Indicadores de qualidade química de um Argissolo Amarelo Distrocoeso sob diferentes sistemas de manejo

Abstract

Obtaining parameters to evaluate soil quality is a complex task, since it depends on intrinsic soil characteristics. Therefore, quality indicators are used, consisting of chemical, physical and/or biological attributes of the soils that, among other characteristics, suffer from changes that can be detected in the short, medium and/or long term. Monitoring soil health through chemical indicators is feasible because they are very effective in demonstrating the changes resulting from management, becoming essential tools for both agronomic development and environmental preservation. Considering these factors, the objective of this study was to analyze the chemical attributes as indicators of quality in a Distrocoesus Yellow Argisol typical under soybean plantation, common in the eastern region of Maranhão, using the comparison between three different areas: Native Savanna (CN) that served as a witness, a Direct Planting System (SPD) and a Conventional Processing System (SPC), in two distinct periods; dry and rainy. In each period, five sample units of 20 x 20 m were randomly allocated in the three areas studied (CN, SPD, SPC), where eight deformed samples were collected in each sampling unit at depths of 0-10, 10-20, 20-30 and 30-40 cm with the aid of a Dutch-type test, and eight undisturbed samples at the same depths in the minitrunk walls allocated in the middle of the sample units, with the aid of a 100 cm3 Kopecky ring. The following soil chemical attributes were analyzed: pH in water; Calcium and Magnesium, exchangeable Potassium and Sodium; Organic Matter, Total Organic Carbon, Total Phosphorus, Exchangeable Aluminum and Carbon Stock, which was determined by multiplying the organic C content by the mean soil volume weight per depth. Subsequently these data were submitted to analysis of variance at 5% probability. Soils in the Savanna area showed low values for most aspects evaluated, except for aluminum and organic carbon. Comparing the two management systems, the SPD did not differ from the SPC in most aspects evaluated. It was possible to change the chemical attributes of the natural soil as a function of anthropization, due to the use of fertilizers, liming among other techniques, it was also possible to observe that some chemical attributes change according to the seasonality and that the Carbon Stocks did not differ depending on the handling. It is necessary to improve conservation management systems such as the SPD for eastern Maranhão, with the objective of maintaining soil health in order to prevent, recover and/or maintain its quality, enabling agricultural development within the concepts of sustainability, showing producers that it is possible to ensure their production and productivity without major impacts to ecosystems, given the sensitivity of the Savanna to anthropization