No simple answers on soybean fertilizer use

There are no easy or one-size-fits-all guidelines for applying key fertilizers on soybean fields. An Extension soil fertility specialist looked at some of the key considerations.

With soybean prices on the rise, more farmers may be looking to grow the crop. Daniel Kaiser, extension soil fertility specialist with the University of Minnesota, offered soybean fertility advice in a recent webinar. (Erin Ehnle Brown / Grand Vale Creative LLC)

Soybean prices are soaring , and so area farmers are evaluating whether to plant more of the crop this spring. That can make fine-tuning fertilizer application on beans especially important, an Extension specialist said.

The main thing for farmers to focus on is "the foundation of their soil fertility program. Looking for P and K mostly, soil testing, focusing on those applications," Daniel Kaiser, extension soil fertility specialist with the University of Minnesota, said in recent webinar.

P is agricultural shorthand for phosphorus, a widely used fertilizer than helps plants convert other nutrients into useable building blocks with which to grow. K stands for potassium, another widely used fertilizer that helps to strengthen plants' ability to resist disease and plays an important role in increasing crop yields and overall quality.

Among Kaiser's top recommendations:

"Don't buy what you don't need," he said.


Kaiser spoke Jan. 25 during the Virtual Best of the Best in Wheat and Soybean Research. The online event, open to the news media, was sponsored by the North Dakota State University and the University of Minnesota Extension, along with the Minnesota Association of Wheat Growers, Minnesota Wheat Research and Promotion Council, Minnesota Soybean Research and Promotion Council, North Dakota Soybean Council, North Dakota Grain Growers Association and North Dakota Wheat Commission.

Many of the attendees work in the Red River Valley of western Minnesota and eastern North Dakota, so parts of the presentation were geared specifically for soybeans grown in that specific area.

Nitrogen is another key nutrient, one that helps all aspects of a plant's healthy growth. Part of soybeans' appeal is that the plants, a legume, provide their own nitrogen by pulling it from the atmosphere and converting it into a form the plants can use. Now, there's some evidence that especially high-yielding soybeans also need fertilizer applied by the farmer to achieve those high yields.

Kaiser, asked about that, said that in most cases the additional yield doesn't justify the nitrogen application. A possible exception are fields in which soybeans are being grown for the first time.

Kaiser also recommended focusing on the timing of phosphorus and potassium applications when data suggests it's critical.

Flexibility is essential, he said.

"There isn't one best strategy to manage P and K for all fields," he said.

The value of micronutrients, or chemical fertilizers that include boron, chlorine, copper, iron, manganese, molybdenum and zinc, appears to be limited on Minnesota soybeans, Kaiser said.


"We've looked at this a number of times, and I have not been able to track any consistent data that shows any clear response to any micronutrient across a wide range of fields across the state," he said. "Manganese for soybeans might be the only one you want to watch."

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