Pretend you’re a crops consultant. A client applied 80 pounds of nitrogen per acre preplant and another 20 pounds of N per acre as starter. He has a good stand. Should he sidedress 50 pounds of N at V5 and save 50 pounds to apply later, or apply it all now? His typical rate is 200 pounds per acre.
This month's panel of Indiana certified crop advisers addresses this scenario. See how your strategy compares to their suggestions. The panel includes Traci Bultemeier, an accounts manager for DuPont Pioneer, Fort Wayne; Gene Flaningam, Flaningam Ag Consulting LLC, Vincennes; and Bryan Overstreet, Purdue University Extension ag educator in Jasper County.
Bultemeier: The standard has been 1 to 1.25 pounds of nitrogen per bushel for a total of 200 pounds of N. Growers have had success applying two in-crop passes of N in addition to preplant and starter. Rapid uptake of N starts around V6, so a V5 timely application is a good target. An at-tassel application may provide additional N needed to finish filling out grain. The amount of N available and the amount needed are dependent upon weather and soil type.
Flaningam: Split applications of N are more advantageous than a single application for both yield gains and environmental impact. Consider equipment availability for those late-season nitrogen applications. Nitrogen stabilizers can help reduce N losses. Surface-applied N will need rainfall or irrigation to place it in the root zone. I would rather you inject your final application of N at V5. There is much less risk for loss than later surface-applied N if an irrigation system isn’t available.
Bultemeier: Today’s economics have each farm operator considering their practices and input costs, along with questioning the 1.25-pounds-per-bushel theory. Several online estimators consider N price and corn price. There are also several paid services that consider soil-type variation, rainfall, irrigation, N-type manure applications and costs to give a recommendation on the amount of N plants need to finish the year. You might shy away from spending extra dollars on them, but these programs take away a good bit of guesswork.
Overstreet: In terms of agronomics, it makes sense to put some N on later. Logistically, is it doable on your farm? Since the plant uses most of the N closer to tasseling, applying closer to that time makes sense. But you also risk not getting that last 50 pounds on, due to weather delays or too many acres to cover.
Bultemeier: After every major rainfall, I get questions about how much N was lost. The answer is, "It depends." By using N modeling systems, you can get an idea of how much was lost in each field by soil type. This can help determine if more, less or no N is needed. It could help you more easily achieve or protect higher yields and optimize input cost of N.
Overstreet: If you look at the cost of N and price of fall corn, the economic optimum rate is at least 180 pounds per acre and could be as high as 230 pounds, depending upon where you live. Below that rate, you could limit yield. Learn more from this update from Purdue.