What is in this article?:
- Micronutrient deficiencies may be cutting into corn yields
- Nutrient availability more complex
• In high-yield systems, it's not just that corn requires more macronutrients like nitrogen and phosphorus — which is what farmers normally think about — more micronutrients are needed as well.
• If you have soil that is deficient in micronutrients, you could be limiting yields."
Nutrient availability more complex
“Nutrient availability is more complex than soil nutrient concentrations," Ciampitti said. "Nutrient availability is also related to the plant's ability to take up each nutrient at the soil-root interface.”
In the second part of a study on how modern corn hybrids (post-1990) absorb and allocate nutrients under contemporary management practices, Vyn and Ciampitti measured how simultaneous increases in the number of plants per acre and nitrogen rates affected the concentration of zinc, copper, iron and manganese in two hybrids of corn.
Vyn said the influence of plant density on the uptake of micronutrients was relatively minor, even at high crowding levels, in that higher plant density resulted in similar yields as medium and low densities. But as nitrogen rates increased, yields rose and corn plants took up a substantially greater amount of micronutrients and allocated more micronutrients to the ears.
"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.
The study was published in AgronomyJournal and can be viewed online at https://dl.sciencesocieties.org/publications/aj/tocs/105/6.