Water use efficiency of croplands as affected by cropping systems and climate in a long-term study in the midwestern of United States

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

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/17/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The accelerated global population growth and water scarcity are raising concerns about the ability of the agricultural system to meet the growing demand for food, fuel, feed and fiber in the forthcoming decades. These concerns highlight the necessity of a more efficient use of water resources in agricultural production, particularly under the current global change scenario. Long-term monitoring of major cropping systems offers opportunities to accurately evaluate crop water use and its interaction with climate, informing the development of future management strategies to enhance food security at local to global scales. In this study, we used 20 years of observed data from three sites in Eastern Nebraska (USA) to quantify the changes to yield (Y, estimated from yearly inventories), evapotranspiration (ET, estimated from three Eddy flux towers), and water use efficiency (WUE, as the ratio between Y and ET) and their interaction with climate under three major cropping systems in the western US Corn Belt (irrigated continuous maize, irrigated maize soybean rotation, and rainfed maize soybean rotation). Results showed significant differences between irrigated and rainfed sites while there was no significant effect of crop rotation. Irrigation increased Y, ET and WUE by 27.6%, 11.8%, and 18.4% respectively in maize rotation and 12.9%, 5.1%, and 7.4% respectively in soybean rotation. These differences were likely related to crop photosynthetic activity, which is directly linked to seasonal leaf area index and biomass that determine crop seasonal water use and productivity. Yield was highly correlated with WUE and affected its temporal pattern while the WUE-ET correlation was non-significant. Vapor pressure deficit (VPD) was negatively correlated with Y in maize years and therefore was determinant in maize’s WUE, though ET exhibited the highest negative correlation with WUE in the irrigated sites. For soybean, soil water content (SWC) showed the highest correlations with Y and WUE, though negative in the irrigated site and positive in the rainfed. These results enhance our understanding of water productivity, the plant-atmosphere exchange and the interaction with climate. Such understanding is crucial to develop sustainable cropping systems that meet the growing demand for food under current and anticipated future climate variability and change.