Agro-Tech Book - Agriculture Support Programme

A “DEEP WELL PUMP” is a means of raising water from a well using rubber washers on a rope
in a pipe. Turning the handle at the top of the well causes the rope with washers on it to
pass up the pipe lifting the water with it. The out�ow can be diverted into a furrow. Do not
try to put the water into a pipe on the surface since no pressure can be generated by this
kind of pump at the outlet.
The pump can deliver about 5,000 litres per hour to a head of 4 metres.
Wind powered pumps - windmills
Windmills cost around US$2,500 and will pump from a borehole or a well. They must be
placed where there is enough wind and they will pump only when there is wind, so they should
deliver into a tank so as to catch the water by night as well as by day. It is advisable to �t
them with a manually operated handle to pump even small amounts of water to keep seedlings
alive when there is calm weather.
A large windmill could irrigate up to 5 hectares if it is well placed for wind and water
source.
Windmills can be damaged by high winds in storms and so should be “locked” to prevent
rotation during storms.
Motorised pumps
Pumps with engines are usually “centrifugal” pumps using one or more “impellers” that spin
very fast to give pressure. There are also “mono” pumps for boreholes that operate on a
screw principle forcing water upwards through a pipe.
There are many different speci�cations for these pumps so farmers must to describe to
the sales agent what the needs are exactly in order to have the correct kind provided. The
agent will need to know:
the amount of money available to purchase the equipment
the size of the area to be irrigated
the type of soil (sandy-clay)
the elevation of the top of the water supply in relation to the elevation of the �eld
the �ow rate of the supply
the topography (contours/slopes) of the �eld
the range (rotations!) of crops to be grown
the availability (and distances) of ZESCO
E.E.O.A.
When a competent agent has all the above information, he can make sensible proposals to
the farmer who can then select a design which will suit him best. He can decide what kind
of irrigation system is to be used. Will it be �ood or drip or sprinkler because the different
pressure requirements will dictate what kind of pump is needed.
Standard pumps with petrol or diesel engines are useful for �ood irrigation or �lling tanks.
Check with neighbours to �nd their experience of pumps and see what is available in your
area. All pumps require spares so it is important that there is an agent nearby.
AGRO-TECHNOLOGY: Farming and Processing Equipment
5