Changes in soil chemical reactions in response to straw sugar cane and vinasse

Abstract

Sugarcane harvesting is predominantly mechanical because of environmental restrictions, reduced requirements for manpower, and the quest for improved efficiency. Therefore, large amounts of straw remain available in the soil. Vinasse, a liquid waste, is a main byproduct of the sugar and alcohol industry, in addition to sugarcane straw. Both accumulate in sugarcane fields; however, the effects of their interaction are unclear. In this study, the effects of applications of sugarcane straw and vinasse on the pH and the potassium (K), calcium (Ca), and magnesium (Mg) concentrations of a dystroferric Red Nitosol with a high base saturation were examined. The profiles of soil samples from sugarcane plantations collected at depths of 0-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0,30 m were reproduced in 64 polyvinyl chloride (PVC) columns with dimensions of 0.036 × 0.30 m (diameter × height). The soils were treated with doses of 0, 125, 250, and 500 m3 ha-1 sugarcane vinasse and 0, 3, 6, and 9 t ha-1 sugarcane straw and incubated for 60 days. Following the analysis, by layer, the data were subjected to analysis of variance by partitioning the degrees of freedom into orthogonal polynomials. The pH and the Ca, Mg, and K concentrations increased throughout the soil profile upon vinasse application. An acid-base imbalance was observed in the topsoil layers in association with the high K saturation. The application of sugarcane straw enhanced the effects of the vinasse across all of the depths analyzed but did not increase the pH. The best results were obtained when applying a dose of 300 m3 ha-1 vinasse and 6 t ha-1 sugarcane straw.