Nitrogen management in maize in no-till system in succession to winter cover crops at two locations: II - effect on grain yield

摘要

The release of nitrogen (N) of crop residues depends on the processes of microbial immobilization and mineralization, which are influenced by environment. The objective of this study was to evaluate, at two locations, the effects of rate and timing of N application in maize (0-0; 0-160; 30-130 and 60-100kg/ha, respectively, at sowing and sidedressed), in no-till system, established in two sowing dates after desiccation (1 and 20 days) of two winter cover crops (black oat and common vetch) and bare area, on grain yield. The experiment was conducted at two locations of the state of Rio Grande do Sul, Brazil, in the 1996/97 growing season. Maize response to N application depended on the location, on the specie of winter cover crop used and on sowing date after desiccation. In Eldorado do Sul, N application at sowing increased grain yield in relation to the treatment with total N sidedressed. At Passo Fundo there were no differences among the treatments with N application. The increase of the N rate from 30 to 60kg/ha at sowing date did not affect grain yield of maize, regardless of the other treatments used. The delay in 20 days of maize sowing date in succession to black oat was benefitial only in Eldorado do Sul, with 34% of increase of the grain yield.