Correct Soil PH in Fill

To the gardener, correct pH is important for obtaining the best plant growth and efficient use of fertilizers. The pH numbering system revolves around 7, the neutral point. Any number lower than 7 indicates an acid substance, while any number higher than 7 indicates an alkaline material. The pH of pure water is 7. This indicates that the hydrogen ions (which influence acid reactions) are equal in quantity to the hydroxyl ions (which influence basic reactions).

The following numbers indicate the approximate pH of some common items: vinegar or lemons - 2.25; apples - 35; tomatoes - 4.25; cabbage - 5.3; milk - 6.6; baking soda - 8.4, and milk of magnesia- 10.5. Most foods we eat, as well as many of our body fluids, are either somewhat acid or neutral. This is also true of plant growth. Most plants we grow should have soil that is neutral or slightly acid. The best pH range for most plants is between pH 6 and pH7. There are exceptions, such as the azaleas and rhododendrons, which do best at a soil pH close to 5.

If plant growth has not been as good as desired this past season, even though you applied adequate fertilizer and water, you may need to consider and check the soil pH. There is no way to accurately guess the pH of a soil by its appearance. A soil test is the only accurate way to determine the existing acidity or alkalinity of a soil. Soil testing is relatively inexpensive and may be done through University Extension Centers as well as through some private laboratories.

Fall is a good time to get soil treated, as there is less demand, and results can usually be obtained much more quickly than in spring. Acid soils are easily reduced by the addition of lime. However, since the reaction takes place slowly, it is usually beneficial to apply lime to the lawn or garden in fall rather than in spring. This is especially true of lawns were application is made only to the surface and not tilled into the soil.

Avoid excess applications, and apply lime only in the amount recommended with the results of the soil test. Several types of lime are available which cause a pH change as well as add calcium to the soil. Ground limestone is best for general yard and garden use, although ground dolomitic limestone is even better because it also supplies magnesium. Other forms of lime include hydrated (slaked) lime and quick lime (oxide of lime). These latter two also supply calcium and change pH, but they are much faster acting, which greatly increases the chances for plant damage.

Therefore, in most cases, ground limestone should be preferred. After the proper pH has been established in a garden, the soil slowly becomes more acid. Therefore, many gardeners add about 5 pounds of ground limestone per 100 feet of garden every 4 or 5 years as a maintenance procedure. To avoid an excess, or application when unnecessary, check soil conditions by having it tested periodically.

http://en.wikipedia.org/wiki/PH