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Nebraska: more corn with less nitrogen


Nebraska farmers are using nitrogen fertilizer much more efficiently than they were 30 to 40 years ago.

How efficient? Consider that in the 1970s nitrogen use efficiency was 1.5 to 1.6 pounds per bushel of corn. That’s 1½ pounds of nitrogen per bushel.

Richard Ferguson, University of Nebraska soil fertility specialist, says that figure is twice the nitrogen fertilizer used per bushel in 2010 — 0.84 pound per bushel of corn.

“The average application rate of nitrogen fertilizer has remained basically unchanged for the past 40 years, at approximately 140 pounds per acre,” he says.“ But at the same time, corn production has seen a steady, linear increase in Nebraska over that same period.”

The numbers, according to Ferguson, do not indicate that a bushel of corn requires only 0.84 pound of nitrogen.

“There are other sources of nitrogen besides fertilizer available to the crop, such as mineralized soil organic matter, residual nitrate from previous fertilization, plus credits from legume and manure,” he says.

These other sources contribute to the total nitrogen need for a corn crop of 1.1 to 1.2 pounds per bushel, says Ferguson.

At a glance

Nebraska farmers continue to use nitrogen more efficiently.

Results show rates per acre are steady, but production is higher.

Producers are considering other N sources when determining rates.


He says that farmers are accomplishing this efficiency by accounting for other sources of nitrogen available to the crop, as well as using efficiency-boosting practices that include sidedressing, fertigation, use of nitrification and urease inhibitors, use of slow-release formulations, setting of realistic yield goals and efficient irrigation management.

Nebraska, because of the number of center-pivot systems statewide, has the potential to make even more efficient use of nitrogen through the use of fertigation. Applying nitrogen through pivots enables producers to spoonfeed the crop to meet nitrogen needs when the crop needs it.

UNL’s guidelines on fertilizer use are available in “Fertilizer Suggestions for Corn, EC 117.” To find UNL publications, go online to extension.unl.edu/
publications
.

Specific recommendations for fields using soil test information and cropping history can be calculated using the online resource soiltest.unl.edu.

In 2005, UNL added economic adjustments to its nitrogen fertilizer recommendations, based on the relationship of crop and nitrogen prices.

In 2010, even though fertilizer prices seemed high, the value of the crop, on average, was even higher, resulting in a price ratio of 17:1. To avoid either deficient or excessive rates of nitrogen application, the price ratio range in UNL nitrogen recommendations for corn is confined between 4:1 to 10:1.

“A price ratio above 10:1 could lead to excessive nitrogen rates,” Ferguson says.

He says USDA recently released a report on fertilizer use and prices for corn across the United States. The report was based on the Agricultural Resource Management Survey conducted in 2010. Ferguson used this data, along with crop production data in Nebraska from the Nebraska State Agricultural Statistics Service, to show how efficiently Nebraska farmers use nitrogen for corn production.

Source: UNL CropWatch and interview with Richard Ferguson. Go to cropwatch.unl.edu.

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This article published in the August, 2011 edition of NEBRASKA FARMER.

All rights reserved. Copyright Farm Progress Cos. 2011.