- Kenya
Samuel Mwonga
Egerton University, Crops, Horticulture and Soils, Faculty Member
Research Interests: Agronomy, Biology, Agroforestry, Maize, Chickpea, and 9 moreFallow, Zea mays, Crop Rotation, Rift Valley Fever, Dolichos, Soya, Maïs, Garden Pea, and Lablab
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In many smallholder farming systems in sub-Saharan Africa, nutrient supply is either too low leading to soil fertility decline due to soil mining or too high leading to environmental pollution. The aim of our study was the quantification... more
In many smallholder farming systems in sub-Saharan Africa, nutrient supply is either too low leading to soil fertility decline due to soil mining or too high leading to environmental pollution. The aim of our study was the quantification of mineral nutrient transfer from soil to market in African indigenous vegetable (AIV) production systems as guide for development of fertiliser recommendations. In a field experiment under optimal nutrient supply, we measured biomass and mineral nutrient concentrations (nitrogen, phosphorus, sulfur, potassium, magnesium, calcium) of edible (leaves, tender laterals) and non-edible (stems, coarse roots, fine roots) plant organs of six leafy vegetable species (amaranthus Amaranthus cruentus, cowpea Vigna unguiculata, African kale Brassica carinata, African nightshade Solanum scabrum, spider plant Cleome gynandra, common kale Brassica oleracea acephala). In a “batch system”, plants were completely harvested five weeks after transplanting. In a “continu...
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The rainfall pattern in Molo district, situated in the central Rift Valley province of Kenya, is bimodal in nature with long (4-5 months) and short (2-3 months) rain seasons being experienced annually. The short rains are often unutilized... more
The rainfall pattern in Molo district, situated in the central Rift Valley province of Kenya, is bimodal in nature with long (4-5 months) and short (2-3 months) rain seasons being experienced annually. The short rains are often unutilized by farmers partly due to the acidic nature of the soils that is a hindrance to growth of short maturing crops such as legumes. It was thus hypothesized that planting improved fallow legumes; cowpea (CP) and crotalaria (CR) with application of soil amendments; lime (L), rock phosphate (RP), and farm yard manure (FYM) in the short rain season (SRS) would better utilize the SRS fallow. CP and CR were planted in the SRS of 2005 and 2006 with (CPL+RP, CRL+RP and CRL+RP+FYM) and without (CP0 and CR0) application of soil amendments. The experiment was laid out in a randomized complete block design. At CP maturity and CR flowering, the aboveground biomass was incorporated in the soil except in the CRL+RP+FYM treatment where the aboveground biomass was remo...
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Sustainable intensification (SI) approach aims to increase agricultural productivity and farmers’ livelihoods. However, there is limited empirical evidence of impact adopting SI practices (SIPs) on famers’ livelihoods in Sub-Saharan... more
Sustainable intensification (SI) approach aims to increase agricultural productivity and farmers’ livelihoods. However, there is limited empirical evidence of impact adopting SI practices (SIPs) on famers’ livelihoods in Sub-Saharan Africa (SSA). There is need therefore to assess whether adoption of SIPs in actual sense improves farmers’ livelihoods and if so, by what magnitude. This study evaluated the impact of adoption of SIPs on household income based on 685 household-level data from rural and pre-urban vegetable production in Kenya using a treatment effect model. Results show that the correlation coefficients were statistically significant, hence the adoption of SIPs was influenced by both observed and unobserved factors. Further, the findings revealed that adoption of SIP increased crop income by 53.3%, while total household income increased by 12.9%. These findings highlight the need for continued public and private investments on programs and policies supporting adoption of ...
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Cadmium (Cd) is toxic to humans. The most important source for dietary intake is consumption of plant products, whereby Cd concentrations in leafy vegetables are particularly high. In periurban areas, soils are often contaminated with Cd.... more
Cadmium (Cd) is toxic to humans. The most important source for dietary intake is consumption of plant products, whereby Cd concentrations in leafy vegetables are particularly high. In periurban areas, soils are often contaminated with Cd. Thus, recommendations to increase vegetable consumption should consider species-specific uptake and allocation to edible plant organs. Cadmium uptake and distribution within plant was compared in various species to derive recommendations for vegetable production on contaminated soils. Four African indigenous vegetable species (African Nightshade Solanum scabrum, amaranth Amaranthus cruentus, cowpea Vigna unguiculata, spider plant Cleome gynandra), and a standard species commonly grown in Asia (Pak Choi Brassica rapa chinensis) were grown in nutrient solution at three Cd-concentrations: 0.1 (low), 1.0 (moderate) and 2.5 μM Cd (high contamination). Biomass and mineral nutrient concentrations were measured in roots, leaves, stems and lateral branches....
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Food production in smallholder farming systems of sub-Saharan Africa is often constrained by low soil contents of plant-available phosphorus (P). An option to increase food production is cultivation of species with high P efficiency.... more
Food production in smallholder farming systems of sub-Saharan Africa is often constrained by low soil contents of plant-available phosphorus (P). An option to increase food production is cultivation of species with high P efficiency. Plant strategies to improve growth and P acquisition on low P soils include root foraging strategies to improve spatial soil exploitation, P mining strategies to enhance desorption, solubilisation or mineralisation, and improving internal P utilisation efficiency. The aim of this study was to measure plant responses to low P availability in soil and to determine if there is variation among African indigenous vegetables (AIV) in their ability to use organic phosphate and sparingly soluble P forms. Six AIV species (Spider plant Cleome gynandra, African nightshade Solanum scabrum, Amaranthus Amaranthus cruentus, Cowpea Vigna unguiculata, African kale Brassica carinata, Common kale Brassica oleracea) were cultivated under controlled conditions in pots on a ...
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A sole inorganic fertilizer application study was done in southern Mali in Sikasso during the rainy season 2016-2017 to assess its effect on cassava growth and yields parameters. A randomized complete block design (RCBD) experiment with... more
A sole inorganic fertilizer application study was done in southern Mali in Sikasso during the rainy season 2016-2017 to assess its effect on cassava growth and yields parameters. A randomized complete block design (RCBD) experiment with three replicates in two sites was used. The inorganic fertilizer used was the NPK (15-15-15) at 4 rates (0kg ha-1, 100kg ha-1, 200kg ha-1 and 300kg ha-1). Two cassava genotypes, Bonima (local) and Sika (from Ghana) were used in Finkolo and Loulouni. The fertilizer rates were applied in splits at equal quantity, two weeks after planting and the rest two months later. Analysis of soil nutrients before planting and plant leaves N, P and K content were performed. Data on numbers of branches, number of tubers per plant and fresh tuber yield were collected. The Least Significant Difference (LSD) at p=0.05 served to separate means. Our findings showed that Sika genotype and 300 kg ha-1 of NPK are the best genotype and NPK (15-15-15) rates respectively in th...
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Spinach plants were exposed to magnetic field from germination up to maturation, a period of 60 days. The levels of magnetic flux density were 0.5, 1.0, 1.5 and 2.0 mT while exposure time was 10 minutes, 30 minutes and 60 minutes. After... more
Spinach plants were exposed to magnetic field from germination up to maturation, a period of 60 days. The levels of magnetic flux density were 0.5, 1.0, 1.5 and 2.0 mT while exposure time was 10 minutes, 30 minutes and 60 minutes. After 60 days the concentration of iron, calcium, potassium, sodium, magnesium and calcium was analyzed using Atomic Absorbance spectrophotometry. The data was analyzed using excel. Magnetic flux density from (0.5-2) mT and exposure time of (10-60) minutes has a significant effect on elemental composition elements in the leaves of spinach.
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Food production in sub Saharan Africa is constrained by low soil fertility, whereby soil organic matter (SOM) is key factor regulating many soil functions that determine the yielding ability of soils. SOM content is influenced by the mass... more
Food production in sub Saharan Africa is constrained by low soil fertility, whereby soil organic matter (SOM) is key factor regulating many soil functions that determine the yielding ability of soils. SOM content is influenced by the mass and quality of organic carbon input into soil. In smallholder farming systems manure and composts are scarce, and only small fractions are allocated to soil amendment due to alternative use as feed and fuel. Therefore, organic matter input into soil is often restricted to plant residues remaining in the field. In this study, we quantified the effects of species and harvesting method on the mass and quality of plant-derived carbon input into soil with the aim to improve soil fertility management in African indigenous vegetable (AIV) production systems. Five AIV species (amaranthus Amaranthus cruentus, cowpea Vigna unguiculata, African kale Brassica carinata, African nightshade Solanum scabrum, spider plant Cleome gynandra) and common kale (Brassica ...
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This study evaluated the effects of treating cocopeat with calcium nitrate (Ca(NO3)2) at different soaking durations on potato (Solanum tuberosum L.) Apical Rooted Cuttings (ARCs) growth and yield parameters. A greenhouse pot experiment... more
This study evaluated the effects of treating cocopeat with calcium nitrate (Ca(NO3)2) at different soaking durations on potato (Solanum tuberosum L.) Apical Rooted Cuttings (ARCs) growth and yield parameters. A greenhouse pot experiment was carried out at the Climate and Water Smart Agriculture Centre of Egerton University, Kenya. An air-dried cocopeat 1.5 kg per treatment, was treated using five soaking durations (12, 24, 36, 48 and 72 hours) × four levels of Ca(NO3)2 (0, 60, 100 and 150 g) soaked in 15 litres of water. Soil and the untreated cocopeat were used as positive and negative controls, respectively. The treatments were arranged in a completely randomized design with three replicates. The results showed that there was no significant (P>0.05) interaction effect of Ca(NO3)2 × soaking duration for the number of branches and normalized difference vegetative index. The main effect of 150 g Ca(NO3)2 gave the highest average number of branches (16.13), NDVI (0.89) and plant he...
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The intent of this study was to assess the feasibility of engaging youths in secondary schools in disseminating agricultural information among smallholder farmers using a five-month vertical vegetable gardening technology case in Busia... more
The intent of this study was to assess the feasibility of engaging youths in secondary schools in disseminating agricultural information among smallholder farmers using a five-month vertical vegetable gardening technology case in Busia County, Kenya. The research employed mixed research design targeting smallholder farmers and youths in secondary schools. A sample of 132 smallholder farmers and 132 youths in their first, second, and third years of study were selected to participate in the study at the baseline survey, during the intervention, and at the closure survey. The baseline survey was used to identify gaps, followed by participatory training intervention on the mound bed, primary tower, and second wall, to create awareness about vertical vegetable gardening through young farmers' clubs, and a closure survey to assess the change caused by the intervention and the feasibility of the approach. The study used kales, black nightshade, swiss chard, capsicum and carrots as exam...
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Inadequate child feeding practices remain a challenge in some sub-Saharan African countries despite various attempts to introduce age-appropriate diets. This study aims at identifying facilitating and hindering factors to improve the... more
Inadequate child feeding practices remain a challenge in some sub-Saharan African countries despite various attempts to introduce age-appropriate diets. This study aims at identifying facilitating and hindering factors to improve the consumption of fruits among children in Western Kenya. Trials of Improved practices (TIPs) were carried out from August-October 2019 in eight villages in Teso-South Sub-County, Kenya, targeting 53 households with children under eight years of age. The trials included three household visits with counselling to improve children’s diets and to negotiate to test household specific recommendations. Interview guides were used to capture experiences and perceptions of the improved practices. The responses were analysed by performing a structuring qualitative content analysis using QDA-Software. Factors identified to facilitate fruit consumption among children included the availability of fruits or fruit seeds for planting, the influence and positive reactions ...
In Mali, cassava is grown on ultisols in Sikasso region situated in the southern part of the country. The yields are however low due to the low fertility of the cassava growing soils, inadequate fertilizer use and low yielding genotypes.... more
In Mali, cassava is grown on ultisols in Sikasso region situated in the southern part of the country. The yields are however low due to the low fertility of the cassava growing soils, inadequate fertilizer use and low yielding genotypes. This study aimed at determining the effect of four NPK fertilizer (15-15-15) rates (0 kg ha -1 , 100 kg ha -1 , 200 kg ha -1 and 300 kg ha -1 ) applications on growth and yield of two cassava genotypes. A randomized complete block design (RCBD) with three replicates was used in two sites during 2016/2017 cropping season. The fertilizer rates were applied in two splits of equal quantity at two weeks after planting and two months later. Data on plant height, numbers of branches, number of stem, stem diameter, number of tubers per plant, and fresh tuber weight were collected. Data collected were subjected to analysis of variance using Statistical Analysis System (SAS version 9.3). Least Significant Difference (LSD) at p=0.05 was used to separate means....
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Drivers of land use change were captured by the use of DPSIR model where Drivers (D) represented human needs, Pressures (P), human activities, State (S), the ecosystem, Impact (I) services from the ecosystem and Response (R), the... more
Drivers of land use change were captured by the use of DPSIR model where Drivers (D) represented human needs, Pressures (P), human activities, State (S), the ecosystem, Impact (I) services from the ecosystem and Response (R), the decisions taken by land users. Land sat MSS and Land sat ETM+ (path 185, row 31) were used in this study. The Land sat ETM+ image (June 1987, May, 2000 and July, 2014) was downloaded from USGS Earth Resources Observation Systems data website. Remote sensing image processing was performed by using ERDAS Imagine 9.1. Two land use/land cover (LULC) classes were established as forest and shrub land. Severe land cover changes was found to have occurred from 1987-2000, where shrub land reduced by -19%, and forestry reduced by -72%. In 2000 – 2014 shrub land reduced by-45%, and forestry reduced by -64%. Forestry and shrub land were found to be consistently reducing.
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Low soil fertility, soil acidity and prevalence of sheep sorrel weed are the major constraints limiting potato production in the cool highlands of the North Rift, Kenya. An experiment was conducted for 2 seasons (LR 2002 and SR 2002) at... more
Low soil fertility, soil acidity and prevalence of sheep sorrel weed are the major constraints limiting potato production in the cool highlands of the North Rift, Kenya. An experiment was conducted for 2 seasons (LR 2002 and SR 2002) at Timboroa in UH 1-2 agro-ecological zone in Uasin Gishu District to identify suitable legumes for use either as green manures in an intercrop with potatoes to improve soil fertility and ameliorate soil acidity; hence prevent germination and growth of sheep sorrel (Rumex acetosella L.). Eight legumes, namely: purple vetch (Vicia benghalensis), lana vetch (Vicia dasycarpa), lupine (Lupinus albus), lablab bean (Lablab purpureus cv. Rongai), lablab bean (Lablab purpureus cv. Black seeded), velvet bean (Mucuna pruriens), jack bean (Canavalia ensiformis) and lima bean (Phaseolus lunatus) were evaluated. Purple vetch, lana vetch and lupine had significantly higher ground cover and therefore more promising in terms of smothering the sheep sorrel weed in the c...
ABSTRACT A 2-year study was conducted at two sites, Njoro and Mang’u, both in Nakuru district, in 1998–2000 to test the validity of double cropping of selected forage legumes with wheat and test their contribution to enhanced crop yields... more
ABSTRACT A 2-year study was conducted at two sites, Njoro and Mang’u, both in Nakuru district, in 1998–2000 to test the validity of double cropping of selected forage legumes with wheat and test their contribution to enhanced crop yields in a cereal-based cropping system. It was hypothesized that double cropping was possible in order to utilize the short rainy season, where the land is left under natural fallow. The main factor during the short rainy season was different fallow species: Medicago sativa L., Vicia sativa L., Melilotus alba Desr., Crotalaria ochroleuca G. Don, Trifolium subterraneum L., Triticum aestivum L. and a natural fallow. During the long rains, inorganic nitrogen supply to wheat test crop at 0, 20 and 40kg N/ha was applied to make three sub-plots representing zero, full and double N rates, respectively. This factorial combination gave 21 treatments. The trial was laid as RCBD with split plot arrangement replicated three times. Double cropping was possible with some species with only V. sativa and C ochroleuca nodulating. Natural fallow plot recorded yield suppression probably due to wide C:N ratio and possibly allelopathic effects of the previous year’s weeds. Wheat grown after C. ochroleuca produced the highest biomass and grain yields. This demonstrated that double cropping was possible using some species where the complementary legume crop could offer higher nutritive content to maize stover, the main livestock feed during the dry season. KeywordsForage-Legumes-Double cropping-Wheat
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Soil degradation especially soil acidity and low fertility are the major constraints hampering maize production in Molo district, Kenya. The challenge therefore is to develop sustainable soil management strategies for enhancing maize... more
Soil degradation especially soil acidity and low fertility are the major constraints hampering maize production in Molo district, Kenya. The challenge therefore is to develop sustainable soil management strategies for enhancing maize production and concomitantly food security. A three-year field experiment were conducted on smallholder farms (SHF) of Molo to test the effectiveness of applying low cost technologies (LCT): lime,
Research Interests: Agronomy, Low Cost Technology, Food Security, Seasonality, Maize, and 15 moreBiological Nitrogen Fixation, Field Experiment, Fertilizer, Soil Degradation, Green Manure, Acid Soil, Manure, Soil management, Phosphate Rock, soil pH, Soil Acidity, Nutrient Availability, Lime, Cropping System, and Farm Yard manure
The use of legume crops as alternatives to a fallow in wheat–maize rotations in the Rift Valley of Kenya may suppress weeds and add nitrogen to the system. A field study was set up in the Njoro and Rongai regions to evaluate the effect of... more
The use of legume crops as alternatives to a fallow in wheat–maize rotations in the Rift Valley of Kenya may suppress weeds and add nitrogen to the system. A field study was set up in the Njoro and Rongai regions to evaluate the effect of managing the traditional fallow with chickpea (Cicer arietinum L.), field bean (Phaseolus vulgaris L.), soybean [Glycine max (L.) Merril], field pea (Pisum sativum L.) and dolichos [Lablab purpureus (L) Sweet] on the following wheat and maize crops. The objectives of this study were to assess the impact of improved fallow on weed control, soil nitrogen and performance of the following cereals in a bid to improve their yields. The legumes, along with wheat and maize, were grown as fallow-management treatments during the short-rains season, and their residues were incorporated into the soil before sowing the test cereal in the long-rains season. Weed biomass and species diversity reduced by 35–92% and 25–58% at Njoro, and 10–100% and 83–100% at Ronga...
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The traditional natural fallows are no longer practicable in sub-Saharan Africa and technologies to replace them are being popularised through management of short fallow systems. Dolichos [Lablab purpureus (L.) Sweet] is among the legumes... more
The traditional natural fallows are no longer practicable in sub-Saharan Africa and technologies to replace them are being popularised through management of short fallow systems. Dolichos [Lablab purpureus (L.) Sweet] is among the legumes used to improve such fallows and its residues are incorporated to improve yield of succeeding cereal. Two field studies were conducted to determine dolichos residue mineralisation schedule and response of maize to timing of the residue incorporation, to establish if the current residue incorporation practice maximises nutrient benefit to succeeding cereal. Dolichos residue was applied at 2 t/ha in litterbags, buried in the field at 15-cm depth and retrieved after 1, 2, 4, 8 and 16 weeks, and the remaining debris analysed for loss of weight, N, P and K. A parallel split-plot experiment was set up to determine response of maize to time of residue incorporation, with or without fertiliser nitrogen supplementation. The main plot treatments were nitroge...
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The effects of widely spaced trees ofAcacia tortilis andAdansonia digitata on their understory environments were investigated in four savannas located along a gradient of increasing livestock utilization in Tsavo National Park (West),... more
The effects of widely spaced trees ofAcacia tortilis andAdansonia digitata on their understory environments were investigated in four savannas located along a gradient of increasing livestock utilization in Tsavo National Park (West), Kenya. Plant species composition and biomass and the physical and chemical properties of soils that occur below tree crowns were compared to open grasslands. The tree-crown zones at
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Cocopeat, a by-product of the coconut (Cocos nucifera L.), is an important soilless media that contains high potassium (K), sodium (Na), and electrical conductivity (EC) depending on its source. Methods for extracting these elements and... more
Cocopeat, a by-product of the coconut (Cocos nucifera L.), is an important soilless media that contains high potassium (K), sodium (Na), and electrical conductivity (EC) depending on its source. Methods for extracting these elements and thus lowering EC are yet to be standardized. This study was therefore carried out to investigate two extraction methods of these elements in cocopeat. A greenhouse pot experiment was carried out at the Climate and Water Smart Agriculture Centre of Egerton University, Kenya. It was laid out in a 5 × 4 factorial completely randomized design. Five soaking durations (12, 24, 36, 48, and 72 hours) and four calcium nitrate (Ca(NO3)2) levels (0, 60, 100, and 150 g) were used. The experiment was done in two folds: the leachate and treated cocopeat examination for their chemical properties. The General Linear Model procedures were used for Analysis of Variance at (P ≤ 0.05). The results showed that the addition of Ca(NO3)2 100 g extracted significantly more K...