Assessing the effectiveness of agricultural conservation practices in maintaining soil organic carbon under contrasting agroecosystems and a changing climate

Authors: Gollany, Hero; Del Grosso, Stephen - Steve; Dell, Curtis; Adler, Paul; Polumsky, Robert - Wayne

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2021
Publication Date: 5/26/2021
Citation: Gollany, H.T., Del Grosso, S.J., Dell, C.J., Adler, P.R., Polumsky, R.W. 2021. Assessing the effectiveness of agricultural conservation practices in maintaining soil organic carbon under contrasting agroecosystems and a changing climate. Soil Science Society of America Journal. 85(5):1362-1379. https://doi.org/10.1002/saj2.20232.
DOI: https://doi.org/10.1002/saj2.20232

Interpretive Summary: The potential of conservation practices to maintain soil organic C (SOC) and reduce climate change impacts on yields is unknown. This study aimed to validate the Day-Cent model with observed yield data and the CQESTR model with measured SOC in two agroecosystems, and predict the best practices to sustain SOC under projected climate change. Data were from a conventional tillage (CT) wheat-fallow rotation, no-till (NT) wheat-fallow and NT wheat-pea cover crop, either without nitrogen (N) fertilizer or with 120 lb N/ac fertilizer, at Pendleton, OR; and crop rotations with CT and NT silage or grain corn-soybean-alfalfa with or without manure or stover removal or cover crop at State College, PA. Measured and CQESTR-simulated SOC values were significantly correlated. At Pendleton, SOC in the top 2-ft depth increased in NT wheat-fallow with 120 lb N/ac and yield increase, and NT wheat-pea cover crop using current yields. All CT, and NT plots with 0 lb N/ac lost SOC under both climate scenarios with current average wheat yields. The NT management under dryland production provided a limited increase in SOC. In Pennsylvania, predicted SOC in the 3.3-ft depth decreased in corn-soybean under CT or NT with stover removal, but increased in NT and dairy forage NT with manure added, under projected climate change. Responses of SOC to climate change were affected by experimental conditions, local climate, and type of biomass inputs. Cover crops, native perennial grasses or alfalfa, and organic inputs such as manure under NT are agricultural management strategies for maintaining or increasing SOC and improving resiliency of agroecosystems to extreme weather events and agricultural sustainability.

Technical Abstract: The potential of conservation practices to maintain soil organic C (SOC) and reduce climate change impacts on yields is unknown. This study aimed to validate the Day-Cent model with observed yield data and the CQESTR model with measured SOC in two agroecosystems, and predict the best practices to sustain SOC under projected climate change. Data were from a conventional tillage (CT) wheat (Triticum aestivum L.)-fallow rotation without N or with 135 kg N/ha fertilizer, and no-till (NT) experiments, NTA (NTA0W-F and NTA135W-F) and NTB with a wheat-pea (Pisum sativum L.) cover crop (NTB0W-P and NTB135W-P) in Oregon; and crop rotations with CT and NT silage or grain corn (Zea mays L.)-soybean [Glycine max (L.) Merr.]-alfalfa (Medicago sativa L.) with or without manure or stover removal or a cover crop in Pennsylvania. Measured and CQESTR-simulated SOC were significantly (p <0 .0001) correlated (r = 0.90). In Oregon, predicted SOC to 60 cm increased under NTA135W-F and NTB135W-P at 0.05 and 0.08 Mg/ha/yr under projected climate change, respectively. The NT management under dryland production provided a limited SOC increase. In Pennsylvania, predicted SOC to 1 m decreased at 0.07 Mg/ ha/ yr in corn-soybean under CT or NT with stover removal, but increased by 0.71 Mg/ha/ yr in dairy forage NT and manure added under climate change. The responses of SOC to climate change were affected by management, biomass type, edaphic properties, local climate, and agroecosystem.