Molybdenum (Mo) in crops: role, deficiency signs and how to correct it

Molybdenum is a micronutrient the crop needs in very small amounts to turn nitrate into protein and, in legumes, for the nodule bacteria to fix nitrogen from the air. A molybdenum-short crop looks nitrogen-starved: pale older leaves, scorched or cupped leaf edges, weak nodules in pulses and the narrow 'whiptail' leaves of cauliflower. Unlike most micronutrients, it is least available in acid soils.

By Gafar Laiya and the Gujarat Bio Organics team. Updated November 2026.

What molybdenum does in the plant

• Part of the enzyme that turns nitrate taken from the soil into forms the plant can build protein from.
• Part of the enzyme nodule bacteria use to fix nitrogen in legumes.
• Helps the plant use phosphorus and iron.
• Needed for pollen and seed development in some crops.

How molybdenum moves in the plant

Molybdenum moves fairly well inside the plant, so the shortage often shows on older and middle leaves first, looking like nitrogen shortage.

Signs of molybdenum deficiency

• Pale yellow-green older leaves, like nitrogen shortage, that do not improve with urea.
• Leaf edges scorched, rolled or cupped upward.
• Few, small, pale nodules in legumes.
• In cauliflower and cabbage, narrow strap-like leaves (whiptail) and poor heads.
• Poor flowering and seed set in legumes.

Crop by crop

More crops and look-alikes: Molybdenum deficiency symptoms crop by crop.

Where and why it happens

• Acid soils, where molybdenum is held tightly; this is the opposite of zinc, iron and manganese.
• Heavily weathered, leached soils.
• Soils high in iron and aluminium oxides.
• Heavy sulphate fertilizer use, which can compete with molybdenum uptake.

How it works with other nutrients

• Raising the pH of acid soils with lime usually releases molybdenum.
• Sulphate competes with molybdenum for uptake.
• Phosphorus can improve molybdenum uptake.
• Molybdenum shortage makes nitrogen shortage worse, because nitrate is not used.
• See nutrient interactions.

What happens if it is not managed

• Legumes fix less nitrogen, so they need more fertilizer and leave less for the next crop.
• Nitrate builds up in leaves instead of becoming protein.
• Poor flowering, pod and seed set.
• Low yields that urea does not fix.
• See the full picture of what unmanaged shortages cost.

How to confirm it

• Suspect molybdenum when a legume looks nitrogen-starved with few or pale nodules, or when urea does not help.
• Dig up plants and check nodules: healthy ones are pink inside.
• Check soil pH: acid soils are at risk.
• A leaf test confirms; soil tests for molybdenum are less common.

How to correct it

• Seed treatment with a molybdenum salt, often together with Rhizobium culture, is the usual and cheapest method.
• Foliar spray on the standing crop for quick correction.
• Liming acid soils improves availability.
• Only tiny amounts are needed. Take the dose from the label or your agriculture officer.

Too much molybdenum

• Plants tolerate excess molybdenum, but animals do not.
• Fodder very high in molybdenum can cause copper shortage in cattle (molybdenosis).
• Do not over-apply on fodder crops.

Doses depend on the crop, soil and product, so this page gives methods, not amounts. Take the dose from your soil test report, the product label or your local agriculture officer or KVK. Results differ from farm to farm with soil, weather, crop and management. Farmer experiences on this site are their own reports, not a promise of results.