Wheat Topdress Additives

Producers should consider three important management decisions for wheat topdress
applications: nitrogen rate, application time, and nitrogen source. Producers may also have an
interest in considering other wheat topdress issues, such as the use of various additives with their
nitrogen application. Research conducted at Farm Focus in 2003 addresses the use of various
products with nitrogen topdress for wheat. A brief discussion for each of these research products
is presented below:
Addition of Copper
The objective of this study is to evaluate yield response of wheat to the addition of copper in a
spring nitrogen topdress application. The treatments were 60 lb./acre nitrogen topdress using
28% UAN, and 60 lb./acre nitrogen topdress using 28% UAN plus 1 qt./acre Krystal Klear Cu (5%
chelated copper). These two treatments were replicated three times and broadcast applied on
April 2, 2003. Results from this single year study indicate no significant differences between the
two treatments for moisture or yield.
Evaluation of Nitrogen Rate and Sulfur
The objective of this study is to evaluate yield response of wheat to two different nitrogen
topdress rates and the addition of sulfur in a spring topdress application. The treatments were 60
lb./acre nitrogen, 60 lb./acre nitrogen with 20 lb./acre sulfur, 90 lb./acre nitrogen, and 90 lb./acre
nitrogen with 20 lb./acre sulfur. The nitrogen only treatments were applied using 28% UAN liquid
fertilizer. The treatments with sulfur had THIO-SUL (26% sulfur solution, 2.87 lb. sulfur/gallon)
added at a rate of 7 gallons per acre, and the amounts of 28% UAN were adjusted to compensate
for the nitrogen available in THIO-SUL. These four treatments were replicated four times and
broadcast applied on April 2, 2003. Results from this one-year study indicate that the additional
30 lb./acre nitrogen significantly increased wheat yields. Based on the yield differences from this
trial, it would appear the sulfur did improve nitrogen efficiency at the lower nitrogen rate of
application, but had no effect on the higher 90 lb./acre nitrogen application rate.
Evaluation of Nitrogen Rate and Super N
The objective of this study is to evaluate yield response of wheat to two different nitrogen
topdress rates and the addition of Agrotain Super N. The treatments were 60 lb./acre nitrogen, 60
lb./acre nitrogen plus Super N, and 90 lb./acre nitrogen. The nitrogen source for the three
treatments was 28% UAN liquid fertilizer. Super N was added at the rate of 3.25 gallons/ton of
28% UAN fertilizer to the 60 lb./acre nitrogen rate. Super N was not added to the higher nitrogen
rate due to space limitations in the trial. These three treatments were replicated three times and
broadcast applied on April 2, 2003. Results from this one-year study indicate that the additional
30 lb./acre nitrogen significantly increased wheat yields. The results did not indicate a statistically
significant yield increase from the addition of Super N to the lower rate of nitrogen.
All wheat research trials mentioned above received 250 lb./acre 11-26-15-6S broadcast at
planting. Plots were planted with a John Deere 750 no-till drill on September 30, 2002 at a
seeding rate of 150 lb./acre and harvested July 14-16, 2003. For complete details on the above
wheat research trials (including yield data, moisture data, and harvest populations) visit
http://www.farmfocusshow.com/research.htm and click on 2003 ‘Table of Contents’.

Source : http://vanwert.osu.edu/ag/article%20archives/2004/Wheat%20Topdress%20Additives.pdf