Leaf Color Chart for Rice: How to Read It and When to Add Urea
A leaf color chart is a plastic strip with four shades of green that tells you when palay needs nitrogen. You hold a rice leaf against it, match the color, and add urea only when most leaves read too pale. It is a cheap way to feed the crop by what it shows you, not by habit.
Farmers call it the LCC. It is a fast, handy field tool that measures how green a leaf is, and that greenness follows the plant's nitrogen. The panels run from number 2, a yellowish green, to number 5, a dark green. So a pale reading on enough leaves means the crop is running short, and a top dressing of urea fertilizer will pay.
The chart does one job only. It reads nitrogen, not phosphorus, potassium or zinc. For the whole season, start from our rice fertilizer schedule, then let the chart fine tune each urea dose.
When to start reading the leaf color chart
Take the first reading 14 days after transplanting (DAT). In direct wet seeded rice, start at 21 days after sowing (DAS). If you put 14 14 14 with sulfur into the soil or as a top dressing at 14 DAT, wait and begin at 21 DAT instead.
After that, read the field every 7 days until the first flowers appear. Some guides give a range of every 7 to 10 days, up to 5 to 10 days after panicle initiation. Both stop around flowering, because heavy nitrogen late in the season invites lodging, pests and unfilled grains.
| Crop | First reading | Then | Last reading |
|---|---|---|---|
| Transplanted rice | 14 DAT, or 21 DAT if 14 14 14 with sulfur went on at 14 DAT | Every 7 days | First flowering |
| Direct wet seeded rice | 21 DAS | Every 7 days | First flowering |
How to read a leaf color chart, step by step
Choose 10 healthy hills
Walk into a part of the lot where the stand looks even and pick 10 hills at random, away from the bund. Skip plants with disease spots or insect damage. Some guides use 12 hills, and more hills give a steadier average.
Pick the right leaf
On each hill, take the topmost leaf that has fully opened. It is the youngest full leaf, and it shows the plant's nitrogen best. Keep it on the plant, since you only need to lay it on the chart.
Lay the middle of the leaf on the chart
Hold the leaf so its middle lies on the color strips, and pick the panel that matches best. If it falls between two panels, write the average, so a leaf between 3 and 4 reads 3.5.
Shade it with your body
Stand with the sun at your back so your body shades both the leaf and the chart. Direct sunlight changes how the green looks. The best time to read is between 8 and 10 in the morning.
Same reader, same hour
Let one person take every reading at about the same time of day, all season. Then use a fresh set of 10 leaves each week.
Count the low leaves
Write down all 10 readings. After that, count how many fall below the critical value for your crop.
The critical value: 4 for transplanted rice, 3 for direct seeded
The critical value is the line between enough nitrogen and too little. It is 4 for transplanted rice, inbred or hybrid, and 3 for direct wet seeded rice.
The rule itself is simple. If 6 or more of your 10 leaves read below the critical value, top dress nitrogen. If 5 or fewer fall below it, skip the urea this week and read again in 7 days. That one habit stops you from feeding a crop that is still green enough.
| Season | Nitrogen per hectare | Urea per hectare | Urea for a quarter hectare |
|---|---|---|---|
| Dry season | 30 kg | 1.5 bags (75 kg) | About 19 kg |
| Wet season | 23 kg | 1 bag (50 kg) | About 12.5 kg |
Why the dry season gets more
The dry season brings more sunshine, so a healthy crop can turn more nitrogen into grain. A wet season crop gets less light, and extra nitrogen then mostly adds leaves, lodging and disease. That is why the wet season dose is smaller, and our guide to fertilizer for wet season rice goes further.
How to apply the urea
- Keep a shallow 2 to 3 cm of water in the paddy as you spread it, and close the outlets so the fertilizer stays in your field.
- Spread it in the afternoon, after 3 PM, when cooler air means less nitrogen escapes as gas.
- Broadcast evenly so no corner gets a double dose.
- Use urea for these doses. Leave out ammonium sulfate here, since the basal 14 14 14 with sulfur already gives the crop enough sulfur.
Check that the yellow really comes from nitrogen
A pale leaf does not always mean hunger. Before you buy urea, walk the lot and rule out these other causes. Our guide to yellow rice leaves goes deeper.
- Brown planthopper. Round patches turn yellow, then brown and dry, with insects crowded at the base of the hills. See brown planthopper.
- Tungro. Leaves turn yellow to orange from the tip down, and stunted plants show up in patches. See rice tungro.
- Zinc shortage. Dusty brown spots appear on the upper leaves of stunted plants, 2 to 4 weeks after transplanting.
- Sulfur shortage. The young leaves yellow first, while nitrogen shortage yellows the older, lower leaves first.
- Potassium shortage. Plants stay dark green, but older leaves get yellowish brown edges or dark brown spots near the tips.
- Water stress. Drought rolls the leaves and dries the tips. Deep water for a week or more leaves few tillers and dark roots.
Our page on nutrient deficiency in rice shows each sign side by side. If pests or disease explain the color, urea will not fix it, and it can even make the problem worse.
Common leaf color chart mistakes
- Reading in full sun, which changes the shade you see.
- Picking an old lower leaf, or a torn and spotted one, instead of the youngest full leaf.
- Sampling only beside the bund, where plants do not show the field's average.
- Reading 3 or 4 leaves instead of 10, so one odd plant decides the dose.
- Adding urea when only 4 or 5 leaves read low. The rule asks for 6 or more.
- Changing readers, or reading at noon one week and at 4 PM the next.
- Reading on after flowering, when the weekly checks should have ended.
- Expecting the chart to show phosphorus, potassium or zinc. It reads nitrogen only.
Write the date, the lot and all 10 readings every week. After two or three seasons, you will see how each lot behaves, and you will buy urea with more confidence.
Let Anee read the leaves for you
In anee.io, the LCC Checker brings the chart to your phone. Take photos of your leaves, and Anee, the smart farm technician, reads the color and tells you how much urea to add. If you prefer the plastic chart, write the readings in a note on the lot.
The weekly reading also fits your season plan. On the cropping calendar, add a leaf check every 7 days from 14 DAT, and each lot gets its own dates from its own transplanting day. When you top dress, the farm inventory takes the bags of urea out of stock and adds their cost to your expenses.
Sign up free, set each lot's transplanting date, and anee.io dates every leaf reading and urea dose for you.
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