This work aimed to quantify the available nitrogen (N) to a maize crop and evaluate its effects on leaf area index (LAI), shoot dry matter (SDM) production, N absorption by the above ground biomass, and grain yield. The evaluations were performed in a soil management experiment run since 1985, with three cropping systems (oat - Avena strigosa/maize, oat + vetch - Vicia sativa/maize and oat + vetch/maize + cowpea - Vigna unguiculata) and two rates of nitrogen (0 and 180 kg ha-1) applied to maize. In the 2000/2001 cropping year, four nitrogen rates were applied (0, 60, 120 and 180 kg ha-1). The estimated available N to the maize calculated from the contribution from the soil, cover crops and N fertilizer varied from 27 to 192 kg ha-1. All evaluated variables presented high dependence on available N, and reached its maximum level near to the highest level of available N (192 kg ha-1). With this level of availability, at the stage of pollination, the largest values of LAI (4.41) and the highest leaf N concentration were observed, however, the highest N accumulation in the above ground biomass was observed at the milk grain stage and the shoot dry matter accumulation at the dent stage. The maximum grain yield obtained was 8,920 kg ha-1, corresponding to 112 kg ha-1 of exported N by the grain.
cropping systems; leaf area index; shoot dry matter; biomass nitrogen concentration; Zea mays L
