| On the basis of comprehensive analysis of climatic factors, biological features and soil humilities, the biological characteristics of a crop were thought to hide in the changes of its rhizosphere moisture to some extent. Meantime, crop index was introduced considering the field evapo-transpiration under actual circumstances and thought to contain the biological characteristics of the crop to some extent. Based on what had been mentioned above, and using perennial data collected by the field experiments, a model to compute the actual evapo-transpiration in the field of rain-fed wheat was established and verified with the evapo-transpirations directly measured in the field. The results revealed that the model had high precision with its relative error ranging within ±10% and could be used as another method to compute the field evapo-transpiration. |