Modeling sprinkler efficiency with consideration of microclimate modification effects

Irrigation efficiency is an important consideration for selecting a suitable irrigation method in arid and semiarid regions. Crop canopy interception and wind drift may reduce sprinkler efficiency. However, the evapotranspiration suppression resulting from temperature reduction and humidity increase in sprinkler-irrigated fields versus non-irrigated fields, defined as microclimate modification in this article, imposed a positive effect on sprinkler efficiency. In this study, a sprinkler efficiency model based on the Cupid program was proposed for considering the effects of microclimate modification. The air temperature, relative humidity, plant transpiration, soil evaporation and sprinkler efficiency during the irrigation season of corn in the North China Plain were simulated using the model. The results indicated that the microclimate within the sprinkler-irrigated field could be modified during irrigation, and the effects continued for 10–20 h after the application finished. When evapotranspiration suppression was considered, sprinkler efficiency could be improved by 5 percentiles versus non-irrigated fields. A sensitivity analysis of sprinkler efficiency was conducted by classifying the input variables of the model into three categories: constant, hourly and daily variables. It was found that the sprinkler efficiency was only generally sensitive to the leaf thermal emissivity for all constant and daily variables investigated. The sensitivity to hourly variables was greatly dependent upon the specific soil, plant and weather conditions during an irrigation event.