Deficiency ID: Minimizing the Impact of Nutrient Deficiencies

Midseason scouting is a best management practice engaged in by every farmer who wants to pursue the best possible outcomes for his production, year-in and year-out.

When you go into a field and find a problem this time of year, you’ve already lost bushels. But in areas where crops aren’t getting proper nutrition, for one reason or another, a rescue application of the right nutrient can still help limit the loss, according to Mosaic agronomist Dr. Matt Clover. The key is knowing what to look for, and recognizing the symptoms unique to each particular deficiency.

Discoloration is often the first sign to catch the eye.

“If you go out in the field and notice the plant leaves are beginning to look chlorotic, which is a yellowing of the leaves, or even necrotic, which is a dead area of tissue that can form — those are signs that something is wrong and needs to be taken care of,” Clover says.

But look more closely, and each nutrient shows its own particular symptoms.

“When you look at the big three — nitrogen, phosphorus and potassium — all of their nutrient deficiency symptoms will show up first in the lower leaves of the plant,” explains Clover. “These nutrients are mobile within the plant. If the plant is in a deficiency situation and can’t get nutrients from the soil, the plant has the ability to take those nutrients from the lower leaves, and redistribute them up to the new growth in the upper leaves, where the plant is actually growing.”

But how do you tell nitrogen deficiency from a lack of phosphorus or potassium?

“For nitrogen, typically you will see yellowing starting on those lower leaves, from the midrib in corn, and working its way outward on the leaf. It looks like a lack of chlorophyll — turning light green to yellow,” Clover says. “Phosphorus is a little different. There can be multiple symptoms. Early on, it can stunt plant growth, and it can also be seen in purpling of the leaf. The purpling is actually an accumulation of anthocyanin within the plant leaves.”

“Potassium deficiency can look a lot like nitrogen deficiency, except that it starts on the outer leaf margins and works its way in,” says Clover. “The coloring is very similar [to nitrogen deficiency]; you have chlorosis, which is yellowing, or even necrosis — the dead spots. Unlike nitrogen, this condition first appears on the outside margins of the leaf and works its way in.”

Though hidden deficiencies in the soil can cause these problems, weather is another main culprit that prevents plants from getting the food they need from the soil. Both flood and drought can disrupt the flow of nutrients. Taking account of weather conditions is important, both for rescue applications and going forward, to understand what modifications need to be made to the long-term nutrient management plan.

“This year is a perfect example of weather-related deficiency,” Clover says. “I am in Illinois, and I just checked yesterday — we have had 15 inches of rain since the first of June, and most of that has come in the last two weeks. So the plants around here are showing yellowing symptoms, and in some cases, showing necrosis from the waterlogged conditions. Too much water can inhibit the plants’ ability to take up nutrients. Sometimes, too much water can look like nitrogen deficiency because the water prevents the plant from taking up the nitrogen it needs.”

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