ABSTRACT
Under areas where rainfall exceeds evapotranspiration, soil acidification is an ongoing process that can be either accelerated by the activity of plants, animals, and humans or slowed down by careful management practices [1,2]. In areas that remain unaffected by industrial pollution, soil acidification is mainly caused by the release of protons (H) during the transformation and cycling of carbon (C), nitrogen (N), and sulfur (S) in the soil-plant-animal system [3,4]. Under managed systems much of the accelerated soil acidification is caused by increasing N and S inputs into the farming system (Table 1). For example, in areas of Australia where legumes have been grown continuously for more than 30 years, the soil pH has decreased by about one unit [5-10]. Similarly, in New Zealand, intensively managed legume-based dairy pastures require applications of approximately 2.5 tons of lime per ha every 6 years [11,12] to neutralize acidity mostly generated through loss of N from an accelerated N cycle.
