Don’t guess – do a soil test

Horticulture Hints

Spring is a great time for amending the garden soil, and getting it prepared for the upcoming growing season. Soil test results will provide you with soil nutrient levels and fertilizer recommendations when needed. Soil testing helps avoid unnecessary applications of fertilizer when guessing the amounts to apply, and avoid use of excess nutrients which can pollute local waterways. Test results also help to improve plant health by checking your soil pH.

The soil pH is important because it affects the availability of essential nutrients. The pH scale runs from 0 to 14. Any pH below 7.0 is acidic and any pH above 7.0 is alkaline. A pH of 7.0 is neutral. Most vegetables, fruits, annuals and perennials grow best in slightly acidic soils with a pH between 6.0 and 7.0. Plants may not perform as well in soils with a pH of 7.5 or above because of the reduced availability of some essential nutrients.

A soil test will indicate the current soil pH and, if necessary, the amount of lime to apply to the area. Liming materials include ground limestone which is mainly calcium carbonate (CaCO3) and dolomitic limestone which contains calcium carbonate and magnesium carbonate (MgCO3).

Vegetable and flower gardens can be improved by applying and incorporating organic matter, such as compost, well-rotted manure or peat, into the soil. Work the organic matter into the top 8 to 12 inches of soil. Soil test results will show the amount of organic matter (OM) in your soil.

Did you know? Iowa State University Soil Laboratory no longer performs garden soil testing. So where to go for testing? Soil testing is available thru many private and state laboratories. For help in selecting a soil testing site or directions on taking soil samples, please feel free to contact me.

Horticulture Questions? Contact McCormick at for information or advice.