Acid Tolerant Microbial Inoculants: A Requisite for Successful Crop Production in Acidic Soils

Acidic soils comprise more than 30% of the global land area and are characterized by a pH value lesser than 5.5 throughout the year. Acidic soils are characterized by the deficiency of beneficial elements such as molybdenum (Mo), phosphorus (P), magnesium (Mg) and calcium (Ca) and the abundance of aluminium (Al), iron (Fe) and manganese (Mn). Such soils are also home to unique species of microorganisms that have evolved several tolerance mechanisms in order to overcome the acidic environments. Such mechanisms range from maintaining the intracellular levels at near neutral levels to dispensing with peripheral cellular structures that are in direct contact with the soil acidity. But despite the global distribution and importance of these soils, microbial inoculants that are suited to acidic soil conditions have not received the attention of microbiologists and agronomists, thereby depriving these soils of the benefits of beneficial microbial inoculation. This chapter attempts to highlight the issues related to soil acidity with respect to their nature, nutrient availability, microbial diversity and the need for acid-tolerant microbial inoculants for use in acid soils.