Cashew Nutrient Deficiency: Signs, Causes and the Fertilizer That Fixes It
Cashew nutrient deficiency is one of the first things to check when the leaves of your kasoy (cashew) turn yellow, purple or burnt at the edges. On Philippine farms the usual ones are nitrogen, phosphorus, potassium, zinc and boron. 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, phosphorus and potassium move inside the plant, so a shortage shows on the old, lower leaves first. But zinc and boron 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 cashew nutrient deficiency you have, and a soil test confirms it. Each one below has its signs, its causes and its fix.
Cashew 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 | Old leaves pale from the tip, then yellow and droopy. Small leaves, small nuts. | Urea 46 0 0, Ammonium sulfate 21 0 0 |
| Phosphorus | old, lower leaves | Leaves dark green, then dull red, green or purple. Slow tree with some dying branch tips. | Superphosphate 0 20 0, 16 20 0 |
| Potassium | old, lower leaves, leaf edges and tips | Old leaf edges turn pale yellow then brown. Purple spots under the leaf. Light nuts. | Muriate of potash 0 0 60, Sulfate of potash 0 0 50 |
Shows first on the young leaves
| Nutrient | Where it starts | What you see | Fix with |
|---|---|---|---|
| Zinc | young leaves and the tip, between the veins | Newest leaves small, long and pale with green veins, on short shoots with few side branches. | Zinc sulfate, Agricultural lime |
| Boron | young leaves and the tip, fruit, grain or tubers | Growing buds and young leaves die, flowers drop, apples split and nuts stay empty. | Borax, Solubor |
Before you buy fertilizer for a cashew nutrient deficiency
So use the table to pick the likeliest cashew 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 cashew
Older leaves turn pale green from the tip, then yellow and droop. The tree grows slowly, with smaller leaves and smaller fruits and nuts that mature early. In bad cases the young leaves pale too. You see it most at this stage: young trees in the first five years, and bearing trees that are never fertilized.
Why nitrogen deficiency happens in kasoy
Most Philippine cashew trees get no fertilizer at all, as a review of cashew production in the Philippines notes. Coastal cashew soils often hold only low to medium nitrogen.
How to tell it apart
Tea mosquito bug damage also makes trees look poor. But it leaves dark dead lesions on young shoots and flower stalks, and the shoots and flower clusters dry up. To be sure, do a soil test and a leaf test. For the leaf test, take the fifth or sixth mature leaf below the flower cluster as flowering starts. New flushes that come out greener after urea confirm it.
What to apply for nitrogen deficiency
Apply Urea 46 0 0 or Ammonium sulfate 21 0 0 in a ring under the canopy and water it in, following the soil test. Give a full yearly dose of 750 grams of nitrogen per tree from the fifth year, with one fifth of that in the first year and one fifth more each year after. For a quick lift it gives a foliar spray of Urea at 10 grams per liter (160 grams in a 16 liter sprayer) every 15 days.
- Urea 46 0 0
- Ammonium sulfate 21 0 0
- Complete 14 14 14
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, fertilize young trees every year as they grow, split the dose over the rainy season, and mulch the basin.
Phosphorus deficiency in cashew
Young mature leaves first turn darker green, then take on a dull red, green or purple tint. The tree stays small with less leaf area, leaves fall early, and some branches die back with dead leaf tips. You see it most at this stage: young trees after planting and trees on poor acid soils.
Why phosphorus deficiency happens in kasoy
Acid, weathered upland soils that lock up phosphorus and soils low in organic matter. Phosphorus is often very low in cashew soils.
How to tell it apart
Potassium deficiency also brings purple spots, but on the underside of leaves, together with yellow, browning leaf edges. Tea mosquito bug causes shoot dieback too, but with dark lesions on the shoots. To be sure, soil test for available phosphorus and pH, and a leaf test of mature leaves taken at the start of flowering.
What to apply for phosphorus deficiency
Use Superphosphate for a quick fix and rock phosphate or bone meal for the long term, applied after a soil test. From the fifth year on, the full yearly dose is 325 grams of P2O5 per tree. Phosphorus is taken up best near pH 6.5 to 7.5, so lime very acid soils.
- Superphosphate 0 20 0
- 16 20 0
- Complete 14 14 14
- Agricultural lime
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, put phosphorus in the planting hole, add organic manure each year, and lime acid soils.
Potassium deficiency in cashew
The edges of older leaves turn pale yellow, then brown and die, and the damage moves up to younger leaves. In bad cases the whole leaf browns. Purple spots can show on the underside of leaves. Trees grow poorly and give smaller, lighter nuts. You see it most at this stage: bearing trees, most of all during nut filling.
Why potassium deficiency happens in kasoy
Sandy and leached soils, acid soils, and years of harvest with no potash returned. Potash is readily available above about pH 6.
How to tell it apart
Magnesium deficiency also starts on old leaves, but it yellows between the veins rather than scorching the edge. Drought can also brown leaf edges, but over the whole tree at once. To be sure, soil test for potash and pH, and a leaf test of mature leaves at the start of flowering.
What to apply for potassium deficiency
Use Muriate of potash 0 0 60 in split doses following the soil test. Lime or dolomite to keep pH up. From the fifth year on, the full yearly dose is 750 grams of K2O per tree. For a quick fix spray Sulfate of potash at 10 grams per liter (160 grams in a 16 liter sprayer) in the morning. Give a 1 percent potassium chloride spray (160 grams in a 16 liter sprayer).
- 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, give potash every year with nitrogen, add organic matter, and keep the soil pH near 6.
Zinc deficiency in cashew
The youngest leaves come out small and long, green to pale green with the veins staying green. Sometimes show small dead spots. Internodes stay short and the tree makes few side branches. You see it most at this stage: new flushes, mostly before flowering.
Why zinc deficiency happens in kasoy
Soils naturally low in zinc, heavy phosphate, and pH outside 5 to 7.5. Zinc is often very low in cashew soils.
How to tell it apart
Manganese deficiency also bunches the leaves into a rosette. But the leaves are pale green to greenish yellow and the tree makes more side branches, not fewer. To be sure, soil test for zinc and pH, and a leaf test of mature leaves at the start of flowering. Spray a few trees and watch the next flush. In a soil test, less than 0.8 ppm of zinc is low.
What to apply for zinc deficiency
In bad cases give a morning spray of Zinc sulfate at 2 grams per liter (32 grams in a 16 liter sprayer) mixed with 2.5 grams per liter of lime (calcium carbonate). Give Zinc sulfate at 0.5 percent (5 grams per liter, 80 grams in a 16 liter sprayer). Do not apply zinc and phosphate fertilizer at the same time. Give 50 to 100 grams of Zinc sulfate a young tree and 100 to 250 grams a bearing tree a year under the canopy.
- Zinc sulfate
- Agricultural lime
Sold here with zinc: Harvester Zinc Sulphate Heptahydrate by Universal Harvester (22 percent zinc), Tierramino ZN by Unilox Far East Resources (7 0 0 with 10 percent zinc), Liquid Chelate Zinc with Sulfur by Sagrex (10 percent zinc and 5 percent sulfur) and Nemes Foliar by SCL Filipinas (4.8 0 0 with 10 percent zinc, 4.9 percent boron and 4.8 percent magnesium). 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, avoid heavy phosphate and overliming, and spray zinc before flowering where tests run low. Test the soil every two or three years.
Boron deficiency in cashew
It hits the growing points. Buds and young leaves die, and root tips stop growing, lose color and die. Flowers drop, the fruits split, and nuts stay small and poorly filled. You see it most at this stage: flushing and flowering, and during nut setting.
Why boron deficiency happens in kasoy
In other tree crops such as coffee, it is linked to soils low in boron, heavy liming, heavy potash and long droughts. The same conditions likely apply here.
How to tell it apart
Tea mosquito bug also dries flower clusters and kills young shoots, but it leaves dark lesions where it fed. Calcium deficiency also kills growing points, but the young leaves ripple, turn brittle and cup with scorched edges. To be sure, soil test for boron, and a leaf test of mature leaves at the start of flowering. In a soil test, less than 0.5 ppm of boron is low.
What to apply for boron deficiency
After a soil test, give Borax to the soil at 50 grams per tree, or a foliar spray of Borax at 1 gram per liter (16 grams in a 16 liter sprayer). Do not mix borax with calcium or ammonium fertilizers. Too much boron is toxic, so do not repeat high doses without a test. Give boron before flowering: flowers and fruit set need it most.
- 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, add organic matter, mulch the basin in the dry season. Give a small boron dose before flowering on soils that tested low.
A soil test is the surest check for any cashew 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 kasoy needs. That saves money, because extra fertilizer is money lost.
Open the Nutrient Deficiency Finder, pick kasoy, 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
Cashew nutrient deficiency questions
Why are my kasoy leaves turning yellow?
What fertilizer fixes nitrogen deficiency in cashew?
What fertilizer fixes phosphorus deficiency in cashew?
What fertilizer fixes potassium deficiency in cashew?
How do I know which nutrient my kasoy 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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