Rome, Italy
December 19, 2007
High levels of arsenic in rice
could be reduced by applying improved irrigation management
practices in Asia, FAO said
today in a new report entitled Remediation of Arsenic for
Agriculture Sustainability, Food Security and Health in
Bangladesh.
Studies have shown that high concentrations of arsenic in soil
and irrigation water often lead to high levels of arsenic in
crops and are posing an increased food safety risk. At present,
twelve countries in Asia have reported high arsenic levels in
their groundwater resources.
“The problem of high arsenic levels in crops, particularly rice,
needs to be urgently addressed by promoting better irrigation
and agricultural practices that could reduce arsenic
contamination significantly,” said Sasha Koo-Oshima, FAO water
quality and environment officer.
“Arsenic-contaminated rice could aggravate human health when
consumed with arsenic-laden drinking water. The widespread
addition of arsenic to soils, for example in Bangladesh, is
degrading soil quality and causing toxicity to rice. Arsenic
contamination is threatening food production, food security and
food quality,” she noted.
Entering the food chain
Arsenic enters the food chain mainly through crops absorbing
contaminated irrigation water. Millions of shallow tube wells
have been installed throughout Asia over the last three decades
pumping water from contaminated shallow groundwater aquifers.
Contamination originates in arsenic-rich sediments of the Ganges
and Brahmaputra river that filters into groundwater water pumped
to the surface through millions of tube wells.
Bangladesh has the highest percentage of contaminated shallow
tube wells and an estimated 30 million people are dependent on
those wells for drinking water and irrigation. Of the four
million hectares under irrigation, 2.4 million ha are irrigated
with approximately 900 000 shallow tube wells. Approximately 95
percent of the groundwater extracted is for irrigation.
It has been estimated that water pumping from shallow aquifers
for irrigation adds one million kilogram of arsenic per year to
the arable soil in Bangladesh, mainly in the paddy fields. Rice
is the staple food in Bangladesh and it is consumed in large
quantities.
Raised beds
Planting rice in raised beds around 15 centimetres above the
ground and not in conventional flooded fields counteracted yield
losses and resulted in lower arsenic levels in crops and in the
soil, a pilot field study in Bangladesh conducted by FAO and
Cornell University revealed. In addition, the raised bed rice
buffers against floods and drought and serves as a measure in
climate adaptation.
“Raised beds are significantly reducing the exposure of rice
plants to contaminated irrigation water and are producing higher
yields,” Sasha Koo-Oshima said.
A related Cornell University project proved that between 30 and
40 percent less irrigation water is needed in raised-bed-
system. Fertilizers are also captured better – with the effect
that farmers will need less fertilizers. The raised-bed-system
represents a major shift in rice production but tests show that
farmers prefer the new approach due to visibly higher yields,
water savings, lower tillage and labour costs and production of
a safer crop.
Identifying and targeting rural areas that are worst affected by
arsenic contamination and further developing and extending the
raised-bed-system should become a main priority in order to
reduce the risk of arsenic contamination to human health, secure
food safety and production, Koo-Oshima said. |
|
