Field Methods to Assess the Impact of Air Pollutants on Crop Yields

摘要

The wide range of estimates for annual losses in crops ($135 to 900 million) from pollutants indicates a lack of objective information on the subject. Estimates have been based primarily on the presence of foliar symptoms but little is known of the relationships between foliar symptoms, plant growth stage, and yield loss. For the most part, the previous estimates disregard subtle injury or yield loss in the absence of symptoms. Sound experimental evidence on the yield responses of plants to ambient levels of pollutants is needed before rational decisions on air pollution control strategies can be made. Recent efforts to experimentally quantify the effects of pollutants on plants in the field have centered on the use of protective chemicals, open-air exposures, ambient pollutant gradients, sensitive and resistant cultivars, or field exposure chambers. Each of these methods has advantages and disadvantages which are discussed. We feel that open-top field chambers are presently the best approach to a critical evaluation of the effects of gaseous pollutants on plant yield. The effects of the chambers on the environment are small, yet pollutant concentrations can be adequately controlled through exclusion and addition. Current methodologies used in open-top field chambers and results showing threshold concentrations of ozone for growth and yield effects of several crop species are presented. Estimates of losses for agricultural crops at different seasonal ozone levels are given. 44 references, 4 figures, 4 tables. (ERA citation 09:026931)