Remote sensing evaluation of winter cover crop springtime performance and the impact of delayed termination

Authors: THIEME, A. - University Of Maryland; HIVELY, W. - Us Geological Survey (USGS); Gao, Feng; Jennewein, Jyoti; Mirsky, Steven; SOROKA, A. - Us Geological Survey (USGS); KEPPLER, J. - Maryland Department Of Agriculture; BRADLEY, D. - Maryland Department Of Agriculture; SKAKUN, S. - University Of Maryland; McCarty, Gregory

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2022
Publication Date: 1/11/2023
Citation: Thieme, A., Hively, W.D., Gao, F.N., Jennewein, J.S., Mirsky, S.B., Soroka, A., Keppler, J., Bradley, D., Skakun, S., McCarty, G.W. 2023. Remote sensing evaluation of winter cover crop springtime performance and the impact of delayed termination. Agronomy Journal. 15:442–458. https://doi.org/10.1002/agj2.21207.
DOI: https://doi.org/10.1002/agj2.21207

Interpretive Summary: Winter cover crops reduce soil erosion and take up excess nitrogen. The Maryland Department of Agriculture (MDA) Winter Cover Crop Program introduced a delayed termination (after May 1) incentive in 2019 to promote springtime biomass accumulation. However, the impact of the delayed termination has not been fully evaluated yet. This study estimated cover crop biomass, nitrogen, and carbon accumulation associated with regular- and delayed-terminated fields using satellite remote sensing and in situ measurements. Results show that the delayed-termination fields accumulated additional biomass, nitrogen, and carbon. The additional biomass, carbon, and nitrogen sequestration achieved through the delayed termination incentive were more cost-effective than early-termination base payments. The findings support the Winter Cover Crop Program for improving agroecosystem services.

Technical Abstract: In 2019, the Maryland Department of Agriculture's Winter Cover Crop Program introduced a delayed termination incentive (after May 1) to promote springtime biomass accumulation. We used satellite imagery calibrated with springtime in situ measurements collected from 2006–2021 (n = 722) to derive biomass estimates for Maryland fields planted to cereal cover crop species (286,200 ha total over two seasons). Cover crop C content remained steady throughout the cover crop growing season (42.6% of biomass), whereas N concentration had an inverse relationship with biomass and ranged from 1.7 to 2.9%. Throughout Maryland, delayed termination fields (n = 19,120; average termination of May 18) were, on average, estimated to accumulate an additional 789 kg of biomass, 15 kg of N, and 336 kg of C per hectare when compared to fields associated with standard termination dates (n = 28,811; average termination of April 16). Over two cover crop seasons (2019–2021), the delayed termination incentive yielded an extra 75,660,000 kg biomass, 1,526,000 kg N, and 32,230,000 kg C across 96,040 hectares. Regularly terminated field incentives cost an average of US$0.10 per kg of biomass and $4.09 per kg of N, with variability associated with agronomic management (species, planting method). Delayed termination fields cost of $0.08 per kg of biomass and $3.51 per kg of N. Late-planted cover crops that were terminated early had minimal environmental benefit, and wheat, which comprised 68% of cover crop area, performed poorly compared with other cereal species. Our findings demonstrate that substantial additional springtime biomass, C, and N accumulation were achieved through the delayed termination incentive.