Teor de n-mineral no solo e produtividade do milho sob plantas de cobertura em plantio direto

Abstract

Among the several limiting factors to maize productivity, it is worth noting the incorrect handling of nitrogen (N), since it is one of the nutrients that has the most influence on grain yield and which most costs production costs. In order to increase the sustainability of production systems, it is necessary to understand the dynamics of this nutrient in the production system and to consider the contribution of the coverage systems that precede the commercial crop to define the need for nitrogen fertilization. The objective of this study was to evaluate the effect of different winter cover crops on the availability of mineral N in the soil during the development of corn cultivation in the presence and absence of nitrogen fertilization in no-tillage in a dystroferric Red Nitosol under the conditions Of the southwestern region of Paraná. The experimental design was a randomized block design, in split plot, with three replications. The main plots consisted of eight soil cover systems: black oat, ryegrass, rye, vetch common, blue Lupins, forage turnip and consortium among Oat+Vetch (O+V) and Oat+Vetch+Turnip (O+V+T) and subplots, two, with two levels of nitrogen fertilization (0 and 180 kg N ha-1) in the corn crop. Evaluations were made regarding the production, decomposition and release of N by the dry matter of the cover plants. In the soil was evaluated the availability of mineral during the decomposition of the residues of the cover plants. Maize was evaluated as yield components, relative chlorophyll content in leaves and grain yield. O+V and O+V+T consortia presented total accumulated DM and N production equivalent to the use of oats and rye in a single form, intermediate C / N ratio, N release equivalent to the use of uniquely cultivated vetch, allied The greater protection of the soil to the logo of the 120 days of evaluation. The availability of nitric and ammoniacal N in the soil is greater the lower the C/N ratio of the cover systems analyzed. The need for nitrogen fertilization for maize crop considering the contribution of each cover system in the N supply, using the spad index readings for calculation is: vetch: 0 kg N ha-1, lupine: 63 kg N ha-1; O+V+T: 65 kg N ha-1; Turnip: 95 kg N ha-1; O+V: 104 kg N ha-1; Rye: 149 kg N ha-1; Ryegrass: oats 150 kg N ha-1; 180 kg N ha-1. The cultivation of corn without nitrogen fertilization after vetch, turnip and O+V+T consortium, yield productivity similar to that obtained with the 180 kg ha-1. The yield of maize that received nitrogen fertilization in succession to the ryegrass, rye, turnip and O+V+T systems (6.4 Mg ha- 1), presented a lower productivity of 2.3 Mg ha-1compared to systems with vetchLupine, and A+E.