Sustainable intensification promotes environmentally sound and productive agriculture. However, use of sustainable intensification practices (SIPs) is low in many sub-Sharan African countries. This study examined the adoption of SIPs in Kenyan rural and peri-urban vegetable production to understand the scale of and underlying factors in the use of SIPs. A multistage sampling technique was employed to randomly select 685 rural and peri-urban vegetable farm households. Household data was then collected and anaylsed for four practices namely improved irrigation, integrated soil fertility, organic manure and crop diversification using a pre-tested structured questionnaire. A multivariate probit model was run to model simultaneous interdependent adoption decisions. Adoption of organic manure and African indigenous vegetables (AIV) diversification was high in both rural and peri-urban areas. However, adoption of improved irrigation systems and integrated soil fertility management was low, and even significantly lower in rural areas than in peri-urban areas (p < 0.041). Similarly, adoption intensity of SIPs was lower in rural areas than in peri-urban areas. Furthermore, the findings also show complementarities and substitutabilities between SIPs. Market integration, the farm location and household income were the major factors heavily influencing the adoption of most SIPs. Policies and programmes that seek to build household financial capital base and integrate farm households into effective and efficient vegetable markets need to be formulated and implemented in order to enhance adoption of SIPs in AIV production.

High fertiliser costs and declining soil fertility are'among the key factors contributing to low crop yields in Kenya. The contribution of five legumes grown in the short-rains season to soil nitrogen status and performance of a succeeding maize (Zea mays L.) was studied in an experiment at Njoro and Rongai within the Rift Valley Highlands of Kenya, from 1997 to 1999. Treatments included a weedy fallow, five grain legumes and maize (H513) grown during short-rains season followed by maize in the April-August long-rains season. The legumes were chickpea (Cicer arietinum L.), field bean (Phaseolus vulgaris L.), soybean [Glycine max(L.) Merril], garden pea (Pisum sativum L.), dolichos [Lablab purpureus (L.) Sweet]. The crop residues and vegetation of the weedy fallow were incorporated in the soil during seedbed preparation for the long rains season. The maize test crop was supplied with three levels of nitrogen, 0,30, and 60 kg ha-' as main factor whilst fallow management options were allocated as sub-factors in a split-plot treatment arrangement of a randomised complete block design replicated three times. Results show improved soil N status following legumes, with dolichos giving highest available N. Grain yield in maize succeeding legumes was 2468% higher than maize succeeding weed fallow. In the absence of N fertiliser input, maize succeeding dolichos gave 20-40% higher yield than maize after weed fallow treated with recommended 60 kg N ha-' fertiliser rate. The study has demonstrated that the use of grain legumes, particularly dolichos in rotation with maize, is a viable and preferable option to weedy fallows and maize-maize sequences.

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 Rongai, respectively, in the succeeding cereal against preceding traditional fallow. The perennial weeds, which included Digitaria scalarum, Pennisetum clandestinum and Conyza sp., were substantially reduced in the managed fallow. Legume-managed fallow significantly improved soil nitrogen status and the yield of the following cereals. Grain yield in managed fallow increased on average by about 39 and 17% over locations in maize and wheat, respectively. Despite yielding less soil-incorporated residue, the impact of legumes was greater than that of the traditional fallow yielding large amount of organic material. Among the legume species, dolichos showed outstanding positive effect on succeeding cereal crop, probably due to increased soil nitrate levels. Field bean and chickpea have a potential seed advantage, although the latter is susceptible to 100% loss by Helicoverpa armigera. Hence, managing the traditional short-rains fallow with legumes could reduce weed infestation, in addition to improving soil nitrogen for subsequent crops.

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(NO 3 ) 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(NO 3 ) 2 100 g extracted significantly more K and Na in the leachate than Ca(NO 3 ) 2 0.0 g and 60 g. The EC levels in the leachate increased with the application levels of Ca(NO 3 ) 2 while the pH levels were reducing. In the treated cocopeat, Ca(NO 3 ) 2 100 g and soaking duration 36 hours significantly reduced K and Na and sufficiently supplemented Ca and N. Irrespective of Ca(NO 3 ) 2 and soaking durations, after the cocopeat is washed, the EC and pH values fall within their suitable ranges. There was a strong negative correlation between Ca and Na, Ca and K, and between Na and EC. Also, strong positive correlation between Ca and N and Ca and EC. Effective supplementation of Ca and N, and optimal reduction of K and Na by 78.44% and 92%, respectively can be achieved with 100 g of Ca(NO 3 ) 2 1.5 kg −1 of cocopeat in 15 liters of water with a soaking duration of 36 hours.

Grain sorghum (Sorghum bicolor) has a great potential for use as food and beverage in developing countries. However, information regarding the effect of the agro-ecological environments on the grain quality attributes of selected sorghum lines desirable for malting and brewing and for baking in Kenya, is lacking. The experiments of this study were conducted at different environmental locations in Kisumu, Siaya and Busia Counties of Kenya. Nine sorghum lines were sown in plots in Randomized Complete Block Design (RCBD) and replicated three times. Panicles from two central rows of each plot were harvested at physiological maturity to provide grains that were used for proximate analysis. The percentage crude protein, tannin and starch content were determined. The amount of starch varied with sorghum lines and growing environments, ranging between 29.7 and 80.2%. SDSAI × ICSR43 line recorded tannin content in the range of 8.00 to 24.33 mg/100 ml tannic acid equivalents. Crude protein content and starch ranged 8.9 to 15.4% and 29.7 to 80.2%, respectively across environments. The combined analysis showed that the growing environment variously affected the nutritional and antinutritional content of sorghum lines. This implies that breeders should consider stability of the quality parameters that define commercial utilization of these sorghum lines.