Sistemas de produção com aporte de palha e nitrogênio sobre atributos do solo e desempenho da soja no Oeste Paulista

Abstract

The production and quality of the straw deposited on the soil is a prime factor to enable soybean cultivation in regions of sandy soils with high risk of water deficit. The objective of this work was to evaluate the no-tillage effect with differentiated straw and nitrogen input before soybean cultivation, aiming at improvements in the physical and organic matter properties of the soil and increase in soybean yield. The experiment was carried out in an experimental area of the Western São Paulo University - UNOESTE, in Presidente Prudente-SP, in the agricultural years 2014/2015 and 2015 / 2016. The experimental design was a randomized complete block design, with four replications, in a subdivided plots scheme, with four replications. The plots consisted of three crop rotations, I) corn / lupine / soybean, II) corn + palisade grass / soybean, III) palisade grass / soybean, and the subplots by four doses of N, 50, 100, 150 and 200 kg ha-1 applied annually. Were evaluated: amount of straw and its persistence on the soil before and after soybean sowing, soybean yield, amount of soybean root and its nodulation in the two years of the experiment, besides the chemical and physical attributes of the soil. The results were submitted to analysis of variance and the effects of the variables were compared by the tuckey test at the 5% probability level. It is possible to increase soybean yield in regions with sandy texture and water deficit, using production systems that increase the straw production , with use of palisade grass and annual doses of N between 150 and 200 kg ha -1. The single palisade grass cultivation or intercropping with maize in the soybean harvest season allowed a greater soil cover with straw during summer soybean. However, this was not enough to increase grain yield in years with low straw production, as occurred in the 2015/2016 harvest, even with increased soybean root growth in depth, when in succession to single palisade grass. The treatments with higher straw and N inputs did not result in an increase in organic matter content in the soil, probably due to the irregularity of rainfall during the period when the forage plants, which are large producers of green mass, have the best growing conditions. The organic matter increase in the 0-10 cm layer due to the greater contribution of palisade grass straw in the first year of the experiment also resulted in an increase in soil microporosity. It was evidenced that, the organic matter content in the soil does note remain uncharged because the soil and climate conditions in which the experiment was carried out. The nitrogen fertilization did not interfere in the nodulation of the soybean, which occurred satisfactorily both in the quantity and in the mass of the analyzed nodules, when it is carried out in the production systems.