8 - Plant growth-promoting diazotrophs: Current research and advancements

Abstract

Nitrogen is an essential element for plant growth and is made available to plants by the diazotrophs. These organisms are also involved in the supply of other growth-supporting components such as indole acetic acid, phosphates, potassium, iron, etc. Hence, these diazotrophs are referred to plant growth-promoting (PGP) diazotrophs. Increased demands for food production require increased nitrogen supply, which is met by the use of synthetic fertilizers, compromising soil health and agricultural sustainability. Biological nitrogen fixation is the solution to overcome this problem. Optimizing nitrogen fixation will help in meeting the increasing demands of growing populations. Therefore, we need good nitrogen-fixing microorganisms having plant growth-promoting properties, their mechanisms need to be thoroughly studied, their applicability to all crop types should be researched, and efficient formulations of plant growth-promoting diazotrophs should be made available for sustainable agricultural practices. This chapters covers nitrogen fixation in terrestrial soils and in the marine ecosystem, general mechanism of nitrogen fixation, other beneficial mechanisms of plant growth promotion harbored by diazotrophs, recent genomic advances in the field, diazotrophs used as biofertilizers and available in the global market, and use of biofertilizers in agriculture. It also highlights the challenges to the application of PGP diazotrophs to nonleguminous crop plants.