Professional soil testing is a relatively inexpensive way to ensure gardeners are taking the right steps to improve soil. Doing it in advance of planned projects allows time for necessary improvements to be made. It can be done through private laboratories or through local cooperative extension offices, and should be done on a regular basis for continued soil improvement.
Professional soil testing requires gardeners to gather and submit soil samples to testing facilities. Individual sample-gathering procedures and prices vary by facility, but generally involve pulling samples of a specific size from several places in a yard or garden. Tests for pH, mineral content, and soil type (sand, loam, clay, or a combination) can be selected for different prices.
Professional soil testing should be performed at least two months prior to planned soil projects, such as gardens or sod laying, according to North Carolina State University Extension. This allows adequate time for test results to be received by the gardener, as well as time to enact the recommendations made by the test results. This also allows any necessary soil amendments time to address the problems they are meant to correct.
In the U.S., the cooperative extension office system makes professional soil testing accessible at reasonable prices throughout the country. Additionally, private soil testing laboratories can be found through consultation of phone books and internet searches. The advantage of involving a local cooperative extension system office is that their master gardeners are intimately familiar with that area's challenges, and can give more specifically targeted information to gardeners.
Simply guessing that soil needs something, or applying nutrients just because a particular plant is known to benefit from them (epsom salts for rosebushes, for example) only works if the soil needs those nutrients. Overapplication of nutrients disturbs the balance of the soil, making it difficult for plants to absorb necessary nutrition. The importance of soil's pH level is that it determines what nutrients are made available to plants for absorption.
Professional soil testing and following of recommendations made by test results ensures that these problems do not occur. It saves time and money by advising only necessary actions. It is also better for the environment, as application of the proper amounts of nutrients ensures no excess mineral runoff into local waterways.
Professional soil testing is a powerful tool to advance soil improvement. However, it should not be considered a one-time fix for all a soil's problems. Soil improvement is a continual process, and a new professional soil test should be done every three to five years to assess a soil's current state. All soil, no matter what its problems are, can be improved by the ongoing addition of organic matter (such as compost).