Symbiotic nitrogen fixation and nodulation
The biological interaction between Rhizobium and host legume roots is highly host-specific.
- Bacteria enter plant root hairs, inducing the formation of specialized root nodules.
- Inside active nodules, the bacterial enzyme nitrogenase reduces atmospheric nitrogen into plant-available ammonia.
- Healthy active nodules display a pink or reddish interior due to leghemoglobin, an oxygen-binding protein.
- Leaves significant residual nitrogen in the soil, benefiting succeeding cereal crops in crop rotation systems.
Crops and matching Rhizobium cross-inoculation groups
Using the correct bacterial strain matching the specific pulse or oilseed crop ensures effective nodule formation.
- Chickpea (Gram): Rhizobium ciceri specific to chickpea root systems.
- Pigeon Pea and Cowpea: Bradyrhizobium species adapted to red gram, cowpea, and green gram.
- Soybean: Bradyrhizobium japonicum specialized for soybean nodulation.
- Groundnut: Specific cowpea miscellany Rhizobium strains.
- Lentil and Field Pea: Rhizobium leguminosarum bv. viciae.
Seed inoculation method and best practices
Proper seed treatment technique ensures high viable bacterial cell counts on the seed coat.
- Preparation: Dissolve 50 grams of jaggery in 500 ml of boiled, cooled water to make a sticky carrier slurry.
- Inoculation: Mix the biofertilizer packet (typically 200 g per 10 to 15 kg of seed) gently with the jaggery slurry and coat seeds evenly.
- Drying: Shade-dry the inoculated seeds on a clean plastic sheet for 30 minutes; never expose treated seeds to direct sunlight.
- Compatibility: If treating seeds with chemical fungicides or insecticides, apply chemicals first, allow to dry, and apply Rhizobium biofertilizer immediately before sowing.
Official source
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National Centre of Organic and Natural Farming (NCONF) ↗Related on KisanPe
Common questions
How can a farmer check if Rhizobium nodules are actively fixing nitrogen?
Cut open a root nodule with a sharp blade; if the internal tissue is pink or red, it contains leghemoglobin and is actively fixing nitrogen.
Why is jaggery water used during Rhizobium seed treatment?
Jaggery solution acts as a sticky binder that adheres bacterial cells securely to the seed coat while providing initial carbohydrates to nourish the bacteria.
Can Rhizobium biofertilizer be applied to wheat or rice?
No, Rhizobium forms symbiotic nodules exclusively with leguminous crops; non-legumes like rice and wheat require free-living or associative biofertilizers like Azotobacter or Azospirillum.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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