Testing the pH level of garden soil is an important step to maintaining a healthy garden, even if it has been successful for many years. PH levels range from 1 to 14, with the neutral value as 7; 1-6 is considered acidic, and 8-14 is alkaline. The most plants grow well in the middle of that range from a 6.0 to 7.0. PH levels also affect the nutrients that a plant receives, and those levels can change over time.
If you grow pH-sensitive landscaping plants or vegetable crops, knowledge of your garden’s soil pH level is an essential part of proper plant maintenance. Without knowledge of your soil’s pH, soil preparation and fertilization is essentially a shot in the dark. Under-or over-fertilization can lead to poor plant performance, plant damage, and even plant death. Furthermore, over-fertilization is taxing on the natural environment.
About Soil pH Measurements
Soil pH measures acid-forming hydrogen ion activity in a soil and is important in understanding the availability of nutrients within the soil. The pH scale ranges from 1 to 14, with the center point, 7, being neutral. As pH falls below seven, acidity increases. As pH rises above seven, alkalinity increases. While many plants can do well in soils anywhere near the center range of the pH scale, other plants have more specific requirements. A soil test is the only way to dependably establish soil pH.
Basic Testing Methods
There are two basic methods of conducting a soil pH test: use a commercial test kit at home, or send a soil sample to a laboratory for testing. Most experts highly recommend laboratory testing over commercial test kits. Commercial test kits are relatively unreliable and do not include detailed soil data or recommendations on amending your soil, should its pH be out of range.
In most areas you can find a government or university operated soil-testing laboratory that accepts soil samples from gardeners for comprehensive testing. Contact your county agricultural office or the agricultural department at your local university for local testing information. In most cases, testing is free or very low cost. If you are located far from the nearest lab, you can usually download the soil test forms online and submit your soil sample by mail. The soil test forms will ask you to identify the plants you intend to put in the soil.
To take a sample, use a stainless steel or chrome plated trowel or coring tool. Dig a narrow hole to a depth of about eight inches. Then scrape a sample from the side of the hole, starting at the bottom. Deposit the sample in a clean container. Repeat this process in at least six spots around the planting site, combining the samples in the same container. Finally, submit your soil sample and test forms as required by your local laboratory.
Top alkaline plants: Clematis, hebe, forsythia, campanula, aubretia
Top acidic plants: Camellia, rhododendron and azalea, dogwood, Japanese maple