WINNIPEG – A federal government commitment to ratify the Kyoto Accord
on greenhouse gas reduction has prairie producers worried about the
impact it will have on their farms.
Farmers could face several problems: How difficult will it be to reduce
the flow of greenhouse gases from crop land? What voluntary actions can
farmers take now to avoid government regulation?
The answers to these questions may not be as difficult as they seem.
Atmospheric measurements taken on six farms in the Red River Valley in
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2002 documented a 26 percent overall reduction in greenhouse gas
emissions on wheat fields when fertilizer was applied based on a
variable rate prescription map, compared to neighbouring wheat fields
fertilized in the conventional manner.
The research, conducted by the University of North Dakota, was
presented in a Nov. 6 seminar at the Agriculture Canada research centre
in Brandon.
Scientists Rebecca Phillips and David Brookman said the variable rate
fertilizer applications reduced greenhouse gas emissions and also led
to better financial returns.
“At one of the farms, the precision farming technique gave the producer
a $13,000 benefit on a 74 acre field over a two year period,” Phillips
said.
“This financial benefit came through a combination of cost savings on
fertilizer and a higher yield. He put down about 10 percent less
fertilizer on that field.”
The variable rate farm is owned by Pete Carson of St. Thomas, N.D.,
near the Canada-United States border. His variable rate prescription
map is based on field history, soil testing and remote sensing imagery.
“After working with precision farming since 1994, Carson has reached
the point where he now routinely applies more fertilizer in the areas
he knows will produce more crop, and less fertilizer in the areas with
less potential,” Brookman said.
“For example, where he knows his soil can support a 100 bushel crop, he
fertilizes to a 100 bu. target. Where his soil can only support a 50
bu. crop, he uses 50 bu. as his fertilizer target. That’s the economic
rationale for what he’s doing. The side effect is that he avoids
putting down fertilizer that will end up in the atmosphere.”
The research was done at three sites, with two fields at each site. At
each site, one field was fertilized using variable rate technology. The
comparison field, located a kilometre away, was fertilized in the
conventional manner. The farms were commercial operations and did not
alter their practices for the study. Research plots were not used.
The two primary greenhouse gases measured in the fields were carbon
dioxide (CO2) and nitrous oxide (N2O).
Carbon dioxide is released from decomposing organic matter.
Nitrous oxide is found in much smaller amounts, but is far more potent,
with a global warming potential 310 times more powerful than CO2.
Whatever form of nitrogen added to or existing in soil, it is
susceptible to N2O loss through a process called denitrification. This
is the conversion or reduction of nitrate (NO3-) to N2O and dinitrogen
gas (N2) in waterlogged conditions.
The loss of N2O represents a loss of costly nitrogen inputs; so it
makes environmental and economic sense for producers to use nitrogen
more efficiently.
Phillips and Brookman used a Gas Chromatography Shimadzu Varian. A
portable collection chamber was placed on the soil surface to collect
air samples given off over one hour. Samples were taken five times in
each field during the growing season.
Data collected showed that carbon dioxide given off from the soil
averaged 202 micrograms per acre per day in the precision field and
just over 280 micrograms per acre per day in the conventional field.
Nitrous oxide flow averaged less than 0.04 micrograms per acre per day
in the precision field and 0.2 micrograms per acre per day in the
conventional field.
The data also showed the environmental benefit was greater in dry
soils than in fields with moist soil. This led the researchers to
suggest that the potential for reducing greenhouse gas emissions might
be greater in the drier areas of the Prairies than in the Red River
Valley.
Alan Moulin, Agriculture Canada soil scientist at Brandon, agrees with
most of the North Dakota researchers assessment of the benefits of
precision farming west of the Red River Valley, but with some
reservations.
“I think there’s significant potential for variable rate in western
Manitoba, for instance,” he said. “But in terms of moisture, we’re in a
very different situation here than a farmer at, say, Swift Current.
“I’ve worked with scientists at Swift Current who found totally
different results in different years with variable rate. One year it
has a positive effect. The next year it doesn’t. It all relates to
weather and moisture, and that is a highly variable factor.
He said it takes years of data collection to make a beneficial
prescription map.
“You need data from at least five years to get the kind of results we
see from a farmer who started precision farming in 1994,” Moulin said.
