Model for predicting soil water status based on the canopy-air temperature differential in apple orchard

This study was conducted to develop a model for predicting soil water status in the apple orchard based on canopy-air temperature differential(ΔT) at 14∶00 o'clock in the fine days during the growing season in combination of observed air temperature and relative available soil water contend in 0～80 cm soil layer in 2003～2004. Relative available water content(RAW) in 0～80 cm depth layer was chosen as the index of soil water status. The experiment was carried out in the hilly land of North China from 2002 to 2005. The results showed that: RAW and ΔT were significantly correlated(r=－0.819, n＝50), according to the data in 2003～2004, and were tested with the measured data in 2002 and 2005, indicating that the measured RAW was highly correlated with the simulated data(r=0.9137, n=40). Thus, the model can provide a valuable tool for diagnosing soil water status for apple trees. Based on this model, the critical ΔT could be calculated according to the critica1 RAW, and if the measured ΔT is larger than the critical ΔT, irrigation should be carried out in the orchard.