Update from the Field: Don’t Guess, PSNT
Posted by Dave Dyson, Agronomist on June 09, 2020
As the torrential rains dissipate and the ground starts to slowly dry out, it is time to think about sidedressing corn with nitrogen. The 18 states that planted 91% of the 2019 corn acreage saw an earlier planting season this year; not as early as 2012, but earlier than normal, Figure 1. That has translated into corn emergence moving ahead of the five-year average. The corn that was planted around April 20 is now approaching V4, the optimal time to start thinking about performing the Pre Sidedress Nitrate Test (PSNT).
Figure 1: These two charts represent 2020 planting progress compared to the five year average. https://downloads.usda.library.cornell.edu/usda-esmis/files/8336h188j/9c67x7852/8910kd63p/prog2220.pdf and http://www.thecropsite.com/reports/?id=509
Performing a PSNT will provide a snapshot of how much nitrate is available in the soil at the time the soil test was pulled. This test is accurate, but the values will change with the next rain event, so it is essential to perform these tests within a week of side-dressing, Figure 2. Once results from the PSNT are received, the nitrate value can be used to determine how much nitrogen will be needed to apply to the corn crop. All states have different guidelines, but most recommend 25ppm of nitrate to provide the corn crop adequate nutrition until harvest.
Figure 2: This picture was taken 5/26/20 near Walton, Indiana, and shows a field with V2 corn. The producer applied manure on this field during the winter months and is wondering if additional nitrogen is needed. Pulling a PSNT seven days prior to a sidedress application will give a snapshot picture of how much nitrogen is out in the field.
There are three main sidedress options for applying a liquid nitrogen fertilizer on a corn crop. The first is Y-drops, flexible tubes that can either be fitted on a toolbar or high clearance sprayer. The Y-drops are usually the fastest form of sidedress application because there is no soil contact. The Y-drops run on top of the ground, directing the liquid nitrogen solution to the base of the plant. This can be beneficial by applying the nitrogen solution close to the plant, while not burning the corn plant’s tissue. The biggest drawback to Y-drop application is this process leaves the nitrogen unincorporated by soil and susceptible to both volatilization and leaching.
The second sidedress option is using a rolling coulter. The rolling coulter can be fitted onto a toolbar or some high clearance sprayers. The coulter cuts a groove into the soil, and an injector is mounted behind to spray a stream of nitrogen into the groove. This method is slower than the Y-drops but will cover most of the nitrogen solution with soil, protecting the nitrogen from loss due to volatilization.
The third option for sidedress is to bury the nitrogen solution 4-6 inches below the ground with a knife attached to a toolbar. This option is the slowest to apply in the field but will prevent volatilization.
Regardless of the application method, nitrogen leaching out of the root zone is always a risk. The excessive rain events that usually happen after sidedress is over, around the 4th of July, can move nitrogen out of the reach of the crop’s roots and may move the nitrogen down into the tile ditches and cause water pollution. To mediate this risk, using a product such as UltraMate® LQ or UltraMate Zn will protect the nitrogen from volatilization and leaching. UltraMate LQ and UltraMate Zn contain 12% humic acid and 4% fulvic acid. Humic acids sequester metals, including nickel. Without nickel, urease enzymes cannot function as they require nickel to survive; with no active urease in the soil, the urea portion of UAN will be protected from being converted to ammonia by urease activity, thereby preventing the urea from volatilizing. The humic and fulvic acid will complex the nitrogen molecules, preventing the nitrate in the UAN from leaching out of the root zone. Carbon chelating the nitrogen will make the corn plants more efficiently take up the nitrogen, Figure 3.
Figure 3: This picture was taken 5/26/20 near Walton, Indiana, and shows a field with V2 corn. The producer applied manure on this field during the winter months and is wondering if additional nitrogen is needed. Pulling a PSNT seven days prior to a sidedress application will give a snapshot picture of how much nitrogen is out in the field.
In conclusion, there are many considerations as sidedress season approaches. First, perform a PSNT to determine how much nitrogen should be applied to the corn crop. Second, consider the various application methods to determine which is right for your operation. Third, add UltraMate LQ or UltraMate Zn to your sidedress application to reduce volatilization and leaching. Contact your local sales representative from The Andersons for more information about PSNTs and UltraMate LQ or UltraMate Zn.
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Dave Dyson is a regional agronomist for The Andersons’ Farm Centers which are located throughout Ohio, Michigan, and Indiana. He is an Indiana native and grew up on a dairy farm in Miami County. A graduate of Purdue University with a degree in Crop & Soil Science, Dave has a deep knowledge of various agronomic topics and is committed to helping growers improve their crops. If you have any questions, Dave can be reached at david_dyson@andersonsinc.com.
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