Experimental study on crop evaportranspiration model based on SPAC system

The canopy temperature, land surface temperature and leaf area index of cotton, winter wheat and summer corn in different growth periods were determined basing on the field experiment in the year of 2004 and 2005. The model of crop evaportranspiration was established on the foundation of the local meteorological data, energy balance equation and aerodynamic equation, and calculated values of the crop evapotranspiration model were compared with actual evapotranspiration of cotton, winter wheat and summer corn in different growth speriods. The results show that the calculating values of the crop evaportranspiration model not only indicate the variation rule of these three kinds of crop evaportranspiration in different growth periods, but also indicate relatively error of the average values between calculating value and actual evapotranspiration with 8.46%, 4.76% and 12.85% in 2004 respectively; 3.42%, 1.65% and 0.84% in 2005 respectively. So the model of crop evaportranspiration can be used to calculate crop evaportranspiration, and it also provides the theoretical foundation for monitoring the soil moisture and calculating the crop water stress index.