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Soil pH
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pH is a measure of the concentration of hydrogen ions (acid ions). A pH reading can range from 1 (extremely acidic) to 14 (extremely alkaline). A pH value of 7 is neutral.
When the pH of the soil is measured, a suspension of the soil is prepared. pH values are reported as pH (water) and pH (KCl). Remember that the pH (water) is, on average, one unit higher than pH (KCl) for the same soil.
The optimal pH (water) of soil for most crops ranges between 6.50 to 7.50. When the pH (water) drops below 5.30, too much aluminium is present in the soil. Aluminium is toxic to roots and root growth will be affected. If the pH (water) exceeds 7.50, nutrient elements like phosphate, zinc and manganese become insoluble and deficiencies can be induced.
In soils with a neutral to acid pH, the pH of the subsoil will usually be lower than that of the topsoil.
