Manganese in Plants
Effect of manganese on yield in rye; control on left, treated crop on right

Manganese is an important micronutrient. For starters, it helps to activate key enzyme systems in plants. In addition, it has many varied roles:

  • Producing chlorophyll.
  • Helping to metabolize nitrogen and carbohydrates.
  • Producing lignin, the substance that lends strength to plant stems.
  • Promoting pollen germination.

This mineral is particularly important to root crops such as onions because it promotes healthy root growth and wards off a number of root diseases.

Manganese also increases the nutritional value of food for the end consumer, as it enables the plant to synthesize a number of vitamins.

Natural Sources

Manganese is among the most abundant minerals in the earth’s crust. It can be found in many types of rocks, not to mention air and water.

Manganese chelate is considered a suitable fertilizer for organic use.


Manganese in Plants
Particularly vigorous stand of rye fertilized with manganese

Even though manganese is common, it can become unavailable due to adverse conditions. Factors that can reduce manganese availability and uptake in plants include:

  • Poor soil drainage.
  • Soil pH over 7.5.
  • Excessively high organic matter levels.
  • Insufficient nitrogen.
  • Excess iron.

Root crops, particularly onions, have considerable manganese needs. Other plants susceptible to manganese deficiency include peas, green beans, raspberries, apples, and cherries.

Symptoms of manganese deficiency in plants include:

  • Uneven emergence.
  • Small, irregularly shaped leaves.
  • Checkered, striped, or uniform yellowing of young leaves.
  • Death of discolored leaf parts.
  • Yield reduction.

Never apply a manganese fertilizer without first testing the soil to make sure it is truly necessary. Instead, stop applying organic matter for the time being and correct the pH to a range between 5.0 and 7.0. Then apply nitrogen. If iron toxicity is involved, address this problem, as well.


Manganese toxicity can be caused by a pH below 5.5, or it can be a result of the overuse of fertilizers containing manganese. Marigolds and zonal geraniums are particularly susceptible to the effects of excess manganese.

Toxicity symptoms (which mostly appear on older leaves) include:

  • Leaf cupping.
  • Darkened leaf veins.
  • Reddish-brown spots on leaf surfaces.
  • Burned leaf tips and margins.

If your plants are suffering from manganese toxicity, stop using all fertilizers that contain the mineral. Raise the pH closer to a neutral level, and flush the excess manganese from the soil with plenty of water.

Complete Series

Minerals in Plants

Minerals in Plants