Demands of safe and healthy food, sustainable production system and long-term maintenance of soil health and environmental pollution has made organic farming a key priority area across the globe. Though, the complete avoidance of chemical inputs in agriculture is inevitable for sustainable food security but there are huge opportunities of organic farming in the selected crops and niche areas for domestic as well as international market. Bio fertilizers are the organic formulations/preparation which contain the live efficient strains of nitrogen fixers, phosphate solubilizes or cellulolytic microorganisms used as seed treatments or soil application. The bio fertilizer application accelerates microbial degradation of complex organic matter and increases the availability of various nutrients essential for plant growth.

                Biological nitrogen fixation accelerated by nitrogen fixing bio fertilizer i.e. Rhizobium, Azotobacter etc. both as symbiotic and/or free living N fixers enhance the soil fertility by fixing atmospheric N. Also, phosphate solubilizing bacteria (PSB) help in mineralization of organic phosphates and produces the plant available P during the cropping season (Mahdi et al., 2010). Bio fertilizer are known as naturally available biological systems of nutrient mobilization. Though the bio fertilizer have several beneficial effects both in organic farming and integrated nutrient management practices, but this technology is remained under popularized among the farmers, especially in Asian region. In case of India, only 30% of net cultivable area falls under irrigated condition and rest of the 70% area is covered by rain-fed conditions where a negligible amount of fertilizers is added to soil by the farmers.

                In India, the agricultural production system of rain-fed area is largely depends on the readily available organic manures (by default organic production system) as a sources of nutrients for the crops grown in these areas. Especially the North-Eastern Himalayan (NEH) region of India has high potential for organic farming. With sizable acreage (>18 Mha) of NEH region can be potentially use for organic/natural farming and thus this region can be emerged as a hotspot of organic products in World’s organic market (Venkatashwarlu, 2008). Bio fertilizer play a crucial role in mineralization/decomposition of fixed/non-available nutrient present in the soil system. Thus, use of bio fertilizer along with organic manures can be the potential alternative for maintaining the long-term soil fertility and soil organic matter under the organic farming systems, especially in the arid, semi-arid and sub-humid climate soils of India.

Bio fertilizer are need of hour

Since the initiation of green revolution  in India, indiscriminate and non-judicious use of synthetic fertilizers have degraded the agricultural ecosystem in many folds. Continuous use of synthetic fertilizers and other agro-chemicals has led to increase in cost of cultivation for the marginal and small farmers in India. In this scenario, adoption of organic/natural farming by the small and marginal farmers will not only reduce the cost of production but also maintain the long-term soil and environmental health too. Long-term use of on-farm inputs along with Bio fertilizer is eco-friendly, economical, more efficient and productive and moreover it is accessible to the marginal and small farmers at very low cost. Increased availability of insoluble soil nutrients to the crops with use of bio fertilizer and long-term positive impacts of bio fertilizer and organic manures on soil physico-chemical and biological properties are the two major benefits of bio fertilizer use in modern scientific agriculture (Kumar et al., 2018).

Important Bio fertilizers

Based on the nutrients mobilized by the bio fertilizer, they have been grouped as follows:

Ø  Nitrogen fixing bio fertilizer

Ø  Phosphate solubilizing Bio fertilizer

Ø  Bio fertilizer mobilizing the micronutrients

Ø  Plant growth promoting Rhizobacteria

Nitrogen fixing bio fertilizer

The nitrogen fixing bio fertilizer converts the elemental nitrogen into plant available N forms. Among the N fixing bio fertilizer, groups of microorganisms or microbial inoculants, which can fix the atmospheric N into plant available forms, are included. Further, based on their nature, these groups of microbes are divided into various categories viz. free living, symbiotic, blue green algae, leguminous and non-leguminous species etc. Table 1 contains the details of different groups of microbes able to fix the atmospheric nitrogen.

Table 1. Different types of nitrogen fixing bio fertilizer (These bio fertilizer can be purchased by the farmers from different ICAR institues/SAUs/KVKs)

Phosphate solubilizing Microorganisms

                Phosphorus has high fixing nature in the soil as soon as it is applied (15-20% use efficiency). Many bacterial inoculums through production of low molecular weight organic acids have ability to dissolve the insoluble organic and inorganic phosphate compounds i.e. tricalcium phosphate, dicalcium phosphate, rock phosphate and hydroxyapatite. These PSMs increase the availability of phosphorus in soil through various mechanisms i.e. lowering the soil pH, chelation, mineralization, production of siderophores. Table 2 contains the details of different phosphate solubilizing microorganisms.

Table 2. Different types of phosphate solubilizing microorganisms.