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

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. Lateplanted cover crops that were terminated early had minimal environmental benefit,

Recent Rapid Increase of Cover Crop Adoption Across the U.S. Midwest Detected by Fusing Multi‐Source Satellite Data

“…Beyond adoption, outcome‐based incentives are more effective to promote the environmental benefits of cover cropping compared to action‐based incentives. Further work on quantifying cover crop growth outcomes, such as cover crop biomass (Thieme et al., 2022), nutrient content (Wang et al., 2021), and their environmental benefits on soil and water quality (Qin et al., 2021), can improve the efficacy of incentive programs.…”

Assessing relationships of cover crop biomass and nitrogen content to multispectral imagery

“…been reported as high as 11 Mg ha −1 in some Maryland fields (Thieme et al, 2023). However, GDD, an important predictor of plant growth, will not explain biomass production in all instances (Jennewein et al, 2022).…”

“…Farmers employ various cover crop management strategies, with termination timing being one of them. The accumulation of growing degree days (GDD), whether from earlier fall planting or later termination, should result in greater biomass (Balkcom et al., 2015; Baraibar et al., 2020; Butler et al., 2002; Otte et al., 2019; Pantoja et al., 2016; Reed et al., 2019; Thieme et al., 2023).…”

“…For instance, early boot cereal rye (Secale cereale) biomass can be as low as 1.4 Mg ha −1 but can reach 7.1 Mg ha −1 at later growth stages (Duiker & Curran, 2005), and has even been reported as high as 11 Mg ha −1 in some Maryland fields (Thieme et al., 2023). However, GDD, an important predictor of plant growth, will not explain biomass production in all instances (Jennewein et al., 2022).…”

“…Even when species are not considered, additional challenges in using remote sensing can arise during the growing season. Calibration equations using NDVI may require separate algorithms in the winter and spring (Theime et al., 2023). Additionally, winter freeze events may cause the senescence of leaf tissue, which is not measured by NDVI, even if the leafy biomass remains.…”