Precipitation over the eastern United States has
been increasing in acidity, particularly within the last
three decades. The average annual pH of rain in this
area is about 4.2. The foliar surface, or phylloplane,
of soybean can be damaged by rain acidified to pH 2.9.
Simulated acidic precipitation has an overall inhibitory
influence on soil microbial processes. The effect acidic
precipitation may have on epiphytic microorganisms has
not been examined. Bacteria are among the most numerous
residents on the phylloplane.