Newsletter and Technical Publications
<Sourcebook of Alternative Technologies for Freshwater Augumentation
1.4.5 Porous Clay Pots and Pipes for Small-scale Irrigation
Porous clay pots and pipes are a means of water application that conserve
water by applying water directly to the roots of plants, thereby limiting
evaporation losses (Figure 26).
Both clay pipes and clay pots can be homemade; most are installed by
individual householders. The pipes are joined to form tubes of 250 mm in length
with an inside diameter of 75 mm. The pipes are placed along the entire length
of the beds by laying them end-to-end in a levelled trench. At one end, a right
angle fitting is attached and an upright section of pipe installed. The trench
is then backfilled with soil to a depth of 100 to 200 mm, depending upon the
soil type. Water is poured into the porous pipe through the upright pipe. Each
plant bed is about 3 to 6 m in length. The water seeps into the root zones
through the joints between the individual pipes, or through the pipe walls if
unglazed clay pipes are used.
|Alternatively, porous pots (made of unglazed clay) are buried in the
soil up to their necks next to the plants or between plant rows at
intervals of 300 mm. Water seeps from each pot through the pores and forms
a wetted zone. Varying the frequency of filling, the size of the pots and
the spacing between pots affects the watering process. Selection of the
most suitable size of pot and its placement is governed by the type of
Figure 26. Clay pipes and clay pots.
Extent of Use
Adoption is fairly limited, possibly due to the fact that the initial stages
are very labour-intensive. Trials in the dry areas of Chiredzi, Zimbabwe, have
shown that communities are interested in this technology.
Operation and Maintenance
Once the systems are installed, there is very little maintenance required.
Operation is quite simple.
Level of Involvement
Farmers, researchers and extension workers must work together to implement
this technology. Communities can construct and operate the system. However,
government officials and/or NGOs may have to work with pipe/pot manufacturers to
ensure availability of supplies of suitable pots and pipes. Extension workers
can assist farmers in pipe/pot placement for best effect and at depths/densities
best suited for various types of crop.
Effectiveness of the Technology
It was found, during the replicated trials, that water savings varied from 11
to 28% of the water used with traditional irrigation.
Since this technology uses clay pots and clay pipes that are locally
manufactured, the costs are normally low. The major cost is the cost of labour,
which is estimated at approximately $40/ha in Zimbabwe.
This technology is most suitable for dry areas with less than 500 mm
rainfall/year. With this technology, it becomes possible to save water and
irrigate small vegetable gardens in rural areas. Communal farmers, especially
women, can manufacture the pots/pipes without having to develop special skills.
Porous clay pots and pipes conserve water and enable crops to grow in areas
where they otherwise could not grow.
Material for clay pipes and pots, and local skills for pot-making, are
readily available at negligible cost. This method provides a uniformly-wetted
area, and, because water is applied at depth, often helps to reduce any weed
problems - weeds generally have shallow root systems that are not well-served by
this technology. Also, pots can be placed next to individual plants. Once the
technology is installed the system can be used for several seasons.
The initial labour required to manufacture the pots/pipes and install this
technology is very high. The use of clay pots can be more labour intensive than
traditional methods of watering crops, and may have difficulty in coping with
providing adequate water for crops with high water requirements. Also, the
porosity of pots decreases with time, and they have to be replaced at intervals.
Pot lifespans are greatly reduced by the use of turbid water with a high silt
and clay content. The silt accumulates in the pores, effectively sealing the
The technology is culturally acceptable.
Further Development of the Technology
There is need to market this technology, especially in areas of low rainfall
(less than 500 mm/year).
Lowveld Research Station, Post Office Box 97, Chiredzi,