Rezaei et al. (2025) Modelling phosphorus and potassium dynamics in drip-irrigated potato systems using coupled agro-hydrological model

Identification

• Journal: Agricultural Water Management
• Year: 2025
• Date: 2025-10-24
• Authors: Meisam Rezaei, Kambiz Bazargan, Karim Shahbazi, Mostafa Marzi, Meysam Cheraghi
• DOI: 10.1016/j.agwat.2025.109920

Research Groups

• Soil and Water Research Institute, Agricultural Research, Education and Extension Organization, Karaj, Iran
• Ghent University (UGent)
• Flemish Institute for Technological Research of Belgium (VITO NV)

Short Summary

This study combined field experiments with coupled DSSAT and HYDRUS-2D models to investigate phosphorus (P) and potassium (K) dynamics in drip-fertigated potato systems under semi-arid conditions, revealing limited vertical mobility for both nutrients but greater lateral movement for K, and demonstrating that frequent, low-concentration fertigation significantly enhances nutrient availability and uptake efficiency.

Objective

• To hypothesize that a coupled agro-hydrological model will reveal distinct P and K responses to irrigation and soil properties, with K exhibiting greater spatial mobility due to weaker adsorption and P remaining highly localized due to strong specific adsorption in semi-arid soils.
• To quantify the vertical and lateral distribution of P and K following drip fertigation through systematic soil sampling and in situ soil water monitoring.
• To identify key drivers of nutrient transport, including soil hydraulic parameters, water application, nutrient concentration, and root distribution, via sensitivity analysis using HYDRUS-2D.
• To evaluate the performance of the coupled DSSAT–HYDRUS framework in simulating water–nutrient–crop interactions for optimizing fertigation strategies.

Study Configuration

• Spatial Scale: Field plots of 4 m² (potato) and 2 m² (fallow); soil profile analysis from 0 to 100 cm depth; computational domain of 35 cm width and 100 cm depth. Soil samples collected horizontally at 0, 5, 10, and 15 cm from emitters and vertically at 0–5, 5–10, 10–15, 15–20, 25–30, and 30–40 cm depths.
• Temporal Scale: A single potato growing season (19 June–20 October 2018). Soil samples collected at 4, 24, 98, 624, and 1632 hours post-first fertigation, and 4, 24, 98, and 960 hours post-second fertigation.

Methodology and Data

• Models used:
  • DSSAT (Decision Support System for Agrotechnology Transfer) - specifically DSSAT-SUBSTOR-Potato model.
  • HYDRUS-2D (coupled with DSSAT for dynamic LAI and potential evapotranspiration inputs).
  • RETC software (for optimizing van Genuchten-Mualem parameters).
  • Rosetta neural network software (for initial parameter prediction).
• Data sources:
  • Field experiments: Soil water content (calibrated time-domain reflectometry probes), nutrient distribution (soil sampling and laboratory analysis for available P/K, soluble P/K, and other ions), crop growth (plant height, canopy width, leaf area index, fresh/dry biomass, tuber yield), soil physical and chemical properties (texture, bulk density, pH, electrical conductivity, cation exchange capacity, organic matter), meteorological variables (on-site weather station).
  • Laboratory analysis: Soil water retention curves (sandbox and pressure plate apparatus), saturated hydraulic conductivity (constant-head permeameter).

Main Results

• Potassium (K) and phosphorus (P) exhibited limited vertical mobility (≤15 cm for K, ≤13 cm for P) due to strong soil adsorption and root uptake in the upper soil layers.
• K showed greater lateral movement (≤35 cm) compared to P, attributed to its weaker sorption affinity and higher solubility.
• Sensitivity analysis identified soil hydraulic properties (saturated water content and pore-size distribution) and hydrodynamic dispersion coefficients (longitudinal and transverse) as major drivers of water and solute transport.
• Model simulations aligned well with observed data, showing high reliability (RMSE < 0.05 cm³ cm⁻³ for water content; r² > 0.8 for solutes).
• Scenario analysis indicated that splitting the total fertilizer dose into four smaller applications (instead of two large doses) enhanced nutrient availability by 30–40%, reduced peak fixation and leaching, and maintained tuber yield (30.2–31.5 t ha⁻¹).
• Increasing irrigation water application by 1.5 times did not significantly alter vertical and lateral K and P movements.
• Overall, frequent, low-concentration fertigation improved nutrient uptake efficiency by 15–20% and minimized environmental losses.
• The simulated potato tuber yield (31530 kg ha⁻¹) closely matched the measured value (30150 kg ha⁻¹).

Contributions

• First study to integrate a coupled DSSAT-HYDRUS-2D approach to specifically model the distinct dynamics of P and K, including their adsorption chemistries and plant uptake patterns, in a drip-fertigated potato system under semi-arid conditions.
• Provides a mechanistic and validated understanding of P and K fate and efficiency, moving beyond the prevalent nitrogen-centric modeling paradigm.
• Offers practical, evidence-based insights for precision nutrient and water management, directly supporting sustainable agricultural practices and aligning with United Nations Sustainable Development Goals (SDGs).
• Delivers a robust decision-support tool for optimizing drip fertigation strategies, providing actionable recommendations for farmers and policymakers to enhance nutrient use efficiency and mitigate environmental risks.

Funding

• Technical Report No. 67055, a collaborative effort between the Soil and Water Research Institute (SWRI) of Iran, the Iranian National Elite Foundation (BMN), Ghent University (UGent), and Flemish Institute for Technological Research of Belgium (VITO NV).
• Funding provided in part by all participating institutions.
• VITO supplied the HYDRUS-2D software license.

Citation

@article{Rezaei2025Modelling,
  author = {Rezaei, Meisam and Bazargan, Kambiz and Shahbazi, Karim and Marzi, Mostafa and Cheraghi, Meysam},
  title = {Modelling phosphorus and potassium dynamics in drip-irrigated potato systems using coupled agro-hydrological model},
  journal = {Agricultural Water Management},
  year = {2025},
  doi = {10.1016/j.agwat.2025.109920},
  url = {https://doi.org/10.1016/j.agwat.2025.109920}
}