High N rates increase micronutrient uptake

“From a human nutrition viewpoint, there’s always a concern that increasing yields will dilute the nutritional quality of corn,” Vyn said. “But as long as soil concentrations of nutrients are sufficient, higher yields tend to mean more micronutrients are concentrated in the grain, not less.”

But higher corn yields mean more micronutrients leave the field at harvest.

“Growers are not used to thinking about how much zinc leaves the field when they harvest grain corn,” Vyn said. “But that’s part of the management equation that has to be considered.”

At high plant density (42,000 plants per acre) and high nitrogen rates (200 pounds per acre), 58 percent of zinc taken up by corn hybrids was removed in the grain, compared with 31 percent of copper, 18 percent of iron and 15 percent of manganese.

Vyn and Ciampitti also observed differences in when micronutrients are absorbed and where they are stored in the corn plant. Zinc is taken up throughout the season and is primarily stored in the stems during the vegetative stage, while iron is allocated to the leaves. Copper and manganese are distributed to both leaves and stems and are taken up mostly before the flowering period.

To prevent deficiencies, Vyn suggests growers add zinc to bulk fertilizer with phosphorus – which has a similar uptake pattern – or put it in a starter, while manganese can be supplied in a foliar application where necessary. Growers usually can rely on soil for sufficient levels of iron and copper, he said.

Further research will concentrate on developing estimates for micronutrient requirements to help inform growers which kinds of fertilizers to apply and when.

“There’s no question that when you have more biomass and higher grain yields, you require more of certain micronutrients,” Vyn said. “It’s something to be aware of.”

Funding for the study was provided by Dow AgroSciences, the U.S. Department of Agriculture, the Purdue Bilsland Dissertation Fellowship, Potash Corp. and The Mosaic Co.