Long-term croplands water productivity in response to management and climate, in Western US corn belt

Authors: KHORCHANI, MAKKI - University Of Nebraska; AWADA, TALA - University Of Nebraska; Schmer, Marty; Jin, Virginia; Birru, Girma; DANGAL, SHREE - University Of Nebraska; SUYKER, ANDY - University Of Nebraska; Freidenreich, Ariel

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2023
Publication Date: 12/23/2023
Citation: Khorchani, M., Awada, T., Schmer, M.R., Jin, V.L., Birru, G.A., Dangal, S.R., Suyker, A., Freidenreich, A.S. 2023. Long-term croplands water use efficiency in response to management and climate, in Eastern Nebraska's US corn belt. Agricultural Water Management. Volume 291. https://doi.org/10.1016/j.agwat.2023.108640.
DOI: https://doi.org/10.1016/j.agwat.2023.108640

Interpretive Summary: Evaluating water use efficiency over time can provide insights on crop productivity and how management practices relates to increasing food and water security. In this study, we used data collected over a 20-year period (2001-2020 years) to investigate the interannual variability in yield, evapotranspiration, and water use efficiency (ratio of yield and evapotranspiration), and their response to climate in three different crop rotations in Eastern Nebraska's US Corn Belt. The three crop rotations were irrigated continuous corn, irrigated corn-soybean rotation, and rainfed corn-soybean rotation. Irrigation increased grain yield, evapotranspiration and water use efficiency by 27.6%, 11.8%, and 18.4%, respectively in corn in rotation and 12.9%, 5.1%, and 7.4% respectively in soybean in rotation, relative to rainfed. We found that grain yield was highly correlated with water use efficiency. For irrigated soybean, soil water content had the highest correlations with grain yield and water use efficiency. These results are important for developing sustainable, productive, and resilient cropping systems that meet the growing demand for food under current and anticipated future climate variability and change.

Technical Abstract: The projected global population growth and increasing water scarcity are raising concerns about the resilience of agricultural systems to meet the growing demands for food, fuel, feed and fiber in the coming decades. Long-term monitoring of crop yield and water use across major cropping systems offer opportunities to evaluate crop performance and their response climate change, which can inform the development of improved management strategies aimed at enhancing resilience, and food and water security at local and global scales. In this study, we used data collected over a 20-year period (2001-2020 years) to investigate the interannual variability in yield (Y), evapotranspiration (ET), and water use efficiency (WUE, ratio of Y and ET), and their response to climate in three major cropping systems (crop rotations) located in Eastern Nebraska's US Corn Belt: irrigated continuous maize, irrigated maize-soybean rotation, and rainfed maize-soybean rotation. Our results showed significant differences (p < 0.05) in Y, ET, and WUE between irrigated and rainfed sites, while there was no significant effect of crop rotation on measured responses. Irrigation increased Y, ET and WUE by 27.6%, 11.8%, and 18.4%, respectively in maize in rotation and 12.9%, 5.1%, and 7.4% respectively in soybean in rotation, relative to rainfed site . We found that Y was highly correlated with WUE (maize: R=0.9, p<0.05; soybean: R=0.83, p<0.05) and affected its temporal pattern, while the WUE-ET correlation was non-significant. Vapor pressure deficit (VPD) was negatively correlated with Y in rainfed maize (R=-0.72, p<0.05) and therefore considered a determinant in its WUE (R=-0.7, p<0.05), while ET exhibited the highest negative correlation with WUE in the irrigated sites (R=-0.62, p<0.05). For soybean, soil water content (SWC) had the highest correlations with Y and WUE (irrigated: R=-0.77; rainfed: R=0.49, only significant in irrigated sites). Our findings emphasize the role of water availability for plant productivity and water use efficiency relative to crop rotation, especially in maize. These results are important for developing sustainable, productive, and resilient cropping systems that meet the growing demand for food under current and anticipated future climate variability and change.