Sequestration of native soil organic carbon and residue carbon in complex agroecosystems

Abstract

Knowing short-term gains and losses of soil organic carbon (SOC) is crucial for understanding the role of different land management practices in climate change mitigation. This study evaluated the flow of carbon (C) in soil from two differently configured intercrops [1:2 (one row of maize and two rows soybean); 2:3 (two rows of maize and three rows of soybean)] compared to a maize and soybean sole crop as a result of residue addition. Addition of soybean or maize residues significantly increased (p < 0.05) SOC, light fraction (LF-C), and soil microbial biomass (SMB). Soil organic C from native sources was significantly greater (p < 0.05) than C from new (residue) sources. The LF had a significantly greater (p < 0.05) C content from new sources. Treatments amended with soybean residue had a significantly greater (p < 0.05) contribution from new C sources for SOC and LF than treatments amended with maize residue. The SMB-C was significantly greater (p < 0.05) in the 2:3 intercrop. Cumulative soil CO2 emission was significantly lower (p < 0.05) in intercrops than in sole crops. CO2 emissions derived from new C sources was significantly greater (p < 0.05) than that derived from native sources in maize amended treatments; and not significantly different (p < 0.05) for treatments amended with soybean residues.