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/10113/5935598
Citation: Nash, P.R., Gollany, H.T., Sainju, U.M. 2018. CQESTR simulated response of soil organic carbon to management, yield, and climate change in northern Great Plains region. Journal of Environmental Quality. 47:674-683. https://doi.org/10.2134/jeq2017.07.0273.
Interpretive Summary: In the northern Great Plains, traditional management practices, such as conventional tillage with crop-fallow, have reduced annualized crop yields due to declined soil fertility from the loss of soil organic matter. Improved management practices are needed to enhance soil organic matter, reduce carbon pollution in the atmosphere, sustain crop yields, and increase farm income through carbon-credit markets in the long term.Our objectives were to: (1) use the CQESTR model, a carbon model, to predict soil organic carbon in the top 4 inches from barley-pea , continuous barley, and barley-fallow rotation under conventional tillage and no-tillage systems with or without 71lb N /ac nitrogen fertilization through 2045 and (2) evaluate how the projected temperature and precipitation changes, crop production, and management could impact soil organic carbon while identifying best management practices to increase soil organic carbon and reduce carbon dioxide emissions in eastern Montana. If crop production and climatic conditions remained at the 2006-2011 average levels, soil organic carbon in the top 4 inches of soils was predicted to increase by 1.6 lb C/ac in barley-fallow under conventional tillage and by 4.1 lb C /ac in continuous-barley under no-tillage by 2045. When the projected air temperature and precipitation was factored in over 2012-2045, soil organic carbon was predicted to increase further by about 0.34 lb C/ac for a barley-fallow rotation and by 0.93 to 1.29 lb C/ac for continuous barley and barley-pea rotation. Based on the model simulations, changes in temperature and precipitation through 2045 may facilitate soil organic carbon accretion in the top 4 inches in the dryland cropping systems in the northern Great Plains if crop production can at least remain at current production levels. The adoption of continuous cropping, no-tillage, and nitrogen fertilization could further increase soil organic carbon stocks [GRACEnet publication].
Technical Abstract: Traditional dryland crop management includes fallow and intensive tillage, which have reduced soil organic carbon (SOC) over the past century raising concerns regarding soil health and sustainability. The objectives of this study were to: 1) use CQESTR, a process-based C model, to simulate SOC dynamics from 2006 to 2011, and predict relative SOC trends in cropping sequences that included barley (Hordeum vulgare L.), pea (Pisum sativum L.), and fallow under conventional tillage (CT) or no-till (NT), and N fertilization rates through 2045; and 2) identify best dryland cropping systems to increase SOC and reduce CO2 emissions under projected climate change in eastern Montana. Cropping sequences were conventional till/barley-fallow (CTB-F), no-till/barley-fallow (NTB-F), no-till/continuous barley (NTCB), and no-till/barley-pea (NTB-P), with 0 and 80 kg N ha-1 applied to barley. Under current crop production, climatic conditions, and averaged N rates, SOC at 0 to 10 cm depth was predicted to increase by 1.74, 1.79, 2.96, and 4.57 Mg C ha-1 by 2045 for CTB-F, NTB-F, NTB-P, NTCB, respectively. When projected climate change and the current positive U.S. barley yield trend were accounted for in the simulations, SOC accretion was projected to increase by 0.62 to 0.69 Mg C ha-1 and 0.11 to 0.47 Mg C ha-1, respectively. Based on the model simulations, adoption of NT, elimination of fallow years, and N fertilizer management will likely have the greatest impact on SOC stocks in the top soil as of 2045 in the northern Great Plains.