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  • From: "Tradingpost" <tradingpost@lobo.net>
  • To: livingontheland@lists.ibiblio.org
  • Subject: [Livingontheland] Restoring Degraded Soils a Matter of Urgency
  • Date: Thu, 31 Jan 2008 13:01:45 -0700


Restoring Degraded Soils a Matter of Urgency
http://www.i-sis.org.uk/RDS.php
Lim Li Ching reports

Sources for this article are posted on ISIS membersÂ’ website. Details
here.

Research has shown that declining crops yields are, in most cases,
exponentially linked to loss of soil quality. Soils are threatened by water
and wind erosion, nutrient depletion and salinisation, among other things.

Although, on a global scale, soil loss is unlikely to be a major threat to
food security, the impacts are probably going to be felt acutely at the
local and regional levels. This is especially so where farmers are too poor
to curb or overcome the damage.

Mechanized agriculture has caused billions of tonnes of carbon previously
trapped in soil to be released to the atmosphere as carbon dioxide and
methane. Lack of carbon in the soil makes crop production inefficient and
constrains yields.

Global warming is likely to make things worse. As the ground heats up,
organic matter decomposes more easily, reducing soil fertility, releasing
carbon dioxide and further exacerbating the warming effect. In fact, soil
erosion already contributes to global warming, as some of the carbon in
soil-laden water running off fields inevitably escapes into the atmosphere.
Deserts are expected to expand as the interiors of continents become drier,
and erosion would worsen if soils dried out and violent storms became more
frequent.

Inevitably, a hotter world is likely to have less organic matter in its
soils. This will have tremendous consequences for farmers the world over,
particularly for those farming in the marginal areas of developing
countries. Critical regions of soil degradation and hence a high priority
for soil restoration and carbon sequestration (storing carbon in soil
securely so it is not immediately reemitted) include sub-Saharan Africa,
central and south Asia, China, the Andean region, the Caribbean, and the
acid savannas of South America.

Fortunately, something can be done, by managing soils to stem erosion and
retain more carbon. Carbon sequestration can potentially offset global
fossil fuel emissions by 5-15% each year, while raising yields. Once
sequestered, carbon can remain in the soil, for the next 20-50 years at
least, as long as appropriate management techniques are used.

One proven method of resisting erosion, restoring soil fertility and
boosting crop productivity is the use of organic compost. Compost is a
natural fertilizer, supplying soils with vital plant nutrients, and aiding
them to retain water and air. It restores soil carbon, crucial in
maintaining consistent yields through improvements in water and nutrient
holding capacity, soil structure and biotic activity. Compost improves soil
texture and structure, and helps control weeds, pests and diseases.

The implications of practices such as composting could be enormous for food
security. According to Rattan Lal of the Carbon Management and
Sequestration Centre at Ohio State University, a one tonne increase of the
soil carbon pool in degraded soils may increase crop yield by 20 to 40
kilograms per hectare (kg/ha) for wheat, 10 to 20 kg/ha for maize, and 0.5
to 1 kg/ha for cowpeas. In Ethiopia, farmers using compost increased yields
for various food crops, sometimes doubling or even tripling yields. The
yields from using compost are comparable, and often higher, than those from
chemical fertilizer.

Already, agricultural experts are urging Malawian subsistence farmers to
use organic compost, instead of manufactured fertilisers. Samuel Saka,
agricultural development officer for Nkhunga extension planning area in
Nkhota-Kota district in central Malawi said, "Based on the successful
demonstration plots we had, many farmers have started implementing this
method and the results speak for themselves - high maize yields."

A nationwide campaign is being promoted, as prices of manufactured
fertilisers are skyrocketing, putting them beyond the reach of most
Malawian subsistence farmers. As compost is affordable and can be prepared
from a combination of readily available material such as dry leaves, grass,
maize stalks and other biodegradable substances, it can be made and used by
poor farmers. There is no need to borrow money, so farmers do not have to
take credit and get into debt as they often do when using chemical
fertilizers.

The materials to make compost are mixed with soil and water, then left to
decompose for some time. The heat generated during the process destroys
most weed seeds, fungal diseases, parasites and pests. Although farmers do
have to invest time and labour into making good compost, the rewards are
worth the effort. The positive effects of compost on yields last for two or
more growing seasons, so soil given compost in one year need not be treated
again the next year.

Other strategies exist for combating soil degradation, and should be used
together with compost. For example, in developing countries, sowing cover
crops, using green manures and crop residues, and planting trees have
restored soil fertility and stemmed erosion. In general, recommended
strategies to rehabilitate degraded soils and increase soil carbon are also
sustainable agricultural practices. The combined benefits of restoring
soils, increasing yields and helping limit climate change are too important
to ignore.






  • [Livingontheland] Restoring Degraded Soils a Matter of Urgency, Tradingpost, 01/31/2008

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