Abstract |
Cotton (Gossypium hirsutum L. cv. 'SJ-2'), grown in open-top chambers in the Central Valley of California, was exposed to 6 ozone (O3) treatments ranging from charcoal-filtered (CF) to ambient plus 0.10 ppm O3 (1981) or twice ambient O3 concentrations (1982) for the entire growing seasons of 1981 and 1982. Half the plots were irrigated optimally and the other half were water-stressed by providing 25% (1981) or 20% (1982) less irrigation water. During the typically hot, dry growing season of 1981, cotton yield in normally irrigated (NI) treatments was reduced 20% in non-filtered (NF) chambers relative to CF controls. Doubling ambient O3 concentration reduced yield 45%. Water-stressed (WS) plants showed almost no response to O3. In 1982, potential evapotranspiration during the growing season averaged 20% less and ambient O3 concentration averaged 39% lower than in 1981. Under these growing conditions, cotton yields in NI and WS treatments responded similarly to O3. Yields in NF chambers were reduced 15% relative to CF chambers. Doubling ambient O3 concentrations reduced yields 65%. The greater relative response of cotton to O3 in 1982 may have resulted from the cooler more humid growing conditions, which increased the susceptibility of cotton to O3. (Copyright (c) J. Environ, Qual., Vol. 14, No. 1, 1985.) |