ABSTRACT
Microorganisms are an interactive component of soil systems in that they contribute to soil acidification and in turn respond to changes in soil pH. The regulation of soil biological processes by pH, as well as the effects of microorganisms on soil acidification, can be studied at different scales, ranging from microsite effects in the vicinity of plant roots to long-term effects on soil genesis and ecosystem properties. At the most fundamental level, microbial acid production leads to the weathering of rocks and minerals into secondary minerals that constitute soil [1]. Changes in soil acidity affect the leaching and bioavailability of base cations, the bioavailability of phosphorus, and the solubility and toxicity of metal cations. At the ecosystem level, biologically driven changes in soil pH influence the selection of plant and microbial species that make up the community. Soil pH also affects the primary productivity by controlling nutrient turnover rates, nitrogen chemistry, accumulation of phytotoxic compounds, and the populations of symbiotic, plant growth-promoting, and root disease-causing microorganisms that colonize the rhizosphere. In this manner, soil pH is one of the most fundamental variables in plant microbial ecology and is routinely measured and reported in virtually all studies on soil biology.
