PSB — Phosphate-Solubilising Bacteria
The biofertiliser that unlocks phosphorus you already paid for — freeing fixed soil phosphate so less of your DAP is wasted.
- What it is
- Phosphate-solubilising bacteria
- Form
- Carrier-based / liquid inoculant
- Price
- Low (a few tens of ₹ per acre)
- Best for
- Unlocking fixed phosphorus (all crops)
Overview
Most soils hold a large reserve of phosphorus that plants cannot use, because it is chemically fixed to calcium, iron or aluminium. Much of the phosphorus in DAP or SSP gets fixed the same way soon after application. PSB — phosphate-solubilising bacteria such as Bacillus and Pseudomonas — release acids and enzymes that free this locked phosphorus into a form roots can take up.
Used across almost any crop, PSB improves the efficiency of your phosphorus fertiliser and taps the soil’s own reserve, so it can trim the phosphorus dose. It works especially well paired with rock phosphate or as a partner to Rhizobium/Azotobacter, and like all inoculants it complements rather than replaces the fertiliser plan.
What it is and when to reach for it
- A phosphorus-unlocking biofertiliser for almost any crop — reach for it to get more from your DAP/SSP and from the soil’s fixed phosphorus reserve.
- It pairs naturally with a nitrogen biofertiliser (Rhizobium on legumes, Azotobacter/Azospirillum on cereals).
- It is a supplement that improves phosphorus efficiency and can trim the dose, not a phosphorus fertiliser in itself.
How to use it well
- Seed treatment: coat seed with an inoculant slurry, dry in the shade, sow the same day — often combined with a nitrogen inoculant.
- Soil: mix the dose with FYM or compost and broadcast; it works well applied with rock phosphate, whose phosphorus it helps solubilise.
- Keep the soil moist and the product away from fungicides so the bacteria survive and establish.
What it can and cannot do
- A living product — store cool and shaded, keep away from agrochemicals, and use before expiry.
- It makes existing and applied phosphorus more available; it does not add phosphorus of its own, so a truly phosphorus-poor soil still needs a phosphorus source.
- Its benefit is larger where a lot of phosphorus is fixed — high-calcium (alkaline) and acidic soils both fix phosphorus heavily.
Common mistakes
- Expecting PSB alone to feed a phosphorus-poor soil — it unlocks phosphorus, it does not create it.
- Mixing it with a fungicide or strong agrochemical, which kills the bacteria.
- Storing it in heat or using it past expiry, leaving few live organisms.
Crops it is used on
Open a crop for its full nutrient schedule.
Common questions
What does PSB do?
Phosphate-solubilising bacteria release acids and enzymes that free up phosphorus locked in the soil (fixed to calcium, iron or aluminium) and the phosphorus in fertilisers that would otherwise get fixed. That makes more phosphorus available to the crop and improves the value you get from DAP or SSP.
Does PSB replace DAP?
No — it makes phosphorus more available, but it does not add any of its own. On a genuinely phosphorus-poor soil you still need a phosphorus source; PSB then helps you get more from a smaller dose. It works especially well alongside rock phosphate.
Can PSB be used with other biofertilisers?
Yes — PSB is commonly combined with a nitrogen inoculant: Rhizobium on legumes, or Azotobacter/Azospirillum on cereals and vegetables. Together they cover nitrogen and phosphorus. Just keep all of them away from fungicides and agrochemicals.
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.