Decomposition of different amounts of straw sugarcane deposited on the ground in the central South Region of Brazil

Abstract

The mechanized harvesting of sugarcane deposits a large quantity of straw onto the soil. In the last few years, it was reported that this straw could be used for ethanol production, denominated second generation ethanol. However, the total removal of the straw could cause negative impacts on the soil. Therefore, it is indispensable to study specific variables that are associated with these impacts. The decomposition dynamics of plant material deposited onto the soil surface is directly linked to increase in carbon (C) stocks in the soil. The object of this study is to determine the speed of the decomposition of the different proportions of sugarcane straw (25, 50, 75, 100 and 200%) on the soil and the qualitative characteristics of the straw under different edafoclimatic conditions. With this aim, nine experiments will be set up in the field, with six annual collections, during two years, of remaning residues (0, 30, 65, 110, 175, 260 and 360 days past harvest). We will analyze C, nitrogen and structural carbohydrates of straw at each collection. With the aim of verifying small changes, over a short period, in C in the soil from the sugarcane straw we will perform a parallel experiment, to monitor the natural abundance of ´13C. In addition we will simulate the effect of deposition or removal of sugarcane straw using mathematical models. Finally, these data will be integrated through multivariant statistics (principal component analysis), with the aim of ordering the variables that affect straw decomposition. We hope that the results produce in this research can contribute in the evaluation of the environmental sustainability of second generation ethanol production in the Central South region of Brazil. (AU)