Phogat et al. (2025) Regional dynamics in evapotranspiration components, crop coefficients, and water productivity of vineyards

Identification

• Journal: Agricultural Water Management
• Year: 2025
• Date: 2025-11-12
• Authors: V. Phogat, Paul R. Petrie, Marcos Bonada, Cassandra Collins
• DOI: 10.1016/j.agwat.2025.109955

Research Groups

• Crop Sciences, South Australian Research and Development Institute, Adelaide, SA, Australia
• School of Agriculture, Food and Wine, Waite Research Institute, University of Adelaide, Adelaide, SA, Australia
• College of Science and Engineering, Flinders University, Adelaide, SA, Australia
• ARC Training Centre for Innovative Wine Production, University of Adelaide, Adelaide, SA, Australia

Short Summary

This study estimated water balance components, crop coefficients, and water productivity for Shiraz vineyards across 48 locations in Barossa, South Australia, over three seasons using the FAO-56 dual crop coefficient approach, revealing significant spatial and temporal variability in these parameters and highlighting the need for site-specific irrigation management.

Objective

• To estimate actual evapotranspiration (ETc act), transpiration (Tc act), soil evaporation (Es), seasonal water stress (Ks), and location-specific actual crop coefficients (Kc act and Kcb act) for Shiraz grapevines over multiple seasons (2018–19, 2019–20, 2020–21) at 48 locations in the Barossa region.
• To compare the water balance components, crop coefficients, and imposed water stress across different sites, sub-regions, and the entire region.
• To estimate the water productivity in terms of yield and fresh and dry biomass of pruning to understand the inherent variability induced by soil type, vine canopy, and climate parameters.

Study Configuration

• Spatial Scale: 48 locations (24 sites with two distinct zones each) in the Barossa GI zone (including Barossa Valley and Eden Valley subregions) in South Australia.
• Temporal Scale: 3 consecutive growing seasons (2018–19, 2019–20, 2020–21), from 15 September to 31 March each season.

Methodology and Data

• Models used: FAO-56 dual crop coefficient (DCC) approach.
• Data sources:
  • Soil moisture probes (EnviroSCAN, Sentek technologies) for real-time soil water content dynamics at 48 locations.
  • Portable automatic weather stations (MEA Junior WS, Measurement Engineering Australia) at each site for daily temperature, relative humidity, rainfall, wind speed, and solar radiation.
  • Soil sampling and analysis (MIR spectroscopy, clod method) for physico-chemical characteristics and plant available water capacity (PAWC).
  • Winegrape phenology observations (Eichhorn and Lorenz system) and canopy measurements (Leaf Area Index, LAI, estimated from iPhone images analyzed with Matlab code).
  • Measured vine pruning weight and fruit yield at all study sites.
  • Reference crop evapotranspiration (ETo) estimated using the modified Penman-Monteith approach.

Main Results

• Significant variability was observed in water balance parameters, crop and water stress coefficients, and water productivity across sites and seasons, with a coefficient of variation ranging from 20% to 97% in daily and seasonal actual evapotranspiration.
• Average actual transpiration accounted for approximately 63% and evaporation for 37% of seasonal actual evapotranspiration, indicating potential for water savings from soil surface evaporation.
• Estimated actual single crop coefficient (Kc act) varied widely across growth stages: 0.32–0.76 (initial), 0.35–0.59 (budburst to flowering), 0.16–0.62 (flowering to veraison), and 0.16–0.64 (veraison to harvest).
• Actual basal crop coefficients (Kcb act) showed considerable site-specific variability, questioning the use of uniform coefficients.
• Water stress (Ks) gradually increased, peaking from late November to early December, with regional variations from 20% to 64%.
• Water productivity based on transpiration (WPTc) was approximately 60% higher than that based on actual evapotranspiration (WPETc) across all sites and subregions.
• The model performance for daily plant available water (PAW) showed good agreement with measured values, with average root mean square error (RMSE) of 10.1 mm and normalized Nash-Sutcliffe efficiency (nNSE) of 0.76.

Contributions

• Provides location-specific actual crop coefficients (Kc act, Kcb act) and water stress coefficients (Ks) for Shiraz grapevines across a diverse wine-producing region, addressing the limitations of generic coefficients.
• Quantifies the spatial and temporal variability of evapotranspiration components and water productivity at a regional scale, offering insights for efficient irrigation scheduling and water resource management.
• Demonstrates the successful application of the FAO-56 dual crop coefficient approach for assessing site-specific water needs and stress levels in highly managed perennial crops like grapevines.
• Highlights the significant contribution of soil evaporation to total water loss (37%), particularly during early growth stages, suggesting opportunities for water saving strategies like mulching.

Funding

• Wine Australia (Project Number: UA1602)
• Levies from Australia’s grape growers and winemakers
• Matching funds from the Australian Government

Citation

@article{Phogat2025Regional,
  author = {Phogat, V. and Petrie, Paul R. and Bonada, Marcos and Collins, Cassandra},
  title = {Regional dynamics in evapotranspiration components, crop coefficients, and water productivity of vineyards},
  journal = {Agricultural Water Management},
  year = {2025},
  doi = {10.1016/j.agwat.2025.109955},
  url = {https://doi.org/10.1016/j.agwat.2025.109955}
}