Role of Root Nodule Bacteria in Improving Soil Fertility and Growth Attributes of Leguminous Plants Under Arid and Semiarid Environments

Abstract

In the late seventeenth century, tools of modern science began to reveal the secrets of plant nutrition, and nitrogen, phosphorus, and potash were identified as essential nutrients for plant growth. The soil was assumed to be the source of phosphorus and potash, but it has been a matter of argument up to nineteenth century that either plants absorb nitrogen from the air or extract it from the soil. Schultz-Lupitz (1881) revealed that the plants required more nitrogen than any other soil nutrient and leguminous plants were able to accumulate large amounts of nitrogen. The nodules attached to the roots of leguminous plants were responsible for converting nitrogen gas of the atmosphere into soluble nitrogenous compounds (Hellriegel 1887; Hellriegel and Wilfarth 1888). Presently, this marvelous piece of natural chemistry is known as the symbiotic association between leguminous plants and a soil bacterium. Plant-bacteria interactions in the rhizosphere are the determinants of plant health and soil fertility (Hayat et al. 2010). It is now well established that the leguminous plants enhance soil fertility and non-leguminous plants deplete it. The intensive use of chemical fertilizers has degraded soil fertility resulting in severe health and environmental hazards such as soil erosion, water contamination, pesticide poisoning, falling groundwater table, water logging, and depletion of biodiversity. The plant-microbe interactions in the rhizosphere play an essential role in transformation, mobilization, solubilization of nutrients, and uptake of essential nutrients by plants. The soil bacteria supply nutrients to crops, stimulate plant growth, control or inhibit the activity of plant pathogens, improve soil structure, bioaccumulation, or microbial leaching of inorganics, etc. (Ehrlich 1990), and have been used in crop production for decades (Davison 1988). It has