Geostatistics as a validation tool for setting ozone standards for durum wheat

Area of Science:

• Environmental Science
• Plant Science
• Agricultural Science

Background:

• Ozone pollution poses a significant threat to plant health and agricultural productivity.
• Existing European and USA ozone standards lack field validation due to independent monitoring networks.
• Durum wheat in Italy was used as a model to test ozone protection standards.

Purpose of the Study:

• To validate and compare the effectiveness of European and USA ozone standards in protecting crops.
• To identify optimal ozone exposure metrics and critical levels for safeguarding agricultural yields.
• To assess the spatial representativeness of current ozone standards.

Main Methods:

• Geostatistical analysis was employed to integrate spatially independent ozone, meteorological, and plant response data.
• Biological responses of durum wheat were monitored in the field.
• Multiple regression analysis was used to determine factors influencing yield variability.

Main Results:

• Ozone impact on yield was better summarized by exposure-based standards than by hourly averages.
• European standards protected >=90% of sites, while the USA legal level (75 ppb) protected only 39%.
• Reducing the USA level to 65 ppb or using the W126 index improved protection to 91% and 97%, respectively. A flux of 22 mmol m(-2) protected 97% of sites.

Conclusions:

• European exposure-based ozone standards offer superior crop protection compared to current USA standards.
• Adjustments to USA ozone levels, such as adopting the Canadian 65 ppb or W126 index, are recommended for better agricultural protection.
• Precipitation is a major driver of yield variability, while ozone's direct impact is relatively small under current standards.