RP-Department of Environmental Science

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    Influence of Nutrient Management and Crop Rotation on Soil Weed Seedbank in Tharaka Nithi County
    (JMES, 2024-06) Mwangi, Obadiah; Wambui, Hottensiah; Mucheru-Muna, Monicah
    Soil weed seedbank in crop fields are largely influenced by crop rotation, farming practices and nutrient application. For a better understanding of response of various weed species to these management practices, research was conducted to assess their effect on the soil weeds seedbank population dynamics in 2017-2019. In this study, two nutrient level i.e., 225 kg N ha-1 and 125 kg P ha-1 represented high nutrient input levels applied in commercial systems (Conv-High and Org-High) and 45 kg N ha-1 and 26 kg P ha-1 was used to mimic low nutrient practices common in smallholders farming systems (Conv-Low and Org-Low) in the region of Tharaka- Nithi County. Trials were laid out in a randomized complete block design with four treatments replicated four times. A crop rotation with maize, beans, potatoes and cabbage was used with maize/cabbage 1st year, maize/beans 2nd year and maize/potatoes 3rd year were established within the four farming systems. Soil was sampled at a depth of 0-20 cm at the end of every cropping season. The sample were treated with gibberellic acid to break weed seed dormancy and seed emergency method was used to determine weed seeds in the soil sample. Results were analyzed using Simpson’s diversity index and GenStat 14th edition. From the result, 14 weed species were identified. Amaranthus hybridus, Bidens pilosa, Tagete minuta and Galinsoga parviflora increased in their density with increase in fertilizer application while Schkurihria pinnata and Portulaca oleracea increased with decrease in fertilizer application. Crop rotation resulted contributed to weed density decrease. Conventional high encouraged high weed density compared to Org-high, Conv-Low and Org-low while as Org-Low encourage high weed species diversity λ= 0.1208 compared to λ= 0.115, λ= 0.1080 and λ= 0.0901 in Org-high, Conv-High and Conv- Low, respectively. In weed management, fertility inputs and cropping system are the major factor influencing weed composition in farming systems.
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    Determinants of the Adoption of Climate Change Adaptation Strategies by the Smallholder Farmers in Hiran Region, Somalia
    (JMES, 2024-04) Odawa, A. A.; Mucheru-Muna, M.; Dominic, M.; Mburu, B. K; Omari, E. N.
    East Africa, notably Somalia, is one of the worst-affected regions by climate crises. Adaptation to climate change can be used to minimize many of climate change's negative consequences while maximizing its positive effects. This necessitated the need to; (i) identify the smallholder farmers' adaptation methods to the negative impact of the climate crisis and (ii) identify factors that affect farmers' adaptation practices in the Hiran region of Somalia. The study used a descriptive study design where a random sample of 222 farmers from the Hiran Region were involved. The research surveys among the selected farmers were conducted using a questionnaire. The Binary logistic regression analysis revealed that age, family size, marital status, non-farm income, off-farm jobs, access to credits, access to extension, and support from extension agencies were major predictors of the different climate change adaptation measures of the farmers. Therefore, the Federal government ought to review farmer extension systems and design farm management adoption programs based on the socio-economic and institutional characteristics of the farmers and create a favorable environment for the provision of agricultural credits to the farmers in efforts to boost farmers' climate resilience.
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    Factors Influencing Management of Human Excrement through Biogas Technology in Mukuru Kwa Njenga Slums, Nairobi City County Kenya
    (EANSO, 2024-05) Munyigi, Lilian; Mang’uriu, Daniel
    One of the factors influencing the achievement of sustainable sanitation is the proper disposal of human excrement. The problem is most prevalent in informal settlements, where sewerage systems are rare. One of the approaches considered sustainable is the conversion of human excrement into renewable energy via biogas technology. The purpose of the study, which was guided by Roger's theory of innovation diffusion, was to investigate the key factors that influence human excrement management through biogas technology. Mukuru Kwa Njenga slums were chosen as a study area. A sample of 100 people was selected using systematic random sampling. Data were analysed using a social science statistics package. Multiple linear regression was used to determine demographic factors that influence technology adoption. The Chi-square test was used to examine the relationship between various variables. Tables and charts were used to present the data. The study revealed that gender (p=.001) and education level (p=.000) significantly influence the use of biogas technology in the management of human excrement. Technology failure ((χ2= 10.301, p=.036) and lack of technical skills ((χ2= 7.518, p=.128) have no significant effect on the technology adoption rate. Cultural beliefs (χ2= 23.665, P=.000) have a significant effect on the use of biogas produced from human excrement. The ability of technology to prevent overflowing of faecal matter during heavy rainfall (χ2= 23.937, P=.000) and the prevention of odour from sanitation facilities (χ2=17.983, p= .001) has encouraged many residents to use the technology. The study concludes that technical and socio-economic factors, as well as its relative advantage over other excrement disposal methods, influence its adoption rate.
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    Nitrogen and Phosphorus Mineralization and their corresponding Monetary Values under Long‐Term Integrated soil Fertility Management Practices
    (WILEY, 2024-05) Bolo, Peter; Mucheru‐Muna, Monicah; Kinyua, Michael; Ayaga, George; Nyawira, Sylvia; Kihara, Job
    Introduction: Nitrogen (N) and phosphorus (P) are essential nutrients for plant growth, commonly supplied through costly inorganic amendments. However, despite the benefits of nutrient mineralisation, there is limited quantitative information on its monetary value, and the extent of associated potential financial relief to smallholder farmers, particularly in western Kenya region. Materials and Methods: This study used in situ resin core method to explore the extent of N and P nutrient mineralisation and monetary equivalents under select integrated soil fertility management (ISFM) practices in two long‐term (17 years) trials namely Conservation Tillage (CT1) and Integrated Nutrient Management (INM3). Results: FYM addition increased various soil chemical parameters while sole fertiliser (NPK) reduced soil pH and soil organic carbon (SOC). Phosphorus application was associated with increased P availabillity and its monetary value within the first month (0.29 kg P ha−1 ; USD 1.13 ha−1 ) and second month (1.22 kg P ha−1 ; USD 4.76 ha−1 ) of incubation. The quantities of N mineralised, and their monetary equivalents varied with fertiliser application and incubation times. Nitrogen fertilisation depressed P mineralisation and monetary benefits. FYM application increased P mineralisation and its monetary value within 30 (0.78 kg ha−1 ; ~USD 3.02 ha−1 ) and 60 (1.22 kg ha−1 ; ~USD 4.76) days of incubation. Residue application increased mineralised N (17.48 kg ha−1 ; ~USD 22.79 ha−1 ) after 60 days. Maize and soybean intercropping increased N mineralisation (45.81 kg N ha−1 ) and monetary value (USD 59.76 ha−1 ). SOC and other soil variables, their stoichiometry ratios and N mineralisation were significantly correlated. Combined NPK and FYM application significantly (p ≤ 0.05) increased maize yields and grain prices. Conclusion: These findings reflect potential nutrient‐based economic advantages of ISFM practices to resource‐limited smallholder farmers. Combined application of NPK fertiliser and FYM is integral in not only optimising crop yields, but also driving key soil health‐related parameters and economic benefits.
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    Perception and Knowledge of Solar Photovoltaic Technology in Climate Change Mitigation by Households in Embu County, Kenya
    (JGEESI, 2024-03) Njeru, Pamella Camu; Ndunda, Ezekiel
    Climatic changes continue to impact our ecosystems and livelihoods globally. In the past few decades, have experienced an increase in unpredictable and extreme weather events, precipitating to the three planetary crises of biodiversity loss, climate change and pollution. Embu County in Kenya has not been spared from the resultant climate change impacts. Although globally solar energy is promoted as a sustainable source of energy, its uptake in Embu County remains low. The study sought to assess the uptake of solar photovoltaic technology by households in climate change mitigation and identify the determinants of solar photovoltaic technology uptake. Cross sectional data from a sample size of 395 households in Mbeere- north Sub County in Embu County was collected using data collection tools including questionnaires, interviews, and observations. Purposive and simple random sampling was employed to select the respondents for inclusion in the study. After data collection, qualitative and quantitative data analysis methods were employed to analyze the data including SPSS (statistical package for the social sciences). The results indicate an overall increasing temperature and overall decreasing rainfall in Embu County. Income demonstrated a greater influence compared to other factors in determining the decision to adopt solar appliances at p =0.397. A significant proportion of respondents (36.9%) reported having limited awareness of climate change and its impacts. Social and mass media were main sources of climate information. There was a positive significant correlation between respondents who displayed awareness of climate change and its impacts and the adoption of solar energy and awareness on solar energy adoption as a solution to climate change at p values of 0.348 and 0.140. The results assisted in assessing the uptake of solar photovoltaic in climate change mitigation in Embu County and identify the determinants driving households on the uptake of solar photovoltaic technology.
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    Rainfall and Temperature Trend Analysis using Mann-Kendall and Sen's Slope Estimator Test in Makueni County, Kenya
    (JMES, 2024-03) Muia, V. K.; Opere, A. O.; Ndunda, E.; Amwata, D. A.
    This study sought to analyze annual, seasonal, and monthly rainfall and temperature (minimum and maximum) trends in Makueni County from 1991 to 2020 using the Mann–Kendall (MK) trend test and Theil-Sen’s slope estimator. Data analysis was done in R software. The findings revealed a declining trend in annual and seasonal (short and long rain seasons) rainfall, albeit statistically insignificant. Similarly, monthly rainfall exhibited a downward trend in nine of the twelve months. This decline, however, was only significant in June. The findings revealed a statistically significant upward trend in the county’s annual and seasonal minimum and maximum temperatures across the study period. Similarly, monthly analysis revealed a statistically significant increasing temperature (both minimum and maximum) trend in at least nine of the twelve months. When the data was analyzed by sub county, the results revealed differing trends in annual, seasonal and monthly rainfall patterns with some sub counties experiencing increased rainfall and others decreased rainfall. However, annual, seasonal and monthly temperature (minimum and maximum) analysis revealed an increasing trend in all the sub counties with the most of the observations being statistically significant. These patterns suggest that Makueni county is already experiencing climate change. The findings serve as a foundation for sound climate change policy decisions in the county. They also suggest the need for the development of climate change adaptation strategies targeted at mitigating risks and increasing resilience to climate shocks.
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    Factors Influencing Climate Information Access of the Farmers in Hiran Region, Somalia
    (IPRJB, 2024-02) Odawa, Abdiwali Abdulle; Mucheru-Muna, Monicah; Mburu, Benson Kamau; Omari, Erick Nyaboga
    Purpose:Like other poor states and post-conflict countries, Somalia faces significant challenges in achieving the SDGs, particularly concerningfood security. Because agricultural productivity is compromised, it immediately and significantly jeopardizes the nation's food security. Adapting to climate change can maximize its benefits and lessen many of its horrendous side effects. However, Somalia does not address or cover farmers' access to climatic information, which is important when organizing policy responses. This study's goal was to assess the variables that affect farmers in Somalia's Hiran region's ability to obtain climate information.Methodology:The target population of this study was smallholder farmers in the Hiran region, particularly in the Baladweyn and Bulaburte districts. Both purposive and random sampling were utilized. A questionnaire was used to gather data from 222 randomly chosen smallholder farmers as part of a survey research design. Descriptive statistics and binary logistic regression were used to test the data using STATA and SPSS. The data was presented using tables and figures.Findings:Most farmers (78%) had access to climate information. The most common sources of information on climate crises were radio (95%), agricultural extension agents (80%), and firsthand observation (75%). Gender (p = 0.020), marital status (p = 0.036), education level (p = 0.047), farm size (p = 0.000), distance to the market (p = 0.000), and support from local and international agencies (p = 0.013) had a significant correlation with farmers access to climate information. The report advised Somalia's federal government and regional and foreign non-governmental organizations to proceed with intervention plans, focusing particularly on variables that were identified.Unique Contribution to Theory, Practice, and Policy: Study outcomes contribute significant information to policymakers, professionals, and the federal government of Somalia to develop policies and regulations that are relevant to the farmer's needs to adapt to the negative impacts of climate crises. It will also lead to necessary coordination among different climate actors, stakeholders, and farming communities in the region to fill any climate information gap. This will finally allow farmers to access well-timed and dependable information regarding climate disasters.
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    Interactive Effects of Zai Pits and Convectional Practices with Soil Amendments on Soil Physico-chemical Properties
    (Int. J. Bioresource Sci., 2023-12) Muchai, Serah W.K.; Mucheru- Muna, Monica W.; Ngetich, Felix K.; Gitari, Harun I.; Nungula, Emmanuely Z.; Baaru, Mary
    Soil fertility decline and moisture deficits are major challenges facing crop production in semi-arid areas. Soil water conservation, in combination with nutrient management, might be useful in agricultural land restoration in tropical developing countries. This study aimed to examine the interactive effect of Zai pits and conventional planting with soil amendment on restoring soil physico-chemical properties in semiarid areas. The selected physico-chemical properties were soil pH, soil organic carbon, nitrogen content, available phosphorus, aggregate stability, and soil moisture. A field experiment was carried out for three consecutive cropping seasons SR20, SR21, and LR21. Two planting techniques (conventional and Zai pit) and five soil amendment options (control, cattle manure, Tithonia diversifolia, 60 kg N ha−1, cattle manure + 30 kg N ha-1, Tithonia + 30 kg N ha-1) were tested. Randomized Complete Block Design (RCBD) with twelve treatments and three replications was used. Results revealed a significant increase in soil fertility parameter pH (p<.001), TN (p=0.003), OC (p=0.014), and Av. P (p=0.004). A significant increase in aggregate stability in Zai pits than in conventional planting was equally observed. Additionally, a significant increase in volumetric water content was observed in Zai treatments as compared with conventional treatments at a depth of 35 cm. The combination of soil amendments with Zai pits and conventional planting enhanced soil nutrient availability meanwhile improving water retention. Application of soil amendment with Zai pits and conventional planting is therefore recommended in semi-arid areas. Particularly, Zai pits would be essential for moisture retention and infiltration of water in arid and semi-arid areas.
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    Soil Bacterial Community is Influenced by Long-Term Integrated Soil Fertility Management Practices in A Ferralsol in Western Kenya
    (WILEY, 2023-12) Bolo, Peter; Mucheru‐Muna, Monicah; Mwirichia, Romano K.; Kinyua, Michael; Ayaga, George; Kihara, Job
    Introduction: Soil bacterial community structure, abundance and diversity, important in biogeochemical cycling, are influenced by several anthropogenic and edaphic factors. Numerous agronomic practices have been promoted to improve soil fertility and crop production in western Kenya, but little is known on their impacts on soil microbial diversity in the region. Materials and Methods: In this study, conducted in 2019, we assessed the influence of various long‐term (17 years) agronomic management practices, involving application of farmyard manure (FYM) either sole or under different combinations with inorganic nitrogen (N), phosphorus (P) and potassium (K), using 12 treatments, on bacterial community composition, relative abundance and diversity. The bacterial community composition was assessed through amplicon sequencing on an Illumina Miseq platform conducted in MR DNA Laboratory, USA. Results: The soil bacterial community composition and diversity were predominantly higher under management practices with application of FYM, either sole or in combination with inorganic fertilisers compared to treatments with either sole NPK fertiliser or no input application. Certain bacterial taxa, involving Proteobacteria, Bacteroidetes, Nitrospirae, Fusobacteria, Nitrospinae and Actinobacteria predominated in management practices where FYM was added either solely or in combination with chemical fertilisers. In addition, several soil chemical parameters showed significant influences on bacterial composition, relative abundance and diversity indices. Soil pH, soil organic carbon (SOC), N, K, Ca, Mg, Cu, Zn, Fe and cation exchange capacity consistently showed strong positive correlation with numerous bacterial phyla. Bacterial phyla were significantly affected by treatments. Some bacterial phyla, like Chloroflexi and Acidobacteria, were mostly dominant in treatments applied with organic inputs but were depressed under carbon‐deficient treatments (no‐input control and sole NPK application treatments). Conclusion: This study revealed that long‐term agricultural management practices that seek to improve SOC content and nutrient availability also stimulated bacterial diversity and shifted bacterial composition.
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    Influence of Farmyard Manure Application on Potential Zinc Solubilizing Microbial Species Abundance in a Ferralsol of Western Kenya
    (MDPI, 2023-11) Bolo, Peter; Mucheru-Muna, Monicah Wanjiku; Mwirichia, Romano Kachiuru; Kinyua, Michael; Ayaga, George; Kihara, Job
    Zinc is an important nutrient for plant growth and development. Its availability is influenced by zinc solubilizing microbes (ZSMs). The effects of commonly promoted agronomic practices on the abundance of ZSMs are so far not well understood. In this study, conducted in 2019, we assessed the effects of farmyard manure (FYM) application, either sole or in combination with residue and/or inorganic fertilizer inputs, on ZSM community structure using 11 treatments in a long-term (17 years) integrated soil fertility management experiment located in Western Kenya. Bacterial and fungal community composition were evaluated by amplicon sequencing on an Illumina MiSeq platform. The results showed that putative ZSMs (i.e., the ZSMs generally considered to possess the zinc solubilizing capabilities) were clustered in two major clades based on either the application or no application of FYM. Sole application of FYM significantly (p < 0.05) increased the abundance of several ZSMs under a maize–Tephrosia rotation. In addition, systems with the combined application of FYM with other inputs generally showed significantly increasing trends for some ZSMs under a maize–Tephrosia rotation. Moreover, the combined application of FYM and P rather than only P significantly increased the abundance of some ZSMs under maize monocropping systems. Furthermore, as well as affecting ZSM abundance, soil chemical variables involving soil organic carbon (SOC), total N and Olsen P significantly increased with FYM application. This study indicated that management practices such as the application of FYM that increase SOC, and other soil chemical parameters, also/concomitantly increase ZSM abundance. These results imply enhanced capacities for microbial-linked zinc availability with FYM application.
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    The Spatial Distribution of Quarry Stone Mining Sites in Igembe South Sub County Meru County, Kenya
    (JHSS, 2023) Muriki, Joseph Gitonga; Wambugu, Stephen; Obando, Joy
    The objective of this study was to develop a GIS-based spatial distribution of mining site patterns in order to identify risk-prone geo-locations in Meru County's Igembe South Sub County. Data was collected using PRA methodologies and processes, primary data was collected from participants' notes to detect mining-related problems, and an informal and formal survey and pair-wise assessment was used. There has been concern about the spatial distribution of mining in affected areas. The communities and mines in the Akachiu ward are as follows: Auki, Amwamba, Nceme, Kirindine, and Tiira. Information was obtained from 300 respondents. These issues were resolved by segmenting the target population and confirming field observations. Data were analysed using the nearest neighbour analysis method and descriptive means, median, and mode statistics. Results were then presented using tables, maps, graphs, and pie charts. Results established that mining activities have damaged land in Igembe South Sub-County, reducing food production and agricultural demands and polluting water supplies in the area, including contaminated streams. Pollution and noise are present in the area. It was affirmed that the residents know the environmental consequences of mining. In light of the County Government of Meru's efforts at restoration and intervention, such as re-afforestation, the mining companies and the County Government of Meru are reviewing their methods of operation and providing alternatives to the affected areas. Mining's environmental impact should be reduced by rethinking the environmental management strategy.
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    Adoption of Climate Change Friendly New Rice For Africa (NERICA) Varieties among Farmers in Mwea West Sub-County, Kenya
    (AJEST, 2022) Mburu, Benson Kamau; Ngucia, Christine Wanjiku
    Climate change and inefficient water utilization have led to marked fluctuations of the mean rice crop production in sub-Sahara Africa. In order to improve food security and households’ income, adaptation strategies to climate change such as the adoption of new rice varieties are inevitable. This study examined the farmers’ perception and adoption of climate change friendly New Rice for Africa in Mwea West Sub-county. The study applied the descriptive survey design with questionnaires being administered to a sample of 376 farmers. Key informants included four officers from Mwea Irrigation Agricultural Development and the Ministry of Agriculture. Quantitative data were analysed using Statistical Package for Social Sciences whereas qualitative data were analysed through establishing the categories and themes, relationships/patterns, and conclusions drawn in line with the study objectives. Results indicated a highly significant difference in adoption between farmers affiliated to Mwea Irrigation Scheme and the out-growers (X2 = 18.5, df =2, p= 1.67×10-6 ). The study concluded that the adoption of New Rice for Africa varieties in the Mwea West Sub-county is low and slow. This is mainly caused by inadequate information among the farmers as well as low market demand for the rice varieties. There is a need to enhance these rice varieties by intensifying efforts to sensitize farmers.
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    Challenges and Opportunities of Participatory Management of Upland Wetland in Kiambu County, Kenya
    (SIB, 2020) Kinyariro, Mwaura Samuel; Njuguna, Steven Gichuki; Macharia, Geoffrey
    Kinyariro MS, Njuguna SG, Macharia G. 2020. Challenges and opportunities of participatory management of Upland Wetland in Kiambu county, Kenya. Bonorowo Wetlands 10: 78-91. Wetlands are continuously degraded through agricultural activities, pollution, and settlements. For example, in the Lari sub-district, increased population pressure decreased soil fertility, unreliable rainfall, and the search for food security forced farmers to encroach on the seemingly idle Upland Wetlands. Opportunities for wetland conservation lie in participatory approaches applied locally to conserve this vital natural resource. The main water of the Ruiru river comes from the Upland Wetlands harvested by the Nairobi Water and Waste Company in the Githunguri sub-district at the Ruiru dam. This research is critical because the water company does not have in-depth information about its catchment area, which leads to encroachment and ultimately rationing of water in the city of Nairobi. This study aims to document the causes of wetland degradation in the highlands, assess the level of community participation, and determine the level of awareness of the importance of wetlands and the possible contribution of farmer involvement in catchment management. The sampling method used to select the research unit was stratified and random sampling where farmers and Ruiru dam workers were given a questionnaire. Purposive sampling was used to determine the WARMA manager, WRUA officer, and six older people interviewed. 40 farmers from the Lari 107 settlement scheme where the wetlands are located, and four workers of the Ruiru dam were given questionnaires. Data analysis was performed using the Chi-square package computer, T-test, and SPSS. Percentages for qualitative data are presented using tables, bar charts, and pie charts. The wetland mapping was carried out using GIS and Google Earth. The study results found that the total land cover of upland rice fields was 129.6 Ha after deducting 105.4. Ha for the last thirty years due to encroachment. The study revealed that 65% of respondents had lived in the area for more than 20 years. Farmers drain wetlands primarily for food supply (50%) to generate income (25%), while 10% control waterborne diseases. Participation rates are negligible, with only 2.5% of respondents participating in wetland conservation. Community-based conservation groups like WRUA still lack in this area. Environmental impacts include loss of biodiversity, destruction of ornithological habitat, and loss of hydro plant species. Social effects include outbreaks of waterborne diseases such as typhoid, water pollution, and weak community conservation infrastructure. However, there is a chance for community involvement, where the majority of the population is ready to carry out conservation (X2 = 0.127, p = 0.001). The formation of community-based conservation groups such as the Water Resources Users Association, the Association of Riverland Owners, and the Watershed Advisory Committee was proposed as the primary solution. Devolution of water resources is also proposed to ensure local people benefit from selling water to city residents. Such efforts would provide an adequate water supply to Nairobi and the surrounding satellite cities
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    Factors Influencing Biofuel Production in Western Kenya
    (IJLSAR, 2023) Kiptoo, Daisy; Waswa, Sharon; Njiru, Magdalene Kagendo
    : Biofuel production is at the forefront of the agenda of many countries across the globe in the quest to lower greenhouse gas emissions and improve energy access. The increase in oil prices and climate change have been the drivers to ensure the adoption of biofuels. With the global consumption of oil projected to increase, biofuel provides a viable option for a clean, affordable, and climate-friendly source of fuel. However, biofuel production is in Kenya faced with various challenges. Therefore, the study sought to assess the factors that influence biofuel production in Western Kenya. The qualitative research design was adopted with both primary and secondary data collected. Data collection was through interviews, focus group discussions, case studies, and a review of secondary data. The results established that there was a link between food security and biofuel production. Factors influencing the production of biofuel in Western Kenya included the lack of a specific national biofuel policy framework that promotes sustainable development and use of biofuels, limited research, insufficient feedstock to increase production, over-reliance on rain-fed agriculture to grow energy crops, inadequate technology and technical expertise and some knowledge among stakeholders regarding the need and importance of biofuel deployment across the country. There is need for alternative sustainable farming methods that can incorporate cane farming and food crop farming to ensure food security, better farming practices to increase the cane yield, and research on consumer attitudes and behaviours towards biofuels to promote the adoption of the technology.
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    Zai Technology and Integrated Nutrient Management for Improved Soil Fertility and Increased Sorghum Yields in Kitui County, Kenya
    (Frontiers in Sustainable food Systems, 2021) Kebenei, Mercy Cheruto; Mucheru-Muna, Monicah; Muriu-Ng’ang’a, Felista; Ndung’u, Charles Kimani
    Deteriorating soil fertility, low unreliable rainfall and soil moisture stress has resulted to low crop yields among farmers of sub-Saharan Africa (SSA), necessitating a search for more sustainable production practices. Zai technology has the ability to promote soil moisture retention and enhances soil fertility. A four-seasons field experiment was conducted to assess the impact of Zai technology combined with cattle manure and inorganic fertilizer on selected soil properties and sorghum yields in Kabati, Kitui County. The experiment was set up in a Randomized Complete Block Design (RCBD) with eight treatments replicated thrice with sorghum Gadam as the test crop. Soil sampling was done at the beginning of the first season and at the end of the fourth season at a dept of 0–15 cm across each plot for laboratory analyses. From the results, the increase in electrical conductivity was significant at p < 0.05 in all the treatments after four cropping seasons. Total organic carbon significantly increased in Zai with cattle manure (p = 0.045), conventional with no input (p = 0.038) and conventional with cattle manure (p = 0.045). Available phosphorous significantly (p < 0.05) increased in treatments under Zai technology while total nitrogen significantly (p < 0.05) reduced after the four cropping seasons. There was a significant (p < 0.05) interactive effect of the tested factors on soil pH, electrical conductivity, total nitrogen, and available phosphorous at the end of the experiment. Moreover, there was significant (p < 0.05) interactive effects on grain yields (SR18 and SR19 seasons) and stover yields (SR18, LR19, and SR19 seasons), with higher yields being recorded in treatments under Zai technology. This study demonstrates the importance of Zai technology in increasing crop yield by trapping water and enhancing its retention and infiltration into the soil for uptake by plants. This study concluded that positive impacts on important soil properties and crop yield could be realized when Zai technology is utilized alongside either sole inorganics or a combination of organic and inorganic amendments and this could be used as a strategy to improve crop production in eastern Kenya and other similar areas.
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    A Quantitative Appraisal of Selected Agroforestry Studies in the Sub-Saharan Africa
    (Cell Press, 2022) Muthee, Kennedy; Duguma, Lalisa; Majale, Christine; Mucheru-Muna, Monicah; Wainaina, Priscilla; Minang, Peter
    The multiple ecosystem services and livelihood assets development challenges facing the world, including climate change, land degradation, and high poverty levels, have necessitated cross-cutting solutions. Such includes agroforestry technologies, where trees are integrated with crop and pasture lands to yield multiple ecosystem goods and services. Though an ancient approach to land management, agroforestry faces a modern and urgent demand for expansion to counter ecosystems-livelihoods imbalances in most regions across the globe. This paper sought to synthesize the dynamics and characteristics of agroforestry technologies in sub-Saharan Africa by adopting the systematic review approach. Eighty-six (86) agroforestry studies were reviewed, analysing variables such as the dominant agroforestry technologies, production systems, types of studies, and ecosystem services generated by different agroforestry technologies. It established that majority of the agroforestry studies are multiple (undefined) in nature at 36%, have moderately changed over the years, the dominant agroforestry study type is journal articles (59%), and they are mostly scientific in nature (57%). Further, income generation was the dominant provisioning service (31%), greenhouse gas emission reduction was the main regulatory service (31%), and soil fertility management was the key support service. Tradeoffs associated with agroforestry technologies, including increased deforestation rates, tree-crops competition, increased pests and diseases, and potential food insecurity due to reduced crop production were also identified. Barriers to agroforestry such as insecure land tenure systems and inadequate research development are discussed. Pathways towards increased agroforestry technologies adoption, such as creating a conducive institutional and policy environment, as well as developing business support services for agroforestry-related goods and services were identified. The study reiterates the need for increased agroforestry technologies adoption to create the ecosystems-livelihoods balances, with sufficient measures to minimize the potential tradeoffs.
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    Managing Soil Organic Carbon in Tropical Agroecosystems: Evidence from Four Long-Term Experiments in Kenya
    (Copernicus Publications for EGU, 2023) Laub, Moritz; Corbeels, Marc; Couëdel, Antoine; Ndungu, Samuel Mathu; Mucheru-Muna, Monicah Wanjiku; Mugendi, Daniel; Necpalova, Magdalena; Waswa, Wycliffe; de Broek, Marijn Van; Vanlauwe, Bernard; Six, Johan
    In sub-Saharan Africa, maize is one of the most important staple crops, but long-term maize cropping with low external inputs has been associated with the loss of soil fertility. While adding high-quality organic resources combined with mineral fertilizer has been proposed to counteract this fertility loss, the long-term effectiveness and interactions with site properties still require more understanding. This study used repeated measurements over time to assess the effect of different quantities and qualities of organic resource addition combined with mineral nitrogen (N) on the change of soil organic carbon (SOC) contents over time (and SOC stocks in the year 2021) in four ongoing long-term experiments in Kenya. These experiments were established with identical treatments in moist to dry climates, on coarse to clayey soil textures, and have been conducted for at least 16 years. They received organic resources in quantities equivalent to 1.2 and 4 t C ha−1 yr−1 in the form of Tithonia diversifolia (high quality, fast turnover), Calliandra calothyrsus (high quality, intermediate turnover), Zea mays stover (low quality, fast turnover), sawdust (low quality, slow turnover) and local farmyard manure (variable quality, intermediate turnover). Furthermore, the addition of 240 kg N ha−1 yr−1 as mineral N fertilizer or no fertilizer was the split-plot treatment. At all four sites, a loss of SOC was predominantly observed, likely because the sites had been converted to cropland only a few decades before the start of the experiments. Across sites, the average decline of SOC content over 19 years in the 0 to 15 cm topsoil layer ranged from 42 % to 13 % of the initial SOC content for the control and the farmyard manure treatments at 4 t C ha−1 yr−1 , respectively. Adding Calliandra or Tithonia at 4 t C ha−1 yr−1 limited the loss of SOC contents to about 24 % of initial SOC, while the addition of sawdust, maize stover (in three of the four sites) and sole mineral N addition showed no significant reduction of SOC loss over the control. Site-specific analyses, however, did show that at the site with the lowest initial SOC content (about 6 g kg−1 ), the addition of 4 t C ha−1 yr−1 farmyard manure or Calliandra with mineral N led to a gain in SOC contents. The other sites lost SOC in all treatments, albeit at site-specific rates. While subsoil SOC stocks in 2021 were little affected by organic resource additions (no difference in three of the four sites), the topsoil SOC stocks corroborated the results obtained from the SOC content measurements (0–15 cm) over time. The relative annual change of SOC contents showed a higher site specificity in farmyard manure, Calliandra and Tithonia treatments than in the control treatment, suggesting that the drivers of site specificity in SOC buildup (soil mineralogy, soil texture, climate) need to be better understood for effective targeting management of organic resources. Farmyard manure showed the highest potential for reducing SOC losses, but the necessary quantities to build SOC are often not realistic for smallholder farmers in Africa. Therefore, additional agronomic interventions such as intercropping, crop rotations or the cultivation of crops with extended root systems are necessary to maintain or increase SOC.
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    Maize Grain Yield and Grain Zinc Concentration Response to Zinc Fertilization: A Meta-Analysis
    (Cell Press, 2023-05-05) Mutambu, Dominic; Kihara, Job; Mucheru-Muna, Monicah; Bolo, Peter; Kinyua, Michael
    Zinc deficiency in agricultural soils is a current global agroecosystems challenge. Maize exhibits elevated susceptibility to Zn deficiency and low response to zinc fertilization. As a result, there are contradicting literature reports on the crop response to zinc fertilization. This meta-analysis synthesized the current evidence on maize response to zinc fertilization from different studies and highlighted the potential innovations to improve the crop response to zinc application. Systematic literature searches were conducted on the Web of Science and Google Scholar for peerreviewed publications. From the selected publications, data extracted were maize grain yield and maize grain zinc concentration. The meta-analysis was conducted in R statistical environment using the metafor package. The ratio of means was the chosen effect size measure used. The assessment of effect size heterogeneity showed that the study effect sizes were significantly heterogeneous and also publication bias was evident. The analysis showed 17% and 25% maize grain yield and grain zinc concentration response to zinc fertilization. As a result, zinc fertilization was associated with yield increments of up to 1 t ha− 1 and 7.19 mg kg− 1 grain zinc concentration over the control (no zinc application). Despite the observed maize grain response to zinc application, the median concentration of grain Zn was below the 38 mg kg− 1 recommended maize grain zinc concentration to combat human zinc deficiency (hidden hunger). As a result, potential innovations likely to achieve sufficient maize grain zinc content were highlighted including the use of nano-particulate zinc oxide, foliar zinc application, timing of zinc application, precision fertilization and zinc micro-dosing. Due to scanty literature on the progress of these innovations in maize, follow-up studies are recommended to evaluate their potential success in the agronomic bio-fortification of maize with zinc.
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    Variations in Plant Nutrient Allocation, Physiological Development Patterns and Soil Structural Characteristics as Influenced by Zero Tillage Systems in the Central Highlands of Kenya
    (2022) Kinyua, M.W.; Kihara, J.; Bolo, P.; Mucheru-Muna, M.W.
    The global food requirements are projected to rise above the current demand. Surface application of residues in zero tillage results to nitrogen immobilization, posing nutrient use efficiency challenges, while tillage and crop residue removal destroys soil structure. Little is documented on how integrated use of crop residues and inorganic nitrogen under zero tillage could affect plant nutrient allocation, physiological development, and soil structural improvement relative to conventional tillage systems. A study was conducted to: (i) assess how nitrogen and phosphorus accumulation in maize grain and stover are affected by application of different rates of residue and inorganic nitrogen in conventional relative to zero tillage systems, (ii) examine how maize development is influenced by application of different levels of residue, inorganic nitrogen and tillage and (iii) assess how application of residues, inorganic nitrogen and tillage influence soil aggregate stability. An on-station trial was set in a randomized complete block design replicated three times during the 2015 short rain season. Six treatments were laid, comprising a combination of different rates of maize stover residues (0, 3 and 5 tons/ha) and nitrogen as urea (0, 80, 120 kg/ha), in conventional relative to zero tillage systems. Soil was sampled to assess nitrate- nitrogen concentration at four depths, namely, at sowing, 8th leaf, 10th leaf and dent stage, soil carbon and aggregates at the four depths at the end of the season. Minidisc infiltrometer of 0.25 radius was used monthly to assess treatment effects on soil hydraulic conductivity #Corresponding author:m.kinyua@cgiar.org and leaf chlorophyll recorded every fortnight from maize topdressing to tasselling using SPAD-502 meter. Analysis of variance was done using GenStat analysis software 14th edition, means separated using least significant difference (P≤0.05). Residue application in conventional tillage increased nitrogen (56%) and phosphorus (29%) allocation in maize grain compared to when equivalent rates of inputs were applied in zero tillage while increasing residue quantity from 3 to 5 t/ha increased grain phosphorus allocation by 24% (P≤0.05). When equal rates of inputs were applied in zero and conventional tillage, the latter had taller (12.3%) plants (P≤0.05) but with similar leaf area index and chlorophyll content as those of zero tillage. At 0-5 cm, the large macro aggregates were affected by depth and treatment × depth interaction (P≤0.01) with zero tillage+5R+80N having 41% higher large macro aggregates than zero tillage+3R+80N. The ability of zero tillage+5R+80N treatment to increase grain phosphorous allocation, moderate leaf nitrogen levels through maize vegetative stages and produce higher macro aggregate proportions prompts its consideration as a best nutrient management zero tillage strategy for central highlands of Kenya. Its feasibility under mixed farming system characterized by stiff competition for stover with the livestock component requires a further study.
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    Impact of Development and Management Options on Water Resources of the Upper Mara River Basin of Kenya
    (Wiley Online Library, 2020) Omonge, Paul; Herrnegger, Mathew; Gathuru, Gladys; Fürst, Josef; Olang, Luke
    This study employed the Water Evaluation and Planning model to evaluate selected policy-based water development and management options on water resources of the upper Mara Basin of Kenya. The major water resources of the region were identified and quantified to establish the current demand versus supply status. Data on domestic water consumption, agricultural demand and industrial consumption were collected through a rigorous fieldwork campaign and used to define the current state of water use and demand. The water resource model was calibrated and validated against observed discharges and subsequently used to simulate the selected policy-based options. Results indicate that an increase between 49% and 180%, depending on the assumed scenario, in annual water demand is expected by the year 2030. As a conclusion, the simulations demonstrate that there is both the need and significant potential to reduce the demand by implementing water conservation measures.