Sistemas integrados de cultivo e pecuária em terras baixas do Sul do Brasil: Parâmetros físicos e estoques de carbono orgânico de um Planossolo

Abstract

Lowland soils present conditions of high hydromorphism and, in turn, difficulty in inserting upland species and adopting agricultural activities. Crop rotation and the insertion of other plant species have been tested aiming at the sustainability of the production system and improvement of the physical quality of lowland soils. The objective of this work is to evaluate some physical attributes (density, porosity, aggregation and the soil water retention curve), and chemical (organic carbon stocks) of a Eutrophic Solodic Haplic Planosol in integrated systems of annual crops of grains and livestock. The study was carried out in four agricultural areas located in the municipalities of Capão do Leão and Arroio Grande, in RS. The integrated systems (IS) evaluated were: a) SCAP - Conventional lowland cultivation system in RS: Irrigated Rice - Fallow - Fallow - Fallow (extensive beef cattle); b) ILP: CropLivestock Integration System; c) ASAS: Rice-soybean-rice-soybean crop rotation; d) AASS: Rice-rice-soybean-soybean crop rotation. In the period of October and November 2020, soil samples with preserved structure were collected in the layers 0.00-0.05 m, 0.05-0.10 m and 0.10-0.20 m. The evaluations were carried out in the Soil Physics and Chemistry laboratoriesat UFPel and Embrapa Clima Temperado. Crop and livestock systems influenced some physical and chemical parameters of a Planosol in lowland areas of southern RS, especially macro and microporosity, total porosity and carbon stock. The introduction of annual crops (soybean) in the production system resulted in an improvement in physical attributes, such as total porosity, mainly in the 0-0.05m and 0.05-0.10m layer(s). It was concluded that the integrated crop-livestock system conducted under wide-base ridges reduced the physical quality of the soil, as it was observed lower microporosity, total porosity and carbon stock, on the other hand, the quality of lowland soils, especially of Planosols, can be improved by adopting annual crop rotation (soybean) in integrated cropping systems.