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Integrated Nutrient Management, Soil Fertility and Productivity of Maize (Zea mays l.) in a Derived Savanna Ultisol of Southeastern Nigeria
The response of maize to different rates of NPK 15:15:15 compound fertilizer under basal application of rice-husk ash (RHA) was evaluated in a two-year field experiments in 2009 and 2010. The RHA at 4 t ha-1 was incorporated into the soil before the application of 0, 100, 200, 300 and 400 kg ha-1 NPK. The RHA contains 64.00 g kg-1 Ca, 12.20 g kg-1 Mg, 12.50 g kg-1 P, 9.00 g kg-1 K, 2.10 g kg-1 N, 1.23 g kg-1 Organic carbon and had a pH of 10.86. Treatments were fitted in a randomized complete block design (RCBD) replicated three times. Analysis of variance (ANOVA) indicated no significant treatment effects at P = 0.05 on soil pH, Ca, P and K except for soil total N. Curve estimations show values of R2 = 0.892** for soil total N and R2 = 0.874** for grain yield of maize. Significant increase (P < 0.01) in soil total N status from 0.065 % in the control (0 kg ha-1) plots to 0.23 % at 400 kg ha-1 NPK fertilizer relate to the patterns of growth and grain yield of maize test crop. The application of 200 kg ha-1 NPK gave grain yield of 3016.67 kg ha-1 when compared with 1755.55 kg and 1944.44 kg ha-1 obtained, respectively in the control and 100 kg ha-1 NPK. Grain yield at 300 and 400 kg ha-1 NPK were not significant (P = 0.05) when compared with that at 200 kg ha-1. The application of 200 kg ha-1 NPK tended to be cost effective.