Carbon, light organic matter and oxidizable organic carbon fractions

Abstract

The evaluation of water light organic matter and organic carbon fractioning by different oxidation degrees may contribute to the soil organic matter dynamics understanding in areas under organic management. This study aimed to evaluate the total soil organic carbon (TOC), light organic matter (LOM) in water and TOC oxidizable fractions under different organic production systems. It was selected five areas: fig cultivation, passion fruit and Desmodium sp consortium; corn/beans cultivation in conventional tillage (CT), eggplant/corn cultivation in no-tillage (NT) and agroforest system (AFS). The soil samples were collected at 0-0.05 and 0.05-0.10 m depths, and TOC, LOM in water and organic carbon oxidizable (fractions F1, F2, F3 and F4) were evaluated. The fig area showed higher TOC and N contents. The highest levels of LOM in water were observed in NT and the lowest in CT area. The highest C contents of F1 were observed in fig and passion fruit areas (0-0,05 m). For F4, the Fig and NT areas showed the C highest values (0-0.05 m). In a general way, in the fig area it was observed an increasing of TOC and N contents when compared with others areas. The NT area promot the highest LOM and N contents when compared to the CT system. The organic farming system in no-tillage with eggplant/corn provides better carbon distribution in each oxidizable fraction in relation to the TOC, showing a balance between more lability (F1) soil organic matter and more recalcitrant organic matter fraction (F4).