Soil carbon, organic matter fractions, and soil physical quality under different sugarcane harvesting systems in north-east Brazil

Context Sugarcane cultivation is one of the main agricultural activities in Brazil. Among the production systems, unburnt harvesting has gained prominence and has been replacing the burning system. The use of unburnt harvesting system increases straw retention on soil surface, which influences the quantity and quality of soil organic matter (SOM). Aims We evaluated the effects of burnt and unburnt sugarcane harvesting systems on soil organic carbon (SOC) stocks and SOM dynamics in the north-east region of Brazil. Methods The study was conducted at three sites, each containing one area of burnt sugarcane harvesting system (Bs), two areas of unburnt sugarcane harvesting systems (Us) and one area of native vegetation (NV), totaling 12 collection sites. Key results The results show that the conversion of NV to sugarcane cultivation areas led to SOC loss, which ranged from 7% to 62%, and reduced soil quality due to losses of particulate organic matter (POM) and increased soil bulk density (BD), being corroborated by changes in other indicators, such as soil degree of compactness (SDC), and reduction in the soil structural stability index (SSI). Conclusions Despite the losses when compared to NV, the Us system showed increments in SOC, POM-C, and SSI and reductions in BD and SDC compared to Bs. Implications The findings of this study highlight the importance of understanding the impact of land use change on the properties of SOM.