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Irrigation
Irrigation is the artificial application of water to land for the purpose of agricultural
production
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The key to maximizing irrigation efforts is uniformity
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Deciding which irrigation systems is best for your operation requires a knowledge of
equipment, system design, plant species, growth stage, root structure, soil composition, and land
formation
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Losses of water will occur due to evaporation, wind drift,
run-off and water (and nutrients) sinking deep below the root zone
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Types of irrigation
Various types of irrigation techniques differ in how the water obtained from the source is
distributed within the field
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Sl
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1
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b
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d
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3
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Irrigation methods
Surface
Flooding
Border
1
...
Contour
3
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Rectangular
2
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Straight
2
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Surface Irrigation
Surface irrigation is the oldest and widely used method of water application to agricultural
land
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A flow is introduced at upper edge of the field
which covers the field gradually
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In
addition, other factors such as field slope, surface roughness, and the geometry or shape of the
flow cross-section also influence advance rate
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Water is applied either the entire field (uncontrolled flooding) or part of the field (furrows,
basins, border strips)
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In doing so it may be
essential to use more than one method of irrigation in an area or a given farm
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Fig
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Surface irrigation methods can also be divided into the following two groups
1
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Controlled Surface Flooding
30
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1Uncontrolled Surface Flooding or Flooding
It consists of applying water to the field without any bunds to guide the flow of water wetting
the soil surface completely
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Sometimes it is also adopted in the initial stages of

land development
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, rice, low value pastures, lawns and millets etc
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No land levelling & land shaping required
2
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Less skill required by irrigator
Disadvantages:
1
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Low irrigation application efficiency
30
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2 Controlled Surface Flooding
30
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2
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In some cases (ring basin) the plot may also be circular
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However, it is particularly useful on fine textured soils with low infiltration and
percolation rates so that the water is retained on the surface and in the root zone for a longer
period of time
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This method is most
commonly used for irrigating crops like groundnut, finger millet, sorghum, vegetable crops etc
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These are generally tuber and root crops like potato,
cassava beet and carrot
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Basins are mainly of two types:
1
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Ring basin (circular in shape)
30
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2
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1 Check Basin
The size of check basins may vary from one meters square, used for growing vegetables and
other intensive cultivation, to as large as one or two hectares or more, used for growing rice
under wet land conditions
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Check basins can be further divided into rectangular and
contour types
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Water can be applied uniformly
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Even small streams can be used for irrigation of crops efficiently
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Simple and cheap when equipment is used for constructing bunds

Disadvantages:
1
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2
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e
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3
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More labour is required for field layout and irrigation
30
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2
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2Ring Basin Method
This method is a modification of check basin method and is suitable for sparsely grown orchard
crops and cucurbits
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These basins are suitably connected to
irrigation conveyance channels in such a way that either each basin is irrigated separately or a
group of basins are irrigated at once by flowing water from one basin to another through interconnections
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High irrigation application efficiency can be achieved with properly designed system
2
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High labour requirement
2
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Limited to relatively uniform lands
30
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2
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Irrigation water is released into each strip connected directly to irrigation channel
situated at the upstream end of the border strip
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After sufficient water is applied to one strip, the irrigation stream is turned into
another strip
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03%)
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Two types of borders are formed:
1
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These are preferred when fields
can be levelled or be given a gentle slope economically
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Contour Border

These are formed across the general slope of the field and are preferred when land slope
exceeds the safe limits
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Advantages:
1
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Provides uniform wetting of soil profile
3
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Requires relatively large water streams for quick advance of water to minimize deep
percolation losses at the upper end of the border strip
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Wastage of water by deep percolation in coarse textured soils
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2

Furrow Irrigation Method

Furrow irrigation system is primarily used for vegetables
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It has advantage that water is applied only
in furrows instead of being applied on the whole field
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Infiltration occurs laterally and
vertically through the wetted perimeter of the furrow thus the root zone of the crops gets the
desired moisture
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Based on their size and spacing furrows may be classified as deep furrows and corrugations
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5 to 12
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Corrugation irrigation
consists of running water in small furrows called corrugation which direct the flow down the
slope
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It is commonly used for irrigating non-cultivated crops like small grains and
pastures growing on steep slopes
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Fairly high irrigation application efficiency among surface irrigation methods
2
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Low evaporation losses
Disadvantages;
1
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Possibility of intra-furrow soil erosion
3
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Moisture
moves upwards towards the land surface through capillary action to meet requirements of the
crops in plant roots
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Water may be obtained from
wells, streams, lakes etc
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Open ditches are preferred because they are relatively inexpensive and suitable for
all types of soils
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Sub-surface irrigation
requires little field preparation and labour
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The irrigation water is essentially required to be of good quality to prevent excessive soil
salinity
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The use of sub-irrigation is limited because it requires certain soil condition that is the soil
is permeable in root zone, underlain by an impervious horizon or high water table
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Ground slope is moderate
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, which raises the water
table to a uniform depth below the ground surface over the entire area,
(vi) Availability of adequate outlet for drainage of the area so irrigated particularly in humid
areas,

(vii) Subsoil water table is within 2 to 3 m below the ground surface, (viii) Topographical
conditions are uniform, and
(ix) Soil is capable of lifting moisture from the water table to the root zone
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The efficiency of water use depends on soil
characteristics, topography and operation and maintenance management
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Sprinkler Irrigation
The sprinkler irrigation is one of the pressurised irrigation methods, in which water is sprayed
into the air and fall on the ground surface somewhat resembling rainfall
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The pressure
created by the pump, which causes the water to flow out through the sprinkler nozzle
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With careful selection of nozzle sizes and
spacing, sprinkler pipe spacing and operating pressure the amount of irrigation water required
to fill the crop root zone can be applied nearly uniform at the sprinkling rate to suit the
infiltration rate of soil
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The
pipes need to be flexible, crack and impact-proof, capable to sustain the desired pressure and
temperature; and durable
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•

Successfully irrigate high permeable soils that are difficult to irrigate using surface
irrigation methods
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•

Lands having steep slopes and erodible soils and undulating terrain that would be too
costly to make smooth for use
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•

Suppressing dust during to dust storm during summer and cooling the local
environment
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Sprinklers spread water as “rainlike” droplets over the land surface
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Mainlines
convey water from the water source to the sub-mains and laterals
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36
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shows the

components of a portable sprinkler irrigation system
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1
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A pump unit
3
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Fertiliser application units and filters
5
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Sprinkler head
7
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i) Water Resource: The information on quantity and quality of available water resources is
required for design of sprinkler system
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This
information is particularly required for deciding whether the entire area of the proposed field
or the portion of the area of the field can be irrigated
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The water from the source (ground water / surface water) is pumped under pressure to sprinkler
system
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A high speed centrifugal or turbine
pump can be used for operating sprinkler irrigation to individual fields
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For pumping water from deep wells or more than eight meters, a submersible
pump is used
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iii) Pressure gauge: It is used to measure operating pressure of sprinkler system
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5 kg/cm2)
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Fertiliser Application Unit: Soluble chemical fertilizers can be injected into the
sprinkler system and applied to the crop
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A venturi injector is connected with the main
line, which creates the differential pressure to suck fertilizer solution to flow in the main line
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Filters: Filters are used to filter the suspended particles and debris flowing with water
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Main line
conveys water from the source and distributes it to the submains
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Aluminium or PVC or HDPE pipes
are generally used for portable systems, while steel pipes are usually used for center-pivot
laterals
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vi) Sprinkler Head: Sprinkler head distributes water uniformly over the field without
generating runoff and loss due to deep percolation
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The rotating type can be adopted for a wide range of application rates and spacing
(Fig
...
5)
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Pressures
ranging from 16 to 40 m head are considered to be the most practical for normal uses
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Essentially a coupler should provide: a) a reuse and flexible connection, b) not leak at the joint,
c) be simple and easy to couple and uncouple, and d) be light, non-corrosive, durable
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6
shows different types of sprinkler fittings and accessories
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a) Water meters: It is used to measure the volume of water delivered in to the system
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b) Flange, couplings and nipples are used for proper connection to the pump, suction and
delivery
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They are used as per requirements
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The studies conducted in different parts of India showed that this method can save
water to the extent of 30 per cent compared to surface irrigation method
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(ii) Frequent application of water and depths matching with the water requirement of crops
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(iii) As there is no overland flow, water is not moved on land surface, this method is suitable
for irrigating all types of soils except very heavy clay
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(iv)It is suitable for oil seeds and cereal and vegetable crops
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(vi)There is no necessity of making bunds, ridges, field channels etc
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The land used for these construction is saved and can be used for crop cultivation
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(viii) Chemicals and fertilizers can be applied along with water
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(x) The damage on vegetables, citrus, apple, mango, litchi, and other fruit crops to fog, frost
and high solar radiations can be protected
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(xii) Plant protection chemicals can be applied to distant part of plant, which is not possible in
other methods of irrigation
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(ii) The fine-textured soils which have a low infiltration rate cannot be irrigated efficiently
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(iv) High operational costs due to higher energy requirements
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However, research experiments on paddy
crops have given promising results
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(vii) Water with impurities and sediments may damage the system components

Drip Irrigation
Drip irrigation was discovered by Israel country
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The pressure that need to
maintained at the emitters, also called as operating pressure, is usually small operating pressure
(20 to 200 kPa) compared to the operating pressure required at the nozzle or sprinkler of the
sprinkler irrigation system
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5 to 12 ltr/hrs depending
on the soil type, discharge available at the source and the area to be irrigated
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The components of the drip irrigation system are classified into following principal
categories:
a) Water source: Water sources such as river, lake, reservoir/tank, well, canal water supply or
connection to a public commercial or cooperative water supply network can be used
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b) Pump and prime mover: The pressure necessary to force water through the components
of the system including fertilizer tank, filter unit, mainline, sub main, laterals and provide at
the emitters at the desired pressure is obtained by a pump of suitable capacity or the overhead
water tank located at suitable elevation
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The sprinkler
system is operated at the pressure to apply the desired depth of water and ensure application
uniformity (2
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d) Pipe network: Mainline, submains and manifolds (feeder pipes) and laterals
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f) Control devices: Valves, flow meters, pressure and flow regulators, automation equipment,
backflow preventers, vacuum and air release valves, etc
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Media, screen and disc
filters
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Pressurized tank, venture injector, injection pump
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Improved Plant Growth and Crop Yield: It has been reported that drip irrigation increases
the yield from 10 to 60% depending upon soils and crops over conventional methods of
irrigation
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Energy Saving: Because of high irrigation efficiency, less amount of water is required to be
applied and hence less time is required to supply the desired quantity of water and therefore
this, method saves energy
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Weed Control: In drip method, due to partial wetting of soil, weed infestation is very less in
comparison to other methods of irrigation
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There by reducing the operational costs even
upto the extent of 50%
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As the irrigation requirement of this method is almost reduced by more than 50%, the
use of water with salt loads cause the less salt accumulation compared to surface irrigation
methods
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No Soil Erosion: As water is not moved over the land surface, there is no soil erosion due to
drip irrigation
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Only land smoothening will suffice
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Adaptability to Application of Mulches: The drip irrigation method wherein the drippers can
be placed below the mulch cover is suitable for the situations where the mulches are required
to be used
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Extensive Maintenance Requirement: Clogging can adversely affect the flow rate and
uniformity of water application, increased maintenance costs as it becomes necessary to check,
replace or reclaim the clogged emitters
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Rodents, rabbits, dogs, etc
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Salinity Hazards: Although drip system can be used under saline conditions, it must be
managed properly
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High Skill Requirements: High skill is required for designing, installation and subsequent
operation
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has been
necessary
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These irrigation methods describe
above

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