Abstract

Low purchasing power of inorganic fertilizers by farmers among other factors has led to a decrease in maize production in Kenya. Growing trees on-farm can improve the situation. A study was carried out at three sites in Western Kenya to investigate the effects of selected tree species on total organic carbon, cation exchange capacity, pH, growth and yield of maize. Top soil (0 to 15cm) and maize plants were sampled for measurements under the canopies of selected tree species at (2, 7 and 12 m) from trees. A complete randomized block design with four tree species, three levels of distance and three stages of growth was used. Soils under Grevillea robusta had a significantly higher pH (p=0.02) at Ulafu. Soil CEC under G. robusta and Leuceana leucocephalla were significantly lower (p< 0.001) compared to Markhamia lutea and Mangifera indica at Ulafu. Maize under G. robusta at Bumula had the highest yield (3.91 t ha^-1). A significantly lower (p=0.001) maize yield was revealed under M indica in both Ulafu and Ndere. The study suggests some positive influences from all the trees by increasing total organic carbon in soils. Therefore, increasing the number of trees on farms may improve soil fertility and maize production.

Key words: Soil pH, total organic carbon, cation exchange capacity, tree species, maize growth and yield.