Garden Soil Preparation

09/09/10

Frann Leach

Different types of plants each require varying degrees of soil acidity or pH. Some plants are very sensitive to soil pH levels. Some garden plants will prefer acid soils while others prefer an alkaline soil. The acidity or alkalinity of soil is measured by pH (potential Hydrogen ions). pH is a measure of the amount of lime (calcium) contained in your soil, and the type of soil that you have. Soils in moist climates tend to be acid and those in dry climates are alkaline. A soil with a pH lower than 7.0 is an acid soil and one with a pH higher than 7.0 is alkaline. The soil must be adjusted to suit the plant which will occupy that area if it is not already within that plants requirement range.Testing Your Soil pH
Many garden centers will pH test a soil sample for you, or you can buy an inexpensive pH test kit at a nursery, or hardware stores.
These test kits generally consist of a test tube, some testing solution and a color chart. You put a sample of your soil in the tube, add a few drops of test solution, shake it up and leave it for an hour or so to settle. The solution in the tube changes color according to the pH of your soil. Compare the color of the sample with the color chart that came with the kit. Matching colors will tell you the pH of your sample. Quality pH test kits will have a chart to help interpret the test result.Adjusting Your Soil pH Levels
Once you have determined the pH you can make any needed adjustments to the soil. Materials to adjust your soil pH levels are available at your local garden center.Raising The Soil pH
To Make It More Alkaline
It is generally easier to make soils more alkaline than it is to make them more acid. 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 result.

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
Add 8 ounces of hydrated lime per square yard in loamy soils
Add 12 ounces of hydrated lime per square yard in clay soils
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 gardening season. It is easier 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 soil pH levels.Lowering The Soil pH
To Make It More Acid
If your soil needs to be more acidic, sulfur may be used to lower the pH if it is available.
To reduce the soil pH by 1.0 point:
Mix in 1.2 oz of ground rock sulphur per square yard if the soil is sandy.
Mix in 3.6 oz per square yard for all other soils.
The sulphur should be thoroughly mixed into the soil before planting. Sawdust, composted leaves, wood chips, cottonseed meal, leaf mold and especially peat moss, will lower the soil pH.
More Soil pH Tips
Always read and follow the manufactures recommendations when using chemical products.
Use appropriate protection such as a dust mask, and gloves.
The best way to adjust pH is gradually, over several seasons.
Lime should be applied only when tests show it to be necessary.
If the soil is excessively alkaline, you may find that you are better off to build a raised bed using topsoil purchased from a nursery.

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