Booklet No. 357
II. Limitations of Water Availability
III. Present Irrigation Systems
IV. Drip Irrigation
V. Advantages of Drip Irrigation
Irrigation water is a very precious input for increasing agricultural production. Judicious
application of water to the crops is the urgent need of the day without lowering the yield
potential. Drip irrigation is a system, in which water is applied in drops during irrigation which
saves 50 to 70% of the water used in the conventional irrigation methods. This booklet gives
farmers most of the details about drip irrigation.
Dr. K T. Chandy, Agricultural & Environmental Education
Water is the most precious commodity in our country from the point of view of all-round
development and progress, sustained agricultural production and industrialization. The demand
of water is increasing day by day, for agriculture and for domestic uses. The priorities of use of
water also varies from place to place depending upon the circumstances. Presently about 92%
of water is used for agriculture, 2% for industries, and 6% for drinking and domestic purposes.
These allotments usually changes according to changing water use and scarcity situations.
After independence, our country has invested large amounts of capital on major and
minor irrigations projects even though, only 35% of cultivated area could be brought under
irrigation. The quantity of water received by the crops hardly meet their demands as per their
growth stages. On the one hand there are constraints in the availability of irrigation water, and
on the other there is a need for more facilities for irrigation among the farmers, due to the
increased awareness about modern production techniques, suggested by various extension
agencies and agricultural universities etc. This has resulted in excess drawing of ground water
leading to a serious problem of recession of groundwater table. This has also resulted in
increasing the cost of production and of lifting water from the ground level.
Under this situation, it is imperative to utilize the available irrigation water most
scientifically so that the water use efficiency can be increased manifold.
Drip irrigation is one of the latest methods of irrigation which is becoming popular in
areas where water scarcity and salt problems are present. It is also known as trickle irrigation.
It is a method of watering plants frequently but giving only the volume of water required
for consumptive use of the plants, thereby, minimizing such conventional losses, as deep
percolation, runoff, and soil water evaporation etc. With this objective, a large number of
scientists and technologists developed a modem technique for irrigation, called drip irrigation to
overcome the problem of scarcity of water to the crops. Drip irrigation was first used in green
houses in England in 1940's. Soon it spread to open fields in Israel and subsequently to many
other places in the world.
II. Limitations of Water Availability
The water resources of India are limited. About 75% of the total cultivated area in the
country depends on rainfall to sustain crop production. Success in dry farming depends on
moisture conservation practices and judicious use of available water for irrigation. The following
are the major limitations of water availability for the agricultural crops.
A. Erratic monsoon
In India, monsoon is usually erratic, sometimes delayed or nearly creating drought like
situations. Though the monsoons usually last for four months, the rains are received only in the
first two or last two months. Due to this .it is very difficult to decide the strategies of cropping
patterns. The mid-season changes in the cropping patterns, though, are suggested but are very
difficult to follow. The sufficient recharging of ground water is essential for sustainable farming,
but usually the purpose is defeated due to erratic rains.
B. Priority for drinking water
During the drought or scarcity situations priorities changes, making available more water
for drinking purposes in towns, cities etc. With the growing population in the country, the
demand for drinking water is ever increasing and the availability of irrigation water for crop
production is gradually decreasing. Due to further population pressure and urbanization, the
demand for drinking water may even further increase.
C. Priorities for industries
The progress of industrialization in our country is rapid and for the growth of industries
water is required. The demand and allotment of water on priority basis is also increasing day by
day. The National Commission on Agriculture has assessed 23% rise in water requirement for
industrial and domestic purposes.
D. Water for power generation
Since the demand for supply of electricity for the industrial and domestic purposes has
increased greatly large scale diversion of water for hydroelectric power generation through mini
and micro-hydel projects became a necessity. However, in
most cases this water can also be used for irrigation and domestic purposes.
E, Livestock and cattle wealth
During the drought period, a large quantities of water supply is diverted for cattle and
other livestock causing the scarcity of water for irrigation and other purposes.
F. Lifting charges
The cost of irrigation charges vary greatly, depending on the depth of water source.
Energy is always required for lifting irrigation water from the sub-soil. Hence it involves higher
cost which is greatly enhanced in the recent years, resulting in the increase of the cost of
production. The cost of water diverted from a free flowing stream using the gravitational force is
probably the cheapest.
G, Sub-soil water level
A large number of tube wells are set up during the recent past, which usually draw
excess ground water from sub-soil, without recharging sufficiently in the due course of time. Due
to erratic monsoon and excessive drawing of water the ground water table reserves are greatly
diminished. In the recent years, the number of tube wells increased rapidly in many parts of the
country and hence the water table has gone down considerably.
III. Present Irrigation Systems
The present day conventional irrigation systems have major disadvantages. The
distribution and drainage at the farm level are left to the individual farmers. The present
irrigation practices are often extremely wasteful. Although 3 the prevailing practices vary widely,
estimates indicate that farmers lose more than half the amount of water they receive at the
headgate, through evaporation, runoff, or deep percolation.
The following are some of the major constraints in the proper water utilization.
1. Land leveling
In gravitational irrigation water can not be used uniformly and efficiently by the farmers, if
the land is not properly leveled. Often the farmers do not have the adequate knowledge about
land leveling and shaping. For better irrigational efficiency, land leveling is a prerequisite though
it is expensive also.
2. Command area
The irrigational projects usually have a definite command area, which can be brought
under irrigation. The main activities under these projects are on farm works such as construction
of field channels and drains, promoting small bunds across small streams, organizing supply
facilities etc. Canal water is easily and conveniently available to the fields which are situated at
low level and at the head ends of the channels while it is scarcely available at the tail ends and
higher fields. Wherever the lift irrigation from canal is permitted, it becomes very costly and
3. Wastage of water
Due to construction of 'Kutcha' channels a large quantity of water is lost in transport due
to percolation, leakages etc. Thus overall water requirement increases many more times than
actually required for physiological processes of crop growth. Sometimes accumulation of water
in the field is also observed as waste due to lack of proper drainage.
4. Excess labour involvement
In the conventional irrigation system, from outlet (distributions) to the fields, channels are
made in the field which usually are subjected to leakages etc. This requires constant
supervision by labourers so that irrigation water is not lost to other fields. For distribution and
irrigation also labourers are required.
B. Disadvantage of conventional irrigation
The following are some of the important disadvantages of the irrigation methods
conventionally followed in India.
1. An estimated level of 43% efficiency in surface water utilization and 70 percent efficiency in
ground water utilization (at farm level) recorded, shows that a large quantity of water is not
properly uti1ised in the present irrigation system.
2. The distribution of water in the field by main canal, sub-canals and distributions up to the
outlet points into the fields and subsequently in the far off drainage points in the fields, is uneven
due to poor leveling. This sometimes creates problem for getting sufficient and adequate
irrigation to the crops.
3. Crops are usually subjected to cyclic changes of flooding and water stress situations, by
providing heavy irrigation at one time and leaving the fields to dry up for about 10 to 15 days.
The moisture availability to the crops is fluctuates from saturation to stress and again to
saturation. This results in poor yields of the crops.
4. The fields situated in low areas always get excess water causing prolonged water logging
due to lack of leveling of fields. Thus crops are subjected to water logging resulting in poor
5. In the fields about 10-15% of land is utilized for preparing channels and distributions etc.
which decreases effective area of cultivation.
6. Extensive areas of land in the arid and semi-arid regions of India have gone out of cultivation
due to rise of water table and accumulation of salts. Excessive irrigation and poor water
management are the chief reasons of water logging and gradual build up of excessive salts.
Progressive build up of soil salinity has made the soils unsuitable for cultivation.
7. Sometimes a large quantity of irrigation water is subjected to deep percolation and seepage
resulting in the use of higher amount of fertilizers.
8. In the absence of planned proper combinations of spacing, length and slope of furrow's and
suitable size of irrigation streams and duration of the water application, it will be very difficult in
regulating the flow of irrigation water in the fields.
9. Slow and gradual changes in soil physical properties, particularly soil structures due to top
soil erosion, takes place under present irrigation practices.
10. Cyclic changes of wetting and drying of soil particles, around the roots result in disturbances
of root activity of the crop.
11. In conventional irrigation, unmanageable undesirable weed growth is usually observed.
These weeds hinder free movement of water.
12. Due to the improper irrigation methods in the conventional irrigation system, crops can not
be raised satisfactorily. The moisture in the soil fluctuates between too dry to too wet stages.
Fig.l depicts the moisture fluctuation in the conventional system of flood irrigation.
Fig.1: Soil moisture changes under flood irrigation
Courtesy: Agri-energy Round Table, India & Deccan Sugar Institute, Pune, Pp 19 Study
C. Unsurmountable problems
In the conventional irrigation methods, a large number of problems are faced. Some of
them are briefly explained here.
1. Canals and lifts
The canal and lift irrigation system is so designed that farmers cannot have choice of
crops. Generally in the command area all the farmers are compelled to chose the same crop
and even the same varieties is the water is available only for certain periods. Besides, due to
seepage and percolation of water on both sides of the canal water logging, salinity and alkalinity
are common in the farmers fields.
Since wells are quite deep, the costs for digging or boring, high lifting pumps, their
installment and maintenance on electricity or diesel have to be borne by the farmers.
3. Field levels
The intensity of problems due to flow irrigation method varies from field to field
depending upon the soil profile and topography of the soils. Too clayey and sandy soils create
hurdles in irrigation as the former offers much resistance to penetration of water and in the later
water is easily lost through deep percolation and seepage.
IV. Drip Irrigation
The potential of drip irrigation in improving agricultural productivity was identified long
back. Drip irrigation is the term used for describe the method of irrigation which is characterized
by following features.
1. Water is applied at a low rate. It is let out drop by drop at the spot of application.
2. A given quantity of water is applied over a long period of time.
3. Water is applied at frequent intervals.
4. Water is applied directly to the root zone of plants. This minimizes the water loss.
5. Water is applied via a low pressure delivery system. Usually gravitational force is used for
6. Since the crops are irrigated throughout their growth periods, more water could be saved by
Water management in drip irrigation is carried out through micro irrigation techniques
such as surface drip and sub surface drip irrigations. Micro irrigations may be defined as a
method of irrigation which is used to provide equal and even amount of water directly to the
plant in a controlled manner. Surface drip and sub surface drip applications are the two types of
drip irrigation. They are briefly explained as follows.
A. Surface drip irrigation
Surface drip irrigation is provided with a Lateral Drip Poly Ethylene (LPE) or Life Lateral
Drip Poly Ethylene (LLDPE). Further they are fitted with microtubes which are also called
drippers, emitters and drip nozzles as per design. The daily requirement of water is supplied by
means of lateral pipes micro tube network on the surface of the soil. From these lateral pipes
and micro tubes it is easy to maintain the drip irrigation system as the clogging or any other
defects can be located and rectified immediately. The system can be shifted whenever and to
wherever it is required with minimum damage. The cost of installation is also reduced
significantly. At harvesting special care has to be taken to avoid damages to lateral pipes and
micro tubes. The approximate cost of 10000 to 12000 per acre depends mostly on design
characteristics, operation and maintenance. The network of drip irrigation consists of lateral
pipes fitted with microtubes and running in between rows of the crops, main line fitted with
pressure computing self flushing dripper valves at suitable distances. All the lateral tubes are
connected with a controlled water pumping mechanism, which gradually and slowly pumps
water which is made available by microtubes to the soil at regular intervals.
B. Sub-surface drip system
The LLDPE (Life Lateral Drip Poly Ethylene) lateral lines are buried in trenches at the
depth of 15-25 cms and water is applied in the sub soil zone. ¥or long duration crops the depth
of trench may be about 30-45 cms. They may be strips of pipes provided with holes or twin-waIl-
laterals under a specific pressure compensating system maintaining uniform discharge
throughout the lateral pipe. There are several prototypes of twin wall systems. The trenches are
to be made at the appropriate depth manually in the fields. The twin wall laterals are laid in the
trenches with openings upwards and trenches are closed with soil. The other equipments ego
sand filters screen filters, pressure gauges pressure valves, water meter, pumping mechanism
etc. are connected as per design.
C. Concepts of drip irrigation
Drip irrigation has the greatest potential in saving water and improving the crop yields.
Drip irrigation is the frequent slow application of water at low pressure through emitters located
at selected points along the delivery pipe lines. In Fig.2 typical pattern of soil moisture changes
over the time for drip are detailed.
D. Drip systems and components
Drip irrigation differs from conventional (furrow or sprinkler) by providing water to a plant
in a localized fashion, only at the plant root zone. Water is applied frequently, slowly and at low
pressures. In Fig 3 field layout for a crop row spacing
of one meter is detailed. The main components of a drip irrigation system is explained here.
1. Main components
A drip irrigation system consists of a main line, submains, laterals and emitters. The
main line delivers water to submains and the submains into the laterals.
Courtesy: AM. Michael, Irrigation: Theory & Practice, Pp 665
The emitters which are attached to laterals distribute water for irrigation. The mains,
submains and laterals are usually made of black PVC (poly Vinyl Chloride) tubing. The emitters
are also made of PVC material though other materials are also used. PVC material is preferred
for drip system as it can withstand saline irrigation water. It is also not affected by chemical
fertilizers. Emitters may have porous walls or twin walls and is a more complex mechanical unit.
Lateral lines are about 3/8 to 3/4 inch in diameter, and the main lines are of polythene 2 to 4
inches in diameter. Emitters may lie on surface or buried under the soil as per design. The
systems operates either daily or every other day, during most of the growing season. Duration
of application ranges from 1 to 16 hours and generally is not continuous.
2. Ancillary components
These include a valve, pressure regulator, filters, pressure gauge etc. The head of the
system consists of a pump to lift the water and produce the desired pressure and distribute the
water through nozzles or emitters. There are in general three main connections in a drip
irrigation system, namely, the main-sub main connections and sub-main lateral connections and
the lateral and microtubes as detailed in Fig. 4.
Courtesy: A.M. Michael, Irrigation: Theory & Practice, Pp 666
The main sub-main connection is usually a "Tee" either thread or slip. A sub-main is
used to deliver water into laterals and also used as a controller so that the field can be irrigated
separately under a desired water pressure at any selected time. All the specific items used for
control are installed in the sub- main which is called a sub-main manifold.
3. Pump and prime mover
The pressure necessary to force water through the components of the systems,
including the filter unit, main line, lateral lines and the drip nozzles, is obtained by a pump of
suitable capacity. Volute centrifugal pumps operated by engines or electric motors are
commonly used. The water pressure developed by the pump should be sufficient to maintain the
desired pressure at the laterals. The laterals may be designed to operate under pressure as low
as 0.15 to 0.2 Kg/cm2 and as to 1.75 Kg/cm2. A pressure drop of 0.5 to 1.0 Kg/cm2 may be
anticipated in the head of the drip system, including the filter. There is a further drop of pressure
in the laterals and the emitters. The water coming out of the emitters is almost at atmospheric
4. Filter unit
A filter unit which cleans the suspended impurities in the irrigation water so as to prevent
blockage of holes and passages of microtubes is an essential part of the drip irrigation system.
The effective performance of drip nozzles lies in the effective performance of the filter unit. The
filter system may consist of valves and a pressure gauge for regulation and control.
5. Micro tubes
The micro tubes or 'emitters' or 'drippers' or drip nozzles are provided at a regular
intervals on the laterals. They allow the water to emit at very low rates, usually in trickles. There
are three types of trickles.
i. Water seeps out continuously along the lateral lines.
ii. Water sprays or drips from an emitter connected or inserted on the laterals.
iii. Water sprays or drips from holes punched in the laterals.
The discharge rate of emitters usually range from 2 to 10 litres per hour.
E. Drip system design
The following general information are required for designing a drip irrigation system.
1. Water source
The source of water is usually a well or a tank storing rainfall runoff water. If it is a well,
information such as the level of water depth, recharging capacity, etc. is required for designing
the system. If it is a tank, information on reservoir capacity, evaporative loss etc. are required to
fabricate a drip irrigation system.
2. Types of crops
Different crops require different plant to plant and raw to raw spacings and water
requirements. The general layout of the system and especially the emitters will depend on the
type of crops sown.
3. Topographic condition
It is necessary to know the general level slope, land leveling and other level details to
determine the size and location of main and sub-main lines.
The infiltration rate, water holding capacity, texture, structure and the bulk density of the
soil must be known for designing.
5. Climatic records
These will show when and how often an irrigation is needed during various seasons of
F. Basic hydraulics
A drip irrigation system is made by a combination of different sizes of plastic pipes which
are usually considered as smooth pipes. The variation of discharge from emitters along a lateral
line is a function of the total length of the laterals and inlet pressure emitting spacing, and total
flow rate. This creates a design problem to select the right combination of length and pressure
in order to achieve an acceptable and non- uniform pattern of irrigation. Hydraulically the
pressure variation along the lateral line will cause an emitter-flow-variation and a pressure
variation along a sub-main will cause a lateral line flow variation.
V. Advantages of Drip Irrigation
Following are the main advantages of the drip irrigation.
1. Controlled application of water as per the needs of plants at low pressure to limited soil areas
2. Water saving to the tune of 50 to 70 per cent by reducing the total evaporative surface,
reduction in runoff and controlling deep percolation losse.
3. Soil erosion is minimal, due to no runoff water on surface.
4. Weed growth is minimum.
5. Water loss through transpiration is low.
6. Development of surface crust and determination of surface soil structure is avoided. Soil
compaction is less.
7. Limited soil wetting permits undisturbed cultural practices.
8. It is possible to obtain, better yield and quality of crops by controlling soil moisture-air-
9. We can save the fertilizers by monitoring the supply of nutrients as per the need of the crop.
10. Improvements in biological fertility can be achieved by avoiding pollution.
The initial expenditure in establishing a long term drip irrigation system usually costs
around Rs.32000/- per hectare. This includes the cost of all the components mentioned earlier
except the source of water and pump set on the well or boring. This heavy initial expenditure
usually discourages the cultivators to install drip system in his fields, though subsidies are given
on the purchase of these equipments by the central and state governments. The drip system of
irrigation is usually adopted in Maharastra by orchards and sugarcane growers. They receive
subsidies from the sugar development funds, besides the other agencies. The comparative
figures studied for sub-surface and surface drip and conventional furrow irrigation are given in
detail in Table I.
Table 1 Sugarcane Yield, quantity of irrigation water applied and its efficiencies
Treatment Particulars Total Yield/ Increase Water
No. quantity MT/HA in Yield use
of over efficienci
irrigation control es
T1 Subsurface, paired 93.86 143.8 12.22 1.532
planting daily irrigation
T2 Subsurface, paired 93.86 142.5 11.91 1.518
planting alternate day
T3 Subsurface, paired 107.56 175.5 36.94 1.631
planting daily irrigation
T4 Subsurface, paired 187.6 6154.21 20.32 0.821
planting alternate day
T5 Furrow method of irrigation, 215.35 128.16 - 0.595
normal planting (control)
The above data was collected from the trials conducted at Mahatma Phule Agri.
University, Rahuri on sugarcane crop. The highest yield (175 tonnes/ha) was obtained in
surface drip and paired planting of sugarcane with daily drip irrigation. The yield gain was
around 36% over the control yield. The water efficiency use in this treatment was also quite high
i.e. 1.631. The water saving over the conventional fur- row method was over 50 percent.
It is calculated that the gain of 47 Tonnes/ha will earn I around Rs.23,500 per year (@
Rs.500 per tonne). The drip irrigation systems of long term life (five years), may give farmer
additional income of around Rs. l,17,500 which may cover the initial cost.
On the long term basis, the drip irrigation system is more economical and paying for the
farmers. The drip system could be popularised if growers are financed in the initial stages and
subsidies are allowed.
Drip irrigation or trickle irrigation was first used in green houses of England in 1940; soon
it spread to open fields of crops in Israel, and in other countries. The efficiency in the use and
saving of a large quantity of water has attracted major attention in the recent years. In our
country, water is the most important input for increasing crop production and the saved water
can be utilized for other crops too. The major hurdle in adopting the drip system of irrigation in
large scale is its initial cost which an average Indian farmer will not be able to invest on priority
basis though a large number of agencies are also helping him. The problem can be more
practically tackled by forming irrigation co-operative societies and by joint