Sidedressing Potassium For Corn—Is It An Option?
Robert Mullen, Ph.D.
Director of Agronomy
To say Dr. Robert Mullen is passionate about agriculture would be an understatement. He holds a Bachelor of Science degree in ag business from Cameron University, along with a Master of Science degree in plant and soil science and a Ph.D. in soil science from Oklahoma State University. In addition, Dr. Mullen has been published in a variety of scientific and trade journals. But it’s not just his academic accomplishments that make him unique. It’s his unwavering ability to take complex data and — in simple terms — explain how it impacts a farmer’s bottom line. Dr. Mullen delivers the kind of insightful observations that can lead to a more profitable business. As a leading agronomy expert, Dr. Mullen has a goal to further educate farmers on best management practices that improve their yields and maximize their return on investment.
A question that often arises is, “If I missed my fall and spring application of potassium, can I sidedress my corn crop to make up for it?” This question has been especially prevalent the last two years. The answer is typically yes, you can—but it may not perform as well as a fall/spring application.
Iowa State University just published an article dealing with this very issue (that article can be found here). As one might suspect, the greatest response to sidedress potassium (in a liquid form) was in soils that were classified as below the optimum (although some optimum soils did show response to potassium—albeit with smaller yield increases). The timing of the sidedress potassium was applied mid-row to a depth of 3-4 inches at the V5-V6 growth stage.
The conclusion of the research was that broadcast preplant potassium resulted in greater yield responses above the respective control plots than sidedress potassium applied at equivalent rates (especially the lower rates). This research does indicate that sidedress potassium can be an option if other application timings were missed, but purposefully delaying potassium sidedressing may not be the best approach.