Rhizobium (nitrogen-fixing biofertiliser)
A living seed treatment for legumes — the bacteria that let a pulse crop make much of its own nitrogen from the air.
- What it is
- Symbiotic N-fixing bacteria
- Form
- Carrier-based / liquid inoculant
- Price
- Low (a few tens of ₹ per acre)
- Best for
- Pulses & legumes (seed treatment)
Overview
Rhizobium is a nitrogen-fixing bacterium used as a seed inoculant on legumes — gram, arhar, moong, urad, soybean, groundnut and others. It enters the roots and forms nodules where it converts atmospheric nitrogen into a form the plant can use, in a genuine two-way partnership: the crop feeds the bacteria sugars, the bacteria feed the crop nitrogen.
On a well-nodulated legume this can supply a large share of the crop’s nitrogen, so a small, cheap packet reduces the urea bill and leaves residual nitrogen for the next crop. The catch is that Rhizobium is strain-specific — the strain for gram will not nodulate groundnut — so you must use the inoculant meant for your crop group.
What it is and when to reach for it
- A nitrogen-fixing seed inoculant for legumes only — reach for it whenever you sow pulses, groundnut or soybean.
- It is strain-specific: use the Rhizobium meant for your crop group, not a generic one.
- It is a supplement, not a full nitrogen replacement — it reduces the nitrogen dose rather than removing it, and legumes still need phosphorus and sulphur.
How to use it well
- Seed treatment: make a slurry of the inoculant (with a little jaggery or gum solution as sticker), coat the seed evenly, dry it in the shade, and sow the same day.
- One packet (about 200 g) usually treats the seed for one acre — follow the pack rate for your crop.
- Treat with Rhizobium last, after any fungicide seed treatment, and keep the two from direct contact — fungicides kill the bacteria.
What it can and cannot do
- It is a living product with a short shelf life — store it cool and in the shade, never in the sun, and use it before the expiry date.
- Nodulation is best on soils with decent organic matter and the right moisture; poor, dry or very acidic soils fix less.
- It fixes nitrogen only for the legume it is partnered with — it does nothing for a cereal.
Common mistakes
- Using the wrong crop’s strain, so the bacteria never form effective nodules.
- Mixing it straight with a fungicide-treated seed or an agrochemical, which kills the culture.
- Storing the packet in the sun or heat, or using it after expiry, so most of the bacteria are already dead.
Crops it is used on
Open a crop for its full nutrient schedule.
Common questions
Which crops is Rhizobium used for?
Legumes only — pulses like gram, arhar, moong and urad, plus groundnut and soybean. It forms nitrogen-fixing nodules on legume roots and does nothing for cereals like wheat or rice, which use Azotobacter or Azospirillum instead.
How do I treat seed with Rhizobium?
Make a slurry of the inoculant with a little jaggery or gum solution as a sticker, coat the seed evenly, dry it in the shade (never in the sun), and sow the same day. Roughly one 200 g packet treats an acre of seed. Apply it after any fungicide seed treatment, not mixed with it.
Does Rhizobium replace nitrogen fertiliser?
It reduces it, not fully replaces it. A well-nodulated legume fixes a large part of its own nitrogen, so you can cut the nitrogen dose — but the crop still needs phosphorus and sulphur, and a small starter dose of nitrogen is often still given at sowing.
Composition and doses follow ICAR / Soil Health Card guidance; prices are the notified subsidised rates for the season shown and are guidance, not a quote. A soil test for your field always beats a general rate. See our editorial policy.