Heavy, persistent rainfall across much of the Texas Blacklands this spring has damaged yield potential for corn, but late applications of nitrogen may prevent some loss, says a Texas AgriLife Extension agronomist.

Ronnie Schnell, speaking at the recent Stiles Farm Foundation field Day at Thrall, said denitrification — nitrogen loss from saturated soils — will result in some yield loss. “It’s hard to estimate how much nitrogen loss will occur, but a 2 percent to 5 percent loss per day of saturation is possible if it’s nitrate nitrogen. Most nitrogen we apply turns to nitrate pretty quickly, and is subject to loss.”

He says he’s seen a lot of variability across the region. “I’ve seen some fields with significant nitrogen deficiency, and they will see some yield loss.”

Corn growers may see tips of ears dying back, as well as V-shaped yellowing on the leaves.

Adding more nitrogen, even late in the season, could save some yield, Schnell says. “Corn may be able to take up some nitrogen late. If it’s applied close to tasseling, for instance, we could see benefits.”

He says corn producers typically apply nitrogen at or before planting, then sidedress at the six- to seven-leaf stage. If heavy, persistent rainfall delays that second application and the field loses early nitrogen to denitrification, yield loss is likely.

“If we delay nitrogen application, we may lose 10 percent. But if we don’t put it out at all, we’re looking at a 30 percent yield loss.”

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He says growers are asking which fields are worth making the extra nitrogen application. “Plant size is the key,” he says, “and leaf surface area is the most important factor. If the leaf is able to capture enough sunlight, it may benefit from more nitrogen. If leaf surface is more limited, it may not be beneficial.

“Look at all fields, evaluate the plants, check the cost of nitrogen, determine how much will be needed, and then see if a late application is economical.”