Agen 159 lec 2

WELCOME
Md. Nurul Kadir
Lecturer
Department of Agricultural Engineering

MAIN FEATURES
IRRIGATION AND ITS METHOD

Definition of Irrigation
Irrigation may be defined as the application of water to
soil for the purpose of supplying the moisture essential
for plant growth.
Therefore, need for irrigation is as follows :
 Where, Rainfall is not sufficient to supply crop
water needs
 Where rainfall is not uniformly distributed to
supplement the crop requirement
 If there is variable crop water requirement

1.Irrigation supplies moisture to the soil essential for, germination of seeds
and various growth processes of crop.
2.Cools the soil and the surroundings thus making the environment more
favorable for crop growth.
3.Washes out or dilutes salts present in the soil.
4.Softens the clods and thus helps in tillage operations.
5.Enables application of fertilizers.
6.Reduces the adverse effects of frost on crops.
7.Ensures crop success against short duration drought
Functions of Irrigation

Irrigation maximizes crop productivity and thereby ensures food security
It makes agricultural industry profitable and competitive
 Irrigation improves land productivity and value of land
Promotes employment generation and lively hood of society
Main conveyance/irrigation canals can be used for flood protection, recreation and
navigation.
It promotes fish and wildlife preservation
Rapid development of irrigation facilities through construction of multipurpose dams
enhances hydroelectric power generation.
Irrigation promotes a whole array of agro-based industries which are drive engines of
economy.
Direct/indirect benefits of Irrigation

TYPES OF IRRIGATION
1. SURFACE IRRIGATION
2. SUB-SURFACE IRRIGATION
Surface irrigation
In the surface methods of irrigation, water is applied directly to the soil surface from
a channel located at the upper reach of the field. Water may be distributed to the crops
in border strips, check basins or furrows.
Subsurface irrigation
In sub-irrigation, water is applied below the ground surface by maintaining an artificial
water table at some depth, depending upon the soil texture and the depth of the plant
roots. Water reaches the plant roots through capillarity action.

Irrigation water can be applied to the land in several different ways, and the
choice among alternative irrigation methods, depends upon many factors,
including:
• economics
• crop type
• soil type
• water availability and quality
• farming practices
• legal considerations and others

METHODS OF IRRIGATION
• SURFACE IRRIGATION
• SUB-SURFACE IRRIGATION
• SPRINKLER IRRIGATION
• TRICKLE (DRIP) IRRIGATION

Uncontrolled surface flooding
 It consists of applying water to the field without any bunds to guide the flow of water
wetting the soil surface completely.
 This method is most commonly used for irrigation of crops sown by broadcasting
method viz., rice, low value pastures, lawns and millets etc.
Advantages
1. No land levelling & land shaping
2. Low labor and land preparation costs
3. Less skill required by irrigator
Disadvantages
1. Applied water is lost by deep percolation &
surface runoff
2. Low irrigation application efficiency

Controlled flooding
Check basin method
In this method the field is divided into square or rectangular plots of
4 to 4000 m2 guided by bunds on all the sides. v
Advantages
1. Water can be applied uniformly.
2. Even small streams can be used for irrigation of crops efficiently.
3. Simple and cheap when equipment is used for constructing bunds
Disadvantages
1. Unless the land is levelled, distribution of water in plot is uneven.
2. Considerable area is lost under field channels and bunds i.e.
nearly 30% of area.
3. Bunds interfere in working of inter-cultivation equipment
4. More labour is required for field layout and irrigation

Ring basin method
This method is a modification of check basin method and is
suitable for sparsely grown orchard crops and cucurbits.
Advantages:
• Effective leaching
• Maximum use of seasonal rainfall
• High application efficiencies
Limitations:
• Soil crusting
• Unsuitable for crops that cannot accommodate
inundation.
• Application efficiency is comparatively high.

Border strip method
The cultivated field to be irrigated is divided into a number of long parallel
strips, generally 3 to 15 m in width and 75 to 300 m in length separated by small
border ridges or low dykes of about 15 cm high, laid out in the direction of the
slope.

Furrow irrigation method
o Furrow are narrow field ditches, excavated between rows of plants and carry water through
them
o Spacing of furrows is determined by proper spacing of the plants.
o Furrows vary from 8 to 30 cm deep and may be as much as 400 meters long
o Deep furrows are widely used for row crops.
o Small shallow furrow (called corrugations) suitable for irregular topography and close growing
crops such as meadows and small grains.
o Water diverted into the furrows by using rubber hose tubing.
o Hose prevents the necessity of breaking of the ditch bank and provides a uniform flow into
the furrow.

Advantage:
Only about one-fifth to one-half of the land
surface is wetted by water. So, it results in less
evaporation,
less pudding of soil.
Disadvantages:
Excessively long furrows may result in too much
percolation near upper end and too little water near
the down-slope end.
It involves high initial cost and salt accumulation in
the ridges.
It is suitable for row crops (like potatoes, groundnut, sugarcane etc.)
and for medium to moderately fine textured soil.

Traditional methods
Levee: holds the
water back
Canal: allows the water
to be brought to drier
areas
Dam: controls the
flow of water

Sprinkler irrigation method
o Water is applied to the soil in the form of a spray through a network of
pipes and pumps.
o It is kind of an artificial rain and gives good results
o It is a costly process and not widely used in our country.
o It can be used for all types of soils and for widely different topographies
and slopes.
o It fulfills the normal requirement of uniform distribution of water.
 This method can be used for almost all crops
(except rice and jute) and on most soils.
 It is best suited to sandy soils that have a high
infiltration rate.
 It can be applied to any topographic conditions
without extensive land preparation.

Advantages of sprinkler irrigation:
o Seepage losses, which occur in earthen channels of surface irrigation methods, are completely
eliminated. Moreover, only optimum quantity of water is used in this method
o Land leveling is not required and thus avoiding removal of top fertile soil, as happens in other
surface irrigation methods.
o No cultivation area is lost for making ditches results in increasing about 16 % of the cropped area
o The water is to be applied at a rate lesser than the infiltration capacity of the soil, and thus avoiding
surface run off.
o This method leaches down salts and prevents water-logging or salinity
o It is less labor oriented and hence useful where labor is costly and scarce.
o Up to 80% of applied water can be stored in the root zone of plants.
o Fertilizers can be uniformly applied, because they can mixed with irrigation water
Limitations of sprinkler irrigation:
o High winds may distort sprinkler pattern, causing non-uniform spreading of water on the crops.
o In areas of high temperature and high wind velocity, considerable evaporation losses of water my
take place.
o They are not suited to crops requiring frequent and larger depths of irrigation, such paddy.
o Initial cost of the system is very high, and the system requires a high technical skill
o A constant water supply is needed for commercial use of equipment
o Only sand and silt free water can be used, as otherwise pump impellers lifting such waters will get

Drip irrigation
o It is the latest field irrigation technique (also called trickle
irrigation)
o Irrigation water is applied by using small diameter (12 to 32
mm) plastic lateral lines.
o The lateral lines contains some devices called „emitters‟ at
selected spacing to deliver water to the
soil surface near the base of the plants.
o It is best suited for widely spaced plants, salt problems and
for areas with water scarcity.
o In this method, water is slowly and directly applied to the
root zone of the plants for minimizing
the losses by evaporation and percolation
o This method is being used for small nourishes, orchards, or
gardens.

Benefits:
 Conventional losses such as deep percolation, runoff and soil water can be minimized by applying
a volume of water approaching the consumptive use of the plants.
 Small area is wetted thereby reducing weed growth, insects and diseases etc.
 Soil crusting and interference with harvesting is minimized.
 Greater crop yield and better quality can be obtained.
 For widely spaced like fruit trees, the system may be even more economical than sprinkler
method of irrigation.
Disadvantages:
 High initial cost of the deep irrigation equipment sometimes limits its use to orchard and
vegetables in water scarcity areas.
 Clogging of emitter may disrupt the irrigation system.
 Plastic pipes may damaged by rodents.
 Wind erosion can harm the pipes.
 Like the sprinkler method, drip irrigation permits the simultaneous application of fertilizers
through the system.
 When compared to the sprinkler system, the drip method operates on much lower line a saving
in energy requirements.

REFERENCE
•S.K.GARG, IRRIGATION ENGINEERING AND
HYDRAULIC STRUCTURES.

Agen 159 lec 2

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