Monitoramento dos atributos físicos do solo e produtividade de cana-de-açúcar em função de diferentes sistemas de preparo de solo

Abstract

This study evaluated the behavior of soil physical properties in growing plant sugarcane and ratoon cane in a Typic Haplustox soil under different tillage systems. The experiment was done in the Cerrado region, at Usina Jalles Machado, in 2009, with sugarcane variety CTC 02. The experimental design was randomized blocks (RBD), and soil total porosity, macroporosity, microporosity and bulk density were measured in split plots 6 x 2 (soil preparation as the factor plot, and planting dates as subplot factors), in four replications. The evaluations were done within each soil layer (0-0.2, 0.2-0.4 and 0.4-0.6 m). The other variables were evaluated in 6 x 3 split-plot factorial (where soil preparation was the factor in the plots, and soil layers the subplot factor), with four replications. The treatments were the types of tillage: 1. Moldboard + drying + Harrow; 2. Ripper + Harrow; 3. Desiccation + Direct furrowing; 4. Desiccation Ripper + Direct furrowing; 5. Stubble trasher + Ripper; 6. Stubble trasher + Harrow + Moldboard + Harrow. Sugar cane productivity, total porosity, macroporosity, microporosity, bulk density and resistance to penetration were evaluated, in the year of plant cane and second ratoon year. The geometric mean diameter and aggregate distribution in classes 4-2, 2-1, 1-0.5, 0.5-0.25 and <0.25 mm, soil organic matter, water dispersible clay and flocculation index, were evaluated only in ratoon cane. All evaluations were performed at 0-0.2, 0.2-0.4 and 0.4-0.6 m. The results were submitted to ANOVA and the averages compared by the Tukey test (P<0.05). The system of direct furrowing had the greatest macroporosity and total porosity in the layer 0-0.2 m. Decrease in macroporosity and total porosity, as well as increases in density values in the layer 0.4 to 0.6 m were observed in ratoon cane. Soil resistance to penetration was greater in the layer 0.2-0.4 m. The system furrowing directly showed the smallest values of clay dispersed in water, while the system of Stubble trasher + Harrow + moldboard + Harrow, the greatest values. Greater levels of soil organic matter were found in the 0-0.2 m layer in the system directly furrowing. Greater values of geometric mean diameter and aggregate size classes between 4-2 mm were found the 0-0.2 m layer in systems direct furrowing and direct furrowing + ripper. The greatest yield was obtained with use of the moldboard plow + Harrow and Stubble trasher + Harrow + moldboard + Harrow; however, the system with direct furrowing, besides contributing for better soil physical quality, productivity values were very close to systems with joint use of the moldboard plow.