A soil test is the first step for any food plot endeavor. A completed test provides a wealth of data about your soil’s current condition, as well as helps you steer your food plot creation in the right direction by recommending the ideal level of nutrients to add. The results provide a road map to growing greener grasses, better brassicas and addicting alfalfa.
A soil test is just that: A scientific evaluation of your soil’s nutrients, acidity and trace minerals. All three are vital ingredients in the food plot equation. Professional tests are conducted in a laboratory using high-tech equipment that takes precise readings. They are far more accurate than any at-home kit you can buy. And they are a lot easier.
“Take eight to ten core samples from zero to six inches deep, put them in a clean container, mix it all up, put as much as will fit in the sample box we provide and send it to us,” says University of Tennessee Cooperative Extension soil lab director, Dr. Robert Florence. “Make sure you mark the type of plant or plants you want to grow so we can tailor the amendments to those plants.”
In a couple weeks, you will receive an email that spells out your soil’s current pH, phosphorous and potassium levels, along with other trace minerals like zinc and magnesium. One element that isn’t included is nitrogen. That’s because nitrogen is volatile. It doesn’t stay in the soil long and is often absent or present in low levels.
“We only test nitrogen levels for corn and wheat and only when those plants are young,” says Florence. “How much is in the soil before you plant doesn’t really matter. What matters is how much you add when you plant.”
Soil test results will include recommended application rates of lime and nutrients, including nitrogen, phosphorous and potassium (also called potash) for the specific plants you want to grow.
Nitrogen is what turns plants green and builds strong leaves. It is especially important for grasses like oats and wheat. Phosphorous helps plants produce flowers, seeds and stronger stems. Potassium also contributes to stronger plants, helping them survive drought and disease.
These elements are represented by N, P and K, respectively, on your results and the numbers in the recommended fertilizer section represent the ratio of each element in a particular fertilizer. Therefore, a 10-10-10 fertilizer will have 10 percent each of nitrogen, phosphorous and potassium. The remaining 70 percent is filler.
Some soil tests recommend specific types of lime, usually either a dolomitic or calcitic lime, which is more commonly called aglime. It is what farmers typically use. Which one is right for you?
“Either one will get your soil’s pH to the right level if you use the recommended amount,” says Florence. “Most farm service companies use aglime, which typically comes in a powdered form. The pelletized lime you get from garden stores is often dolomitic lime and is easier to spread if you are using your own equipment, but that may not be practical if your soil requires a large amount. The bottom line is that either is fine.”
You shouldn’t be concerned with trace minerals like zinc, manganese and magnesium, either. All three play a role in soil health and plant growth, but Florence says that unless you are trying to grow grain crops for harvest, there is no need to worry about their levels.
“Just stick to the recommended fertilizer and lime application rates and you will be fine,” he says. “Dolomitic limestone can provide magnesium if your levels are abnormally low, but that is pretty rare.”
Whatever type you use, spread it well before you plant your seeds. “It can take weeks for lime to fully amend the soil’s pH level. And you want to make sure you disk it in,” says Steve Scott, Vice President of Whitetail Institute. “That’s important. If it just lays on the soil’s surface, it can take much, much longer to work down to the depth where it has the most effect or it might run off after a heavy rain.”
