How Much Organic Fertilizer Does One Pot Need? A Dosage Guide by Container Size
Almost every organic fertiliser bag sold in Sri Lanka tells you what is inside it and almost none tells you how much to use. So people guess. They guess high, because more food sounds like more growth, and then they wonder why the leaves yellowed and the plant stopped.
Over-feeding is the single most common way home gardeners damage healthy plants. This guide gives you actual quantities — by pot size, by bed area, and by how often.
Why Too Much Is Worse Than Too Little
An under-fed plant grows slowly and looks pale. It is alive, and it recovers within a fortnight of being fed. An over-fed plant is a harder problem.
Concentrated fertiliser raises the salt level in the soil around the roots. When the soil outside the root holds more dissolved salt than the root does, water moves out of the root instead of in. The plant dehydrates while sitting in damp soil — which is why over-feeding and under-watering look identical: drooping, crisp leaf edges, stalled growth.
The usual response is to water more, which does not help, and the plant declines over a week or two. Starting low and increasing is always the safer direction.
Pellets and Granules: By Pot Size
These quantities suit composted, pelletised manure — the Eco Max Green Boost, Bio Bull and Eco Max Lusty type of product. Apply to the soil surface, keep it away from the stem, then water it in.
- Small pot, up to 15cm / 6in across (herbs, a single chilli) — about 1 tablespoon, roughly 15g. Every 6–8 weeks.
- Medium pot, 20–25cm / 8–10in (one tomato, brinjal, capsicum) — 2 to 3 tablespoons, roughly 30–45g. Every 6 weeks.
- Large pot or grow bag, 30cm / 12in and up — a small handful, roughly 60–75g. Every 6 weeks.
- Raised bed or open ground — 100–150g per square metre for cow or goat manure; 60–100g per square metre for chicken manure, which is considerably stronger.
A level tablespoon of dry pellets is about 15g, and a cupped adult handful is about 60–70g. You do not need scales — but do use the same spoon each time rather than estimating by eye, which drifts upward.
Powders: Use Roughly Two Thirds
Powdered manure such as the chicken manure powder (Rs 245), cow manure powder (Rs 250) or goat dung powder (Rs 250) acts faster than pellets because there is more surface area for soil organisms to work on.
Use about two thirds of the pellet quantities above, and mix powder into the top few centimetres of soil rather than leaving it on the surface where it cakes and sheds water.
Compost Is the Exception
Finished compost is a soil improver as much as a fertiliser, and the nutrients in it are mild and slow. You can be far more generous.
For Eco Agri Natural Organic Compost (Rs 440):
- In pots: up to a third of the total volume when you first fill them.
- Topping up an existing pot: a 2–3cm layer on the surface, two or three times a year.
- In beds: a 3–5cm layer worked through before planting each season.
It is genuinely difficult to harm a plant with properly finished compost. If you want one product you cannot get wrong, this is it.
Timing Through a Plant’s Life
How much matters, but so does when. The same dose helps or hurts depending on the stage.
- Before sowing or transplanting: work compost or cow manure through the soil. Skip the strong nitrogen products entirely.
- Seedlings, first 2–3 weeks: feed nothing. Young roots burn easily and there is enough in the growing medium already.
- Active leaf growth: this is when nitrogen earns its place. Chicken manure for leafy crops, goat or compost for everything else.
- At first flowering: stop the high-nitrogen feeds. Nitrogen now produces leaves at the expense of fruit — the classic enormous, beautiful, fruitless tomato plant.
- While fruiting: light compost or slow-release pellets only, every 6–8 weeks.
- After each cut of leafy greens: a small nitrogen dose to drive the next flush.
Reading the Plant
Quantities are a starting point. The plant will tell you whether you got it right.
Signs of too little: pale or yellowing older leaves at the bottom first, slow growth, small leaves, weak stems. Feed at the normal rate and expect improvement within two weeks.
Signs of too much: crisp brown leaf edges or tips, sudden wilting in moist soil, a white crust on the soil surface, lots of dark green leaf and no flowers. Stop feeding, and water deeply and repeatedly to flush the excess through. In a pot, water until it runs freely from the bottom, three or four times over a week.
Our guide to the signs your plants are unhealthy works through the other causes that look similar.
Four Rules That Prevent Most Problems
- Water before and after feeding. Nutrients travel in water, and concentrated fertiliser against dry roots is how burn happens.
- Keep it off the stem. Apply in a ring a few centimetres out from the base. Fertiliser piled against a stem invites rot.
- When unsure, halve it. You can always add more in a fortnight. Pulling it back out is not an option.
- Feed on a schedule, not on impulse. Write the date somewhere. Most over-feeding happens because nobody remembers when they last fed.
If You Would Rather Not Measure
Slow-release pellets are the forgiving option — they meter themselves out over weeks, so a slightly heavy hand matters far less. Eco Max Lusty is designed for that.
Our Beginner Home Garden Kit (Rs 1,699) also arrives with the quantities already proportioned to what is in it, which removes the arithmetic for a first garden.
And if you have been feeding generously because the plants looked unhappy, try the opposite for a month. In home gardens, it is more often too much than too little.
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