The Rural Voice, 2003-05, Page 51t
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Ag News
Fine-tuning application good nitrate management
By Janice Becker
Nitrate management was at the top
of the agenda when Greg Stewart of
OMAF spoke at the Huron County
Soil and Crop Improvement
Association crop update meeting in
Blyth in April.
Good nitrate management is about
fine tuning applications and
determining the optimum quantity,
he told the crowd gathered.
Focusing on the relationship
between the nitrate rate per acre and
the bushels per acre yield, generally
for corn, Stewart said the maximum
yield rate often does not correspond
with the maximum economic benefit.
"1t is usually back a bit on the
graph. On a test, 30 pounds more of
nitrates only added three more
bushels of corn."
In determining the efficient use of
nitrates, Stewart said the numbers
will vary depending on the field, the
price of corn and the cost for
nitrogen.
"Three bushels of corn at a price of
$3.33 per bushel would ring in an
extra $10. But, if the price of
nitrogen went to 40 cents, 30 pounds
would cost $12 thereby creating a
loss of $2. However, if the price were
30 cents, there would be a $1 gain."
Stewart said the price ratio for
which one should aim is five, such
as when the nitrogen cost is 30 cents
per pound and the corn price is six
cents per pound.
Farmers should be conscious of
that ratio because if it rises to seven,
the amount of nitrogen applied
should be reduced.
When deciding where to start with
nitrate applications, Stewart
suggested looking at general
recommendations compiled by
OMAF, NMAN (a nutrient
management software program) or
the product requirements. According
to studies, Huron County could fit
into two categories which could
dramatically alter the rates.
Some would categorize the region
as southwest, any region west of
Toronto which has more than 2,800
heat units, and compare cropping
results to those done in Ridgetown.
Others would use Elora numbers,
west -central, which has less than
2,800 heat units, but also requires
considerably less nitrogen, said
Stewart.
To achieve a 128- bushel -per -acre
yield in the southwest, 167 lbs of
nitrogen was utilized while only 108
were needed in the west -central.
The Ridgetown site also showed a
distinct advantage with side -dressing
rather than pre -plant, he said.
These trials were all in corn -after -
corn situations and there were no
considerations given to no -till.
Stewart said the regional
recommendations used can also
impact the amount of nitrogen
allowable as the Southwest starts
with higher levels and credits for
manure and/or previous crops are
deducted.
If the recommendation is 165 lbs,
of nitrates with a 40 lb. credit for red
clover and 30 for solid manure, the
farmer would still be allowed to
apply 95 lbs. However, lower starting
levels for the West -Central region
would reduce the rate to almost no
additional applications.
Farmers must also take into
consideration residual nitrates in the
soil and ask if the credits are correct,
said Stewart.
The best way to evaluate is with a
soil test at the appropriate time of
year. These test would then override
the general recommendations.
Testing can also help farmers better
manage nitrates as the soil's
requirements can also vary yearly
depending on inputs from previous
crops and manure, weather and with
location in each field.
Nitrate levels increase with heating
so a cool summer would result in a
slower release and lower overall
total.
A warm, dry spring would leave
high residual levels in the soil on
June 1 (the optimum testing date)
because there had been more released
and little leaching.
"You can only find this with
testing," said Stewart.
Though admitting imperfections in
soil testing, he said, in his opinion, it
will give "pretty good direction 70
per cent of the time. It gives guidance
to move up or back."
Stewart included a few tips to
improve the accuracy of testing. A
12 -inch core sample, done in one
strip, should be taken pre -side -
dressing and not in a starter fertilizer
band if pre -plant applied. The sample
should not be stored on the vehicle
dashboard as nitrates increase with
heat.
The turn -around time on samples is
usually a couple days.
Questioned on the validity of
putting so much emphasis on nitrates
when other factors could effect yield,
Stewart noted that this would
eliminate nitrogen as a limiting factor
though it would not stop other
nutrients from having an impact.
In response to an inquiry about
applying all the nitrogen either in
pre -plant or during planting, Stewart
said the farmer would then miss the
opportunity to adjust the rate
afforded by side -dressing after
testing on June 1. "A guess on May I
would be too high while a June test
could show that no side -dressing is
needed."
While encouraging farmers to cut
their nitrogen applications, Stewart
stressed that this brings with it a need
for more accuracy and efficiency as
there is less room for error.
It is hoped work will be done this
season to look at the impact of other
criteria such as organic matter, to
adjust the general recommendations
currently in use.0
4-H leadership
conference planned
Providing young people the
opportunity to develop their
communication and leadership skills
will be the emphasis of the one day
workshop called "Leap into
Leadership" being held Saturday,
May 3, at the Western Fairgrounds,
London.
"Dare to Care" is the title of the
feature speech by Andrew
Thibodeau, London, who has
provided 10 years of inspirational
speeches on student leadership,
across North America.
Continued on page 48
MAY 2003 47