Simulated acid rain effects on yield response of two corn cultivars

Acid rain is a documented phenomenon over much of the eastern and midwestern United States, including major portions of the Corn Belt. However, few studies report the effect of acid rain on yield of corn (Zea mays L.). Field experiments were conducted in 1983 and 1984 on a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) soil at Urbana, IL. Two corn cultivars (Pioneer 3377 and B73 x Mo17) were protected from ambient rain by two automated movable rain exclusion shelters and were exposed to one of six simulated rain acidities ranging from pH 5.6 to 3.0. Analysis of the effect of rainfall pH on grain yield showed no significant linear or quadratic trend (α = 0.10) for either cultivar in individual years or with both years combined. Comparisons among treatments for both cultivars showed rain simulants with no added acid (pH 5.6) resulted in grain yields that were not significantly different from the average grain yields of the other five pH treatments. For B73 x Mo17, the 2-yr combined yield for the pH 3.0 treatment was significantly lower (5.7%) than the average yield for the other five treatments. This same contrast was not significant for Pioneer 3377. These results imply that under normal environmental conditions and agronomic practices, rainfall at its present levels of acidity has little if any effect on corn yields.