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Nitrogen rates
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By John
Fulton
[NOV. 15, 2005]
The wonderful fall weather and the threat of
greatly increased spring prices have led to a large amount of
nitrogen being applied this fall. Of course there are several
thousand acres of spring applications already planned, so here is a
synopsis of the new university guidelines regarding nitrogen rates
at current nitrogen costs.
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There are separate ranges for corn following soybeans and corn
following corn. A soybean nitrogen credit will no longer be
subtracted from the recommendation but is included in the
corn-following-soybean numbers.
Using a corn price of $2 per bushel and a nitrogen price of
30 cents per pound (anhydrous ammonia at $492 per ton), the
recommended range of nitrogen applied for corn after soybeans is
122 to 162 pounds per acre. For the same price scenarios, the
corn-after-corn recommended range is 137 to 174 pounds per acre.
The midrange nitrogen application amount is based on about
148-bushel yields. Take the difference in planned yield from 148
and multiply by 0.4 to get the different amount of nitrogen to
apply from the midpoint. The midpoint would be 156 pounds in
corn after corn. An expected yield of 180 would mean 180-148=32.
Then 32x0.4=13 additional pounds from the midpoint. The total
would be 156+13=169 pounds of N in corn after corn for an
anticipated 180-bushel yield.
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These recommendations fluctuate depending on the corn price and the
nitrogen price. Corn price looks to be fairly stable in that $2
area, due to the government loan rate. To adjust for N price, the
entire range is decreased by 10 pounds when the nitrogen price
increases by 6 cents per pound (about $100 per ton in ammonia cost).
With spring prices forecast in the $600-per-ton range, this may well
mean the corn-after-soybean range will be about 112 to 152 and the
corn-after-corn range 127 to 164.
These figures are from over 250 Illinois trials. Of course, they
didn't all perform perfectly. Some fields varied from these figures,
and your fields may also. The main point is that high-priced
nitrogen and low-priced corn means you should probably apply less
nitrogen to maximize your income. Gone are the days when 200-pound
applications to maximize yield are the norm. Instead, we're trying
to maximize returns on the investment.
[John
Fulton, unit leader,
University of Illinois Extension,
Logan County Unit]
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