Qualidade da matéria orgânica do solo, geoestatística e simulação dos estoques de carbono e nitrogênio pelo modelo Century em latossolo do cerrado maranhense

Abstract

The Cerrado Biome has been undergoing transformations mainly related to the replacement of native forest by agricultural systems, which affect the dynamics of the organic matter compartments of the soil and consequently the C and N stocks. The objective of the present study was to evaluate the impact of integrated management and pasture systems on C and N stocks, as well as to simulate the effects of land use in these stocks and their compartments using the Century 4.5 model and to map the spatial variability of those referred to stocks in the edaphoclimatic conditions of the Cerrado of Maranhão in a Red-Yellow Oxisol. The study was carried out in the municipality of São Raimundo das Mangabeiras, Maranhão. Four areas were selected under different forms of land use (crop-livestock-forest integration, crop-livestock integration with no-till farming, crop-livestock integration with recent patch scarification and harrowing and pasture), and an area under native vegetation of Cerrado sensu stricto. The soil was classified as Red-Yellow Oxisol. Mini trenches were opened to collect soil at depths: 0.0- 0.10; 0.10-0.20; 0.20-0.30 and 0.30-0.50 m, for the study of C, N and chemical and physical fractionation of organic matter. For modeling with Century 4.5, only samples corresponding to a depth of 0.0-0.20 m were used. The system Crop-livestock integration with recent patch scarification and harrowing expressed the largest C stock and Pasture the largest N stock when taking into account the sum of the layers (0.0-0.50 m). The simulations with Century 4.5 indicated that the C and N in the passive compartment were the least affected by land use and that the slow compartment was the main responsible for the increase in C and N stocks. In geostatistics, the mean and median values are similar for the C and N stocks in their respective management systems, indicating a symmetrical distribution of the data, confirmed by the asymmetry and kurtosis values close to zero. It is concluded that the conversion of the native Cerrado forest to integrated systems and pastures increases the C and N stocks in the soil. The modeling results indicate that further adjustments are needed for the application of Century 4.5 in crop-livestock integration systems. The spatial distribution of C stocks is more homogeneous in the Crop-livestock integration with no-till farming, while the Crop-livestock integration with recent patch scarification and harrowing presents greater homogeneity in the N distribution.