Ask an Agronomist
What Do You Think About Sidedressing With Urea?
Nov 15, 2011
Question: What is your opinion about sidedressing with urea? Also, when is the best time or at what height of the corn is best?
Answer: When we talk sidedressing with urea that’s typically done with a buggy or with an airplane. It’s rare to see someone knifing urea in as a sidedress application. I’m not saying it can’t be done but that it’s rare. Because you’re surface applying the urea you have to protect it from loss through volatility, meaning you need to either use a coated urea or you need to put a urease inhibitor down with the urea. As for timing of application, I would recommend applying two-thirds of my nitrogen upfront either pre-plant or at planting and the rest as late as the sidedressing equipment will allow. That’s probably around V6 with a tractor and fertilizer buggy or one or two leaves pre-tassel with an airplane, Your goal is to not see any nitrogen deficiency during the vegetative or reproductive stages. Also, for sidedress applications, farmers have a choice in what nitrogen product to apply. Many are asking if there is an agronomic difference between 28% and anhydrous ammonia. At sidedress, as far as the plant’s uptake of the nitrogen, these products will both convert to ammonium and nitrates for uptake. The difference between these two is their timing of availability. If you had yellow corn, and you were to sidedress the corn to make it green, 28% has ammonium and nitrate, and that turns corn back green. So you’ll see a quicker response to 28%. Anhydrous ammonia is different. With anhydrous, you create a core and it could be 14 days before nitrogen would be released from that core. If you’ve applied enough nitrogen upfront to keep the corn green through the vegetative stages, and you’re sidedressing N for ear fill, there most likely will be no difference between anhydrous and 28%.