Semi-arid Eastern Kenya Research Articles

Farmers’ participatory selection for early bulking cassava genotypes in semi-arid Eastern Kenya

Cassava is an important food security crop in semi-arid, Eastern Kenya, but production is constrained by planting late bulking landraces. Therefore, farmer participatory variety selection was initiated with the aim of identifying early bulking varieties with preferred root qualities. Four popular local varieties were crossed with six early-bulking varieties selected from IITA germplasm in a North Carolina II mating scheme. The resultant 225 cloned F1 progenies were evaluated for early bulking in a 15 x 15 simple lattice design with two replications at KARI-Kiboko farm in Eastern Kenya. Sixty-five farmers participated in the selection of early bulking genotypes with preferred root qualities during the second and third harvests at 7 and 8 months after planting. At 7 months, there was a significant variation among genotypes for root bulking, cyanide content, dry matter content, harvest index and root number. Farmers subjected all the genotypes to a preference test and selected 30 genotypes (13%), which combined early-bulking and high root quality. A selection index based on farmers’ ranking of agronomic traits was then imposed on the selected 30 genotypes to identify those that were superior in both agronomic and end-user traits for possible release and advancement. The selected genotypes were all significantly superior to the parents. The top 10 genotypes displayed above average performance for all agronomic traits. Involving farmers in selection helped to identify early bulking genotypes with end-user root qualities that could/should ultimately accelerate their adoption. Key words: Cassava, participatory, early bulking.

Integrated soil fertility management enhances population and effectiveness of indigenous cowpea rhizobia in semi-arid eastern Kenya

Legume biological nitrogen fixation is an environmentally friendly and economical means that can reduce low resource farmer dependence on expensive chemical nitrogen (N) fertilizers. We investigated the effect of two cowpea ( Vigna unguiculata (L.) Walp) varieties (IT95K-52-34, an international variety from IITA and Kang’au, a local variety) under an integrated soil fertility management trial on indigenous symbiotic rhizobia in a semi-arid farmer's field in eastern Kenya. The ox-ploughed field trial had the following treatments: an unamended control, manure applied at 2.5 t ha −1, triple superphosphate (TSP as (P 2O 5, 0:46:0) at 15 kg ha −1; and a combination of manure and TSP applied at the single rates. Soil samples were collected from each treatment during planting and harvesting of the cowpea crop and used in most probable number (MPN) plant infection assays with the two cowpea varieties as traphosts in Leonard jar growth systems and grown under glasshouse conditions. Generally, soil amendments enhanced cowpea rhizobial populations which varied from 4.89 × 10 2 rhizobia g −1 soil to 1.074 × 10 3 rhizobia g −1 soil. The highest shoot biomass accumulation occurred on cowpea variety IT95K-52-34 plants inoculated with soils from the manure applied plots. We isolated 150 fast- and slow-growing cowpea rhizobia. Contrary to most previous studies, the bulk (97%) of the isolates was fast growing which grouped into 9 types on the growth characteristics on yeast extract agar (YEMA). The study indicated that ISFM was important for rhizobia population build up over a cowpea-growing season.

Participatory plant breeding approach for host plant resistance to bean fly in common bean under semi-arid Kenya conditions

Common bean (Phaseolus vulgaris L.) is the most important legume crop in Kenya. It is cultivated across a wide range of agro-ecologies which include high potential and marginal areas. Eastern Kenya alone, largely semi-arid, accounts for 35% of the country’s total bean production. Bean farmers mainly small-scale have limited access to quality seed, chemical pesticides and fertilizer. Therefore, bean yield under on-farm conditions still remains below 500 kg ha−1 while the potential is about 1,200 kg ha−1 under semi-arid conditions. To asses the farmers’ views on bean varieties and a key insect pest and associated constraints contributing to yield loss, research was undertaken. The research included survey to quantify the yield loss and Participatory Rural Appraisal to determine the level of adoption and criteria for variety choice in semi-arid eastern Kenya (SAEK). The results show that farmers consider drought and insect pest problems as main causes for low yields. The adoption rate for improved varieties is high but self sufficiency in beans stands at 23% in the dry transitional (DT) agro-ecology and at 18% in the dry mid-altitude (DM) agro-ecology, respectively. This could be attributed to low adaptability since most of the improved varieties grown were selected for high potential areas but now found in marginal areas. Drought, earliness, yield stability, and insect pest resistance are the main reasons for choice of varieties by farmers. Bean fly (Ophiomyia sp.) was identified as one of the key crop pests of beans limiting yield. Besides, African bollworm (Helicoverpa armigera) and bean aphid (Aphis fabae) were ranked higher. Due to limitations of the conventional breeding approach, a participatory plant breeding approach is suggested so as to provide an opportunity to develop insect pest resistant varieties adapted to the SAEK region.

Simulating phosphorus responses in annual crops using APSIM: model evaluation on contrasting soil types

Crop simulation models have been used successfully to evaluate many systems and the impact of change on these systems, e.g. for climatic risk and the use of alternative management options, including the use of nitrogen fertilisers. However, for low input systems in tropical and subtropical regions where organic inputs rather than fertilisers are the predominant nutrient management option and other nutrients besides nitrogen (particular phosphorus) constrain crop growth, these models are not up to the task. This paper describes progress towards developing a capability to simulate response to phosphorus (P) within the APSIM (Agricultural Production Systems Simulator) framework. It reports the development of the P routines based on maize crops grown in semi-arid eastern Kenya, and validation in contrasting soils in western Kenya and South-western Colombia to demonstrate the robustness of the routines. The creation of this capability required: (1) a new module (APSIM SoilP) that simulates the dynamics of P in soil and is able to account for effectiveness of alternative fertiliser management (i.e. water-soluble versus rock phosphate sources, placement effects); (2) a link to the modules simulating the dynamics of carbon and nitrogen in soil organic matter, crop residues, etc., in order that the P present in such materials can be accounted for; and (3) modification to crop modules to represent the P uptake process, estimation of the P stress in the crop, and consequent restrictions to the plant growth processes of photosynthesis, leaf expansion, phenology and grain filling. Modelling results show that the P routines in APSIM can be specified to produce output that matches multi-season rotations of different crops, on a contrasting soil type to previous evaluations, with very few changes to the parameterization files. Model performance in predicting the growth of maize and bean crops grown in rotation on an Andisol with different sources and rates of P was good (75-87% of variance could be explained). This is the first published example of extending APSIM P routines to another crop (beans) from maize.

Exploring options for integrated nutrient management in semi-arid tropics using farmer field schools: a case study in Mbeere District, eastern Kenya

The farmer field school (FFS) approach was used in semi-arid eastern Kenya in the period 2002–2003 to explore technology options for addressing declining soil fertility and to institute learning processes on integrated nutrient management (INM). Participatory diagnosis of soil fertility constraints and experimental design workshops led to the formulation of the INM-FFS learning curriculum and choice of INM technologies for testing in the central learning plot. INM technologies jointly chosen for testing included farmyard manure (FYM = T1), diammonium phosphate (DAP = T2), combined application of FYM and DAP (T3); and T3 combined with Tithonia diversifolia applied as green manure (T4). Maize was used as a test crop. The treatments were replicated twice using a pair-wise design and data collected, bi-weekly, using the agroecosystem analysis (AESA) framework to aid learning and data analysis with farmers. Farmers' evaluation of the trials was conducted at the end of the study period using matrix scoring and ranking. Treatments with combined application of organic and inorganic materials had better agro-economic performance than sole application of either FYM or DAP (T4 > T3 > T2 and T1) and they had a high value cost ratio (VCR > 2). The technologies of T1 to T3 did not have a positive impact on either nitrogen or phosphorus balances. However, T4 resulted in a positive partial N balance. Farmers' evaluation corresponded well with the majority of the quantitative agro-economic analysis. The study showed that there is a potential to use FFS for INM technology development and testing by stimulating interactions, farmer learning and closer working relationships between farmers, research scientists, extension and the institutions that they represent.

Integrating Farmers' and Scientists' Knowledge in Participatory Soil Mapping and Management: A Case Study from Semi-Arid Eastern Kenya

Sustainable natural resources management, particularly soil management, requires integration of farmers', researchers' and other stakeholders' knowledge for enhanced rural development. A field stud...

Regional distribution of Lepidopteran stemborers and their parasitoids among wild grasses in the semi-arid eastern Kenya

(Received 25 April, 2001; accepted 5 March, 2002) ABSTRACT A survey was conducted in six agroecological zones (AEZs) in semi-arid eastern Kenya, in May, 1996, to identify the major wild host grasses (abundance > 70%) for stemborers in each zone. The grasses sampled were Pennisetum purpureum Schumach, P. trachyphyllum Pilg., Panicum maximum Jacq, Sorghum versicolor Anderss, Cenchrus ciliaris L. and Cyperus sp. Among these grasses, P. purpureum was the most widespread and abundant. The survey was followed by an on-farm study conducted in each of the six AEZs to determine the relative abundance and distribution of stemborers, that infested the major wild grasses and their parasitoids . This was done by destructive sampling of 100 tillers, at a three-month interval, from July 1997 to April 1998. The stemborers that infested the grasses were Chilo partellus Swinhoe and Sesamia calamistis Hampson. Among these, C. partellus was the predominant species, with the highest number being recovered on S. versicolor (94.6%). Parasitoids were only reared on S. versicolor, and these were Cotesia sesamiae (Cameron), C. flavipes Cameron, Chelonus curvimaculatus (Cameron), Pristomerus sp. and Norbanus sp., with C. flavipes causing the highest parasitism (13.6%). Results reveal that S. versicolor exhibited potential for use in the management of stemborers in maize, by acting as a and crop for C. flavipes, between cropping seasons. Key Words: Agroecological zones, Chilo partellus, Cotesia flavipes, Cotesia sesamiae, refuge, trap crop Resume Une reconnaissance a ete effectuee dans six zones agro-ecologiques de la region semi-aride du Kenya, en Mai 1996, en vue d'identifier les herbes sauvages dominantes (abundances > 70%) pouvant servir de pieges pour les destructeurs des tiges de mais. Les herbes echantillonnees etaient Pennisetum purpureum Schumach, P. Tranchyphyllum Pilg., Panicum maximum Jacq, Sorghum versicolor Anderss, Cenchrus ciliaris L. and Cyperus sp. La reconnaissance etait appuyee par une etude dans les fermes, dans chaque zone ecologique, pour determiner l'abondance relative et la distribution des destructeurs des tiges et leurs parasites envahissant les herbes dominantes. Pour ce faire, un echantillonnage destructif etait utilise. Cent tiges fraiches etaient coupees a trois mois d'interval, de Juillet 1997 en Avril 1998. Les destructeurs des tiges ayant attaque les plantes etaient Chilo partellus Swinhoe et Sesamia calamistis Hampson. Partellus etait l'espece la plus dominante. Partellus etait abondant sur le S. versicolor. Les parasites se cabraient uniquement sur S. versicolor, parmis eux, Cotesia sesamiae (Cameron), C. flavipes Cameron , Chalonus curvinaculatus (Cameron), Pristomerus sp. et Norbanus . Flavipes C. avait le plus taux de parasitisme (13.6%). Les resultats ont ainsi revele que S. versicolor a un potentiel de control sur les destructeurs de mais en agissant comme piege et refuge au C. flavipes durant les saisons de culture. Mots Cles: Zones agro-ecologiques, Chilo partellus, Cotesia flavipes, Cotesia sesamiae, refuge, plant piege (Af Crop Sci J 2002 Vol 10 No 2 pp183-194)

Farmers' perceptions of aspects of maize production systems and pests in semi-arid eastern Kenya: Factors influencing occurrence and control of stemborers

A farmer survey was conducted in six agro-ecological zones (AEZs) in semi-arid eastern Kenya to verify the socio-economic importance of maize, identify its pests and farmers' perceptions of the relative importance of the pests. We also determined some agronomic practices that may influence stemborer infestation and identified the stemborer control methods used. Pests reported included chafer grubs, stemborers, termites, 'red ants', yellow-necked spur fowls, squirrels, monkeys, porcupines, rats, wild pigs and storage insect pests. Their relative importance in each AEZ is discussed. The squirrel was the most widely distributed and important vertebrate pest of maize in the study AEZs. Stemborers infested maize in all the zones, and ranked first among insect pests in the Upper Midland zone 4 (UM4), Lower Midland zone 3 (LM3) and LM4, and second in LM5, but were unimportant in UM2. Agronomic practices that may influence stemborer infestation in maize, including cropping system, sowing time, fertilizer/manure use, stover storage usage and disposal and maize varieties are discussed. Most farmers preferred local to improved maize varieties, and maize was mostly grown as an intercrop. This emphasizes the need for more research effort to identify pests and develop pest management technologies in local maize varieties, contrary to the current research agenda which has focussed on improved varieties. Pest management technologies developed also should be compatible with intercropping before dissemination to farmers. Farmers use insecticides, wood ash, soil, saw dust, chilli pepper powder, dry cell powder and mexican marigold ( Tagetes minuta ) to control stemborers.

Associations between grain yield and carbon isotope discrimination in cowpea

Twenty cowpea ( Vigna unguiculata L. Walp.) genotypes, comprising Kenyan cultivars and Kenyan and introduced breedings lines, were grown in 15 replicated field trials carried out at three locations in semi-arid eastern Kenya over four seasons. Grain and straw yields and the carbon isotope discrimination (Δ) of this material were determined, and days to flowering and maturity observed. None of the seasons in which the trials were conducted was appreciably drier than the long term average for the sites, and some trials received excessive rain. Averaging the data for the 15 trials, one genotype yielded much less grain (77 g m −2) than the 19 others, whose yield ranged from 125 to 177 g m −2 (average 148 g m −2). Trial mean yield trials had a high straw Δ ( r = +0.567) and had received more rain between flowering and maturity ( r = +0.428) than lower yielding ones. Among genotypes, averaging over trials, the correlation coefficient ( r) between grain yield and grain Δ was +0.394, and between grain yield and straw Δ, +0.460. Early genotypes had the highest grain Δ and straw Δ. The correlation among genotypes between date of flowering and grain Δ was −0.632 and with straw Δ, −0.502. When comparisons were made among trials, there was no clear relationship between the strength of the correlations among genotypes between grain yield and straw Δ or grain Δ and the degree of stress experienced by a trial (as indicated by the rainfall it had received). It appeared that this was because the variances of grain Δ and straw Δ were greater in the most droughted trials, whereas the variance of yield was greatest in the least droughted trials. It is concluded that the genetic correlation between grain yield and either grain Δ or straw Δ is unlikely to be strong enough to make either Δ a useful surrogate or adjunct in selecting for high yield in the segregating generations of a breeding programme for semi-arid eastern Kenya, but that Δ may be of value in the selection of parent genotypes.

The Use of Manure on Smallholders' Farms in Semi-Arid Eastern Kenya

SummaryThe manure that is returned to croplands each year is an important resource in the subsistence farming systems of eastern Kenya. Measurements on several farms have shown that the manure being used is of very poor quality. Analyses of soil samples from beneath the bomas (small enclosures) where animals are kept indicate that substantial losses of nutrients occur through leaching; ammonia volatilization and denitrification may also be involved. Current practice is to apply the manure at rates that appear to make poor use of this scarce resource. The findings are discussed in terms of what changes to the system may be feasible to reduce losses of nutrients, and to improve the quality of the manure and the effectiveness of its use.

Effects of Temperature, Soil Water Status and Depth of Planting on Germination and Emergence of Maize (Zea Mays) Adapted to Semi-Arid Eastern Kenya

SUMMARYThe effects of temperature and soil water potential on maize germination were investigated in controlled environment conditions and the effects of depth of planting and a mulch on maize emergence were studied in a field experiment in eastern Kenya. The rate of germination increased to an optimum temperature of 33.6°C above a base temperature of 6.1°C and decreased above the optimum to zero germination at 42.9°C. The thermal time for median germination increased from 51.5°Cd to 56.4°Cd as soil matric potential decreased from -5 to -40 kPa. Soil water content, depth of planting, and their interaction had significant (P < 0.001) effects on final germination and emergence but mulch, or any interactions involving mulch, had no such effects. Increasing depth of planting by 1 cm increased the thermal time required for emergence by 2.8°Cd, and decreasing water content by 1% increased the thermal time required for emergence by 3.2°Cd.Germinación y emergencia del maíz