DETERMINING QUANTITY OF COWPEA (Vigna unguiculata) LEAF YIELD UNDER DIFFERENT MANURE APPLICATION REGIMES AND CROPPING SYSTEMS IN WESTERN KENYA

Abstract

The low production of cereals and legumes among small-scale farmers in Kenya attributed to declining soil fertility and poor agronomic practices has led to renewed interest to review existing crop improvement technologies. Such technologies if applied appropriately can lead to crop yield improvement. The study was conducted among members of three farmer associations: MFAGRO (Vihiga), BUSSFFO (Bungoma) and AFDEP (Teso) in western Kenya, during the short rain season (SRS) and long rain season (LRS) of the year 2011 and 2012 respectively. The experiment aimed at studying factors affecting technology uptake among small-scale farmers. It also evaluated effect of fortified organic manure on leaf yield of cowpea grown under different cropping systems. The experimental design was split-split plot in a Randomized Complete Block Design (RCBD) with three replications per cropping zone (site). Two levels of organic manure: 0 t ha-1 and 5 t ha-1 (season one): 0 t ha -1 and 2.5 t ha -1 (season two) were randomized in the main plots. Three cropping systems: monocrop, conventional and Managing Beneficial Interaction in Legume Intercrops (MBILI) in the sub plots while two cowpea (Ken kunde, and Black eye) and two maize (Hybrid 513 and WS 303) varieties in the sub- sub plots. Topsoil (0-15 cm depth) was sampled and analysed for physical and chemical properties (pH, N, OC and P) before planting and after harvesting. Similarly, pH, N, and P of the organic manure were also analysed before fortification. Results showed that leaves of Ken kunde grown with fortified manure were vigorous and had a significantly high (p < 0.001) leaf yield across all sites. Fortification of manure increased the levels of phosphorus and nitrogen available to the cowpea crop hence promoting growth of longer shoots, numerous, and larger leaves resulting in high leaf yield. Teso recorded (2.3 t ha-1), Bungoma (1.9 t ha-1) and Vihiga (1.8 t ha-1) of total leaf yield. The least leaf yield (0.1 t ha-1) was recorded in Black eye variety grown without manure in Vihiga. A significant difference (p < 0.01) in leaf yield was also observed in cowpea grown under different cropping systems. Ken-kunde grown in monocrop system recorded 1.9 t ha- (Teso), 1.3 t ha-1 (Vihiga) and 1.5 t ha-1 (Bungoma). Ken-kunde grown in MBILI system recorded 1.7 t ha- (Teso), 1.0 t ha-1 (Vihiga) and 1.2 t ha-1 (Bungoma).Same variety in conventional system recorded 0.9 t/ha (Teso), 0.7 t ha-1 (Vihiga) and 0.8 t ha-1 (Bungoma). Though Ken-kunde performed better while grown with fortified manure in monocrop system due to reduced competition, growing it with fortified manure in MBILI system was most appropriate to the small-scale farmer, because of farm size limitations and economies of scale associated with intercropping. The combination was recommended to farmers for adoption with an aim at improving cowpea leaf yield and associated income . The results also revealed that some of the factors that influenced adoption of technology and its intensity among small scale farmers included, site (county) where the farmer resided, know-how on value addition, knowledge on the technology, availability of inputs, age of household head and membership to a farmer association. It was also noted that ability of such farmers to identify farming related problems and solutions required strengthening through capacity building. The community action research approach was therefore effectively used to engage farmers through all the project phases thus increased their level of project ownership, technology adoption, adaptation and dissemination.