Cowpea Nutrient Deficiency: Signs, Causes and the Fertilizer That Fixes It
Cowpea nutrient deficiency is one of the first things to check when the leaves of your paayap (cowpea) turn yellow, purple or burnt at the edges. On Philippine farms the usual ones are nitrogen, phosphorus, potassium, magnesium, manganese, iron 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, potassium and magnesium move inside the plant, so a shortage shows on the old, lower leaves first. But manganese, iron 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 cowpea nutrient deficiency you have, and a soil test confirms it. Each one below has its signs, its causes and its fix.
Cowpea 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 | Pale yellow green plants with weak growth and few working nodules on the roots. | Rhizobium inoculant for cowpea, Urea 46 0 0 |
| Phosphorus | old, lower leaves, the roots | Small, dark green plants that grow slowly and set few pods. | 16 20 0, Complete 14 14 14 |
| Potassium | old, lower leaves, leaf edges and tips | Older leaflets yellow at the tips and margins, go brown, then fall. | Muriate of potash 0 0 60, Complete 14 14 14 |
| Magnesium | old, lower leaves, between the veins | Older leaves 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 |
|---|---|---|---|
| Manganese | young leaves and the tip, between the veins | Young leaves pale between green veins, later with brown spots, often on limed sandy soil. | Manganese sulfate |
| Iron | young leaves and the tip, between the veins | Young leaves turn yellow, veins and all, then nearly white, on limey soil. | Ferrous sulfate |
| Boron | young leaves and the tip | New leaves come out small and crinkled. | Borax |
Before you buy fertilizer for a cowpea nutrient deficiency
So use the table to pick the likeliest cowpea 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 cowpea
Lower leaves turn pale and yellow first and the whole plant stays light green, thin and slow. Cowpea feeds itself through root nodules, so this nearly always means the nodules are few or not working. You see it most at this stage: three to six weeks after planting.
Why nitrogen deficiency happens in paayap
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
Sulfur deficiency starts on the young leaves. Iron and manganese deficiency yellow between the veins of young leaves. 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
Feed the standing crop, since nodules cannot be added now: sidedress a little Urea 46 0 0 beside the rows, following the soil test. When the roots carry few nodules, the crop needs nitrogen fertilizer. If the nodules failed, 10 to 20 kg of nitrogen per hectare is enough: about half a bag of Urea 46 0 0 beside the rows, before flowering.
- Rhizobium inoculant for cowpea
- 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, use a cowpea Rhizobium inoculant on the seed at planting, keep it shaded, and give only a small nitrogen starter. Keep organic matter up with compost, manure or crop residues.
Phosphorus deficiency in cowpea
Plants are small and stunted with dark, sometimes bluish green leaves and often no clear leaf marks. Roots and nodules are few and pods are few. You see it most at this stage: seedling to flowering.
Why phosphorus deficiency happens in paayap
Acid upland soils and soils low in phosphorus.
How to tell it apart
Nitrogen deficiency makes plants pale, not dark. To be sure, soil test for phosphorus, or compare with a strip given phosphorus.
What to apply for phosphorus deficiency
Apply 16 20 0 or Complete 14 14 14 in the furrow at planting, following the soil test. For a standing crop give a 2 percent DAP 18 46 0 spray (20 g per liter, 320 g in a 16 liter sprayer) every 15 days for pulses. A usual basal dose is 2 to 3 bags of Complete 14 14 14, or 1 to 2 bags of Diammonium phosphate 18 46 0, per hectare in the furrow at planting.
- 16 20 0
- Complete 14 14 14
- Diammonium phosphate 18 46 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, apply phosphorus at every planting and add compost.
Potassium deficiency in cowpea
The tips and edges of older leaflets turn yellow, and the yellow moves slowly toward the center and base. The leaf edges then die and brown, and the leaves fall. You see it most at this stage: flowering and pod filling.
Why potassium deficiency happens in paayap
Sandy soils and soils cropped for years without potash.
How to tell it apart
Magnesium deficiency yellows between the veins, not from the edges. To be sure, soil test for potassium.
What to apply for potassium deficiency
Give a 1 percent potassium chloride spray (10 g Muriate of potash per liter). Add Muriate of potash 0 0 60 to the soil following the soil test. 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, include potash at planting on sandy soils. Keep organic matter up with compost, manure or crop residues. Split the potash on sandy soil.
Magnesium deficiency in cowpea
The areas between the veins of older leaves turn yellow, later deep yellow, with rusty specks and dead blotches between the veins and at the edges. Late in the season the plants look like they are maturing early. You see it most at this stage: mid growth to pod filling.
Why magnesium deficiency happens in paayap
Acid, sandy soils in rainy areas and heavy potash.
How to tell it apart
Potassium deficiency starts at the leaf edges and tips. To be sure, soil test for magnesium and pH.
What to apply for magnesium deficiency
Give a 1 percent magnesium sulfate spray (10 g Epsom salt per liter) every 15 days. Use Dolomite on acid soils 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, lime acid soils with dolomite. Keep potash in balance with magnesium and calcium.
Manganese deficiency in cowpea
Leaves turn pale green to pale yellow between the veins, which stay green, starting on the new leaves. Brown spots and dead patches follow on the lower leaves as it gets worse. You see it most at this stage: early to mid growth.
Why manganese deficiency happens in paayap
High pH, over limed sandy soils and soils high in organic matter.
How to tell it apart
Iron deficiency turns the veins yellow too. 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 5 kg manganese sulfate per hectare to the soil, or two manganese sulfate sprays 10 days apart. Spray Manganese sulfate at 0.2 to 0.5 percent (32 to 80 grams in a 16 liter sprayer) two or three times, 10 to 14 days apart.
- 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 over lime. Test the soil every two or three years.
Iron deficiency in cowpea
Young leaves yellow between the veins first, then the veins yellow too, and in severe cases the leaves turn almost white. Older leaves stay green while growth slows. You see it most at this stage: seedling and early growth.
Why iron deficiency happens in paayap
High pH soils with free lime.
How to tell it apart
Manganese deficiency keeps the veins green. To be sure, soil pH test and a leaf test. In a soil test, less than 4.5 ppm of iron is low.
What to apply for iron deficiency
Give a 0.5 percent ferrous sulfate spray (5 g per liter, 80 g in a 16 liter sprayer). 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, avoid limey patches or add compost. Test the soil every two or three years.
Boron deficiency in cowpea
Leaves crinkle and stay small, mostly at the top of the plant. The newest growth is hit worst while older leaves look normal, since boron does not move within the plant. You see it most at this stage: flowering and pod set.
Why boron deficiency happens in paayap
Sandy soils low in organic matter, high pH soils and drought.
How to tell it apart
Virus diseases also crinkle leaves, with mosaic patterns and insects present. Boron shortage has no mosaic. To be sure, leaf or soil test for boron. In a soil test, less than 0.5 ppm of boron is low.
What to apply for boron deficiency
Give a 0.2 percent borax spray (2 g per liter, 32 g in a 16 liter sprayer). Do not band boron in the seed row. A usual soil dose is 5 to 10 kg of Borax per hectare (0.5 to 1 kg of boron), mixed evenly with the basal fertilizer.
- Borax
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, keep organic matter up. Test the soil every two or three years.
A soil test is the surest check for any cowpea 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 paayap needs. That saves money, because extra fertilizer is money lost.
Open the Nutrient Deficiency Finder, pick paayap, 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
Cowpea nutrient deficiency questions
Why are my paayap leaves turning yellow?
What fertilizer fixes nitrogen deficiency in cowpea?
What fertilizer fixes phosphorus deficiency in cowpea?
What fertilizer fixes potassium deficiency in cowpea?
How do I know which nutrient my paayap 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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