On Lime, pH, and Nutrient Availability

For optimum crop growth, you need optimum nutrient availability. For optimum nutrient availability, you need the right pH. For the right pH, you might need lime. To know all of that, you need a soil test. Now is the time to know your needs for lime.

Your soil test will show the field’s place on the Shoemaker-McLean-Pratt (SMP) buffer index, which we use to determine liming rates to correct your soil’s pH. For corn, you need lime if your soil’s pH is less than 5.8 on the SMP or 6.0 for beans.

“When it’s below these numbers, we recommend liming,” said Federated agronomy sales manager Kevin Carlson. “The rate is determined by our Quarry Ag Lime Table, which we’ve used for several years, because we spread standard quarry ag lime.”

The reason it’s so important to spread lime at the correct rate is spelled out on our pH & Nutrient Availability Table. Nutrient availability is one of the biggest reasons for correcting low pH. If your pH is off by even a little, bad things can happen. It’s best to be in the 6.0  to 7.0 soil-acidity range. 

Maintaining your pH in the right range is important for optimum crop growth and nutrient availability.

“Very slightly acidic is best, unless you’re growing alfalfa, which should be neutral,” Carlson said. “There are a lot of tie-up as pH starts to drop. pH is not a numeric scale; it’s a logarithmic scale, which means that the difference in one pH unit is actually a difference of 10 times. For instance, going from 7 to 6 on the pH scale is actually a difference of 10 times the acidity, and going from 7 to 5 is 100 times more. So it’s important to get it right!"

To recap: Get a soil sample, use it to determine your pH, then spread lime as needed. Federated will help with all of that. Just call your Federated Agronomist to get started.