Organic residue management, soil nutrient changes and maize yield in a humid Ultisol

Abstract

A study was conducted on an Oxic Paleudult in South Western Nigeria to evaluate the effects of organic residue treatments after clearing a 3 year secondary fallow land on soil nutrients, maize yield and profitability. Burning of the fallow residue in 1993 and crop residue in situ in 1994 led to significant increases in soil pH, total N, organic matter, available P, exchangeable Ca, Mg and K within one month in both fertilized and unfertilized treatments. However, the increases were not sustained till harvest and in most cases the concentrations of the nutrients decreased significantly below the pretreatment levels. Increases due to residue incorporation were small but more sustainable, while in bare unfertilized plots the nutrients decreased below the pre treatment levels throughout the period of the experiment. Maize yields were significantly higher in residue incorporated and burnt plots than in the bare plots with or without fertilizer application in both years. The influence of fertilizer application was profound. However, residue incorporation without fertilizer produced 84% of the yield obtained in bare fertilized plots in 1993 and as much as 104% in 1994. The highest profit was obtained when fertilizer application was combined with residue incorporation.