commercial insecticide (profenofos + cypermethrin) (insecticide); and (4) an untreated control (control). Each treatment was replicated thrice and the experiment was conducted twice during two seasons. Flies (300/tunnel) and treatments were introduced at flowering. One day later, 25 flies/tunnel were randomly collected from each cage to assess conidial acquisition (for fungus and fungus + cuelure treatments only) and mortality during a 10- day interval in the laboratory. Flies in the fungus + cuelure treatment acquired more conidia (18.02 ± 0.48 conidia/fly) than those in the fungus treatment (11.93 ± 0.40 conidia/fly). Flies in the fungus + cuelure treatment experienced the highest mortality (95.31% ± 1.69%), while those in the insecticide treatment experienced the lowest (38.70% ± 4.32%). Dry conidia were collected from the autodissemination devices (in the fungus and fungus + cuelure treatment) daily for 7 days after flowering to check for compatibility through germination tests. Percentage germination reduced over time from 86.45% ± 1.77% and 87.72% ± 1.71% on day 1 to 16.39% ± 2.11% and 42.76% ± 1.74% on day 7 (seasons 1 and 2, respectively). The yield was significantly different among treatments and was, across seasons, highest in the fungus + cuelure (6961 ± 550 kg/ha) and insecticide (7267 ± 352 kg/ha) treatments and lowest in the control treatment (2089 ± 155 kg/ha).
Integrated Soil Fertility and Water Management Practices for Enhanced Agricultural Productivity
(UoeM, 2023-06-23) Ndegwa, Jackline K.; Gichimu, Bernard M.; Mugwe, Jayne N.; Mucheru-Muna, Monicah; Njiru, Daniel M.
Declining agricultural productivity has been a challenge worldwide and especially in Sub-Saharan Africa (SSA). Low agricultural productivity has been attributed to factors such as poor farm management practices, soil moisture stress, soil infertility, and soil degradation, among others. -e nations in the SSA are prone to insu5cient crop yields due to their inadequate capacity to adapt to good agricultural practices that support crop productivity such as integrated soil fertility and water management (ISFWM) practices. -is lowers the farmers’ capacity to improve crop productivity, thus contributing in jeopardizing the food and nutritional security in SSA. Past research has shown that ISFWM strategies have not been properly adopted probably due to the lack of adequate awareness among the farmers about them. In addition, there is limited documentation on the importance of ISFWM in enhancement of soil fertility, water use e5ciency, and sustainable crop production in SSA. -is paper discusses some of the key ISFWM options that have the potential to enhance soil fertility, improve water use e5ciency, and consequently increase agricultural productivity. -e practices include intercropping, use of tied ridges, minimum tillage, mulching, and combined use of organic and inorganic fertilizers.
Nutritional and Phytochemical Composition of Bambara Groundnut (Vigna subterranea [L.] Verdc) Landraces in Kenya
(UoEM, 2023-06-02) Chelangat, Mercy; Muturi, Phyllis; Gichimu, Bernard; Gitari, Josiah; Mukono, Simon
Bambara groundnut (Vigna subterranea) is a highly nutritious legume with good drought tolerance attributes and is therefore a suitable candidate for food and nutritional security especially in drought prone areas. This study was conducted to determine the nutritional and phytochemical composition of seventeen Bambara groundnut landraces that were collected from Vihiga, Kakamega, Bungoma, Busia, and Kisumu Counties in Kenya. Prior to characterization, a field experiment was set up in Ishiara Ward in Mbeere North Sub-County in Embu County for two cropping seasons to standardize and multiply the seeds. The experiment was laid out in a Randomized Complete Block Design with three replicates. The harvested seeds were analyzed for their proximate, nutritional, and phytochemical composition using standard procedures. The moisture content ranged from 3.47 to 6.24%, total ash from 3.17 to 4.69%, crude protein from 21.18 to 26.00%, and fats from 4.56 to 7.02%. Iron levels ranged from 4.07 to 5.13 mg/100 g, sodium from 25.14 to 129.66 mg/100 g, potassium from 819.34 to 1,131.80 mg/100 g, and zinc from 0.06 to 0.42 mg/100 g. The tannin levels ranged from 0.01 to 0.04 mg/g, saponins from 0.82 to 1.06 mg/100 g, alkaloids from 0.01 to 0.12 mg/100 g, and flavonoids from 4.07 to 8.45 mg/100 g. The landraces BG-125, BS-148, and BS-145 with relatively higher nutrients composition and those with high levels of phytochemicals such as BS-104 and MU-137 are recommended to plant breeders for further selection and production of certified seeds. These selections will also be promoted to the farmers for production through various extension programs.
Tied-ridging and soil inputs enhance small-scale maize productivity and profitability under erratic rainfall conditions in central Kenya
(UoEM, 2023) M., Ndung’u; Mugwe, J.N.; Mucheru-Muna, M.W; Ngetich, F.K.; Mairura, F.S.; Mugendi, D.N
Deficits in soil moisture and low soil fertility are the major constraints to smallholder farming systems in the SSA (sub-Saharan Africa) region. This study evaluated the effects of tied ridging and selected soil fertility inputs on; soil water content at different depths, maize yields, and economic returns. The treatments were: Tithonia diversifolia + inorganic fertilizer, manure + inorganic fertilizer, inorganic fertilizer, and control with or without tied ridging as the soil water conservation factor. Data were subjected to analysis of variance, and the means were separated using LSD at p ≤ 0.05. Treatments with Tithonia diversifolia or manure combined with inorganic fertilizer with or without tied ridging consistently affected soil water content positively. The effect of tied ridging on soil water content was greater during the short rain season compared to the long rains. In addition, there was evidence that tied ridging and organic soil inputs resulted in greater soil moisture conservation during the critical silking and tasselling maize phenological stages during the short rain season. Treatments had significant effects on grain and stover yields during the long rain 2016 season (p < 0.0001 and p = 0.0477, respectively) and the short rain 2016 season (p < 0.0001 and p = 0.0035, respectively). The highest (4.87 Mg ha− 1 ) maize grain yield was recorded in Tithonia diversifolia plus inorganic fertilizer under tied ridging in the long rain 2016 season, while manure + inorganic fertilizer without tied ridging gave the highest yields (1.27 Mg ha− 1 ) in the short rain 2016 season. The highest net benefits of US$ 1229.90 ha− 1 and US$ 171.57 ha− 1 were recorded under Tithonia diversifolia plus inorganic fertilizer with tied ridging during the long and short rain seasons, respectively. Overall, the best-performing treatments in yields and profitability were those that combined organic and inorganic fertilizers, regardless of the presence or absence of tied ridging. Climate-smart agricultural strategies combining tied ridges and organic inputs should be an integral component of farmer management if losses related to soil fertility and water stress are to be minimized under erratic rainfall regimes in the semiarid farming systems of the SSA region.

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