Plantas de cobertura de inverno em sistemas de produção de milho sob plantio direto no sudoeste do Paraná

Abstract

The tillage system was a great advancement for the Brazilian agriculture, promoting benefits by maintaining crop residue on the soil surface. However, there is an predominance in the use of oat cover crop of winter, preceding summer commercial crops. Despite providing the input of large amounts of waste, this species is not preferred due to the high C: N ratio, to precede the cultivation of corn, crop that occupies large areas of crops in the southwest region of Paraná. This work aimed to evaluate the effect of different ground cover plants, preceding corn crop in the presence and absence of nitrogen fertilizer, no-till, soil and climatic conditions in the Southwestern region of Paraná. An experiment was conducted with accompaniment during two years (2010/2011 and 2011/2012) in the experimental area of the Universidade Tecnológica Federal do Paraná, Campus Dois Vizinhos. The experimental design was a randomized block, split plot design with three replications. The main plots consisted of eight soil cover crops, which were: black oat, ryegrass, rye, vetch common, white lupins, forage turnip and consortium among Oat+Vetch (O+V) and Oat+Vetch+Turnip (O+V+T) and subplots, with two levels of nitrogen fertilization (0 and 180 kg N ha-1) in the corn crop. Evaluations were made regarding the development, production, decomposition and liberation N by dry matter (DM) of cover crops. In corn, beyond agronomic traits were evaluated in the total N present in biomass, flag leaf and in the grain. In the soil, there were evaluations and monitoring of respiratory activity of inorganic N (N-NH4 + and N-NO3-) released during decomposition of residues. Was found in the 2010/2011 season that the C:N ratio systems containing single legumes were statistically lower than pure grasses. The highest rate of waste decomposition occurred with the isolated use of vetch. However, both of legumes provided greater release of N. The use of mineral Nfertilization in corn, promoted higher yield, with no influence of cover crops. For the 2011/2012 season, there was the highest DM yield with the use of oat (4.7 Mg ha-¹) not differing from the other grasses and consortium. The lowest rate of decomposition occurred with the use of oats, in isolated culture. The consortium O+V+T presented the second highest N release, behind only the common vetch. Legumes and brassicas (turnip), isolated in cultures without addition of mineral N, provide yield similar addition of 180 kg N ha-¹ in coverage.