Effects of Ozone, Sulfur Dioxide, Soil Water Deficit, and Cultivar on Yields of Soybean

Abstract

Abstract The effects of ozone (O 3 ) stress on bean yields and seed size of four soybean cultivars [ Glycine max (L.) Merr.] grown in open‐top chambers in 1981, 1982, and 1983 are presented. The O 3 treatments included charcoal filtered (CF) and nonfiltered (NF) air, and 0.03, 0.06, and 0.09 µ L L −1 O 3 added 7 h d −1 to NF air. The effects of SO 2 in concentrations from 0.005 to 0.224 µ L L −1 (4 h d −1 , 5 d wk −1 ) from the seedling stage to maturity were studied in 1981 and 1982. In 1982 and 1983 the effects of soil moisture stress (SMS) and well‐watered (WW) soil conditions on the response of soybean to O 3 stress were determined. The primary objective was the evaluation of 3 yr of soybean data from our site using the nonlinear Weibull and the polynomial dose‐response models to relate yield responses to O 3 exposure doses. The variables also included SO 2 , soil moisture, and cultivar. The homogeneity of the response equations were compared to permit development of the smallest set of homogeneous equations over years. Both O 3 and SO 2 negatively impacted bean yields and seed size. No interactions between O 3 and SO 2 were indicated. With the Weibull model, interactions between O 3 and soil moisture were observed with ‘Forrest’ in 1982 and ‘Williams’ in 1983. With an O 3 level considered typical in soybean production areas (seasonal 7 h d −1 , 0.055 µ L L −1 ) compared to background O 3 (0.025 µ L L −1 ) and using all data from 3 yr of experiments, the Weibull model predicted the same (15%) mean yield loss under both SMS and WW regimes.