A bag of vermicompost should tell you what is in it. In India the Fertiliser (Control) Order, 1985 sets the standard for vermicompost sold in packs for farming, and its numbers give you something concrete to ask any seller for, including us.
What the Order asks for
Fertiliser (Control) Order, Schedule IV: vermicompost
| Property | Requirement |
|---|---|
| Moisture | 15.0 to 25.0% by weight |
| Colour | Dark brown to black |
| Odour | Absence of foul odour |
| Particle size | At least 90% passes a 4.0 mm sieve |
| Bulk density | 0.7 to 0.9 g per cubic centimetre |
| Total organic carbon | At least 18.0% |
| Nitrogen, phosphorus, potassium | At least 1.0% N, 0.8% P2O5 and 0.8% K2O, with N, P and K together at least 2.5% |
| Heavy metals (mg per kg, at most) | Cadmium 5, chromium 50, nickel 50, lead 100 |
Judging a bag yourself
- Look: dark and granular, with no recognisable pieces of the original dung or leaves. The USDA organic programme asks for no traces of raw material.
- Smell: earthy, like soil after rain. A sharp ammonia or rotten smell means it is not finished.
- Feel: damp like a wrung-out sponge, crumbly, not dusty and not dripping.
- Rub a pinch between your fingers: it should be fine and even.
A home maturity test
Look and smell cannot tell you everything. In one study of a food-waste vermicompost, the carbon-to-nitrogen ratio and pH looked right at week seven, yet the germination index was only 58 percent, which means moderate harm to seeds. A simple check is to fill two small pots, one with plain soil and one with half vermicompost and half soil, sow ten radish or cress seeds in each, and compare how many come up in three to four days. If the vermicompost pot lags far behind, let the material cure longer.
Storing it
- Keep the bag sealed, in the shade and away from the sun and rain.
- Do not let it dry out completely or get waterlogged. Damp is right, dripping is not.
- Use it within a few months for the best result. One 180-day study of cattle-manure vermicompost in sealed bags found quality peaked around day 150 and fell afterwards. It is a single study on one feed, so take it as a guide and not a rule.
Common questions
How long does vermicompost last?
There is no firm published shelf life. One study of sealed bags found the best quality at about 150 days and a decline by 180, so using it within a few months is a sensible rule. Longer claims, such as a year or two, were not found in any source we could check.
Should vermicompost be dry or damp?
Evenly damp, like a wrung-out sponge. The Fertiliser (Control) Order allows 15 to 25 percent moisture in a pack.
What colour and smell is good vermicompost?
Dark brown to black, and with no foul smell. An earthy smell is normal.
What does the Fertiliser (Control) Order require?
For vermicompost it sets limits for moisture, particle size, organic carbon, nitrogen, phosphorus and potassium, and four heavy metals. The table above lists them.
Can I store vermicompost in plastic bags?
Yes, sealed bags are how it is sold. Keep them out of the sun and make sure the material is damp and not wet.
Terms in this guide
Sources
- Fertiliser (Control) Order, 1985, Schedule IV (consolidated copy)
- FAOLEX: Fertiliser (Control) Order text
- ICAR Research Complex for NEH Region: vermicompost production and practices
- USDA National Organic Program guidance 5021: compost and vermicompost
- Maturity and stability study of vermicompost (Iranian Journal of Environmental Health Science and Engineering, 2012)