Tensile strength, friability, aggregation, and soil organic matter physical fractions of an Oxisol cultivated with sugarcane

Abstract

The objective of this work was to evaluate the tensile strength, friability, aggregation, and the physical fractions of soil organic matter of a Rhodic Hapludox cultivated with sugarcane (Saccharum officinarum). The treatments consisted of one, three, and five years of cultivation of sugarcane, in the state of Rio Grande do Sul, Brazil. As a reference, a native forest adjacent to the cultivation area, with soil and relief characteristics similar to those of the cultivation areas, was used. Deformed samples were collected at 0.00–0.05, 0.05–0.10, and 0.10–0.20-m soil depths, for the determination of the soil physical attributes and for the physical fractionation of particle-size and density of the organic matter. The physical attribute evaluations were able to detect changes in the structural quality of the Oxisol, which resulted from the sugarcane cultivation. In comparison with the native forest, the stability and tensile strength of the aggregates decreased with the time of sugarcane cultivation. Tensile strength increased with soil depth, proportionally to the reduction of total soil organic carbon content. Soil preparation and straw burning reduce the input of fresh organic matter into the soil and accelerate the decomposition of the labile organic matter compartment, with negative consequences to soil physical properties over time.