Seasonal vapor pressure deficit and temperature effects on carbon dioxide and water dynamics in a prevalent crop rotation in the Northern Great Plains

Authors: Whippo, Craig; Saliendra, Nicanor; Liebig, Mark; Archer, David

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2025
Publication Date: 1/27/2025
Citation: Whippo, C.W., Saliendra, N.Z., Liebig, M.A., Archer, D.W. 2025. Seasonal vapor pressure deficit and temperature effects on carbon dioxide and water dynamics in a prevalent crop rotation in the Northern Great Plains. Agricultural and Forest Meteorology. v363. https://doi.org/10.1016/j.agrformet.2025.110425.
DOI: https://doi.org/10.1016/j.agrformet.2025.110425

Interpretive Summary: In the northern Great Plains of the United States, producers are growing more spring wheat, corn, and soybeans in a rotation. The weather in this area is very unpredictable, and it may become more variable. But it is not known how these crops will respond to these weather extremes. A primary concern is if weather extremes lead to carbon loss and increased water use that can reduce long-term crop productivity. We analyzed weather and gas flux data over two rotation cycles in a spring-wheat, corn, and soybean rotation in a no-till, rainfed field. We found that hotter and drier air was associated with less soil moisture, which had a greater impact on carbon balances than rainfall. The results also showed that water loss was mostly driven by warmer air during the dormant season, but water loss was more resistant to warmer and dry air during the growing season. Low rainfall dried out the soil, which limited water and carbon fluxes during the growing seasons. These results suggest that expected increases in evaporative demand due to high temperatures and/or low humidity may increase drought stress. This may increase the need for farmers to use conservation practices, such as planting cover crops or keeping residue, to keep more water in the soil during the dormant season.

Technical Abstract: The use of a spring-wheat, corn, soybean rotation has become more widespread in dry-land cropping systems in the northern Great Plains of the United States. But this region experiences extreme variability in climate, which is projected to increase in the future, and little is known about how weather changes impact this crop rotation in terms of carbon and water balances. To address this research gap, we analyzed micrometeorological and eddy covariance flux data over two rotation cycles (2016-2021) through a spring-wheat, corn soybean rotation in a no-till, rainfed field managed according to prevailing local practices. Using linear and quadratic regression models, we found a negative correlation between vapor pressure deficit (VPD) and soil moisture, which impacted net-ecosystem production (NEP) and gross ecosystem production (GEP) more than precipitation. Results also indicated that evapotranspiration (ET) across dormant season and growing seasons by three crops (i.e., 12 crop-seasons) was mainly determined by VPD during the dormant season but high ET values were maintained with increasing VPD during the growing season. Low precipitation (i.e., corn and soybean in 2020 and 2021, respectively) decreased soil moisture which limited ET, NEP, and GEP in the growing seasons. These results imply that anticipated increases in evaporative demand due to elevated temperatures and/or low humidity in conjunction with drought may necessitate wider adoption of conservation agricultural practices, such as planting cover crops or residue retention, that enhance soil moisture recharge during the dormant season.