Yellow leaves are one of the most common worries in the field. A crop that was dark green last week suddenly turns pale, and the farmer wonders: is it a lack of nutrients, a disease, an insect, or just too much water? The right answer matters, because spraying a fungicide on a zinc-deficient field wastes money, and giving urea to a diseased field does not help at all.
In this guide we explain, in simple words, why crop leaves turn yellow, how to tell a nutrient deficiency from a disease, and what to do in each case. The main trick is to look at which leaves turn yellow and how the yellowing looks.
Yellow leaves at a glance
A leaf is green because of chlorophyll, the pigment that makes food for the plant. When the plant cannot make enough chlorophyll, or when the leaf is damaged, it turns pale green, yellow or even white. This is called chlorosis. It can come from five groups of causes:
| Group | Typical sign | Common examples |
|---|---|---|
| Nutrient deficiency | Even yellowing in a clear pattern; the same on both sides of the leaf; whole patches of the field | Nitrogen, zinc, iron, sulphur, magnesium, potash |
| Disease | Spots, patches, mosaic, curling or wilting; spreads from plant to plant | Leaf spots, blight, wilt, rust, virus |
| Insects and mites | Pale speckles, curling, sticky honeydew, insects on the underside | Aphids, whitefly, jassids, thrips, mites |
| Water and soil problems | Yellowing after heavy rain or on low-lying patches; poor roots | Waterlogging, drought, salty or alkaline soil, compacted soil |
| Other causes | Sudden yellow-brown burn after a spray, or yellowing in cold weather | Herbicide drift, wrong spray dose, frost, heat, old age of the leaf |
The first clue: old leaves or young leaves?
Some nutrients can move inside the plant. If the soil runs short, the plant pulls them out of the old leaves and sends them to the new growth. So the deficiency shows first on the older, lower leaves. Nitrogen, potash, magnesium and phosphorus behave like this.
Other nutrients cannot move once they are placed in a leaf. Their deficiency shows first on the young, upper leaves. Iron, sulphur, zinc, manganese, calcium and boron behave like this.
The second clue: the pattern of yellowing
Look closely at one leaf. The shape of the yellow tells a lot:
- Whole leaf evenly pale or yellow: usually nitrogen (old leaves) or sulphur (young leaves). Also seen with waterlogging.
- Yellow between the veins, veins stay green: iron, magnesium, manganese or zinc. Iron shows on young leaves, magnesium on old leaves.
- Yellow starting at the tip or edge and burning brown: potash deficiency, or salt or fertiliser burn.
- Yellow spots with a brown or dark centre, or a yellow halo around a spot: a leaf spot disease (fungal or bacterial).
- Patchy light and dark green mosaic, curling, stunted plants: a virus, often carried by whitefly or aphids.
Nutrient deficiency: how to identify and correct it
The table below lists the common deficiencies. The correction doses are general ranges for a first aid spray; always read the label of the product you use, and get a soil test done so that you correct the real problem.
| Nutrient | Which leaves | How it looks | General correction |
|---|---|---|---|
| Nitrogen (N) | Old, lower leaves first | Pale green to yellow, starting from the tip in a V-shape; slow, thin growth | Top-dress urea in split doses; a 1–2% urea foliar spray (10–20 g per litre) gives a quick green-up |
| Phosphorus (P) | Old leaves | Dark green or purplish leaves, stunted plants, weak roots | Basal DAP or SSP at sowing; cold soil makes it worse |
| Potassium (K) | Old leaves | Yellow-brown scorching at the tips and edges | Muriate of potash in the soil; foliar potassium nitrate (13:00:45) about 0.5–1% (5–10 g per litre) |
| Magnesium (Mg) | Old to middle leaves | Yellow between the veins, veins stay green; leaves may turn orange or red | Foliar magnesium sulphate about 0.5–1% (5–10 g per litre); soil application as per soil test |
| Sulphur (S) | Young leaves | Whole young leaf pale yellow (looks like nitrogen, but on new growth) | Gypsum, SSP or elemental sulphur in the soil; important for mustard, pulses and oilseeds |
| Iron (Fe) | Young leaves | Yellow or whitish new leaves with green veins; common in alkaline or waterlogged soil | Foliar ferrous sulphate about 0.5% (5 g per litre) with a pinch of citric acid, or a chelated iron product |
| Zinc (Zn) | Young to middle leaves | Pale or whitish patches between veins, small leaves, rusty brown spots; "khaira" in paddy, white bud in maize | Zinc sulphate in the soil as per soil test; foliar about 0.5% (5 g per litre) |
| Manganese (Mn) | Young leaves | Pale grey-yellow patches between veins; common in wheat after paddy on light soils | Foliar manganese sulphate about 0.5% (5 g per litre) |
| Boron (B) | Growing tips | Thick, brittle, distorted young leaves; growing point dies; poor flowering | Foliar boron (20%) about 1 g per litre; do not overdose, as the margin of safety is small |
| Calcium (Ca) | Growing tips and fruit | Curled young leaves with scorched edges; blossom-end rot in tomato | Calcium nitrate foliar spray as per label; keep soil moisture even |
Foliar spray tips: spray in the early morning or late afternoon, never in hot midday sun. Wet both sides of the leaves. Try a small area first and look after 2–3 days. Do not mix many products in one tank without checking that they are compatible.
Diseases that cause yellowing
When yellowing comes with spots, patches, wilting or a fungal growth, think of a disease. The common ones are:
| Disease type | What you see | Examples |
|---|---|---|
| Fungal leaf spots and blights | Round or irregular spots, often with a yellow halo; leaves dry and fall; worse in humid weather | Early blight, leaf spot, anthracnose, powdery and downy mildew |
| Rust | Orange or yellow powdery pustules or stripes on the leaf | Yellow rust and brown rust in wheat |
| Bacterial diseases | Water-soaked angular spots; yellow wavy streaks from the leaf tip or edge | Bacterial leaf blight in paddy, bacterial spot in tomato and chilli |
| Viral diseases | Yellow-green mosaic, curling, small leaves, stunted plants; spreads with whitefly, aphids or thrips | Leaf curl in chilli and tomato, yellow vein mosaic in okra |
| Wilt and root rot | Lower leaves turn yellow, plant wilts in the day even with moisture; roots or stem base turn brown | Fusarium wilt, root rot, collar rot |
| Nematodes | Round yellow, weak patches in the field; small knots on the roots | Root-knot nematode in vegetables |
How to tell a deficiency from a disease
| Point | Nutrient deficiency | Disease or pest |
|---|---|---|
| Pattern on the leaf | Even and symmetrical; the same on both halves of the leaf | Uneven; spots, patches, or one side only |
| Pattern in the field | Follows the soil: whole field or patches that match the soil type, high or low spots | Starts at a few plants and spreads to the next plants |
| Which leaves | Old leaves or young leaves, in a clear order | Any leaves, often mixed ages |
| Other signs | No mould, no insects | Fungal growth, insects, honeydew, curling, rot |
| Spread | Does not spread from plant to plant | Spreads, especially in humid weather or by insects |
| Response | Improves after the right nutrient is given | Does not improve with fertiliser |
Step-by-step: find the cause in your field
- Note which leaves are yellow: old (lower), young (upper), or all.
- Look at the pattern: even yellow, yellow between veins, tip burn, spots, or mosaic.
- Turn the leaf over: look for whitefly, aphids, thrips, mites or white powder under the leaf.
- Check the roots and stem base: pull out one plant. Healthy roots are white and firm. Brown, rotten roots or knots point to root disease or nematodes. Cut the stem near the base: brown streaks inside point to wilt.
- Check water: is the soil waterlogged, or was there a long dry spell? Is there a low spot where water stands?
- Remember what you did in the last 10 days: a herbicide spray nearby, a new pesticide, a heavy dose of fertiliser, or a change in the weather such as cold nights.
- See the field pattern: whole field, patches, or spreading from one corner.
- Get a soil test (and, if possible, a leaf test) from a nearby soil testing laboratory or your Krishi Vigyan Kendra (KVK).
Common yellowing problems in key crops
| Crop | Common cause | What to look for |
|---|---|---|
| Paddy | Zinc deficiency ("khaira"); nitrogen shortage; iron in nurseries and dry-seeded fields; bacterial leaf blight | Rusty brown spots on young to middle leaves, stunting after transplanting (zinc); even pale green (nitrogen); yellow wavy streaks from the edge (bacterial blight) |
| Wheat | Nitrogen shortage; manganese or sulphur deficiency; yellow rust; waterlogging in winter | Lower leaves yellow (nitrogen); pale patches after paddy on light soils (manganese); yellow stripes with powder (yellow rust) |
| Maize | Nitrogen and zinc deficiency | V-shaped yellow from the leaf tip (nitrogen); pale or whitish bands on young leaves (zinc) |
| Mustard | Sulphur deficiency; white rust; aphids | Pale young leaves and poor pod filling (sulphur); white blisters under the leaf (white rust) |
| Chilli, tomato | Leaf curl virus; magnesium or calcium shortage; wilt | Curled, yellow, small leaves with whitefly (virus); yellow between veins on older leaves (magnesium) |
| Potato | Nitrogen shortage; blight; waterlogging | Lower leaves yellow (nitrogen); water-soaked spots with white mould (late blight) |
| Sugarcane, banana | Iron deficiency in alkaline soil; waterlogging | New leaves white to yellow with green veins (iron) |
How to prevent yellowing
- Test the soil every 2–3 years and fertilise by the result, not by habit.
- Split the nitrogen: give urea in 2–3 doses instead of one large dose.
- Add organic matter: well-rotted farmyard manure or compost improves nutrient supply and root health.
- Do not skip micronutrients in areas known for deficiency, such as zinc in paddy and maize.
- Fix drainage: make channels so that water does not stand in the field.
- Irrigate evenly: not too much and not too little, and avoid long dry spells followed by flooding.
- Treat seed and rotate crops to cut soil-borne disease.
- Scout every week: catch insects and disease when only a few plants are affected.
- Avoid herbicide drift: if a neighbour is spraying a herbicide, keep your crop away from the spray, and spray in calm weather.
Common mistakes
- Giving only urea for every yellow field, without checking the cause.
- Spraying a fungicide or insecticide on a nutrient deficiency, or the reverse.
- Giving more fertiliser to waterlogged plants. The roots cannot take it up, and the extra salt can burn them.
- Using more than the label dose of a micronutrient, especially boron and zinc.
- Mixing many products in one tank without checking compatibility.
- Waiting too long. Early correction is cheaper and gives a better yield.
Yellow-leaf checklist
- Are the old or the young leaves yellow?
- Is the yellowing even, between veins, at the tip, spotted or mosaic?
- Did I check the underside of the leaf for insects?
- Did I check the roots and the stem base?
- Is there waterlogging or a long dry spell?
- Did a herbicide or a new spray touch the crop?
- Did I send a soil sample for testing?
- Did I try the correction on a small area first and look again after 2–3 days?
Frequently asked questions (FAQ)
Why do the leaves of a crop turn yellow?
The main reasons are a lack of nutrients such as nitrogen, zinc, iron or sulphur; diseases such as leaf spots, wilt or virus; insects such as whitefly and aphids; waterlogging or drought; and chemical injury from a herbicide or a wrong spray dose.
How can I tell if yellowing is from nutrient deficiency or a disease?
A deficiency is usually even and symmetrical, follows the soil pattern in the field, and does not spread from plant to plant. A disease shows spots, patches, mould, wilting or curling, and spreads from plant to plant. Insects, honeydew or rotten roots also point away from a deficiency.
Why do the lower leaves turn yellow first?
This is the sign of a deficiency of a nutrient that moves inside the plant, mainly nitrogen, potash, magnesium or phosphorus. The plant pulls it from the old leaves to feed the new growth. Wilt, root rot and waterlogging can also begin with the lower leaves.
Why do the new top leaves turn yellow?
This points to a deficiency of a nutrient that does not move, such as iron, sulphur, zinc, manganese, calcium or boron. A virus or an insect attack on the growing tip can also cause yellow young leaves.
Is urea the right fix for every yellow crop?
No. Urea helps only when nitrogen is short. If the cause is zinc, iron, sulphur, a disease or waterlogging, urea will not fix it and can even harm the crop. First find the cause.
Can a foliar spray cure yellow leaves quickly?
For micronutrient and nitrogen shortages, a foliar spray can show a green-up within a few days. It is a quick first aid, not a replacement for correcting the soil. Do not use it for disease or insect damage.
Can waterlogging make leaves yellow?
Yes. In standing water the roots lack air and cannot take up nutrients, so the leaves turn yellow even if the soil has enough fertiliser. Drain the field first, then correct nutrition once the soil is workable.
Crop nutrition and protection at KisanShop
Once you know the cause, you can choose the right input. See crop nutrition products at KisanShop, fungicides for fungal diseases and insecticides for sucking pests. A few examples by nutrient are given below; read the label and dose of every product before use.
- Zinc: Agriventure Zinc Oxide 39.5% Liquid Micronutrient Fertilizer, Geolife Zinker
- Magnesium: Agriventure Magnesium Sulphate, HURL Apna Magic Magnesium Sulphate
- Iron: Katyayani Fe EDDHA Iron Chelate
- Boron: Dayal Borofert 20, Agriventure Boron 20%
- Sulphur: Dayal Fertisulf 90% Sulphur
- Potash (foliar): Agriventure NPK 13:00:45 Potassium Nitrate
- Balanced nutrition: AgriVenture NPK 19:19:19
- Calcium: Agriventure Calcium Nitrate
Also read: yellowing of paddy leaves: causes and treatment (in Hindi) and potato blight: causes, early symptoms and prevention.
Important note: This article is for general information. Nutrient doses, sprays and pesticides should be chosen after a soil or leaf test and as per the latest product label. Recommendations can change with the crop, soil, variety, weather and local conditions, so take the final decision on the advice of your nearest Krishi Vigyan Kendra (KVK) or the state agriculture department. Kisan Call Centre: 1800-180-1551 (toll free).
