Effect of Organic and Inorganic Fertilisers on Maize and Traditional Vegetable Yields in Kisii Highlands

ABSTRACT One of the major problems facing resource-poor small-scale farmers producing maize and traditional vegetables in Kenya is a decline in soil fertility. During participatory rural appraisal (PRA) exercises undertaken in Bogetaorio village, Nyamira District, Kenya, farmers attributed low yields of maize and traditional vegetables to declining soil fertility as a result of continuous cropping, burning of crop residues and soil erosion. The PRA further showed that farmers in the region applied low quantities of organic and inorganic fertilisers because of their high costs. A study was therefore started during the Short Rains of 1995 to address the problem of low crop production by improving soil fertility. The objectives of this study were to determine: 1) the effect of both organic and inorganic fertilisers on yield of maize and traditional vegetables and 2) low cost fertilisers for recommendation to farmers in the study area. The treatments varied according to test crops and included varying rates of farm yard manure (FYM) combined with inorganic fertiliser. Application of organic/inorganic fertiliser treatment combinations significntly increased soil nutrient status over the experimental period. The level of soil P, Ca, and K increased by over 70%. The fertiliser treatment combinations generally gave similar yields to the recommended rate of inorganic P and N fertilisers and gave higher yields than FYM/compost treatments alone. In 1998, the combination treatments of 10 t/ha compost + 15 kg P2O5/ha + 15 kg N/hagave a maize yield of 7.8 t/ha, which was significantly higher (P<0.05) than yields from the other treatments and was within the range of potential maize yield (7.2–9.0 t/ha) in the region. The fertiliser treatment combinations also increased yield of traditional vegetables significantly (P=0.05) compared to FYM applied alone. Thus, a combination of organic and reduced rates of inorganic fertilisers may be a promising low cost option to the use of the recommended rate of inorganic fertiliser for maize and vegetable production.