Sistemas de manejo e níveis de compactação nos atributos químicos do solo e na exportação de nutrientes pela soja

Abstract

Soybean is one of the main crops grown globally due to its potential for cultivation in different regions. It is known that the soil structure influences its physics, as evidenced in several published studies. However, it also has a significant influence on its chemical aspects, such as the cycling of carbon and nutrients, among other determining factors for the proper development of plants. Therefore, considering the importance of soil conservation, with consequent improvement in fertility and increase in crop productivity, the objective of this study was to evaluate the occasional effect of compaction levels and cropping systems on the chemical attributes of the soil and the export of nutrients by soybeans. The experiment was carried out at Fazenda Cedro, located in the city of Dourados, MS. The soil in the area is characterized as Latossolo Vermelho Distroférrico, with a clayey texture. The experimental design was in randomized blocks, in split plots (2x4), consisting of two soil tillage systems (No-tillage and Conventional tillage) and four levels of compaction per pass through the tractor wheels (zero, 3, 6 and 9 strides), with four repetitions. The physical attributes of the soil were initially evaluated to characterize the experimental area. Before the soybean harvest, samples were collected for chemical analysis of the soil, taking a 0-10 and 10- 20 cm deep sample from each experimental unit, totaling 64 soil samples, for later determination of nutritional values. Grain samples were taken from each experimental unit at harvest time, totaling 32 samples for nutritional analysis, determining the macronutrients. The data obtained were submitted to analysis of variance, using the F test and the means using the Tukey test, at 5% probability. To evaluate the correlation between the chemical attributes of the soil with the physical attributes, Pearson's correlation analysis was used. The P concentration increases up to 6 passes. The contents of Ca and Mg in the soil increase after 3 passes, while the contents of K and MO show higher concentrations with greater compaction. The highest content of S was observed in the subsurface layer up to 4 passes. Soil compaction reduces P and Mg export, which is also harmed by cropping systems. Higher levels of compaction favor the concentration of K and N in soybeans. Ca is not affected by compaction or cropping systems. Soybean growth, production components, and yield are not influenced by soil tillage systems while increasing the level of compaction reduces yield.