Soil Analysis

3. Soil Analysis

Many advocates of organic gardening will tell you that the first step is to have your soil analyzed to determine what elements are missing, and to determine its pH—that is, the degree of its acidity (sourness) or alkalinity (sweetness), because the pH has a relationship to the ability of the soil to support the growth of various plants. (pH is a chemical symbol denoting the concentration of hydrogen ions per liter.) You might decide to bypass this step.

On a scale of 0 to 14, pH values from 0 to 7 indicate acidity; values from 7 to 14 indicate alkalinity; pH 7, the value of pure water, is regarded as neutral. Soil in most low rainfall areas tend to be alkaline; soil in high rainfall areas are usually somewhat acid.

The continual addition of organic material to the soil generally provides the necessary elements for plant nutrition, and tends to stabilize the pH, with the result that vegetables with a variety of pH preferences can be grown together successfully. Most vegetables prefer soils that are neutral or slightly acid (pH 6.5). See chart of pH preferences in supplementary section of this lesson.

A slightly-acid soil is best for availability of nutrients. I) the soil is too acid, calcium, magnesium, and phosphorus levels decrease, and manganese and aluminum may be too available, even toxic. The pH of a very acid soil can be raised by adding dolomite lime. In alkaline soils over pH 7.5, iron, copper, manganese, zinc, and phosphates may become less available. Organic matter is the best remedy for such very alkaline soils. Humus or organic matter tends to neutralize either overly-acid or overly-alkaline soils.

For simple pH readings, you can test your soil with a kit. If serious problems persist, professional soil analysis can point out sources of trouble. Most gardeners discover what will grow well in their soil by observation and trial-and-error.