Answer: The acidity or alkalinity of the soil is measured by pH (potential Hydrogen ions). Basically it is a measure of the amount of lime (calcium) contained in your soil, and the type of soil that you have. Generally, soils in moist climates tend to be acid and those in dry climates are alkaline. In general, a soil with a pH lower than 7.0 is an acid soil. One with a pH higher than 7.0 is alkaline.
A soil test is necessary so you'll know what you're working with and how much lime to add to change the soil's pH. Once you have determined the pH you can amend the soil to accommodate the plants in your garden.
Because different soil types react in different ways to the application of lime you will have to add more lime to clay soils and peaty soils than you will in sandy soils to achieve the same results.
To increase your pH by 1.0 point and make your soil more alkaline, add 4 ounces of hydrated lime per square yard in sandy soils; or add 8 ounces of hydrated lime per square yard in loamy soils; or add 12 ounces of hydrated lime per square yard in clay soils, or add 25 ounces of hydrated lime per square yard in peaty soils.
Correction of an overly acid soil should be considered a long term project, rather than trying to accomplish it in one year. It is better to test your soil each year and make your adjustments gradually. The addition of hardwood ash, bone meal, crushed marble, or crushed oyster shells will also help to raise the soil pH to make your soil more alkaline.
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