Chen et al. (2025) Integrated modeling of crop growth with 2D soil water flow and solute transport considering dynamic root spatial distribution under film mulched drip irrigation

Identification

• Journal: Agricultural Water Management
• Year: 2025
• Date: 2025-12-13
• Authors: Shuai Chen, Zunqiu Xu, Chunying Wang, Songhao Shang
• DOI: 10.1016/j.agwat.2025.110069

Research Groups

• Department of Hydraulic Engineering, Tsinghua University, Beijing, China
• College of Water Resources, North China University of Water Resources and Electric Power, Zhengzhou, China

Short Summary

This study developed and validated a two-dimensional coupled model (WSP-2D) for simulating soil water flow, solute transport, and crop growth under film-mulched drip irrigation, incorporating dynamic root distribution and water flux through mulched film planting holes. The model accurately captured field observations and demonstrated the critical importance of dynamic root growth and surface water flux for accurate simulations of soil water, salt, and crop yield.

Objective

• To develop a two-dimensional integrated soil water-salt-crop model (WSP-2D) that considers water flux through planting holes of plastic film and dynamics of root growth under drip irrigation.
• To calibrate and validate the integrated model with data from a maize field experiment conducted in 2023 and 2024.
• To analyze the potential impacts of assuming no flux at the film-mulched zone and an unchanging root zone on the simulation accuracy of soil water and salt dynamics.

Study Configuration

• Spatial Scale: Field experiment conducted at Shuguang Experimental Station, Hetao Irrigation District, Inner Mongolia Autonomous Region, China (40°46′ N, 107°24′ E). Model domain was a 55 cm wide and 80 cm deep cross-section.
• Temporal Scale: Two-year field experiment (2023 and 2024) covering maize growing seasons (27 April to 17/18 September).

Methodology and Data

• Models used: WSP-2D (a newly developed coupled model), which integrates:
  • Richards equation for 2D soil water flow.
  • Advection-dispersion equation for 2D solute transport.
  • A crop growth module based on the EPIC (Environmental Policy-Integrated Climate) model.
  • Van Genuchten-Mualem (VG-M) model for soil hydraulic properties.
  • Feddes model for water stress, linear reduction for salt stress, or S-shaped function for water-salt stress in root water uptake.
  • Classical logistic growth function for dynamic root growth.
  • Implemented in MATLAB (Version 2012a).
• Data sources:
  • Two-year (2023-2024) field experiment data from a maize field under film-mulched drip irrigation in Northwest China.
  • Measurements included gravimetric soil water content, soil electrical conductivity (converted to salt content), leaf area index (LAI), aboveground biomass, root length density, and maize yield.
  • Soil physical properties (particle size, bulk density) from excavated soil profiles.
  • Meteorological data from the nearby Linhe weather station.
  • Irrigation water quality (total dissolved solids).

Main Results

• The WSP-2D model accurately simulated soil water content (R² > 0.90, NSE > 0.84), soil salt concentration (R² > 0.48, NSE > 0.40), leaf area index (R² > 0.90, NSE > 0.84), aboveground biomass (R² > 0.98, NSE > 0.95), and maize yield (relative errors < 1.3%) during calibration (2023) and validation (2024).
• Considering water flux (infiltration/evaporation) through planting holes of the mulched film significantly improved simulation accuracy. Ignoring this flux led to reduced NSE values for soil water content (e.g., from 0.91 to 0.77 in 2024) and increased RMSE for salt concentration (e.g., by 0.17-0.28 g L⁻¹). It also resulted in 5.8-6.8% lower simulated crop yields.
• Dynamic root growth simulation performed better than a fixed root distribution. Simulations with a fixed root distribution overestimated soil water content by up to 21.8% and underestimated salt concentration by up to 43.5% in the top layer (0-30 cm) of the root zone, while showing opposite tendencies in the lower root zone. This effect was most pronounced in the early and middle crop growth stages.
• Salt mainly accumulated in the upper 0-40 cm loam layer (above the sand layer) and in the soil beneath the plant row due to transpiration, highlighting the impact of layered soil profiles on salt distribution.

Contributions

• Development of a novel 2D integrated soil water-salt-crop model (WSP-2D) that explicitly accounts for two critical interactive processes: water flux through planting holes of mulched film and dynamic 2D root growth and distribution.
• Quantification of the significant impact of these processes on the accuracy of simulating soil water, salt dynamics, and crop growth/yield under film-mulched drip irrigation, demonstrating that commonly adopted simplifications (no flux through film, fixed root zone) lead to substantial errors.
• Provides a more realistic and robust tool for understanding and managing agro-eco-hydrological processes in film-mulched drip irrigated systems, particularly in arid and semi-arid saline environments with layered soils.

Funding

• National Key R&D Program of China (Grant No. 2021YFD1900600)
• National Natural Science Foundation of China (Grant No. 52209061)

Citation

@article{Chen2025Integrated,
  author = {Chen, Shuai and Xu, Zunqiu and Wang, Chunying and Shang, Songhao},
  title = {Integrated modeling of crop growth with 2D soil water flow and solute transport considering dynamic root spatial distribution under film mulched drip irrigation},
  journal = {Agricultural Water Management},
  year = {2025},
  doi = {10.1016/j.agwat.2025.110069},
  url = {https://doi.org/10.1016/j.agwat.2025.110069}
}