NC State Floriculture


Low Substrate Manganese Corrective Procedures

Brian E. Whipker, James L. Gibson, Paul V. Nelson, Todd J. Cavins, and John M. Dole

Disclaimer: Growers should read and follow all label directions. Test the corrective procedure on a small number of plants prior to applying it to the entire crop.

Possible Causes
Corrective Procedures
Not using a fertilizer containing Mn (eg. calcium nitrate + potassium nitrate).

1. Use a fertilizer that contains Mn.
2. Corrective drench application of manganese sulfate at 10 ppm of Mn for soilless substrates. Add 0.5 oz. (14.2 g) of manganese sulfate (28% Mn) per 100 gallons of water. Rinse off foliage. Test on a few plants first. Do not over apply.
3. To apply a foliar spray of Mn: mix 2 oz. (56.7 g) of manganese sulfate per 100 gallons of water. It will give a final concentration of 40 ppm Mn. Test on a few plants first. Do not over apply.

Foliar sprays have a greater risk of plant injury. Avoid applications during the midday heat. Plant uptake is enhanced by prolonged drying time, which occurs during humid conditions, especially in the morning. Nutrient uptake through the leaves is also greater in the day than at night, making morning applications more desirable than evening sprays.

Little or no Mn provided through the irrigation water. 1. Use a fertilizer that contains Mn.
Don't forget to check out the Plant Root Zone Management (PRZM) Manual for more information! Want to know more? Click here!

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