Managing potassium fertilizer

Potassium (K) is a nutrient associated with the movement of water, nutrients and carbohydrates in plant tissue. When making decisions for applying it for corn and soybeans there are a few things you should consider.

Dan Kaiser is an extension nutrient management specialist at the University of Minnesota. He says applying potassium fertilizer ahead of corn will give you the best bang for your buck. However, data is showing a different outcome with soybeans.

"We see more risk for yield decreases from high rates of potassium which could be attributed to chloride toxicity because many of our northern varieties are sensitive to over-application of chloride. That’s been a main research emphasis I’ve had, trying to get a handle on that sensitivity and getting a more targeted recommendation for the soybean crop," says Kaiser. "You know, just split applying, especially if you have to put a high rate, seems to be the right way to do that."

He says soil tests will tell you where potassium fertilizer should be applied. Sample your fields at the same time of year every time you test because potassium levels can vary from fall to spring.

Placement of the nutrient is key, especially in reduced or no-till situations.

"With potassium, one thing that’s critical for uptake is to have some soil moisture at the point where most of that potassium is in the soil. So, in a reduced till or no-till situation, if you’re looking at a broadcast application to the soil surface, we tend to see a lot of stratification in the upper inch or two of soil," he says. "If that dries out, that plant can struggle in getting the potassium it needs. So, in that situation, banding may be a better option."