Acidity and Alkalinity (PH)

Most plants develop well in soils that are slightly acid to neutral (6.0 to 7.0) provided the proper nutrients are in the soil. These nutrients are available to plants in this range of pH. Generally, soils in moist climates are acid and those in dry climates are alkaline.

A soil with a pH lower than 7.0 is an acid soil and one with a pH higher is alkaline. A soil analysis will reveal the pH of the soil so that a decision can be made on whether to alter the pH or not.

Most garden plants prefer a pH in the neutral range. Some plants are more specific in their requirements. Lilacs and clematis thrive in sweet soils. Rhododendrons and blueberries like a lower pH. You can adjust the pH in different parts of your landscape.

Acid soils can be limed to bring the pH to the favorable range. Lime, ground limestone, marl, or ground oyster-shells on garden soils serves a threefold purpose: (1) To supply calcium and other plant nutrients; (2) to reduce soil acidity; (3) to improve the physical character of certain heavy soils.

As a rule, asparagus, celery, beets, spinach, and carrots are benefitted by moderate applications of lime, especially on soils that are naturally deficient in calcium. Dolomitic limestone should be used on soils deficient in magnesium. Most garden vegetables do best on soils that are slightly acid and may be injured by the application of lime in excess of their requirements.

For this reason lime should be applied only when tests show it to be necessary. Most garden centres carry inexpensive soil testing kits which include a test for PH. The test is easy to perform, and you should also test for essential nutrients as well.

In no case should the material be applied in larger quantities than the test indicates. Most garden soils that are in a high state of fertility do not require the addition of lime.

Alkaline soils may be treated with an acid producing material. Organic matter, sulfur, and some sulfur containing materials can be used. When using organic matter in the form of manure, care must be taken that the manure itself is not alkaline.

Some manures are alkaline and contain high amounts of soluble salts which are detrimental to plants, especially when applied in alkaline soils. It is recommended that you adjust your soil PH - if necessary- gradually over a couple of growing seasons. This will give you the best results.

With good drainage, plenty of organic matter in the soil, and the moderate use of commercial fertilizers, the growth requirements of nearly all vegetables may be fully met.