Sanjulata, Subuhi Nishad, Mahima Bhardwaj and Gayatri
College of Agriculture, Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.)

A biofertilizer is a natural input that contains live microorganisms that improve nutrient availability for plants by fixing atmospheric nitrogen, solubilizing phosphorus, or promoting plant growth. Sustainable agriculture is essential, and healthy soil is its foundation. One of the most natural, cost-effective, and environmentally friendly methods of improving soil fertility is to use Rhizobium, a helpful nitrogen-fixing bacterium. Rhizobium plays an important function in increasing crop yields while decreasing reliance on chemical fertilizers.

Rhizobium: A Nitrogen-Fixing Biofertilizer
Rhizobium which is found mostly in leguminous plants has the ability to colonize plant roots and encourage nodulation, enlarge cell elongation, and increase chances of bacterial association. Rhizobacteria residing in root nodules fix nitrogen into ammonia by the involvement of nitrogenase enzyme that helps in plant growth. Inoculation of these nitrogen-fixing microorganisms along with legume plants enhanced availability of N nutrient when plants are grown in soil that is scarce in the nutrient. Their symbiotic association sustains for a long time and increases various agronomic implications and facilitates N utilization. Indeed, a more understanding and management of N-fixing microorganisms could be initiated (Santi et al. 2013) to benefit the farmers through knowledge awareness. Sahgal and Johri (2003) reported that several genera of nitrogen-fixing microorganisms are able to fix N in a diverse range of plant species. Rhizobium has a symbiotic connection with leguminous plants (including chickpeas, soybeans, lentils, peas, and beans).

Why Rhizobium is Important as a Biofertilizer
  • Biological Nitrogen Fixation (BNF): Nitrogen gas (N₂) from the air is transformed by rhizobium into ammonia (NH₃), a type of nitrogen that plants may utilize.
  • Crop-Specific Efficiency: Certain strains of rhizobium are compatible with particular legumes, including beans, peas, soybeans, lentils, and chickpeas.
  • Reduces Need for Chemical Fertilizers: Rhizobium reduces the expense and environmental effect of chemical fertilizer use by providing nitrogen naturally.
Importance of Rhizobium Biofertilizer

1. Natural nitrogen fixation
Rhizobium bacteria develop symbiotic relationships with leguminous plants, converting atmospheric nitrogen into ammonia. This provides a natural source of nitrogen, which is necessary for plant growth, without the need for synthetic nitrogen fertilizers.

2. Improves Soil Fertility
Rhizobium contributes to the preservation and enhancement of long-term soil health by supplementing the soil with nitrogen that is biologically accessible. Additionally, it increases microbial activity, which benefits the soil environment.

3. Reduces Chemical Fertilizer Dependency
Rhizobium reduces the need for nitrogen-based chemical fertilizers, which:
  • Lowers input costs for farmers
  • Minimizes soil and water pollution
  • Reduces greenhouse gas emissions from fertilizer production and use

4. Boosts Crop Yield and Quality
Legume crops treated with Rhizobium show:
  • Higher biomass and grain yields
  • Better quality produce with improved protein content
  • More vigorous plant growth, especially under low-input conditions

5. Environmentally Sustainable
Rhizobium is eco-friendly and biodegradable. Its use:
  • Prevents chemical buildup in the soil
  • Promotes climate-resilient agriculture
  • Supports organic and sustainable farming practices

6. Encourages Crop Rotation and Diversification
Rhizobium-enriched legume crops enhance the soil conditions for later non-legume crops (like cereals), increasing the yield and profitability of crop rotation

7. Enhances Efficiency in Integrated Nutrient Management (INM)
When used along with other biofertilizers (like phosphate-solubilizing bacteria) and organic inputs, Rhizobium contributes to a balanced nutrient supply, improving overall nutrient use efficiency.

Application Methods

1. Seed Treatment (Most Common)
  • Prepare a Jaggery/Gum Solution: Dissolve 50 g of jaggery in 500 ml of lukewarm water (acts as a sticker).
  • Mix with Rhizobium Culture: Add the Rhizobium culture (approx. 200g per 10-12 kg of seeds).
  • Coat the Seeds: Mix the seeds in the solution thoroughly until coated.
  • Dry in Shade: Spread treated seeds in the shade for 30 minutes. Do not expose to direct sunlight.
  • Sow Immediately: Use treated seeds within 24 hours for best results.

2. Seedling Root Dip Method (For transplanted legumes)
  • Mix Rhizobium in water (1 packet in 10–15 liters).
  • Dip roots of seedlings for 15–30 minutes before transplanting.

3. Soil Application (Less common, for large-scale fields)
  • Mix 1–2 kg of Rhizobium culture with 25 kg of compost or FYM (farmyard manure).
  • Broadcast uniformly over 1 acre before sowing.
Precautions During Application
  • Do not mix Rhizobium with fungicides, chemical fertilizers, or pesticides.
  • Use fresh, unexpired culture specific to the crop.
  • Maintain shade and moisture when treating seeds.
  • Store the culture in a cool, dry place, away from sunlight.
  • Inoculant strains are crop-specific (e.g., Rhizobium japonicum for soybean, Rhizobium leguminosarum for peas and lentils).
Crops That Benefit from Rhizobium
Rhizobium is used with leguminous crops, such as: Chickpea(Gram), Pigeon pea (Arhar),Soybean,Lentil(Masoor),Groundnut,Pea,Blackgram(Urad),Greengram (Moong),Cowpea.




Recommended Dose of Rhizobium
  • Seed Treatment: 200 grams per 10-12 kg seeds (1 acre)
  • Soil Application: 1–2 kg/acre with FYM or compost
Tips for Farmers
  • Combine Rhizobium with phosphate solubilizing bacteria (PSB) for better growth.
  • Use in combination with organic farming or INM (Integrated Nutrient Management).
  • Practice crop rotation with legumes to naturally boost nitrogen in fields.
Benefits of Using Rhizobium

1. Improves Soil Fertility:
By fixing atmospheric nitrogen, Rhizobium naturally replenishes soil nutrients.

2. Reduces Fertilizer Costs:
Farmers can save on nitrogen fertilizers, as Rhizobium provides free nitrogen to the crop.

3. Increases Crop Yield:
Healthier soil leads to better crop productivity and higher-quality produce.

4. Environmentally Friendly:
Reduces the carbon footprint and soil degradation caused by chemical fertilizers.

5. Enhances Long-Term Soil Health:
Promotes biological activity and microbial balance in the soil.

Conclusion
Rhizobium biofertilizer is a powerful tool in sustainable agriculture, especially for legume cultivation. Its natural nitrogen-fixing ability helps reduce dependence on chemical inputs, improves soil health, and supports eco-friendly farming practices. Promoting its use can lead to better crop productivity and environmental conservation.

References:

Sahgal M, Johri BN (2003) The changing face of rhizobial systematics. Curr Sci 84:43–48

Santi C, Bogusz D, Franche C (2013) Biological nitrogen fixation in non-legume plants. Ann Bot 10:1–25