5 Tips for Managing Potassium Fertilizer

Apr 12, 2019

By Daniel Kaiser

Decisions on optimal fertilizer management can be challenging in years with low commodity prices. Work is underway to overhaul the corn and soybean potassium (K) guidelines in Minnesota. When making decisions for applying K for corn and soybean, here are a few things that you should consider:

1. Focus on rate, not timing

Applying the correct rate that is needed over one or two years in a crop rotation has been shown to be more important than the time when the fertilizer is applied. Much of our current data has demonstrated that timing of application in a multi-year cropping rotation is not important. Applying ahead of the crop that will get the greatest advantage from the K is the best way to get the most bang for your buck.

2. Focus on a proven yield, not a yield goal

When making decisions about how much K to apply, it can be difficult to determine what yield should be used for both a sufficiency-based or build and maintenance strategy. Using a historical yield average is the best option. A value which you have proven can be produced is a smart way to ensure fertilizer is not over-applied. The soil itself is not devoid of potassium, so being exact on your predicted rates is not critical. Some fertilizer is always better than none in situations where a response to a nutrient is likely.

3. Stick to the same time of year when soil sampling

Sampling fields at similar times of the year is critical to ensure you can accurately determine how soil test values for K change over time. Potassium is different from other nutrients in that the soil test value is not static in the field over the growing season and can vary from fall to spring.

4. Apply K when and where it is needed

Soil tests are still the best option for deciding when and where K fertilizer should be applied. For soils higher in clay, like loams and clay loam soils, the chance for a profitable response to K fertilizer is very low when soil tests are around 200 parts per million K. For very sandy soils which do not hold K well, such as loamy sands, high rates of K may not be needed even though soil test values can be lower compared to higher clay soils.

5. Choose the right placement option

Research has shown that banding K can be more effective in some circumstances. Broadcast application of K in reduced tillage situations like ridge- and strip-tillage or no-till can stratify K near the soil surface, which can lead to poor uptake if soils become dry. While banding K is not always needed, identifying situations where it is beneficial is key to ensure optimal productivity.

It is a good time to start reviewing fertilizer decisions as we wait for fields to dry this spring. There are situations where potassium may not be needed, so knowing which fields need K could save time this spring.

Source: umn.edu

Video: Why Your Food Future Could be Trapped in a Seed Morgue

In a world of PowerPoint overload, Rex Bernardo stands out. No bullet points. No charts. No jargon. Just stories and photographs. At this year’s National Association for Plant Breeding conference on the Big Island of Hawaii, he stood before a room of peers — all experts in the science of seeds — and did something radical: he showed them images. He told them stories. And he asked them to remember not what they saw, but how they felt.

Bernardo, recipient of the 2025 Lifetime Achievement Award, has spent his career searching for the genetic treasures tucked inside what plant breeders call exotic germplasm — ancient, often wild genetic lines that hold secrets to resilience, taste, and traits we've forgotten to value.

But Bernardo didn’t always think this way.

“I worked in private industry for nearly a decade,” he recalls. “I remember one breeder saying, ‘We’re making new hybrids, but they’re basically the same genetics.’ That stuck with me. Where is the new diversity going to come from?”

For Bernardo, part of the answer lies in the world’s gene banks — vast vaults of seed samples collected from every corner of the globe. Yet, he says, many of these vaults have quietly become “seed morgues.” “Something goes in, but it never comes out,” he explains. “We need to start treating these collections like living investments, not museums of dead potential.”

That potential — and the barriers to unlocking it — are deeply personal for Bernardo. He’s wrestled with international policies that prevent access to valuable lines (like North Korean corn) and with the slow, painstaking science of transferring useful traits from wild relatives into elite lines that farmers can actually grow. Sometimes it works. Sometimes it doesn’t. But he’s convinced that success starts not in the lab, but in the way we communicate.

“The fact sheet model isn’t cutting it anymore,” he says. “We hand out a paper about a new variety and think that’s enough. But stories? Plants you can see and touch? That’s what stays with people.”

Bernardo practices what he preaches. At the University of Minnesota, he helped launch a student-led breeding program that’s working to adapt leafy African vegetables for the Twin Cities’ African diaspora. The goal? Culturally relevant crops that mature in Minnesota’s shorter growing season — and can be regrown year after year.

“That’s real impact,” he says. “Helping people grow food that’s meaningful to them, not just what's commercially viable.”

He’s also brewed plant breeding into something more relatable — literally. Coffee and beer have become unexpected tools in his mission to make science accessible. His undergraduate course on coffee, for instance, connects the dots between genetics, geography, and culture. “Everyone drinks coffee,” he says. “It’s a conversation starter. It’s a gateway into plant science.”