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The Food and Agriculture
Organization (FAO) report found that, "Organic agriculture performs
better than conventional agriculture on a
per
hectare scale, both with respect to direct energy consumption (fuel and
oil)
and indirect consumption (synthetic fertilizers and pesticides)", with
high
efficiency of energy use.
Since 1999, the Rodale Institute's long-term trials in the United
States
have
reported that energy use in the conventional system was 200 percent
higher than
in either of two organic systems - one with animal manure and green
manure, the
other with green manure only - with very little differences in yields.
Research
in Finland
showed that while organic farming used more machine hours than
conventional
farming, total energy consumption was still lowest in organic systems;
that was
because in conventional systems, more than half of total energy
consumed in rye
production was spent on the manufacture of pesticides.
[1]
Organic agriculture was more energy efficient than conventional
agriculture in
apple production systems. Studies in Denmark
compared organic and conventional farming for milk and barley grain
production.
The energy used per kilogram of milk produced was lower in the organic
than in
the conventional dairy farm, and it also took 35 percent less energy to
grow a
hectare of organic spring barley than conventional spring barley.
However,
organic yield was lower, so energy used per kg barley was only
marginally less
for the organic than for the conventional.
The FAO estimated that organic agriculture is likely to emit less
nitrous oxide
(N2O). This is due to lower N inputs, less N from organic manure from
lower
livestock densities; higher C/N ratios of applied organic manure giving
less
readily available mineral N in the soil as a source of denitrification;
and
efficient uptake of mobile N in soils by using cover crops.
Greenhouse gas emissions were calculated to be 48-66 percent lower per
hectare
in organic farming systems in Europe, and were attributed to no input
of
chemical N fertilizers, less use of high energy consuming feedstuffs,
low input
of P, K mineral fertilizers, and elimination of pesticides, as
characteristic
of organic agriculture.
Many experiments have found reduced leaching of nitrates from organic
soils
into ground and surface waters, which are a major source of nitrous
oxide. A
study reported in 2006 also found reduced emissions of nitrous oxide
from soils
after fertilizer application in the fall, and more active denitrifying
in
organic soils, which turns nitrates into benign N2 instead of nitrous
oxide and
other nitrogen oxides. [2]
Organic field crops and animal products generally consume less primary
energy
than non-organic counterparts, owing in part to the use of legumes to
fix N
rather than fuel to make synthetic fertilisers (Williams et al., 2006).
In
relation to this, many studies have found that the emissions related to
crop
production are lower in organic farms than in conventional farms when
measured
as a per hectare basis, but this advantage of organic production is
less clear
in units of crop yield, since yields are lower for some crops in
organic farms
(Flessa et al., 2001, Tzilivakis et al., 2005, Petersen et al., 2006).[3]
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