Effect of farmyard manure and inorganic fertilizers on maize production on Alfisols and Ultisols in Kakamega, western Kenya.

Abstract

Soil acidity is one property associated with decline of most crop productivity. Alfisols and Ultisols are some of the acidic soils predominant in western Kenya. An experiment was conducted in both soils to find out the effect of farmyard manure (FYM) and inorganic fertilizers on maize yield on farmers' fields during wet and dry seasons of 2006. The experiment, laid out in a randomized complete block design (RCBD), had five replications in each soil type. The treatments were: farmer's practice, N (60 kg ha-1), NP (60 kg ha-1 of each), NPK (60 kg ha-1 of each N and P; K 40 kg ha-1), FYM+30 kg N ha-1, and optimal fertilizer (N, 200; P, 60; K, 120; Mg, 20; B, 5 kg ha-1). During wet season, all treatments in Alfisols gave nearly double grain yield compared to Ultisols. In both soils, during the same season, except for optimal fertilizer, FYM was not significantly (P≤0.05) different from other inorganic fertilizer treatments on plant population, height, cob number, stover, grain yield and 100-seed weight. FYM had a 108% and 103% grain yield advantage over farmer's treatment in Alfisols and Ultisols, respectively. During dry season, plant population, number of cobs and grain yield were higher in Ultisols compared to Alfisols. In each soil type, FYM plus 30 kg N ha-1 provided maize grain yield equivalent to that of N, NP and NPK treatments. FYM had a 4% grain yield advantage over optimal and NPK treatments on Ultisols during dry season. We conclude that larger amount of fertilizers or liming is needed on Ultisols to enhance their productivity to the level of Alfisols and that due to the fact that smallholder farmers are not likely to afford large amount of fertilizer and liming, use of FYM is their best bet for maize production on both Alfisols and Ultisols as there is no significant yield advantage from N, NP or NPK over FYM. Ultisols appear to be more responsive to FYM during dry season probably due to prevailing higher temperatures and relatively dry soil which enhances faster mineralization of organic matter to available plant nutrients. Addition of N fertilizer failed to increase yield in Ultisols, probably due to decline in soil pH and consequently inefficient utilization of applied resources.