Wang et al. (2026) Optimal groundwater depth thresholds for sunflower in salt-affected farmland: A process-based modeling approach across hydrological years in the Hetao Irrigation District

Identification

• Journal: Agricultural Water Management
• Year: 2026
• Authors: Zhipeng Wang, Xiangping Wang, Yuhang Wang, Changcheng He, Zhang Wen, Yulong Jiang, Wenping Xie, Xuan Yu, Rongjiang Yao
• DOI: 10.1016/j.agwat.2026.110181

Research Groups

• State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, China.
• China University of Geosciences, China.
• Inner Mongolia University of Science & Technology, China.

Short Summary

This study integrates field experiments with the Agro-Hydrological & Chemical (AHC) simulator to determine optimal groundwater depth (GWD) thresholds for sunflower cultivation. The research identifies specific GWD ranges for dry, normal, and wet hydrological years that balance maximum crop yield with effective soil salinity control in the Hetao Irrigation District.

Objective

• To quantify the impact of groundwater depth and salinity on root-zone water-salt dynamics and sunflower yield.
• To identify critical GWD thresholds for desalination and derive Pareto-optimal GWD strategies for different hydrological years using multi-objective optimization.

Study Configuration

• Spatial Scale: Field-scale experimental plots in Xinjian Village, Wuyuan County, Hetao Irrigation District (HID), China (41°5'N, 108°21'E).
• Temporal Scale: Two growing seasons (2023–2024) for field validation; historical meteorological analysis spanning 1957–2023 for hydrological year classification.

Methodology and Data

• Models used: AHC (Agro-hydrological & chemical and systems simulator) for 1D vertical water and solute transport; NSGA-II (Non-dominated Sorting Genetic Algorithm II) for multi-objective optimization; Rosetta pedotransfer function for initial soil hydraulic parameters.
• Data sources: Field-measured soil moisture, electrical conductivity (EC1:5), and sunflower yield; meteorological data from the Linhe station (Station ID: 53513); historical rainfall data from the National Oceanic and Atmospheric Administration (NOAA).

Main Results

• Flux Dynamics: Upward water flux from groundwater approaches zero at approximately 3.0 m depth, while upward salt flux becomes negligible at depths between 1.5 m and 1.9 m.
• Salinity Control: Root-zone salt accumulation is negatively correlated with GWD. The threshold GWD for effective desalination (where net salt change is zero) ranges from 1.48 m to 2.47 m, depending on groundwater Total Dissolved Solids (TDS) and rainfall patterns.
• Yield Response: Sunflower yield shows a unimodal response to GWD, as shallow depths increase salt stress and excessive depths cause water stress. The negative impact of groundwater mineralization on yield weakens significantly when GWD exceeds 1.8 m.
• Optimal Thresholds: The Pareto-optimal GWD ranges for sunflower growth under rainfed conditions (with pre-sowing irrigation) are:
  • Dry years: 1.18–1.28 m.
  • Normal years: 1.23–1.32 m.
  • Wet years: 1.37–1.45 m.

Contributions

• Establishes a process-based modeling framework that reconciles the competing objectives of agricultural productivity and soil salinity suppression in arid irrigation districts.
• Provides quantitative GWD management targets tailored to specific hydrological year types, offering a scientific basis for the design of subsurface drainage systems and water-saving irrigation strategies.
• Demonstrates the dual regulatory role of GWD in balancing capillary-driven salt ascent and groundwater contribution to crop water requirements.

Funding

• Development Program of Inner Mongolia Autonomous Region (Reference code: NMKJXM202401–01).

Citation

@article{Wang2026Optimal,
  author = {Wang, Zhipeng and Wang, Xiangping and Wang, Yuhang and He, Changcheng and Wen, Zhang and Jiang, Yulong and Xie, Wenping and Yu, Xuan and Yao, Rongjiang},
  title = {Optimal groundwater depth thresholds for sunflower in salt-affected farmland: A process-based modeling approach across hydrological years in the Hetao Irrigation District},
  journal = {Agricultural Water Management},
  year = {2026},
  doi = {10.1016/j.agwat.2026.110181},
  url = {https://doi.org/10.1016/j.agwat.2026.110181}
}

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