Soil pH measures soil acidity. When a pH reading is below 7.0, the soil is considered acidic. Many plants, such as grass, appreciate a small amount of soil acidity, but too low a soil pH stunts a plant's growth.
Adding lime to a soil, according the University of Florida, changes a soil's pH level. Before an application of lime, a soil requires testing for its lime requirements. Garden soil tests are available from many university extension centers for a small fee. The test results will give you the exact amount of lime required to raise your soil to the desired pH level. The soil pH should be between a 6.0 and 7.0. Lime requires application according to the amount of product recommended by the soil test per 1,000 square feet or acre, according to Ohio State University.
Calcium carbonate, magnesium carbonate and other minerals compose agricultural lime, according to the University of Minnesota. Calcitic lime and dolomitic lime are both used for agricultural purposes and are included in the agricultural lime category. calcium carbonate makes up calcitic lime, while magnesium carbonate makes up dolomitic lime. Slow-acting dolomitic lime contains magnesium, which encourages plant growth.
Hydrated lime is a fast working version of agricultural lime. It is considered the strongest type available. Utilize hydrated lime in areas with heavy clay soil that needs a boost in pH. Use of hydrated lime in areas with loamy soil should be avoided, as hydrated lime is known to burn plant roots.
Use wood ash from a fireplace or fire pit to raise a soils pH, according to the University of Minnesota. Add wood ash only in small amounts, no more than 2 lbs. per 100 square feet of soil a year. The soil will contain too much potassium if more wood ash is used. Potassium in large amounts reduces a plant's ability to absorb nutrients.