Thursday, March 5, 2009

Greenhouse and Nursery - Problems Associated with High Alkalinity Water or Acid Water

Alkalinity or acidity levels in water used in greenhouses and nurseries can lead to media related pH problems, nutrient deficiencies, or toxicities. The following is some information on the topic from the University of Maryland.

Problems Associated With High Alkalinity in Greenhouse or Nursery Water

• Rise in the pH of the growing medium.
• Micronutrient deficiencies as these elements become insoluble.
• Possible magnesium deficiencies due to calcium imbalance.
• Possible high sodium levels.

Managing High Alkalinity

• Utilize acidic fertilizers.
– Formulations with active acidity
– Formulations with high potential acidities
• Practice constant liquid feeding.
• Consider acid injection.
• Modify the growing media to start at a lower pH.
• Monitor sodium levels.

Acid Use Calculator for Correcting High Alkalinity in Water
• This tool is available from North Carolina State University. Go to
- go to floriculture
- click floriculture software
- click alkalinity calculator

In all cases you should send your water sample to a lab that test water for greenhouse or nursery operations each year to check alkalinity levels.

Problems Associated With Acidic Waters

• Drop in the pH of the growing medium.
• Possible micronutrient toxicities as these elements become highly soluble.
• Deficiency of calcium and magnesium.

Managing Acidic Water

• Select fertilizers that are neutral or have a low potential acidity.
• Supply Ca & Mg via fertilizer or growing media additions.
• Monitor pH - make sure it is stable.
• Consider K bicarbonate injection.
• Monitor nutrient contents of media.

Reprinted from the March 14, 2008 edition of the Greenhouse TPM/IPM Weekly Report from the University of Maryland Cooperative Extension, Central Maryland Research and Education Center

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