Agriculture Reference
In-Depth Information
saw something special 20 years ago on the Ca Mau Peninsula of southern
Vietnam. Here, saline water and problem soils have been turned to farmers'
advantage by adopting rice-shrimp systems combined with novel methods
of water and soil management. The peninsula has no sources of freshwater
except rain and very deep wells, but it has mangroves, fields and an
abundant marine environment. On a field trip with a group of students,
Xuan stopped at Long Dien Dong village to show a soil profile. Pointing
to the bluish-grey soil horizon below the brown topsoil, he told farmer
Ba Sen: 'If you let this soil dry, it will become acidic, and nothing can be grown on it.
But when the field is permanently wet, even with saline water on the surface, your soil
fertility will be maintained forever.' But to Ba Sen, this was not news at all. He
had accidentally discovered a sustainable practice of managing the
potentially acid sulphate soil four years before, and had even written it in
a will to his eldest son.
The rice field is prepared during the start of the rainy season. Saline
water is let out of the field and the soil is flushed by the rainwater. Initially,
soil salinity might be high, but it falls after a few rains. Seedlings are
prepared in nurseries in the early rainy season, and fields are cleaned of
weeds and algae, without tillage. Seedlings are transplanted at the age of
30 to 40 days at the end of July, and Ba Sen gets a yield of about 4 tonnes
per hectare. After harvest, and while the soil is still wet and river water
not yet saline, farmers allow river water to enter the field to raise shrimps. 32
The first shrimp harvest is after the end of the rainy season, after which
the field is prepared for another crop of shrimp. This time, saline water
is taken into the field at high tide. Water management is crucial, and water
is exchanged once or twice a week in order to create a continuous flow in
the field. Stocking of shrimps is carried out between January and March,
and these are fed with cassava, coconut meal, milled rice and fishmeal,
yielding (during April to June) nearly 200 kilogrammes per hectare.
What is clever about this system is that Ba Sen is getting much more
from rather unpromising resources than anyone could have expected. He
has spoken at local meetings and international conferences, and the
practices have spread throughout Ca Mau. The result is that mangroves
are being sustained, marine resources valued, and agriculture's productivity
increased - all because an integrated and balanced system of management
has been developed in which the total is better than the sum of its parts.
As Vo-Tong Xuan puts it:
The creative and intelligent people of Ca Mau now have a rich experience in
exploiting their saline water environment. They do not see it as a constraint to their
development, but on the contrary they take advantage of it, a valuable advantage which
will lead Ca Mau to prosperity.
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