Manganese

Manganese is involved in photosynthesis and chlorophyll production. It helps activate enzymes involved in the distribution of growth regulators within the plant.

Manganese deficiency causes yellowing between veins of young leaves. Leaves gradually turn pale green with darker green next to the veins.

Manganese toxicity can occur on soils with a low pH. It causes brown spots or yellow mottled areas near leaf tips and along the leaf margins. It usually develops on older leaves. Brown spots may also develop on veins, petioles, and stems.

Manganese availability is greatest at a soil pH of 5.0 to 6.5. Soil-applied manganese may be useful in acidic (low pH) sandy soils; however, on high pH and muck soils, foliar applications are often more effective than soil applications. It is important not to add more lime than is needed to correct soil acidity. High organic matter levels decrease manganese availability

If a manganese deficiency is confirmed, apply foliar sprays when the plants are about ⅓ grown or sooner. Two or more sprays may be necessary at 10-day intervals.

The OMAFRA-accredited manganese soil test uses a “Manganese Availability Index”. This index evaluates manganese availability based on soil manganese level and soil pH.