Agriculture accentuates interannual variability in water fluxes but not carbon fluxes, relative to native prairie, in the U.S. Corn Belt

Authors: Schreiner-Mcgraw, Adam; WOOD, JEFFREY - University Of Missouri; Metz, Megan; SADLER, EDWARD - Retired ARS Employee; Sudduth, Kenneth - Ken

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2023
Publication Date: 3/20/2023
Citation: Schreiner-McGraw, A.P., Wood, J.D., Metz, M.E., Sadler, E.J., Sudduth, K.A. 2023. Agriculture accentuates interannual variability in water fluxes but not carbon fluxes, relative to native prairie, in the U.S. Corn Belt. Agricultural and Forest Meteorology. 333. Article 109420. https://doi.org/10.1016/j.agrformet.2023.109420.
DOI: https://doi.org/10.1016/j.agrformet.2023.109420

Interpretive Summary: To support a growing population, agricultural lands must increase production while simultaneously decreasing negative environmental impacts. Important strategies to reduce negative environmental impacts include the use of cover crops and no-till agriculture to reduce soil erosion and enhance soil carbon stores, and to convert agricultural fields to restored prairie ecosystems. The impacts of these management decisions on the water and carbon cycles of a field, however, are poorly understood. In this article, we measure carbon and water fluxes from two agricultural fields (one conventionally managed with annual tillage and the other no-till with cover crops) and a native tallgrass prairie. We evaluate the sensitivity of fluxes to environmental conditions including soil water content, vapor pressure deficit, air temperature, and light availability and find that the conventional agricultural site is the most sensitive to changes in environmental conditions while the prairie site is the most resilient to changes. The interannual variability in water use is accentuated by agricultural management and because of the more diverse cropping system, is highest at the no-till plus cover crop site. The interannual variability in carbon fluxes, however, is not increased by agricultural management. These findings illustrate how conventional cropping systems are not as resilient to changes in environmental conditions as no-till systems with cover crops. This evidence supports the adoption of these conservation practices in a changing climate.

Technical Abstract: To support a growing population, agricultural lands must increase production while simultaneously decreasing negative environmental impacts. To decrease negative environmental impacts, the conversion of conventional agricultural lands to no-till with cover crops or to restored prairie in the Midwest United States has been proposed and has the potential to dramatically alter hydrologic behavior. Our understanding of the impacts of this conversion on water and carbon fluxes from the (agro-)ecosystems, however, is limited. We deployed eddy covariance systems in a business-as-usual (BAU) tilled cropping system, an aspirational (ASP) no-till cropping system with cover crops, and a native tallgrass prairie (TP) ecosystem to measure evapotranspiration (ET) and carbon dioxide exchange with the atmosphere. Measurements began in 2015 and we have at least 4 complete years of observations at each site. The average annual ET is highest at the TP site, but the gross primary production, and ecosystem respiration are highest at the ASP site. Average annual net ecosystem exchange is negative (carbon uptake) at both agricultural sites (-305 ± 147 and -311 ± 154 gC m-2 yr-1 at ASP and BAU, respectively) and neutral in the prairie (-11 ± 40 gC m-2 yr-1 at TP). We evaluate the sensitivity of fluxes to environmental conditions including soil water content, vapor pressure deficit, air temperature, and photosynthetic photon flux density and find that the BAU site is the most sensitive to changes in environmental conditions while the TP site is the most resilient to changes. The interannual variability in ET is accentuated by agricultural management and because of the more diverse cropping system, is highest at the ASP site. The interannual variability in carbon fluxes, however, is not increased by agricultural management. This study provides information on the dynamics of carbon and water fluxes from several potentially important land cover classes within the U.S. Corn Belt.