Crop water stress parameters for turfgrass and their environmental dependability

Abstract

The concept of crop water stress index (CWSI) was explored using empirical and theoretical models to evaluate bermudagrass water status. The empirical methods were simplifications of the crop energy balance equation. Measured field data were employed to develop the empirical CWSI parameters. Field data were collected from turf plots under three levels of irrigation for the 1986 growing season in Tucson, Arizona. The simplest empirical model of Idso gave the highest variance in estimates of CWSI for all treatments with the estimates being highly influenced by net radiation. An improved empirical model was developed when net radiation was included in the statistical analysis of the canopy temperature minus air temperature limits. In general, the most accurate estimates of CWSI were obtained by using the energy balance equation with constant values of potential canopy and aerodynamic resistances. Various methods were used to evaluate these resistances. Further research is needed to test the perfomance of the theoretically-derived CWSI and to develop more general methods of evaluating the resistances.