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This is a test: Knowing details about soil is critical for gardening success

This is a test: Knowing details about soil is critical for gardening success

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Gardening in the heat of August in Central Virginia can be difficult. The weeds seem to be taking over this late in the season and the humidity can remove a gardener’s motivation to fight them. However, there is one 15 minute gardening task you should complete this month that will pay dividends in your garden all year long — take a soil sample and have it tested.

Why, you might ask, should I have my soil tested? Soil tests are easy to do and will provide you with some of the key information you need to have a successful garden. Knowledge is power and guessing is expensive in terms of wasted time and money. We all want to do the right things for our landscapes, but feeding plants and lawns can be like feeding a young toddler. You can see signs of distress but you don’t always know what’s wrong. An inexpensive soil test will provide information about soil composition, pH, and the plant available levels of phosphorus, potassium, and seven other essential elements or nutrients. It also provides recommendations on whether any nutrients need to be added and how much of each nutrient to add. It’s like having a cheat sheet on how to have a better garden and avoid killing your plants.

Some homeowners have asked if they can just skip the testing step and go straight to fertilizing. Unfortunately, that’s a bad idea. Overapplication or application of unneeded materials can result in salt injury to plants, cause nutrient imbalances that retard plant growth, and has the potential to become an environmental pollutant. You can actually kill a plant or lawn through ‘kindness’. Nutrient toxicity is a condition where an overdose of one of the 16 elements for normal growth causes a plant to stop growing.

Using too much or the wrong type of fertilizer can have broader negative impacts than just damaging your home’s landscape. Nitrogen and phosphorus from home applications are currently major sources of pollution in our waterways. These nutrients lead to algae blooms, which feed bacteria population booms, which then causes a crash in oxygen levels that lead to fish kills. Therefore, you should use only the minimum of amount of fertilizer that your landscape needs and your soil test report will tell you what that amount should be.

Late summer is a great time to get your soil test done because soil is naturally depleted at the end of the growing season, testing labs are usually not as busy, and you will get your report in time to implement the recommendations. For example, if you receive a recommendation to apply lime a fall application allows for the 3 to 6 months that are needed for the lime to react with the soil before Spring planting.

To get started, you will need to collect a soil sample. The accuracy of the soil test and report is a reflection of the quality of the sample taken so follow the instructions provided by the soil testing lab to correctly obtain your sample. There are commercial testing labs that offer a variety of services or you can use the routine soil testing offered through the Virginia Cooperative Extension. The fee for the Extension’s routine test package is $10 per sample for in-state residents. The Goochland Extension office provides soil sampling boxes and instructions. They can be contacted at (804) 556- 5841 or at their office at 2748 Dogtown Road . You can visit Virginia Tech’s Soil Testing Lab’s website at to obtain even more insight into what your soil test report will contain.

So if the heat and humidity mean you only complete a few garden chores this month, make one of them digging up a soil sample. The results will be well worth it.

Cathy McCarthy is a certified Master Gardener through the Virginia Cooperative Extension and a member of the Goochland Powhatan Master Gardener Association. If you are interested in learning more about GPMGA programs or how to become a master gardener volunteer please visit

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