By Dawn Pettinelli for UConn Extension
Soil testing is an inexpensive, yet valuable, tool for assessing the fertility of lawn and garden areas. Test results indicate the soil’s pH level, the amounts of available plant nutrients, and the existence of nutrient imbalances, excesses or deficiencies.
WHY SHOULD I HAVE MY SOIL TESTED?
Soil testing eliminates the guesswork many gardeners face when deciding the kinds and amounts of fertilizers or soil amendments they should purchase and apply. Each soil test report contains recommended amounts of limestone and/or fertilizer needed for optimum plant growth. Knowing how much to apply saves time and money.
It is a smart decision to test the soil every few years. Further- more, it is particularly important in new garden bed installations or in established plantings that are not performing as well as expected. Regardless of whether you garden organically or use synthetic fertilizers, you will find that plants grow best when their nutritional requirements are met. This is achieved not only by the addition of nutrients such as nitrogen, phosphorus and potassium but also by sometimes modifying the soil’s pH through the incorporation of limestone or sulfur.
Soil pH is a measurement of the acidity of the soil. A pH of 7.0 is neutral, below 7.0 is acidic, and above 7.0 is alkaline. Native soils tend to be acidic. It may be necessary to raise the pH by adding limestone. Plant species vary in their soil pH preference. Blueberries and broad-leaved evergreens, such as rhododendrons, may develop iron deficiencies if the soil pH is too high. Lack of calcium from low soil pH may contribute to the physiological condition known as blossom end rot, which affects tomatoes and summer squash.
Applying the proper amounts of limestone and fertilizer pro- motes healthy, productive plants. In addition, it minimizes the potential for water pollution from over-application of nutrients, especially nitrogen and phosphorus.
WHAT CAN SOIL TESTS DETERMINE?
The standard nutrient analysis will provide the soil sample’s pH and the available amounts of phosphorus, potassium, calcium, magnesium, micronutrients and an estimate of total lead. Site-specific fertilizer recommendations are provided based on the soil test results. Recommendations for modifying the soil pH with limestone or sulfur are made if necessary.
Separate analyses offered by the lab include: percent organic matter, particle size analysis (the relative amounts of sand, silt and clay), micronutrients, soilless media and soluble salts. Commercial agronomic or vegetable growers may be interested in our presidedress soil nitrate test.
WHAT CAN SOIL TESTS NOT DETERMINE?
The soil fertility test performed at UConn cannot detect the presence of contaminants such as pesticides or petroleum products. A listing of state approved environmental laboratories which can perform these analyses is available at the Connecticut Department of Public Health’s website, www.state.ct.us/dph
Our soil tests also cannot identify problems due to insects, diseases, poor or excessive drainage, environmental stresses such as drought or winter injury, or improper cultural techniques.
WHEN IS THE BEST TIME OF YEAR TO HAVE MY SOIL TESTED?
A soil sample can be collected any time the ground is not frozen. The lab performs soil analyses year round. Fall is an optimal time for sampling because added amendments can begin to react with the soil over the winter. When submitting samples in the springtime, try to send them in early enough to give yourself time to prepare your beds before planting. Generally, the turnover time is 3 to 5 days in the lab but may be longer in April and May.
A soil test every 3 to 5 years is adequate for most situations. An exception to this would be sites requiring large nutrient additions or pH adjustments. In this case, it would be advisable to test one year after the recommendations for limestone and/or fertilizer were followed to monitor their effect. Whenever comparisons of results are desired, take samples at the same time of year.
For more information on having your soil tested please visit: http://www.soiltest.uconn.edu or call 860-486-4274.
