Irrigation Methods Guide

Irrigation
Vijitha Vikneshwaran
Lecturer(Temporary)
Faculty of Technology
University of Jaffna

Introduction
• Irrigation is the artificial application of water to the soil in
order to facilitate crop growth.
• It is used to assist in the,
growing of agricultural crops
maintenance of landscapes
re-vegetation of disturbed soils in dry areas
2

Importance of water in agriculture
• All the physiological processes of plants are directly or
indirectly influenced by water status of the plant
• Growth and development
• It is a constituent of protoplasm
• Maintenance of turgidity of cells
3

• Act as solvent of nutrients, photosynthates and other
substances
• Water is involved in hydrolysis of starch
• Work as reactant in many process (Eg: Photosynthesis)
• Act as hydraulic fluid permitting regulation of internal
pressure
4
Importanceofwaterinagriculture,cont

Necessity Of Irrigation
• Insufficient rainfall
• Uneven distribution of rainfall
• Improvement of perennial crop
• Development of agriculture in dry area
5

Benefits Of Irrigation
• Increase in crop yield
• Protection from famine
• Cultivation of superior crops
• Elimination of mixed cropping
• Economic development
• Hydro power generation
6

• Domestic and industrial water supply
• Possible to have multiple cropping
• Green manuring
• Cool the soil and atmosphere
• Wash out or dilute the salt in soil by leaching
• Softening of soil and tillage pan
7
BenefitsOfIrrigation,cont…

Ill Effects Of Irrigation
• Impaired soil aeration
• Rising of water table
• Formation of marshy land
• Dampness in weather
• Loss of valuable lands
8

• Imbalance in nutrient uptake
• Physiological imbalance in plants
• Restricted root system
• Toxicity of nutrient
• Loss of soil fertility
9
IllEffectsOfIrrigation,cont…

Selection of irrigation method
• There are several factors that need to be considered
while selecting an irrigation method.
• Farmers must have knowledge of the,
Soil condition
Topography
Size and shape of a field
Cropping system
Labor availability
10

• In pressurized irrigation system, water is applied to
plants under pressure through a network of pipes and
pumping system.
• Any how this system is not feasible unless energy
resources are available at reasonable cost.
• Farmers must have access to electricity supply in order to
run a pump unit, which is needed to dissipate water with
pressure.
11
Selectionofirrigationmethod,cont…

• Development and annual operational costs are the most
important factors while selecting an irrigation method.
• It is not only the equipment, construction and
installation cost but also the operation cost that needs to
be taken care of.
• These costs must be compared with the expected yield
benefits.
• The farmers will be interested in implementing a certain
method only if they find it economically attractive.
12
Selectionofirrigationmethod,cont…

Irrigation systems
• There are two types of irrigation system
Gravity flow or surface irrigation
Pressurized irrigation
• Gravity flow refers to the application and distribution of
water from higher to a lower topography by gravity flow.
• In this method, the land to be irrigated must have a
gentle slope, else the cost of land leveling and
preparation go may up considerably.
• It is by far the most common form of irrigation method in
the world.
• There are 4 basic methods of surface irrigation. 13

Methods Of Irrigation
1. Surface irrigation
(a) Uncontrolled/ wild/ free flooding method
(b) Border strip method
(c) Check method
(d) Basin method
(e) Furrow method
2. Sub-surface irrigation
3. Sprinkler irrigation
4. Drip irrigation 14

Surface Irrigation
• In this methods, water is either ponded on the soil or
allowed to flow continuously over the soil surface for the
duration of irrigation.
• It results in low levels of performance due to uncertain
infiltration rates which are affected by,
Year-to-year changes in the cropping pattern
Cultivation practices
Climatic factors and
Other factors
15

Uncontrolled Flooding
• It is the application of water without any preparation of
land and without any levees to guide or restrict the flow
of water on the field.
• Uncontrolled flooding generally results in excess
irrigation at the inlet region of the field and insufficient
irrigation at the outlet end.
• Efficiency is reduced because of either deep percolation
or flowing away of water from the field.
• The advantage of this method is the low initial cost of
land preparation.
16

17
UncontrolledFlooding,cont…
Figure 01: Wild flooding

Border strip Method
• It is a controlled surface flooding method of applying
irrigation water.
• In this method, the farm is divided into a number of
strips.
• These strips are separated by borders.
• These borders are 2–10 m wide and 52–300 m long,
depending on the soil type and slope of the field.
• It is suited to soils of moderately low to moderately high
intake rates and low erodibility.
18

• This method requires preparation of land involving high
initial cost.
• Examples of crops irrigated by this method include
wheat, leafy vegetables and fodder.
19
BorderstripMethod,cont…
Figure 02: Border strip method
Siphons
Head ditch
Drain

Advantage
• No land is wasted for making channels expect the supply
channels
• Efficiency of water application is high compare to furrow
and basin irrigation
• Variable stream size can be efficiently used
• Labor requirement is low
20

• Easy disposal of excess surface water
• Effective application of machinery
• Easy removal of excess rainfall
• Suitable method for low to moderately high water intake
rates soil
21

Disadvantages
• Precise land leveling is essential
• Initial cost of land preparation and land grading is high
• Not suitable for uneven and undulating land with shallow
soils
• Enough skill is required in applying water
22

• Not feasible for high intake soil
• Not suited for crust forming soil
• Only appropriate for close spacing crops
• Stream size must be large to carry out major tillage
operation
• Suitable only for particular topography < 1% of slope
23

Basin method
• This is the most common irrigation method
• In this method field is divided in to small units.
• All four sides of basin is surrounded by earth bunds.
• Each basin has nearly level surface.
• A common irrigation or drainage line runs in between
two strips of such small plots.
• The basins are filled with water to a desired depth.
• Then the water is retained until it infiltrate into the soil
24

Advantages
• Suitable for flat land
• No salt accumulation
• Easy management
• Well adopted for small holder farmers
• Suitable for close spacing crop
• Rain and irrigation water can be conveniently used for
wetting the root zone
25
Basinmethod,cont…

Disadvantages
• Leveling of land within the unit is very difficult
• Labor cost is high for land preparation
• Not applicable for high infiltration soil
• 20% of the land is lost in bund preparation
• Difficulties in the operation of machineries
• Removal of excess rainfall is difficult
• Land grading and shaping are required
26
Basinmethod,cont…

27
Basinmethod,cont…
Figure 03: Basin method

Check Method
• It is based on rapid application of irrigation water to a
level or nearly level area completely enclosed by dikes.
• The entire field is divided into a number of almost
leveled plots surrounded by levees.
• This method is suitable for a wide range of soils ranging
from very permeable to heavy soils.
• Loss of water through deep percolation and surface
runoff can be minimized.
28

• In addition, adequate irrigation of the entire farm can be
achieved.
• So that, application efficiency is higher for this method.
• Any how there is some loss of cultivable area which is
occupied by the levees.
CheckMethod,cont…
29
Figure 04: Check method

Furrow Method
• In this method small channels are constructed along the
primary direction of the movement of water and letting
the water flow through these channels.
• Furrows necessitate the wetting of only about half to
one-fifth of the field surface.
• This reduces the evaporation loss considerably.
• Furrows provide better on-farm water management
capabilities for most of the surface irrigation conditions.
30

• Possibility of increased erosion
• Furrow irrigation requires more labor than any other
surface irrigation method.
31
FurrowMethod,cont…
Figure 05: Furrow method

Advantages
• Less evaporation loss
• Variable size of streams can be used
• Wide rage of soil can be irrigated
• Furrow act as drainage channel in high rainfall areas
• Suitable to use in crust forming soil
32

Disadvantages
• Land requires precise grading to uniform slope
• Labor requirement is high for grading land and making
furrows
• Erosion of furrow is anticipated if furrows are not
properly graded
• Salt accumulation on the furrows causes salinity
problems
33

Subsurface Irrigation
• Subsurface irrigation (or simply sub irrigation) is the
practice of applying water to soils directly under the
surface.
• Moisture reaches the plant roots through capillary
action.
• The conditions which favor sub irrigation are as follows:
• Impervious subsoil at a depth of 2 m or more,
• A very permeable subsoil
• A permeable loam or sandy loam surface soil
• Uniform topographic conditions and
• Moderate ground slopes
34

• In flooding method of irrigation, a field is flooded with water.
• This results in significant
Runoff
Anaerobic conditions in the soil and around the root zone
Deep irrigation below the root zone
• Therefore, surface irrigation method is an inefficient irrigation
method.
• In contrast, microirrigation is an efficient method of water
application.
36
Microirrigation,cont…

• Microirrigation is the slow application of continuous
drips, tiny streams or miniature sprays of water above or
below the soil surface.
• This system is effective in saving water and increasing
water use efficiency as compared to the conventional
surface irrigation method.
• It helps reduce,
Water consumption
Growth of weeds
Soil erosion and
Cost of cultivation
37

• Microirrigation can be adopted in all kinds of land,
especially where it is not possible to effectively use
flooding method for irrigation.
• Microirrigation can be useful in
Undulating terrain
Rolling topography
Hilly areas
Barren land and
Areas having shallow soils 38

Features of microirrigation system
• Water is applied via pressurized piping system.
• Microirrigation requires pumps for developing the
required pressure for delivering water through pipelines.
• This is the basic requirement regardless of whether the
source of water is surface or underground.
• Water is applied drop-by-drop for a long period in case of
drip irrigation system.
• Water is applied at a low rate to maintain the optimum
air–water balance within the root zone.
39

• Water is applied at frequent intervals as per the
requirement of plants.
• Water is supplied directly to the plants and not to the
other areas of the field, thus, reducing wastage.
• Soil moisture content is always maintained at ‘field
capacity’ of the soil.
• Hence, crops grow at a faster rate, consistently and
uniformly.
40
Featuresofmicroirrigationsystem,cont…

Classification of microirrigation system
• Microirrigation system can be broadly classified into two
categories.
(1) Drip irrigation system
(2) Sprinkler irrigation system
• However, there are distinct differences between drip and
sprinkler irrigation systems in terms of
Water flow rate
Operating pressure requirement and
Measurement of the wetted area
41

• Water flow rate means the amount of water discharged
in an area at a particular time.
• It is expressed in liter/minute or gallons/ minute.
• The system operating pressure must compensate for
pressure losses through system components and field
elevation effects.
42
Classificationofmicroirrigationsystem,cont…

Sprinkler Irrigation
• It is the method of applying water to the soil surface in
the form of a spray.
• Rotating sprinkler head systems are commonly used for
sprinkler irrigation.
• Each rotating sprinkler head applies water to a given area
which is governed by the nozzle size and the water
pressure.
• Alternatively, perforated pipe can be used to deliver
water through very small holes.
• These holes are drilled at close intervals along a segment
of the circumference of a pipe 43

• Sprinklers have been used on all types of soils on lands of
different topography and slopes and for many crops.
• The following conditions are favorable for sprinkler
irrigation:
• Very previous soils which do not permit good
distribution of water by surface methods
• Lands which have steep slopes and easily erodible soils
• Irrigation channels which are too small to distribute
water efficiently by surface irrigation and
• Lands with shallow soils and undulating lands which
prevent proper leveling required for surface methods
of irrigation
44
SprinklerIrrigation,cont…

Advantages
• Low water loss (efficiency up to 80%)
• Saving in fertilizer
• Suitable for any topography
• No soil erosion
• Better seed germination, free aeration of root zone
• Uniform application of water
45

Disadvantages
• High initial cost, cannot adopt by ordinary farmers
• Poor application efficiency in windy weather and high
temperature
• High evaporation losses
• Water should be free of debris
• Physical damage to crops by application of high intensity
spray
46

47
Figure 06: Sprinkler irrigation

Drip Irrigation
• Drip irrigation is also called trickle irrigation.
• It involves slow application of water to the plant root
zone.
• The losses by deep percolation and evaporation are
minimized.
• A precise amount of water is applied to replenish the
depleted soil moisture at frequent intervals, for optimum
plant growth.
• The system enables the application of water and fertilizer
at an optimum rate to the plant root system.
48

• Trickle irrigation system comprises,
Main line
Sub mains
Laterals
Valves (to control the flow)
Drippers or emitters
Pressure gauges
Water meters
Filters
Pumps
Fertilizer tanks
Vacuum breakers and
Pressure regulators
49
DripIrrigation,cont…

• The drippers are designed to supply water at the desired
rate directly to the soil.
• Low pressure heads at the emitters are considered
adequate as the soil capillary forces causes the emitted
water to spread laterally and vertically.
• The amount of water supplied to the soil is almost equal
to the daily consumptive use.
• Thus it is possible to maintain a low moisture tension in
soil.
50

51
Figure 07: Schematic diagram of drip irrigation

52
Figure 08: Drip irrigation

Advantages:
• Low water loss and hence saves water
• Enhances plant growth and plant yield
• Saves labor and energy
• Control weed growth
• No soil erosion
• Improves fertilizer application efficiency
53

Disadvantages
• High skill in design, installation and subsequent
operation
• Clogging of small conduits and openings
• Not suitable for closely planted crops
54

Quality of irrigation water
• Surface water, ground water and suitably treated waste waters
are generally used for irrigation purposes
• Irrigation water must not,
have direct or indirect undesirable effects on the health
of human beings, animals and plants.
damage the soil and not endanger the quality of
surface and ground waters with which it comes into
contact.
• The presence of toxic substances in irrigation water may
threaten the vegetation besides degrading the suitability of
soil for future cultivation. 55

• Classification of various types of impurities, which make
the water unfit for irrigation:
• Sediment concentration in water
• Total concentration of soluble salts in water
• Proportion of sodium ions to other ions
• Concentration of potentially toxic elements present in
water
• Bacterial contamination
56
Qualityofirrigationwater,cont…

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