There are three numbers on a bag of fertilizer that can be a baffling set of digits, essentially meaningless to many food plotters.
“They indicate the ratio of nitrogen (N), phosphorous (P) and potassium (K),” says Mississippi State University plant and soil sciences associate
professor Dr. Keith Crouse. “They are always in the same order, no matter what the number actually is.”
Those numbers, he explains, are a percentage of each element. An even fertilizer, 10-10-10, for example, has equal parts of nitrogen, phosphorous and potassium. The remaining 70 percent is filler that helps spread the fertilizer evenly. In some cases, the remaining percentage also consists of trace minerals and other nutrients that benefit the soil. A higher number, 20-20-20, for example, has more of each nutrient, meaning you won’t have to use as much on each application.
Fertilizer Type and Amount Required
So what’s the right fertilizer and, more importantly, how much should you use?
Crouse says the only way to determine exactly how much fertilizer you need is with a soil test. In fact, fertilizing is pointless until you take that step. “You could be spending a lot of money you don’t need to be spending if you don’t conduct a soil test,” he said. “In some cases, you could even damage your food plots.”
Applying too much fertilizer can actually kill your food plots by feeding them too much. Excess fertilizer is also a major cause of poor water quality, as unused nutrients run off fields and into streams, rivers and lakes. The heavy load of fertilizers creates algae blooms, which ultimately deplete oxygen levels in the water, stressing or even killing fish and other aquatic life.
Fertilizing Is Pointless Until You Get the Soil Tested
A soil test is a simple, inexpensive process that will tell you exactly how much of each nutrient to put down. Virtually every state cooperative extension office and even food plot seed manufacturers like Whitetail Institute and Mossy Oak BioLogic conduct soil tests for a small fee, usually under $10. Simply send a small bag of dirt along with a standard form and you’ll receive recommendations for fertilizer and lime applications, usually in pounds per acre. You’ll have to do a little math to figure out exactly how much to put on your plots, but it’s certainly the best money any food plotter will spend.
For example, you might not need to put nitrogen on some plants. Clover “fixes” nitrogen in the soil. That is, it actually converts nitrogen from the air and puts it into the ground. Spreading additional nitrogen likely won’t have any benefit to the clover, but it will feed unwanted grasses in your food plot, creating more competition for other nutrients, moisture and root space. That’s why it’s a good idea to fertilize clover with a mix higher in phosphorous, which promotes root growth, and lower in nitrogen. Clover and other legumes like beans and alfalfa also benefit from higher doses of potassium, which protects against heat and cold stress and helps protect against diseases. However, grasses like corn, wheat and rye require lots of nitrogen, so a fertilizer with a high first number and lower second and third numbers (such as 28-4-8) are best for annual grasses.
“A soil test will tell you exactly what ratio your food plots need,” says Crouse. “And your local farm supply store can custom-mix fertilizers for you.”
Related: Soil Samples for Food Plot Readiness
Balance the pH
Just as a soil test will determine how much and what type of fertilizer you need, it will also tell you your soil’s pH (potential hydrogen) level, which is a measure of a soil’s acidity. A measure of 7.0 is neutral; anything lower is acidic while a higher number indicates basic soil. Generally, a pH level of between 6.0 and 7.0 is good for most food plot plants, with 6.5 the best all-purpose pH level. Lime is even more important than fertilizer, because a proper pH level allows plants to take in the nutrients in the soil.
“If you have to choose between buying fertilizer and lime, I’d opt for the lime, because if the pH isn’t right, your fertilizer won’t give you the results you will get with a proper pH level,” he says.
Pelletized lime is the most common type sold, but it can take up to six months to have a full effect on soil acidity, so Crouse suggests putting lime down well ahead of your planting date. If you don’t have time, consider a hydrated lime. It’s more expensive but begins working on the soil’s pH level almost immediately. Crouse also says it’s a good idea to disk the lime into the soil so it affects the soil closest to the roots, but top-spreading it will work just fine in established plots. The effects of a single lime application can last up to three years, but it’s a good idea to conduct a soil test once a year to make sure the soil’s pH and nutrient levels are adequate. Fertilizer can be spread just about any time of year, but it will help the plants most if it is spread when the plot plants are actively growing.
It’s not mandatory to fertilize and lime your plot plants. They’ll grow without the extra help. But why go to all the trouble of disking, seeding and spraying without helping your food plots reach their full potential? Healthy food plots translate to healthy deer, and that means you’ll have a more rewarding hunting season.
Featured photo: iStock