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What is pH Anyway?

The pH (potential Hydrogen) of a soil indicates its acidity or alkalinity. It is measured on a scale of 0-14, with 7 being exactly neutral. 7.1 and higher are alkaline, 6.9 and lower is acid. Most soils are neutral to slightly acid, which is also the ideal range for most plants. The importance of pH is that it affects plants’ intake of nutrients from the soil.

Different plants are adapted to different soil pH ranges. Our heavy winter rains tend to make our soils more acidic, so native plants are adapted to acidic soils. So are rhodies, camellias, blueberries, and most evergreens. Grasses, roses, and a lot of our favorite perennials and vegetables, however, prefer higher alkalinity.

To raise pH one unit (say from 6 to 7-acid to neutral), the rule of thumb is to use LIME at a rate of 5 pounds per 100 square feet. To lower pH (make soil more acidic), apply agricultural sulfur, 1 pound per 100 square feet. Sandy soils will need a little less than this average, heavy clays a bit more.

Remember, plants can best utilize nutrients when the pH is in the range they like. If you apply fertilizer to a plant suffering the wrong pH, then you’re not getting your money’s worth. So remember each year to lime your lawns and other neutral-to-alkaline loving plants—winter is a good time to do it.

By Cathy Revell, W.C.N.
Skylights Spring/Summer 2001, Vol 15, No. 2

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