ISIS Report
Organic Agriculture Fights Back
Critics of organic agriculture claim that it is based more on
ideology than on environmental or economic merit.
Lim Li Ching reviews the evidence
and turns the table on the critics.
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Organic farming largely excludes synthetic inputs - pesticides,
herbicides and fertilisers – and focuses instead on biological
processes such as composting and other measures to maintain soil
fertility, natural pest control and diversifying crops and livestock.
Organic agriculture gives priority to long-term ecological health, such as
biodiversity and soil quality, contrasting with conventional farming,
which concentrates on short-term productivity gains.
Organic farming has been denigrated for being less efficient in land
use and having lower yields than conventional farming, and even accused of
posing potential health risks. According to a commentary in Nature
by Anthony Trewavas, Fellow of the United Kingdom Royal Society, "Although
its supporters assert that organic agriculture is superior to other
farming methods, the lack of scientific studies means that this claim
cannot be substantiated".
But he is wrong, there are scientific studies, peer-reviewed and
published, documenting organic agriculture’s positive outcomes.
Furthermore, certified organic production is just the tip of the iceberg
in terms of land managed organically but not certified as such. De
facto organic farming is prevalent in resource-poor and/or
agriculturally marginal regions where local populations have limited
engagement with the cash economy (see "Ethiopia to feed herself",
this issue). Farmers rely on locally available natural resources to
maintain soil fertility and to combat pests and diseases. They are showing
the way towards sustainable agriculture through sophisticated systems of
crop rotation, soil management, and pest and disease control, based on
traditional knowledge.
Similar or higher yields
The charge that organic farming is lower-yielding is misleading. Studies
simply evaluating the reduction or elimination of inputs in conventional
systems may not accurately represent conditions in alternative systems.
Furthermore, abstract comparisons made when farms have just turned organic
do not tell the whole story, as it takes a few years for yield to
increase. Thus, it is necessary to make long-term comparisons.
A study on conventional and alternative farming systems for tomatoes
over four years indicate that organic and low-input agriculture produce
yields comparable to conventional systems. Nitrogen (N) availability was
the most important factor limiting yield in organic systems, and can be
satisfied by biological inputs.
Another experiment examined organic and conventional potatoes and sweet
corn over three years. Results showed that yield and vitamin C content of
potatoes were not affected by the two different regimes. While one variety
of conventional corn out-produced the organic, there was no difference
between the two in yield of another variety or the vitamin C or E
contents. Results indicate that long-term application of composts is
producing higher soil fertility and comparable plant growth.
A review of replicated research results in seven different US
Universities and from Rodale Research Center, Pennsylvania and the Michael
Fields Center, Wisconsin over the past 10 years showed that organic
farming systems resulted in yields comparable to industrial, high input
agriculture.
- Corn: With 69 total cropping seasons, organic yields were 94% of
conventionally produced corn.
- Soybeans: Data from five states over 55 growing seasons showed
organic yields were 94% of conventional yields.
- Wheat: Two institutions with 16 cropping year experiments showed that
organic wheat produced 97% of the conventional yields.
- Tomatoes: 14 years of comparative research on tomatoes showed no
yield differences.
The most remarkable results of organic farming, however, have come from
small farmers in developing countries. Case studies of organic practices
show dramatic increases in yields as well as benefits to soil quality,
reduction in pests and diseases and general improvement in taste and
nutritional content. For example, in Brazil the use of green manures and
cover crops increased maize yields by between 20% and 250%; in Tigray,
Ethiopia, yields of crops from composted plots were 3-5 times higher than
those treated only with chemicals; yield increases of 175% have been
reported from farms in Nepal adopting agro-ecological practices; and in
Peru the restoration of traditional Incan terracing has led to increases
of 150% for a range of upland crops.
Projects in Senegal involving 2000 farmers promoted stall-fed livestock,
composting systems, use of green manures, water harvesting systems and
rock phosphate. Yields of millet and peanuts increased dramatically, by
75-195% and 75-165% respectively. Because the soils have greater water
retaining capacity, fluctuations in yields are less pronounced between
high and low rainfall years. A project in Honduras, which emphasized soil
conservation practices and organic fertilisers, saw a tripling or
quadrupling of yields.
In Santa Catarina, Brazil, focus has been placed on soil and water
conservation, using contour grass barriers, contour ploughing and green
manures. Some 60 different crop species, leguminous and non-leguminous,
have been inter-cropped or planted during fallow periods. These have had
major impacts on yields, soil quality, levels of biological activity and
water-retaining capacity. Yields of maize and soybeans have increased by
66%.
Efficient production
The world’s longest running experiment comparing organic and
conventional farming pronounced the former a success. The 21-year study
found that soils nourished with manure were more fertile and produced more
crops for a given input of nitrogen or other fertiliser. Nutrient input in
the organic systems was 34 to 51% lower than in the conventional systems,
whereas mean crop yield was only 20% lower over 21 years, indicating
efficient production and use of resources. The ecological and efficiency
gains more than made up for lower yields. In the long term, the organic
approach was commercially viable, producing more food with less energy and
fewer resources.
The biggest bonus was improved quality of the soil under organic
cultivation. Organic soils had up to 3.2 times as much biomass and
abundance of earthworms, twice as many arthropods (important predators and
indicators of soil fertility) and 40% more mycorrhizal fungi colonising
plant roots. Mycorrhizal fungi are important in helping roots obtain more
nutrients and water from the soil.
The enhanced soil fertility and higher biodiversity is believed to
render the organic plots less dependent on external inputs and provide
long-term environmental benefits.
Better soils
Indeed, organic agriculture is helping to conserve and improve farmers’
most precious resource – the topsoil. To counter the problems of
hardening, nutrient loss and erosion, organic farmers in the South are
using trees, shrubs and leguminous plants to stabilise and feed soil, dung
and compost to provide nutrients, and terracing or check dams to prevent
erosion and conserve groundwater.
Field experiments conducted at three organic and three conventional
vegetable farms in 1996-1997 examined the effects of synthetic fertilisers
and alternative soil amendments, including compost. Propagule densities of
Trichoderma species (beneficial soil fungi that are biological
control agents of plant-pathogenic fungi) and thermophilic microorganisms
(a major constituent of which was Actinomycetes, which suppresses Phytophthora)
were greater in organic soils. In contrast, densities of Phytophthora
and Pythium (both plant pathogens) were lower in organic
soils.
While the study recorded increased enteric bacteria in organic soils,
the researchers stressed that this was not a problem, as survival rates in
soil are minimal. Critics of organic farming have disingenuously pointed
to the possible human health effects of using manure. But untreated manure
is not allowed in certified organic culture, and treated manure
(known widely as compost) is safe - this is what is used in organic
farming. Unlike conventional regimes (where manure might be used),
mandatory organic certification bodies inspect farms to ensure standards
are met.
Little yield difference was observed in the first year. In the second
year, tomato yields were higher on farms with a history of organic
production, regardless of soil amendment type, probably due to the
benefits of long-term organic amendments. Mineral concentrations were
higher in organic soils whilst soil quality on conventional farms was
significantly improved by the addition of organic fertiliser.
Another means to restore soil fertility in organic systems is through
legumes. A 15-year study compared three maize/soybean agro-ecosystems. One
was a conventional system using mineral N fertiliser and pesticides. The
other two systems were managed organically. One was manure-based, where
grasses and legumes, grown as part of a crop rotation, were fed to cattle.
The manure provided N for maize production. The other did not have
livestock; N fixed by legumes was incorporated into soil.
Amazingly, the 10-year-average maize yields differed by less than 1%
among the three systems. Soil organic matter and N content increased
markedly in the manure system and, to a lesser degree, in the legume
system, but were unchanged or declined in the conventional system. The
latter had greater environmental impacts - 60% more nitrate leached into
groundwater over a 5-year period than in the organic systems.
In Honduras, the mucuna bean has improved crop yields on steep, easily
eroded hillsides with depleted soils. Farmers first plant mucuna, which
produces masses of vigorous growth that suppresses weeds. When the beans
are cut down, maize is planted in the resulting mulch. Subsequently, beans
and maize are grown together. Very quickly, as the soil improves, yields
of grain are doubled, even tripled. Mucuna produces 100 tonnes of organic
material per hectare, creating rich, friable soils in just 2-3 years.
Mucuna also produces its own fertiliser, fixing atmospheric N and storing
it in the ground where it can be utilised by other plants.
No increased pests
Because organic farms don’t use synthetic pesticides, critics claim
that losses due to pests would rise. However, research on Californian
tomato production found that the withdrawal of synthetic insecticides does
not lead to increased crop losses as a result of pest damage. There was no
significant difference in pest damage levels on 18 commercial farms, half
of which were certified organic systems and half, conventional operations.
Arthropod biodiversity was on average one-third greater on organic farms
than on conventional farms. There was no significant difference between
the two for abundance of pests, but densities of natural enemies were more
abundant on organic farms, with greater species richness of all functional
groups (herbivores, predators, parasitoids). Thus, any particular pest
species in organic farms would be associated with a greater variety of
herbivores (i.e. diluted) and subject to a wider variety and greater
abundance of potential parasitoids and predators.
At the same time, research has shown that pest control is achievable
without pesticides, reversing crop losses. For example, in East Africa,
maize and sorghum face two major pests – stemborer and Striga, a
parasitic plant. Field margins are planted with ‘trap crops’
that attract stemborer, such as Napier grass. Pests are lured away from
the crop into a trap – the grass produces a sticky substance that
kills stemborer larvae. The crops are inter-planted with molasses grass
(Desmodium uncinatum) and two legumes: silverleaf and greenleaf.
The legumes bind N, enriching the soil. But that’s not all. Desmodium
also repels stemborers and Striga.
Korean researchers recently reported that avoiding pesticides in paddy
fields encourages the muddy loach fish, which effectively control
mosquitoes that spread malaria and Japanese encephalitis. The larvae
numbers of the mosquito vectors were significantly lower in organic sites.
Higher biodiversity
Maintaining agricultural biodiversity is vital to ensuring long-term
food security. Organic farms often exhibit greater biodiversity than
conventional farms, with more trees, a wider diversity of crops and many
different natural predators, which control pests and help prevent disease.
Proving with stunning results that planting a diversity of crops is
beneficial (compared with monocultures), thousands of Chinese rice farmers
have doubled yields and nearly eliminated its most devastating disease,
without using chemicals or spending more. Under the direction of
scientists, farmers in Yunnan implemented a simple change that radically
restricted the incidence of rice blast. Instead of planting large stands
of a single type of rice, as they typically have done, they planted a
mixture of two different kinds of rice: a standard rice that does not
usually succumb to rice blast disease and a much more valuable sticky rice
known to be very susceptible.
Resistant plants not only blocked the airborne spores, but as more
farmers participated, positive effects began to multiply. Not only were
spores not blowing in from the next row, they were no longer coming from
the next farmer’s field either, rapidly halting the disease’s
spread. The sticky rice plants, which rise above the shorter, standard
rice plants, enjoyed sunnier, warmer and drier conditions that also
discouraged the growth of ice blast.
Furthermore, empirical evidence from a study conducted since 1994 shows
that biodiverse ecosystems are 2-3 times more productive than
monocultures. In experimental plots, both aboveground and total biomass
increased significantly with species number. The high diversity plots were
fairly immune to the invasion and growth of weeds, but this was not so for
monocultures and low diversity plots. Thus, biodiverse systems are also
less prone to weeds!
The last word - sustainability
Research published in Nature investigated the sustainability of
organic, conventional and integrated (combining organic and conventional
methods) apple production systems in Washington from 1994-1999. All three
gave comparable yields, with no observable differences in physiological
disorders or pest and disease damage.
The organic system ranked first in environmental and economic
sustainability, the integrated system second and the conventional system
last. A sustainable farm must produce adequate high-quality yields, be
profitable, protect the environment, conserve resources and be socially
responsible in the long term. Specific indicators used were soil quality,
horticultural performance, orchard profitability, environmental quality
and energy efficiency.
Soil quality ratings in 1998 and 1999 for the organic and integrated
systems were significantly higher than for the conventional system, due to
the addition of compost and mulch. There were satisfactory levels of
nutrients among all three systems. A consumer taste test found organic
apples less tart at harvest and sweeter than conventional apples after six
months of storage.
Organic apples were the most profitable due to price premiums and
quicker investment return. Despite initial lower receipts in the first
three years, due to the time taken to convert to certified organic
farming, the price premium to the grower of organic fruit in the next
three years averaged 50% above conventional prices. In the long term, the
organic system recovered initial costs faster. The study projected that
the organic system would break even after 9 years, but that the
conventional system would do so only after 15 years, and the integrated
system, after 17 years.
The environmental impact of the three systems was assessed by a rating
index related to the potential adverse impacts of pesticides and fruit
thinners: the higher the rating, the greater the negative impact. The
conventional system index was 6.2 times that of the organic system.
Despite higher labour needs, the organic system expended less energy on
fertiliser, weed control and biological control of pests, making it the
most energy efficient.
If you wish to see the
complete document
with references, please consider becoming a member or friend of ISIS.
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