For Larry Oldham, Mississippi Extension professor and plant and soil scientist, managing soil fertility depends on getting back to the basics.
"When dealing with soil fertility during hard times, we need to go back to the basics, know what we're purchasing, and know what will work to make an operation better," Oldham said. "We've got all kinds of wonderful tools and products we can use, but we must respect the soil. In the Delta, we have some of the most fertile, native soil on the entire planet. We need to respect that."
According to Oldham, Delta soil can provide all the mineral nutrients, everything except carbon, hydrogen, and oxygen, which is provided by the plant's leaves, to the soil.
"There's nothing wrong with the basics. I'm going to use some sports analogies," he said. "John Wooden won a bunch of national championships in basketball at UCLA, and the first practice day of each fall, he would teach his players how to tie their shoes. Wooden recognized the players already knew how to tie their shoes, but he wanted to make sure they did it the right way. Take care of the basics, and from there, everything else grows."
Farmers should start with a soil test that gives an overview of the phosphorus, potassium, pH, lime, and a few other soil nutrients. A soil test provides a snapshot in time of the soil's ability to provide nutrients throughout the growing season.
"A separate test called the lime requirement will give an indication of how much lime to apply to a field to get to a target pH. This is important because respecting the soil includes maintaining pH. Controlling the pH is a basic building block. It's like learning to tie your shoe," Oldham said.
The first step is an up-to-date soil test to know the condition of your soil fertility. Next, be careful with how you invest your money.
"Farmers are approached with all sorts of tools, products, and information," he said. "They will be told they need to use this or that, but for any product, ask for evidence. Look for unbiased, scientific evidence to back up a claim for any product before you invest in it. Every time you apply something in the field, whether it is fertilizer, a crop protection product, or so forth, that's an investment. Know what return you're going to get back on the investment.
"One thing we have relearned in recent years looking at soil fertility tests is you can tell if your soil will probably respond to fertilizer. It also shows if you don't need fertilizer. Which route is cheaper to go with? Since insurance fertilizer applications are costly, there is no need to buy it if you don't need it."
When investing in fertilizer
With soil testing always be aware of the philosophy behind the recommendations of where you get your soil tested because some labs can be more generous in their recommendations than others.
"Another aspect of soil testing is the recommendations you get in return. The recommendations must be based upon calibration and correlation data, which has usually been done looking at the soil test levels in the upper 6 to 8 inches of the soil.
Also, he said that even if you go down further and measure X pounds of potash or phosphorus and depth, what that means in terms of response is still debatable. We know plant roots go down further and use those nutrients, but if we go down further than normal and measure it, currently not much research will tell you what those numbers mean," Oldham said.
"Again, always consider the potential return on the investment. Fertilizer is not cheap. If you don't get a response from it, that's a negative return on an investment," Oldham said.
"Stick to the basics, and at the end of the day, be able to say that you did something to improve your operation based on facts."