Appraisal of some nitrogen indices for predicting nitrogen need of maize

Abstract

Field experiments were conducted for two years on 20 farmers' fields to appraise some N forms as indices for predicting N need of maize crop in some southwestern Nigeria soils. The total-N organic-N, exch. NH₄, fixed-NH₄ and NO₃-N in the 0-20 cm depth ranged from 300-1400, 249-1197, 10-62, 15-122 and 9-42 mg kg^-1 respectively. All the N forms are significantly related to soil organic matter. Although all the N forms gave positive and significant relationships with relative yield, the most important predictor variable was NO₃ –N in 0-45cm soil depth (R²=0.94). The critical level of the residual NO₃ within this soil depth was established at 46.0 mg kg^-1. Six of the sites fell within high N class while the other 14 sites fall within low N class. The probability of obtaining response to N application is higher in the latter than in the former sites.

Nigerian Journal of Soil Science Vol. 15 2005: 123-128