El-Wahed et al. (2026) Partial Root-Zone Drying and Regulated Deficit Irrigation Effects on Potato Yield, Quality, Water Productivity, and Net Profit under Surface vs. Subsurface Drip Irrigation

Identification

• Journal: Potato Research
• Year: 2026
• Date: 2026-04-09
• Authors: Mohamed H. Abd El-Wahed, Mahmoud M. Ali, Ahmed Abdel-Aziz, Yahia A. M. Ibrahim
• DOI: 10.1007/s11540-026-10054-7

Research Groups

• Department of Agriculture, Faculty of Environmental Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
• Department of Agricultural Engineering, Faculty of Agriculture, Fayoum University, Fayoum, Egypt
• Department of Agricultural Engineering, Faculty of Agriculture, Ain Shams University, Cairo, Egypt

Short Summary

This study evaluated the combined effects of full and deficit irrigation levels (100%, 80%, 60% ETc), irrigation techniques (single lateral, partial root-zone drying), and drip irrigation depths (surface, 15 cm, 30 cm) on potato yield, quality, water productivity, and net profit in sandy loam soil under arid conditions in Egypt. It found that full irrigation with partial root-zone drying and subsurface drip irrigation at 15 cm depth maximized yield and net profit, while 80% ETc with the same technique saved 20% water with only a slight yield reduction, making it suitable for water-limited conditions.

Objective

• To evaluate the combined effects of partial root-zone drying (PRD) and regulated deficit irrigation (RDI) under surface and subsurface drip irrigation (DI and SDI) systems on potato yield, quality, water productivity, and net profit in arid regions, specifically Egypt.

Study Configuration

• Spatial Scale: Field experiments conducted at the Experimental Demo Farm, Faculty of Agriculture, Fayoum University, Fayoum, Egypt (Latitude: 29° 17′ 34.1" N, Longitude: 30° 54′ 57.3" E, Altitude: + 25 m). The soil was classified as sandy loam with slight salinity (EC values ranging from 4.66 to 6.45 dS/m).
• Temporal Scale: Two consecutive spring growing seasons (2021 and 2022). Potato plants (Spunta variety) were grown for 120 days each season.

Methodology and Data

• Models used:
  • Reference evapotranspiration (ETo) calculated using Doorenbos and Pruitt (1992) Eq. (1): ETo = Epan × Kpan.
  • Crop evapotranspiration (ETc) estimated using Doorenbos and Pruitt (1992) Eq. (2): ETc = ETo × Kc.
  • Irrigation water applied (IWA) calculated using Keller and Karmeli (1975) Eq. (3).
  • Water productivity (WP) calculated using Fessehazion et al. (2011) Eq. (5).
  • Net profit calculated as Economic income - Total costs (Eq. 6), with total costs determined according to Mansour et al. (2020).
• Data sources:
  • Field experiments with a split-split-plot design and three replicates.
  • Treatments included three irrigation regimes (FI: 100% ETc, I80: 80% ETc, I60: 60% ETc), two irrigation techniques (Single Lateral (SL), Partial Root-Zone Drying (PRD)), and three buried lateral depths (0 cm (surface), 15 cm, 30 cm).
  • Monthly weather data (temperature, relative humidity, wind speed, evaporation pan).
  • Soil physical and chemical properties (0–20, 20–40, 40–60 cm depths).
  • Irrigation water quality analysis.
  • Measurements of potato tuber yield, tuber size distribution, real density, and firmness.
  • Economic data on potato crop production prices and cultivation costs.
  • Statistical analysis performed using ANOVA (InfoStat 2016) with LSD test at P < 0.05.

Main Results

• Full irrigation (FI, 100% ETc) under PRD and subsurface drip irrigation (SDI) at a buried lateral depth of 15 cm resulted in the highest potato tuber yield (50,560 kg/ha) and net profit (282,725 L.E./ha).
• The most marketable tuber size category was 30–60 mm, which also showed the highest yield (31,940 kg/ha) under FI, PRD, and SDI at 15 cm depth.
• When irrigation water applied (IWA) decreased by 20% (I80) and 40% (I60), potato yield decreased by 11.04% and 29.88%, respectively.
• The maximum water productivity (WP) value was 15.62 kg/m³, recorded with irrigation treatment I60 (60% ETc), using PRD under SDI at a buried depth of 15 cm.
• PRD irrigation significantly increased the mean values of potato crop production by 20.33% (FI), 30.84% (I80), and 32.67% (I60) compared to single lateral (SL) treatments.
• A buried lateral depth of 15 cm consistently outperformed surface drip irrigation (0 cm) and SDI at 30 cm depth across all irrigation treatments for tuber yield, size distribution, real density, and net profit.
• The highest real density of potato tubers was 1087 kg/m³ under FI, PRD, and SDI at 15 cm depth.
• Deficit irrigation (I60) resulted in higher potato tuber firmness (maximum 322,600 Pa) compared to full irrigation (FI, minimum 296,200 Pa).
• A quadratic relationship was observed between the irrigation water applied (IWA) and potato crop productivity.

Contributions

• Provides a comprehensive evaluation of the synergistic effects of combining regulated deficit irrigation, partial root-zone drying, and varying drip irrigation depths (surface vs. subsurface) on potato production in arid environments.
• Offers specific, localized recommendations for optimal irrigation management in Egypt, addressing a gap in the literature where most studies were conducted under different climatic and soil conditions.
• Quantifies the trade-offs between water saving and yield/profit, recommending full irrigation with PRD and SDI at 15 cm for abundant water, and 80% ETc with the same technique for water-limited conditions to save 20% IWA with minimal yield reduction.
• Highlights the importance of subsurface drip irrigation at an optimal depth (15 cm) for enhancing water productivity, tuber quality (real density), and economic returns.

Funding

• Deanship of Scientific Research (DSR) at King Abdulaziz University, Jeddah, Saudi Arabia (Grant no. IPP 36-155-2025).

Citation

@article{ElWahed2026Partial,
  author = {El-Wahed, Mohamed H. Abd and Ali, Mahmoud M. and Abdel-Aziz, Ahmed and Ibrahim, Yahia A. M.},
  title = {Partial Root-Zone Drying and Regulated Deficit Irrigation Effects on Potato Yield, Quality, Water Productivity, and Net Profit under Surface vs. Subsurface Drip Irrigation},
  journal = {Potato Research},
  year = {2026},
  doi = {10.1007/s11540-026-10054-7},
  url = {https://doi.org/10.1007/s11540-026-10054-7}
}