The objective of this research was to evaluate the corn yield on nitrogen fertilizer levels, verifying soil fertility changes and Crotalaria and Canavalia residues decomposition which were cultivated before corn cultivation. The experiment was carried out in 2003/2004 agricultural year in Gurupi Universitary Campus of Federal University of Tocantins, on a split -plot randomized blocks scheme with four repetitions. In plots were cultivated Crotalaria juncea or Canavalia ensiformis, and in split-plots were tested nitrogen level requirements to corn: 0, 50, 100, 150, 200 e 250kg ha-1. Independently of N levels were observed that Crotalaria cultural residues decomposed with higher rate when compared with Canavalia residues, which contributed to better corn grain yield with its residues because higher decomposition rate. The highest corn productivity (9444kg ha-1) was obtained with 100kg ha-1 of N fertilizer with Crotalaria straw residues, while almost the same (9074kg ha-1) was only obtained with 250kg ha-1 with Canavalia residues. After corn harvesting, there was an increase on organic matter levels on Crotalaria residues, an increase on P levels on Canavalia residues, and with any legume residues, an increase on Ca+Mg exchangeable levels.
residues decomposition; cover crops
