The Rural Voice, 1999-05, Page 55Corn fertilizer — how
much?
By Keith Reid
Soil Fertility Specialist
OMAFRA, Walkerton
One question which keeps coming
up again and again is, "how much
fertilizer can I put on with my corn
planter?" The reason for pushing the
fertilizer rate is usually to try to get
over the field with one pass, but this
needs to be balanced off against
meeting the needs of the crop in the
most effective way possible. Too
much fertilizer can hurt yields just as
badly as too little.
Phosphorous is not toxic to the
seedling because it gets tied up so
quickly by the soil, so there is no
practical limit to how much
phosphorous can be applied at
planting. In fact, phosphorous applied
in a band is much more available to
the seedling than broadcast
phos horous, so there is a real
adva tage to applying all of the
phospborus requirements through the
planter. The problems come from the
nitrogen and potassium parts of the
fertilizer.
Both nitrogen and potassium
cause fertilizer burn by increasing
the salt concentration in the soil
solution. If the concentration is too
high, water is pulled out of seeds and
roots, instead of flowing into them.
The result looks like someone singed
the roots with a lit match, leaving
them blackened. In addition, some
nitrogen fertilizers release free
ammonia when they dissolve in the
soil water, which can also injure plant
tissue.
The main factors that affect the
severity of fertilizer burn, or
conversely, the maximum safe rate of
fertilizer to apply, are the distance of
the fertilizer band from the seed row,
and the concentration of fertilizer per
foot of row. Safe rates of fertilizer
placed with the seed are only about
one -twelfth as much as can be placed.
in a band two inches beside and two
inches below the seed, where up to 80
Advice
pounds per acre of nitrogen plus
potash can be applied safely. For
higher rates, the band should be
placed even further away from the
seed row to maintain a margin of
safety. In practical terms, this usually
means splitting the fertilizer into
separate bands. a close one with the
phosphorous and one further away
with the bulk of the nitrogen and
potash.
Concentration per foot of row is
linked with row width, so narrow
rows have higher safe rates per acre
than wide rows. The maximum safe
rate per acre in a 20 -inch row is
double the safe rate in a 40 -inch row,
because there are twice as many feet
of row per acre with the narrower
rows. For more details, refer to the
soil management section of the Field
Crop Recommendations available at
your local OMAFRA Office. The
cost of the publication is $10 plus
GST.O
Take the time to train
new workers
lt� the Ontario Farm Safety
Association
It often seems ditltcult to find.
enough time to instruct new
employees. Yet proper job training is
recognized as being fundamental to
reducing potential for accidents and
injuries in the workplace.
Many seasonal workers ma} he
first-time farm employees. Neter
assume that these people know
exactly
‘% hat is expected of them. Put
yourself in their place — it can be
frustrating and scary to simply he
directed to the workplace. with no
instruction on how to complete a
particular job properly! Following are
a few key points that contribute to
safer working conditions:
• Employees should be made
aware of specific haiards in their
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MAY 1999 51