Using farmer-prioritized vertisol management options for enhanced green gram and tomato production in central Kenya

Abstract

Green gram (Phaseolus aures L.) and tomato (Solanum lycopersicum L) are widely grown in the vertisols of the Mwea Irrigation Scheme in Kenya alongside the rice fields. Green gram can fix nitrogen and is grown for its highly nutritious and curative seeds while tomato is grown for its fruit rich in fiber, minerals and vitamins. The two can be prepared individually or together in a variety of ways including raw salads and/or cooked/fried. They together form significant delicacies consumed with rice, which is the major cash crop grown in the black cotton soils. The crops can grow well in warm conditions but tomato is fairly adaptable except under excessive humidity and temperatures that reduce yields. Socio-economic prioritization by the farming community and on-farm demonstrations of soil management options were instituted to demonstrate enhanced green gram and tomato production in vertisol soils of lower parts of Kirinyaga County (Mwea East and Mwea West districts). Drainage management was recognized by the farming community as the best option although a reduced number of farmers used drainage and furrows/ridges, manure, fertilizer and shifting options in that descending order. Non-availability of labour and/or financial cost for instituting these management options were indicated as major hindrances to adoption of the yield enhancing options. Labour force was contributed to mainly by the family alongside hiring (64.2%) although 28% and 5.2%, respectively used hired or family labour alone. The female role in farming activities dominated while the male role was minimal especially at weeding. The youth role was insignificant and altogether absent at marketing. Despite the need for labour at earlier activities (especially when soil management options needed to be instituted) it was at the marketing stage that this force was directed. Soils were considered infertile by 60% but 40% indicated that their farms had adequate fertility. Analysis showed that with ridging, farm yard manure and fertilizer improved soil fertility, crop growth and income considerably. Phosphate and zinc enhancement reduced alkalinity and sodicity. Green gram and tomato yields increased under ridges and farm yard manure application by between 17-25% which significantly enhanced household incomes.

Key words: Green gram, Tomato, Vertisol management, Household income, Mwea, Kenya