Foliar fertilizing field corn received a positive push when corn prices climbed to all-time highs. Researchers and farmers took a second look at the yield potential from the tactic with the opinion that pushing yields, even if quite small, would pay off.

Then last year exceptionally wet weather had the potential to limit corn yields in some cases, and a foliar nitrogen application made sense to replace a portion of potentially lost nitrogen.

"We knew that nitrogen might have been marginal because of nitrogen loss mechanisms, and it was a year when we would expect responses from late nitrogen applications," said Kelly Nelson, Ph.D., research associate professor, Greenley Research Center, University of Missouri.

It was an excellent year to research the use of mixing a fungicide with various liquid N products for an after-tassel application.

Surprising Results
Nelson expected most of the N and fungicide mixes to have significantly higher yield than the comparisons of only applying the fungicide or the N alone. Foliar N applications or separate fungicide applications were comparable in increasing yields in many cases. Nelson was surprised that really only one mixture containing a lower than maximum rate of nitrogen and a low rate of fungicide resulted in a substantial yield increase that would be economically beneficial. He is further studying this 2008 finding again in 2009 to see if results are repeatable and why it might occur.

Nitamin 30L fertilizer from Georgia-Pacific Plant Nutrition, a blend of methylene urea, urea and triazone, which contains 30 percent N, of which 60 percent is slowly available, was mixed with Headline fungicide. It was 1 gallon per acre of Nitamin 30L tank-mixed with 3 ounces per acre of Headline that increased corn yields by 23 bushels per acre compared to non-treated acres.

"I really expected we would see a higher yield by combining the nitrogen with the fungicide. The logic is that we would expect, in a nitrogen-deficient situation or when plants are showing some deficiencies, that you would have some response to the treatment, but in our high-yield environments, we weren't seeing additional benefit," Nelson said.

Other university data compiled by Helena Chemical has shown its CoRoN product works well on corn in combination with a fungicide applied at VT to R2 stage of growth, but again with a lower rate of N. "We have really good data showing the yield potential increase, above what the fungicide does alone when CoRoN is used as the carrier," said Gary Schmunk, Helena Chemical product manager.

The private and university data compiled by Helena is the justification for more than 20 formulations of CoRoN to use on various specialty crops, row crops, ornamentals and turf. CoRoN is a 25-0-0 controlled release N product specifically for foliar fertilizer (18.8 percent urea N and 6.2 percent water soluble N).

"What we've found in our research is that one to two gallons per acre of CoRoN with a fungicide provides the economical return on investment for corn," Schmunk said.

Adding Micronutrients
Another supporter of foliar fertilizer application to corn is Vatren Jurin, Brandt Consolidated technical director. He also professes the need for using a slow-release N solution to eliminate phytotoxicity concerns. Brandt's N solution for this use is an 80 percent slow-release N triazone-type chemistry based on urea.

Brandt Consolidated is big on including micronutrients in a foliar fertilizer N solution. "Timing is very important if you are going to put micronutrients with a foliar nitrogen solution. If you are working with zinc and manganese, you want to make application in early stages of the corn-V4 to V6. If you want to use boron, you can do it with a fungicide application in the VT to R1 reproduction stages," said Jurin.

Brandt Consolidated's own retail operations and many others they supply have offered foliar N feeding opportunities to their farmers, and Jurin said the company has had good science, data and support behind the practice. The liquid micronutrients have been used extensively, complimenting the foliar feeding.

"The more surface area, the more efficient the foliar application will be," Jurin said. "In row crops, the way you want to apply nitrogen is in combination with micronutrients and pesticides all at the same time."

He is confident in the company's research that shows the boron and the N solution is compatible with a fungicide mix for late-season applications. Again a low volume N content of the mix would be appropriate.

Brandt has developed complexing agents for its liquid micronutrients to assure compatibility with pesticides and uptake by the crop, Jurin said. The challenge in formulating products is to make sure they don't interact to neutralize or render the pesticide useless.

"An example of having to change formulations to keep up with various pesticides is how manufacturers of glyphosate have changed formulations over the years. There was a period when they seemed to be changing formulation every year. That was a challenge because we had to adjust our chemistry to match," Jurin said.

Schmunk also explained the potential for earlier season foliar N application from his company's standpoint. "What's driving the corn market business is that the farmer wants something that is more efficient to apply because standard sidedress nitrogen is only from 30 percent to 70 percent efficient with so much of it being lost from volatizing or leaching or dry weather affecting the availability to the corn."

Even though foliar-applied N is efficient, it is not possible to replace the corn crops total need of pre-season applied or sidedress applied N. Again foliar fertilizing needs to be done in conjunction with a pesticide application using the N solution as the pesticide carrier to be an economical operation.

Nelson stressed his belief that the biggest potential is for late-season foliar feeding in conjunction with a fungicide. At that stage of growth in a high-yielding environment when there is a lot of translocation from the leaves to the ear, there often is potential for a boost in N making a difference. In addition, it is a practical combination of products at a critical time of corn development.

Nelson said, "Usually corn production doesn't justify a foliar fertilizer application unless you have obvious deficiencies, and that's something that I think is key to understand."