Predicted Annual Biomass Input To Maintain Soil Organic Carbon Under Contrasting Management

Corn (Zea mays L.) residue is an important source of lignocellulosic feedstocks for meeting the US renewable energy goals. However, there is uncertainty in how much biomass can be sustainably harvested. The objectives of this study were to (i) simulate soil organic carbon (SOC) dynamics in the 0-20, 20-30, and 0-30 cm soil depths for the 2005-2015 study period using CQESTR, a process-based C model; (ii) establish trends in SOC with residue removal and tillage management over the predictive period of 2016-2035; and (iii) recommend practices to maintain SOC stocks in a corn-soybean (Glycine max L. [Merr.]) rotation with corn residue removal in western Minnesota. The residue removal treatments in the conventional tillage since 1995 (CT95) and no tillage since 1995 (NT95) were initiated in 2005, and in 2006 for the no tillage since 2005 (NT05). Corn residue removal treatments were none, cob removal, similar to 50% removal, and similar to 75% removal (R0, RCob, R50, and R75, respectively). Only R0 in NT05 increased SOC (0.32 Mg C ha(-1) yr(-1)) stocks in the top 30 cm soil depth by 2035 with annual aboveground biomass input of 6.30 Mg ha(-1) yr(-1). It was concluded that only the NT05 field has the potential to maintain SOC at the current rate of biomass addition, and a minimal annual aboveground C (MSC) input of 3.75 Mg C ha(-1) yr(-1) is required to maintain SOC until 2035. These simulation results indicate that caution should be used in removing residue especially under conventional tillage.