Soil pH Basics

A pH value indicates how acidic or alkaline something is on a scale from 1 to 14. Pure rainwater or distilled water is neutral with a pH of 7.0. Acids have pH less than 7 (lemon juice and vinegar are around pH 2). A pH above 7.0 is more alkaline (baking soda is around pH 8, ammonia is about pH 11).

Most vegetables like a neutral or slightly acidic soil (pH 6.0-7.5). In areas with wet, rainy climates like the Pacific Northwest, soils tend to be acidic. Soils with lots of leaf matter also tend to be acidic, as do clay soils. So the soil in your Seattle garden is more likely to be slightly acidic than alkaline - but don’t worry, it might not be too acidic.

Simple Soil pH Tests

Here are a few basic pH tests. These test are not exact by any means, but should give you a general idea of whether your soil pH is too far from neutral. If either test indicates your soil is too far from basic, you should get a more accurate test from an expert, or try the mild corrective actions mentioned.

To test if your soil pH is too low (acidic, also called sour): Add a pinch of baking soda to a tablespoon of wet soil from your garden. If you don’t hear a lot of fizzing, then your soil is not too acidic (try testing for alkalinity). To correct acid soil, add a few scoops of lime, dolomite lime, or even wood ashes to your plot and dig it into the top few inches of soil.

To test if your soil pH is too high (alkaline, also called basic or sweet): Add a tablespoon of white vinegar to a tablespoon of dry soil from your garden. If you hear fizzing, then your soil is probably too alkaline (try testing for acidity). If you don’t hear a lot of fizzing, then your soil is not too basic. To correct slightly alkaline soil, dig peat moss into your planting beds.

Copyright © 2003 Brian Ballard. All rights reserved.