Modeling Evapotranspiration and Crop Growth of Irrigated and Non-irrigated Corn under Warm Climate

Authors: Zhang, Huihui; Malone, Robert - Rob; Ahuja, Lajpat; Ma, Liwang; Anapalli, Saseendran; Marek, Gary; Gowda, Prasanna; Evett, Steven - Steve; Howell, Terry

Submitted to: World Congress of Soil Science
Publication Type: Abstract Only
Publication Acceptance Date: 4/5/2018
Publication Date: N/A
Citation: N/A

Interpretive Summary: Accurate quantification and management of crop evapotranspiration (ET) are critical to optimizing crop water productivity for both dryland and irrigated agriculture, especially in the semiarid regions of the world. In this study, four weighing lysimeters were planted to maize in 1994 with two fully irrigated and two non-irrigated for measuring crop ET in Bushland, Texas. The two fully irrigated lysimeters were used for calibrating the Root Zone Water Quality Model (RZWQM2) and the non-irrigated ones were reserved for model evaluation, in terms of leaf area index, biomass, soil water contents, and daily ET. The Nimah-Hanks approach in RZWQM2 was used for calculating actual crop water update (AT), and the Richards’ equation was used for actual soil evaporation (AE). The Shuttleworth and Wallace method (S-W) and ASCE Standardized alfalfa Reference ET plus crop coefficients (ASCE) were used to calculate potential ET (PET), which were partitioned into potential evaporation (PE) and potential transpiration (PT) based on leaf area index. As a result, four water stress factors were tested in the model against the lysimeter data, i.e., AT/SW-PT, AT/ASCE-PT, (AT+AE)/SW-PET, and (AT+AE)/ASCE-PET. Root Mean Squared Deviations (RMSDs) and relative RMSDs (RMSD/observed mean) values for leaf area index, biomass, soil water contents, and daily ET were within simulation errors reported earlier in the literature. For the two non-irrigated lysimeters, the simulated daily ET values were also reasonably close to the measured values, but were under-estimated during mid-growth stage. In general, water stress factor defined by (AT+AE)/SW-PET was better than other stress factors in simulations of non-irrigated corn biomass and grain yield. Additional studies of crops grown under dryland conditions using weighing lysimeters are needed to corroborate these findings and aid in the development of new water stress algorithms.

Technical Abstract: Accurate quantification and management of crop evapotranspiration (ET) are critical to optimizing crop water productivity for both dryland and irrigated agriculture, especially in the semiarid regions of the world. In this study, four weighing lysimeters were planted to maize in 1994 with two fully irrigated and two non-irrigated for measuring crop ET in Bushland, Texas. The two fully irrigated lysimeters were used for calibrating the Root Zone Water Quality Model (RZWQM2) and the non-irrigated ones were reserved for model evaluation, in terms of leaf area index, biomass, soil water contents, and daily ET. The Nimah-Hanks approach in RZWQM2 was used for calculating actual crop water update (AT), and the Richards’ equation was used for actual soil evaporation (AE). The Shuttleworth and Wallace method (S-W) and ASCE Standardized alfalfa Reference ET plus crop coefficients (ASCE) were used to calculate potential ET (PET), which were partitioned into potential evaporation (PE) and potential transpiration (PT) based on leaf area index. As a result, four water stress factors were tested in the model against the lysimeter data, i.e., AT/SW-PT, AT/ASCE-PT, (AT+AE)/SW-PET, and (AT+AE)/ASCE-PET. Root Mean Squared Deviations (RMSDs) and relative RMSDs (RMSD/observed mean) values for leaf area index, biomass, soil water contents, and daily ET were within simulation errors reported earlier in the literature. For the two non-irrigated lysimeters, the simulated daily ET values were also reasonably close to the measured values, but were under-estimated during mid-growth stage. In general, water stress factor defined by (AT+AE)/SW-PET was better than other stress factors in simulations of non-irrigated corn biomass and grain yield. Additional studies of crops grown under dryland conditions using weighing lysimeters are needed to corroborate these findings and aid in the development of new water stress algorithms.