Maize (Zea mays) response to nitrogen fertiliser on an ultisol in southern nigeria under two tillage and mulch treatments

Abstract

AbstractThe response of maize to four rates of nitrogen (N) fertiliser (0, 60, 120 and 240 kg N ha−1) on an ultisol in south‐eastern Nigeria was evaluated under two tillage and two mulch treatments. Differences in plant height, leaf area index and grain yield between the conventionally tilled and zero‐tillage treatments were not significant at P < 0.05, but the mulched plots out‐yielded the unmulched plots by 23–46% during the drier seasons. On each tillage‐mulch combination, grain yield response to nitrogen was of a quadratic polynomial form, indicating that maximum yields occurred at 123, 139, 130 and 142 kg N ha−1 on the tilled‐mulched, tilled‐unmulched, untilled‐mulched and untilled‐unmulched plots, respectively. Nitrogen use efficiency (grain yield per kg N applied) decreased in the order tilled‐mulched (32.6) > untilled‐mulched (30.9) > untilled‐unmulched (27.8) > tilled‐unmulched (22.4) where the figures in parentheses represent nitrogen use efficiency (kg kg−1).For each tillage treatment maximum soil temperature was higher and moisture retained at 2 and 10 days after saturation lower on the unmulched than mulched plots. Percentage moisture loss between these days was 45.5, 83.3, 25.0 and 55.6 respectively, on the tilled‐mulched, tilled‐unmulched, untilled‐mulched and untilled‐unmulched plots. The untilled‐mulched plots had the highest contents of residual organic carbon and total N.