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United States Department of Agriculture

Agricultural Research Service

You are here: ARS Home / Research / National Programs / National Program 203 : Air Quality / Component IV: Ozone Impacts
National Program 203: Air Quality
Component IV: Ozone Impacts
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1 - Introduction
2 - Effects of Ozone on Yield and Product Quality
3 - Mechanisms of Ozone Response
4 - Ozone-Tolerant Crops
5 - Effects of Ozone on Pests and Parasites
Effects of Ozone on Yield and Product Quality

Problem Statement

Rationale.  Because of the wide-ranging movement of ozone precursors from urbanized areas and their subsequent combination to form ozone, the problem of ozone impacts on crops is not limited to urbanized areas or to any particular part of the country. Some of the most productive agricultural areas in the eastern and midwestern parts of the U.S. are exposed to elevated ozone, in addition to the well known ozone problems in California and elsewhere. Tropospheric ozone concentrations have increased appreciably over the past 50 years. Concentrations in many areas of the U.S. are now approximately twice as high as would exist without the influence of human activities, and ozone concentrations in rural areas are projected to increase. The adverse effect of ozone on agriculture has national and international ramifications because it directly increases production costs of food and fiber, which are passed on to the consumer. In addition, tropospheric ozone adversely affects food quality and nutrition, environmental quality, biodiversity, and the atmosphere as a natural resource.

What is known.  Visible symptoms of ozone injury to plants vary in severity among species, but may consist of decreased chlorophyll, increased pigmentation, and areas of dead plant tissue. Unfortunately, these symptoms often are not distinguishable from symptoms caused by pathogens, nutrient deficiencies, or other stresses. Often, the only visible feature of ozone stress is more rapid senescence (tissue death) toward the end of the life cycle, especially with annual plants, which is noticeable only when directly compared to nonstressed plants. Field experiments with open-top chambers have shown that ambient ozone concentrations suppress the growth and yield of major crops in productive agricultural areas of the country. Agronomic crops such as soybean, cotton, peanut, and some wheat cultivars are generally sensitive to ozone. Corn and sorghum are less sensitive although there is variability in ozone sensitivity among cultivars of the same crop. Estimates of ozone-induced yield losses nationally are variable, but limited data indicate that ozone causes substantial economic losses through reduction of crop yields. The extent of loss varies not only with the ozone sensitivity of individual crops, but also highly depends on environmental conditions during plant growth and exposure. For example, plants tend to be more sensitive to injury when grown and exposed under conditions of high humidity; whereas they are less sensitive under drought and elevated atmospheric carbon dioxide. In general, detrimental effects of ozone are on crop yield although minor changes in product quality have been reported. Visible injury and suppressed growth also diminish the economic value of some horticultural and ornamental crops.

Gaps.  Although limited data are available from field studies concerning ozone effects on yield and/or quality of major crops (e.g., soybean, corn, cotton, peanut, rice, wheat, sorghum), not all economically important crops have been tested. For those crops that have been studied, too few cultivars or varieties were evaluated to estimate risks to production with confidence. Furthermore, there are insufficient data on those cultivars currently used in production agriculture, and too little is known about their genetic variability in ozone sensitivity. There is a serious shortage of data on horticultural crops (food and ornamentals), which often are ozone sensitive and are very important economically. In addition, experiments to date have not been conducted under a sufficient range of climates to understand the effects of variable environmental factors on the quantification of ozone impacts. Effects of environmental variables such as temperature, relative humidity, rainfall, solar radiation, and soil properties are particularly important with the rise in atmospheric carbon dioxide concentrations and the associated changes in global climate that may occur. Ozone exposure patterns vary to some extent both geographically and year-to-year. The degree to which these variations affect plant response are not well understood. The capability to extrapolate data across years and climates is currently limited, and data are needed to develop plant growth process models and statistical models for extrapolation and prediction. Techniques and tools for experimentation and assessment need further development.


  • Determine impacts of ozone on yield and quality of major crops, including variation among cultivars within species;
  • Determine environmental influences on crop response to ozone; and
  • Improve ability to predict ozone effects on crop production under future climate/management scenarios


This research should emphasize experiments in field plots with plants grown from germination through maturity while exposed to appropriate ozone concentrations and exposure regimes. Experiments in greenhouses and growth chambers should be conducted with supplemental light that approximates the quality and intensity of full sunlight. Typically, open-top field chambers or similar facilities will be used to control and manipulate ozone concentrations around test plants. This approach permits the experimental pollutant-exposure treatments to be defined, allowing dose-response analysis within and across years. Use of existing ambient ozone gradients, open-air treatments (similar to those used in free-air carbon dioxide enrichment studies) or chemical ozone protectants should be considered when there are distinct experimental advantages.

Plant response to ozone varies across locations and years, and therefore gas exposure concentrations should encompass a wide range. Ozone exposure regimes should be similar to those found in ambient air (i.e., simulate daily peaks and episodic nature of ambient ozone concentrations). Plant cultivars, soil variables, or other factors can be included as additional variables, as appropriate. Environmental data such as temperature, rainfall, humidity, and irradiation should be routinely recorded throughout the experiments. Prominent cultivars of economically important agronomic and horticultural species should be used unless the specific research needs dictate otherwise. Emphasis for each crop species should be on cultivars or genotypes that represent current and, as much as known, future farming practices.

Statistical dose-response models will be developed to estimate effects of ranges of ozone concentrations on yield. The experimental data, however, will represent only a small fraction of the air pollutant/climate scenarios that may be encountered. Therefore when possible, associated physiological and growth data should be used to develop mechanistic simulation models of crop growth and yield that incorporate response to ozone stress.


  • Data will be available to determine the economic costs of ozone pollution to crop production.
  • The future effects of ozone on crop production in a changing climate will be predictable.
  • A scientific basis will be provided to choose among management options to limit ozone impacts on crop production.


Informed decisions by agricultural producers and regulatory and policymakers to minimize ozone impacts on agricultural production, agribusiness, and the public.

Linkages to Other ARS National Programs

  • Global Change
  • Integrated Agricultural Systems
  • Plant Diseases
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Last Modified: 10/28/2008
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