I am more fascinated than ever on the nitrogen issue whose role in ozone has been an ongoing concern of mine - mainly because of all the nitrogen-loving lichens growing berserk on trees, dead wood, and rocks...so today I called Thomas Armitage, a self-described Environmental Scientist who is the unfortunate go-to guy at the EPA for the Science Advisory Board, listed as their contact. He did return my call, in the early evening - working overtime!
Seasonal mean of ambient ozone concentrations between 09:00 and 16:00 h over the continental United States from 1 July to 31 September 2005 (Tong et al. 2007. Atmos. Environ. 41:8772). Areas shown in brown, orange and red can experience significant crop yield loss and damage to ecosystem function from ambient ozone.
Yield Loss Caused by Ozone
Field research to measure effects of seasonal exposure to ozone on crop yield has been in progress for more than 40 years. Most of this research utilized open-top field chambers in which growth conditions are similar to outside conditions. The most extensive research on crop loss was performed from 1980 to 1987 at five locations in the USA as part of the National Crop Loss Assessment Network (NCLAN). At each location, numerous chambers were used to expose plants to ozone treatments spanning the range of concentrations that occur in different areas of the world. The NCLAN focused on the most important agronomic crops nationally.
The strongest evidence for significant effects of ozone on crop yield comes from NCLAN studies (Heagle 1989). The results show that dicot species (soybean, cotton and peanut) are more sensitive to yield loss caused by ozone than monocot species (sorghum, field corn and winter wheat).