In the debate over high input and organic farming last week,
several people made reference to developing countries in the
tropics, especially sub-Saharan Africa, to make their case. As
someone who has spent most of the last 15 years working as an
agronomist in sub-Saharan Africa and the Caribbean, I find neither
sides' positions entirely satisfactory from the perspective of the
Third World and the realities and constraints facing farmers in
the developing world.
Robert Stevahn suggests loss of wildlife and presumably other
environmental problems are the result of the export of Western
agricultural technology and "hooking them on expensive technology."
That can hardly be true of sub-Saharan Africa, where 95 % of the
region's food is produced by low resource farmers (Mellor et al.,
1987). Much of this production is achieved with manual labor,
little or no fertilizer and little or no pesticides. It is true
that there have been disastrous attempts at large-scale farming.
I have had occasion to visit a few such farms and most of them
suffered from agronomic and managerial mismanagement, lack of spare
parts and a host of other problems typical of developing countries
and can hardly serve as evidence for or against the technical
feasibility of high input commercial agriculture. Although some
used destructive land clearing practices and did not take adequate
precautions to control runoff over large surfaces, they represent
a drop in the bucket, in terms food production in the region.
Dennis Avery stated that "most of the wildlife the world is losing
has been the result of extending low-yield organic farming methods
in countries like Ecuador and Nigeria." I do not know Ecuador, but
I do know Nigeria, and I hardly think agriculture can take all the
blame. Hunting and destruction of habitat through logging,
urbanization and probably fires all share in the
loss of wildlife and habitat. In some countries, like Haiti, the
need for fuel is also an important cause of habitat destruction.
In slash and burn agriculture, farmers usually do not kill all the
trees and regeneration of natural vegetation occurs quickly once
the site is abandoned. Logging with heavy equipment would seem to be
much more destructive to the environment, leaving the soil more exposed
to erosion and removing upper story trees that can take decades to replace.
Avery does havea point, however, that low input agriculture practiced in
much of the tropics is demanding in terms of its use of natural
habitat. The following hypothetical example shows why.
Lets assume that a family is cultivates 1.5 ha, not an
unreasonable size for this region of the world. Without
external inputs, he will have to abandon his land after 3
years of cultivation because of depleted fertility. Shifting
cultivation is sustainable, according to the literature, if the
natural fallow lasts sufficiently long to allow complete regeneration
of the natural vegetation. Estimates vary as to how long that
may take, but lets take ball park figures of 7 years in
savanna and 20 years in forest. Let's also assume for
simplicity that the farmer divides his land into thirds, with
a rotation of 2 crops maize (year 1), maize (2 crops) /
cassava intercrop (year 2), with second year cassava ending
the rotation (year 3). Let's estimate maize
yields at 2 and 1 t/ha in first and second years, respectively
and cassava at 10 tons fresh tubers/ha in the third. Total
annual production: 3 t maize, 5 t cassava. However, on an
land-use basis, that works out to 300 kg maize/ha/year and 500
kg fresh cassava tubers/ha/year in savanna; 130 kg maize and
217 kg cassava tubers/ha/year in forest. Or inversely, 10-23
ha of land is required to produce a yearly harvest of 3 t
maize and 5 t cassava. Of course, there will also be secondary
crops, such as vegetables, fruit and legumes, as well as harvest
of a few products from fallow species, but it is the staple crops
on which farmers rely for their survival.
With increasing population and without an increase in productivity,
only two outcomes are possible. Agricultural production can
remain sustainable by converting larger areas of natural habitat to
agriculture. Or, the shifting cultivation gradually becomes
permanent no-input agriculture with fallows diminishing to the
extent that productivity declines. In either case the effect on
the environment is negative. It is reasonable to conclude that the
high land requirement of low-input agriculture is leading to
deforestation, soil degradation and soil erosion in many places in
the tropics.
Several contributors have suggested that population growth is the
problem. However, population, per se, is not a general problem in
much of tropical Africa; demographics is. Apart from certain regions,
such as SE Nigeria and the central African highlands, much of sub-
Saharan Africa is not over-populated. Even without population increase,
the problem would still occur. People congregate where
services are available, thereby over-cropping land within easy
proximity. How far can you travel to your fields on foot or
bicycle and still have time and energy to farm? How far from town
do you live if you want your children to attend school? Several
generations ago, in parts of Africa, villages were not at permanent
locations but moved as cropped fields became less productive. That
is not possible in modern Africa. Although land is abundant,
accessible land becomes scarce, fallow periods decline and so does
productivity. Population increase should be controlled, but the
way to achieve it is to enable the developing world's farmers to
increase their standard of living through more productive
agriculture.
Only modest levels of nitrogen and phosphorus are often enough to
obtain 50-100 % increases in yield and to extend the period of
cropping. Yields comparable to temperate production are possible
with high inputs. However, long-term use of fertilizers is not
enough to sustain yields at a high level (Kang and
Balasubramanian, 1990), or if so, not at economic levels.
Replenishment of organic matter is key. However, the strategies
taken by Western commercial agriculture, whether organic or
otherwise, are mostly inappropriate in the agricultural economies
of developing countries. No-till systems based upon herbicides, for
example, require inputs beyond the reach of most farmers.
Benbrook and others advocated sharing of landscapes between
wildlife and food production. Try telling that to a farmer who has
had his farm trashed by a herd of elephants. Setting aside habitat for
cobras and green mambas would neither be popular nor healthy. I have to
agree with
Avery on this point, wildlife preserves seem like a much better
idea.
It seems to me that Sustainable Agriculture for Third World farmers
will have to develop on a course of its own, integrating the best
and most appropriate ideas from both sides of this debate in order
to attain sustainable increases in yield. They need fertilizers to correct
nutrient imbalances and raise the ceiling on yields, and they need ways to
sustain productivity through organic matter and nutrient recycling. They
also need safe ways to protect crops from insects and diseases. Much
research needs to be done, and it is unfortunate to see support for
agricultural research in this region dwindling at such a critical period.
Mellor, J.W., C.L. Delgado and M.J. Blackie, 1987. Priorities for
accelerating food production in Sub-Saharan Africa. In
Accelerating Food Production in Sub-Saharan Africa. eds J.W.
Mellor, C.L. Delgado & M.J. Blackie. John Hopkins University
Press.
Kang, B.T. and V. Balasubramanian, 1990. Long-term fertilizer
trials on Alfisols in West Africa. Transactions 14'th
International Congr. Soil Sci., Kyoto, Japan 4: 20-25
Dennis A. Shannon
Department of Agronomy and Soils
202 Funchess Hall
Auburn University, Alabama 36849-5412
Telephone: 334-844-3963
Facsimile: 334-844-3945
E-mail: dshannon@ag.auburn.edu