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

Abstract

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.

Effect of Soil Texture on Water Movement of Porous Ceramic Emitters: A Simulation Study

“…In general, system design parameters must be determined by infiltration experiments under different working conditions in order to determine the infiltration characteristics of subsurface irrigation emitters (cumulative infiltration, wetting front, and soil water content distribution) [6]. Emitter infiltration characteristics are affected by many factors, such as soil texture, bulk density, initial water content, emitter installation, buried depth, and emitter characteristics (structure size, design discharge, and working pressure head) [7]. The discharge of clay pots in soil is greatly affected by the pot porosity [8].…”

“…Emitter discharge gradually stabilized after 12 h, the working pressure head on the ceramic emitter increased, and the stabilized discharge also increased. Wang et al [7] simulated the infiltration characteristics of clay pipes under negative pressure conditions and found that the larger the negative working pressure head and hydraulic conductivity of the clay pipes, the greater the cumulative soil infiltration. HYDRUS-2D can accurately simulate the infiltration characteristics of ceramic pipes and pots under a working pressure head of 0-200 cm [5].…”

Steady Flow from an Array of Subsurface Emitters: Kornev’s Irrigation Technology and Kidder’s Free Boundary Problems Revisited

“…We use several default HYDRUS options: iteration criteria, time step controls, an initial (at t = 0) pressure head of − 100 cm throughout the modeled 2D domains, the VGM capillary pressure and phase permeability functions, and the soil catalog. Wang et al (2017), among many others (see also Šimůnek et al 2016), used HYDRUS for modeling SI from a PP either as a solitary emitter, i.e., without overlapping of flows generated by laterally neighboring emitters, or as a system of parallel emitters. In their conceptual HYDRUS models, they assumed a "free drainage" or specified negative pressure head boundary condition at the bottom of the flow domain.…”

“…6i) illustrates the water table position, in particular, d = 46 cm, m = 40 cm. Similarly to Ashrafi et al (2002) Siyal andSkaggs (2009), andWang et al (2017), we can include a thin pipe wall made of a low permeable clay.…”

Effects of Textural Layering on Water Regimes in Sandy Soils in a Desert-Oasis Ecotone, Northwestern China

“…Many approaches have been proposed for analyzing the characteristics of infiltration processes in textural layered soils. Common methods for acquiring soil hydrological processes include laboratory tests (Al-Maktoumi, et al, 2015), field experiments (Rimon, et al, 2007;Gvirtzman, et al, 2008), and simulations by current commercially available soil water models such as HYDRUS 1D or 2D (Wang, et al, 2017;Wang, et al, 2018), and theoretical models such as the Green-Ampt model (Mohammadzadeh-Habili and Heidarpour, 2015;Deng and Zhu, 2016). Preferential flow is a common phenomenon in the desertoasis ecotone (Yan and Zhao, 2016;Zhang, et al, 2017b), however, HYDRUS failed to simulate the complexity of flow processes observed in dry soils, specifically confounding preferential flow (Hardie, et al, 2013).…”