Agronomy Update May 2019
Posted on May 23, 2019
By Dave Dyson, Agronomist
The rain just keeps on coming and delaying corn planting in the majority of the Corn Belt. As the 2019 planting date moves further back into May, you may be looking for ways to reduce wait times before planting. I fielded many calls this past week about changing nitrogen sources for pre-plant. As the options for pre-plant nitrogen are tightening up, I’ll be highlighting the benefits and drawbacks of different sources of nitrogen, as well as ways to overcome these challenges.
Anhydrous ammonia (NH3) is a widely used form of nitrogen in the Corn Belt, especially for pre-plant application. The importance of NH3 includes the fact that this source of nitrogen (N) is by far the most concentrated, with 82% N. It can be applied long before the crop is planted, including in the fall, when other N sources are susceptible to loss. Also, it normally is a less expensive source of N. The conversion of ammonia to ammonium creates a temporary alkaline condition in the ammonia retention zone, typically as an oval 2 to 5 inches in diameter around the application area. Since the pH will be elevated, waiting 5-7 days before planting will ensure the risk of seedling injury is reduced. The problem comes when no NH3 has been applied and the calendar is May 13th.
I recommend putting the corn seed into the ground as soon as the soil conditions permit, but this may leave some of you with a major decision. You now have to choose to delay your nitrogen (NH3) application until sidedress time, V3-V6, or change your source of nitrogen for the 2019 crop season. If you decide to change your source of nitrogen, you will have to choose between urea and urea-ammonium nitrate (UAN). The main drawback with urea is with application. Urea is a dry material, so an additional application pass will have to be performed to apply this product. In addition, if applying urea with a spinner spreader you will have to “double spread” the product to increase the chances of an even application, doubling your application time. Soon after urea is applied to the soil, it changes to NH3 either chemically or by the enzyme urease, and then to NH4. If the urea is not incorporated, loss from volatilization can be substantial (figure 1).
Figure 1: This graphic from Taurus Ag shows the urea cycle in the soil and how easily urea can be diverted away from the targeted crop.
If you are considering changing your nitrogen source away from NH3, I would strongly encourage moving toward UAN. UAN is a liquid and can be applied at the same time as the herbicide, saving a pass and increasing the efficiency of your application. A big drawback with surface application of UAN is the risk that some of the urea portion of UAN will volatilize off. To ensure the UAN stays in the root zone and does not volatilize or leach away, I recommend using 1 gal/ac of UltraMate® Zn with your UAN application. UltraMate Zn is The Andersons’ liquid humic acid and will carbon chelate the UAN, preventing the nitrogen from leaving the cropping system, while also providing 1 qt/ac of Nulex® 15% Zinc to the corn crop.
In conclusion, UltraMate Zn is a carbon product that stabilizes nitrogen, reducing volatility and leaching while promoting soil microorganisms. By limiting the loss of nitrogen from the cropping system, the environment is protected and yield is increased.
By Jessica Stacy, Product Specialist
Last year, UltraMate LQ was tested with a surface application of UAN, figure 2, and the results speak for themselves. The below graph shows the average of a replicated 28% nitrogen study outside of Walton, IN. The replications that were treated with 1 gal/ac of UltraMate LQ yielded 10.63 bu/ac more than the replications that only had 28% applied.
When UltraMate LQ was applied sidedress at a rate of 1 gal/ac with 160 units of UAN, an average advantage of 7.95 bu/ac was observed compared to the replications treated with 160 units of UAN alone. This study was conducted in Southern Illinois and Iowa by Beck’s Practical Farm Research in 2017.
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