Nitrogen key to corn's uptake of other nutrients

Nitrogen key to corn's uptake of other nutrients

Study shows new corn hybrids take up more nitrogen and micronutrients from soil than hybrids planted before 1990.

MODERN corn hybrids use more nitrogen and micronutrients than older hybrids, according to a new Purdue University study.

While studying the timing of nutrient uptake in corn and how that process affects yield; Purdue agronomy professor Tony Vyn and Kansas State University associate professor Ignacio Ciampitti determined that post-1990 corn plants increased nitrogen intake from the soil by 27% during the flowering stage compared to pre-1990 corn plants. The research also showed that nitrogen uptake after flowering in modern hybrids averaged 56% of the total grain nitrogen at the end of the season.

The increased grain nitrogen came primarily from new nitrogen uptake from soil during grain filling, as opposed to nitrogen being remobilized from plant leaves and stems. The higher amount and duration of nitrogen uptake contributed to superior grain yields even as actual grain nitrogen concentrations declined.

The timing of nitrogen uptake can affect the corn plant's abilities to absorb other plant nutrients. Optimum nitrogen levels increased the plant's abilities to absorb phosphorus, potassium and sulfur, Vyn explained.

"You need to think in terms of nutrient balance. If you have a plant with more biomass and more yield, it will be taking up more nutrients in a balanced manner that shifts with plant needs and growth stages," Ciampitti said.

Because modern corn hybrids use nitrogen more efficiently, they will also increase uptake of other nutrients.

"At some point, (corn producers will) need to increase the amount of these other nutrients applied to their fields as yields continue to increase," Vyn said.

Growers may need to use fertilizers to meet the increased nutrient requirements, including micronutrients, of hybrid corn in high-yield systems.

In the second stage of the research project, 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. The study demonstrated that today's corn plants also take up more micronutrients.

"This study raises the question of whether we need to pay more attention to micronutrients in fertilizer management," Vyn said. "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 your yields."

Growers often overlook the crucial role micronutrients play in optimum plant growth and reproductive development, Vyn said. They often assume that the soil nutrient concentrations for these micronutrients are sufficient.

"For many years, we didn't have to worry about micronutrients, but if you're in a cash crop situation where you're producing bigger plants and more grain, you are exporting more micronutrients away from the field at harvest," he said. "If you're not replacing them, the soil is going to be depleted over time."

Producing higher-yielding corn means more micronutrients will leave the field at harvest time.

Based on the study, corn hybrids at a high plant density of 42,000 plants per acre and nitrogen rate of 200 lb. per acre utilized 58% of the zinc, 31% of the copper, 18% of the iron and 15% of the manganese in the soil.

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

Vyn and Ciampitti also observed the difference in when micronutrients are absorbed and where they are stored in the corn plant. For instance, the corn plant takes up zinc throughout the season but stores it in the stem during the vegetative stage, while iron is allocated to the leaves. Before the flowering period, copper and manganese are taken up and distributed to both the leaves and stems of the corn plant.

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

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

Volume:85 Issue:47

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