920 Samoa Blvd, Ste 217, Arcata, CA 95521
(707) 633-8885

Raising and Lowering Soil pH

Raising Soil pH:

Use a product containing calcium carbonate (CaCO3) ALWAYS lime at a different time than you apply organic amendments. They will interact with each other when you want them to act upon the soil. Pay attention to the % CaCO3 in the product you buy. Oyster shell adds calcium (Ca) and other trace minerals, but doesn’t raise the soil pH as effectively as dolomite or lime. Lime – ~100% CaCO3 – Just adds calcium (Ca) and raises pH Dolomite – CaMg(CO3)2 – Adds calcium (Ca), magnesium (Mg) and raises pH Gypsum – CaSO4*2H2O – Adds calcium (Ca) and sulfur (S) without affecting soil pH.

Lowering Soil pH:

Put a “pH down” (Like potassium hydroxide (KOH) agent in your irrigation water. Organic matter like peat and humus are naturally low in pH and will help neutralize some of the carbonates that are causing high pH. Aluminum sulfate is a fast NON-organic way of lowering pH, however we do not recommend this method.