Productivity of Field‐Grown Soybeans Exposed to Acid Rain and Sulfur Dioxide Alone and in Combination

Abstract

Sulfur dioxide (SO2)‐fumigated and unfumigated field plots of soybeans (Glycine max cv. Wells) were exposed to acid (pH 3.1) or control (pH ∼ 5.3) precipitation simulants to determine effects on growth and productivity. The precipitation simulants were applied at approximately 5‐day intervals in July and August with a total of 3.4 cm applied in 1977 and 4.5 cm in 1978. Sulfur dioxide fumigations of ∼ 4‐hour durations were performed 24 times in 1977 and 17 times in 1978, resulting in an average fumigation concentration of 0.79 ppm (89.6 ppm · hour dose) SO2 the 1st year and 0.19 ppm (13.$ ppm · hour) the 2nd. The acid precipitation simulant produced no statistically significant effect on seed yield in either year and a 4% increase in seed size in 1978. The simulated acid rain may have contributed to the nutritional requirements of soybeans by providing S and N during the critical pod‐filling stage. Sulfur dioxide exposure decreased seed yields in both 1977 and 1978 by > 35 and 12%, respectively. Aceelerated senescence, as suggested by increased leaf fall, may be responsible for the decreased yield in the SO2‐exposed plants.The SO2 exposure appeared to negate the positive acid rain effect on seed size observed in 1978, when the two treatments were combined. Acid precipitation apparently increased the reduction in seed weight resulting from SO2 exposure in 1977. Although visible injury was induced by acid rain exposure in a chamber study, only a small percentage (< 1%) of tissue was affected and there was no apparent effect on plant growth. The results of these studies suggest that the possibility for harmful effects on soybean yield from acid precipitation of a magnitude used in this study are minimal; however, soybean yields may be decreased by SO2 exposures > 13.5 ppm · hour occurring during the growing season.

THE CONTRASTING RESPONSE TO SIMULATED ACID RAIN OF LEAVES AND COTYLEDONS OF CABBAGE (BRASSICA OLERACEA L.)

“…Significant reductions in yield of soybean were also found by Banwart and co-workers using a comparable experimental procedure (Banwart, Hassett & Vasalis, 1984). However, in other field experiments with this species, acid rain treatments did not cause significant reductions in yield (Irving & Miller, 1981;Troiano et al, 1983 ;Heagle et al, 1983). Differences in response to simulated acid rain have also been recorded in experiments with other crop species (Lee et al, 1981;see Irving, 1983).…”

Effects on Photosynthesis, Carbon Allocation, and Plant Growth Associated With Air Pollutant Stress

“…Depressions of photosynthetic rates may occur within minutes to hours after the initiation of exposure, are often reversible, and may not be accompanied by major visible injury, at least at low concentrations (Black and Unsworth, 1979). Recurrent exposure to low concentrations may cause the destruction of chlorophyll and hasten leaf senescence (Irving and Miller, 1981). At higher concentrations, responses often are not reversible and often are associated with the appearance of visible injury.…”

Variability of above-ground litter inputs alters soil physicochemical and biological processes: a meta-analysis of litterfall-manipulation experiments

“…Terrestrial ecosystems are undergoing simultaneous changes in climate and biogeochemical cycles, and those changes could affect plant net primary production (NPP) positively or negatively. Changes such as elevated CO 2 , nitrogen deposition (Xia and Wan, 2008) and temperature increases (Raich et al, 2006) were found to enhance plant productivity, whereas elevated O 3 (Liu et al, 2005), drought (Zhao and Running, 2010) and acid deposition (Irving and Miller, 1981) generally decreased productivity. These changes in primary production could alter both the quality and quantity of above-ground litter inputs to soil (Liu…”