Frações orgânicas e índice de manejo de carbono do solo em diferentes sistemas de produção orgânica

Abstract

ABSTRACT The effect of organic management may have a positive influence on the fractions of soil organic matter. This study aimed to evaluate the fractions of soil organic content and carbon management in areas subject to organic management under different systems of soil use. The areas selected presented the following systems of soil use: conventional tillage (CT) with corn cultivation, no tillage (NT) with eggplant cultivation, reduced tillage (RT) with fig cultivation, passion fruit and Desmodium sp combination and an agroforest system (AFS). An area of secondary forest was taken as reference for the original condition of the soil. The soil samples were taken at depths of 0-5 and 5-10 cm. We quantified the total organic carbon (TOC), particulate organic carbon (POC) and organic carbon associated with minerals (OCam). These measures were used to estimate the stock (StTOC, StPOC and StOCam) and carbon management (CMI) indexes. In the 0-5 cm depth there were higher levels of TOC in the fig (RT) followed by eggplant (NT), and the depth of 5-10 cm found major differences between the areas evaluated for this attribute. The StPOC was greater in the area under direct sowing (0-5 cm), and was different between all areas in depth. This area also had the highest CMI. The best StOCam were observed in the fig (RT) in both depths; these were different than the other areas. The results indicate that the TOC was more effective in identifying changes due to the management adopted at a depth of 5-10 cm, while StPOC was the best measure for surface soil (0-5 cm). The CMI found in the eggplant under NT, managed organically and with the use of legumes as green manure, demonstrated the greatest sustainability of the system in relation to other areas.