Detection of crop transpiration and water stress by temperature-related approach under field and greenhouse conditions

A new method for estimating crop transpiration and crop water stress index (CWSI) by using a temperature-related approach was developed and verified i n this study. In the proposed method, 3 temperatures and a few meteorologic al variables (net radiation and humidity) are required. The 3 temperatures include sunlit leaf temperature, imitation leaf temperature, and air temper ature. The imitation leaf refers to an artificial leaf without transpiratio n. The major advantage of the proposed method is that plant correction fact ors, empirical coefficients, and canopy and aerodynamic resistances are not required. Experiments for verification were conducted in a sandy field wit h sorghum crop and in a greenhouse with melon crop. Data obtained by the pr oposed method were compared with the amount of transpiration determined wit h lysimeters, soil water status determined by TDR, and CWSI estimated by Ja ckson's method. The calculated transpiration by the proposed method was con sistent with the results obtained with lysimeters, with a regression coeffi cient r(2)=0.88. Values of CWSI calculated by the proposed method were in a greement with Jackson's CWSI, with a regression coefficient approximately e qual to 1. These results indicate that the proposed method can be applied t o estimate crop transpiration and water stress index under both field and g reenhouse conditions.