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

Abstract

BACKGROUND: 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. RESULTS: 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. CONCLUSION: 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.