Effect of fertilizer on microbial decomposition of leaf litter of a regenerating bush-fallow in sub-humid tropical Nigeria

Abstract

A 5-month study of the effects of urea and NPK-mixtures on microbial litter decomposition process was carried out on the leaf litter of a regenerating secondary forest at Ile-Ife, Nigeria. The litter was treated with urea and an NPK-mixture separately at three levels of concentrations calculated on the basis of the fertilizers. Addition of urea and an NPK-mixture at 5, 10 and 15 mg g −1 air-dried litter increased microbial population, activity and the rate of decomposition of litter as compared with the control. In the case of the NPK-mixture, the increase was more pronounced as the concentration increased, but in the case of urea, the increasing trend was reversed after two months, even though bacterial population maintained a steady increase. The nutrient element dynamics of decomposing leaf litter in relation to fertilizer treatment was examined. N, P and Mg concentrations in leaf litter declined in the first two months of sampling. However, N and P remained relatively constant despite about 30% loss in weight of leaf litter during subsequent sampling periods. The rate of loss of Mg was somewhat faster than that of the organic matter. K and Ca showed marked contrasts both with N, P and Mg and with one another.