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Identify late-season nutrient deficiency

Corn Watch: Check out these examples of nutrient deficiency symptoms.

Tom J. Bechman, Midwest Crops Editor

September 12, 2023

3 Min Read
Yellowing and browning on corn leaves indicative of a potassium deficiency
POTASSIUM LACKING: Notice the yellowing and even browning along the outside margins of these corn leaves. These leaves were below the ear on respective plants. The symptoms indicate a potassium deficiency. Photos by Tom J. Bechman

Sometimes you don’t need a stalk test right before harvest to determine if your corn plants ran short on nitrogen. Sometimes all you need to know is right before your eyes in visual nitrogen deficiency symptoms. And occasionally, other nutrients are deficient and show up as deficiency symptoms as well.

“We always look at the lower leaves, even when scouting near harvest,” says Dave Nanda, director of genetics for Seed Genetics Direct, sponsor of Corn Watch ’23. “We can learn many things, such as if there was late-season disease pressure. But leaves, especially lower leaves in the canopy, are very good indicators if plants run short on one or more nutrients before achieving physiological maturity at black layer.

“Symptoms of major nutrients are usually clear cut and easy to detect. They often show up on lower leaves in the field first. You don’t know why plants ran short, but you at least know which nutrients were limiting in the plant later in the season.”

Nanda shares advice on how to identify deficiencies of major nutrients:

Nitrogen. A nitrogen deficiency produces the most classic symptoms of all. If corn is short on nitrogen all season, it will likely be stunted and pale in color instead of dark green, and it will produce smaller ears.

If there is sufficient nitrogen most of the season but then it runs short while filling kernels, classic leaf-firing symptoms are likely to appear, first on lower leaves and then, if the deficiency is severe enough, moving up the plant.

“Yellowing begins at the tip of leaves and moves down the midrib, often in a V-shaped or inverted V-shaped pattern,” Nanda explains. “As the deficiency becomes more severe, leaf tissue may die and turn brown.”

classic leaf firing symptoms on a corn leaf

Potassium. Potassium deficiency also causes yellowing and browning of leaves, but it starts along the outside leaf margins at the tip and moves up and down the margins, instead of moving into the midrib, Nanda says.

Here’s how the Purdue Corn and Soybean Field Guide describes the symptoms of potassium deficiency in corn: “Yellowing leaf margins on lower leaves beginning at the tips. Eventually, affected areas turn brown.”

If the potassium deficiency is severe enough, it may also reflect itself in the size and shape of ears, according to the Purdue guide. Ears tend to be small and pointed with poorly filled tips.

view between stalks in a green cornfield

Phosphorus. Phosphorus deficiency reflects itself as stunted dark green to purplish plants. In severe cases, ears may be twisted, with irregular kernel rows and imperfectly developed tips.

“It’s more common to see phosphorus deficiency early in the season, particularly if it is cool and wet,” Nanda says. “There may be enough phosphorus in the soil, but plants can’t get it. After it warms up, plants can take it up, and reddening and purpling often disappear.”

About the Author(s)

Tom J. Bechman

Midwest Crops Editor, Farm Progress

Tom J. Bechman became the Midwest Crops editor at Farm Progress in 2024 after serving as editor of Indiana Prairie Farmer for 23 years. He joined Farm Progress in 1981 as a field editor, first writing stories to help farmers adjust to a difficult harvest after a tough weather year. His goal today is the same — writing stories that help farmers adjust to a changing environment in a profitable manner.

Bechman knows about Indiana agriculture because he grew up on a small dairy farm and worked with young farmers as a vocational agriculture teacher and FFA advisor before joining Farm Progress. He works closely with Purdue University specialists, Indiana Farm Bureau and commodity groups to cover cutting-edge issues affecting farmers. He specializes in writing crop stories with a focus on obtaining the highest and most economical yields possible.

Tom and his wife, Carla, have four children: Allison, Ashley, Daniel and Kayla, plus eight grandchildren. They raise produce for the food pantry and house 4-H animals for the grandkids on their small acreage near Franklin, Ind.

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