What is the first thing you should look at when you get a soil test report back from a lab, or from your consultant who is dealing directly with the lab? Brian Early believes it is soil pH.
Early is DuPont Pioneer's production agronomist for northeast and east-central Indiana. Before his career with Pioneer, he operated his own crop consulting business and was heavily involved in soil testing and interpreting soil test results for customers.
"Soil pH is often overlooked, but that is where your soil fertility program should start," he emphasizes. "The reason it is so important is because it determines how available other nutrients are to crops in the soil. Once you have soil pH where you want it, the nutrients you apply will be more available to the crop."
Availability varies by the nutrient. Some are tied up and not available at very low pH, while others get tied up in the soil at very high pH levels. Early says a good goal is to get your soils in the 6.0 to 6.5 range, preferably closer to 6.5.
Corn can tolerate acidic soils somewhat better than some other crops, but still does better if pH is near 6.5, he says. For soybeans and especially alfalfa, having the pH near 6.5 is critical. Actually, Early suggests pH levels of 6.5 to 7.0 for alfalfa.
You will see two values reported on most soil report forms – one is soil pH and the other is buffer pH. The one you want to pay attention to know whether your soils are acidic or not is soil pH, Early says. Buffer pH gives you an indication of how quickly your soils will respond to lime if lime is needed.
"I would spend dollars devoted to soil fertility on lime first if it's needed," Early concludes. "That's how important it is."