Regulation of surface and sub-surface soil organic carbon sequestration in water-limited landscapes with integration of circular perennial grass buffer strips

Abstract

Soil organic carbon (SOC) sequestration through innovations in agriculture, including integrating perennial grasses with annual crops, can mitigate climate change. However, integrating circular buffer strips (CBS) of perennial grasses with annual crops in water-limited semi-arid landscapes is a new concept, and how SOC and nitrogen (N) pools respond to CBS and what drives SOC sequestration in the surface and sub-surface depths with CBS integration in typical annual cropping is lacking. Our evaluation of the response of SOC and N fractions under buffer strip grass (BSG), adjacent buffer strip corn (BSC), and continuous conventional corn (CCC) without grass buffer after six years of grass establishment show contrasting trends. The SOC in 0–20 cm depth was 13.1 % greater under BSC than under CCC, while BSG had 49.7–68.2 and 17–29.9 % greater potentially mineralizable carbon (PMC) than CCC and BSC in 40–60 and 60–80 cm, respectively. Mineral-associated organic carbon (MAOC) in 60–80 cm depth was 29.9 % greater under BSG than CCC. Soils under BSC also accumulated 65.6 % more particulate organic carbon (POC) than under CCC in 0–20 cm. While POC contributed to SOC sequestration in surface soils, an increase in MAOC contributed to SOC accumulation in deeper profiles. Integrating buffer strips of perennial grasses enhances soil profile C sequestration in semi-arid agroecosystems through divergent mechanisms in surface and subsurface depths.