This document discusses definitions and strategies for improving irrigation efficiencies at the field level. It defines key terms like irrigation efficiency, application efficiency, distribution efficiency, and water use efficiency. Irrigation efficiency looks at the volume of water beneficially used divided by the volume delivered. Application efficiency focuses on a single irrigation event and how much water is stored in the crop root zone. Distribution efficiency measures uniformity of application. The document also discusses strategies to improve efficiencies like reducing losses, minimizing irrigation inputs while maintaining production, and allowing a greater area to be irrigated with the same water volume.

1. Irrigation Efficiencies,their Importance and Strategies for their
Improvementat Field Level
C K Saxena
Central Institute of Agricultural Engineering, Bhopal 462 038
Introduction
Continuouslygrowing demand offood,fibre and services to ever increasing population of the world coupled with
decreasing or degrading natural resources ofland and water have created tremendous pressure on planners and
executers. The agricultural productivity has continuouslybeen increasing over lastfew decades.Water scarcity is
likely to be the single mostimportantregional and global resource management challenge in the coming years.
Prudent use of water is becoming an immediate necessity.
The Webster’s Unabridged Dictionary (New World Dictionaries, 1979) and Turner (1987) defined the word
efficiency as (i) the ability to produce the desired effect with a minimum of effort, expense, or waste; and (ii) the
ratio of effective work done to the energy expended in producing it, as of a machine; output divided by input.
Efficient was defined as producing the desired effect, or result, with a minimum of effort, expense, or waste.
Major difficulties in defining irrigation system could include inadequate specification of the boundary conditions
(both temporal and spatial) that define the system being considered; as well as the difficulties in deciding an
appropriate output. Therefore, when applied to irrigation, the term ‘‘irrigation efficiency’’ is partially applicable in
that it considers the water consumed (crop ET) in producing the desired effect (crop production), but it could be
an inappropriate term if we consider the water that is not consumed as wasted. If expense is the main criterion
under consideration, then a properly managed surface, or gravity, irrigation system may be as efficient as more
sophisticated systems like sprinklers or micro-irrigation systems.Hence, the performance of an irrigation system
or projectmay better be described in specific terms pointing the physical or economic productivity of the system
rather than using efficiency parameters. On the other hand, both the input and output water volumes at different
locations and over a range of time scales within the overall irrigation system (Fig 1) can be assessed. Similarly,
while the ultimate volumetric output product of the irrigation system is the water used by the plant, the output
product from the whole farming system is commonly viewed as the marketable crop or the economic return s.
Hence, while it is possible to claim that the "efficiency" of water should not be defined in terms of crop yield
produced or value obtained. Several water management sub-systems exist at most irrigated farms or fields as
following:
 Supply systems (e.g. harvesting or lifting from river and captured overland flows);
 Pumping groundwater from bores wells; and/or supply from irrigation scheme dams, channels and/or
pipes);
 On-farm storage systems (e.g. tanks; or small catchment dams);
 On-farm distribution systems (e.g. earthen channels; gated pipes; or pressurised enclosed systems);
 Application systems (e.g. surface, sprinklers, micro-systems); and
 Recycling systems (e.g.tail drains and tail water recycling channels and utilising supplyharvesting pumps;
or catch drains feeding into fields in the down streams).
The efficiency of water use can be defined for each of these sub-systems based on the volumetric water inputs
and outputs,or uses and losses for a time frame – a single event or multiple events over irrigation or for a whole
crop season or for whole year. Potential volumetric losses (or inefficiencies) within each of these sub -systems
must be measured or estimated accurately to quantify whole farm water use efficiency. Volumetric
measurements of the water flows into and out of each unit are required and include groundwater and riverine
flows, scheme supplies, rainfall, seepage (or percolation), evaporation, overland flows and tail water recycling.
There could be several benefits that may include environmental and economic for better irrigation efficiency.
Improving irrigation efficiency will mainly:
 Mean less stress on water resources,less losses ofwater and nutrients to groundwater and surface water
resources;
 Minimise irrigation inputs while continuing to maintain/improve production and overall profits;
 Potentially allow a greater area to be irrigated with a given volume of water.
The key is to irrigate efficiently to improve economic performance (improving on-farm productivity) and
environmental performance (reducing impacts on water source and receiving waters) in a complementary way.

2. (Source: Barrett et al., 1999)
Fig. 1 Framework for irrigation efficiencies
Irrigation Efficiency Definitions
Although there are many definitions of irrigation efficiency, they can be grouped into three main categories of
irrigation efficiency, application efficiency and distribution efficiency.
Irrigation Efficiency
In general,irrigation efficiency is related to the percentage of water delivered to the field that is used beneficially.
Because benefits of applying water are not immediately attained, definitions containing a measure of beneficial
use are usually applied over a longer timeframe than for individual events. Some of these definitions are more
relevant when considering seasonal water allocation or seasonal water use. Few such definitions have been
discussed below. The traditional definition of irrigation efficiency (IE) (Kruse, 1978) is:
IE =
Volume of water beneficially used
Volume of water delivered to field
(1)
Burt et al. (1997) modified this definition to accountfor soil-water storage as:

3. IE =
Volume of water beneficially used
Vol of irrig water applied –Change in storage ofirrigationwater
(2)
This definition considers the overall water balance,area,hydrological boundaries, rainfall, soil moisture storage,
and all uses over an appropriate timeframe. The approach developed by the International Commission on
Irrigation and Drainage (ICID) by Bos et al. (1993) provides the following overall definition of irrigation efficiency.
They used the term overall project efficiency, which is suitable for all irrigation systems and is defined as follows:
OPE = Crop water use
Total inflow into supply system
(3)
Bos et al. (1993) subdivided this definition into three sub-components – conveyance efficiency, distribution
efficiency and field application efficiency, to track and account for water use from the point of supply through to
the crop. Because of the many invisible factors that influence irrigation efficiency from the source to the crop
(capital investment,labour availabilityand skills,energyuse, weather, and the physical performance of irrigation
systems), focusing on attaining a reasonable level of irrigation efficiency may be more realistic than trying to
calculate irrigation efficiencyrigorously.This takes the focus off trying to define all aspects of beneficial use. Burt
and Styles (1994) have used an alternative definition that they have called irrigation sagacity (IS), which they
consider to be a better measure of wise water use than irrigation efficiency, as follows:
IS =
Irrigation water beneficially or reasonably used
Irrigation water applied
(4)
Although this definition is probablya better measure ofgood water use, it has not been widely adopted, primarily
because of the difficulty of measuring beneficial or reasonable use.
Seasonal Irrigation Efficiency
An alternative definition ofirrigation efficiency that takes into account the seasonal nature ofirrigation is seasonal
irrigation efficiency (SIE), which was developed as part of the development of indicators of sustainable irrigation
(LE, 1997; Wells & Barber,1998). It relates the depth of water applied in a season to consumptive use ofthe crop
and typically gives values in the range of 1-2, with the more efficient systems resulting in values closer to 1, as
following:
SIE =
Seasonaldepth of water appliedto crop
Seasonalevapotranspiration−Seasonalrainfall
(5)
Application Efficiency
Where the focus is on the performance of a single event, application efficiency (AE) is most commonly used. In
broad terms, application efficiency is the percentage of water delivered to the field that is used by the crop. The
typical definition (e.g. Bos & Nugteren, 1974; Kruse, 1978; Jensen et al., 1983; Walker & Skogerboe, 1987) is
known as water application efficiency (WAE) and is:
WAE =
Volume of water requiredto replace cropevapotranspiration
Volume of irrigation water delievered to the field
(6)
Burt et al. (1997) define irrigation application efficiency(IAE) as follows:
IAE =
Average depth of irrigationwater contributing to target
Average dpeth of irrigation water applied
(7)
Burt’s definition differs from the one typically used as it goes beyond simplyreplacing soil water deficits.It implies
that water contributing to the target will eventually be beneficially used. In addition to meeting ET, it considers
crop water needs such as germination, cooling, frost protection, leaching and pest control. Partial replacement
of the soil water deficit to allow more effective use of rainfall is also considered.The definition proposed byBos et
al. (1993) for field application efficiency (FAE) is:
FAE =
Water applied that isused by crop
Water delievered to irrigation field
(8)
Another common definition relating to application efficiency is Irrigation System Efficiency (ISE), as defined by
Painter & Carran (1978):

4. ISE =
Water appliedthat isstored in crop root zone
Totalamount water delievered to the farm
(9)
Commonly, a variation to the above definition is used:
AE =
Water applied that isstored in crop root zone
Average depth ofwater applied to crop
(10)
This is identical to Eq.(9) for sprinkler irrigation systems, where losses between the water delivery point and the
field are considered negligible.It will differ on systems utilising non-piped delivery methods, as frequently found
on border-strip irrigation systems.This definition has been widelyused in design evaluations in New Zealand and
Australia (LE, 2005), McIndoe (2000) and Rout, et al., 2002). Several researchers have published application
efficiencies for a wide range of irrigation system types,some from India and California State University (Solomon,
1988) and Kansas State University (Rogers et al., 1997) are given in Table 1. These values are intended for
general system type comparisons and should not be used for specific systems or crops.
Table 1 Application efficiencies of irrigation systems
System type Solomon,
1988
Rogers etal.,
1997
Sivanappan,
1998
Clemmens,
2000
Surface
irrigation
Basin 80-90 -
Border 70-85 60-90 60-70 55-90
Furrow 60-75
Sprinkler
irrigation
Hand move or portable 65-75 65-80 70-80 65-85
Travelling gun 60-70 60-70 - 60-75
Centre-pivot & linear move 75-90 75-90 - 75-90
Solid setor permanent 70-80 70-85 - 70-85
Trickle
irrigation
With point source emitters 75-90 75-95 90 85-90
With line source products 70-85 70-95 - 85-90
Water Use Efficiency
One useful measure of irrigation efficiency that encompasses both water use and production is water use
efficiency (WUE). Water-use efficiency is defined as the ratio between the amount of water that is used for an
intended purpose and the total amount of water input within a spatial domain of interest. In this context, the
amountof water applied to a domain ofinterestbut not used for the intended purpose is a loss from that domain.
Clearly, to increase the efficiency of a domain of interest, it is important to identify losses and minimize them.
Depending on the intended purpose and the domain of interest, many efficiency concepts are involved, such as
crop water-use efficiency, field water use efficiency and others (Guerra et al., 1998). It is commonly defined as:
WUE =
Production (
kg
ha
)
Irrigation water use (m3
ha
)
(11)
Until recently, this definition was notoften considered as a measure of irrigation efficiency in India, although it is
commonly used in Australia and the USA. The definition focuses farmer’s attention on both water use and
production, and provides an indication of whether the resource has been used effectively. It is analogous to
another widely used term of water productivity, as because it defines the amount of food produced per unit
volume of water used. The water-used may have various components (evaporation, transpiration, gross inflow,
net inflow, and others), it is essential to specify which components are included when calculating water
productivity. The concept of water productivity, like the water-use efficiency, needs clear specification of the
domain of interest.
Distribution Efficiency
Distribution efficiencyis a measure ofuneven application.It is defined in terms of distribution uniformity and has
a significant effect on application efficiency. It is usually determined by measuring the depth of water collected
from a grid of catch cans during an irrigation event and analysing the variation of water depths collected in catch
cans.
Distribution uniformity (DU) is an expression that describes the evenness of water application to a crop over a
specified area, usually a field, a block or even an irrigation chak or command area. It applies to all irrigation

5. methods as all irrigation systems incur some non-uniformity. The lower the value of DU, the poorer is the
uniformity of application. It is computed by using following formula:
DU =
Average lowest quartile depth of water applied to crop
Average depth ofwater applied to crop
(12)
The mostwidelyaccepted hydraulic performance parameters for evaluation of micro-irrigation systems vis-à-vis
parity in water distribution are: Emitter flow rate variation (qvar), Discharge coefficient of variation (CVq or CV),
Christiansen uniformitycoefficient (CUC), and Distribution uniformity (DU) (Camp et al., 1997; Kang et al., 1999;
Kang and Nishiyama, 1996). qvar can be calculated from eqn.
𝑞 𝑣𝑎𝑟 =
𝑞 𝑚𝑎𝑥 −𝑞 𝑚𝑖𝑛
𝑞 𝑚𝑎𝑥
× 100 (13)
Where qmax is the maximum emiter flow and qmin is the minimum emitter flow.
Christiansen’s Uniformity Coefficient (CCU)
Christiansen’s (1942) uniformity coefficient (CCU) is commonly used for evaluating sprinkler or drip system
uniformity. It is defined as:
𝐶𝐶𝑈 = [1 −
∑ | 𝐷𝑖−𝐷̅|𝑛
𝑖=1
∑ 𝐷𝑖
𝑛
𝑖=1
]100 (14)
Where,
Di is the discharge or depth of irrigation of an emitter,
𝐷̅ is the mean discharge of all emitters (or plants in case of plant wise determination of CCU),
n is total number of observations/emitters (total number of plants in case of plant wise determination of CCU).
The definitions ofDU and CU require that catch volumes are representative of the depth applied to equal areas,
or, the catch volumes are weighted according to the area they represent. If application depths are normally
distributed and the mean depth of water applied is the same as the mean soil water deficit, Seginer (1987)
showed that application efficiency can be approximated from CCU as follows :
AE = 0.5 [ 1 + CCU/100 ] (15)
This definition allows onlyfor losses due to non-uniform applications under situations where depths applied equal
soil water deficits.
Wilcox-Swailes Coefficient of Uniformity
Wilcox & Swailes (1947) proposed a uniformity coefficient, Wilcox-Swailes Coefficient of Uniformity (WSCU)
based upon the coefficient of variation, which can be expressed as:
WSCU = (1 – CV) (16)
Where, CV is Coefficient of Variation expressed in fraction, as the standard deviation divided by mean value of
emitter discharges (or the mean and the standard deviation of the sum ofdischarges of all emitters at each plant
for plant wise WSCU). This parameter has the same limitation as the CCU. Table 2 provides the performance
rating as classified as per ASAE standard for the emitters’ discharge.
Table 2 Emitter quality classifications for Coefficient of Variation (CV) 1
Classification
Point Source
Line SourcePressure
Non-compensating
Pressure
Compensating
Excellent < 0.03 < 0.05 < 0.05
Good 0.03 - 0.05 0.05 - 0.10 0.05 - 0.10
Fair 0.05 - 0.10 0.10 - 0.15 0.10 - 0.15
Poor 0.10 – 0.15 - 0.15 - 0.20
Unacceptable > 0.15 > 0.15 > 0.20
Statistical Uniformity
1
Source: Drip Design in the Landscape,The Irrigation Association,August2000

6. Hart (1961) described the uniformityof irrigation through the terms Statistical Coefficient of Uniformity (SCU) and
Low Quarter Distribution Uniformity (SDUlq), which are expressed as:
SCU = (1 – /2 CV) (16)
SDUlq = (1 – 1.27 CV) (17)
The reason for the use of term 1.27 in Eq (17), as explained by Hart (1961) is due to the fact that in a normal
distribution, the mean of the low quarter of the values occurs approximately 1.27 times the standard deviation
below the mean. These parameters were used by many workers (Solomon, 1984; Burt et al., 1997; Ascough &
Kiker, 2002 and Saxena & Gupta, 2006). While SCU has the same limitation as the CCU, SDUlq reflects on the
deficit of water in the lower quarter of the area if each dripper represents the same area. Error! Reference
source not found.3 can be utilized to assign a qualitative rating to the lower quarter distribution uniformity
(SDUlq) for irrigation systems according to characteristics as “excellent,very good,good, fair, and poor” based on
the type of micro-sprinkler actuallyused in the station/zone.If the overall lower-quarter distribution uniformity has
a rating of “fair” or “poor,” then consider redesigning the system through the replacement in sprinkler heads or
emitters type, their spacing, and correcting operating pressure problems etc.
Table 3 Rating of Lower Quarter Distribution Uniformity (DULQ) for Sprinkler Zones
Type of
Zone
Excellent
(%)
Very Good
(%)
Good
(%)
Fair
(%)
Poor
(%)
Fixed Spray 75 65 55 50 40
Rotor 80 70 65 60 50
Impact 80 70 65 60 50
(Source : IA, 2002))
Emission Uniformity
In trickle irrigation,distribution efficiencyis a measure ofthe variation of emitter flows down a lateral or
throughoutan irrigation block. Measurementofapplied depths in trickle irrigation is more difficult,so distribution
efficiency is usuallyspecified in terms ofemission uniformity(EU), which is defined as follows:
𝐸𝑈 = 100{1 −
1.27 𝐶𝑉 𝑚
√ 𝑛
} ×
𝑞 𝑚𝑖𝑛
𝑞 𝑎𝑣𝑔
(18)
Where, CVm = coefficientof manufacturing variation for the emitters; n = number ofemitters per plant; qmin =
minimum emitter flow in block; and qavg = average emitter flow in block.
Table 4 Recommended ranges of design emission uniformity (EU)
Emitter type Spacing (m) Topography Slope (%) EU range (%)
Point source on perennial
crops
>4 Uniform <2 90 – 95
Steep or undulating >2 85 – 90
Point source on perennial or
semi-permanentcrops
<4 Uniform <2 85 – 90
Steep or undulating >2 80 – 90
Line source on annual or
perennial crops
All Uniform <2 80 – 90
Steep or undulating >2 70 – 85
(Source : ASAE EP405.1 APR1988 R2008)
Standard design ranges ofemission uniformity(EU) for the micro-irrigation system is given in Table 4 for different
topographical,slopes and spacing. While, the performance of the micro-irrigation system could be rated as per
Table 5 for different types of systems.
Table 5 Rating of Emission Uniformity (EU) for drip/micro-irrigation zones
Type of
Irrigation systems
Excellent
(%)
Very Good
(%)
Good
(%)
Fair
(%)
Poor
(%)
Micro spray 80 70 60 50 40
Drip –Standard 80 70 65 55 50
Drip - Pressure compensating 95 90 85 80 70
(Source : IA, 2002))
Coefficient for Emitter Flow Variation
Bralts & Kesner (1983) used the term Coefficient for Emitter Flow Variation (CEFV) that can be measured both
plant and emitter wise from the field observations. It is expressed as:

7. 𝐶𝐸𝐹𝑉 =
0.667(∑ 𝑈𝑆−∑ 𝐿𝑆)
(∑ 𝑈𝑆+∑ 𝐿𝑆)
(19)
Where, US is the sum ofobservations in upper 1/6th
of distribution,and  LS is the sum of observations in
lower 1/6th
of distribution.
Computed values ofactual Coefficient of Uniformity(CU) were obtained from CEFV using the following equatio n
described by Camp et al. (1997) and Bralts & Kesner (1983) as CU(CEFV).
CU(CEFV) = (1 – /2 CEFV) (20)
The values of the computed CUs are theoretically similar to that of CCU when the data follow a normal
distribution. A comparison between CCU and the computed values of CU(CEFV) were made to assess in an
experimental set up, CU could be calculated using CEFV at reduced cost on observations (Saxena and Gupta,
2006). Application efficiency can also be estimated from the distribution uniformity of the applied water. An
empirical relationship has been derived to describe application efficiency based on distribution efficiency for
trickle systems (Walker, 1979).
Based on statistical uniformity and distribution uniformity, Pitts (1997) suggested the criteria for rating the
performance of drip system, which is reproduced in Table 6.
Table 6 Criteria for rating the performance ofthe irrigation systems
Statistical
Uniformity (SCU), %
Distribution Uniformity (DU), % System Rating
> 90
80-90
70-80
<70
>87
75-87
62-75
<62
Excellent
Good
Fair
Poor
Factors Influencing Irrigation Efficiencies
Irrigation system design and management decisions are the result of a complex interaction of many variables
which are rarely consistentbetween individuals.Irrigation managementis often expected to maximise efficiencies
and minimise the labour and capital requirements of the particular irrigation system without adversely affecting
the growing environment for the plant (Walker and Skogerboe, 1987). However, irrigation efficiencies are
influenced by a wide range of factors including:
 Agronomic (e.g. crop responses to climatic and soil moisture variables);
 Environmental (e.g. rainfall, its spatial and temporal distribution, other climatic factors, soils, salinity,
topography);
 Social (e.g. experience, education, skills, lifestyle, labour availability, fear of change);
 Economic (e.g. capital availability, operating costs, returns from product);
 Historical (e.g. existing infrastructure, previous farming systems);
 Hydrological (e.g. river/canal flow regimes, groundwater issues; surface flow harvesting);
 Engineering constraints (e.g. hydraulic design limitations on pumps, pipes and storages, supply
capacities, well performance);
 Regulatory policy (e.g. legislation on access to canals, river, surface and groundwater);
 Water availability and quality; and
 Other external factors (e.g. canal breach, system failure or no electricity etc.)
Many managerial actions are dependenton the specific type of irrigation application system or design available.
Other decisions (e.g. frequency of irrigation, depth of water to be applied) are common to all systems and
dependent on the nature of the crop, soil and environmental conditions. However, in all cases, irrigation
managers are faced with the need to identify practical and economic answers, in a situation where the system
(biological, engineering and economic) is exceedingly complex, its interactions and inter-relationships are
complicated or imperfectly understood, the available data is often inadequate, and the specific goal is
inadequately defined (e.g maximise marginal or total profit, or biological returns per unit of water/land/other
input?). Even at the single field scale, the irrigator requires a wide range of input information, much of which is
either inadequate or imperfectly understood, in order to implement an appropriate irrigation management plan.
Importance of Irrigation Efficiencies and Strategies for its Improvement
In India, the irrigated area is 34 per cent of the net area sown.The gross irrigated area is 80 million ha which gets
India the prize for the largest amount of irrigated agriculture in the world (Oza, A, 2007). This water is not used
efficiently, for example, up to 20 per cent of water delivered to the minor’s outlet may be lost in distribution
channels on-farm and around 60 per cent of water used for irrigation on-farm is applied using high volume,

8. gravity irrigation methods.In a study, the losses during the various phases ofwater conveyance were found to be
as much as 71 % (Table 7) (Thandaveswara, 2009). Some 10-15 per cent of water applied to crops is lost
through over watering. By improving on-farm irrigation efficiency, the return from crops can be enhanced due to
the reduced inputs required, the environment and its natural resources are better protected with its long -term
sustainability. Crop quality and yield increases due to improved water application and thereby a reduced water
logging,sedimentmovement,erosion,lesser runoff, leachate and nutrient losses in controlled deep percolation
can be checked. Several approaches or options can be used to improve on-farm irrigation efficiencies,which may
vary widely by region and with the commodityunder irrigation by considering these options individually, together
or in combination. Starting from adopting technology that better matches the irrigation water application to plant
water requirements; reconfiguring irrigation layouts, installing infrastructure, such as recycling systems and
piping,to improve on-farm storages and deliverysystems or installing new infrastructures, such as drip or spray
systems to improve in-field applications systems and saving of water from evaporation.
Strategies for Effective Irrigation Scheduling
Proper irrigation scheduling is a key elementin improving the irrigation efficiencies.Selecting a water scheduling
method will depend on the availability of climatic data. Crop water use depends on the type and growth stage of
crop, weather and soil conditions (e.g. temperature, sunshine, wind speed, relative humidity and soil moisture
content etc). Water use can be estimated based on maximum daily temperatures and the growth stage of the
crop. If climatic data cannot be measured on site or is not available nearby, it may be more appropriate to
schedule irrigation from representative field soil water measurements.Irrigation atproper time of the day reduces
the evaporation this can be done by avoiding mid-day irrigation and using under-canopy rather than overhead
sprinkling.
An efficient schedule can be accomplished by determining and controlling the rate, amount, and timing of
irrigation water in a planned and efficient manner. Using water measuring devices such as irrigation water
meters,flumes,weirs,or other water-measuring device installed in a pipeline or ditch. Variable rate application of
water should be considered if water holding capacities range significantly. Soils information on the available
water-holding capacity of the soil can helpful along with the amount of water that the plant can extract from the
soil before additional irrigation is needed (MAD). Water use information for various crops can be obtained from
various publications. Efficient scheduling is also possible using modern software tools such as CROPWAT,
SWAP and WASIM etc.
Strategies for Efficient Irrigation Water Application
Irrigation water should be applied in a manner that ensures efficient use and distribution, minimizes runoff or
deep percolation,and minimizes soil erosion.The selection of an appropriate irrigation system should be based
on having sufficient capacity to adequately meet peak crop water demands for the crop with the highest peak
water demand in the rotation. The method of irrigation employed varies with the type of crop grown, topography,
soils,shape and size of the field. The system capacity is dependent on the peak period evapotranspiration rate,
crop rooting depth, available water holding capacity of the soil, and irrigation efficiency. Other potentially limiting
factors are water delivery capacity and permitted water allocation.Field slope and steepness determines whether
surface or micro- irrigation can be used, apart from individual farmers’ interest and socio-economic factors. If
secondarysalinization from irrigation is a problem,an application method must be chosen to keep salts leached
below the root zone.
Micro-irrigation systems have discharge points or sufficientlysmall holes in sections ofhose so as to apply small
amounts of water at high frequency intervals generally at low flow rates and low pressures (Burt and Styles,
1994). Micro-irrigation systems are typically designed to only wet the root volume within the root zone and
maintain this zone at or near an optimum moisture level (James, 1988). Hence, there is a potential to conserve
water losses by not irrigating the whole field. Obvious advantages of micro-irrigation include a smaller wetted
surface area,minimal evaporation and weed growth,and potentially improved water application uniformity within
the crop root zone by better control over the location and volume of application (Hoffman and Martin, 1993). The
efficiency of micro-irrigation systems is often quoted as greater than 90% (e.g. Golberg et al., 1976; Hoffman et
al., 1990; Keller and Karmeli,1975;Jensen,1983).Losses of water in micro-irrigation systems principally occur
through evaporation from the soil surface, surface run-off and deep drainage. Evaporation losses are generally
small due to a limited wetted surface area and the absence of surface ponding due to the low discharge rates.
The application of water using micro-irrigation systems also normally occurs either beneath the plant canopy,
directly on to the soil surface or beneath the soil surface in case of subsurface drip system further reducing the
potential for atmospheric evaporation and wind drift. The wide diversity of micro-irrigation systems available can
be categorised according to either their physical structure or their placement in the field (e.g surface, subsurface
or suspended). The physical structures generally include a flexible thin-walled drip (or trickle) tape made of
polyethylene where the emitter is formed by the double chamber which is integral to the glued, welded or joined
walls ofthe tape; or a drip (or trickle) hose where the structure is a thicker walled polyethylene pipe into which the
separately formed emitter is inserted, welded, glued within, or attached externally to the hose. Emitters can be
described as linear, turbulent, or pressure regulating. Micro-sprinkler systems have small sprays as their
emission points and usually consist of LDPE with sprays inserted directly into the hose or on the end of small
micro-tube laterals thatcan be positioned some distance from the supply.The porous pipe (or leaky hose) made

9. of LD (Low density) or HD (High density) polyethylene. In few methods chemigation can be used. C overage,
timing,and type of chemical application determine which application method can be more efficient. Chemigation
with surface irrigation should be avoided when alternative methods are available for the application of fertilizers
and pesticides mostly due to environmental issues. When a micro-irrigation system is properly designed and
operated, it can effectively contribute in increasing application efficiencies.
Table 7 Average cropyield,percentage increaseinyield,wateruse efficiencyandwater savingindripover
the conventionalirrigationsystemfor variouscrops
S.
No.
Crop
No.of
references
Yield (tha-1
)
Yield
Increase
(%)
WUE
(tha-1
cm-1
)
Water
saving(%)
1 Banana 7 71.52 29.27 2.95 42.50
2 Ber 3 71.03 27.67 0.66 34.33
3 Bitter gourd 4 2.68 44.38 1.43 69.50
4 Bottle gourd 1 55.80 46.80 1.03 35.70
5 Brinjal 7 16.01 44.63 1.47 42.55
6 Cabbage 5 50.49 37.48 3.17 37.35
7 Capsicum 1 22.50 66.60 0.78 43.10
8 Carrot 1 26.26 92.30 0.81 33.60
9 Castor 2 7.27 30.24 1.73 32.99
10 Cauliflower 3 19.50 39.73 0.68 37.10
11 Chilli 5 67.98 28.74 7.47 47.28
12 Coconut,No/plant 2 181.00 7.10 6.89 50.50
13 Cotton 3 36.00 40.00 0.86 51.10
14 Cucumber 1 22.50 45.10 0.94 37.80
15 Grape 5 29.93 20.94 0.95 43.00
16 Groundnut 2 3.50 62.50 1.00 32.40
17 Guava 2 25.50 63.00 3.53 9.00
18 Mango 3 19.50 80.67 2.40 28.93
19 Mosambi,1000pcs 1 15.00 98.00 0.23 61.00
20 Okra 12 20.05 20.69 1.94 44.72
21 Onion 3 17.01 42.60 1.20 36.70
22 Papaya 5 56.64 71.97 0.91 67.97
23 Pomegranate,100pcs 3 44.67 55.67 0.53 57.33
24 Potato 5 28.66 50.02 2.80 24.62
25 Radish 2 17.00 27.50 5.04 64.00
26 Ridgegourd 3 17.39 14.50 4.36 43.39
27 Sweetpotato 1 50.00 39.00 1.98 68.00
28 Sugarcane 6 145.87 43.59 1.19 46.67
29 Tapioca 2 54.60 12.60 0.55 23.40
30 Tomato 11 36.57 46.00 3.82 37.35
31 Turmeric 2 18.44 76.30 0.56 53.10
32 Watermelon 3 46.80 64.83 2.13 46.10
(Source: Saxena and Gupta, 2004) WUE= Water Use Efficiency, pcs= Pieces
There have been a range of recent literature reviews on micro-irrigation. Burt and Styles (1994) provide a
practical guide to the design, installation and management of drip and micro-irrigation while Camp (1998) has
undertaken a comprehensive review of published research into the design and evaluation of subsurface drip
irrigation.Table 7 is a compilation of numerous studies conducted indifferentparts ofthe country on various crops to
quantifythe benefits ofthe use ofdripirrigationin terms ofincreasedproductionandproductivityas well as saving ofwater
(PadmakumariandSivanappan,1989;Raman,1999;Sivanappan, 1999; and Singh et al., 2002, Saxena and Gupta,
2004 etc.).
Improved Agronomic Practices – Some More Options
As on-farm irrigation efficiencies mainly depend on the application of water to the crop and its attributes lots of
agronomic interventions have been reported in literature to support their improving effects on irrigation
efficiencies. Some of them are:
 Surface evaporation can be reduced by avoiding mid-day irrigation and using under-canopy rather than
overhead sprinkling
 Avoid over irrigation, reduction of opportunity time also enhance the irrigation effciencies.
 Control weeds on inter-row strips and keep them dry
 Use multi row planting. Single lateral based system as well as alternative irrigation in two adjoining
laterals of micro-irrigation.
 Early transplanting in rice in parts of Bihar and other eastern states have been reported to have saved
water (Gupta & Gill, 2003).

10.  Transporting irrigation water from the source of supply to the on-farm irrigation system can be a
significant source of water loss and cause of degradation of both surface water and ground wate r.
Practices that are recommended to be used to ensure proper transportation of irrigation water (USDA-
NRCS, 1977) include transportation through pipelines,lining ofditches and water control structures such
as drops, chutes, diversion structures.
 The use of runoff water to can provide additional irrigation and reduce amount of diverted water and
increases the water use efficiency.
 Reuse ofpoor qualitysaline drainagewater for irrigation ofsalttolerantcrops is a viable option to minimize
the disposal needs. It could easily be achieved through the use of drip irrigation.
 The relative yield of wheat with pre-sowing irrigation with fresh water followed by saline water throughout
compared with yield where no pre-sowing irrigation with fresh water was made were always higher when
equal amount of salt was applied.
 Blending involves mixingtwo waters ofdifferentqualities to obtain water that is suitable for irrigation. The
salinityattained after mixingshould be within the permissible limits based on soil type, crop to be grown
and climate of the area. The cyclic use, also known as sequential application or rotational mode of
drainage water reuseis a technique which facilitates conjunctive use offresh and saline drainage effluent.
 Plant and harvest at optimal times as per the crop varieties and regions.
 Use of resource conservation techniques like direct sowing using zero till drill, use of permanent
beds for planting, raised bed planting, intermittent submergence of rice, in-situ moisture retention,
mulching, can reduce time lostas well as irrigation water and thus enhance the irrigation water use and
other efficiencies (Gupta & Gill, 2003)
 Precision Land Levelling: Precision land levelling gives more efficiently spread to the surface water
application over the entire field. Reshaping the surface of land can be done to planned grades by
manual, animal and machinery including advanced equipments like LASER land level lers. Precision
land levelling by laser leveller not only saved water and energy but also enhanced crop and water
productivity. It has been however argued that the cost involved in the additional investment on the land
levelling could not be economically effective over the drip irrigation in the orchards.
 Use of Polyacrylamide Application for Erosion and Infiltration Management: On surface irrigated
lands susceptible to irrigation induced erosion, the addition of a water soluble polymer polyacrylamide
(PAM) to irrigation water may be appropriate to minimize or control soil erosion. PAM enhances
available water, controls erosion and promotes infiltration on irrigated lands. When applied to soils,
erosion prevention PAM binds fine-grained soil particles within the top 1-2 mm of soil. A compendium of
PAM related research information is available at the website
http://kimberly.ars.usda.gov/pamPage.shtml. Additional factors that affect PAM’s effectiveness include
irrigation inflow rate, duration of furrow exposure, and soil salinity. (Sojka and Entry,1999).
Concluding Remarks
Efficient micro-irrigation involves a wide range of interrelated factors such as farm size, shape, soil conditions,
cropping patterns,agronomic crops,as well as the socio-political and economic aspects, utilization of water and
availability with appropriateness oftechnologies,facilities and infrastructure development,government and policy
support, provision of incentives and availability of financial support, as well as operations and ma nagement
approaches. Lots of efforts have been made in the past on research, development and extension of micro -
irrigation knowledge to achieve higher production and water productivity. From planning till execution as well as
operation and maintenance, all the management stages should to be water conscious.
Increasing the irrigation efficiencies in agriculture is necessary to solve many of the problems of the water crisis,
but this alone is not sufficient. Considerable attention must be given to establishing and maintaining access to
water for domestic uses and income generation,affordable water-productivityenhancing technologies,and giving
the small-scale farmers a voice in water decisions too. Attention needs to be paid to develop farmers’ oriented
cheaper and efficient water saving solutions like automated micro-irrigation and fertigation systems.
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