Simulation of Soil Water and Salt Distribution Characteristics within Area between Drip Tapes under Mulched Brackish Water Drip Irrigation in Greenhouses

Film-mulched drip irrigation with brackish water should avoid soil salt accumulation to maximize the benefits of water-saving. However, soil leaching by rainfall or flood irrigation is lack under greenhouses condition, the partial inhibition of surface evaporation by film mulching combined with the wetted volume intersection due to double-point source drip irrigation exacerbates the irregularity of water and salt distribution in the area between drip tapes (ABDT), which is not conducive to the effective implementation of salt control measures. Therefore, taking the field experimental plot of mulched drip irrigation with the layout of "two films and two rows" as the research object, and using the HYDRUS _ 2D model to simulate the dynamic distributions of soil water and salt in ABDT based on the two-dimensional simulation domains considering different drip discharge fluxes (0. 5 ~3. 0 L/h) and bare soil spacing between films (0 ~ 50 cm). The results indicated that the established model can accurately describe the water and salt distribution in ABDT, and reducing the horizontal distance from the emitter could obtain a high simulation accuracy. As the bare land between the films was decreased from 50 cm to 0 cm, the average moisture content of the soil in ABDT was increased from 25.12 cm3 /cm3" to 28. 76 cm3 /cm3, and the average soil solute concentration in ABDT was decreased from 9. 53 g/L to 6. 25 g/L. The effect of drip discharge fluxes on soil water-salt distribution in ABDT was relatively low, the maximum differences in soil volume moisture content and salt mass concentration between treatments with discharge fluxes of 0.5 h/L and 3.0 h/L were only 0.14 cm3 /cm3 and 0. 22 g/L, respectively, and both occurred in the bare soil spacing between films of 50 cm. Additionally, after long-term dry-wet alternation, salt accumulated on the outside of the drip belt might diffuse inward to ABDT, and with the decrease of bare soil spacing between films, the horizontal position of the lowest soil salinity would move from the location of dripper to ABDT. Findings of this research can provide a theoretical basis for selecting suitable low-salinity planting locations for crop cultivation in greenhouse condition. © 2023 Chinese Society of Agricultural Machinery. All rights reserved.