Home Micro-farms Forest farms Technical Support Contact Us

4.2.7 Molybdenum

First seen: Younger leaves
Signs:Leaves show streaking of yellow.
Natural Sources: Grass Clippings, sawdust, wood shavings.

Molybdenum deficiency shows up as spotting on young leaves


Description: Molybdenum (mo lib den um) is a metallic element that is used to strengthen and harden steel. It is used as a trace mineral necessary for plants.

Deficiency: Molybdenum deficiency is rare in plants because such a small amount is needed. Deficiency first shows up in young leaves and shows up as dying area around the leaf edges.

Toxicity: Molybdenum toxicity is first seen as a copper deficiency in the plant leaf tissues.

Conditions: Molybdenum deficiency shows up first in acid soil, water and media conditions. It can show up in plants grown in a peat moss media.

Molybdenum requirements of plants

Molybdenum is needed in trace amounts. It acts as an electron carrier in converting nitrate (NO3-) or ammonium(NH4+). This means it is important in allowing plants to use the nitrogen in the nutrient.

Legumes, such as peas, beans and peanuts, need molybdenum for the bacteria that form nitrogen fixing root nodules (Sprague, 1964).

Molybdenum deficiency in plants

A deficiency is usually seen in acid soil or acid media conditions. It often looks like nitrogen starvation as molybdenum deficiency reduces the plants' ability to utilize nitrogen. Edges of leaves curl up and die with a brown color and there is some brown discoloration of the leaf edges. Yellow and orange spots start to appear on the outside margin of the leaves. It first effects the older lower leaves.

Whiptail - a condition caused by molybdenum deficiency where the plant leaf does not fill out, and the leaf midrib grows long and twisted like a whip. It is often seen first on the shaded portion of the plant.

Saline conditions - In saline conditions the first sign in leaves is a yellowing of leaves.

Remedy to molybdenum deficiency

A foliar spray is made of 1 ounce of sodium or ammonium molybdenate in 100 gallons of water. Phosphate fertilizers usually have enough molybdenum as an impurity to act as a molybdenum supplement for soil or nutrient water.

Molybdenum needs in humans

Molybdenum is stored in the body in amounts as little as .1 ppm of body tissue (Guthrie, 1971). It is used in an enzyme, xanthine oxidase that aids in mobilization of iron from liver, and gathers excess nitrogen in the body turning it into uric acid. It is also a part of aldehyde oxidase, which oxidises fat (Kirschmann, J.D., 1975).

Human daily requirements for molybdenum

Adults need 0.15 to .5 mg. Only 20 to 30% of ingested molybdenum is absorbed (12). Grains, legumes and dark green leafy vegetables are rich sources. Amounts differ due to amount available in soil. Food completely dependent upon soil content (Kirschmann, J.D., 1975) and it should be included in nutrient water of hydroponic culture.

Molybdenum deficiency

Since so little molybdenum is needed by the human body, a deficiency is rare. When it is induced in research, it looks like anemia, or iron deficiency.

Molybdenum toxicity

Too much molybdenum can trigger a copper deficiency (6). Toxicity is characterized by diarrhea, anemia, depressed growth (Kirschmann, J.D., 1975). Scouring in cattle (diarrhea) is caused by high amounts of molybdenum and can be corrected by giving more calcium.

Recommendation: In a hydroponic nutrient, molybdenum should be added at a rate of 1 microgram per liter of solution. This allows for enough molybdenum to grow a large crop and still includes enough molybdenum for human nutriention.

Copyright © 2022 Forest Farms International