Extension folks are always telling you to get your soil tested every 3-5 years. Why is that? Whether you are testing the soil in your lawn, garden, or farmland, a basic soil test can provide a lot of useful information.
What will a soil test tell us? Soil is a very complex mixture of living organisms, minerals, organic materials, water, and gases, so there’s a lot that you could potentially test! A basic soil test will usually focus on the chemical part of the soil, and will describe the percentage of organic matter, the pH of the soil, and the amounts of phosphorus (P), potassium (K), calcium, and magnesium. All of these are necessary for plant growth and development. While properties of soil tend to change fairly slowly over time, testing regularly can help you learn the limitations
One of the most important measurements on a soil test is pH. This measurement describes the acidity of the soil on a scale from 0-10. You may hear soil described as sour or sweet. Sour means acidic (pH less than 7.0), and sweet means basic (pH greater than 7.0). In west-central Indiana, we usually expect to see soil pH a little sour to just about neutral, between 6.0 and 7.0. This range is suitable for growing most garden plants, lawns, forages, and row crops, although some plants and crops have varying needs. A pH that is too high (too sweet) or too low (too sour) can prevent plants from getting enough of several essential nutrients. Plants with nutrient deficiencies will look sickly – yellow leaves, stunting, and failure to thrive are all potential symptoms of nutrient deficiencies affected by pH. Fun fact: there are some plants that can serve as a visual indicator of soil pH. Around here, the plant to look for is bigleaf hydrangea (Hydrangea macrophylla). In acidic soil conditions, the plant will accumulate aluminum, which turns flowers purple to blue. In basic soil conditions, flowers will range from pink to red.
Once you know the pH of a soil, you can work to mitigate a pH that is too high or low by adding appropriate amounts of acidic products or lime, and then move on to addressing nutrient deficiencies by applying fertilizers or compost. As your local Ag and Natural Resources Educator, I can help you calculate how much to apply. Addressing the pH before applying fertilizers ensures that any products you use will be utilized by plants effectively!
Soil testing can be completed in early spring or in fall after crops have been harvested. The best results will come from sending a soil sample to one of several soil testing labs around the Midwest for a thorough chemical analysis. At-home kits will not provide results that are reliable. If you have any questions about soil testing, please give us a call at the Montgomery County Extension Office!


Ashley Adair is the Extension Educator for Agriculture & Natural Resources at Purdue Extension – Montgomery County. She can be reached at (765)-364-6363 or holmes9@purdue.edu.