Agro-ecological Zones In Kenya Research Articles

Agronomic management response in maize (Zea maysL.) production across three agroecological zones of Kenya

AbstractMaize (Zea maysL.) productivity in Kenya has witnessed a decline attributed to the effects of climate change and biophysical constraints. The assessment of agronomic practices across agroecological zones (AEZs) is limited by inadequate data quality, hindering a precise evaluation of maize yield on a large scale. In this study, we employed the DSSAT‐CERES‐Maize crop model (where CERES is Crop Environment Resource Synthesis and DSSAT is Decision Support System for Agrotechnology Transfer) to investigate the impacts of different agronomic practices on maize yield across different AEZs in two counties of Kenya. The model was calibrated and evaluated with observed grain yield, biomass, leaf area index, phenology, and soil water content from 2‐year experiments. Remote sensing (RS) images derived from the Sentinel‐2 satellite were integrated to delineate maize areas, and the resulting information was merged with DSSAT‐CERES‐Maize yield simulations. This facilitated a comprehensive quantification of various agronomic measures at pixel scales. Evaluation of agronomic measures revealed that sowing dates and cultivar types significantly influenced maize yield across the AEZs. Notably, AEZ II and AEZ III exhibited elevated yields when implementing combined practices of early sowing and cultivar H614. The impacts of optimal management practices varied across the AEZs, resulting in yield increases of 81, 115, and 202 kg ha−1in AEZ I, AEZ II, and AEZ III, respectively. This study underscores the potential of the CERES‐Maize model and high‐resolution RS data in estimating production at larger scales. Furthermore, this integrated approach holds promise for supporting agricultural decision‐making and designing optimal strategies to enhance productivity while accounting for site‐specific conditions.

Isolation and Identification of Bacterial Soft-Rot-Causing Isolates from Cassava, Homa-Bay County, Kenya

Cassava bacterial soft rot is of great importance to economically valuable crop varieties. Commonly, bacterial soft rot strains cause destructive vegetable and potato diseases worldwide. The strain act similar to other species of the family Enterobacteriaceae that cause soft rot in plants. However, the disease has spread in a wide range of environment with its prevalence and causative strains less known to most agroecological zones of Kenya. Generally, aim of this study was to isolate, characterize and identify bacterial soft rot causative strains in cassava, Homa-Bay County. At the Sub County level, 104 farms were identified through a simple random method and symptomatic cassava plants sampled along laid transect in each farm. Rotten cassava tubers were then randomly sampled, packed and taken to the laboratory for pathogen identification. The bacterial strains were isolated in Nutrient Agar at 37˚c for 24 hours to obtain pure cultures. Identification was done using morphological, biochemical and 16S rRNA analysis method. The study identified: two Pectobacterium carotovorum, three Bacillus species: Bacillus amyloliquefaciens, Bacillus subtilis, and Bacillus tropicus, and three Achromobacter species: Achromobacter marplatensis, Verticiella sediminum, and Achromobacter xylosoxidans, pathogenic strains causing cassava bacterial soft rot. In this study, characterization and identification of cassava bacterial soft rot in Homa Bay County was done for the first time. The results can not only be used in the characterization enzymes produced by cassava bacterial soft rot strains but also in the development of effective control strategy.

Species-Site Suitability Assessment of Bamboo and Its Detailed Study in Different Agroecological Zones of Kenya

The site suitability assessment of Bamboo in Kenya was studied for diverse agroecological zones (AEZs) comprising one indigenous and fifteen exotic bamboo species in nine different AEZs of Kenya. Three bamboo clumps from each species that were at least five years old were assessed to accurately capture data on growth performance and yield. Soil samples collected at 0–30 cm depth from different areas varied considerably. The proportion of soil varied across the bamboo planting sites (F(1,11) = 24.94; p < 0.001), soil pH in the planting sites varied significantly (F(1,11) = 13.92; p < 0.001), and soil bulk densities had different results (F(1,11) = 13.92; p < 0.001). The lowest bulk density (0.61 ± 0.01) was recorded in Kakamega (UM1), while the highest (1.63 ± 0.01) was reported in Gede. Data on characteristics of clumps and internode length and wall thickness integrated through GenStat statistical software using ANOVA entail a huge variation in growth performance for each bamboo species across planting sites. Morphological characters were also studied in detail. The mean height, diameter, and stocking density were comparatively lower even in elevated zones that were only 200 m below its natural range. This resulted in an extremely low yield, which is not viable for economic investment. The species is unsuitable for plantation establishment outside its natural range of 2300 m–3200 m above the sea level (a.s.l.). Plantation below this range will not dissipate but will not attain a healthy growth. The primary use will be restricted for ornamental and conservation purposes such as scaffolding, roof construction, and fabrication of basic household furniture.

Field Screening of Elite Cassava (Manihot esculenta) Mutant Lines for their Response to Mosaic and Brown Streak Viruses

Cassava Brown Streak Disease (CBSD) and Cassava Mosaic Disease (CMD) have been major limiting biotic factors to the productivity of cassava farming in Kenya. Development of resistant cassava varieties is most effective way. The study was to determine response of elite cassava lines to CBSD and CMD under field conditions on different agro-ecological zones in Kenya. Screening was done under hot-spot field conditions where five lines together with their parents were evaluated in Randomized Complete Block Design with three replications at University of Eldoret (UoE), Solai and Marakwet sites in Kenya. Severity assessment done on 1-5 rating scale where 1 very resistant and 5 most susceptible. Elite cassava lines had significant differences in their response (p < 0.05) to CBSD and CMD. Additionally, genotypes, site and time interval were also significant (p < 0.05). The three elite lines (CAS1, CAS2 and CAS3) had better tolerance to both diseases compared to their parents (KME3 and KME4) with KME4 showing visible brown rings on the root typical of CBSD The elite lines CAS1, CAS2 and CAS3 identified to have better adaptability to both CBSD and CMD could be further exploited in breeding for new cassava varieties for Kenya and other countries in the region with similar ecology.

Field evaluation of glutathione and glutamic acid as host marking pheromones for control of Tephritid fruit flies in a mango orchard in Kenya.

Tephritid fruit flies are a major constraint to the global production of horticultural crops. In Africa, an array of native and alien invasive fruit fly species represents a key challenge to the horticultural industry. In an effort to develop a safer management tool for these pests, we previously identified glutathione (GSH) and glutamic acid (GA), as the host marking pheromones (HMPs) of Ceratitis cosyra and Ceratitis rosa, respectively. Here, we report on the effectiveness of these compounds (GSH and GA) in reducing natural fruit fly population infestations in mango orchards. Mango trees at two different agroecological zones in Kenya were sprayed with HMPs, and the fruits sampled periodically and assessed for fruit fly emergence. Fruit fly emergence data were compared to two controls, the positive control using spot spraying of food bait (SS), and the negative control using water (W). The two HMPs and SS substantially decreased fruit fly emergence from the sampled mangoes. GSH and GA treated mangoes showed reduced C. cosyra and C. rosa infestation by ~70-75% relative to control (W), and with variation noted in the pheromone applied and the recovered fruit fly species. The adult emergence in pheromone-treated plants compared favorably with the positive control SS. However, the HMPs had little impact on reducing Bactrocera dorsalis infestation of mangoes. The decrease in fruit fly emergence in sampled mango fruits from HMP treated trees corroborate previous laboratory results and support the prospect of using HMPs in the management of African fruit fly species. © 2022 Society of Chemical Industry.

Lemongrass (Cymbopogon flexuosus) agronomic traits, oil yield and oil quality under different agro-ecological zones

This paper investigated the influence of three agroecological zones (AEZs) in Kenya, namely upper, middle and lower zones on Cymbopogon flexuosus agronomic traits, oil yield and oil quality. Plant height (PHT), number of leaves per clump (NoLC), number of tillers per clump (NoTC), survival rate, herbage yield and oil yield were evaluated at the harvesting time (90 and 150 days after planting) during February and April 2022. The C. flexuosus oil was recovered by steam distillation technique and subsequently assessed for quality using gas chromatography with mass spectrometry (GC-MS) analysis. Results showed that C. flexuosus grown in lower and middle zones had higher PHT, NoLC and NoTC compared to those grown in the upper zone. Plant survival ranged from 73.75 to 90.50%, herbage yield ranged between 10,200 and 13,027 kg/ha and oil yield ranged from 25.34 to 31.74 l/ha across the zones. In total, 49 compounds were identified from the extracted C. flexuosus oil cultivated under the three AEZs using the GC-MS method, with the middle zone characterized by the greatest number of constituents, out of which, 11 oil compounds differed significantly among the three AEZs. The oil yield of C. flexuosus on a fresh weight basis across the three zones ranged from 0.17 to 0.24%, and the main constituents in the essential oil were citral (54.80–71.45%), geranyl acetate (3.73–7.96%), geraniol (3.04–7.02%) and isogeranial (2.29–2.71%). Further, citral, a racemic compound of two isomers neral and geranial, was 69.92 and 71.45% in the oil in upper and lower zones, respectively, indicating that the oil from the two zones attained acceptable quality for its applications. The citral percentage was lower in the middle ecological zone (54.80%) as compared to the other two zones. The present work reflects that AEZs in Kenya affected the C. flexuosus oil yield, oil quality and various agronomic traits. • Cymbopogon flexuosus grown in lower and middle zones had higher PHT, NoLC and NoTC compared to the upper zone. • The main constituents in the C. flexuosus essential oil across the three zones were citral (54.80–71.45%), geranyl acetate (3.73–7.96%), geraniol (3.04–7.02%) and isogeranial (2.29–2.71%). • Citral content obtained from the lower and upper zones attained the required threshold levels for its applications.

Establishment and spread of Cotesia flavipes Cameron: Implication on the local population of Chilo partellus (Swinhoe) across three agroecological zones in Kenya

Establishment and spread of Cotesia flavipes Cameron: Implication on the local population of Chilo partellus (Swinhoe) across three agroecological zones in Kenya

Efficacy of Hexanal Field Spray on the Postharvest Life and Quality of Papaya Fruit (Carica papaya L.) in Kenya

Papaya is a thin-skinned fruit that ripens and softens over a very short time, usually in 3 days, predisposing the fruit to physical damage and phyto-pathogen invasion even with careful handling further shortening postharvest shelf life. The objective of this study was to determine the efficacy of Hexanal, naturally occurring compound, on-farm spray, in managing the postharvest shelf life of papaya in two agro-ecological zones in Kenya. A formulation of Hexanal containing Tween 20 and ethanol was made by volume basis (v/v) and spray treatment at 1 and 2% in “Solo sunrise” and “Mountain” papaya cultivars. The experiment was a randomized block design with ninety-six plants per farm randomly selected. Spraying was applied at 30 days, 30 + 15 days, and 15 days to harvest time on mature green papaya. Control papaya fruits were sprayed with clean tap water as control. Data were collected on color changes and fruit retention on tree. The fruits were harvested when two to three yellow stripes were visible from the lower end of the fruits for postharvest analysis. Hexanal sprayed papaya fruits were retained for at least 13 days longer compared to the control fruits on tree. Hexanal treatment at 2% revealed an improved effect on managing papaya postharvest shelf life. All fruits treated with Hexanal significantly showed reduced rate of color break, softening, and enhanced extension of fruit shelf life by at least 6 days. Hexanal treatment also delayed ethylene and respiratory peaks by three days and showed no significant ( P ≤ 0.05 ) difference in the levels of total titratable acidity and total soluble solids. The results of this study indicate that Hexanal applied as a preharvest spray on mature green “Solo sunrise” and “Mountain” papaya cultivars grown in Kenya, is effective in prolonging shelf life and postharvest quality.

Yield and evapotranspiration characteristics of potato-legume intercropping simulated using a dual coefficient approach in a tropical highland

An accurate estimation of crop evapotranspiration and soil water balance under potato-legume intercropping is important for improving the crop water productivity of rainfed potato. This study quantified the evapotranspiration, yield, and soil water balance of potato (Solanum tuberosum L.) intercropped with lima bean (Phaseolus lunatus L.) or dolichos (Lablab purpureus L.) in comparison to the same crops under monocropping. The experiment was set up in three agroecological zones of Kenya: upper midland (with an altitude range of 1500–1653 m above sea level (masl)), lower highland (1892–1923 masl) and upper highland (2502–2594 masl). The dual crop coefficient approach was adopted with the SIMDualKc model to estimate crop evapotranspiration and compute the soil water balance. The dual crop coefficient partitions crop evapotranspiration into crop transpiration and soil evaporation by applying both soil evaporation and basal crop coefficient. The model was calibrated and validated using field data observed along four crop growth seasons. The basal crop coefficients, the ratios of soil evaporation to evapotranspiration, and that of transpiration to evapotranspiration were determined. The yields of different intercrops were converted into equivalent yield of potato based on price of the produce. Good agreement between the observed and simulated data for available soil water and crop evapotranspiration was found with modeling efficiency > 0.8. The residual mean square error was low and ranged from 0.01−0.08 m3 m-3 for available soil water and 0.03−0.09 mm d-1 for crop evapotranspiration. The transpiration to actual evapotranspiration ratio of potato-legume intercropping was 6−28% greater than that of the sole potato because legume intercrops fully covered the ground by mid-season, thus limiting the energy available for soil evaporation. Crop yields were significantly greater under intercropping as transpiration occurred near its potential rate, thus not limiting yields. These results support the dual crop coefficient method as an appropriate tool to estimate and accurately partition crop evapotranspiration under potato-legume intercropping.

Evaluation of vegetable pigeonpea [Cajanus cajan (L.) Millsp] genotypes for yield stability

BackgroundVegetable pigeonpea is an important food security crop in the marginal dry areas of the Eastern region of Kenya. The adaptation and stability of vegetable pigeonpea genotypes across different agro-ecological zones in Kenya are not adequately determined. The objective of this study was to evaluate the yield stability and adaptability of genotypes: KAT 60/8, MZ 2/9, ICEAP 00554, ICEAP 00557 and KIONZA based on additive main effects and multiplicative interactions (AMMI) and Genotype plus genotype by environment (GGE biplot) analysis.MethodsEvaluation of vegetable pigeonpea Genotypes was conducted at Kiboko, Katumani and Kambi ya Mawe research stations located in Eastern region and University of Nairobi Field station in central region of Kenya. The genotypes were planted in a Randomized Complete Block design (RCBD), replicated three times at all sites. Rainfall at Kiboko and Kabete were supplemented with irrigation, using sprinklers, for a total of 38 times, providing 832 mm of water. The crop was protected from pests by the application of broad-spectrum, non-systemic, pyrethroid alpha-cypermethrin and dimethoate, after field scouting. All other agronomic and cultural practices were done as recommended for each location.ResultsCombined analysis of variance (ANOVA) at six environments revealed highly significant (P < 0.01) variations in G × E interactions for yield (Kg/ha), 100 Seed mass (g/100 seed), days to flower and maturity (P < 0.05). AMMI model for grain yield interaction principal components analysis (IPCA), explained 96.5% of the total yield variation. The cultivar MZ 2/9 and KAT 60/8 recorded a lower IPCA1, indicating a wider adaptation and stability. Kambi ya Mawe, Katumani and Kiboko had higher IPCA1, indicating greatest interactive environments and adapted genotypes. Kambi ya Mawe, was the most ideal location for evaluating pigeonpea genotypes. While KIONZA was the most ideal genotype for yield performance, MZ 2/9 and KAT 60/8 were most stable with a wider adaptation.ConclusionKIONZA should be used as a reference genotype, while Kambi ya Mawe would be the most ideal location for testing the vegetable pigeonpea genotypes in breeding research. Increased deployment of stable pigeon pea cultivars, MZ 2/9 and KAT 60/8 would enhance food security in the dry areas of Eastern regions of Kenya. These genotypes need to be promoted with farmers for wider adoption in the Eastern region of Kenya.

Physicochemical Profile of Essential Oils Obtained from Chia (Salvia hispanica L.) Seeds Grown in Different Agro-Ecological Zones of Kenya

The chia seed samples were purchased from farmers in five locations in three agro-ecological zones in Kenya. The oil was obtained by cold pressing and physicochemical properties were determined; the fatty acid profile was determined by Gas chromatography. The mean oil yield from pressing was 16%, the refractive index of chia seed oil at 25 °C ranged from 1.4811 to 1.4832, specific gravity ranged from 0.9616 to 0.9629, acidity index and free fatty acids content ranged from 0.0345-0.0808 mg KOH/g oil, and 0.1736-0.4061%, respectively. The matter in volatiles ranged from 0.047-0.086%. The saponification value ranged from 162.1969–183.3791 milligrams (mg) of potassium hydroxide (KOH) per gram (g) of chia seed oil. The differences in refractive index, acidity index, free fatty acids, specific gravity, and saponification value, were statistically significant at (P&lt;0.05). The α-linolenic (C18:3) and linoleic acids (C18:2) were the dominant fatty acids in chia seed oil and they varied with regions. The levels α-linolenic (C18:3) and linoleic acids (C18:2) ranged from 53.32-64.04% and 19.37-22.87%, respectively. The levels of oleic, linoleic, and linolenic fatty acids in chia seed oils from different regions were statistically significant at (P&lt;0.05). The study recommended the cultivation of chia seed in agro-ecological zones II and III where higher yields and higher content of linoleic and linolenic fatty acids were reported, consumption of chia seed oil as edible oil, and substitution of marine oils with chia oil as potential sources of polyunsaturated fatty acids.

Physicochemical Profile of Essential Oils Obtained from Chia (Salvia hispanica L.) Seeds Grown in Different Agro-Ecological Zones of Kenya

The chia seed samples were purchased from farmers in five locations in three agro-ecological zones in Kenya. The oil was obtained by cold pressing and physicochemical properties were determined; the fatty acid profile was determined by Gas chromatography. The mean oil yield from pressing was 16%, the refractive index of chia seed oil at 25 °C ranged from 1.4811 to 1.4832, specific gravity ranged from 0.9616 to 0.9629, acidity index and free fatty acids content ranged from 0.0345-0.0808 mg KOH/g oil, and 0.1736-0.4061%, respectively. The matter in volatiles ranged from 0.047-0.086%. The saponification value ranged from 162.1969–183.3791 milligrams (mg) of potassium hydroxide (KOH) per gram (g) of chia seed oil. The differences in refractive index, acidity index, free fatty acids, specific gravity, and saponification value, were statistically significant at (P<0.05). The α-linolenic (C18:3) and linoleic acids (C18:2) were the dominant fatty acids in chia seed oil and they varied with regions. The levels α-linolenic (C18:3) and linoleic acids (C18:2) ranged from 53.32-64.04% and 19.37-22.87%, respectively. The levels of oleic, linoleic, and linolenic fatty acids in chia seed oils from different regions were statistically significant at (P<0.05). The study recommended the cultivation of chia seed in agro-ecological zones II and III where higher yields and higher content of linoleic and linolenic fatty acids were reported, consumption of chia seed oil as edible oil, and substitution of marine oils with chia oil as potential sources of polyunsaturated fatty acids.

English

Papaya is one of the most important fruits crops of Kenya. However, in the recent past, papaya productivity and quality have been limited by lack of high quality seeds. Most producers depend on farmer selected and imported seeds for propagation. However, this is not satisfactory since few farmers can afford imported seeds due to their high price. On the other hand, most of the farmer selected seeds give rise to trees with inferior fruit quality and are susceptible to diseases. The above mentioned challenges necessitated the development of new Jomo Kenyatta University of Agriculture and Technology (JKUAT) papaya lines with superior qualities to help boost fruit production. So far, the new JKUAT papaya has been evaluated only at JKUAT main campus in Kiambu County. This study evaluated the performance of newly developed JKUAT papaya lines (Line 1, 5, 6 and 7) in different agro-ecological zones of Kenya. The study sites were JKUAT (upper midlands zone), Nkubu (upper highlands zone), KALRO Mwea (upper midlands zone) and Mitunguu irrigation scheme (upper highlands zone). The results on morphological, fruiting and biochemical quality showed significant differences. The total number of fruits varied significantly where line 1 had the lowest number (84 fruits) in JKUAT and the highest number was recorded in line 5 (134 fruits) in KALRO, Mwea. The fruit weight varied significantly and ranged from 1.2 kg in line 5 in JKUAT to 2 kg in line 7 in KALRO Mwea. The total soluble solids (TSS) varied significantly from 8.3% in line 7 in KALRO Mwea to 13.7% in line 5 from Nkubu. The results revealed that new lines had good productivity and they should be commercialized in Kenya. However, there is a need to determine the performance of the newly developed papaya lines under heat and water stress conditions. Key words: Agro-ecological zones, fruit quality, fruit yield, morphology, papaya lines.

Soils, sinks, and smallholder farmers: Examining the benefits of biochar energy transitions in Kenya

Besides reducing fuel demands and indoor air pollution, pyrolytic cooking stoves produce a by-product (biochar) that can improve soil fertility and serve as a sink for carbon sequestration. Most smallholder farmers in Africa depend on wood for fuel, suffer from exposure to smoke and soils in their cultivated farms are deteriorating. Biochar (bio-charcoal) production has potentials to reduce energy requirement, diminish exposure to smoke, improve soil health and ease household activities traditionally associated with female labour. However, introducing new technologies and behaviours that tackle existing problems without creating new ones is a complex endeavour. Transitions need to be anticipatory, comprehensive and inclusive. Having this in mind, a trans-disciplinary study was conducted from 2013 to 2019 with 150 households in three agro-ecological zones of Kenya. The socio-economic conditions, the uses of fuels and stoves, the crops grown and fertilizers used, as well as the labour division within households were documented. Selected households were given pyrolitic cooking stoves and trained in applying biochar to the soil. After two years of using the cooking stoves and applying biochar, studies were conducted to assess the feasibility and preliminary impacts based on the households own perceptions and experiences. The results showed that the strategy represented a viable option to deal with fuel use efficiency, exposure to indoor smoke and soil degradation, as well as easing the burden on female labour.

Spatial clustering of livestock Anthrax events associated with agro-ecological zones in Kenya, 1957\u20132017

BackgroundDeveloping disease risk maps for priority endemic and episodic diseases is becoming increasingly important for more effective disease management, particularly in resource limited countries. For endemic and easily diagnosed diseases such as anthrax, using historical data to identify hotspots and start to define ecological risk factors of its occurrence is a plausible approach. Using 666 livestock anthrax events reported in Kenya over 60 years (1957–2017), we determined the temporal and spatial patterns of the disease as a step towards identifying and characterizing anthrax hotspots in the region.MethodsData were initially aggregated by administrative unit and later analyzed by agro-ecological zones (AEZ) to reveal anthrax spatio-temporal trends and patterns. Variations in the occurrence of anthrax events were estimated by fitting Poisson generalized linear mixed-effects models to the data with AEZs and calendar months as fixed effects and sub-counties as random effects.ResultsThe country reported approximately 10 anthrax events annually, with the number increasing to as many as 50 annually by the year 2005. Spatial classification of the events in eight counties that reported the highest numbers revealed spatial clustering in certain administrative sub-counties, with 12% of the sub-counties responsible for over 30% of anthrax events, whereas 36% did not report any anthrax disease over the 60-year period. When segregated by AEZs, there was significantly greater risk of anthrax disease occurring in agro-alpine, high, and medium potential AEZs when compared to the agriculturally low potential arid and semi-arid AEZs of the country (p < 0.05). Interestingly, cattle were > 10 times more likely to be infected by B. anthracis than sheep, goats, or camels. There was lower risk of anthrax events in August (P = 0.034) and December (P = 0.061), months that follow long and short rain periods, respectively.ConclusionTaken together, these findings suggest existence of certain geographic, ecological, and demographic risk factors that promote B. anthracis persistence and trasmission in the disease hotspots.

The Influence of Weather on the Occurrence of Aflatoxin B1 in Harvested Maize from Kenya and Tanzania.

A study was conducted using maize samples collected from different agroecological zones of Kenya (n = 471) and Tanzania (n = 100) during the 2013 maize harvest season to estimate a relationship between aflatoxin B1 concentration and occurrence with weather conditions during the growing season. The toxins were analysed by the ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method. Aflatoxin B1 incidence ranged between 0–100% of samples in different regions with an average value of 29.4% and aflatoxin concentrations of up to 6075 µg/kg recorded in one sample. Several regression techniques were explored. Random forests achieved the highest overall accuracy of 80%, while the accuracy of a logistic regression model was 65%. Low rainfall occurring during the early stage of the maize plant maturing combined with high temperatures leading up to full maturity provide warning signs of aflatoxin contamination. Risk maps for the two countries for the 2013 season were generated using both random forests and logistic regression models.

Agro-morphological characterization of horned melon (Cucumis metuliferus) accessions from selected agro-ecological zones in Kenya

Morphological characterization of genotypes is fundamental in providing information on their genetic status to guide on their conservation and improvement. The objective of this study was to determine agro-morphological diversity within horned melon in Kenya. The study was carried out in two seasons at the University of Embu in Kenya. The study characterized 19 horned melon accessions collected from different agro-ecological zones in Eastern, Central and Western regions in Kenya. The experiment was laid out in a randomized complete block design with three replications. Morphological characterization of the accessions was based on melon descriptors from International Plant Genetic Resources Institute (IPGRI) with slight modifications. Significant differences were observed in all the quantitative traits except the number of branches and main vine length. However, qualitative variations were only observed in fruit shape, rind colour and seed shape. Principle Component Analysis (PCA) showed that fruit weight, main vine length and days to maturity had the highest contribution to the observed diversity. Cluster analysis separated the accessions into seven groups with between classes diversity of 79.20% and within classes diversity of 20.80%. The diversity observed can be exploited by plant breeders for genetic improvement of the crop.

Detection of Potato virus Y associated with African nightshade leafy vegetable (Solanum scabrum miller) in Kenya

Abstract. The African nightshades (ANS) have been part of the food systems in sub-Saharan Africa for generations. They are particularly attractive to small scale farmers because the risks of crop losses are much lower compared to the exotic vegetables. Plant viruses are economically important pathogens affecting African nightshade production. More than 200 plant viruses are reported to infest solanaceous family crops. This study was carried out to detect Potato virus Y associated with African nightshade. Symptomatic leaf samples were obtained from four agro-ecological zones in Kenya. The viral pathogens were detected using serology and molecular techniques. Laboratory experiments were carried out at the University of Nairobi and Kenya Plant Health Inspectorate Service (KEPHIS) from February 2017 to August, 2018. Field samples had the highest mean viral percentage frequency of 44.8% compared to greenhouse samples having 29.8% using serology methods. Molecular testing revealed that greenhouse and farm field sample were positive for the three Potato virus Y strains PVYN:O (necrotic recombinant), PVYO (ordinary) and PVYNTN (necrotic). Detection of Potato virus Y in ANS suggests that it is prevalent in the sampled regions and could cause problems to other solanaceous crops.

Managing climate risk through crop diversification in rural Kenya

Climatic variability and change continue to militate against efforts to increase agricultural productivity and food and nutrition security in many developing countries. Several studies propose crop diversification as a climate risk management strategy to increase production and food security. Most of the empirical studies are based on cross-sectional data that do not account for unobserved factors that may affect crop diversification. A disaggregated analysis of the influence of climatic variability and change on crop diversification by agroecological profiles is less explored. Panel studies also do not combine more than one climatic variability and change indicator as we do. We employ panel data models on farm household and 31-year rainfall and temperature data to analyze the effects of climatic variability and change on crop diversification among small-scale farmers disaggregated by agroecological zones in Kenya. We find widespread crop diversification among small farms in warmer regions as a risk management strategy. Results further show that smaller farm size, limited use of inorganic fertilizer, low household incomes, and limited access to off-farm livelihood options influence the decision to diversify crop production. However, crop diversification is not a one-size-fits-all strategy and should be adopted in situations where it gives maximum benefits, consistent with existing land use policies and known benefits of a specified crop portfolio. Crop diversification should not crowd-out specialization, particularly among resource-endowed farmers.

Optimizing soil nitrogen balance in a potato cropping system through legume intercropping

Negative nitrogen balance represents a major factor causing low potato yield in potato growing areas of Kenya while its excessive surplus poses a significant environmental concern. In order to synchronize this tradeoff, a field trial integrating potato (Solanum tuberosum L.) with lima bean (Phaseolus lunatus L.) and dolichos (Lablab purpureus L.) in intercropping system was conducted in the upper midland [1552 m above sea level (masl), lower highland (1894 masl) and upper highland (2552 masl)] agro-ecological zones of Kenya. Nitrogen gains from mineralization, fertilization, biological fixation, and outputs from biomass accumulation, leaching, volatilization and soil erosion were quantified using standard procedures. Soil N balance ranged from − 10.7 to − 18.1 kg N ha−1 for sole potato, 4.1 to 6.6 kg N ha−1 for intercropping and 2.9 to 22.3 kg N ha−1 for sole legumes. The intermediate range of polyphenol and lignin contents in intercropping enhanced N mineralization with peak N release of 8 to 9 kg N ha−1 matching with peak N uptake by potato (19.9 to 31.2 kg N ha−1). Nitrate was leached below the active root zone in sole potato cropping (4.2 to 46.6 kg N ha−1), a process that was diverged by the deep root systems of legume intercrops. These results suggest that legume intercropping can provide a means of balancing the nitrogen retained in the biomass and soil, thus offering a mechanism for optimizing the soil N balance in smallholder potato farming systems.