Abstract
Identifying and quantifying conservation-practice adoption in U.S. cropland is key to accurately monitoring trends in soil health regionally and nationally and informing climate change mitigation efforts. We present the results of an automated system used across 645 counties in the United States Corn Belt from 2005 to 2018, mapped at field-scale and summarized for distribution at aggregated scales. Large-scale mapping by OpTIS (Operational Tillage Information System), a software tool that analyzes remotely sensed data of agricultural land, provides trends of conservation tillage (defined as >30% residue cover), cover cropping, and crop rotations, while modeling by DNDC (Denitrification–Decomposition), a process-based model of carbon and biogeochemistry in soil, provides estimates of the ecosystem outcomes associated with the changes in management practices mapped by OpTIS. Ground-truthing data acquired via OpTIS mobile, a roadside field-surveying app, were used for verification in 30 counties. OpTIS results for the Corn Belt show adoption of cover crops after planting corn and soy increased from 1% to 3% of the mapped area when comparing 2006 to 2018. Comparison of trends for conservation tillage use from 2006 to 2018 shows a slight decrease in conservation tillage adoption, from 46% to 44%. Results from DNDC show these soils sequestered soil organic carbon (SOC) at an area-weighted mean change in SOC (dSOC) rate of 161 kgC/ha/year. Comparatively, in a scenario modeled without the adoption of soil health management practices, the same soils would have lost SOC at an area-weighted rate of −65 kgC/ha/year. As many factors affect changes to SOC, including climate and initial SOC in soils, modeling counterfactual scenarios at the field scale demonstrates outcomes of current soil health management in comparison to regional management practices and best management practices, with respect to SOC sequestration. Regional trends in adoption rates of conservation agriculture and resulting soil health implications are of great use for a wide range of stakeholders. We demonstrate the capability of OpTIS remote sensing to deliver robust, large-scale, multi-sensor, ground-verified monitoring data of current and historical adoption of conservation practices, and of DNDC process-based modeling to provide assessments of the associated environmental outcomes across regions in U.S. cropland.
Highlights
In 2019, atmospheric CO2 levels reached a level not seen at any point in the past 800,000 years [1].CO2 absorbs less heat per molecule than methane (CH4 ) and nitrous oxide (N2 O), but it is more abundant in the atmosphere, it contributes proportionally more of the total energy imbalance causing the Earth’s temperature to rise [1]
We present the results of a novel large spatial–temporal scale use of earth-observing remote sensing data to map and monitor the adoption rates of conservation management techniques, and model C dynamics associated with these conservation management practices
We report on Operational Tillage Information System (OpTIS) and DNDC data trends across the Corn Belt
Summary
In 2019, atmospheric CO2 levels reached a level not seen at any point in the past 800,000 years [1].CO2 absorbs less heat per molecule than methane (CH4 ) and nitrous oxide (N2 O), but it is more abundant in the atmosphere, it contributes proportionally more (about two-thirds) of the total energy imbalance causing the Earth’s temperature to rise [1]. Soil disturbance and residue cover management practices are key components of conservation agriculture. Efficacious sustainable agriculture systems rely on conservation management of residue and tillage, making use of no-till practices; planting in narrow slots or tilled strips established in the untilled seedbed of the previous crop, and reduced till practices; planting with residue left on the soil surface year-round with limited soil-disturbing activities such as using vertical tillage, chiseling, and disking [9]. Cover crop planting has demonstrated numerous benefits, including erosion control, increase in soil fertility, sequestration of organic matter, improvement in overall soil health, increase in populations of pollinators, beneficial effects on water quantity and quality, and attenuation of sediment movement and nutrient leaching [10]. Insight from U.S farmers on the use of cover cropping highlights increased motivation in cover crop use stemming from other benefits like weed control, increased moisture retention, livestock grazing, and reduced input costs with respect to fertilizer use [11]
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