By Aaron Kuehl
Quality food plots are an investment of time, labor and money. Their success is a function of good site selection, quality seed, weather and the soil. Only a soil test provides the information necessary to maximize the food plot's full potential and save you money by reducing unnecessary input costs.
Plant growth and vigor are dependent on soil pH and the available nutrients. For food plots, we are most directly concerned with pH, Nitrogen (N), Phosphorus (P) and Potassium (K). pH is the master variable in your soil and determines nutrient availability for your plants and can impact the effectiveness of herbicides.
Avoid DIY soil test kits available at garden centers, and instead send your soil sample to a lab. A lab test will not only provide you with soil conditions, but also recommendations specific to your crop. Your local Extension Service office should have a list of area labs or, occasionally, a sample kit.
Ideally, soil tests should be conducted in the fall mainly because if lime is necessary to adjust your soil pH, it’s best to allow it several months to work. If you miss your fall test window, you can test in the early spring.
All you need for sampling your soil is 1) a clean plastic bucket (2.5 – 5 gallon buckets work great) to mix your sub samples, 2) a soil probe or spade to collect the sub samples and a Ziplock bag. Collect your samples, complete the required soil test form and drop them in the mail. IMPORTANT: not all soil labs provide nitrogen levels in their standard report, but will do so for an additional fee. Since nitrogen is typically the most limiting nutrient, you should ensure those levels are reported. Also, be sure to provide the type of crop you will be planting as this does affect the recommendations.
Fertilizer (NPK) recommendations will be in pounds per acre but unfortunately that’s not how its sold. A bag marked 16-4-8 contains 16% Nitrogen, 4% Phosphorus and 8% Potassium. To convert to pounds, simply multiply the percentage by the bag weight (ie if the bag weighs 50#, 0.16*50= 8#s N, 0.04*50=2#s P, 0.08*50=4#s K). Once you have the poundage, you’ll need to multiply that by your need per acre.
For a more detailed look at the methodology and interpretation of soil testing and other habitat topics view our new Habitat Information Sheets
And remember: Make every acre count, think habitat!
Kuehl is Pheasants Forever and Quail Forever’s Director of Seed Operations.