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Fall nitrogen applications
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[OCT.
10, 2003]
URBANA -- As harvest
moves forward across Illinois, many growers will soon be turning
their attention to their fall fertilization plans. Many of those
plans, however, are likely to be impacted by the prospect for higher
nitrogen costs next spring.
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"With higher prices looming, some
growers who have never done it before will be considering a fall
nitrogen application," said Bob Hoeft, soil fertility specialist
with University of Illinois Extension. "While such applications can
be used effectively on many Illinois soils, there are certainly some
locations in the state where a fall application will not be
economical or environmentally safe."
Hoeft notes that a soil test can be
used to determine where lime, phosphorus or potassium is needed.
"Over the past few years, potassium
deficiencies have shown up more often than they should," Hoeft said.
"The deficiency often occurs because growers have neglected to apply
enough potassium to replace the large amount that has been removed
in the high-grain yields of the last few years."
He points out, however, that there is
no soil test available at this time to predict nitrogen needs.
Instead, growers can use a simple formula that is available in the
Agronomy Handbook and other sources.
"It is especially important to take
credit in the formula for homegrown nitrogen," Hoeft said. "Corn
following a legume, such as soybeans, clover or alfalfa, requires
less nitrogen than corn following corn. On a field that receives a
manure application, nitrogen fertilizer can be reduced by an amount
equivalent to that available from the manure."
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article]
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Hoeft adds that fall applications
should not be used on fields that have large areas of standing water
in the spring and early summer or that have had frequent problems
with nitrogen loss in the past.
"Research has shown that soils in the
area south of Route 16 have a much higher risk of nitrogen loss than
those found farther north," he said. "This is due in part to the
higher temperatures in the southern part of the state throughout the
fall and winter. In addition, the soils in southern Illinois tend to
be more poorly drained."
He emphasizes that nitrogen should not
be applied until the soil temperature is below 60 degrees F if a
nitrogen inhibitor is used or below 50 F if it is not used.
"Irrespective of temperature, a fall application should not take
place until the second week of October in northern Illinois or until
the third week of October in the central part of the state," Hoeft
said.
[University
of Illinois news release]
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