Erdem et al. (2026) Evapotranspiration and crop coefficient of drip irrigated walnut trees in semi-arid climatic conditions, Türkiye

Identification

• Journal: Soil and Water Research
• Year: 2026
• Date: 2026-03-27
• Authors: Tolga Erdem, Erhan Göçmen, Mehmet Şener, Zafer Coşkun, Ahmet Semih Yaşasın, Buse Önler
• DOI: 10.17221/72/2025-swr

Research Groups

• Department of Biosystems Engineering, Faculty of Agriculture, Tekirdağ Namık Kemal University, Tekirdağ, Türkiye
• Tekirdağ Viticulture Research Institute, Tekirdağ, Türkiye

Short Summary

This study determined the seasonal evapotranspiration (ETc) and crop coefficients (Kc) for drip-irrigated walnut trees (ages one to nine) in Türkiye's semi-arid climate. The research provides specific monthly Kc values, ranging from 0.55 in April to 1.07 in July, which are essential for optimizing irrigation water management.

Objective

• To determine the seasonal evapotranspiration (ETc) and crop coefficient (Kc) for walnut trees (ages one to nine) grown under drip irrigation in semi-arid climatic conditions in Türkiye.

Study Configuration

• Spatial Scale: Walnut orchards in a semi-arid climate in Tekirdağ, Türkiye.
• Temporal Scale: Eight growing seasons (2015, 2016, 2017, 2018, 2019, 2021, 2022, and 2023).

Methodology and Data

• Models used: Calculation of reference evapotranspiration (ET0) and crop coefficients (Kc) based on Class A pan evaporation and applied irrigation water. The methodology implicitly follows principles outlined in FAO Irrigation and Drainage Paper No. 56.
• Data sources: Measured Class A pan evaporation, applied irrigation water amounts, and measured rainfall.

Main Results

• The total amount of irrigation water applied varied between 371.7 mm and 619.6 mm (average over eight years).
• Total evapotranspiration (ETc) for the treatment representing 100% Class A pan evaporation (I2) fluctuated between 585.9 mm and 676.5 mm over the study years.
• Daily reference evapotranspiration (ET0) values ranged from 1.85 mm/day to 7.07 mm/day.
• Average monthly crop coefficients (Kc) for walnut trees were calculated as:
  • April: 0.55
  • May: 0.71
  • June: 1.02
  • July: 1.07
  • August: 1.01
  • September: 0.74

Contributions

• Provides empirically derived seasonal evapotranspiration and specific monthly crop coefficient values for drip-irrigated walnut trees (ages one to nine) in a semi-arid region.
• Offers practical data crucial for precise irrigation scheduling and improving water management strategies for walnut cultivation in similar climatic zones.
• Contributes to the existing literature by filling a gap for this specific crop and irrigation method under semi-arid conditions over a multi-year period.

Funding

• Not specified in the provided text.

Citation

@article{Erdem2026Evapotranspiration,
  author = {Erdem, Tolga and Göçmen, Erhan and Şener, Mehmet and Coşkun, Zafer and Yaşasın, Ahmet Semih and Önler, Buse},
  title = {Evapotranspiration and crop coefficient of drip irrigated walnut trees in semi-arid climatic conditions, Türkiye},
  journal = {Soil and Water Research},
  year = {2026},
  doi = {10.17221/72/2025-swr},
  url = {https://doi.org/10.17221/72/2025-swr}
}