Wang et al. (2025) A novel method to optimize the limited irrigation schedule for cotton: HYDRUS-triggered irrigation simulation and plant water deficit index threshold analysis

Identification

• Journal: Industrial Crops and Products
• Year: 2025
• Date: 2025-12-19
• Authors: Hang Wang, Wenting Qi, Xiaopeng Ma, Jiandong Wang, Chuanjuan Wang, Shuji Wang
• DOI: 10.1016/j.indcrop.2025.122484

Research Groups

• Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing, China
• Western Agricultural Research Center, Chinese Academy of Agricultural Sciences, Changji, Xinjiang, China
• State Key Laboratory of Efficient Utilization of Agricultural Water Resources, CAU/CAAS, Beijing, China
• College of Water Conservancy Science and Engineering, Taiyuan University of Technology, Taiyuan, Shanxi, China
• Institute of Soil Fertilizer and Agricultural Water Conservation, Xinjiang Academy of Agricultural Sciences, Urumqi, Xinjiang, China
• School of Water Conservancy and Hydroelectric Power, Hebei University of Engineering, Handan, Hebei, China

Short Summary

This study developed a novel method to optimize limited drip irrigation for cotton in northern Xinjiang, China, by integrating field experiments with HYDRUS simulations and Plant Water Deficit Index (PWDI) threshold analysis, identifying optimal irrigation lower limits for key growth stages under specific water quotas.

Objective

• To assess the availability of PWDI based on root-weighted soil moisture calculations to guide drip-irrigated cotton under film mulch.
• To clarify the PWDI threshold of key growth stages based on the effect of PWDI on the photosynthetic characteristics of cotton at different growth stages.
• To propose a new method for irrigation schedule optimization coupled with HYDRUS simulation and PWDI threshold analysis.
• To propose an optimized irrigation scheme for cotton cultivation in northern Xinjiang, aiming to minimize water stress duration while adhering to strict water allocation constraints through precision irrigation management.

Study Configuration

• Spatial Scale: Field experiments conducted at Changji Comprehensive Experimental Station (87.33°E, 44.27°N) in Changji Hui Autonomous Prefecture, Xinjiang Uygur Autonomous Region, China. Soil layers analyzed were 0–80 cm.
• Temporal Scale: Field experiment from April to October 2023. Numerical simulations spanned 122 days, covering the period from pre-squaring irrigation through boll maturation.

Methodology and Data

• Models used: HYDRUS (version 2.05) for simulating soil water movement based on the Richards equation and Feddes model for root water uptake; nonlinear least squares optimization for PWDI parameter (ρ).
• Data sources:
  • Field experiments in Changji, Xinjiang, China (2023).
  • Soil moisture content monitored using soil temperature and humidity sensors (TEROS12, METER) at 20 cm, 50 cm, and 80 cm depths, calibrated with the drying method.
  • Plant photosynthetic parameters (net photosynthetic rate, stomatal conductance, transpiration rate, intercellular CO2 concentration, atmospheric CO2 concentration) measured with a portable photosynthesis instrument (yaxin-1105, Yaxin).
  • Actual transpiration rate determined by sap flow meter (SFM1, ICT International) using the heat ratio method and water balance method for the bud stage.
  • Leaf area index (LAI) measurements.
  • Soil particle size analysis (MS2000 particle size analyzer) and characterization (USDA classification).
  • Local groundwater quality parameters (pH, electrical conductivity, sodium adsorption ratio).

Main Results

• An optimal value of ρ = 0.12 was identified for the soil water stress correction coefficient γ(h), resulting in a concave function.
• The estimated PWDI method showed satisfactory agreement with measured values (coefficient of determination R² = 0.68, root mean square error RMSE = 0.12, mean absolute percentage error MAPE = 18.86 %).
• The net photosynthetic rate (A) was the most sensitive photosynthetic indicator to PWDI changes, followed by the transpiration rate (Tr) and stomatal conductance (gs).
• Appropriate PWDI thresholds for cotton were determined to be 0.48 for the squaring stage and 0.52 for the boll stage.
• The HYDRUS model accurately simulated soil moisture dynamics across various irrigation treatments (R² range 0.47–0.58, RMSE range 0.01–0.03 cm³ cm⁻³, MAPE range 4.78–7.74 %).
• Boll-stage irrigation management was found to be the primary factor regulating PWDI dynamics.
• Under specific total irrigation limits for cotton in northern Xinjiang:
  • For a 420 mm limit, the optimal scheme was S70B50 (squaring stage lower limit 70 % field capacity (FC), boll stage lower limit 50 % FC), resulting in 60 cumulative days below PWDI thresholds.
  • For a 450 mm limit, the optimal scheme was S65B55 (squaring stage lower limit 65 % FC, boll stage lower limit 55 % FC), resulting in 67 cumulative days below PWDI thresholds.
  • For a 480 mm limit, the optimal scheme was S70B55 (squaring stage lower limit 70 % FC, boll stage lower limit 55 % FC), resulting in 69 cumulative days below PWDI thresholds.
• The optimized irrigation strategy reduced total irrigation by an average of 9.4 % (from 480 mm to 420–450 mm) while decreasing non-stress days by only 8.0 %.

Contributions

• Established a reliable PWDI estimation method and a HYDRUS-based irrigation trigger model specifically for mulched drip-irrigated cotton.
• Quantitatively clarified the response of cotton photosynthetic characteristics to PWDI thresholds at different growth stages, identifying specific thresholds (0.48 for squaring, 0.52 for boll stage) that improve the timeliness and accuracy of irrigation.
• Proposed a novel, integrated method for optimizing limited irrigation schedules by coupling HYDRUS simulation with plant physiological responses via PWDI threshold analysis.
• Provided concrete, optimized irrigation schemes for cotton cultivation in northern Xinjiang under strict water allocation constraints (420–480 mm), aiming to minimize water stress duration during critical growth stages.
• Demonstrated an improved approach to water management that considers both soil water dynamics and crop physiological traits, offering significant reference value for water-scarce regions.

Funding

• Key R & D Program of Xinjiang Uygur Autonomous Region (2023B02024–1, 2023B02014–3)
• Changji Technology Innovation Team project (2023CT08)
• Science and Technology Innovation Project of Chinese Academy of Agricultural Sciences (CAAS-ZDRW202417)
• Xinjiang Uygur Autonomous Region "Tianchi Talents" introduction plan (2023–2025)
• Natural Science Fund Project of Hebei Province (E2024402034)

Citation

@article{Wang2025novel,
  author = {Wang, Hang and Qi, Wenting and Ma, Xiaopeng and Wang, Jiandong and Wang, Chuanjuan and Wang, Shuji},
  title = {A novel method to optimize the limited irrigation schedule for cotton: HYDRUS-triggered irrigation simulation and plant water deficit index threshold analysis},
  journal = {Industrial Crops and Products},
  year = {2025},
  doi = {10.1016/j.indcrop.2025.122484},
  url = {https://doi.org/10.1016/j.indcrop.2025.122484}
}