Rice cultivation using alternate wet and dry irrigation (AWDI)
Practical Action
The AWDI implies that rice fields are allowed to dry intermittently during the rice growing stage
rather than keeping the fields continuously submerged. Farmers can adapt their AWDI practices
to fit the soil type and availability of water and labor.
In AWD systems, flush irrigation is used to supplement rainfall as required. The field is
alternately flooded and non-flooded. This may be for the whole growing season or strategically for
the part of the season. The AWDI involves flooding the field (after a certain number of days have
passed) using irrigation water after the disappearance of ponded water. The number of days of
non-flooded soil can vary from 1 to more than 10 days.
It is believed that continuous submergence is often practiced to control weeds, thus minimizing
the use of herbicide and reducing the labor for weeding. However, the amount of labor spent for
these activities could be smaller in magnitude than those spent for other rice production
activities.
There are a few issues that can affect the implementing of AWDI such as little water control and
lack of a reliable water source. However, farmers can increase yields while reducing water demand
by combining AWDI with SRI (system of rice intensification) cultivation practices, described in
the Intensive Rice Cultivation technical brief.
How to implement AWDI?
• Using the field water tube, monitor the water
depth in the field
• After an irrigation application, the depth of ponded
water will gradually decrease over time. When the
water level drops to 15 cm below the soil surface,
apply irrigation and flood the soil with a depth of
around 5 cm
• Around the time of flowering, ponded water should
always be kept at 5 cm depth (to avoid any water
stress that could result in yield loss) from 1 week
before to 1 week after the peak of flowering.
• After flowering, during grain filling and ripening,
the water level can drop again to 15 cm below the
Figure 2: A field tube under flooded
conditions. Photo credit: Practical Action.
surface before re-irrigation
• AWDI could be started a few days after transplanting (or with a 10 cm tall crop in direct
seeding)
• If many weeds are present, AWDI can be postponed for 2-3- weeks until weeds have been
suppressed by ponded water
The threshold of 15 cm water depth (below the surface) before irrigation is called ‘Safe AWD” as
this will not cause any yield decline (since the roots of the rice plants will still be able to take up
water from the saturated soil and the perched water in the root zone).
In AWD, water savings are in the order of 15%, without any yield penalty. After creating
confidence, farmers may experiment by lowering the irrigation threshold level to to 20, 25, 30 cm
depth, or even deeper. Lowering the irrigation threshold level will increase the water savings;
some yield penalty may be acceptable when the water is scarce or when the price of water is high.
The groundwater in many irrigated areas is very shallow and may reach into the field water tube.
2