Soil CO2 efflux dynamics in an integrated crop–livestock system

Abstract

AbstractIntegrated crop–livestock (ICL) systems have shown potential to provide a variety of environmental benefits including soil carbon (C) increases relative to conventional row cropping systems. However, studies documenting C dynamics of ICL systems in the northern Great Plains are lacking relative to other agroecosystems. Soil carbon dioxide (CO2) efflux, crop biomass, and soil organic matter (SOM) pools were monitored over 3 years in an ICL rotation (corn [Zea mays L.]/soybean [Glycine max L.]–spring wheat [Triticum aestivum L.] + cover crop–cover crop) with fall grazing, a conventional cropping system rotation (corn–spring wheat–soybean) and fall grazed and ungrazed mixed‐grass pasture near Mandan, ND. Cropped treatments were under no‐till management. Annual aboveground crop residue biomass C was similar in the ICL and conventional systems, while less in the grazed pasture (4.18, 3.83, and 1.21 Mg C ha−1 year−1 respectively; p = 0.039). Annual soil CO2 efflux was greater in the ICL, grazed, and ungrazed pasture systems than the conventional system (8.05, 8.73, 8.25, and 5.81 Mg C ha−1 year−1, respectively; p < 0.001). Among crop phases in the ICL and conventional cropping systems, cover crops contributed to greater CO2 efflux in the spring and fall. SOM and C mineralization were greater at 0–5 cm in the ICL system compared to the conventional cropping system (6.6% vs. 6.3%, p = 0.028 and 248 vs. 184 mg CO2–C kg−1, p < 0.001, respectively). Interseeded cover crops in ICL systems can contribute increased root respiration and enhanced SOM pools relative to conventional cropping systems under semiarid conditions.