Simulated soil organic carbon response to tillage, yield, and climate change in the southeastern Coastal Plains

Authors: Nash, Patrick; Gollany, Hero; Novak, Jeffrey; Bauer, Philip; Hunt, Patrick; Karlen, Douglas

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2017
Publication Date: 7/2/2018
Publication URL: https://handle.nal.usda.gov/10113/5935600
Citation: Nash, P.R., Gollany, H.T., Novak, J.M., Bauer, P.J., Hunt, P.G., Karlen, D.L. 2018. Simulated soil organic carbon response to tillage, yield, and climate change in the southeastern Coastal Plains. Journal of Environmental Quality. 47:663-673. https://doi.org/10.2134/jeq2017.05.0190.
DOI: https://doi.org/10.2134/jeq2017.05.0190

Interpretive Summary: Intensive tillage, low residue crops, and a warm, humid climate have contributed to soil organic carbon (SOC) loss in the southeastern Coastal Plains region. The objectives of this study were to: 1) use CQESTR (pronounced sequester), a process-based carbon model, to simulate SOC dynamics in the top 6 inches of a loamy sand soil over a 12 year field study (2002-2013); 2) establish relative trends in SOC due to crop rotation and tillage over a 20 year predictive period (2014-2033); 3) elucidate the impacts of projected climate change and crop yields will have on SOC stocks by 2033, relative to management; and 4) recommend best management practices to increase SOC stocks. The primary soil type was a Norfolk loamy sand. Conservation tillage was predicted to increase SOC by 89.3 to 572 lb/ac for 6 of 8 crop rotations compared to conventional tillage by 2033. The addition of a winter rye or winter wheat to a corn-cotton or corn-soybean rotation was projected to increase SOC by 1313 to 2277 lb/ac. A continued increase in crop yields following historical trends could increase SOC stocks by 250 lb/ac, while climate change projections were predicted to decrease SOC stocks up to 134 lb/ac C by 2033. The adoption of conservation tillage and cover crop management with high residue producing corn rotations will likely optimize SOC accretion in loamy sand soils in the southeastern Coastal Plains region through 2033.

Technical Abstract: Intensive tillage, low-residue crops, and a warm, humid climate have contributed to soil organic carbon (SOC) loss in the southeastern Coastal Plains region. Conservation (CnT) tillage and winter cover cropping are current management practices to rebuild SOC; however, there is sparse long-term field data showing how these management practices perform under variable climate conditions. The objectives of this study were to use CQESTR, a process-based C model, to simulate SOC in the top 15 cm of a loamy sand soil (fine-loamy, kaolinitic, thermic Typic Kandiudult) under conventional (CvT) or CnT tillage to elucidate the impact of projected climate change and crop yields on SOC relative to management and recommend the best agriculture management to increase SOC. Conservation tillage was predicted to increase SOC by 0.10 to 0.64 Mg C ha-1 for six of eight crop rotations compared with CvT by 2033. The addition of a winter crop [rye (Secale cereale L.) or winter wheat (Triticum aestivum L.)] to a corn (Zea mays L.)–cotton (Gossypium hirsutum L.) or corn–soybean [Glycine max (L.) Merr.] rotation increased SOC by 1.47 to 2.55 Mg C ha-1. A continued increase in crop yields following historical trends could increase SOC by 0.28 Mg C ha-1, whereas climate change is unlikely to have a significant impact on SOC except in the corn–cotton or corn–soybean rotations where SOC decreased up to 0.15 Mg C ha-1 by 2033. The adoption of CnT and cover crop management with high-residue-producing corn will likely increase SOC accretion in loamy sand soils. Simulation results indicate that soil C saturation may be reached in high residue rotations, and increasing SOC deeper in the soil profile will be required for long-term SOC accretion beyond 2030.