Matéria orgânica e atributos físicos de Plintossolo Argilúvico Distrófico típico em diferentes agrossistemas na Amazônia maranhense

Abstract

In the Amazon region, the conversion of primary forests into pasture areas for the development of beef cattle or agricultural activities is a common practice and that quickly, due to the management adopted, end up leading to the degradation of these areas. The objective of this work was to verify the influence of different soil uses in different periods of evaluation on the chemical attributes, total contents and carbon and nitrogen stocks of the soil. The experiment was carried out in the Technological Reference Unit (URT) in the municipality of Pindaré-Mirim/MA. The land use systems evaluated were: perennial pasture, pasture recovered for 8 years and secondary forest. In each land use system, trenches were opened in 2013 and 2019 and the layers 0.0-0.20 and 0.20- 0.40 m were sampled. Soil fertility attributes and carbon (C) and nitrogen (N) contents and stocks were evaluated. The highest soil C and N contents were found in the uppermost layer, mean CT values were 13% lower in the 8-year recovered pasture compared to the perennial pasture in the 0- 20 cm layer. The different areas and sampling depth differed significantly for the soil C and N stock variables. Ca contents varied significantly among the areas, with the highest values occurring in the perennial pasture in the two years evaluated. The Mg contents differed among the different depths. The soil density was higher for land use with perennial pasture and recovered pasture, these values may have been higher due to soil preparation for the implementation of the pasture, with the use of machinery and also by the trampling of animals during grazing, pH, differed statistically between the years of evaluation and also between the depths. The chemical attributes, contents and stocks of C and N of the soil suffered alterations as a function of land use and evaluation period. The use of multivariate analysis techniques, clustering and principal components was efficient to verify the differences between the studied environments