ISIS Press Release 12/09/05
Organic Agriculture Enters Mainstream
Organic Yields on Par with Conventional and Ahead During Drought Years
But by far the greatest gains are due to savings on damages to public health
and the environment estimated at more than US$59 billion a year Dr.
Mae-Wan Ho puts the nail on the coffin on industrial agriculture
A fully referenced version
of this article is posted on ISIS members’ website. Details here
Myths die hard
Scientists who should know better - if only they had kept up with the literature
- continue to tell the world that organic agriculture invariably means lower
yields, especially compared to industrial high input agriculture, even when
this has long been proven false (see for example, “Organic agriculture fights
back” SiS
16 [1]; “Organic production works”, SiS
25 [2]).
Researchers led by David Pimenthal, ecologist and agricultural scientist at
Cornell University, New York, have now reviewed data from long-term field investigations
and confirmed that organic yields are no different from conventional under normal
growing conditions, but that they are far ahead during drought years [3]. The
reasons are well known: organic soils have greater capacity to retain water
as well as nutrients such as nitrogen.
Organic soils are also more
efficient carbon sinks, and organic management saves on fossil fuel, both
of which are important for mitigating global warming. But by far the greatest gains are in savings
on externalised costs associated with conventional industrial farming, which
are estimated to exceed 25 percent of the total market value of United States’
agricultural output.
Long-term field trials at Rodale Institute
From 1981 through 2002,
field investigations were conducted at Rodale Institute in Kutztown, Pennsylvania
on 6.1 ha. Three different cropping systems: conventional, animal manure and
legume-based organic, and legume-based organic. Plots (18 x 92 m) were split
into three (6 x 92 m) subplots, which are large enough for farm-scale equipment
to be used for operations and harvesting. The main plots were separated with
a 1.5 m grass strip to minimize cross movement of soil, fertilizers, and pesticides.
Each of the three cropping systems was replicated eight times. The conventional system based on synthetic
fertilizer and herbicide use, represented a typical cash-grain 5-year crop
rotation (corn, corn, soybeans, corn, soybeans) that reflects commercial conventional
operations in the region and throughout the Midwest. According to USDA 2003
data, there are more than 40 million ha in this production system in North
America. Crop residues were left on the surface of the land to conserve soil
and water; but no cover crops were used during the non-growing season.
The organic animal-based
cropping represented a typical livestock operation in which grain crops were
grown for animal feed, not cash sale. This rotation was more complex: corn,
soybeans, corn silage, wheat, and red clover-alfalfa hay, as well as a rye
cover crop before corn silage and soybeans. Aged cattle manure served as the
nitrogen source and applied at 5.6 tonnes per ha (dry), 2 years out of every
5 immediately before ploughing the soil for corn. Additional nitrogen was
supplied by the plough-down of legume-hay crops. The total nitrogen applied
per ha was about 40 kilograms per year or 198 kg per ha for any given year
with a corn crop. Weed control relied on mechanical cultivation, weed-suppressing
crop rotations, and relay cropping, in which one crop acted as living mulch
for another.
The organic legume-based cropping represented a cash grain operation without
livestock. The rotation system included hairy vetch (winter cover crop used
as green manure), corn, rye (winter cover crop), soybeans, and winter wheat.
The total nitrogen added to this system per ha per year averaged 49 kg (or 140
kg per ha) per year with a corn crop). Both organic systems included a small
grain, such as wheat, grown alone or inter-seeded with a legume. Weed control
was similar in both organic systems.
Yields no different except under drought conditions
For the first five years
of the experiment (1981-1985), the yields of corn grain averaged
4 222, 4 743 and 5 903kg
per ha for organic-animal, organic-legume, and conventional systems. After this transition period, corn grain yields were
similar for all systems: 6 431,
6 368, and 6 553 kg per
ha. Overall, soybean yields from 1981 through 2001 were 2 461,
2 235 and 2 546 kg per ha;
the lower yield of organic legume system is attributed to the failure of the
soybean crop in 1988, when climate conditions were too dry to support relay
intercropping of barley and soybeans. If 1988 is taken out of the analysis,
soybean yields are similar for all systems. The 10-year
period from 1988-1998 included 5 years in which the total rainfall from April
to August was less than 350 mm (compared with 500mm in average years). Average corn yields in those dry years were significantly
higher (28 percent to 34 percent) in the two organic systems: 6938 and 7235kg
per ha in organic-animal and organic-legume systems compared with 5333 kg
per ha in the conventional system.
During the extreme
drought of 1999 (total rainfall between April and August only 224mm), the
organic animals system had significantly higher corn yields (1511 kg per ha)
than either the organic legume (421 kgper ha) or the conventional (1100kg
per ha). Crop yield in the organic legume were much lower in 1999 because
the high biomass of the hairy vetch winter cover crop used up a large amount
of the soil water. During the 1999 drought soybean yields were 1400, 1800
and 900 kg per ha for organic animal, organic-legume and conventional.
Other advantages of organic systems
Over a 12-year period, water volumes percolating through
each system were 20 percent and 15 percent higher in the organic-animal and
organic legume systems than in conventional. During the growing season in
1995, 1996, 1998 and 1999, soil water content
was significantly higher in the soil farmed using the organic legume system
than in the conventional system, accounting for the much higher soybean yields
in the organic legume system in 1999. About 5.2 million kilocalories of energy
per ha were invested in the production of corn in the conventional system.
Energy inputs for the organic animal and organic legume
systems were 28 percent and 32 percent less. The energy inputs for
soybean production in the organic-animal, organic legume and conventional
systems were similar at 2.3 mkcal, 2.3 mkcal, and 2.1 mkcal respectively. Economic comparison of the organic corn-soybean rotation
with conventional corn-soybean systems from 1991-2000 showed that without
price premiums for the organic rotation, the annual net returns for both were
similar:$184 per ha for conventional, $176 per ha for organic legume
(Table 1).
Table 1. Annual costs per
ha
| |
Organic legume |
Conventional |
| Seed |
$103 |
$73 |
| Fertilizers &Lime |
$18 |
$79 |
| Pesticides |
$0 |
$76 |
| Machinery |
$154 |
$117 |
| Hired labour |
$6 |
$9 |
| Total |
$281 |
$354 |
| Revenue |
$457 |
$538 |
| Net income |
$176 |
$184 |
Soil carbon
at start (1981) was not different between the three systems. In 2002, however,
soil carbon levels in the organic animal and organic legume systems were 2.5
percent and 2.4 percent versus 2.0 percent in the conventional. The annual
net aboveground carbon input (based on plant biomass and manure) was the same
in organic legume system and conventional system (~9 000kg per ha), but about
10 000 kg per ha in organic animal system. However, the two organic systems
sequester more of that carbon in the soil, resulting in an annual soil carbon
increase of 981 and 574 kg in the organic animal and organic legume systems,
compared with only 293 kg per ha in the conventional systems (calculated on
the basis of about 4 million kg per ha of soil in the top 30cm.). Total soil
carbon increase after 22 years was: 27.9 percent, 15.1 percent and 8.6 percent
in organic animal, organic legume and conventional systems. Soil nitrogen
levels started at 0.31 percent in 1981. By 2002, the conventional system remained
unchanged, while organic animal had increased to 0.35 percent and organic
legume system to 0.33 percent. Using 15N
to measure retention of N in soil it was estimated that 47 percent, 38 percent
and 17 percent respectively of the nitrogen from organic animal, organic legume
and conventional was retained in the soil each year after application. This
matched the decreased amount leached from the organic soils. Four herbicides
were applied in the conventional system: atrazine (to corn), pendimethalin
(corn), metolachlor (corn and soybeans) and metribuzin (soybeans). From 2001
to 2003, only atrazine and metolachlor were detected in water leachates collected
from conventional systems at levels in excess of 3 parts per billion, exceeding
maximum contaminant level set by US EPA for atrazine (no level has been set
for metolachlor). Soils farmed
with the two organic systems had greater populations of spores of the beneficial
Arbuscular mycorrhizal fungi, shown to enhance disease resistance, improve
water relations and increase soil aggregation. Large amounts
of biomass (soil organic matter) are expected to significantly increase soil
biodiversity. Microarthropods and earthworms were reported to be twice as
abundant in organic versus conventional agricultural systems in Denmark. Earthworms
and insects create holes in the soil that increase the percolation of water
into the soil and decrease runoff.
Labour requirements
Each system was allowed
250 “free” family labour per month; while the cost of hired labour was $13
per hour. With organic farming system, the farmer was busy throughout the
summer with the wheat crop, hairy vetch cover crop, and mechanical week control
but worked less than 250 hours per month). In contrast, the conventional farmer
had large labour requirements in the spring and fall, plating and harvesting,
but little in the summer months.
Increase in labour
input may range from 7 percent to a high of 75 percent in organic compared
to conventional systems. But in situations where human labour is not in short
supply, this too can be an advantage of organic agriculture in creating employment.
The externalised costs of conventional agriculture not taken into account
By far the biggest gains from organic agriculture arise
from the savings on the damages to public health and the environment due to
the use of agrochemicals in conventional agriculture. The National Organic Standards Program in
the United States prohibits the use of synthetic chemicals, GMOs and sewage
sludge in organically certified production. As Pimenthal
points out [3], the estimated environmental and healthcare costs of pesticide
use at recommended levels in the US is about 12 billion every year. According
to the National Research Council [3], the cost of excessive fertilizer use
is $2.5 billion per year, while the estimated annual costs of public and environmental
health losses related to soil erosion greater than $45 billion [5]. The total externalised
cost of conventional agriculture per year is $59.5 billion. This represents
27.4 percent of the entire agricultural output ($217.2 billion in 2002 [6]).
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