A bidirectional model for simulating soil water flow and salt transport under mulched drip irrigation with saline water

- Model for water flow and salt transport under mulched drip irrigation is presented.
- Wetting soil volume is affected by plastic mulching and irrigation amount.
- Soil water content parallel to drip tubing is higher than that perpendicular.
- Soil salt concentration was high at the edges of the wetting front.

Here, we present a mathematical model for simulating both soil water flow and salt transport in two directions (perpendicular and parallel to the drip tubing) under mulched drip irrigation with saline water. We evaluated the effectiveness of this model by comparing the simulated values with observed data from the field experiment (one treatment with three replications was imposed with irrigation water electrical conductivity of 4.0 dS m−1 and amounts of 2400 m3 ha−1 under mulched drip irrigation system). The results demonstrated that the model performed reliably in the simulation of water flow and salt transport under field conditions. In addition, the model was also used to simulate the spatial distribution patterns of soil water and salt in the two directions in relation to different treatments of irrigation quantity and quality. The simulation demonstrated that the volume of wetted soil was affected by both the plastic mulching and irrigation amount. The wetted region was expanded to the middle of the plastic mulching when the irrigation amount was high and the uniformity of irrigation increased with increasing irrigation volume. Soil water content in the direction parallel to the drip tubing was higher than that perpendicular to the tubing at the same distance, indicating that the wetting fronts overlapped more rapidly in the direction parallel to the drip tubing. The soil salt concentration was high at the edges of the wetting front, with a fairly large desalinated area immediately underneath and adjacent to the drippers. The model presented here offers an efficient approach to investigating the mechanisms underlying soil water flow and salt transport and for designing mulched drip irrigation systems with saline water.