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organic agriculture fights back
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.
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
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
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
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.
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
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.
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.
This article can be found on the I-SIS website at http://www.i-sis.org.uk/