INFLUENCE OF THE FORM OF HARVESTING AND WASTE APPLICATION ON THE CARBON MANAGEMENT INDEX AND SOIL AGGREGATION UNDER SUGARCANE CULTIVATION

Abstract

Waste application from the sugar-alcohol industry in the soil is a viable alternative from the point of view of the disposal of these residues, in addition to fertilizing the soil with nutrients. The aim of this study was to evaluate the physical fractions of soil organic matter (SOM), carbon management indexes (CMI) and the aggregation of a Red Latosol of clayey texture in areas of sugarcane cultivation managed differently regarding harvest and waste application. Five sugarcane cultivated areas were evaluated, differing in the management of harvest (raw and burned) and application or not of vinasse and/or filter cake, in addition to a reference area of native forest (NF) of Cerrado vegetation. Disturbed soil samples were collected in the layers 0-0.05; 0.05-0.1 and 0.1-0.2 m, and undisturbed samples were collected in the layer 0-0.1. In the disturbed samples, total carbon (TC), physical-granulometric fractionation of SOM were determined with subsequent CMI calculations. Aggregation analysis was performed in the undisturbed samples, and the weighted mean diameter (WMD), geometric mean diameter (GMD) and percentage of aggregates retained in the different sieve classes were determined, in addition to determining the TC contents of each aggregate class. The NF presented the highest levels of TC, particulate carbon (C-POM) and mineral (C-MOM). Among the managed areas, the area that received filter cake and vinasse application stood out with higher levels of TC, C-POM and C-MOM in the most subsurface layer. All areas cultivated with sugarcane presented CMI lower than the area of NF. The worst aggregation indexes were observed in the area with management with burning in the pre-harvest and application of only filter cake, and the best aggregation indexes were in the NF. There was a significant correlation between the aggregation indexes and soil TC contents. The area with the practice of burning, but with joint application of filter cake and vinasse for 16 consecutive years provided greater aggregation of soil and better CMI among the areas cultivated with sugarcane.