Bacterial Inoculants: How Can These Microbes Sustain Soil Health and Crop Productivity?

An increasing trend for the use of microbial bioinoculants to accomplish sustainable agriculture has been witnessed across the globe. Bacterial inoculants, mostly composed of beneficial bacteria including the plant growth-promoting rhizobacteria (PGPRs), exhibit tremendous metabolic versatility for carrying out processes such as nitrogen fixation, phosphate, potassium, zinc, silica, and other substrate solubilization or mineralization, release of plant growth-promoting substances (PGPSs), antibiotic synthesis, and biodegradation of soil organic matter. These processes contribute toward maintenance of soil health. Appropriately screened and applied bacterial inoculants can be a prodigious tool for increasing crop productivity besides decreasing current intensive use of chemical or synthetic fertilizers. These inoculants can help in achieving the long-desired goal of sustainable productivity with a low eco-footprint such that environmental quality conducive for the health of humans, livestock, plants, and soil can be maintained. Because the soil microbial diversity, enumerated as microbial species richness and number, can be considered as an index of soil health and fertility, bacterial genera in the rhizosphere and endosphere of the plants will indicate the health of the soil and, therefore, have a regulating effect on crop productivity. This chapter discusses various mechanisms of action of these bacteria and the beneficial effects of plant growth-promoting bacterial inoculants to realize the concept of conservation of natural resources, particularly the soil as a natural resource for sustainable crop production.