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OSU
Extension
Fall
Fertility and 4-R Fertilizer
Stewardship Reminders
Sam Custer, Extension Educator
The
goals of 4R Nutrient
Stewardship strategies are to maximize economic productivity and limit
offsite
nutrient losses that cost both the grower pocketbook and society.
The
4 R’s include: ‘right’ rate to
meet crop needs and minimize offsite movement, ‘right’ source selected
for
location and timing of application, ‘right’ time based on source and
crop needs
and ‘right’ placement so the nutrients are available to the crop and
stay on
site.
The
4 Rights are interconnected and
work with each other in the overall agronomic production system.
As
we enter the fall, there are a
few reminders of 4R principals to apply:
Determine the right rate of
phosphorus, potassium and lime, by collecting a representative soil
test. The
investment in a representative soil testing program is well worth the
expense.
Once
a rate is determined,
attention needs to be given to source, placement and timing of the
nutrient. In
Ohio, both phosphorous and nitrogen are nutrients that can have offsite
consequences to water quality. They need to be kept in place from an
economic
standpoint for the crop you want to grow. No sense sending dollars down
the
ditch.
Whether
phosphorus is from a
commercial fertilizer or organic source such as manure, broadcast
surface
applications have the greatest risk of offsite movement. In fall 2011,
high
phosphorous levels in tributary water samples seemed to coincide with
periods
where broadcast fertilizer applications occurred followed by rainfall
events.
Shallow incorporation tends to reduce phosphorous losses has been shown
during
rainfall simulator studies. However, caution is warranted to tillage
practices
that increase soil exposure and erosion losses. Alternatives such as
row
starter fertilizer or strip tillage should be considered in erosion
loss
situations.
Ohio
State University does not
recommend fall applied anhydrous ammonia as a preferred method of
nitrogen
application. Years
of field research
shows fall applied anhydrous ammonia can be susceptible to loss and can
result
in significant corn yield decreases
of
as much as 30%, but generally 10-15%.
Shallow, poorly drained soils with
systematic subsurface drainage, cause
fall anhydrous ammonia applications to be risky.
Late winter and early spring warm
weather
periods lead to conditions where ammonium is converted to nitrate via
nitrification. Nitrogen in the form of nitrate can be lost by leaching
(under
cool, excessively wet conditions) or by denitrification (under warm,
excessively wet conditions).
Did
you know that there are 351,000
acres of cropland in Darke County which is the most of any county in
Ohio? Richland
County is number 2 at 295,000 and
Mercer County is third at 293,000 acres.
For
more information visit our web
site at http://darke.osu.edu/ or contact Sam Custer at 937.548.5215.
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