Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/22/2016
Publication Date: N/A
Technical Abstract: The crop water stress index (CWSI) is an important tool for monitoring and quantifying crop water stress and has also been used for irrigation scheduling. In this study, CWSI was estimated by an empirical model and two theoretical models using an estimated and constant aerodynamic resistance, respectively. The accuracy and consistency of CWSI for evaluation of maize water status was assessed using a three-year experimental dataset which was obtained at the USDA-ARS Limited Irrigation Research Farm (LIRF), Greeley, Colorado. Non-water-stressed baselines were developed for each year and were statistically significantly different (p<0.05) due to annual climate variation. The variability of daily CWSI calculated by different baselines was large (maximum±0.15) and decreased with increasing vapor pressure deficit (VPD). The empirical CWSI showed good agreement with observed sap flow measurements but exhibited fluctuations, especially under lower VPD conditions. The theoretical CWSI with an estimated aerodynamic resistance did not show statistical differences between irrigation treatments and underestimated CWSI for water-stressed crop conditions while the theoretical CWSI with a constant aerodynamic resistance indicated accuracy and consistency with the sap flow measurements. The theoretical model with a constant aerodynamic resistance appears to be the most promising approach for CWSI calculation; however, if meteorological measurements (e.g., net radiation and wind speed) are not available, then the empirical CWSI approach could be used with caution.