Soybean Nutrient Deficiency: Signs, Causes and the Fertilizer That Fixes It
Soybean nutrient deficiency is one of the first things to check when the leaves of your utaw (soybean) turn yellow, purple or burnt at the edges. On Philippine farms the usual ones are nitrogen, phosphorus, potassium, sulfur, molybdenum, iron, manganese, zinc and magnesium. 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, potassium, molybdenum and magnesium move inside the plant, so a shortage shows on the old, lower leaves first. But sulfur, iron, manganese 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 soybean nutrient deficiency you have, and a soil test confirms it. Each one below has its signs, its causes and its fix.
Soybean 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 | Light green, stunted plants, often in patches or rows, with few or white nodules on the roots. | Rhizobium inoculant for soybean, Urea 46 0 0 |
| Phosphorus | old, lower leaves, the whole plant | Short, dark bluish green plants with few pods. | Complete 14 14 14, 16 20 0 |
| Potassium | old, lower leaves, leaf edges and tips | Older leaves yellow in blotches from the edges inward. | Muriate of potash 0 0 60, Complete 14 14 14 |
| Molybdenum | the whole plant | Light green plants that look nitrogen starved, on very acid soil, even with nodules present. | Sodium molybdate, Ammonium molybdate |
| Magnesium | old, lower leaves, between the veins | Older leaves turn yellow between the veins, then deep yellow with rusty specks. | Epsom salt / magnesium sulfate, Dolomite |
Shows first on the young leaves
| Nutrient | Where it starts | What you see | Fix with |
|---|---|---|---|
| Sulfur | young leaves and the tip, the whole plant | The newest leaves turn pale first, then the whole plant is evenly yellow green. | Gypsum |
| Iron | young leaves and the tip, between the veins | Youngest leaves turn yellow with green veins, then almost white, on limey soil. | Ferrous sulfate |
| Manganese | young leaves and the tip, between the veins | Leaves pale green to yellow between green veins, later with brown spots, often after liming. | Manganese sulfate |
| Zinc | the whole plant, between the veins | Leaves pale evenly between green veins, then turn rusty brown. | Zinc sulfate |
Before you buy fertilizer for a soybean nutrient deficiency
So use the table to pick the likeliest soybean 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 soybean
Plants are stunted with very pale green leaves, starting on the older leaves. This happens because the roots did not nodulate or the nodules do not work, from poor soil fertility or too little molybdenum. Yellow strips in the field often mark where the inoculant was missed. You see it most at this stage: two to six weeks after emergence.
Why nitrogen deficiency happens in utaw
In a legume this usually means poor nodulation: no inoculant in a field new to the crop, inoculant killed by sun or heat, very acid soil, waterlogging, hot dry soil, or too much nitrogen fertilizer near the seed, which stops nodules from forming.
How to tell it apart
Molybdenum deficiency looks exactly the same, because the nodules need molybdenum to work. It shows on very acid soils. To be sure, dig, do not pull, a few plants 3 to 6 weeks after planting, wash the roots and cut some nodules open. Pink to red inside means they are working, white means not active yet, and brown, grey or mushy means dead. Yellow plants with few or dead nodules point to a nodulation failure, not a lack of fertilizer.
What to apply for nitrogen deficiency
If nodules are poor and plants are yellow, give up to about 56 kg of nitrogen per hectare before full bloom. You can also give a 1 percent urea spray (10 g per liter, 160 g in a 16 liter sprayer) every 15 days.
- Rhizobium inoculant for soybean
- Urea 46 0 0
- Complete 14 14 14
Sold here with nitrogen: Atlas Granular Urea (46 0 0) by Atlas Fertilizer, Crown Champion Ammonium Sulfate by Aqua Hydroponic Prime Ventures (21 0 0 with 24 percent sulfur), 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, before planting, coat 10 kg of seed with a 100 g pack of soybean inoculant after wetting the seed with a glass of water, keep it in the shade and sow at once. Lime very acid soils. Let a soil test and the crop's color set the season's nitrogen.
Phosphorus deficiency in soybean
Plants stay small and dark bluish green, sometimes with purple or bronze tints. Growth is slow, nodules are few and pods are fewer. You see it most at this stage: early growth to flowering.
Why phosphorus deficiency happens in utaw
Acid upland soils and soils low in phosphorus, and fields cropped for years without fertilizer.
How to tell it apart
Nitrogen and molybdenum deficiency make plants pale, not dark. To be sure, soil test for phosphorus before planting.
What to apply for phosphorus deficiency
Use 2 bags of Complete 14 14 14 per hectare along the furrows before sowing when there is no soil test. Soybean also uses phosphorus left by the corn or rice before it, so feeding that crop well helps.
- Complete 14 14 14
- 16 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, fertilize the rotation, not only the soybean, and add organic matter.
Potassium deficiency in soybean
Irregular yellow mottling appears around the edges of the leaves, joins into a yellow band and then moves toward the center of the leaf, followed by dead brown tissue. It starts on the lower leaves. In severe cases all but the newest leaves show it. You see it most at this stage: early growth to pod filling.
Why potassium deficiency happens in utaw
Sandy soils, highly weathered soils and fields cropped without potash.
How to tell it apart
Manganese and iron deficiency start on young leaves. Nitrogen deficiency pales the whole leaf, not the edges. To be sure, soil test for potassium, and check that edges of the old leaves yellow first.
What to apply for potassium deficiency
Apply Muriate of potash 0 0 60 following the soil test. Give a 1 percent potassium chloride spray (10 g per liter, 160 g in a 16 liter sprayer) every 15 days. A usual dose is 1 bag of Muriate of potash 0 0 60 per hectare at planting.
- Muriate of potash 0 0 60
- 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 residues and include potash in the rotation. Split the potash on sandy soil.
Sulfur deficiency in soybean
New leaves are the first to turn pale, then the whole plant becomes evenly pale yellow. It looks like nitrogen deficiency but is not centred on the old leaves. You see it most at this stage: early growth.
Why sulfur deficiency happens in utaw
Sandy soils low in organic matter, and sulfur free fertilizer over many years. Legumes need more sulfur than grasses.
How to tell it apart
Nitrogen deficiency starts on the older leaves. Iron deficiency keeps the veins green. To be sure, soil and leaf test for sulfur. In a soil test, less than 10 ppm of sulfate sulfur is low.
What to apply for sulfur deficiency
Give a 0.5 to 1 percent calcium sulfate spray (5 to 10 g per liter, 80 to 160 g in a 16 liter sprayer). For the soil, Gypsum adds sulfur without nitrogen. About 11 kg of sulfur per hectare is enough for row crops such as soybean. Give it at planting or with the first side dress.
- Gypsum
Sold here with sulfur: Crown Champion Ammonium Sulfate by Aqua Hydroponic Prime Ventures (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 gypsum or a sulfur bearing fertilizer every few seasons. Test the soil every two or three years. Keep organic matter up with compost, manure or crop residues.
Molybdenum deficiency in soybean
Plants are light green and small, just like nitrogen deficiency, because the nodules need molybdenum to fix nitrogen. Nodules may be present but work poorly. You see it most at this stage: early growth.
Why molybdenum deficiency happens in utaw
Very acid, sandy or highly weathered soils, where iron and aluminum hold molybdenum tightly.
How to tell it apart
Nitrogen deficiency from missed inoculation looks the same. Check soil pH. To be sure, soil pH test (below about 5.5 is a warning) and a look at the nodules. A soil pH test confirms the risk. A test spray of sodium molybdate on a few plants confirms the cause when they green up.
What to apply for molybdenum deficiency
Liming to pH 6.0 or above often fixes it alone. Otherwise treat seed with about 35 g of molybdenum per hectare. Or spray 140 to 210 g of sodium or ammonium molybdate per hectare on the growing crop. Spray Sodium molybdate at 0.05 to 0.1 percent (8 to 16 grams in a 16 liter sprayer) once or twice on young plants.
- Sodium molybdate
- Ammonium molybdate
- Agricultural lime
Sold here with molybdenum: Tierramino Molybdenum by Unilox Far East Resources (16 percent molybdenum) and YaraVita Teprosyn Mo (0 15 0 with 15.3 percent molybdenum). 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 molybdenum deficiency in every crop.
To keep it away, lime acid fields before planting and use a molybdenum seed treatment where the pH is low. Test the soil every two or three years.
Iron deficiency in soybean
Young upper leaves turn yellow between the veins first, then the veins yellow too. In severe cases the leaves become almost white. Older leaves stay green, and the patches follow spots of limey soil. You see it most at this stage: seedling and early growth.
Why iron deficiency happens in utaw
High pH soils with plenty of free lime.
How to tell it apart
Manganese deficiency also yellows between the veins, but the veins stay green and brown spots form. Nitrogen deficiency starts on the old leaves. To be sure, soil pH test and a young leaf test. In a soil test, less than 4.5 ppm of iron is low.
What to apply for iron deficiency
Give a 1 percent ferrous sulfate spray (10 g per liter, 160 g in a 16 liter sprayer) every 15 days, or 5 to 10 kg ferrous sulfate per hectare to the soil.
- 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, avoid planting soybean on limey patches or choose tolerant varieties. Test the soil every two or three years. Keep organic matter up with compost, manure or crop residues.
Manganese deficiency in soybean
Leaves turn pale green to pale yellow between the veins while the veins stay green. As it gets worse, brown spots and dead patches form. New leaves can grow out normal later in the season. You see it most at this stage: early to mid growth.
Why manganese deficiency happens in utaw
High pH, sandy soils, over limed fields and soils high in organic matter. Soybean and beans need much manganese.
How to tell it apart
Iron deficiency turns the veins yellow too. Magnesium deficiency starts on the old leaves. To be sure, leaf test for manganese and a soil pH test. In a soil test, less than 1 ppm of manganese is low.
What to apply for manganese deficiency
Give a 0.5 percent manganese sulfate spray (5 g per liter, 80 g in a 16 liter sprayer) every 15 days, or 20 to 25 kg manganese sulfate per hectare to the soil. Give about 5.6 kg of manganese per hectare to the soil, or 1.1 kg per hectare as a spray. Do not put chelated manganese in the soil, since it can make the shortage worse.
- Manganese sulfate
Sold here with manganese: Manganese Sulfate by Zetryl Chem (31 percent manganese), Tierramino MN by Unilox Far East Resources (7 0 0 with 12 percent manganese), Multimate by Agway (4 0 0 with 4.5 percent sulfur, 2.8 percent zinc and 1.8 percent manganese) and Nutri Tabble Meta Foliar by NS Northern Organic Fertilizer (12 percent zinc, 9 percent sulfur, 2 percent magnesium and 1.2 percent manganese). 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 manganese deficiency in every crop.
To keep it away, do not lime above about pH 6.5 on sandy soils. Test the soil every two or three years.
Zinc deficiency in soybean
Leaves become pale between the veins, which stay green, and then turn rusty brown. The pale color is even over the leaf, not starting at the edges as with potassium. It is not common. You see it most at this stage: early growth.
Why zinc deficiency happens in utaw
High pH soils, heavy phosphorus and sandy soils low in organic matter.
How to tell it apart
Potassium deficiency starts at the leaf edges. Manganese deficiency is hard to tell apart without a leaf test. To be sure, leaf test for zinc. In a soil test, less than 0.8 ppm of zinc is low.
What to apply for zinc deficiency
Give a 1 percent zinc sulfate spray (10 g per liter, 160 g in a 16 liter sprayer) every 15 days, or 20 to 25 kg zinc sulfate per hectare to the soil.
- 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, add zinc to the basal fertilizer on high pH soils. Test the soil every two or three years. Do not overdo phosphorus.
Magnesium deficiency in soybean
The spaces between the veins of older leaves turn yellow, then deep yellow, with rusty specks and dead blotches between the veins and at the edges. Late in the season the crop looks like it is maturing early. You see it most at this stage: mid season to pod filling.
Why magnesium deficiency happens in utaw
Acid, sandy soils in rainy areas and heavy potash on soils low in magnesium.
How to tell it apart
Potassium deficiency begins at the leaf edges. Manganese deficiency starts on the young leaves. To be sure, soil test for magnesium and pH.
What to apply for magnesium deficiency
Give a 2 percent magnesium sulfate spray (20 g Epsom salt per liter) every 15 days. Lime acid soils with Dolomite as the soil test advises. A usual dose is 100 to 150 kg of Kieserite or 150 to 200 kg of Magnesium sulfate per hectare at planting. On acid soil, 1 to 2 tons of Dolomite mixed in before planting both limes and feeds.
- 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, use dolomite rather than plain lime on acid soils low in magnesium. Keep potash in balance with magnesium and calcium.
A soil test is the surest check for any soybean 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 utaw needs. That saves money, because extra fertilizer is money lost.
Open the Nutrient Deficiency Finder, pick utaw, 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
Soybean nutrient deficiency questions
Why are my utaw leaves turning yellow?
What fertilizer fixes nitrogen deficiency in soybean?
What fertilizer fixes phosphorus deficiency in soybean?
What fertilizer fixes potassium deficiency in soybean?
How do I know which nutrient my utaw 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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