Rules of soil evaporation and millet evapotranspiration in rain-fed region of Loess Plateau in Northern Shaanxi

For improving precipitation use efficiency of millet in rain-fed region of Loess Plateau, the middle weighing lysimeter, micro-lysimeter and biological indicators were combined in this experiment to determine the soil evaporation and millet evapotranspiration during the whole growing period of millet in Liudaogou watershed of Shenmu County. The results showed that the Logistic model could simulate the growing processes of millet height and coverage, the correlation coefficients of simulated and measured values reached 0.99. Total precipitation was almost equal to the water consumption of millet, but from heading to filling stage millet suffered water stress. In the whole growing period of millet, about 44% of the total field evapotranspiration was consumed by the soil evaporation. There were significant exponential function relations between leaf area index, soil moisture at in 0-10 cm depth and the ratio of evaporation and evapotranspiration, the correlation coefficients were higher than 0.8. The study can provide theoretical support for rational use of limited water resources and improvement of water use efficiency in rain-fed region of Loess Plateau in Northern Shaanxi.