Simulation of water balance and irrigation strategy of typical sand-layered farmland in the Hetao Irrigation District, China

Rational irrigation plays an important role in increasing crop yield and reducing water use. With a typical sand-layered farmland in the Hetao irrigation district as an example, field experiments were conducted during the growth period of maize, and a numerical model of soil water movement was applied to explore the field evapotranspiration, crop water consumption and soil water transport in the sand-layered soil. CropWat 8.0 software was applied to formulate the irrigation schedule under the fixed irrigation interval in each growth stage of maize. The soil water movement in sand-layered soil under different irrigation schedules was simulated by the HYDRUS-1D model. Results show that the HYDRUS-1D model could well simulate the soil water movement during the growth period of crops in the typical sand-layered farmland. In addition, the deep percolation loss of water could be reduced by approximately 20.4–37.6% with appropriate increase in the irrigation frequency and reduction in the irrigation quota. However, under the minimum irrigation interval, there were still 19.5% of irrigation water and rainfall lost by seepage through the deep sand layer. The water stress in the rhizosphere during the mid-stage of crop growth was only 13.9 mm with the irrigation frequency as every 10 days (I10), while that was 107.97 mm with the irrigation frequency as every 25 days (I25). The maximum ratio of actual transpiration rate of crops to actual evapotranspiration of the land was 73.6% with I10 irrigation and the minimum was 63.4% with I25, indicating that increasing the irrigation frequency and reducing the irrigation quota each time are highly beneficial to increasing the water holding capacity for crop growth in the root zone in the sand-layered farmland. The study provides a basis for farmland water management in the arid and semi-arid areas.