Further investigating the performance of crop water stress index for maize from baseline fluctuation, effects of environmental factors, and variation of critical value

Authors: ZHANG, LIYUAN - Jiangsu University; Zhang, Huihui; ZHU, QINGZHEN - Jiangsu University; NIU, YAXIAO - Jiangsu University

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2023
Publication Date: 5/16/2023
Citation: Zhang, L., Zhang, H., Zhu, Q., Niu, Y. 2023. Further investigating the performance of crop water stress index for maize from baseline fluctuation, effects of environmental factors, and variation of critical value. Agricultural Water Management. 285. Article e108349. https://doi.org/10.1016/j.agwat.2023.108349.
DOI: https://doi.org/10.1016/j.agwat.2023.108349

Interpretive Summary: The empirical (CWSI_E) and theoretical (CWSI_T) crop water stress index calculation methods were investigated on estimating maize crop water stress, grain yield and water use efficiency (WUE). Canopy temperatures were measured from maize plots at different irrigation levels during the 2013 and 2015 growing seasons at the Limited Irrigation Research Farm, Greeley,CO. The in-season and seasonal changes of non-water-stressed baseline (NWSB) and non-transpiration baseline (NTB), the effects of environmental factors, and the estimation performances of water stress, grain yield, and WUE were analyzed. Results show significant correlations with vapor pressure deficit (VPD) were found for two baselines, however, the distributions with the changes of VPD and in-season and seasonal changes of NWSB and NTB were different between two methods. Specifically, neither growth stage nor growing season significantly affects the baselines of CWSI_E, indicating that the baselines of CWSI_E were more stable than those of CWSI_T. The lower baselines and narrower space between NWSB and NTB were more likely to be observed in CWSI_T. The greater CWSI values were observed for CWSI_T because of the relatively narrower space between NWSB and NTB. Both methods were suitable to estimate maize water stress when VPD is greater than 1.5 kPa. Both methods could track maize water stress and estimate grain yield and WUE.

Technical Abstract: The empirical (CWSI_E) and theoretical (CWSI_T) crop water stress index calculation methods were investigated in-depth on estimating maize crop water stress, grain yield and water use efficiency (WUE). Fifteen-minute averages of canopy temperatures were measured from maize plots at different irrigation levels during the 2013 and 2015 growing seasons at USDA-ARS, Limited Irrigation Research Farm, Greeley, Colorado. The in-season and seasonal changes of non-water-stressed baseline (NWSB) and non-transpiration baseline (NTB), the effects of environmental factors, and the estimation performances of water stress, grain yield, and WUE were analyzed. Results show significant correlations (p<0.001) with vapor pressure deficit (VPD) were found for two baselines, however, the distributions with the changes of VPD and in-season and seasonal changes of NWSB and NTB were different between two methods. Specifically, neither growth stage nor growing season significantly affects the baselines of CWSI_E, indicating that the baselines of CWSI_E were more stable than those of CWSI_T. The lower baselines and narrower space between NWSB and NTB were more likely to be observed in CWSI_T than CWSI_E. The greater CWSI values were observed for CWSI_T because of the relatively narrower space between NWSB and NTB. Both methods were suitable to estimate maize water stress when VPD is greater than 1.5 kPa. Both methods could track maize water stress with R2 of 0.55 for CWSI_E and 0.49 for CWSI_T (n=236) with sap flow measurements, and could estimate grain yield with the highest R2 of 0.95 and WUE with the highest R2 of 0.87 (n=24).