By PHILIP BRASHER, AP Farm Writer
WASHINGTON
(AP) - Scientists who studied the world's farmland with satellite
maps found widespread damage to soil quality and said irrigation
is draining underground water supplies faster than they can be
replenished.
Either farmers
switch to farming methods that improve soil conditions and use
less water or they won't be able to feed the world's growing population,
according to the report released Wednesday by the International
Food Policy Research Institute.
"The
basic story is that agriculture is being pretty successful at
keeping the world in food. It's been somewhat less successful
in nurturing the natural resources that underpin that production
capacity," said Stanley Wood, the report's lead author.
About 16 percent
of the world's farmland is free of fertility problems, or "constraints,"
such as chemical contamination, acidity, salinity or poor drainage,
the report found.
In parts of
Asia, as little as 6 percent of farmland is free of such problems.
North America has the largest share of the best land at 29 percent.
Aluminum contamination
is high enough on 17 percent of the farmland worldwide that it's
toxic to plants, and salt deposits are a significant problem on
irrigated land. Nearly 4 million acres of farmland is lost to
excessive salt every year, or about 1 percent of irrigated area
worldwide, the report said.
Depletion
of organic matter in soil also is widespread, reducing fertility
and moisture retention and increasing emissions of carbon dioxide
into the air, which is believed a factor in global warming, the
report said.
Scientists
need to find ways to increase food production without "major
increases in the amount of new land under cultivation, which would
further threaten forests and biodiversity, and without resorting
to unsustainable farming practices," said Ian Johnson, a
vice president of the World Bank and chairman of the Consultative
Group on International Agricultural Research.
The world's
population is expected to grow by 1.5 billion over the next 20
years.
Biotechnology
could help boost production, if crops were genetically engineered
to need less water and to grow in poorer soil, but that alone
won't be enough, Wood said.
In many areas,
the problem is that there isn't an economic incentive for farmers
to change the way they farm.
In Kenya,
the soil is so poor that corn yields are 20 percent or less of
what they are in the American Midwest, partly because farmers
can't afford to leave stalks and other plant debris in the soil
to improve its fertility. They feed the plant material to animals
or use it as fuel.
Chemical fertilizers
aren't effective unless sufficient organic matter remains in the
ground, Wood said.
Poor transportation
systems also make it difficult for poor farmers to sell crops
or obtain the chemicals they need.
The report
also cited "an urgent need" to use irrigation water
more efficiently. Irrigation accounts for 70 percent of the fresh
water withdrawn, and 30 to 60 percent is returned for downstream
use, the report said.
The report
is among a series of studies being done on the condition of various
ecosystems, the forests and marine areas.
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