Water management in horticultural crops

WATER MANAGEMENT IN
HORTICULTURE CROPS
AGR 201 (1+1)
Dr. Jagadish
Dept. of Agronomy
HREC, Hogalagere

Importance of water
Water is indispensable: Human, Animal and Plant
All organism contain >90% water
>70% Fresh water used for agriculture
Used for Industries, power generation,
transportation, live stock and domestic purpose
Also called as Universal solvent, Liquid gold & elixir
of life

Functions of water in plant growth
 Germination of seeds
 Contain more than 80% water in plant system
 Base material of metabolic activities
 Imp role in photosynthesis, respiration and
transpiration.
 It act as carrier of plant nutrients from soil to
plant system
 Maintain plant temperature & turgidity
 Transport metabolites from source to sink

Effect of moisture stress on crop growth
 Leads to reduced photosynthesis
 Result in reduced transpiration rate
 Affects of translocation of assimilates
 Respiration increases with increase in moisture
stress
 Reduced enzymatic activities
 Hormonal imbalance
 Leads to retardation of nitrogen fixation
 Reduced nutrients uptake from soil

History of Irrigation in India
Its started in Sindu and Nile river basin
A. Before Independence:
 Indus valley civilization 2500 BC: Small and minor work and household to irrigate
small patches
 Vedic period 400 BC: Irrigate through dug well water
 Great karikala Cholan: built Grand Anaicat across river cauvery in 2nd
century, TN
 Samudragupta and King Ashok: Construction of wells and tanks across
India
 British Govt: During 19th century: Ex: UGP in UP, Mettur dam, periyar dam
B. After Independence:
Major irrigation project works and taken
Ex: Multipurpose river projects like Bhakranangal in punjab, TB project in
KA, Damodar valley project in MP

Importance of water management
 It is most imp. bcz resource are limited but water is needed for all sector
 It helps to proper use of available water resource
 It helps to storing and regulating the water resources
 It helps to proper allocation of water based on area and crop under
cultivation
 It helps to reduce the losses during irrigation: perculation and seepage
 It helps to timely application of sufficient quantity of water to crops
 It considered the cost and benefit of water utilization
 It considered future requirements of water domestic and agriculture
purpose
 It helps to protect the environment from overuse of water

Advantages of irrigation
 Irrigation play imp key role in increasing food production to
feed ever increase of population
 It ensures stable production from dry land area
 Permitting multiple cropping and employment generation
 It helps to reduced risk in expansive inputs
 It helps to increase the input use efficiency

Adverse effect of excess irrigation
 Wastage of large quantity of water
 Leaching of available plant nutrients
 Reduced microbial activity affecting nutrient
transformations
 Accumulation of salts leading to salinity and alkalinity
 Water logged condition of field and leads to physiological
stress

Scientific irrigation management
 4R’s
 R-Right time of irrigation
 R-Right quantity of irrigation
 R-Right method of irrigation
 R-Reduced the leakage of irrigation

Water resources and different crops under irrigation
Particulars
Amount of
water (km3)
Percentage of
total
1.Oceans 1,348,000,000 97.39
2.Polar ice, ice-bergs and glaciers 27,820,000 2.01
3.Ground water and soil moisture 8,062,000 0.58
4.Lakes and rivers 225,000 0.02
5.Atmospheric water 13,000 0.0001
Total 1,384,120,000 100.00
•Water occurs on earth in three farms: Solid, liquid and gaseous
•Only ground water, lakes and rivers and atmospheric water is
available for agriculture
In world

Sl.No. Country Area (m ha)
1 China 69.4
2 India 66.7
3 Pakistan 20.0
4 USA 26.4
5 World 324.0
Status of irrigation in the world
Irrigated area in the world is 20% arable land (Asia is 70%)
China, India and Pakistan is the major irrigated country in the Asia
Outside the Asia, USA was highest irrigated area

The average rainfall of India is 1194 mm in 75 effective rainy days
Net cropped area is 141.1 m ha out of which 66.7 m ha is irrigated
The present storage capacity of irrigation projects in India is about 38 m ha-m
One mm rainfall means 1 ltr of water standing in 1 square meter of area
Water resources of India:

Seasons of rainfall
South-West monsoon (Kharif)- June – September
North-East monsoon (Rabi)- October – December
Winter (Cold dry period)- January – February
Summer (Hot weather period)- March – May
State
Net irrigated
area
(m ha)
Per cent
irrigated area
Haryana 2.94 82.3
Punjab 4.04 98.2
U.P 13.18 79.0
Karnataka 3.56 35.8
Total India 66.70 47.3
Source Area (m ha) Per cent
Canals 17.0 26.3
Tanks 2.2 3.5
Wells 12.0 18.5
Tube wells 29.1 45.0
Others 6.4 9.5
Total 66.70 100.0
Net
irrigated
area
66.7 47.3
•Well irrigation: Bihar, Gujrat, Karnataka and Tamilnadu
•Canal irrigation: North India, AP, Assam, West bengal, Karnataka
•Tank Irrigation: MP, Chattisgarh, Orissa and Maharastra

Status of irrigation in Karnataka
 Average rainfall of Karnataka: 1248 mm
 Net irrigated area 35.56 lakh ha (35.8%)
Source Area (Lakh ha) Per cent
Canals 14.69 35.7
Tanks 1.66 4.0
Wells 4.61 11.2
Tube/Bore
wells
15.59 37.9
Lift Irrigation 1.05 2.6
Other Sources 3.52 8.6
Total 41.12 100.0

Characteristics of good rainfall
1. Quantity should be sufficient to replace the moisture depleted from the
root zone.
2. Frequency should be high so as to maintain the crop without any water
stress.
3. Intensity should be low enough to suit the soil absorption capacity.
Characteristic features of Indian rainfall:
1. There is wide variation in the quantity of rainfall received from place
to place.
2. Rainfall is not uniformly distributed throughout the year.
3. Within the season also the distribution is not uniform.
4. Late starting of seasonal monsoon and early withdrawal of monsoon.
5. Liability to failure is the peculiar behavior of Indian rainfall.

Classification of irrigation projects in India
1. Major irrigation project:
• It covers cultural command area of more than 10,000 hectares.
• This type of project consist huge storage reservoirs and often multi-purpose
projects serving other aspects like flood control and hydro-power.
• Ex: TB dam, Koyna Dam, KRS dam
2. Medium irrigation projects
 It covers cultural command area of 2,000 - 10,000 hectares.
 These are also multi-purpose surface water projects.
 Ex: storage, diversion and distribution structures of water
3.Minor irrigation projects
 It covers cultural command area of < 2,000 hectares.
 The main sources of water are tanks, small reservoirs and groundwater
pumping.

Different crops under irrigation in India
Sl.
No.
Crop
Gross cropped
area (m ha)
Net irrigated
area
(m ha)
Relative area in
percentage of
irrigated area
1 Rice 43.79 26.32 27.2
2 Wheat 29.14 27.45 28.4
3 Maize 9.18 2.45 2.5
4 Chickpea 9.44 3.65 3.8
5 Sugarcane 5.11 4.90 5.1
6 Groundnut 4.81 1.39 1.5
7 Cotton 12.66 4.13 4.3
8
Horticulture
crops
82.7 26.31 27.2
Total 197.00 96.60 100.0

SPAC- Soil Plant Atmosphere Continuum
Soil-plant-water relationship deals with the physical properties of soil and
water that influence the movement, retention and use of water by the
plants.
Soil waterSoil moisture: The water received after rain or irrigation is stored in
the soil profile
Functions of soil water:
a. Photosynthesis
b. Transpiration- Maintenance of body temperature
c. Translocation- nutrients from source to sink
d. Respiration- Gas exchange
e. Turgidity of plant
f. Enzymatic action
g. Hormonal activity
h. Essential for germination

Energy state of soil -water
Water potential:
 Refers to the ability of the water to move in
soil
 Unit of potential is Pascal (Pa), older unit is
bar
 More water in the soil = more water
potential
 At saturation, Water potential is near to 0
 As soil dries, water is held more tightly in
soil =water potential is negetive
 Water will always move from high energy to
low energy state
 Soil water potential is always negetive (-ve)
becouse of negetive matric potential.

Types of water potential
1. Gravitational potential (ψg): is attributed to the gravitational force and is
dependent on the elevation. In soil surface, water flows down under the
influence of gravity. Hence, ψg is positive.
2. Pressure potential (ψp): is attributed to the atmospheric pressure. In
unsaturated soil, ψp is considered ‘Zero’.
3. Matric potential (ψm): Soil matrix / soil solids consist of sand, silt, clay and
organic matter. These solids reduce the free energy of soil water. Hence,
matric potential is always negative. It is also called Capillary potential.
4. Solute/ Osmotic potential (ψs): results from the saltssolutes dissolved in
the soil-water. Dissolved salts reduce the energy status of free water. Hence,
ψs is always negative.

The total soil-water potential is denoted by ‘ψt’. It is the sum of the gravitational
potential, the matric potential, the pressure potential and solute/osmotic potential.
Ψt = ψg + ψp + ψm + ψs
where, ψg = Gravitational potential- Only matters when the soil is saturated.
ψp = Pressure potential- Negligible in soils.
ψm = Matric potential- Water potential of soils.
ψs = Solute or osmotic potential- It matters when the soil is salty.
Soil moisture tension is a measure the water is retained in the soil.
 It shows the force per unit area that must be exerted to remove water from the soil.
 It is expressed in bars or atmospheres or mega pascals.
 1 bar = 0.9869 atm ≈ 1 atm. (atm = average air pressure at sea level).
 1 atm = 1036 cm of water
Soil water potential: It’s the difference between the free energy of the soil
water to that of pure water at reference stage.
 Free energy of pure water is considered as zero
 adsorbed soil water is less to move hence its negetive

A. Adhesion:
 Adhesion is the force of attraction between molecules of different
substances.
 Ex: Water + Soil particle
 A thin film of water is held in soil particles due to this adhesive force.
 Soils with coarser fraction (sand) have lesser adhesive force.
B. Cohesion:
 Cohesion is the force of attraction between molecules of same substances
 Ex: Water + Water, Soil + Soil
 A thick film of water is formed due to cohesive force.
 Finer the size of the particle, higher will be the cohesive force.
C. Surface tension:
 The property of adhesion and cohesion together are responsible for surface
tension which is in turn essential for upward movement of soil moisture.
Physical properties of water

1. InfiltrationWater intake:
 Refers to the entry and downward movement of water from the surface into the
soil.
 This process is of great practical importance since its rate determines the
amount of run-off over the soil surface.
Infiltration rate
• The rate at which water is entering the soil at given time.
• It is expressed as cm per hr or min or sec.
• Infiltration rate decrease gradually with time as the hydraulic gradient reduces
and approaches a constant value.
• Basic infiltration rateSteady state infiltration
Movement of water into the soil
Typical infiltration
curves for different soils

Soil texture:
Clayey soils- least infiltration rate;
sandy soils- maximum infiltration rate (Sandy > Silty > Clayey).
Organic matter content: Soils with higher organic matter content have higher
infiltration rate.
Soil moisture: Wet soil- infiltration is less; dry soil- infiltration is more.
Nature of soil surface: Compact- less infiltration, loose- more infiltration
Soil depth: Shallow soils- less infiltration, deep soils- more infiltration
Soil structure: Poor aggregate stability- less infiltration, good aggregate
stability- more infiltration
Porosity: High porosity- more infiltration, low porosity- less infiltration
Vegetative cover: Vegetative cover- more infiltration, bare soil- less infiltration
Hydraulic conductivity of soil: High HC - more infiltration, low HC - less
infiltration
Factors influencing infiltration

Refers to the readiness with which porous medium transmits fluid
under standard conditions.
Factors influencing permeability:
Number of macropores: More the number of macropores higher is the
permeability.
Soil aggregates: Larger the size of capillary pores, greater is the
permeability.
Depth of soil: Permeability decreases with the depth.
Soil texture: In coarse textured soil, permeability is more compared to
fine textured soils.
Salt concentration: If sodium is high in water- cause dispersion of soil-
reduce the permeability.
Organic matter content: More organic matter in the soil results in more
permeability.
2. Permeability:

‘Downward movement of water through saturated or nearly saturated soil due to
the forces of gravity is known as percolation’
Percolating water is the source of recharge of ground water.
Percolating water carries nutrients to deeper layers beyond the root zone of the
field crops.
In sandy soils, there is a rapid loss of water through percolation.
Clayey soils permit less water to percolate.
In dry region percolation is almost negligible.
3. Percolation:

5. Capillary movement: Once the flow due to gravitational forces has been
ceased, the water moves in the form of thin or capillary film from a wet region
to dry region through the micropores.
Capillary movement may be in all directions: downward, lateral or upwards, from
low tension to high tension area.
4. Seepage: refers to the infiltration, downward and lateral movements of
water into the soil.
Such water may reappear at the surface as wet spots or may percolate to join the
ground water or may join the subsurface flow to springs or streams.

The theory of water movement in soils is based on Darcy's law,
which states that “the quantity of water passing a unit cross section of
soil is proportional to the gradient existing between two hydraulic
heads”.
Mathematically, q = kia
Where, q = volume of flow per unit time (cm3 sec-1).
i = hydraulic gradient, dimensionless
a = cross section of flow area (cm2)
k = hydraulic conductivity (cm sec-1)
Darcy's law:

Movement of water in the soil
Water movement in soil occurs in three distinct ways: saturated flow, unsaturated
flow and vapour movement.
1. Saturated flow:
 When all pores are filled with water either due to rain or irrigation or under
waterlogged situation.
 The major force in driving water in saturated soil is gravity and major direction
is downward movement.
 The rate of movement of water depends on the hydraulic conductivity of the
soil.
 Hydraulic conductivity can be expressed as:V=Kf
 Where, V is the volume of water moved per unit time, f is the water moving
force and K is the hydraulic conductivity.
 Sandy soils have higher conductivity due to the presence of higher macropore
space compared to clayey soils.

2. Unsaturated flow:
When micro pores are filled with water and macro pore are empty than the
condition is called unsaturated soil
The unsaturated movement is in micropores.
The major driving force is metric potential and lateral movement
Plants are subjected to moisture stress when rate of replenishment is
less than rate of absorption.
Unsaturated flow is more important from the point of crop production.
3. Vapour movement:
Water vapour moves from one zone to another due to vapour pressure
gradient i.e., from higher vapour pressure area to low vapour pressure area.
Vapour movement occurs in all the directions- downward, upward and
lateral, depending on the vapour pressure gradient.
Water vapour moves from higher temperature region to cooler region.

Soil moisture constants
1. Maximum water holding capacity (MWHC) or Saturation
capacity:
 When all the pores of the soil are filled with water
 The tension of water at saturation capacity is almost zero
2. Field capacity (FC):
The soil moisture held by the soil against gravitational force is called field
capacity.
At field capacity, Macro pores are filled air, Micro pores are filled with water
Field capacity is the upper limit of available soil moisture.

The soil moisture tension at field capacity is 1/3 atmosphere.

3. Wilting point:
a. Temporary wilting point (TWP): Here, the plants show the
symptom of wilting but regains their turgidity after application of
water
b. Permanent wilting percentage (PWP):
 The soil moisture content at which plants are fail to meet
transpiration requirements and remain wilted unless water is
added to the soil.
 The moisture tension of a soil at the permanent wilting point is 15
atmosphere.
 Lower limit of available water
c. Ultimate wilting point (UWP):
 This is the stage at which the plants die and no longer regains its
turgidity even with external addition of water.
 Here, the moisture is held at a tension of 60 atm.

4. Moisture equivalent:
Moisture equivalent is defined as the amount of water retained
by a sample after being subjected to a centrifugal force of 1000
times that of gravity for a definite period of time, usually half an
hour.
5. Hygroscopic coefficient:
The water is held very tightly around soil particles, mostly being
adsorbed by soil colloids and much of it can move only in vapour
phase.

ASM =
FC – PWP x BD x Depth of
soil
100
It is the quantity of soil water (moisture) available to plants.
It is the amount of water retained in the soil between field
capacity and permanent wilting point (ASM= FC – PWP).
FC represents the upper limit and PWP represents the lower
limit of available soil water.
It is usually expressed in percentage or depth (mm or cm).
Available soil moisture (ASM)
Note: Soil texture, structure and organic matter content influence available soil
moisture in the soil.

Soil moisture characteristic curve
The functional relationship between the energy status of water and
amount of water in the soil represented in graphical form is called
soil moisture characteristic curve.
As the energy status of water decreases
soil moisture content also decreases.
Soil moisture content decreases, more
energy has to be applied to extract
moisture from the soil.
Greater the proportion of clay, more will
be the moisture content at any given
tension.
The shape of the clay soil curve is almost a
straight line with bends on ends while it is
‘L’ shaped in case of sandy soil.

The moisture content at a given suction is greater in desorption than in
sorption and this phenomenon is known as hysteresis.
The relation between energy status and moisture content can be obtained in two
ways:
Hysteresis
(1). Desorption: Drying of initially
saturated soil gradually by applying
increasing suction.
(2). Sorption: Gradually wetting of an
initially dry soil.

The soil depth from which the crop extracts most of the water needed to meet its
evapo-transpiration requirements is known as effective root zone depth.
It is the depth in which active root proliferation occurs and maximum water
absorption takes place.
It is the soil depth used to determine irrigation water requirements of the
crops.
It is the soil depth in which optimum available soil moisture level get higher
productivity of crop
Effective root zone depth

Moisture extraction pattern
•It shows the relative amount of moisture extracted from different depth within the
crop root zone.
•Concentration of absorbing roots is greatest in upper part of the root zone and near
the base of the plants.

Consumptive Use of water
 Evaporation is defined as the process by which water moves out of the water
surface or soil surface in the form of water vapour to atmosphere due to pressure
gradient.
Evaporation from natural surface such as open water, bare soil or vegetative
cover surface to the atmosphere.
Solar radiation is the major source of heat energy for evaporation
Evaporation is measured with evaporimeters.
Evaporation

4) Piche evaporimeter
Types of evaporimeter
1) USWB Class A open pan evaporimeter 2) Sunken screen evaporimeter
3) Can evaporimeter

Transpiration
‘The process by which water evaporates in the form of water vapour from
living plant body especially from leaves to atmosphere’
The rate of transpiration depends on:
1. Supply of energy to vapourise the water and
2. The water vapour concentration gradient at atmosphere.

The combined loss of evaporation and transpiration from a cropped
field is termed as evapo-transpiration (ET).
CU = E + T + WP
The consumptive use includes evaporation (E), transpiration (T) and
water used by plants (WP) for its metabolic activities.
Amount of water used by plants (WP) for its metabolic activities is less
than 1% of the total water absorption. Hence the ET loss is taken as
consumptive use of crop (CU).
Evapotranspiration or Consumptive use is the important factor in
estimating irrigation requirement and planning irrigation system.
Evapo-transpiration (ET) or Consumptive use

Factors affecting ET
1. Climatic factors
a). Solar radiation: Increase with increased ET
b). Air temperature: Higher air temp higher will be the ET
c).Relative humidity: Higher RH, lesser the ET
d). Wind: Dry wind will remove the more evaporation
e). Precipitation: Precipitation increases, higher the ET
2.Crop factors
I. Stomatal opening and closing. Higher ET with opening of stomata
II. Leaf area: Higher the leaf area higher the ET
III. Adaptive mechanism: Ex. Rolling of Maize/sorgham leaves
IV. Rooting depth: Higher the depth higher the ET
V. Stage of the crop: Vegetative higher the ET
3. Management factors
a. Soil condition: Soil salinity lower the ET
b. Cultivation practices: use of mulching material

Potential Evapotranspiration (PET)
PET is defined as the amount of water loss through evaporation and transpiration
in unit time from a short, green crop growing actively and covering the soil completely,
which is never short of water.
This concept was suggested by Thornthwait in 1948.
it is also known as reference evapotranspiration denoted as ET0.
Crop evapotranspiration: denoted as ETc, is the evapo-transpiration from
disease free, well fertilized crops, grown in large fields, under optimum soil water
conditions.
ETc = Kc x ET0 , where as Kc- Crop coefficient
Kc = Crop evapotranspiration (ETc)
Reference evapotranspiration (ET0)

Measurement of Evapotranspiraton/ CU
Direct methods
1. Lysimeters
2. Soil moisture depletion studies
3. Water balance method.
Indirect methods
1.Empirical methods (ET computed from meteorological data)
a) Blaney and Criddle method
b) Radiation method
c) Modified Penman method
2. Pan evaporation method.

1. Weighed type of Lysimeter 2. Non weighed type of Lysimeter

CU = ∑
M1i – M2i
x BDi x Di
100
Where,
CU=Consumptive use in mm
M1i=Moisture content (%) at the beginning of the period in the ith layer of soil
M2i=Moisture content (%) at the end of the period at ith layer of soil.
BDi= Soil bulk density in ith layer (g/cm3)
Di=Depth of ith soil layer (mm)
n = number of soil layers in the effective crop root zone
3. Water Balance Method
Change in soil-water = Inputs of water – Losses of water
(P + I + C) = (ET + D + R) + W
n
i=1

Indirect Method: 1. Empirical method
A. Blaney and Criddle method
This method requires data on daily temperature and day time hours.
ET0 = C [P (0.46 T + 8)]
ET0 = reference evapotranspiration (mm/day) for the month considered.
C = adjustment factor
T = mean daily temperature (oC) for the month under consideration.
P = mean daily temperature of total annual day time hours.
B. Radiation method
This method requires direct measurements of duration of bright sunshine hours,
temperature and radiation data.
ET0 = C (W x Rs)
Rs = Measured mean incoming shortwave radiation (m/day)
W = Temperature and altitude dependent weighing factor
C = Adjustment factor (which depends on RH and daytime wind).

C. Modified Penman method
ET0 = C [W x Rn + (1 – W) x f (U) x (ea – ed)]
Where,
Rn = Net radiation (mm/day);
(ea- ed) = Vapour pressure deficit
F (U): Wind function
W= Temperature and altitude dependent weighing factor
C = Adjustment factor (to compensate for the day and night weather effects).
2. Pan evaporation method
ET0 = Epan x Kpan
Where, Epan = Evaporation (mm/day) from Class A Pan; Kpan = Pan
coefficient

Water requirement of crop is the quantity of water required by a crop for its
normal growth under field conditions.
1. WR = ET + WL + WSP
ET= Evapo-transpiration
CU= Consumptive use
WL= Application losses
WSP= Water for special purposes.
2. WR = IR + ER + S
IR- Irrigation requirement
ER-Effective rainfall
S- Soil profile contribution/ contribution from ground water table.
Water requirement of crops

Factors influencing water requirement
1. Crop factors: Variety, Growth stages, Duration, Plant population,
Crop growing season.
2. Soil factors: Structure, Texture, Depth, Topography, Soil
chemical composition.
3. Climatic factors: Temperature, Sunshine hours, RH, Wind
velocity, Rainfall.
4. Agronomic management factors
Irrigation methods used
Frequency of irrigation and its efficiency
Tillage and other cultural operations like weeding, mulching etc
Intercropping/ cropping systems.

n Mfci - Mbi
NIR= ∑ --------------- x BDi x Di
i=1 100
NIR =Net irrigation water to be applied (cm)
Mfci =FC in ith soil layer (%)
Mbi =Moisture content before irrigation in ith layer (%)
BDi =Bulk density (g/cc)
Di =Depth of ith layer (cm)
n =Number of soil layers in the root zone depth.
Net irrigation requirement (NIR)
The amount of irrigation water required to bring the soil moisture in the effective
root zone to field capacity to meet the ET demand of the crop.
It is the difference between the FC and the soil moisture content in the root zone
before starting irrigation.

• The total quantity of water used for irrigation is termed as gross irrigation
requirement.
• It includes net irrigation requirement and losses in water application.
Net irrigation requirement
Gross irrigation requirement (cm)= ---------------------------------- x 100
Field efficiency of system
Gross irrigation requirement (GIR)

1. Lysimeters
3. Water balance method.
4. Pan evaporation method.
5. Field Experimental plot method
6. Depth-interval-yield approach
7. Estimation of ET loss (emperical method)
a) Blaney and Criddle method
b) Radiation method
c) Modified Penman method
Determination of crop water requirements

Scheduling of Irrigation
Scheduling of irrigation is defined as the determination of the period when to
irrigate and how much to irrigate for optimal crop production.
The main approaches for scheduling of irrigation
1.Feel and appearance
2.Plant indices
3.Indicator plants
4.IW/CPE ratio
5.Sowing high seed rate
6.Soil cum sand mini plot technique
7.Tensiometer
8.Critical stage approach
9. Soil moisture depletion method
10.Stress day index (SDI)

1.Feel and appearance
2.Plant indices

4. IW/CPE ratio
Example: Cotton is irrigated at IW/CPE ratio = 0.8, if the crop was given
initial irrigation with 5 cm, the date of next irrigation is when the CPE reaches
6.25 cm (5 cm/ 0.8 = 6.25 cm).
If the evaporation data for 15 days is 4.0, 4.5, 4.0, 4.5, 4.5, 4.6, 3.8, 4.1, 4.5,
3.8, 4.2, 3.8, 4.2, 4.3 and 4.0 mm, on 15th day the CPE reaches 62.8 mm (= 6.28
cm), hence, the irrigation is scheduled on 15th day.

5. Sowing high seed rate
High seed rate
Normal seed rate

6. Soil cum sand mini plot technique

8. Critical stage approach
Crop Critical stages / Sensitive stages
Ragi Panicle initiation and flowering
Wheat Crown root initiation, tillering and booting
Groundnut Flowering, peg initiation and penetration and pod development
Cotton Flowering and Boll formation
Sugarcane Maximum vegetative stage
Onion Bulb formation to maturity
Tomato Flowering and fruit setting
Chillies Flowering
Cabbage Head formation to maturity
Carrot Root enlargement
Beans Flowering and pod setting
Potato Tuber initiation and maturity
Banana Throughout the growth
Citrus Flowering, fruit setting and enlargement
Mango Flowering
Coffee Flowering and fruit development

9. Soil moisture depletion method
Example: Maize crop to be irrigated at 50% depletion means,
If soil FC = 25% and PWP = 11%, Available water (AW) = FC – PWP = 25-
11 = 14%.
50% depletion of available water = 50/100 x 14 = 7%.
Maize should be irrigated when soil moisture is 25% - 7% = 18%.

Irrigation interval =
Allowable soil moisture
depletion
Daily consumptive use
Irrigation frequency is the interval between two consecutive irrigations during
crop period.
It is the number of days between irrigation during crop period without rainfall.
It depends on the rate of uptake of water by plants, moisture supply capacity of
soil to plants and soil moisture available in the root zone.
Irrigation frequency

Irrigation period is the number of days that can be allowed for
applying one irrigation to a given design area during peak
consumptive use period of the crop.
Irrigation period
Net amount of moisture in soil at start of irrigation (Actual - PWP)
Irrigation period =
Peak period consumptive use of crop

Irrigation water is an expensive input and has to be used very efficiently.
The main losses that occur during irrigation are conveyance, run-off,
seepage, evaporation and deep percolation.
Irrigation efficiency can be increased by reducing these losses.
Irrigation efficiencies
Types of Efficiency
1. Irrigation efficiency (Ei):
2. Water conveyance efficiency
3. Water application efficiency
4. Water storage efficiency
5. Water distribution efficiency (Ed)
6. Water Use Efficiency (WUE):

Irrigation
efficiency (%) =
Water stored in the root
zone of plants 100
Water diverted from the source
1.Irrigation efficiency (Ei):
It is defined as the ratio of the irrigation water stored in the root zone of
plants to the water delivered from the source.
In most irrigation projects in India, the irrigation efficiency ranges between
20 to 40 %.

2. Water conveyance efficiency:
Water conveyance efficiency is used to measure the efficiency of water
conveyance system
It is defined as the percentage ratio of the water delivered to the fields to
the amount of water diverted from the source.
Ec =
Wf
x 100
Wd
Where, Ec = Water conveyance efficiency (%)
Wf = Water delivered to the field (at the field supply channel)
Wd = Water diverted from the source

3.Water application efficiency:
•After the water reaches the field supply channel, it is important to apply the
water as efficiently as possible.
•The water application efficiency is defined as the percentage ratio of the
amount of water stored in the crop root zone to the amount of water
delivered to the field.
Ea =
Ws
x 100
Wf
Where, Ea = Water application efficiency (%)
Ws = Water stored in the crop root zone
Wf = Water delivered to the field (at the field supply channel)

4. Water storage efficiency:
Water storage efficiency refers to the percentage ratio of the amount of water
stored in the crop root zone to the amount of water needed to make up the
soil water depleted in the crop root zone prior to irrigation.
Es =
Ws
x 100
Wn
Where, Es = Water storage efficiency (%)
Ws = Water stored in the crop root zone
Wn = Water needed in the root zone prior to irrigation
Amount o water
needed

5. Water distribution efficiency (Ed):
Indicates the extent to which water is uniformly distributed on a
given land.
In field situation, deviation in depth of wetting is considered to
workout Ed using the formulae
Ed = ( 1 -
y
) x 100
d
Where, y = Average numerical deviation from d
d = Average depth of water stored in the field

6. Water Use Efficiency (WUE):
Water use efficiency denotes the production of crops per unit of water
applied.
A. Crop Water Use Efficiency (CWUE):
It is the ratio of crop yield (Y) to the amount of water depleted by the crop in
the process of evapo-transpiration (ET).
CWUE =Y/ET
B. Field Water Use Efficiency (FWUE): It is the ratio of crop yield (Y) to
the total amount of water used in the field (WR).
FWUE =Y/WR

Factors influencing WUE
1. Nature of the plant: Differences between plant species and between
varieties to produce a unit of dry matter per unit amount of water
used.
2. Climatic conditions: Weather affects both yield and ET.
3. Soil moisture content: Inadequate and excess supply of soil moisture
to crop has adverse effect on plant growth and productivity.
4. Fertilizers: Under adequate irrigation, suitable fertilization increases
crop yields considerably.
5. Plant population: Maintaining optimum plant population along with
optimum level of soil moisture and fertilization increases yield and
WUE.

Methods of irrigation
•The manner in which irrigation water is applied to the land is
referred to as method of irrigation.
•The basic principle for selecting any method is that the required
quantity of water reaches the root zone with minimum loss.
I. Surface Irrigation
II. Sub-surface irrigation
III. Sprinkler irrigation
IV. Drip irrigation

I. Surface Irrigation
 Surface irrigation is the most popular and convenient method.
 It is normally used when there is mild and regular slope, soils with
 Medium to low infiltration rate and a sufficient supply of surface

Surface irrigation: Merits and Demerits

1). Border irrigation
The land is divided into number of long parallel strips called borders.
Suited to soils having moderate infiltration rates.
It is not used in coarse sandy soils due to high infiltration rate.
Border method is suitable to irrigate all close growing crops
Advantages:
1. Border ridges can be constructed with simple implements (bund former).
2. Uniform water distribution and high application efficiency.
3. Large irrigation streams can be efficiently used.
4. Adequate surface drainage is provided.
Disadvantages:
1. High initial cost towards land shaping and stripping.
2. Needs maintenance of borders.
3. Not suitable for light soils owing to high infiltration.

2. Check basin irrigation
It is the most common method of irrigation in India and in many other countries.
Here the field is divided into smaller unit areas so that each has a nearly level
surface.
Advantages:
1. Check basins are suitable for leveled land.
2. Small streams can be applied efficiently
3. Soil erosion is nil or negligible.
4. High application efficiency
5. Better use of rain water
Limitations:
1. Requires complex layout
2. High initial cost.
3. Lot of area is wasted for bunds.
4. Labour requirement

3. Furrow irrigation/ Ridges and Furrow method
Furrow irrigation is used in the irrigation of widely spaced row crops like maize,
sugarcane, potato, tomato, cotton, tobacco, banana etc.
Types of Furrow irrigation
1. Corrugation:
2. Every furrow irrigation
3. Alternate furrow irrigation
4. Broad bed furrow irrigation
5. Surge irrigation

II. Sub-surface irrigation
Water is applied below the ground by creating and maintaining an artificial
water table at some depth.
Advantages:
•Less water requirement
•Weed problem is less due to dry surface soil.
•The efficiency of water use is 70-75%.
Disadvantages:
1. Sub-surface deep percolation losses.
2. Maintenance of pipeline is difficult.
3. Higher cost.

III. Sprinkler Irrigation
•Sprinkler irrigation is also called as ‘Over head irrigation’
•Water is sprayed somewhat resembling rainfall.
•Effortless irrigation
•Discharge rate: 75-150 ltr/hour
Advantages
1. Higher application efficiency and WUE- helps to conserve water
up to 70%.
2. Reduced water loss – Water loss is about 15% (50-70% in surface
irrigation)
3. Effective water management
4. Land leveling, bunding and channels are not necessary.
5. Good method for sandy soils, shallow soils and for steep slopes
and rolling topography.
6. Frost control - protect crops against frost.
7. Protect the crop from high temperature.

Disadvantages
a) High initial cost and high maintenance requirements.
b) Application efficiency is affected by high wind speed.
c) Higher evaporation losses.
d) Higher energy requirement.
e) Use of saline water may damage the foliage of crops.
Suitability
I. Suitable to regions of water scarcity.
II. Suitable for tank and canal irrigated areas to economize the
water.
III. Suitable areas of steep slopes and rolling topography.
IV. Suitable for all types of soils, more particularly sandy and
gravelly soils.
V. Suitable for most of the annual crops- wheat, sorghum, cotton,
potato, tobacco, groundnut, ragi, vegetables etc.

Components of sprinkler system:
1.Pumping unit
2.Pipeline – mains, sub-mains and laterals
3.Couplers
4.Sprinklers
5.Other accessories such as filter, valves, bends, plugs and
riser pipes.

Rotating head (or) revolving sprinkler system are of 3 types.
1. Conventional system/small rotary sprinklers
2. Boom type and self propelled sprinkler system
3. Mobile rain gun/large rotary sprinklers
Based on the portability, sprinkler systems are classified into:
1. Portable system 4. Solid set system
2. Semi portable system 5. Permanent system
3. Semi-permanent system

Drip irrigation slogan: More crop per drop of water

One of the latest and most efficient methods of irrigation.
It was first designed at Israel by Symcha Blase, a water engineer
in 1959.
Method of watering plants frequently and at low volume to
meet the consumptive use of the plants with minimum loss of water
through deep percolation and evaporation.
The system applies water slowly to keep the soil moisture within
the desired range for plant growth.
Discharge rate: 2-4 liter per hour
Drip or trickle irrigation

Components of sprinkler system:
1.Pumping unit
2.Pipeline – mains, sub-mains and laterals
3.Filter unit
4.Emitter/ dripper
5.Fertilizer tank

Advantages of drip irrigation
1. Water saving– WUE more than 90%
2. Uniform water distribution
3. No land leveling required
4. No soil erosion, no loss of nutrients
5. Better weed control
Disadvantages
1. High initial cost
2. Drippers are susceptible to blockage
Suitability
•It is suitable to all vegetables, field crops and orchard crops.
•It is suitable to all types of soils.
•It is most suited to coarse sandy

Other types of micro-irrigation systems
1. Pitcher irrigation: Pitcher irrigation is an indigenous method of micro irrigation
which consists of mud pots of 20 litres capacity with a small hole made little above
the bottom.
2. Microjet irrigation: In microjet irrigation, water leaves the jets at a pressure of
nearly one bar. This gives throw distance of 1 to 4 m with water discharge of 5 to 160
litres per hour.
3. Microsprinkler irrigation: The water is distributed by rotating parts which
produce a rotating jet of water.
4. Bubbler irrigation: Bubbler irrigation is relatively a new system which is
designed to reduce energy requirements through inexpensive, thin walled, corrugated
plastic pipes. Water bubbles out of open vertical tubes. Bubbler system is suitable for
widely spaced crops such as mango, sapota, orange, coconut, grapes etc.
5. Pulse irrigation system: Supplies water in series of pulses or discharges with an
interval of 5, 10 or 15 minutes. The advantage is reduction in clogging problems

Ill effects of poor water management
When the soil contains excess water than that can be accommodated in the pore
spaces, it is said that the field is water logged.
Excess moisture or water logging occurs due to heavy and continuous rains or
due to wrong irrigation methods
Effects of excess moisture/ water logging
1. Poor oxygen availability and high CO2 concentration in soil.
2. Plant roots is affected and may lead to death of roots.
3. Seed germination is affected.
4. Reduced uptake of water and nutrients due to poor aeration.
5. Leaching of plant nutrients leading to their reduced availability.
6. Deficiency of nutrients or in some cases toxicities.
7. Reduced activity of soil microbes.
8. Accumulation of salts leading to salinity and alkalinity
9. Difficulty for cultural operations.
10.Incidence of pest and diseases.

Drainage
It is the process of removal of excess water as free or
gravitational water from the surface and sub-surface of farm lands
with a view to avoid water logging and to create favourable soil
conditions for optimum plant growth.
Situations requiring drainage
1. High water table
2. Water ponding on the surface for longer periods
3. Excessive soil moisture content above FC
4. Areas of salinity and alkalinity where annual evaporation
exceeds rainfall and capillary rise of ground water occurs
5. Humid region with continuous heavy rainfall
6. Flat land with fine texture soil
7. Low lying flat areas surrounded by hills.

Benefits of drainage
1. Drainage lowers underground water table so as to facilitate
increased root zone depth.
2. Drainage improves soil aeration and temperature.
3. Long time of use of agricultural land without any deterioration.
Types of surface drainage
1. Lift drainage
2. Gravity drainage
3. Field surface drainage
4. Ditch drainage
Types of sub-surface drainage: 4 types
A. Tile drainage
B. Mole drainage
C. Vertical drainage
D. Well Drainage or Drainage wells

Quality of irrigation water
•The quality of irrigation water depends on the amount and type of salts present
in the water.
•The main soluble constituents in water are chlorides, sulphates, carbonates,
bicarbonates of Ca, Mg and Na. The other ions present in minute quantities are B,
Se, Mo and F.

Class EC (dS/m) Soils for which suitable
C1: Normal waters < 1.5 Suitable for all soils and crops.
C2: Low Salinity water 1.5 - 3
Suitable for most of the soils and crops.
No leaching is required.
C3: Medium Salinity
water
3 - 5
Suitable for crops with moderate salt
tolerance. Suitable for all crops after
moderate leaching.
C4: High Salinity water 5 - 10
Not suitable for poorly drained soils.
Soils with good drainage and tolerant
crops can only be used with leaching.
C5: Very high Salinity
water
> 10
Not suitable.
Highly salt tolerant crops can be grown
after excessive leaching.
Total Soluble Salts/Salinity level: Salt content in irrigation water is
measured as electrical conductivity (EC). Based on EC, irrigation water is
classified as

b. Sodium adsorption ratio (SAR): Hazards caused by Na+ is more dangerous
than salinity. SAR is used to express sodium hazard level.
Class SAR Remarks
S1: Low Sodium
water
< 10
Can be used for most of the crops &
soils.
S2: Medium Sodium
water
10 -
18
Can be used in coarse textured soils.
Fine textured soils need gypsum
application.
S3: High Sodium water 18 - 26
Requires special management viz.,
drainage, leaching & application of
manures and gypsum.
S4: Very high Sodium
water
> 26
Not suitable.

Irrigation management in Problematic soils
1. Providing drainage
2.Irrigation with good quality water
3.Reducing the irrigation water requirement
4.Selecting the crops of high adaptability
5.Breaking sub-surface impervious layer
6.Avoiding surface irrigation
7.Diversion of run-off water from catchment

Water budgeting
Water budgeting is the detailed account of the water receipt and expenditure
within the crop period for efficient and profitable farm management.
Components of water budget
1. Water supply
a. Precipitation (Rainfall +snow fall)
b. Irrigation water (reservoirs, tanks, ponds, wells, bore wells etc.).
c. Ground water contribution
2. Water demand
a) Crop ET (depends on soil, crop and climate)
b) Run-off and deep percolation losses
c) Irrigation efficiency (conveyance, application and storage efficiency)
3. Soil moisture content before and after the crop season or year

Economic use of irrigation water
Irrigation is practiced to achieve maximum yield per unit of land and
ultimately the profit.
1. Unlimited water supply conditions
a. Conservation of water/ reduction in the losses of water
1. Reduce conveyance losses by lining channels or by using pipelines.
2. Reduce direct evaporation during irrigation by avoiding midday sprinkling.
3. Reduce run-off and percolation losses by avoiding over irrigation.
4. Reduce evaporation from soil by mulching.
5. Reduce transpiration by weeds by proper weed control measures.
b. Enhancement of crop productivity
1. Select most suitable and marketable crops for the region.
2. Use optimal timing for tillage, planting and harvesting.
3. Use appropriate pest and disease control measures.
4. Follow effective nutrient management.
5. Conserve soil and avoid salinization.

2. Limited water supply conditions
1. Selection of appropriate crops and varieties.
2. Use of drought resistant crops.
3. Use of short duration varieties.
4. Irrigation at sensitive growing periods of crop (critical stages).
5. Deficit irrigation at crop growth stages where loss in yield and quality is
minimum.
6. Increasing conveyance and application efficiency of water by reducing losses.
7. Effective utilization of rainfall.
8. Conservation tillage/ stubble mulching.
9. Water saving irrigation methods- Alternate/skip furrow irrigation, Micro-
irrigation.

Irrigation plan
Irrigation plan is a systematic record of all information of a land unit and crop
grown in a given time.
1. Efficient utilization of available water
2. Irrigation scheduling
3. Estimation of various losses viz., conveyance, application etc and ways to
minimize them.
4. Identification of crop plan or cropping pattern based on water availability.
5. Cost – Benefit analysis

1) Prepared based on water resource availability
2) Aim at minimizing water losses and maximizing profit
3) Emphasize on crops adopted to the local situation/ region
4) Water distribution based on crop need and soil capacity
5) Water budgeting accounts the efficiencies of irrigation
6) Necessary water measuring devices, water control, distribution & other on farm
irrigation structures are clearly defined
7) Considers the conjunctive use of rain water
8) Has layout map showing all the ground details
9) Has cost- return analysis
10) Contingent plan and mid-season correction strategies are part of irrigation plan
Features of irrigation plan

Practical 1: STUDY OF SOIL SAMPLING TECHNIQUE AND
DETERMINATION OF SOIL MOISTURE CONTENT BY DIRECT
LABORATORY METHODS
PROCEDURE
Record the weight of empty moisture can along with lid (A).
Collect a sample of soil about 50g in moisture can and cover it immediately with the
lid.
Record the weight of soil sample along with can and lid (B).
Dry the sample in an oven at 105oC for about 24 hours or till the constant weight is
obtained.
Record the dry weight of sample along with can and lid (C).
Calculate the moisture content by using the formula.
Fresh weight of the soil sample (WS1) = B-A
Dry weight of the soil sample (WS2) = C-A
1. GRAVIMETRIC METHOD (WEIGHT BASIS)
2. VOLUMETRIC METHOD (VOLUME BASIS)

Practical 2: STUDY OF DETERMINATION OF SOIL MOISTURE
CONTENT BY DIRECT FIELD METHODS
1. APPEARANCE AND FEEL METHOD
2. SPIRIT BURNING METHOD
3. RAPID MOISTURE METER METHOD

Practical 3: STUDY OF DETERMINATION OF SOIL MOISTURE
CONTENT BY indirect METHODS
1.PRESSURE MEMBRANE /PRESSURE PLATE APPARATUS METHOD
2. SULPHURIC ACID METHOD
3. NEUTRON MOISTURE METER METHOD
4. TIME DOMAIN REFLECTOMETRY (T.D.R.) METHOD
5. MICROWAVE REMOTE SENSING METHOD

Neutron moisture meter Pressure Plate apparatus
Microwave method
TDR method

Practical no 04: STUDY OF DETERMINATION OF SOIL MOISTURE
CONTENT BY TENSIOMETER METHOD

Exp. No. 05: STUDY OF DETERMINATION OF SOIL MOISTURE
CONTENT BY GYPSUM RESISTANCE BLOCK METHOD
Gypsum resistance blocks are used for indirect measurement of soil moisture
content.
Resistance blocks work on the principle that the flow of electricity between two
electrodes in a porous block, embedded in soil, depends on the moisture content of
the soil.
Resistance to the flow of electricity in a porous medium is inversely proportional
to the moisture content.
The commonly used electrical resistance instrument was developed by Bouyoucos
(1949) and hence, they are called as ‘Bouyoucos moisture meter’.
Generally these read about 400-600 ohms at field capacity and 50,000-75,000
ohms at wilting point.

Exp. No. 06 & 7: STUDY OF DETERMINATION OF MAXIMUM WATER
HOLDING CAPACITY, FIELD CAPACITY AND PWP OF SOIL

Exp. 08: STUDY OF MEASUREMENT OF IRRIGATION WATER BY VOLUME,
AREA-VELOCITY AND WATER METER METHODS
1
2
3

1. RECTANGULAR WEIR
Exp. 09: STUDY OF MEASUREMENT OF IRRIGATION
WATER BY WEIRS, ORIFICE, PARSHALL FLUME AND CUT
THROAT FLUME METHODS
Q = 0.0184 LH1.5
Where, Q = Discharge (liters/second)
L = Length of crest (cm)
H = Head over the weir (cm)

2. TRAPEZOIDAL WEIR
Here, L =
L1 + L2
2
Q = 0.0186 LH1.5
Where, L1 = Width of notch at bottom level (cm)
L2 = Width of notch at top level (cm)
H = Head over the weir (cm)

3. V-Notch
Q = 0.0138 H2.5
Where, Q = Discharge (liters/second)
H = Head (cm)

Experiment no.13 & 14: STUDY OF SCHEDULING OF
IRRIGATION
A. Based on plant water indication
1. Wilting symptoms
2. Indicator plants
3. Development of pigment
4. Critical stages of crop growth
5. Growth rate
6. Stomatal movement
7. Leaf reflectance
8. Plant water content
9. Transpiration ratio
B. Based on soil water indication
I. Soil appearance
II. Soil moisture deficit
III. Soil moisture suction/tension
C. Based on soil moisture suction
cum critical stages of crop growth
D. Based on depth-interval-yield
approach
E. Based on Stress Day Index
(S.D.I.)
F. Based on climatological approach
By using empirical formulae
I.W./C.P.E. ratio

Experiment. No.: 16 & 17
STUDY OF COMMON FORMULA IN IRRIGATION
WATER CALCULATIONS

Water management in horticultural crops

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Water management in horticultural crops

Similar to Water management in horticultural crops (20)

Recently uploaded

Recently uploaded (20)

Water management in horticultural crops