Brazil is the world's largest sugarcane producer, so changes in sugarcane management in Brazil can affect the environment to a great extent. During almost one century, studies were carried out in cropping systems involving pre-harvest burning of aerial sugarcane residues. Nowadays the green trash management of sugarcane residues has become a common practice, although the effects are still poorly documented. The objective of this work was to compare topsoil carbon and nitrogen stocks, aggregation and bulk density in Brazilian sugarcane plantations where aerial residues were either burned (Cq) or left on the soil surface (Sq) after harvest. The study was carried out in three plantations, one on a clayey soil (Latossolo Vermelho, LVdf, i.e. Typic Hapludox) and two on sandy soils (Argissolo Vermelho-Amarelo, PVAd, i.e. Typic Hapludult, and Neossolo Quartzarênico, RQo, i.e. Quartzpsamment). On each plantation, the experimental design included six replications per treatment. After three crops, the accumulated aerial residue biomass in Sq treatment amounted to 40 t ha-1 of DM from which 4.5 and 3.6 t ha-1 of DM (i.e. 11 and 9 %) were still present at the soil surface in LVdf and RQo, respectively. This represented 1.60 and 1.35 t ha-1 of C and 0.022 and 0.021 t ha-1 of N, respectively. As a result, soil carbon at a 0-20 cm depth increased by 6.3 and 4.7 t ha-1 in LVdf and RQo, respectively. Over the three-year period, the rate of carbon sequestration in the litter and topsoil in the Sq treatment was 2.63 and 2.02 t ha-1 yr-1 in LVdf and RQo, respectively. Topsoil content of stable macroaggregates was also higher with Sq than with Cq: 814 vs. 693 g kg-1 in LVdf, and 516 vs, 420 g kg-1 in RQo, respectively. On the other hand, Sq caused topsoil compaction (PVAd and RQo) due to the mechanized harvest system. In the Brazilian soils under study, green trash management of sugarcane residues improved the topsoil properties and promoted carbon and nitrogen sequestration in the litter and topsoil.
aggregate stability; burning; mechanized harvest; soil cover
