Rhizosphere microbe-mediated alleviation of aluminum and iron toxicity in acidic soils

Acid soils have pH values of less than 5.5 consistently for extended periods. Agricultural practices, such as flooding and agrochemical application, can cause soil acidity. Cultivation in these soils is extremely challenging as these are associated with metallic toxicities, viz., aluminum (Al) and iron (Fe2 +), accounting for considerable crop yield reduction. Higher soil Al levels limit plant root growth and excess Fe2 + causes nutrient disorders. Several conventional methods, such as proper water management system, application of lime, etc., are being performed to reduce the acidic condition. However, these methods are temporarily satisfying and can affect soil fertility. Employing microorganisms to alleviate such metal toxicity is gaining popularity as an ecofriendly alternative. This chapter deals with the major mechanisms by which agriculturally important microorganisms impart Al and Fe stress tolerance to plants along with the cultivation challenges in acidic soils and the impact of Al and Fe toxicity on crop plants.