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 Introduction to irrigation

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عدد الرسائل : 213
العمر : 29
الموقع : http://www.extratechnology.co.uk/
تاريخ التسجيل : 24/05/2008

مُساهمةموضوع: Introduction to irrigation   الأحد يوليو 20, 2008 1:49 am

Irrigation,
defined as a system used for watering crops and plants, requires proper
design and operation along with experience, science and even some art.



Irrigation, defined as a system used for
watering crops and plants, requires proper design and operation along
with experience, science and even some art. A basic irrigation system
must begin with a landscape design that specifies plants suitable for
the topography, soil, climate and water. After creating the basic
irrigation system design, the type of irrigation system must be
determined. Three basic irrigation types are used in horticulture
applications. These are sprinkler, drip and surface. Each of these
irrigation systems have variations adaptations that work with certain
conditions. Other factors to consider are plant water requirements,
condition of water and its supply, soil type, condition and topography,
microclimate concerns and irrigation scheduling constraints.
Sprinkler systems, commonly used for turf applications, depend
on the size and shape of the area irrigated as well as the flow rate
and pressure of the water supply. Variations of this system include
rotating sprinklers, fixed spray sprinklers and drip and micro
sprinklers.




Rotating sprinklers, either full or part
circle rotating sprinklers, are used on large areas, such as golf
courses, parks, commercial or large residential landscapes. This type
of sprinkler system can have single or multiple nozzles, gears, cam or
impact driven, spacing from 35 to 115 feet, operating pressure from 40
to 100 psi, and flow rates from 6 to 65 gpm. Rotating sprinklers can
even have built-in valves, which is a valve located in the sprinkler
head and/or pressure regulators. Fixed Spray Sprinklers, often referred to as pop-up sprinklers,
have a pattern that can be full, part circle or rectangular with
radiuses from 4 to 22 feet. This type sprinkler system offers several
angles of spray trajectory with application rates ranging from less
than 1 to over 2 inches per hour. When planning irrigation scheduling
for this type of sprinkler system, consider the high application rates
of the spray nozzles to prevent runoff. Drip and Micro-Sprinklers, a cross between spray nozzles and
drip irrigation, are well suitable for ornamental plantings and as well
as a single tree or shrubs. This type of sprinkler system has a low
flow rate, low application rate, small radius that range from 4 to 12
feet and operate with low pressures. Micro sprinklers require filtered
and pressure regulated water.
Drip irrigation, also known as micro irrigation, applies water
to the soil at point locations using low controlled flow rates and drip
emitters that discharge at a rate of .5 to 2 gallons per hour. These
emitters can be pressure compensating and apply a nearly constant
application rate over a wide range of pressures. Drip irrigation, used
on individual plants or groupings of plants, should include a filter
and pressure regulator. Drip tubing and bubblers are two types of drip
irrigation. Drip tubing applies water using equally spaced emitters, 6 to 60
inches, along a semi-rigid tube. Depending on the drip irrigation
tubing type, operating pressures range from 5 to 20 psi. Drip
irrigation, installed on top of the soil or buried in the soil, is used
to irrigate turf. Bubble irrigation does not have drip emitters, but works very
similarly; the difference is that bubble irrigation uses a higher flow
rate that ranges from 2 to 6 gpm. The flow rate of bubble is higher
than the soil intake rate, resulting in a flooding situation. When this
situation occurs, the infiltration of the soil continues after the
bubbler has been shutoff. Only use bubble irrigation where small basins
are capable of being constructed to contain the water and the ground is
level. Surface irrigation, also known as flood irrigation, is the least
commonly used system. This system applies deeper irrigation and
requires higher flow rates for shorter periods. Use surface irrigation
on leveled and diked turf areas only if the soil infiltration is slow
enough for the water to flow over the entire area. In a surface
irrigated system, soil is used as the distributing and infiltration
system and the system requires careful design for it to be efficient.
Occasionally, surface irrigation is used for furrow or diked irrigation
for landscapes and gardens. Irrigation systems are designed to supply an adequate amount of
water in a timely manner to plants. Keeping this in mind is important
when designing an irrigation system. Irrigation zones and irrigation
system layout help achieve this goal. Select irrigation zones by
determining the plants’ water requirements with the availability of the
water supply. For instance, sprinkler systems are better for turf areas
and landscape plants do better with low-flow drip or micro-spray
irrigation. Controllers of irrigation systems vary as much as the
systems themselves. The more expensive the controller, the more options
they have to offer such as being capable of separating irrigation
frequency for different zones. These more expensive controllers also
require more effort to program and understand. Often times the simpler
controllers are the more practical, less expensive and will have the
capability to accomplish the task. Sometimes using two or more simpler
separate controllers instead of one more expensive one is cost
effective.
Irrigation system layout is also very important when installing
an irrigation system. Controllers, which are the time clock, along with
valve boxes should be accessible and be protected from rain and direct
sunlight. Before laying out any irrigation hardwater, draw a scale that
shows the irrigated property along with the location of the plants.
Base the selection of the sprinklers on the size of the irrigated
property. Sprinkler location should begin in the corners where a
sprinkler will be located, and place the next sprinkler by using
head-to-head sprinkler spacing. Drip systems, laid out a little
differently, begin by locating the emitters and positioning them next
to the individual plants or plant groupings that they will irrigate.
The spacing of these emitters is determined on the spreading of the
root system and the soil type. After the initial placement of the
emitters, install the remaining water supply lines.
Successful irrigation depends on all the factors being present.
These factors are the water source, the water meter, backflow
prevention and vacuum breaker device, valves and wire, pressure
regulator, filtration system, controller and related hardware, pipe and
fittings, sprinklers, drip emitters, bubblers or tubing. Every one of
these factors is important.

eng /kareem




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Introduction to irrigation
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