Biofertilizers and Integrated Nutrient Management
During the second half of the 20the century, significant progress in crop production and productivity was achieved world over through increased use of chemical fertilizers. Unfortunately, this improvement was not accompanied with any major effort to maintain soil health in terms of its microbiological and nutrient components, which are so important for crop productivity. It is estimated that in the year 2025, India will need at least 300 million tonnes (MT) of food grains, the production of which would require 45 MT of nutrients. It is estimated tat  of this required nutrient, only 35 MT will be met through chemical fertilizers and the remaining 10 MT will have to be met from organic manures, crop residues and Biofertilizers.

In the soil, plant’s root system is always in close association with multitude of microorganisms and other nutrients. The microbes in root zone are maintained due to a variety of secretions from the roots and constitute what is often described as ‘rhizosphere’. These microbes in their turn supply nutrients to the soil system through their heterotrophic activity and thus supplement nitrogen and phosphorus supplied with the use of chemical and organic fertilizers. Maintenance of these microbes in the rhizosphere, therefore, is also necessary for soil health. Crop productivity and nutrient cycles, however, are integral parts of the exploitation of soil health and have led to soil degradation through nutrient depletion and erosion, so that long term strategies are needed to curtail the use of chemical fertilizers without adversely affecting crop productivity. The use of Biofertilizers, a component of biotechnology, has received increased attention in this connection, leading to increased use of Biofertilizers in our cropping systems. However, the use of chemical fertilizers can not be completely dispensed with (as shown by several experiments), so that an integrated nutrient management (INM) involving the use of Biofertilizers along with both chemical and organic fertilizers is needed. These aspects of biotechnology will be discussed in this chapter.