Estimation of net interception loss by crop canopy under sprinkler irrigation based on energy balance

Transpiration suppression by evaporation of canopy intercepted water was measured using heat balance sap flow during two growing seasons of winter wheat and summer corn to evaluate the canopy interception loss under sprinkler irrigation, compared with surface irrigation. The experimental results demonstrated that crop transpiration was obviously suppressed by microclimate modification resulted from sprinkler irrigation. For one irrigation event, the amounts of transpiration suppression caused by evaporation of the canopy intercepted water were 1.65～4.09 mm and 0.50～2.75 mm from the beginning of spraying to the vanishing of transpiration suppression for winter wheat and summer corn, respectively. Based on energy balance, net canopy interception loss for sprinkler irrigation was determined with Bowen-ratio energy balance technique under sprinkler irrigation. The amount of net interception loss by winter wheat canopy was less than 0.1mm, and the loss intercepted by summer corn canopy varied from 1 to 2 mm, accounting for 4.3%～6.5% of sprinkler irrigation amounts.