PHYSICAL ATTRIBUTES, TOTAL CARBON AND 13C NATURAL ABUNDANCE IN FERRALSOL UNDER DIFFERENT AGRICULTURAL SYSTEMS

The objective of this study was to evaluate the bulk density, total pore volume, carbon stock and natural abundance of 13C in Rhodic Ferralsol in no-tillage system (NTS) areas under different succession and rotation of cultures in the Cerrado of Goiás State, Brazil. In order to do so, NTS areas were selected in Montividiu, Goiás, under the same soil and climatic conditions as the following rotations: soybean-corn succession, soybeanmillet succession, soybean-corn-millet-beans-cotton rotation, soybeancorn-brachiaria succession and a pasture area (PA), used as a control. In each area, samples were collected at depths of 0.0–0.05, 0.05–0.10, 0.10– 0.20, and 0.20–0.40 m. The lowest levels of carbon content and stocks were verified in PA in comparison to the other areas evaluated. The NTS with soybean-corn-millet-beans-cotton crop rotation followed by NTS with soybean-corn-brachiaria succession were those that presented greater potential for carbon stock increase and total soil pore volume, as well as bulk density reduction. The origin of the soil organic matter in the NTS areas is related to plants employing the C4 photosynthetic cycle; however, for mixed C3 and C4 plant systems, the isotopic signature of 13C is reduced, mainly in areas with crop rotation.