Friday,
October 05, 2007
Why organic food can't feed the world
- Craig Meisner, Cosmos Online, Sept. 24, 2007 via Agbioview
This item addresses recent studies have that have re-visited the idea that
organic methods of agriculture would be sufficient to feed the world - but
argues they are they are flawed because of naïveté about agriculture in
developing nations.
Can organic food feed the world? A recent study, published in the journal Renewable
Agriculture and Food Systems provides new data that suggests it can. However,
I have some grave reservations about this prospect that are based on my
experience as a scientist and my time living and working with real farmers in
developing nations...
Heavy burden
So, why won't the use of pure organics work in developing countries like
Bangladesh?
Most supporters of the idea that organic farming can feed the world, assume
that organic manures are cheap and available to all - even the poor. But this
isn't often the case. I see cow dung in Bangladesh and all of South Asia as a
valuable commodity. During my walks in the villages I see it collected
largely by women and children and used as fuel. It's found in nearly every
house, dried and formed into patties, to be sold or burned for cooking.
Straw is another organic source of nutrients, but that's not always available
either. Rice and wheat straw is collected from the fields, and used for
cattle feed or thatching for roofs. Even the stubble is used, which the
poorest come and cut for fuel.
The authors of the study mentioned above - led by researchers at the
University of Michigan in Ann Arbor, U.S. - have rightly assumed that
organics can supply sufficient nutrients for plant growth. However, the quantities
of organics required to sustain such productive growth makes it very
difficult for the poor to handle. Organics whether farmyard manure, compost,
or cow dung, contain moisture and are heavy and difficult to carry from the
homestead to the fields by the growers.
For example, to raise a six-tonne rice crop in the peak season requires 100
kg of nitrogen. Because of monsoons and the fact that several metres of
rainfall drains through the soil every three months, the amount of nitrogen
it carries is low. Assuming we used good quality manure, there would be about
0.6 per cent nitrogen in the material; thus, requiring 17 tonnes per hectare
to produce a six-tonne rice yield.
Can you imagine carrying 17 tonnes of manure, in repeated 50 kilogram loads,
in a basket on your head? The lack of machinery to carry that material and
the labour required to apply it, compounds the challenge.
Plus, there just simply isn't enough manure, or even plant biomass, available
to apply 17 tonnes per hectare, for even a single annual rice crop across the
whole of Bangladesh. That's enough of a problem, but when you consider there
are actually two rice crops a year, the full scale of the problem becomes
apparent!
Green manure
In answer to some of these problems, the new study proposes the use of a
leguminous 'green manure' crop. These pulse crops fix nitrogen into the soil
from the air through a symbiotic relationship with bacteria in their roots.
They provide enough nitrogen for their own growth and more, and when ploughed
under provide nitrogen for a subsequent crop too.
However for such a crop to be used in Bangladesh, it would have to take the
place of a food crop, effectively halving the amount of food the land can
provide. The cropping intensity in many developed countries is well over two
crops per year, but I have seen as many as four to five crops per year in
places that are elevated and flood-free.
Besides substituting for a food crop, green manure crops would also require
cutting and ploughing under the soil. While ploughing technology has
increased dramatically in the last decade in many developed countries, it is
mostly the two-wheel tractors or roto-tiller types; thus making it a
significant challenge to plough down any high-biomass green manure or crop
residues into the soil.
Some propose a greater use of leguminous food crops to supply nitrogen for
the proceeding cereal crop and where possible, growers would love to expand
pulses. However, in South Asia, while the national pulse yields appear
stable, switching to more of these crops is quite risky for individual
farmers due to unseasonable rainfall, diseases, and poor growing
environments.
Faced with a choice
So, to make compost effectively, one has to have surplus plant biomass and
cow dung. For the poor who have limited land and animals, this is quite
difficult.
Surveys I have conducted in Bangladesh clearly show that growers that do have
the ability to add organics to their land are those who are richer and have
larger land holdings and animals. The poor have to rely on purchased
fertilisers, whether organic or chemical. When faced with a choice based on
labour and expense, the poor choose the non-organic fertilisers...
When I have asked growers in Bangladesh, most would love to be able to use
more organics in their farming production. But due to the lack of
availability and costs, organics are actually being used less each year.
Can organic agriculture feed the world? No, but most growers understand that
it benefits the soil, and as such its use is is advocated as much as is
possible. Unfortunately, for Bangladesh, and many developing countries, those
possibilities are diminishing yearly as organics become less and less
available and affordable.
Craig Meisner is Adjunct International Professor of Crops and Soils at
Cornell University of Ithaca, New York. He is based in Dhaka, Bangladesh.
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