Selection and Application of Soil Bacterial Elite Strains as Biofertilizers for the Reclamation of Deteriorated Soil Health

In semi-arid to arid climates, soils generally have a low nutrient content, suffer from severe erosion and desertification, and undergo intensive agricultural practices and continued human activities, including overgrazing and mining. To improve low crop yield in those deteriorated soils, farmers generally use agrochemicals such as pesticides and chemical fertilizers, which are costly and whose uncontrolled and excessive use causes serious environmental damage. Appropriate management approaches are being developed by researchers nowadays to mitigate the negative effects of these environmental stresses. The use of biofertilizers based on plant growth-promoting rhizobacteria (PGPR), nitrogen-fixing bacteria such as rhizobia, emerges as an attractive, sustainable, inexpensive, and, above all, environment-friendly alternative are viable options for crop production. Basically, biofertilizers improve soil fertility and rehabilitate soils affected by many negative environmental problems such as soil salinity, acidity or alkalinity, and metal contamination. The PGPRs have specific mechanisms that allow them to survive and thrive, and even help plants to overcome environmental stresses. These bioagents are considered powerful tools to improve soil health and provide substantial benefits to agriculture. In this chapter, we review recent updates on the selection criteria of elite PGPR strains for their application as biofertilizers for increasing crop yield and improving the health of soils in regions severely affected by various abiotic stresses.