Seeing 35 units of nitrogen disappear from saturated fields takes a lot of the excitement out of $5/bu. corn for Hartwell Huddleston, Leland, MS. Timely growing-season applications are essential to prevent further cuts into the crop's marketplace allure.

Nitrogen (N) loss can occur through several methods including volatility, leaching and denitrification. Mississippi growers often experience N loss resulting from denitrification when wet weather persists after N application. This problem is more prevalent on heavy or fine-textured clay soils.

These soils are prone to remain saturated, causing denitrification when microorganisms turn nitrate N into N gas that escapes into the air, says Erick Larson, grain crops agronomist, Mississippi State University (MSU) Extension, Starkville.

“Warm soil temperatures accelerate this process,” he says. “Rates range from 2% to 3%/day at soil temperatures from 55° to 65° F, or 4-5%/ day if soil temperatures exceed 65°.”

Huddleston farms along the Mississippi River Delta. Like many growers, he has increased corn and soybean production and cut back on cotton. He strives for 220-bu. corn under irrigation in an area that often faces long, hot, dry spells in late summer.

But he can also face horrific rain episodes, like several last spring (2008) that caused the big river to swell over flood stage. “It's hard to believe, but we actually had water shooting up out of some wells (on river-bottom land),” he says.

He regularly pencils in 220-230 units of N to secure a 200-bu. yield, using the 1-lb.-N/bu. yield theory. But after an abnormal 14 in. of rain in July 2007, he figures about 35 N units escaped from the soil.

“My corn averaged 195 bu., so we may have lost at least 35 units in 2007,” says Huddleston, who farms with his brother William and father Herbert. “The ears just didn't fill out.”

At a nearly unbearable cost of about $130/acre for a 220-230-unit application, 35 lost units meant $15-20 went straight down the drain. He knows he can't do much about lost N when whopping downpours strike, creating super saturation. But, he is attempting to make applications more timely and efficient.

“I usually apply 100 units at planting,” says Huddleston. “It's knifed in. More N is applied after a good stand is established.

“I decided to ‘fly on’ more N at the tassel stage. It should provide more timely nutrients for the corn, but it's expensive.”