What Does “Inoculated” Mean in Planting Nitrogen-Fixing Trees?
Inoculation in this context refers to adding beneficial bacteria (specifically Rhizobia) to the roots or seeds of a nitrogen-fixing plant to help it form root nodules—those little bumps where nitrogen fixation actually happens.
Why Inoculate?
Not all soils naturally contain the specific Rhizobia strains that match a tree species. Without them, the tree won’t fix nitrogen efficiently, even if it’s a legume.
Inoculation ensures the right microbial partner is there from the start.
How It Works:
- You coat seeds or roots of nitrogen-fixing plants (like Caesalpinia pulcherrima, Gliricidia, Leucaena, etc.) with a special powder or slurry that contains live Rhizobia bacteria.
- After planting, the bacteria infect root hairs and form nodules.
- Inside those nodules, bacteria convert atmospheric nitrogen (N₂) into plant-usable nitrogen (ammonia).
How to Inoculate (Basic Methods):
For Seeds:
- Mix seeds with a moistened Rhizobium inoculant.
- Coat seeds evenly in a slurry or powder form.
- Let dry in the shade for 20–30 minutes before planting.
For Seedlings:
- Dip roots in a Rhizobium slurry before transplanting.
- Or, mix inoculant into the soil or compost in the planting hole.
Where Do You Get Inoculants?
- Available from agricultural supply stores or biofertilizer suppliers.
- Specific inoculants are labeled for “leguminous trees” or even for certain genera (like Leucaena, Acacia, etc.).
- Some research centers (like Biotech-UPLB) also produce custom inoculants.
Summary:
| Term | Meaning |
|---|---|
| Inoculant | A product containing beneficial nitrogen-fixing bacteria. |
| Inoculation | The act of adding these bacteria to seeds or roots. |
| Goal | To ensure effective nitrogen fixation via root nodule formation. |