Taro Nutrient Deficiency: Signs, Causes and the Fertilizer That Fixes It
Taro nutrient deficiency is one of the first things to check when the leaves of your gabi (taro) turn yellow, purple or burnt at the edges. On Philippine farms the usual ones are nitrogen, potassium, phosphorus, calcium, magnesium, sulfur, iron 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, phosphorus and magnesium move inside the plant, so a shortage shows on the old, lower leaves first. But calcium, sulfur, iron 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 taro nutrient deficiency you have, and a soil test confirms it. Each one below has its signs, its causes and its fix.
Taro 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 | Older leaf blades yellow first, then all of them, with stunted plants and few suckers. | Urea 46 0 0, Complete 14 14 14 |
| Potassium | old, lower leaves, leaf edges and tips | Slow plants that wilt easily, with scorched edges or brown spots in the middle of older leaves. | Muriate of potash 0 0 60, Sulfate of potash 0 0 50 |
| Phosphorus | old, lower leaves | Stunted plants with darker green old leaves dotted with light spots. | Single superphosphate 0 20 0, Complete 14 14 14 |
| Magnesium | old, lower leaves, between the veins | Older leaves yellow between dark green veins, then the edges brown and die. | Epsom salt / magnesium sulfate, Dolomite |
Shows first on the young leaves
| Nutrient | Where it starts | What you see | Fix with |
|---|---|---|---|
| Calcium | young leaves and the tip, the roots | The youngest leaf yellows between the veins and cups, with brown edges, and roots die back. | Agricultural lime, Dolomite |
| Sulfur | young leaves and the tip, the whole plant | Younger leaves are small and evenly yellow, and roots stay short. | Ammonium sulfate 21 0 0, Gypsum |
| Iron | young leaves and the tip, between the veins | Young leaves yellow between the veins, then bleach evenly, in dry upland fields. | Ferrous sulfate |
| Zinc | the whole plant, young leaves and the tip | Plants are just stunted with small leaves. There are few other signs. | Zinc sulfate |
Before you buy fertilizer for a taro nutrient deficiency
So use the table to pick the likeliest taro 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 taro
Roots, main shoot and suckers stay stunted. Yellowing starts on the oldest leaf blades and, as it gets worse, all the blades turn yellow. Old leaves die early, so fewer leaves are working and the corm yield drops. You see it most at this stage: from 2 months after planting through corm bulking.
Why nitrogen deficiency happens in gabi
Flooded (wetland) taro loses nitrogen to the air when the soil has no oxygen. Taro does best when most of the nitrogen in the soil is nitrate.
How to tell it apart
Sulfur deficiency yellows the young leaves evenly. Magnesium deficiency yellows between the veins of old leaves. To be sure, test leaf number 2, the second fully open leaf below the newest. Below 4.0 percent nitrogen means it is short. A leaf test confirms it.
What to apply for nitrogen deficiency
Apply nitrogen following the soil test, for example Urea 46 0 0 or Complete 14 14 14 in split doses. You can also give a urea spray of 10 g per liter (160 g in a 16 liter sprayer) every 15 days. Do not overdo it, since too much nitrogen invites taro leaf blight. A usual side dress is 1 to 2 bags of Urea 46 0 0 or 2 to 4 bags of Ammonium sulfate 21 0 0 per hectare, 30 to 45 days after planting.
- Urea 46 0 0
- Complete 14 14 14
- 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, split nitrogen through the season and add compost or manure.
Potassium deficiency in taro
Growth slows, plants wilt easily and leaf blades are smaller. Older leaves get a burnt look between the veins or along the edges. In some varieties irregular brown spots form in the center of older blades and join until the whole leaf yellows or browns. Corms stay small. You see it most at this stage: corm bulking.
Why potassium deficiency happens in gabi
Sandy and leached soils, and fields where taro and other root crops have been grown for years.
How to tell it apart
Magnesium deficiency yellows between veins first, then browns the margins. Taro leaf blight gives water soaked spots that ooze, mainly in wet weather. To be sure, leaf test of leaf number 2. Soil test for potassium.
What to apply for potassium deficiency
Apply Muriate of potash 0 0 60 following the soil test, split in parts. Give a potassium sulfate spray of 10 g per liter (160 g in a 16 liter sprayer) as a quick fix. A usual dose is 2 to 3 bags of Muriate of potash 0 0 60 per hectare, half at planting and half when the roots or tubers start to swell.
- Muriate of potash 0 0 60
- Sulfate of potash 0 0 50
- Complete 14 14 14
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, return crop waste and add wood ash or compost.
Phosphorus deficiency in taro
Root and shoot growth are stunted. Older leaf blades can look darker green, and in some varieties many light colored dots form between the veins. Later the leaf edges yellow and turn brown. You see it most at this stage: early growth.
Why phosphorus deficiency happens in gabi
Acid upland soils and volcanic soils that hold phosphorus. In flooded fields phosphorus becomes more available.
How to tell it apart
Potassium deficiency gives brown spots and scorched edges, not light dots on dark leaves. To be sure, do a soil test and a leaf test. A leaf holding 0.3 to 0.5 percent phosphorus has enough.
What to apply for phosphorus deficiency
Use single superphosphate for a quick fix and rock phosphate for the long term, following the soil test. A usual basal dose is 4 to 6 bags of Complete 14 14 14 per hectare in the furrow at planting.
- Single superphosphate 0 20 0
- Complete 14 14 14
- Rock phosphate
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, apply phosphorus at planting and add organic manure.
Calcium deficiency in taro
Root and shoot growth drop and roots look stunted. The newest blade yellows between the veins first. When it is bad, blades cup and brown at the margins, never open fully, and the shoot dies. Dying roots let soil diseases in. You see it most at this stage: early growth, on acid upland soils.
Why calcium deficiency happens in gabi
Very acid soils. At pH 4, aluminum also poisons the roots. Heavy potash or ammonium fertilizer, salty soil and dry spells keep calcium from reaching fruit and young leaves.
How to tell it apart
Manganese toxicity in older leaves can look like calcium deficiency with cupped blades. Calcium deficiency starts on the youngest leaf. To be sure, test the soil pH and a leaf. Below 0.7 percent calcium in the leaf means it is short. A soil test for calcium and pH, and a leaf test, confirm it.
What to apply for calcium deficiency
On acid soils, lime about 250 kg per hectare where the pH is 5.5 to 6. About 840 kg per hectare in two splits where it is 3.5 to 4.5. Dolomite protects taro roots on soils with toxic aluminum.
- Agricultural lime
- Dolomite
- Gypsum
Sold here with calcium: Planters Products Lifelime (36.2 percent calcium), Dolomite by A6 Agrisource (24 percent calcium and 11 percent magnesium), Calcipro by Ramgo (15.5 0 0 with 18.8 percent calcium) and Philphos Gypsum (22.2 percent calcium and 17.4 percent sulfur). Check the FPA registration on the bag and follow the label rate. For the how and when, see our guide to fertilizer for tomatoes, and the page on calcium deficiency in every crop.
To keep it away, lime acid soils ahead of planting. Test the soil every two or three years. Keep potash in balance with magnesium and calcium.
Magnesium deficiency in taro
Older leaf blades yellow between the veins while the veins stay dark green. As it gets worse the margins and the spaces between veins turn brown and die, leaves may curl and drop early. You see it most at this stage: mid season.
Why magnesium deficiency happens in gabi
Sandy soils, acid soils and heavy potash.
How to tell it apart
Potassium deficiency scorches margins without the clear green vein pattern. To be sure, A leaf test below 0.2 percent magnesium means it is short.
What to apply for magnesium deficiency
Give about 80 kg magnesium sulfate per hectare in bands near the plants. Do not apply it together with potash. Use Dolomite on acid soils. Put the soil dose in before planting or when the rains begin. Sprays show results in 10 to 14 days.
- Epsom salt / magnesium sulfate
- Dolomite
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, lime acid soils with dolomite. Test the soil every two or three years.
Sulfur deficiency in taro
Roots and shoots grow less, leaf blades are smaller, and the younger leaves turn evenly yellow. The yellow is uniform across the blade, without a pattern of green veins. You see it most at this stage: early growth.
Why sulfur deficiency happens in gabi
Soils low in organic matter and burning crop waste.
How to tell it apart
Nitrogen deficiency yellows the old leaves first. To be sure, A leaf holding under 0.2 percent sulfur is short. A soil test for sulfur and a leaf test confirm it. In a soil test, less than 10 ppm of sulfate sulfur is low.
What to apply for sulfur deficiency
Use Ammonium sulfate 21 0 0 or single superphosphate. Give about 25 kg sulfur dust per hectare on sulfur poor soils, or Gypsum on alkaline soils. Give it at planting or with the first side dress.
- Ammonium sulfate 21 0 0
- Gypsum
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, add organic matter. Test the soil every two or three years.
Iron deficiency in taro
Younger leaf blades first yellow between the veins, then turn evenly bleached. Fewer side roots form. You see it most at this stage: early growth, in upland taro.
Why iron deficiency happens in gabi
Upland (not flooded) soils with high pH. Flooding makes iron more available. Too much manganese can also block iron.
How to tell it apart
Manganese toxicity on older leaves looks like iron deficiency but starts on the old blades. Manganese deficiency also starts on young leaves. To be sure, test leaf number 2. Below 100 ppm iron means it is short. A soil pH test and a leaf test of the young leaves confirm it.
What to apply for iron deficiency
Give about 15 kg ferrous sulfate per hectare to the soil, following a soil test. Spray the young leaves in the cool of the day, soon after sunrise or near sunset.
- Ferrous sulfate
Sold here with iron: DDDD Planter's Choice Ferrous Sulphate Heptahydrate by Modern Time (19 percent iron), Ferrous Sulfate Monohydrate by Zetryl Chem (30 percent iron), Ferrous Sulphate Monohydrate by Newman Chemicals (30 percent iron) and Liquid Chelate Iron with Sulfur by Sagrex (5 percent iron and 3 percent sulfur). 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 iron deficiency in every crop.
To keep it away, keep organic matter high in upland taro fields.
Zinc deficiency in taro
Taro low in zinc is stunted above and below ground, and other signs can be faint. Smaller, distorted young leaves in a rosette and slow leaf growth. You see it most at this stage: early growth.
Why zinc deficiency happens in gabi
Soils outside pH 5 to 7.5 and heavy phosphorus.
How to tell it apart
Many problems stunt taro. Only a leaf test confirms zinc. To be sure, A leaf test of 20 to 40 ppm zinc means the plant has enough.
What to apply for zinc deficiency
Give about 20 kg Zinc sulfate per hectare to the soil, or a spray of 2 g zinc sulfate with 2.5 g lime per liter in severe cases. Keep zinc and phosphate applications apart. Give the soil dose at planting or when the rains begin, and sprays on young growth.
- 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, test before adding zinc. Too much is toxic to taro. Test the soil every two or three years.
A soil test is the surest check for any taro 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 gabi needs. That saves money, because extra fertilizer is money lost.
Open the Nutrient Deficiency Finder, pick gabi, 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
Taro nutrient deficiency questions
Why are my gabi leaves turning yellow?
What fertilizer fixes nitrogen deficiency in taro?
What fertilizer fixes potassium deficiency in taro?
What fertilizer fixes phosphorus deficiency in taro?
How do I know which nutrient my gabi 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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