Use Nitrogen More Efficiently To Get Maximum Results
OWENSBORO, KY.
With the high cost of nitrogen fertilizer,
farmers need to get optimum use of the
product. Reviewing their management
plan and making needed changes can potentially
save money without compromising yield.
Most recent research shows it takes about
three quarters of a pound of nitrogen per bushel
to reach corn’s maximum yield potential, but
some producers use much higher rates, said
John Grove, University of Kentucky College of
Agriculture soil and crop management specialist.
With today’s high cost of nitrogen, using it
more efficiently, and thereby lowering rates, can
have a major impact on profitability.
UK has been using corn-nitrogen trial data for
more than 50 years to determine rates to recommend
to Kentucky growers. As a result of
these long term trials, Grove said UK researchers
know that tillage, soil drainage, previous
crop, winter field cover and timing of
nitrogen applications make a difference in nitrogen
need. There are other factors in individual
fields that can affect a crop’s ability to take
up nitrogen, including stand problems, root development
problems and water availability. Understanding
these factors in their fields will help
farmers determine their nitrogen needs.
Grove said, in his experience, 10 to 25 percent
of farmers in any given area are using more nitrogen
than necessary. That represents a serious
opportunity for efficiency improvement, he
said.
“I’ve actually heard producers say, ‘I know
that field has a problem so I’m going to give it an
extra 25 units of nitrogen and snap it out of it.’
Well, you’re not,” he said. “That nitrogen is not
going to be able to snap that crop out of a compaction
or soil structure problem. It’s not going
to help you when you’re not in an optimal crop
rotation. It’s not going to make up for genetics
or the fact that your plant population is above
or below what that soil will support.”
If drainage is a problem or there is substantial
residue from a previous crop, then the
farmer will want to look at ways to reduce loss
of nitrogen into the air through denitrification
or volatilization.
Placing nitrogen in the soil beside the rows
can reduce the likelihood of both volatilization
and immobilization, therefore reducing the need
to use higher nitrogen rates. Timing of the application
also plays a role. The optimal timing
depends on when the crop is planted, expected
crop development and soil wetness.
Well drained soils offer the greatest flexibility
but give the least response to delayed application
or split applications, Grove said. Therefore,
nitrogen can be applied prior to planting or via
side dressing (placing it beside the row when
corn is 4 to 8 inches tall) with little effect on
yield.
Poorly and somewhat poorly drained soils offer
the least flexibility because they give the most
response to delayed and split applications. The
nitrogen loss problem with these soils is denitrification,
so applications prior to planting and
at planting offer the greatest potential for this
loss. Delaying application until the crop is growing
offers the best chance of getting the nitrogen
to the plant when it needs it. With pre-plant
and at-plant applications, it is also important to
consider using a product containing a nitrification
inhibitor as these reduce denitrification
loss potential on the wettest soils if side dressing
is not possible, he said.
“If you’ve got some wet fields you should be
side dressing at least two-thirds of your nitrogen
on these,” Grove said. “If you do that you
can reduce your total nitrogen rate by 35
pounds per acre. So, on your wettest 1,000
acres of corn ground, with a nitrogen cost of
$0.40 per pound, you’ll save about $14,000.”
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