Effects of legumes on soil nitrogen, yield and nitrogen use efficiency of succeeding maize in Guinea savanna alfisol, Nigeria

Abstract

Nitrogen (N) is a major nutrient limiting maize production in the Guinea savanna of Nigeria due to the inherently poor N status of the soils. The problem is further exacerbated by the non-availability, and when available, expensive nature of inorganic N fertilizers. This study determined the effects of soybean, cowpea, Centrosema pascuourum and a natural fallow on the soil N status, grain yield and nitrogen use efficiency (NUE) of a succeeding maize crop. In the first season, the legumes and fallow plots were established and the legumes grown to maturity. In the second season, maize was planted with different N fertilizer rates of 0, 20, 40 and 60 kg N ha^-1 each combined with two residue managements incorporation and removal. The experimental design was a split-plot arrangement fitted to a randomized complete block with the legumes and fallow as the main plot and combined nitrogen fertilizer and residue management as subplots. The incorporation of legumes residue significantly (P<0.05) increased the soil inorganic N. There was a significant (P<0.05) positive response to previous legumes and fallow by following maize. Maize succeeding the legumes had higher grain and stover yield than maize after fallow. Across all the previous legumes and fallow, there was a significant (P<0.05) positive response to combined N fertilizer and residue management by following maize. Residue incorporation combined with application of 60 kg N ha^-1 had the highest grain, (5167 kg ha^-1) and stover, (5077 kg ha^-1) yields. Among all the treatments, the greatest grain yield of 8501 kg ha^-1 was obtained from the maize grown after soybean with combined 20 kg N ha-1and residue incorporation. Maize after legumes was more efficient in N use than those after fallow. Maize was more efficient in N use when rotated with legumes at low rate of inorganic N fertilizer application.

Keywords: nitrogen use efficiency, legumes, moist savanna.

Nigeria Journal of Soil Research Vol. 6 2005: 9-21