Zinc-Solubilizing Microorganisms: Contributions in Nutrient Availability and Implications for Crop Productivity in Sustainable Agriculture

Conventional intensive agricultural practices are currently used to make nutrition available for the ever-increasing global inhabitants. Among various micronutrients, zinc (Zn) performs several essential functions in plants' life cycle. Therefore, approaches to enhance Zn content in cereal grains are required to reduce the negative effects of Zn deficiency on plants and humans. Currently, several soil- or rhizosphere-dwelling microorganisms have been characterized that employ different mechanisms to enhance Zn availability to plants. Some of the zinc-solubilizing microorganisms (ZnSMs) also possess additional beneficial properties, including solubilization of phosphorous and potassium, and production of phytohormones as well as siderophores. Application of such ZnSMs as bioinoculants to plants has been found to enhance soil fertility status, leading to increases in plant biomass and crop production. Therefore, ZnSMs are applied as microbial inoculants to minimize conventional fertilizer use in soils. In this chapter, current information on the characterization of ZnSMs, mechanisms employed in Zn solubilization, and their contribution toward improvement in crop yields are discussed.