Having potassium in the soil doesn't necessarily mean your crop can access it when it needs it most. Dr. John Murphy and Ben from AgXplore join Farm4Profit to explain potassium demand, plant availability, stress management, application timing, and why late-season potassium could be an overlooked opportunity for both corn and soybeans.
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Potassium is a macronutrient crops need throughout the growing season, but simply having adequate soil levels doesn't guarantee the plant can access it. The AgXplore team explains that roots only explore a portion of the soil profile and potassium movement is heavily tied to water—creating a challenge during dry late-season conditions when crop demand can still be significant.
Dr. John and Ben discuss potassium acetate as a highly plant-available form and explain potassium's role in photosynthesis, stalk quality, standability, and the opening and closing of stomata. That stomatal function becomes especially important under heat and moisture stress because it affects transpiration and the plant's ability to continue moving water and nutrients.
The conversation then turns to timing. AgXplore's Nutri-K provides potassium acetate, while KSB combines potassium, sulfur, boron, and biostimulants. The team says late-season applications have produced positive results across several crops and geographies. In one replicated Wisconsin trial discussed in the episode, potassium treatments improved yield by roughly 5–10 bushels, with the guests citing a minimum ROI around 6-to-1 in that trial. They also found that stacking an earlier application with a later application performed better than a single application.
The bigger takeaway isn't simply to apply more potassium. It's about understanding the crop's demand curve and supplying “the right groceries at the right time.” Soil fertility still provides the foundation, but strategically timed nutrition may help keep the crop functioning and finishing stronger when environmental conditions make soil uptake more difficult.