Simulations of water movement and solute transport through different soil texture configurations under negative-pressure irrigation

摘要

This study examined the effects of different soil texture configurations on water movement and solute transport to provide a reliable scientific basis for the application of negative-pressure irrigation (NPI) technology. HYDRUS-2D was used to analyse water movement and solute transport under NPI. The main results are as follows: (a) HYDRUS-2D can be used to simulate water movement and solute transport under NPI, as there was good agreement between the simulated and measured values for water contents, NaCl concentrations, cumulative water infiltration, and wetting distances in the horizontal and vertical directions; the Nash-Sutcliffe efficiency coefficients were in the range of 0.94-0.97. (b) Layered soils have obvious effects on water movement under NPI. With the emitter position in the loam layer, when a coarse texture of loamy sand was present below the loam layer (namely, L-LS), irrigation water accumulated in the topsoil, and this led to an increase in evaporation compared with the homogeneous loam profile. However, fine texture silty loam or silty clay loam layers beneath the loam layer (namely, L-SiL or L-SiCL, respectively) was more conducive to water infiltration into the lower layer, and this increased the amount of water infiltration and simultaneously reduced the surface evaporation effectively. (c) Layered soils have obvious effects on solute transport under NPI, and salt accumulation will readily occur in the clay-rich soil layer at the interface. The maximum soil salt accumulation of L-LS occurred above the soil interface between the two soil layers with a value of 21.80 g/kg; however, for L-SiCL and L-SiL, the maximum salt accumulation occurred below the soil interface between the two soil layers, with values of 23.80 g/kg and 20.08 g/kg, respectively. (d) Interlayered soils showed remarkable changes in the water infiltration characteristics and salt-leaching intensities under NPI, and the properties for the soil profile with a silty loam interlayer were better than those for the soil profile with a silty clay loam interlayer. The soil profile with a loamy sand interlayer had the lowest amount of water infiltration, which resulted in reductions of the salt-leaching intensities. Thus, NPI is clearly not suitable for loamy sand soil. Overall, the results demonstrated that soil texture configurations affected water movement and solute transport under NPI. Therefore, careful consideration should be given to the use of NPI to achieve target soil water and solution conditions and reduce water loss.