Effects of Simulated Sulfuric Acid Rain on Crop Plants

Since relatively little is known about the effects of acid precipitation on growth and productivity of crop plants, a crop survey was initiated to study effects of H 2SO 4 rain simulants on growth, yield, and quality of selected crops which were chosen to represent diverse taxo nomic groups and crop products. Yield responses of 28 crop cultivars were examined. Plants were grown in pots in field-exposure chambers and subjected to three H 2 SO4 rain simulants (pH levels 4.0, 3.5, and 3.0) and to a control simulant (pH 5.6). Yield of approximately two-thirds of the crops surveyed was not affected by the H 2SO 4 rain treatments. Equal numbers of the remaining crops exhibited stimulatory and inhibitory yield responses at some H 2 SO 4 rain simulant pH levels. These results did not suggest that acid rain treatment either generally inhibited or stimulated crop productivity. Crop response depended on crop species and crop product. For example, while forage yield of alfalfa and timothy was stimulated at some acid rain pH levels, yield of the remaining forage legume and grass species was not generally affected by acid rain treatment. However, root and fruit crop species exhibited generalized responses (yield inhibition and stimulation, respectively) which appeared to be more closely associated with crop product than occurred for other crop product groupings. Effects on crop quality were also important. For instance, although yield of some horticultural leaf and fruit crops was either unaffected or stimulated by H 2 SO4 rain treatment, marketability was adversely affected at low pH because of the presence of discoloration and/or lesions produced by H 2SO4 rain treatment. This preliminary study demonstrates considerable variability in crop response to acid rain. Furthermore, little or no information is currently available concerning the effects of numerous plant, soil, environmental, and stress factors on crop response to acid rain. Consequently, general statements regarding acid rain effects on crop quality and yield are premature. Authors: C.J. Cohen, L.C. Grothaus, and S.C. Perrigan are Research Assistants, Crop Science Department Acknowledgments: We wish to express our appreciation to R.M. Cooper, M.D. Plocher, J.M. Waters, and to the rest of the staff at Schmidt Farm Research Station, Crop Science Department, Oregon State University, for their technical assistance during these studies. Preface: The research described in this report was funded under United States Environmental Protection Agency Contract No. 68-03-2702 and was planned in cooperation with US-EPA researchers, J.J. Lee and G.E. Neely. The purposes of this report are to document the work performed under this contract and to make the information obtained available to interested parties.