Soil organic matter doubles the cation exchange capacity of tropical soil under no-till farming in Brazil.

Abstract

Agricultural conservation practices increase total organic carbon storage in soil (TOCS ), a factor that is correlated with the physical and chemical qualities of highly weathered soils. In this study, we investigated the effects of TOCS on the physicochemical attributes of a Latosol after 10 years of no-till management in Mato Grosso State, Brazil. TCOS was highly correlated (r = 0.92) with cation exchange capacity (CEC, pH = 7) and soil density. In the top 0.2 m soil layer, CEC increased by 25% with every 1.8 kg m-2 of stored organic carbon. Eliminating soil organic matter reduced CEC from an already low value of 8.40 cmolc kg-1 to 4.82 cmolc kg-1 . Humus is therefore clearly important for the formation of a negative liquid charge in a predominantly electropositive but clayey soil. We confirmed that TOCS is an indicator related to the physiochemical characteristics of weathered soils. Furthermore, our results demonstrate that the increased carbon storage under non-tilling systems is essential for guaranteeing weathered soil fertility in tropical climates. © 2018 Society of Chemical Industry.