Estrutura de um planossolo em sistema integrado de produção agropecuária em terras baixas

Abstract

The production system with a focus on monoculture commodities can deplete natural resources and reduce food security for populations around the world, endangering the development of future generations. This reinforces the fundamental role and responsibility of agricultural activity in ensuring not only food production, but produce and conserve. Integrated crop–livestock systems (ICLS) are considered excellent alternatives to increase production efficiency, optimize land use and conserve natural resources. These systems have been used for many years in different parts of the world, but their adoption in areas with difficult soil management, such as lowland (Planosols and Gleysols) is still recent, and the changes that can occur in the soil are little known. The hypothesis of this study was that the ICLS in the Lowlands for the cultivation of irrigated rice in southern Brazil improves the soil physical structure and functionality. The objective was to investigate how the different managements of these systems influence the structure and quality of a Planosol. To test the hypothesis, a long-term experiment is being developed in a Planosol located in the Inner Coastal Plain of Rio Grande do Sul, Brazil. The experiment consists of four agricultural production systems involving the cultivation of irrigated rice: i) rice - fallow - rice, without animal grazing and with soil tillage (disc harrow) in spring; ii) rice - ryegrass with grazing - rice, and no-till; iii) rice - ryegrass with grazing - soybean - ryegrass with grazing - rice, and no-till; and iv) pasture (ryegrass + white clover + birdsfoot trefoil) in winter, and succession field in the summer, being continuously grazed and cultivated with rice under no-tillage every four years. Several structural and functional parameters of soil porosity and root biomass were determined using techniques such as computed tomography. The ICLS composed mainly of grass species (rice-ryegrass) reduced the harmful effects of trampling and improved the structure and functionality of the soil, with reduction in surface bulk density, increase in available water and air permeability due to greater connectivity and pore orientation longitudinal to the flow. Soil turnover can improve quantitative parameters by matching it to integrated systems, however, it creates spherical and non-continuous pores revealed by computed tomography, which can be harmful to the functionality of the pores. The ICLS were not widely superior to the system with soil revolving, however, the results indicate that after 6 years of conducting the experiment, the soil structure has gradually benefited from conservation management, and soil disturbance is not justified.