Managing Soil Organic C with Cover Crops.

Cover crops can be potential companion crops to current agricultural practices to maintain or build soil organic C (SOC) and enhance other soil ecosystem services. For example, cover crops could ameliorate negative effects of crop residue removal for biofuel or livestock production on SOC. Such interactions of cover crops with other practices have not been widely discussed. The objective of this presentation is to discuss published information on the impacts of corn (Zea mays L.) residue removal, cover crops, and cover crop addition following corn residue removal on SOC and related soil ecosystem services. Our literature review indicates that corn residue removal at rates above 65% can reduce SOC stocks by 0.3 to 2.9 Mg ha^-1 yr^-1, whereas cover crops can increase SOC by 0.5 to 1.5 Mg ha^-1 yr^-1 in the upper 30 cm of the soil, depending on soil texture, tillage, climate, and other factors. The significant rates of SOC sequestration by cover crops suggest that these crops can be used to offset SOC losses due to residue removal. Studies specifically evaluating the cover crop effects on soil services after residue removal are few and short term (<6 yr). The few studies indicate that cover crops may or may not have potential to offset the negative effects of high rates of residue removal on SOC in the short term. More research data on the potential of cover crops to offset SOC losses after residue removal are needed across different soils, management scenarios, and climates. Overall, SOC stocks decrease with high rates of crop residue removal and increase with cover crops, but the effects of cover crops after residue removal SOC and other soil properties warrant further research.