ISIS Report 17/02/04
"The Answer Lies in the Soil"
Traditional farming practices in the South are playing a major role
in preserving tropical soils and enhancing food security.
Lim Li Ching reports on some ingenious
strategies used by the farmers.
Sources
for this report are available in the ISIS members site.
Full details here
Soils are fundamental to agriculture, but tropical soils can be rapidly
depleted or eroded, depending on soil type, local conditions and farming
techniques. Although crop yields decline for many reasons and numerous complex
interactions are involved, research has shown that declining crop yield is in
most cases exponentially linked to loss of soil quality, in both the tropics
and the temperate regions.
Soil quality is a holistic concept, as soils are part of a dynamic and
diverse production system with biological, chemical and physical attributes
that are intimately linked to the needs of human societies. Society, in turn,
actively adapts the soil to its needs, mining its nutrients and replenishing
them in times of plenty.
Soil quality varies spatially and temporally, and is affected by
management and use of the soil resource. How actual production is affected by
soil quality depends on two factors: the intrinsic susceptibility of the soil
to erosion (resilience) and the variable impact of that erosion on yield
(sensitivity).
Resilience includes soil ‘strength’, or its resistance to
shocks such as severe rainstorms. It is manifested through specific degradation
or erosion rates on different soils subject to the same erosive conditions.
Sensitivity, on the other hand, denotes fragility or susceptibility to decline
in production per unit degradation. It is a measure of how far the change
induced in soil quality affects the soil’s productive capability.
The different combinations of resilience and sensitivity of tropical
soils, in turn, require different management strategies. The strategies are
themselves related to the capacity of farmers to provide remedial action. For
example, strategies that require mechanical structures will need financial and
human resources, which may be beyond the reach of many smallholder farmers.
Other strategies, such as using crop residues, green manures and alley
cropping, are effective ways to address both erosion and fertility decline.
Even at moderate levels of management such as that which most smallholder
farming households can afford, soils that have moderate resilience and low
sensitivity can effectively continue to withstand degradation and produce
indefinitely, at least for 50 years.
Professor Michael Stocking, from the School of Development Studies,
University of East Anglia, UK, has highlighted these dynamic links between
soils and farmers in a recent paper in Science.
Soil is thus not a static, homogenous medium; instead, it is a dynamic
entity, responding to how humans use it. The dynamism is reflected in
traditional farming practices that do more than just extracting nutrients; they
evolve in response to changing conditions over many years, through informal
experimentation and experience.
This capacity to respond draws on the farmers’ own local knowledge
and resources. According to Stocking, "smallholder farmers in the tropics have
skills and social networks that give us cause for optimism for future soil
quality and food security". Many, he stresses, are managing their soils
sustainably and productively; they "adapt technologies to their local needs
(using indigenous knowledge and innovation) and avoid labor-demanding and
expensive practices".
Traditional farming practices such as multiple cropping - planting
several different food crops in the same field - are excellent ways to preserve
soil quality and ensure food security, Stocking told Inter Press Service
(IPS). Multiple cropping, as opposed to monoculture, minimises
risks. When farmers plant a variety of crops, if the weather is bad for one it
will likely be good for another, or if disease affects one, it is likely that
others will survive. Not only does multiple
cropping spread the risks, but it also provides better nutrition, and the
surpluses can be sold.
"The better strategy in subsistence agriculture is not to maximise
production but minimize risk," said Stocking. Local knowledge enables
smallholder farmers to develop various techniques to minimise risk, including
maintaining soil quality for future years.
Success stories are increasingly common, such as that of Carlos Crovetto
Lamarca, who transformed an eroded farm along the steep coastal slopes in
central Chile. The farm started as little more than rocks and a series of 20m
deep gullies. But Crovetto developed a system for building soil based on
adopting a gentler tillage of plant roots, rather than ploughing. With crop
residues protecting the soil surface from the impact of rain, the soil
structure reformed. Rather than burning or ploughing, he spread straw or other
crop stubble over the soil. "I sell the grain today, and I preserve the stubble
so I can harvest tomorrow," he says.
It took a long time, but now, after nearly 30 years, Crovetto has
created over 30mm of organic topsoil. This happened at least 20 times faster
than what would have been made by natural rock-weathering processes.
Crovetto’s soil is so rich that his crop yields are as good as any in the
North. And, his soils are getting better each year. For farmers like Crovetto,
the importance of protecting and improving soil is clear – "we depend
daily on the most valuable resource, the soil".
Farmers are likely to invest in soil conservation as they are unlikely
to do anything that undermines their future or puts household livelihood and
food security at risk, unless immediate survival were in question. They also
adapt and experiment with methods that can increase benefits.
For example, Stocking cites the use of Mucuna pruriens
(velvetbean) as green manure mulch in sub-humid Benin, as evidence of
smallholder farmers’ adaptability, flexibility and responsiveness to
techniques that bring private benefits. From 15 original farmers involved in
experimentation in 1987, 100 000 were reported to have embraced this practice
by 1996 to counter soil fertility decline. Planting Mucuna beans has
also restored soil fertility on depleted soils in Latin America.
More often than not, farmers make better decisions that the
‘experts’, because of the experience gained in integrating the myriad
local factors responsible for controlling production. They are also often the
best arbiters when it comes to technologies. "Science does not always get it
right and does not necessarily provide workable or acceptable solutions".
An example is in semi-arid Kenya, where farmers choose
‘trashlines’ (bands of uprooted weeds and crop residues) to intercept
sediment and runoff, a technique never promoted by the advisory services. Yet,
when the marginal rates of return and net present values over 10 years are
calculated, trashlines are almost always the only technique of soil quality
maintenance that consistently benefits farmers’ livelihoods.
In Ghana, farmers plant up to 54 different varieties of climbing yams
(Dioscorea spp.) inside the forest to protect the vegetables. At the
same time, the forest keeps the soils moist and rich in organic matter. This
traditional means of maintaining soil-plant relationships also conserves
biodiversity, as the natural forest vegetation is kept to protect the climbing
yams.
A multi-faceted, flexible and diverse approach to managing soil quality
is obviously needed to address the complex realities that smallholder farmers
face. There are many examples from around the world, of farmers in the South
adopting various practices to improve soil quality and conserve soils, leading
to productivity increases (see Chapters 15 & 16 of the report of the
Independent Science Panel, The Case for
a GM-Free Sustainable World). All this is in striking contrast to the
simplistic, mechanistic approach of the dominant Western model of industrial
monoculture.
Agronomists and development professionals from the North often discount
the practices of smallholder farmers because the yields for individual crops
are low by comparison, as farmers tend to plant a diversity of crops. This
one-dimensional yield is a poor yardstick for food security. Maintaining soil
quality and fertility is by far the more important.
North American and European soils have been badly depleted, and remain
productive only on account of the massive amounts of chemical fertilizer
applied to them. "The soils here are just a passive medium keeping the plants
upright," says Stocking.
Agricultural productivity in the North is also wholly dependent on the
plentiful supply of cheap energy available to make fertilizers and to power
machinery, which makes it totally unsustainable. In contrast, with little or no
outside inputs, farming systems in the South are clearly much more sustainable
and productive in multi-faceted ways.
A major threat to productivity in the South is lack of tenure or access
to land. Farmers cannot maintain their soil in areas affected by civil conflict
or insecure land tenure. The greatest damage to soils occurs where conditions
are volatile, as with migrants and refugees, whose local knowledge is poor. In
such cases, depleting the soil of its nutrients is essential for survival, at
least in the short term. The security of tenure for smallholders could be made
even more difficult by changing national and global conditions.
Thus, efforts to improve declining trends in food security not only
ought to focus on local solutions that enhance farmers’ efforts to protect
and improve their soils, and allow them to produce enough of their own food,
but should also encourage policies that can bring about greater stability. They
must be rooted in secure rights to land, water and other resources, including
necessary credit and market. Traditional and appropriate modern techniques and
knowledge should be balanced.
There is much to be done in partnership with smallholder farmers, and
through learning from them. Stocking says, "Interventions that use
community-based approaches that empower farmers to manage their own situation
therefore hold the greatest promise for maintaining soil quality and ensuring
food security".
| 
