Níveis de compactação e sistemas de preparo sobreatributos físicos do solo e produtividade da soja

Abstract

Soil preparation and crop management, especially in no-tillage, due to the absence of soil disturbance associated with continuous machine traffic, can cause soil compaction and reduced crop productivity. The objective was to evaluate soil compaction in two tillage systems on physical attributes and factors influencing soybean yield components. The experiment was carried out at Fazenda Cedro, located in the city of Dourados-MS. The early cycle soybean cultivar, Monsoy 6410 IPRO, was used. The soil is a clayey-textured Oxisol. The experimental design used was a randomized block design in a split-plot scheme, with treatments consisting of two soybean cropping systems (conventional tillage and no-tillage), four increasing levels of induced soil compaction (zero, three, six, and nine passes of an agricultural tractor), with four repetitions. Soil physical attributes, growth, and soybean yield were evaluated. The data obtained were submitted to analysis of variance and, when significant, by the F test. The Student-Newman-Keuls test was used, at 5% probability, to compare the means of tillage systems and regression analysis for compression levels. Pearson's coefficient was used to analyze the relationship between soil attributes with soybean growth and productivity at 5% probability. If there was a significant correlation between variables, linear regression analysis was applied. Soil macroporosity was significantly affected by compaction and cultivation only in the 0.00-0.10 m layer, with an interaction between the tillage system and the number of tractor passes. Regarding microporosity, this was not affected in any of the treatments. Treatments significantly influenced the total porosity in the 0.10-0.20 m layer, but it was not affected in the superficial layer. For soil density, there was only an effect of compaction in the layer of 0.10-0.20 m, where after three passes of the tractor, there was an increase in density. There was also a significant effect of soil compaction for soil penetration resistance, however, in the surface layer, increasing with the number of passes of the tractor. Grain yield was influenced by the two isolated factors and interaction, showing the superiority of soybean yield in both tillage systems. While the tractor traffic intensity increased, the soil resistance to penetration and macroporosity were altered in the subsurface layer of the conventional tillage. The increase in the level of soil compaction provides an increase in density, reductions in macroporosity, and total porosity in the subsurface soil depth, especially in the area with conventional tillage. Tillage systems do not influence soybean growth, production components, and yield, but increasing the compaction level reduces yield.