MULCHING EFFECT OF PLANT RESIDUES WITH CHEMICALLY CONTRASTING COMPOSITIONS ON MAIZE GROWTH AND NUTRIENTS ACCUMULATION

Effects of application of prunings of three woody species (Acioa barte ri, Gliricidia sepium and Leucaena leucocephala), maize (Zea mays L.) stover and rice (Oryza sativa L.) straw as mulch on maize were studied on an Alfisol in southern Nigeria in 1990 and 1991. Maize dry matter and grain yield were higher with applications of plant residues and N fertilizer in both years. Addition of Leucaena prunings gave the highe st maize grain yield in both years. Compared to the 1990 results, Acio a showed the least grain yield decline among the mulch treatments in 1 991. Nutrient uptake was enhanced by applications of plant residues. L eucaena prunings had the highest effect in both years and increased th e mean N, P, and Mg uptake by 96%, 84%, and 50%, respectively, over th e control. Addition of Acioa prunings increased K and Ca uptake by 59% and 92%, respectively, over the control. 'High quality' (low CIN rati o and lignin level) plant residues enhance crop performance through di rect nutritional contributions, whereas 'low quality' (high C/N ratio and lignin level) plant residues do so through mulching effects on the microclimate. 'Intermediate quality' plant residues have no clear eff ects on crop performance.