Nick Constant decided to try foliar micronutrient applications on the family's corn and soybeans five years ago after seeing company field trials near their Williamsville, Ill., farm show that they might pick up a few bushels.

"We don't have any nutrient deficiencies, but the yield data indicated we would see a return on our investment," says Constant, who farms with his father Bruce.

Over the last five seasons, he’s seen an average gain of 2-3 bu./acre in soybeans and 4-5 bu./acre in corn with micronutrient use in their all non-biotech soybeans and biotech corn. They apply a product called Brandt Smart Trio that includes zinc (Zn), manganese and boron in a post-foliar spray tank-mixed with glyphosate in corn and Flexstar/Fusion in soybeans.

"The herbicide application in the soybeans causes some leaf burn," he says. “The micronutrient application seems to help the soybeans come out of it (leaf burn) sooner. It more than covers our costs. I think micronutrients help the glyphosate formulation in corn work better."

New micronutrient options

Using micronutrients to relieve stressors is gaining popularity in some circles, given high commodity prices.

Julian Smith, domestic sales director with Brandt, a Springfield, Ill.-based micronutrient supplier, says company and third-party researchdemonstrates that farmers should be willing to think outside the box and evaluate micronutrient use. Brandt manufactures several micronutrient products, including the Smart System line of foliar micronutrients.

"Micronutrients are becoming an important resource for traditional and non-traditional protocols. We find that micronutrients can be used as physiological tools that can assist gene expression, not just solve the traditional zinc deficiencies in corn and manganese deficiencies in soybeans," Smith says. "Micronutrients can be part of a season-long strategy for efficient nutrient management."

When micronutrients are applied with herbicides, fungicides and insecticides, Smith says Brandt’s research shows that mineral content in corn and soybeans is altered and may increase element availability. For example, some say that higher iron levels may help soybeans manage disease stress.

Ray Schneider, soybean plant pathologist with Louisiana State University (LSU), has researched the effects of minor element nutrition on soybean diseases, including iron. His work to date focuses on Cercospora blight, the biggest disease problem in many southern states, and a close relative to frogeye leaf spot.

"In general, micronutrient use and effectiveness depends on the disease and the element. We see large effects with iron in southern soybeans affected by Cercospora," he says. "The Cercospora pathogen produces a toxin and causes severe defoliation in soybeans. We have found in field trials that iron inhibits production of the toxin and controls the disease."

Iron works with the fungus physiology, not the soybean physiology, Schneider says. "We apply iron as a foliar spray at first flower, before any disease symptoms are present. Our soybean yield measurements indicate an increase in yield over non-treated plots, but we need another year of the research before we will report results. This is a new vein of research to explore these mechanisms and their effects in various crops."

Micronutrient deficiency uses

Micronutrient applications remain a sound strategy where deficiencies may exist. University plant pathologists and soil fertility specialists both urge farmers to monitor fields with a prior history of nutrient deficiencies and perform soil or tissue tests for confirmation.

"Soil conditions like compaction will limit manganese availability, high phosphorus (P) levels limit zinc availability, and high (soil) organic matter often limits copper," says Brandt’s Smith. "We find zinc use in corn can help with phosphate deficiency, root development and early growth. Manganese applied to soybeans is useful for photosynthesis, pest resistance and energy production."

Micronutrients are essential for plants to complete life cycles, says Fabian Fernandez, University of Illinois soil fertility specialist, "just as important as N, P and K. But whether or not micronutrients need to be added to individual fields or even parts of fields is open for discussion. Deficiencies are not common and often are related to soil type."

While Fernandez says Zn may help with germination, he does not see much response in yield from general Zn applications. Upper Midwest farmers with low organic matter or sandy soils or very high P levels from common inorganic fertilizer applications may see the most response, he says.

"Just as with other nutrients, when a micronutrient is deficient you will be able to tell by looking at the crop. Those are fields I would treat with the nutrient that is a problem," he says. "I also would apply micronutrients if I am interested in seeing the potential for a response, on a trial basis only, having strips with and without the micronutrient applied."

Dan Kaiser, University of Minnesota Extension soil scientist, concurs. He recommends soil sampling and a Zn soil test where there may be indication of potential problems in cornfields.

Iron deficiencies are common in soybeans grown west of the Mississippi River, Kaiser and Fernandez say. Manganese deficiencies are more common east of the river; high-pH soils are the trigger, experts say.

"I find it hard to recommend manganese applications in soybeans. We see no clear or consistent responses to micronutrient use," he says. "We have research looking at the uptake of nutrients and how the various elements are related. But for now, we do not see many deficiencies, so farmers do not need much in the way of micronutrients. I suggest interested farmers look at on-farm micronutrient test strips and see if it returns for your operation.