Project at a Glance

Title: Interaction of low levels of ozone and relative humidity on leafy vegetables.

Principal Investigator / Author(s): Bennett, J. P.

Contractor: UC Davis

Contract Number: A6-194-30

Research Program Area: Atmospheric Processes, Ecosystem & Multimedia Effects

Topic Areas: Agriculture, Ecosystem Impacts


The effects of O3 on the yield of crops are dependent on the conditions of the environment where the crop is grown. Varying levels of humidity are known to affect the development of visible injury produced by O3 but nothing is known about how O3 and humidity affect yield. The purpose of this study was to determine the effects of varying levels of O3 and humidity on the yields of leaf lettuce and spinach.

The crops were grown in controlled environment chambers and fumigated six hours daily with 0, .08 and..18 ppm O3 at 30, 50 and 80% relative humidity (RH) for 32-35 days. Results indicated that spinach yield losses followed the opposite pattern. This means that generalizations about yield losses in more humid vs. dry environments are not possible because responses are crop specific. Lettuce plants were also significantly smaller and more tender, rendering them unmarketable regardless of the weight loss. This occured at a concentration below the California one hour O3 standard of .10 ppm and suggests that the standard does not adequately protect this crop. Yield losses in both crops were not correlated with visible injury symptoms and even occured without injury in the case of lettuce. This report was submitted in fulfillment of Agreement No. A6-194-30 by J. P. Bennett under the sponsorhip of the California Air Resources Board. Work was completed as of 15 October 1978.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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