Soil testing is an essential tool for cultural landscape preservation maintenance, as it reveals the health of the soil. Fertility varies over time, and soils that support lawns, field crops, orchards, and landscape plantings tend to become nutrient-depleted if organic nutrients, compost, or nutritional mulch have not been added in several years. Plants that produce crops are particularly heavy feeders.
Annual testing is appropriate for soils growing crop plants, but every 3-5 years is good for most cultural landscape components, including ornamental lawns. Spring and fall are the best times to test. Fall is particularly good if the park is preparing to plant or to seed the cultural landscape.
There are two ways to test soil:
- Test with a do-it-yourself kit purchased from a hardware store or plant nursery (for approximately $25)
- Use a USDA Cooperative Extension Service in your state or county (for $15-$20 per sample)
Our recommendation is to go with the pros, rather than do-it-yourself. The park will receive more accurate, comprehensive information from the Extension Service, along with recommendations on how to correct deficiencies. The USDA Cooperative Extension System is a nationwide, non-credit educational network. Each U.S. state and territory has a state office at the land grant university and a network of local or regional offices.
Use this map to find your local office.
Steps for Testing Soil
- Start by contacting your local Extension Agent to get a soil sampling kit. Obtain a sampling kit for each component of the landscape to be tested, i.e., lawn, shrubs and trees, orchards, meadows, field crops, display beds, etc. should be tested separately. The kit will contain a small box or bag for approximately one pint of soil, as well as a form for you to indicate the type of plants to be grown in the soil.
- Take a soil sample with a digging tool, such as a soil probe, trowel, shovel or spade. Be sure you can dig 3 to 6 inches deep. You’ll also need a clean bucket. With a soil probe, collect ribbons of soil about 2” long and 1” wide. With a trowel, shovel or spade, open up a 3 – 6” deep wedge-shaped hole and shave a 1” thick slice of soil from the edge.
- Take 10 – 20 random or systematic samples across the landscape component to be tested (see the diagram for examples of random and systematic sampling). Remove debris such as thatch or leaf litter or rocks from the soil and combine the 10 – 20 samples in the bucket.
- Put about a pint of the soil mixture into the sample bag or box.
- Repeat the procedure to create another sample for a different landscape component soil test (e.g., lawn, plant bed, orchard etc.). Use multiple tests for landscape components larger than one acre.
- Mail the sample with the form to the Extension Service lab (this is often associated with a university). Payment can be made with a government purchase card. Expect to pay around $20.00 per sample.
The results will be mailed to the park, with an analysis of Nitrogen, Potassium, Phosphorus, Calcium and Magnesium, along with pH, micronutrients, percentage of organic matter and soluble salts (an indication that too much synthetic fertilizer has been added in the past). The results will indicate whether the analysis is too high, sufficient, or too low for the plants the park is intending to grow.
- If the soil is low in nutrients: Most deficiencies can be addressed by incorporating compost or spreading nutritional mulch. Lawns will be healthier if a mulching mower is used to return the clippings to the surface.
- If the pH is too acidic: The Extension Service will recommend an application of granular or pulverized limestone (calcitic or dolomitic). This is most effective if worked down into the soil, rather than left on top. For too acidic soils in lawns, apply limestone after core aeration.
- If the pH is too alkaline: The Extension Service will recommend the application of elemental sulfur. Sphagnum Peat is a more organic soil acidifier; it adds organic matter to the soil when worked below the surface.
Can’t find what you need? Contact the Park Cultural Landscapes Program via email or the program lead in your region.