| Abstract: | Effects of a tillage-surface crop residue combination on nitrogen (N) accumulation by maize were examined using a replicated field experiment. Crop residues, < 70 % surface cover, were applied a few days aftei planting conventional- and ridge-tillage treatments. With < 30 % surface cover, total accumulated-N decreased from about 4 to 2 g plant?1 as the plant population density (PPD) increased from 4 to 7 plants m?2 With < 70 % surface cover, total N accumulated averaged about 3 g plant?1 over the PPD range of 4 to / plants m?1. At a PPD of about 5.5 plants m?2, equal amounts of N were accumulated by plants in al treatments. Nitrogen accumulation was periodically monitored and fitted to a diphasic tanh(ktime]) model About 1.8 to 2.6 g of N and about 0.70 to 1.4 g of N were accumulated before and after anthesis respectively. Maximum N accumulation rates averaged about 92 and 60 mg plant?1 day?1 during vegetativt and reproductive growth-stages, respectively. Total N accumulation during the vegetative growth-stag declined exponentially as PPD increased; this may reflect a crop demand-soil supply relationship. |
