Effects of acidity of simulated rain and its joint action with ambient ozone on measures of biomass and yield in soybean

Abstract

An experiment was performed to determine whether the presence of ozone modified the effects of acidity of simulated rain on growth and yield of soybean ( Glycine max. [L.] Merr.). Beeson, a type II cultivar, was grown in field chambers and exposed to simulated rain at 3 levels of acidity, pH 4.0, 3.4 and 2.8. Each level of acidity was applied to plants grown either in unfiltered ambient air or in charcoal filtered (to remove ozone) ambient air. An interaction between acidity of simulated rain and filtration of ambient air on growth and yield was present. The difference in total dry mass between plants grown in filtered and unfiltered chambers increased with increased acidity, of simulated rain treatments. In filtered air, vegetative mass was only slightly decreased with increased acidity, whereas reproductive mass was increased with increased acidity. In unfiltered air vegetative mass decreased with increased acidity but reproductive mass was only slightly decreased at pH 2.8. Components of yield also were differentially affected by acidity, which indicates the need for a better understanding of the sensitivities of different development processes of the plant to each kind of pollutant. The apparent interaction between ozone and acidic rain indicates that further investigations on this combination must be conducted before acidic rain effects on plant growth can be accurately assessed in ambient atmospheres.