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New irrigation
technology holds big promise
By
Mohammad Aslam, Dr Zahid Hussain & Qurban Hussain
Most of the land area of Pakistan is classified as arid to
semi-arid because rainfall is not sufficient to grow
agricultural crops, forest and fruit plants and pastures.
About 68 per cent of the geographical area of Pakistan lies
under annual rainfall of 300mm, 80 per cent of which is
concentrated in July-Sept; whereas about 24 per cent of this
lies under annual rainfall of 301-500mm. This leaves only 8
per cent of geographical area where annual rainfall exceeds
500mm.
To meet the crop water requirement, supplemental irrigation is
essential for crop production. The overall agricultural
production depends up on the efficient use of scarce water
resource out-side the Indus basin. This objective is
achievable by adoption of pressurized irrigation (sprinkler,
trickle and hosefed) in the water scarcity areas of Pakistan.
Sprinkler irrigation systems: maximize efficiency and
minimize the labour and capital requirement and, at the same
time, maintain a favourable growing environment for the crop.
Hence they are recommended for varying soils, topography and
crops. Flexibility and efficient water control have permitted
a wide range of soils to be irrigated that have surface water
applications, thereby allowing more land to be irrigated.
Thus, million of acres of land in the USA, which was
previously suitable only for dry land farming, is being
irrigated by sprinkler systems today with higher yields.
Similar beginning has already been made in Pakistan to provide
supplemental irrigation to barani lands and irrigated areas
outside the Indus basin where water is at premium.
Experiments were conducted on wheat crop at NARC for
supplemental irrigation through sprinkler system. The yield of
wheat crop was increased from 3.04 tons/hectare to 6.60t/ha by
applying supplemental irrigation of only 135mm as compare to
rainfed whereas only rainfall of 354 mm was received during
the entire crop growing season.
The supplemental irrigation of 10 mm at of time of pre-sowing
(rouni) enhanced the wheat production from 3.04 t/ha to 4.56
t/h as compared to barani (rainfed) condition. Locally
manufactured raingun sprinkler irrigation systems can be used
with discharge of even less than 3 litres per second, whereas
at least 14 litres per second is required for surface
irrigations to a field of around 0.5 acres. Applications of
net-irrigation is possible even to replenish one-day
requirement of 1-5mm in contrast to surface irrigations where
at least 75mm are required to cover the field. Even an
application of 75mm is not possible by surface irrigation at
the time of first irrigation where soil is tilled and
infiltration is high. It means that net water application
required is more than 75mm.
Sprinklers often have multiple uses. The same equipment can be
used for irrigation, crop cooling, frost control and
application of pesticides, herbicides and fertilizers. Many
farmers in barani areas, which annually receive more than
enough precipitation to satisfy crop requirements, are
installing supplemental irrigation systems. This is due to the
fact that usually there is no rain at right time in the
required quantity. Timely irrigation at a critical crop growth
stage can offer more than double yield by applying only a few
centimeters of water. In areas where labour and water costs
are high, sprinklers can be the most economical way to apply
water. Sprinklers can also be used to increase the quantity
and quality of fresh vegetables and fruits for markets, where
colour and quality are given importance.
Trickle irrigation is a system whereby water and
fertilizers are applied directly to individual plants in a
field instead of irrigating the entire area. For orchards or
widely spaced crops, it is accomplished with small diameter
laterals running along each plant row. Emitters are attached
to the lateral for supply of water to each plant to meet its
requirement. Water can be provided to a plant on a low tension
and high frequency basis. Hence creating a near optional soil
moisture environment. Thus water use efficiency can be
increased by 50 per cent or more compared with surface
irrigation system.
Trickle irrigation system is labour-, water- and
fertilizer-efficient. No investment is involved in land
levelling, but there are some maintenance requirements. A
major economic factor is the utility of the trickle system in
providing cost-effective means of fertilizer and pesticides
applications.
Economic considerations favour the use of trickle irrigation
for fruit trees and vegetables of high value grown in specific
conditions such as in tunnels. The potential areas for
installation of these systems include:
- Balochistan where high value crops
are grown and water is at premium.
- Para-urban agricultural areas where
high value vegetables, fruits, cut-flowers and nursery
plants are grown.
- Undulated sandy lands in Thal, Thar
and Cholistan deserts, which have groundwater of reasonable
quality.
- Sandy and undulating riverine areas
in NWFP, the Punjab and Sindh provinces.
- Sandy high areas within Indus basin,
which require huge investments for surface irrigation.
- Fringe areas or where water is either
saline or extremely scarce.
- Northern Areas and barani lands,
where high-value crops are grown on steep slopes and/or with
very coarse textured soils.
- Areas of inland basin having very
thin layer of fresh ground-water - that is, Sindh and
southern Punjab.
Sprinkler and trickle irrigation systems are now being
introduced in the country. They have been installed in several
demonstration plots in the country. Furthermore, progressive
farmers are also installing these systems in collaboration
with Water Resources Institute (WRI), National Agricultural
Research Centre (NARC), Islamabad. All the components are now
locally manufactured in collaboration with the pump and
plastic industry in Lahore.
WRI-NARC, in collaboration with a local enterprise, have
developed a range of sprinkler system using locally available
materials and technology. The estimated cost of this sprinkler
irrigation system is in the range of Rs10,000-12,000 per acres
for a system of at least five acres using diesel-operated
pumps.
Major limitations for large-scale introduction of pressurized
irrigation systems were availability of services to meet
farmers need for design and installation of these systems,
farmers' training and provision after such services, WRI-NARC
has established an Irrigation Service Support Programme (ISSP),
for providing support to farmers in the installation of these
systems and already extended these services to more than 25
farmers and a number of institutions. Farmers are bearing 100
per cent cost of these systems and the demand is so high that
the WRI is not in a position to extend timely services to all
the clientele.
The farmers from any part of Pakistan can contact WRI-NARC for
designing of trickle or sprinkler system. They have to fill a
form and return it to WRI-ISSP-NARC. After consultations with
farmers, survey, mapping and designing of the system is
conducted free of cost.
Dr Zahid Hussain is CSO/director & Mohammad Aslam and
Qurban Hussain are senior engineers, Water Resources
Institute, NARC, Islamabad.
Courtesy Dawn
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