Effects of Agricultural Management Practices On Carbon Sequestration in Soils From a Tropical Agroecosystem: Understanding the Contribution of Geochemical Controls of Soil Carbon Sequestration.

Soil carbon (C) sequestration has been identified as one of the effective potential mitigation option for increasing atmospheric carbon dioxide concentration. Climate, mineralogy and agricultural management practices affect soil organic C (SOC) content, chemistry as well as SOC stabilization mechanisms. This research is focused on understanding the SOC sequestration based on agricultural management practices and aggregate size fractions by determining chemistry of SOC, SOC and mineral associations and interactions. 

Oxisols were collected from 0-5, 5-15 and 15-30 cm depths from the Center of Experimentation and Research Fundacep in Cruz Alta-RS, Brazil which had been under same agricultural management practices since 1985. Main plots were tillage operated plots (no till/conventional till), whereas sub plots were different crop rotations. Four aggregate size fractions were separated by wet aggregate sieving method. Humic acid was extracted from each aggregate size fraction according to IHSS method and analyzed by FTIR,¹³C NMR and HPLC. Iron (Fe) mineralogy, total OC, amorphous and total Fe/Al oxides are determined. Results will be integrated to further our understanding on how agricultural management practices affecting geochemical mechanisms controlling C sequestration in tropical soils.