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OSU Extension, Darke County...
Fall Fertilizer Applications
Justin S Petrosino, Extension Educator
Agriculture & Natural Resources
As
many of Darke County’s fields are
harvested, farmers are now thinking about fall fertilization for next
year’s
crop. Fall is an excellent time for some fertilizer applications but
how the
fertilizer is applied can make a huge difference in your pocket book
and your
environmental footprint.
Before
we discuss fertilizer
placement, fertilizer source, and rates, I will say that all fertilizer
applications should be based on a current soil test for a reasonable
yield
goal. A current soil test refers to a test taken within the past 3
years. A
reasonable yield goal should be arrived at from a field history rather
than a
sales brochure. Some fields can consistently produce 200 bushel corn;
some may
struggle to reach 150.
So
what are the best types of fertilizer
to apply in the fall? The answer is simple, the ones that have the
greatest
chance of being there in the spring! Fall nitrogen applications for
corn can be
made if soil temperatures are below 60 degrees and anhydrous ammonia is
used.
However for fertilizer efficiency and to minimize the chance of
nitrogen loss
through leaching, nitrogen should be applied closer to the time the
crop needs
it. A spring starter application followed by the bulk of the nitrogen
as a
sidedress application before V6 is the optimal way to apply nitrogen
for corn.
Phosphorus
and potassium can be safely
applied in the fall according to a soil test recommendation. The method
of
application depends on the availability of products and equipment.
However
there are a few recommendations that can help keep phosphorus in the
field
whether it is applied as a commercial fertilizer or manure. The first
is to
never apply fertilizer or manure as a broadcast application before a
rainfall
event of a half inch or more. A slow gentle rain can incorporate
broadcasted
fertilizer, but a hard, heavy rain can wash dissolved fertilizer
through a
vegetative buffer strip or to a stand pipe and straight down to a tile
outlet.
A recommended practice is to incorporate the fertilizer immediately
after application.
This can be done through deep banding with strip tillage or
broadcasting and
incorporating with tillage. Once phosphorus is incorporated, unless
certain
conditions exist, it will bind to the soil and remain in the field.
Only if
extremely high phosphorus levels exist in the soil with a high water
table can
phosphorus leach like nitrate nitrogen. Applying according to soil test
recommendation will limit losses in this manner.
There
are still questions floating
around about the impact of glyphosate on nutrient uptake and
availability to
Roundup Ready 2 Yield crops, specifically soybeans. Recently a paper
was
published in the Plant Management Network by several Purdue Field Crop
Specialists entitled, “Glyphosate’s effect upon mineral accumulation in
soybean.”
The research looked at the uptake of macro and micro nutrients by
soybean under
several glyphosate application timings, soybean varieties, and compared
them to
a no-glyphosate control. The summary of the research report is nutrient
uptake
is related to soybean variety and not to the use of glyphosate. The
application
of glyphosate did not cause nutrient deficiency symptoms or decreased
yield.
So
if a nutrient application is on your
agenda this fall apply according to a soil test, check the weather,
incorporate
if at all possible, and choose the right nutrient source. These
principles work
on the farm and in the yard. In the office I receive many soil test
reports and
the highest phosphorus levels typically come from lawns and gardens!
For more
information visit the Agronomic Crops Website at
http://agcrops.osu.edu/ or the
Fertilizer Institute at http://www.tfi.org/.
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