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Fertilizing and Feeding

Will my nitrogen source affect the PH?

The source of nitrogen in your fertilizer affects the pH of the medium you are growing in. The standard of measure of how acidic/basic a source is, is calcium carbonate, a common water mineral. Calcium carbonate is the major contributor of water alkalinity, the capacity for water to 'soak up', or buffer, acidity in water and lead to a high pH.

Note that it is much easier to lower the pH of water through the acidity of a given nitrogen source than it is to raise it, as nitrates are less basic than ammonium is acidic.
 
code:


N Source Potential acidity Potential Basicity

Ammonium sulfate 2,200 0

Urea 1,680 0

Diammonium phosphate 1,400 0

Ammonium nitrate 1,220 0

Monoammonium phosphate 1,120 0

Calcium nitrate 0 400

Potassium nitrate 0 520

Sodium nitrate 0 580


Potential acidity = # of lbs of calcium carbonate needed to neutralize acidity of one ton of source.

Potential basicity = one ton of source has same effect as this many lbs of calcium carbonate.