ORGANIC CARBON AND CARBON STOCK: RELATIONS WITH PHYSICAL INDICATORS AND SOIL AGGREGATION IN AREAS CULTIVATED WITH SUGAR CANE

Abstract

Soil organic carbon and carbon stock influence, directly or indirectly, most of soil aggregate stability indicators. The objective of this study was to quantify the production of dry biomass (DB), total organic carbon (TOC) and carbon stock (CStk) in soil, and to evaluate their influence on some indicators of aggregation in an Oxisol at a Cerrado biome in Uberaba-MG, Brazil. The design was completely randomized blocks, in two evaluation periods: three and six cuts, at six depths (0-0.1, 0.1-0.2, 0.2-0.3, 0.3-0.4, 0.4-0.5 and 0.5-0.6 m). It was evaluated: soil density (SD), volumetric humidity (VH), aggregate stability index (AEI), weighted mean diameter (WDA), mean diameter (GDA), index of aggregates with diameter greater than 2 mm (AI) and sensitivity index (SI), replicated by 4. The best AEI of the soil and the highest TOC contents were found in the most superficial layers, 0 to 0.2 m, for both cuttings. The greater values of TOC and CStk, occurred at the sixth cut area, where there was a higher amount of DB on soil surface. The higher levels of organic matter did not provide higher AEI in the area of sixth cut, when compared to that of the third cut. The TOC and CStk levels in both areas generally had a positive influence on soil aggregation indicators for both cuts.