Cotton Nutrient Deficiency: Signs, Causes and the Fertilizer That Fixes It
Cotton nutrient deficiency is one of the first things to check when the leaves of your bulak (cotton) turn yellow, purple or burnt at the edges. On Philippine farms the usual ones are nitrogen, potassium, boron, magnesium, phosphorus, sulfur and zinc. This guide shows where each one starts, how to be sure, and the fertilizer that fixes it.
Start with one question: did the change begin on the old leaves or on the young ones? Nitrogen, potassium, magnesium and phosphorus move inside the plant, so a shortage shows on the old, lower leaves first. But boron, sulfur and zinc stay where the plant first put them, so the young leaves and the growing tip show it first. After that, the color and the pattern narrow down which cotton nutrient deficiency you have, and a soil test confirms it. Each one below has its signs, its causes and its fix.
Cotton nutrient deficiency signs, old leaves and young leaves
Shows first on the old leaves
| Nutrient | Where it starts | What you see | Fix with |
|---|---|---|---|
| Nitrogen | old, lower leaves, the whole plant | Lower leaves turn pale yellow, then reddish. Plants stay short with few fruiting branches and shed their squares. | Urea 46 0 0, Complete 14 14 14 |
| Potassium | old, lower leaves, leaf edges and tips | Yellow white mottling on leaf tips and edges that turns brown. Leaves curl, turn reddish brown and drop early, and bolls stay small. | Muriate of potash 0 0 60, Sulfate of potash 0 0 50 |
| Magnesium | old, lower leaves, between the veins | Lower leaves turn purple red between green veins, then drop early. | Magnesium sulfate (Epsom salt), Dolomite |
| Phosphorus | old, lower leaves, the roots | Dark green, stunted plants with reddish purple old leaves and late flowering. | 16 20 0, Complete 14 14 14 |
Shows first on the young leaves
| Nutrient | Where it starts | What you see | Fix with |
|---|---|---|---|
| Boron | young leaves and the tip, fruit, grain or tubers | Dark green rings on the leaf stalks, many squares and young bolls dropping, and small, misshapen bolls. | Borax, Solubor |
| Sulfur | young leaves and the tip, the whole plant | The young top leaves turn pale green to yellow while the old leaves stay green. Plants are small and spindly. | Ammonium sulfate 21 0 0, Superphosphate 0 20 0 |
| Zinc | young leaves and the tip, between the veins | Young leaves thick, leathery and cupped upward, yellow between the veins, on short, bushy plants. | Zinc sulfate |
Before you buy fertilizer for a cotton nutrient deficiency
So use the table to pick the likeliest cotton nutrient deficiency, then read its section below. Also keep in mind that dry soil, standing water, cold nights, a pest or a disease can look the same. That is why it pays to check the roots and the whole field first.
Nitrogen deficiency in cotton
The older, lower leaves turn light green, then evenly yellow, often starting at the leaf tip. In bad cases the yellow leaves turn red and then die. Plants stay short and weak, with small leaves, few fruiting branches and few nodes, and they hold fewer squares and bolls. You see it most at this stage: squaring to boll filling, when most of the nitrogen goes into the fruit.
Why nitrogen deficiency happens in bulak
Sandy, light soils, heavy rain or irrigation that washes nitrogen down, and a late or skipped sidedress. Applying urea at noon or on dry soil also loses nitrogen to the air.
How to tell it apart
Sulfur shortage also gives pale plants, but it starts on the young top leaves while old leaves stay green. Magnesium shortage reddens old leaves too, but the veins stay green. To be sure, do a soil test before planting. In season, a leaf test of the most recently matured leaf, about four or five nodes below the top, tells the plant's status, as Bayer notes.
What to apply for nitrogen deficiency
Sidedress Urea 46 0 0 3 to 5 cm from the plant base, hill up and irrigate. Side dress cotton at 42 to 47 days after planting, or splits it at 35 to 42 and 55 to 60 days on sandy soil. For cotton after garlic it gives 3 to 4 bags of urea per hectare. For a quick boost, give a urea leaf spray of 10 grams per liter (160 grams in a 16 liter sprayer) every 15 days. Give 1 percent urea (10 grams per liter, 160 grams in a 16 liter sprayer) or 2 percent DAP.
- Urea 46 0 0
- Complete 14 14 14
- 16 20 0
- Ammonium sulfate 21 0 0
Sold here with nitrogen: Atlas Granular Urea (46 0 0) by Atlas Fertilizer, Amigo Planters Ammonium Chloride by La Filipina (25 0 0), Agripower 46 0 0 (Locally Blended) Coated by Green Acres Agri Tech and Calcipro by Ramgo (15.5 0 0 with 18.8 percent calcium). Check the FPA registration on the bag and follow the label rate. For the how and when, see our guide to urea fertilizer, and the page on nitrogen deficiency in every crop. In anee.io, Anee, the smart farm technician, reads a photo of the leaf and tells you which nutrient is short.
To keep it away, band a basal fertilizer at planting and sidedress on time. For the basal, give 4 bags of Complete 14 14 14 on light soils or 3 bags of 16 20 0 on heavy soils. Do not give too much nitrogen late, because that also hurts the crop.
Potassium deficiency in cotton
Yellowish white mottling starts at the tips and edges and between the veins, then turns into brown dead spots. The edges and tips curl down and break, and the whole leaf turns reddish brown, dry and brittle. Leaves drop early, the crop cuts out early, and bolls stay small, may not open, and give weak lint. Before bloom it shows on the old leaves. Late in the season it can show on the young upper leaves, as the bolls pull potash from them. You see it most at this stage: from first bloom to boll filling. The plant takes up about 70 percent of its potash after first bloom.
Why potassium deficiency happens in bulak
Sandy soils that hold little potash, dry soil (potash moves to roots through soil water), acid soil, hardpans or nematodes that limit roots, and soils high in magnesium. High yielding, early varieties are more prone.
How to tell it apart
Leafhopper damage also yellows and reddens leaf edges and makes them curl down. But you will find the small green insects under the leaves. To be sure, at early bloom, send petioles for testing, taken from the 4th or 5th fully grown leaf below the top. Test the soil before planting.
What to apply for potassium deficiency
Apply Muriate of potash 0 0 60 as the soil test says, in two parts on sandy soils: one third at planting and the other two thirds between squaring and early bloom. For quick help, give two leaf sprays of 5.6 to 11 kg of potash per hectare during peak bloom, with potassium nitrate as the usual spray. Spray Sulfate of potash at 10 grams per liter (160 grams in a 16 liter sprayer), or 1 percent potassium chloride.
- Muriate of potash 0 0 60
- Sulfate of potash 0 0 50
- Complete 14 14 14
- Dolomite
Sold here with potassium: Atlas Muriate of Potash (MOP) by Atlas Fertilizer (0 0 60), Simplot Sulfate 0 0 50 by Nutranta, Potassium Nitrate by Parafield (13 0 46) and Qrop Mix Production 14 0 23 plus 13 Cao by Farmtech Agriland (14 0 23 with 9.3 percent calcium). Check the FPA registration on the bag and follow the label rate. For the how and when, see our guide to potash fertilizer, and the page on potassium deficiency in every crop.
To keep it away, keep soil pH above 6 with lime or Dolomite, give potash in splits. Keep the soil moist through boll filling. Keep organic matter up with compost, manure or crop residues.
Boron deficiency in cotton
Leaf stalks get short, with dark green rings or bands. Young leaves turn thick and brittle, with water soaked spots, and new growth can be misshapen. Many squares and young bolls drop, and the bolls that stay are small, flat sided and dark at the base, and mature late. In bad cases the growing tip dies and many short side branches form. You see it most at this stage: squaring to boll development, when cotton needs the most boron.
Why boron deficiency happens in bulak
Sandy soils and heavy rain that leach boron, soils above pH 7.5 or over limed soils. Drought, because dry soil cuts how much boron the roots take up.
How to tell it apart
Heat, drought and plant bugs also make squares and young bolls drop, and bollworms leave holes in bolls. The dark rings on the leaf stalks point to boron. To be sure, do a soil test. A leaf or petiole test before or at early bloom shows whether the crop needs more boron. In a soil test, less than 0.5 ppm of boron is low.
What to apply for boron deficiency
Plan on about 0.56 kg of boron per hectare. It works best as two leaf sprays of 0.28 kg each, between first square and first bloom. Give about 10 kg of Borax per hectare to the soil. Or spray Borax at 1 gram per liter (16 grams in a 16 liter sprayer). Give a 0.2 percent Borax spray (32 grams in a 16 liter sprayer). Use Solubor for sprays since it dissolves easily, and never overdo the rate.
- Borax
- Solubor
Sold here with boron: Etifert 11 (Borax Decahydrate) by Zetryl Chem (11 percent boron), Fertibagra 15G by Unilox Far East Resources (14.6 percent boron), B17 (Boric Acid) by Newman Chemicals (17 percent boron) and Better Yield by Bacphil Planters Fertilizer (0 0 0.9 with 10 percent boron). Check the FPA registration on the bag and follow the label rate. For the how and when, see our guide to foliar fertilizer, and the page on boron deficiency in every crop.
To keep it away, plan boron every season on sandy or limed soils. Do not mix borax with calcium or ammonium fertilizer in one dose. Test the soil every two or three years.
Magnesium deficiency in cotton
The lower, older leaves turn purple red between the veins while the veins stay green. In bad cases whitish to brown spots form and the edges die. Affected leaves age early and fall, and plants may look stunted. Look for cupping and yellowing between the veins starting on young leaves. But it usually shows on the old leaves first. You see it most at this stage: from flowering on, when the bolls take up magnesium.
Why magnesium deficiency happens in bulak
Acid soils, sandy soils that have lost magnesium to rain, and heavy potash use, which competes with magnesium.
How to tell it apart
Potash shortage starts at the tips and edges with yellow white mottling and brown spots. Nitrogen shortage reddens the whole leaf, veins included. To be sure, do a soil test for magnesium, potash and pH, and a leaf test.
What to apply for magnesium deficiency
Give Magnesium sulfate at about 80 kg per hectare in bands near the plants. Give a 1 percent Magnesium sulfate leaf spray (10 grams per liter, 160 grams in a 16 liter sprayer). Do not apply magnesium and potash fertilizer together. Put the soil dose in before planting or when the rains begin. Sprays show results in 10 to 14 days.
- Magnesium sulfate (Epsom salt)
- Dolomite
- Kieserite
Sold here with magnesium: Dolomite by A6 Agrisource (24 percent calcium and 11 percent magnesium), Agsmart Kieserite Granule (20 percent sulfur and 16.3 percent magnesium), DDDD Planter's Choice Magnesium Sulphate Monohydrate by Modern Time (15.1 percent magnesium) and Zetryl MAG 9 by Zetryl Chem (9 percent magnesium). Check the FPA registration on the bag and follow the label rate. For the how and when, see our guide to complete fertilizer, and the page on magnesium deficiency in every crop.
To keep it away, use Dolomite on acid soils. Long use of dolomite keeps magnesium shortage away. Test the soil every two or three years.
Phosphorus deficiency in cotton
Plants stay short and dark green, with small leaves, weak stems and few side branches. Older leaves can turn reddish purple. Roots grow poorly, flowering and boll set come late, and boll numbers drop. You see it most at this stage: seedling to early squaring.
Why phosphorus deficiency happens in bulak
Acid soils, which tie up phosphorus, as Bayer notes. Cotton takes it up best between pH 6.5 and 7.5. Poor soils with no basal fertilizer bring it on.
How to tell it apart
Nitrogen shortage also stunts the plant, but leaves are pale, not dark green. Cold or waterlogged soil also slows early growth and can redden seedlings, and it clears as soil warms or drains. To be sure, do a soil test for phosphorus and pH before planting.
What to apply for phosphorus deficiency
For quick correction, use Superphosphate 0 20 0. For the long term, bone meal or rock phosphate. Give a 2 percent DAP leaf spray (20 grams of Ammonium phosphate 18 46 0 per liter). Put 2 to 4 bags of Complete 14 14 14 per hectare in the furrow at planting.
- 16 20 0
- Complete 14 14 14
- Ammonium phosphate 18 46 0
- Superphosphate 0 20 0
Sold here with phosphorus: Philphos 18 46 0 (Di Ammonium Phosphate), Atlas Super Gro (16 20 0) by Atlas Fertilizer, Amigo Planters Granular Single Super Phosphate by La Filipina (0 18 0 with 11 percent sulfur) and Triple Super Phosphate by Newman Chemicals (0 46 0). Check the FPA registration on the bag and follow the label rate. For the how and when, see our guide to 16 20 0 fertilizer, and the page on phosphorus deficiency in every crop.
To keep it away, band a phosphate basal at planting. Use 16 20 0 on heavy soils and Complete 14 14 14 on light soils. Lime acid soils.
Sulfur deficiency in cotton
Young leaves at the top turn pale green to yellow while older leaves stay green. Veins stay green for a while, but in bad cases they pale too. Plants are small and spindly with thin stalks, few side branches and small bolls. You see it most at this stage: early to mid season, after heavy rain or waterlogging.
Why sulfur deficiency happens in bulak
Sandy, well drained soils low in organic matter and waterlogged soils, as Bayer notes. Using only urea and phosphate fertilizers that carry no sulfur adds to it, and burning crop waste loses sulfur.
How to tell it apart
Nitrogen shortage gives the same pale color, but it starts on the old, lower leaves. Iron shortage also yellows young leaves, but with green veins standing out sharply. To be sure, A leaf test of young leaves for sulfur and nitrogen together. A soil test helps. In a soil test, less than 10 ppm of sulfate sulfur is low.
What to apply for sulfur deficiency
Use a sulfur fertilizer such as Ammonium sulfate 21 0 0 or Superphosphate. On soils badly short of sulfur, give sulfur dust at about 25 kg per hectare. Give a 1 percent Magnesium sulfate leaf spray (160 grams in a 16 liter sprayer) as a quick fix. Give it at planting or with the first side dress.
- Ammonium sulfate 21 0 0
- Superphosphate 0 20 0
- Gypsum
- Magnesium sulfate (Epsom salt)
Sold here with sulfur: Atlas Ammosul 21 0 0 by Atlas Fertilizer (21 0 0 with 24 percent sulfur), Philphos Gypsum (22.2 percent calcium and 17.4 percent sulfur), Harvester Sulphate of Potash by Universal Harvester (0 0 50 with 17.5 percent sulfur) and Agsmart Kieserite Granule (20 percent sulfur and 16.3 percent magnesium). Check the FPA registration on the bag and follow the label rate. For the how and when, see our guide to ammonium sulfate fertilizer, and the page on sulfur deficiency in every crop.
To keep it away, use Ammonium sulfate 21 0 0 for part of the nitrogen, return crop waste instead of burning it, and add organic matter. Test the soil every two or three years.
Zinc deficiency in cotton
New leaves yellow between the veins, starting from the edge, and turn thick, brittle, leathery and cupped upward. Leaves stay small and may look bronzed, and the space between nodes shortens so plants look bushy. Red coloring on old and young leaves and brown spots. Squares and flowers may drop. You see it most at this stage: seedling to early squaring.
Why zinc deficiency happens in bulak
Soils outside pH 5 to 7.5, and heavy phosphate use, which ties up zinc.
How to tell it apart
Manganese shortage also yellows young leaves between the veins, but zinc short leaves are more misshapen, with long narrow tips. Leafhopper or mite damage also cups and bronzes leaves, so check under the leaves for insects. To be sure, do a soil test with pH, and a leaf test. Spray zinc on a few rows and compare the new leaves. In a soil test, less than 0.8 ppm of zinc is low.
What to apply for zinc deficiency
Give Zinc sulfate at 5 kg per hectare to the soil, or a 1 percent Zinc sulfate leaf spray (10 grams per liter, 160 grams in a 16 liter sprayer). Give a milder morning spray of Zinc sulfate at 2 grams per liter (32 grams in a 16 liter sprayer) with 2.5 grams per liter of calcium carbonate. So start with the lower rate on young plants. Do not apply zinc and phosphate fertilizer at the same time.
- Zinc sulfate
Sold here with zinc: Harvester Zinc Sulphate Heptahydrate by Universal Harvester (22 percent zinc), Petbowe Zinc Sulphate Monohydrate (33 percent zinc), Tierramino ZN by Unilox Far East Resources (7 0 0 with 10 percent zinc) and Liquid Chelate Zinc with Sulfur by Sagrex (10 percent zinc and 5 percent sulfur). Check the FPA registration on the bag and follow the label rate. For the how and when, see our guide to fertilizer with zinc, and the page on zinc deficiency in every crop.
To keep it away, base zinc on a soil test and do not overuse phosphate fertilizer.
A soil test is the surest check for any cotton nutrient deficiency. Before you buy, ask your Municipal Agriculture Office where to send a soil sample. The DA regional soil laboratories test soil, and the result says how much of each fertilizer your bulak needs. That saves money, because extra fertilizer is money lost.
Open the Nutrient Deficiency Finder, pick bulak, say where the leaves changed first and what you see, and get the fertilizers sold here that fix it.
- Anee, the smart farm technician, reads a photo of the leaf
- The cropping calendar dates every fertilizer application of your season
Cotton nutrient deficiency questions
Why are my bulak leaves turning yellow?
What fertilizer fixes nitrogen deficiency in cotton?
What fertilizer fixes potassium deficiency in cotton?
What fertilizer fixes boron deficiency in cotton?
How do I know which nutrient my bulak lacks?
Find the missing nutrient and fix it
With Libre + Anee, read the whole guide: how to tell the deficiency from look alikes, how to be sure, what to apply, and the fertilizers sold here that supply it.
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