EFFECTS OF SIMULATED ACIDIC RAIN ON YIELDS OF FIELD‐GROWN CROPS

Abstract

Experiments were performed to determine the effects of simulated acidic rainfall on yields of radish (Raphanus sativa L.), garden beet (Beta vulgaris L.), kidney bean (Phaseolus vulgaris L.), and alfalfa (Medicago sativa L.) grown under standard agronomic practices. The experimental design allowed the detection of statistically significant differences among means that differed from each other by less than 10 %. The plants were exposed to small additions of simulated rain at pH levels of 5.7, 4.0, 3.1 and 2.7. The spray‐to‐wet simulated rain applications were similar in volume to the median of all ambient rainfall showers. Some plants received no simulated rainfall and all were exposed to ambient rainfall at Brookhaven National Laboratory (Upton, N.Y), which had a mean weighted pH of 4.06 during the summer of 1980. Root mass of radish was not significantly affected by simulated acidic rainfall. The absence of a decrease in root yields in radish was coincident with an absence of visible foliar injury. Beet plants treated with simulated rain applications of pH 4.0, 3.1 and 2.7 showed significant decreases in yield compared with yields under both the ambient rainfall only and pH 5.7 simulated rain treatments. Root yields of beet exposed to simulated rain at pH 5.7, 4.0. 3.1 and 2.7 were 110, 79, 84 and 86% of those receiving ambient rainfall only. Foliar injury on beet was attributed to exposure both to simulated acidic rain of pH 4.0, 3.1 and 2.7 and to several consecutive ambient rainfalls which had an average pH of 3.9. This is the first experiment showing visible foliar injury due to either ambient rainfalls or simulated rain above pH 3.1 under agronomic conditions. With kidney bean, there were no significant differences among treatments of such parameters as number of seeds per plant, mass of seeds per plant and number of pods per plant. There were also no significant differences among treatments for fresh mass or dry mass of alfalfa hay. These studies suggest that no generalizations about crop sensitivity with regard to either plant portion harvested (e.g. roots, fruits, leaves) or taxonomic considerations can be made at the present time. Copyright © 1982, Wiley Blackwell. All rights reserved