ISO 24120-1:2022
(Main)Agricultural irrigation equipment — Guideline on the implementation of pressurized irrigation systems — Part 1: General principles of irrigation
Agricultural irrigation equipment — Guideline on the implementation of pressurized irrigation systems — Part 1: General principles of irrigation
This document provides a guideline for the implementation of pressurized irrigation systems. It is applicable to small-scale family agriculture and large-scale commercial agriculture, in open fields or within enclosed growing structures (e.g. greenhouse, net house). This document is intended for the use of agriculture ministries, agronomists, irrigation planners, farmers and end-users.
Matériel agricole d'irrigation — Lignes directrices relatives à la mise en œuvre des systèmes d'irrigation sous pression — Partie 1: Principes généraux d'irrigation
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 24120-1
First edition
2022-06
Agricultural irrigation equipment —
Guideline on the implementation of
pressurized irrigation systems —
Part 1:
General principles of irrigation
Matériel agricole d'irrigation — Lignes directrices relatives à la mise
en œuvre des systèmes d'irrigation sous pression —
Partie 1: Principes généraux d'irrigation
Reference number
ISO 24120-1:2022(E)
© ISO 2022
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ISO 24120-1:2022(E)
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© ISO 2022
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ISO 24120-1:2022(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Water management .1
4.1 Soil-water relationship . 1
4.1.1 General . 1
4.1.2 Solid particles and porosity . 1
4.1.3 Soil water . 2
4.1.4 Determination of amount of water in a soil layer . 3
4.1.5 Water retention in soils . 3
4.1.6 Soil water potential and movement of water in the soil . . 4
4.1.7 Water distribution in the soil . 5
4.1.8 Distribution of salts in the irrigated volume . 11
4.1.9 Salt concentration as a function of soil water content . 16
4.1.10 Nutrients distribution . 16
4.1.11 Root distribution . 17
4.2 Water sources . 17
4.2.1 Sources . 17
4.2.2 Effects on soil and crops main parameters in relation to chemical/
biological quality of the irrigation water . 17
4.2.3 Effects on filters and irrigation emitters in relation to chemical and
physical parameters . 18
4.3 Water distribution network: main, sub-main, distribution pipes . 18
5 Pressurized irrigation design .19
5.1 General . 19
5.2 Data collection . 19
5.2.1 Soil characteristics . 19
5.2.2 Surface topography . 19
5.2.3 Climate . 19
5.2.4 Water source and quality . 19
5.2.5 Crops characteristics (orchards, field crops, vegetables) . 19
5.2.6 Local water use regulations . 19
6 Calculating irrigation scheduling .19
6.1 General . 19
6.2 Soil — Water reservoir . 19
6.2.1 General . 19
6.2.2 Calculation of water available for the crop in the root zone .20
6.2.3 Calculation of the management allowable deficit . 20
6.2.4 Net irrigation depth (NID) . 20
6.2.5 Gross irrigation depth (GID). 20
6.2.6 Leaching . 21
6.3 Crop water requirements. 21
6.4 Irrigation interval . 22
Annex A (informative) Example of soil data .23
Annex B (informative) Methods for the determination of the wetted volume (bulb)
dimensions .24
Annex C (informative) Salt tolerance of selected crops .27
Bibliography .28
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ISO 24120-1:2022(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
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on the ISO list of patent declarations received (see www.iso.org/patents).
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 23, Tractors and machinery for agriculture
and forestry, Subcommittee SC 18, Irrigation and drainage equipment and systems.
A list of all parts in the ISO 24120 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
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INTERNATIONAL STANDARD ISO 24120-1:2022(E)
Agricultural irrigation equipment — Guideline on the
implementation of pressurized irrigation systems —
Part 1:
General principles of irrigation
1 Scope
This document provides a guideline for the implementation of pressurized irrigation systems.
It is applicable to small-scale family agriculture and large-scale commercial agriculture, in open fields
or within enclosed growing structures (e.g. greenhouse, net house).
This document is intended for the use of agriculture ministries, agronomists, irrigation planners,
farmers and end-users.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
wetting front
boundary between the wetted region and the drier region of soil during infiltration
[SOURCE: Glossary of Soil Science terms, modified — 'dry' substituted with 'drier'.]
4 Water management
4.1 Soil-water relationship
4.1.1 General
The soil is a three-phase system (mineral and organic solid particles, water and air). It is a reservoir
of water used by plants. To design an irrigation system, the soil-water-plant relations, as described in
Clause 4, should be considered. Examples of values of soil physical parameters are presented in Annex A.
4.1.2 Solid particles and porosity
The soil volume is made up of solid particles of different sizes (sand, silt and clay) and pores. The relative
content of the three groups of particles defines the soil texture.
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ISO 24120-1:2022(E)
The volume not filled by the solid particles defines the soil pores. The total volume and size of pores
depend on the soil texture. The higher the soil clay content, the higher the total porosity of the soil and
lower pore size. The total porosity is between 35 % to 40 % in sandy soils, 50 % in medium soils and
can reach 60 % for clay soils.
Under conditions of soil water saturation, all the pores of the soil are full of water and, as a consequence,
do not contain air.
4.1.3 Soil water
The percentage of water relative to the mass of solids is the relation between the mass of the water and
the mass of the particles [as shown in Formula (1)] and is commonly determined by the gravimetric
method.
m
w
w=×100 (1)
m
s
where
w is the gravimetric water content (%);
m is the mass of the water (g);
w
m is the mass of dry soil or mass of solids (g).
s
The gravimetric method is the most accurate method (i.e., the standard method) for determining the
soil water, and it consists of drying samples of soil in an oven at 105 °C for 24 h (or until the sample
reaches steady mass). The gravimetric water content (w) can be obtained using Formula (2):
mm−
w+cd+c
w= ×100 (2)
mm−
d+c c
where
m is the tare of the container;
c
m is the mass of wet soil + container;
w+c
m is the mass of dry soil + container.
d+c
The percentage of water relative to soil volume (i.e. the volumetric water content) is the relation
between the volume of water and the total volume of soil. See Formula (3).
V
w
θ= ×100 (3)
V
t
where
θ is the volumetric water content (%);
3
V is the volume of the water (cm );
w
3
V is the total volume of the soil (cm ).
t
The gravimetric method can be used to determine the soil bulk density, the gravimetric water content
and the volumetric water content. For that purpose, undeformed soil samples should be collected
using the Uhland soil sampler or other similar device for extracting undeformed samples. The soil
bulk density is obtained by Formula (4), in which the total volume of soil is equal to the volume of the
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ISO 24120-1:2022(E)
-3
container. Assuming the water density as a constant equal to 1 g cm , the volumetric water content is
obtained by Formula (5).
m
s
ρ = (4)
b
V
t
θρ=×w (5)
b
where
θ is the volumetric water content (%);
w is the gravimetric water content (%);
-3
ρ
is the soil bulk density (g · cm ).
b
4.1.4 Determination of amount of water in a soil layer
The amount of water in a soil layer can be expressed as water depth (mm). See Formula (6).
θ
hn=× (6)
100
where
h is the water depth in a particular layer of soil (mm);
θ is the volumetric water content (%);
n is the thickness of the particular layer (mm).
NOTE
-2 3 -1
1 mm = 1 l m = 10 m ha
2
1 ha = 10 000 m
4.1.5 Water retention in soils
Knowing the amount of water in the soil without knowing other soil characteristics is insufficient to
determine the amount of water available for crops, in order to programme the irrigation regime.
The water held in the soil pores is a result of the surface tension of the water in contact with the air and
the contact angle between the water and the soil particles. As a result, there is a retention force in the
soil pores (capillarity) that increases with a decrease in the diameter of the soil pores.
Each soil has its own characteristic water retention curve (the water tension relative to the change in
the moisture) according to its texture and structure that defines its pore size distribution.
According to the water retention curve, three water conditions in the soil can be defined.
— Saturation: after an excessive rainfall or irrigation, all the soil pores become full of water, and
drainage downward immediately starts, faster in sandy soils and slower in soils with increasing
clay content.
— Field capacity (θ ): the water content in the soil 1 to 3 days after saturation condition and drainage
FC
has largely ceased.
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— Wilting point (θ ): as water is extracted from the soil through evapotranspiration (from plants
WP
and soils), the water tension is increased (up to 1,5 MPa) at a value whereby most plants can no
longer extract water and wilt permanently.
The total available water of the soil can be calculated as the difference between the water content at
field capacity and permanent wilting point, expressed in percentage. See Formula (7).
θθ−
FC WP
Wn= (7)
TA
100
where
W is the total available water in a particular soil layer (mm);
TA
θ is the volumetric water content at the field capacity (%);
FC
θ is the volumetric water content at the wilting point (%);
WP
n is the thickness of the particular layer (mm).
4.1.6 Soil water potential and movement of water in the soil
The water in the soil is subject to a number of forces, which cause the potential of the soil water to differ
from the potential of pure and free water. These forces result from the attraction of water to the solid
matrix of the soil (clay particles and organic matter), as well as the presence of dissolved salts, and the
influence of the force of gravity. The total water potential in the soil can be presented as the sum of the
individual contribution of each of these forces, as expressed using Formula (8).
ΨΨ=+ΨΨ++. (8)
tg mo
where
Ψ is the total water potential in the soil;
t
Ψ is the gravitational potential;
g
Ψ is the matrix potential;
m
Ψ is the osmotic potential;
o
… are expressions for other terms of the potential of water in the soil that exist theoretically.
The direction of water movement between two points in the soil is determined by the existence of a
difference in the total water potential (Ψ ). The movement occurs from the point of highest potential
t
to the point of lower potential. In the movement of water between two points within the soil, the osmotic
potential (Ψ ) is negligible (in the absence of a semi-permeable membrane between the two points), so
o
that the total potential is restricted to the sum of the gravitational potential (Ψ ) and the matrix
g
potential (Ψ ) (ΨΨ=+Ψ ).
m tg m
The gravitational potential of water at a given point in the soil is determined by the relative elevation of
the point in the soil (relative to the surface, for example).
The matrix potential is also called capillary potential. It results from capillarity (which depends on the
size of the pores in the soil) and water adsorption forces (by attraction to solid soil particles, especially
clay and organic matter).
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ISO 24120-1:2022(E)
4.1.7 Water distribution in the soil
4.1.7.1 Methods with total surface wetting
Irrigation methods with total surface wetting (surface basin irrigation and some sprinkler irrigation)
are designed to perform a uniform distribution of water over the entire surface of the soil, similar to
natural rainfall. The driving force in the movement of water in the soil during irrigation is the force of
gravity (the difference in the gravitational potential of soil water between the surface and the deeper
layers of the soil) and the difference in the matrix potential of the soil between both sides of the wetting
front.
In general, the wetting front is a plane that advances in parallel to the soil surface. The horizontal
movement of water occurs when there is a difference in soil moisture, that is, a difference in the matrix
potential between two points at the same depth in the soil. In methods with total surface wetting, this
difference exists only within the boundaries of the irrigated plot in which the contact plane between
the wet zone and the dry zone (the wetting front in the plot boundaries) represents a very small area in
relation to the surface of the area and the wetting front in the vertical direction. This is why the lateral
movement is very small in relation to vertical movement, and the volume wetted by the movement of
water in the horizontal direction is minimal in relation to the total volume of soil irrigated. The water
pattern in basin is shown in Figure 1 and in sprinkler irrigation in Figure 2.
In basin irrigation, at the ideal wetting pattern, there are small percolation losses close to the field
channel, and in consequence a low depth of percolation at the opposite end. When the inflow rate is not
enough, percolation is high near the canal, and the depth of percolation towards the end is lower than in
optimal conditions (see Figure 1).
In sprinkler irrigation, the uniform water distribution on the soil surface is obtained by establishing
a sufficient overlap of distribution patterns from adjacent sprinklers. The degree of overlap depends
on the characteristic distribution pattern of the individual sprinkler, which in turn is a function of the
sprinkler type, height of sprinklers above crop, nozzles, pressure head and wind conditions. The degree
of overlap and uniformity is also dependent on the speed of movement and whether a 30 s, 60 s, 120 s
(or other) setting is used for the percent timer.
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a) Ideal wetting pattern
b) Wetting pattern with insufficient flow rate
Key
1 field channel
2 bund
3 root zone
4 low percolation losses
5 high percolation losses
6 too dry
[1]
Figure 1 — Basin irrigation water distribution
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ISO 24120-1:2022(E)
a) Wetting pattern for a single sprinkler
b) Wetting pattern of several sprinklers with superposition between wetting zones
Key
1 lateral
2 sprinkler
3 spacing
4 wetted zone
[1]
Figure 2 — Sprinkler irrigation
4.1.7.2 Methods with partial surface wetting
4.1.7.2.1 General
In irrigation methods with partial soil wetting (furrows, drip irrigation, micro-sprinklers and some
cases of irrigation on moving equipment such as LEPA – low energy precision application), the wetting
zone is characterized by having a special shape due to the forces that act on the water during its
infiltration and its movement in the soil. Water is moved by the difference in the total potential of water
in the soil [see Formula (8)]. In the vertical movement, the differences in the gravitational potential act
as well as in the matrix potential. In the horizontal movement there are only differences in the matrix
potential.
The general tendency is that the vertical movement (gradient in the matrix potential and the
gravitational potential) is greater than the horizontal movement (result of the gradient in the matrix
potential only). The difference between the two directions of movement will be greater as the content
of clay in the soil becomes lower. This is because the difference in the potential matrix between the wet
zone of the soil and the dry zone is greater in higher clay content, while there is no difference in the
gravitational component between the soils, whatever their texture.
4.1.7.2.2 Furrow irrigation
The water flows in the furrow and infiltrates down and to the sides of an individual furrow (see
Figure 3).
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ISO 24120-1:2022(E)
Key
A sandy soil
B loam soil
C clayey soil
1 wetted zone
[1]
Figure 3 — Movement of water in irrigation by furrows in soils of different texture
4.1.7.2.3 Drip irrigation
Below and around the dripper, where the water drops drop by drop, a wetted soil zone is formed, within
it three zones can be distinguished (see Figure 4):
— Saturated zone: immediately below and around the dripper a saturated zone is formed, from which
the water moves towards the interior of the soil. In this area there is excess water and lack of air.
Especially in soils of medium or clayey texture there is a small accumulation of water on the surface,
from which the water infiltrates into the saturated zone.
— Equilibrium zone: it is an intermediate zone, in which the moisture content is close to field capacity,
so there is an optimal ratio between the water and air content.
— Wetting front: it is the boundary between the intermediate zone and the dry zone or with moisture
content similar to that existing at the time of beginning of irrigation. In this area there is a deficit of
humidity and the aeration of the soil is maximal.
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Key
A clayey soil
B sandy soil
H horizontal dimension
V vertical dimension
1 saturated zone
2 equilibrium zone
3 dry zone (wetting front)
4 dripper
Figure 4 — Wetting bulb in the drip irrigation in two soils of different texture
The shape and dimensions of the wetting zone (bulb) depend on five factors:
— Soil: when a certain amount of water is applied, the bulb that forms on a clayey soil (with a low
hydraulic conductivity in saturated soil) will be shallower and wider compared to a sandy soil
(with a high saturated hydraulic conductivity). In the latter, the vertical dimension will be more
developed, while the horizontal dimension will be narrow.
— Dripper discharge: for a given soil, an increase in the dripper discharge means an increase in the
radius of the saturated zone, i.e. a wider and more superficial bulb. For the same dripper discharge,
the higher the soil clay content, the greater the radius of the saturated zone.
— Duration of irrigation: the horizontal dimension increases from the irrigation beginning and as long
as it continues, up to a certain limit that also depends on the texture of the soil and the discharge
of the dripper. Above this limit the movement of water will be mainly in the vertical direction, thus
decreasing the irrigation efficiency due to the loss of water by drainage below the root zone.
— Irrigation frequency: as the water content in the soil decreases, the water tension in the soil
increases. The hydraulic conductivity of soil has a wide influence on the behaviour of the water
in the soil wetting from a dripper. The hydraulic conductivity decreases exponentially with an
increase in the water tension in the soil (decrease in water content), and the movement of the water
is slower. Under these conditions, the relative importance of the matrix potential is greater than the
gravitational potential, resulting in a more accentuated horizontal movement.
— Calculation of the bulb dimensions and drippers spacing: the dripper spacing is the spacing
(distance) between drippers along a lateral line. The optimum distance between drippers is that
which represents 80 % of the diameter wetted by an individual dripper, which was calculated or
estimated in the field. With this spacing, an overlapping will be obtained between the wetted areas
of neighbouring drippers. At the same time, a wet strip will be received along the drippers lateral.
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Examples of some means of estimating the wetted area dimensions are presented in Annex B.
Manufacturers of drip irrigation systems present in their catalogues the recommended spacing data,
according to their experience, for different soils and crops.
4.1.7.2.4 Micro-sprinkler irrigation
Similar to drip irrigation, the wetting of the soil in this method of irrigation is partial. There are
different types of micro-sprinklers with different water d
...
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