HomeMy WebLinkAboutFarming '90, 1990-03-21, Page 29FARMING ‘90, WEDNESDAY, MARCH 21, 1990. B13.
Watching nitrogen efficiency under a conservation system
BY BRENT KENNEDY
SENIOR SOIL CONSERVATION
ADVISOR FOR
HURON COUNTY
The principal differences in com
paring a conventional system with
a conservation system is the degree
of inversion and mixing of soil and
crop residues. Residues remaining
on the soil surface dramatically
change from five per cent or less on
moldboard plow to up to 80 per cent
on a no-till system.
The increased residue cover can
significantly reduce the amount of
available nitrogen especially when
surface applied. The increased
surface cover accounts for a num
ber of soil changes.
Surface residues tend to reduce
runoff, increase infiltration and
reduce evaporation, leading to
higher soil moisture conditions.
Higher soil moisture can increase
leaching potential and cause
anaerobic conditions.
Residue increases often result in
<a shift in the microbial populations.
V a' Residue rich soils have increased
populations of the bacteria respon
sible for nitrification, denitrifica
tion and immobilization.
Nitrification is the process which
converts Ammonium N to Nitrate
N. Both Ammonium N and Nitrate
N are plant available. A concern
with the Nitrate N is that it can
easily leach out of the root zone.
Denitrification is the process of
converting Nitrate N to Nitrogen
gas. This results in a direct loss of
N and occurs when soil is anaerobic
or water logged.
Immobilization is another con
cern resulting from the residue rich
layer. Nitrogen may be tied up or
immobilized as the microbes try to
attain a balanced diet of C:N while
feeding on and breaking down crop
residues. Nitrogen immobilized in
this fashion becomes available
again after the microbes die off and
break down.
OMAF to hold
meetings on land
stewardship
A series of meetings will be held
around the province to generate
discussion on issues involving land
stewardship, David Ramsay,
Ontario Ministry of Agriculture and
Food announced recently.
“I have asked Jim McGuigan to
organize these meetings because
land stewardship initiatives will
play an important role in ensuring
the future sustainability and via
bility of the agriculture and food
industry in Ontario,” said Ramsay.
Jim McGuigan, parliamentary
assistant to the Minister, and MPP
for Essex-Kent, will meet interest
ed parties and discuss such issues
as top soil preservation, land
tenure and conservation plans.
Ministry staff will be on hand to
record the ideas and suggestions,
and information gathered from the
meetings will be used to help shape
ministry programs for the future.
‘‘There is a growing awareness
and acceptance among farmers for
new approaches to managing the
land,” said McGuigan. ‘‘The meet
ings will be informal and will be
addressing these subjects from a
very broad perspective, taking in
opinions on everything from land
tenure to costs and competitive
ness.”
A total of nine ‘‘by invitation”
consultation forums have been
scheduled from March 12 to March
27.
A final Nitrogen process is
volatilization. Volatilization (Am
monia N) is the loss of N as a gas
when N, usually in an urea form, is
surface applied.
Nitrogen products in general
have a very diverse make up. The
key product concern from a conser
vation cropping standpoint is whe
ther they are urea or urea based.
Trials conducted in Maryland in
dry years found that when urea was
surface-applied in a no-till situation
there was a significant yield loss.
However in wet years no yield loss
was experienced. The concern with
urea is that it volatilizes rapidly
when surface applied and not
worked in. A rainfall of one third of
an inch within two days is sufficient
to move the urea Nitrogen down
into soil. If rainfall is not received
with six days of broadcast urea,
then losses of up to 30 per cent or
more of your nitrogen can be
expected.
Rates of Nitrogen have also been
an area of concern. Gary Kachano-
ski, under the T2000 program, has
studied the effect of Nitrogen rates
on corn. He has found that by
delivering the rate of N required for
maximum economic yields in a
conventional system to a crop
under a no-till system there was no
significant yield increase. Also
discovered during these trials was
that in the check plots where no
Nitrogen was applied, the no-till
yielded significantly less than con
ventional. This leads us to assume
that for every pound of N applied in
no-till you get a greater yield
response when compared to con
ventional. If you lost Nitrogen from
application or poor product selec
tion, resulting in less N delivered to
the crop, yield will suffer more in
conservation. This is a major
reason to apply Nitrogen to your
crop in a fashion which minimizes
the factors which rob our crops of
Nitrogen.
Nitrogen handling under a high
residue system:
•Injection - where possible Nitro
gen should be injected under
surface residues.
•Banding or Dribbling - surface
broadcasting urea or 28 per cent
should be avoided; surface banding
urea or dribbling 28 per cent is
preferable to broadcasting; if forc-
ed to broadcast, avoid urea based
products.
•Rainfall - if using urea in a
broadcasting situation do so when
rainfall is expected.
The need to deliver Nitrogen to
the crop is essential to attaining
economical yields in a conservation
system More information on Ni
trogen fertilizer and specific rates
can be obtained from factsheets at
your local OMAF offices.
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