Modelling soil water and its uniformity under linear-move sprinkler irrigation

Abstract

Crop yield is strongly affected by soil water distribution near the root zone. The redistribution of soil water in sprinkler irrigation results in higher soil water uniformity (CU_s) than irrigation uniformity (CU_i). A soil water transport model for sprinkler irrigation based on the COMSOL-2D model has been constructed and validated to investigate soil water movement and redistribution. Furthermore, the relationships between CU_s, soil hydraulic parameters, and sprinkler irrigation parameters has been analysed. The results showed that 1) the residual distributions of the vertical wetting front (VWF) and soil water content (SWC) were in the ranges of −0.04–0.05 and −0.09–0.10, respectively, with mean values close to 0 and R² greater than 0.85, indicating that model predictions were reliable; 2) the lower CU_i was, the lower CU_s, the lower the VWF transport rate, and the higher the chances of deep percolation; 3) the VWF transport rate depended on soil texture (loam > clay loam > silty clay), but CU_s was highest for silty clay (76.43 %), medium for clay loam (67.48 %), and lowest for loam (60.36 %); 4) the wetted area and VWF transport distance were positively correlated with soil water at the same moment; and 5) dimensional analysis showed that CU_i had the greatest effect on CU_s, followed by saturated hydraulic conductivity and water transport time. This study provides a theoretical basis for adequate values of CU_i for optimal management of linear-move sprinkler irrigation systems.