Editing Irrigation (section)

== Irrigation methods ==
There are several methods of irrigation. They vary in how the water is supplied to the plants. The goal is to apply the water to the plants as uniformly as possible, so that each plant has the amount of water it needs, neither too much nor too little. Irrigation can also be understood whether it is ''supplementary'' to rainfall as happens in many parts of the world, or whether it is '''full'' irrigation' whereby crops rarely depend on any contribution from rainfall. Full irrigation is less common and only happens in arid landscapes experiencing very low rainfall or when crops are grown in semi-arid areas outside of any rainy seasons.

===Surface irrigation===
{{Main|Surface irrigation}}

[[File:LevelBasinFloodIrrigation.JPG|thumb|Basin [[flood irrigation]] of [[wheat]]]]

Surface irrigation, also known as gravity irrigation, is the oldest form of irrigation and has been in use for thousands of years. In ''surface'' (''furrow,'' ''flood'', or ''level basin'') irrigation systems, water moves across the surface of agricultural lands, in order to wet it and infiltrate into the soil. Water moves by following gravity or the slope of the land. Surface irrigation can be subdivided into furrow,'' border strip or basin irrigation''. It is often called ''flood irrigation'' when the irrigation results in flooding or near flooding of the cultivated land. Historically, surface irrigation is the most common method of irrigating agricultural land across most parts of the world. The water application efficiency of surface irrigation is typically lower than other forms of irrigation, due in part to the lack of control of applied depths. Surface irrigation involves a significantly lower capital cost and energy requirement than pressurised irrigation systems. Hence it is often the irrigation choice for developing nations, for low value crops and for large fields. Where water levels from the irrigation source permit, the levels are controlled by dikes ([[levee]]s), usually plugged by soil. This is often seen in terraced rice fields (rice paddies), where the method is used to flood or control the level of water in each distinct field. In some cases, the water is pumped, or lifted by human or animal power to the level of the land.
[[File:Residential flood irrigation in Phoenix, Arizona, in the United States of America.jpg|thumb|Residential flood irrigation in Phoenix, Arizona, US]]
Surface irrigation is even used to water urban gardens in certain areas, for example, in and around [[Phoenix, Arizona]]. The irrigated area is surrounded by a [[berm]] and the water is delivered according to a schedule set by a local [[irrigation district]].<ref>{{cite web|title=Flood Irrigation Service|url=http://www.tempe.gov/home/showdocument?id=3194|publisher=City of Tempe, Arizona|access-date=29 July 2017}}</ref>

A special form of irrigation using surface water is [[spate irrigation]], also called floodwater harvesting. In case of a flood (spate), water is diverted to normally dry river beds (wadis) using a network of dams, gates and channels and spread over large areas. The moisture stored in the soil will be used thereafter to grow crops. Spate irrigation areas are in particular located in semi-arid or arid, mountainous regions.

===Micro-irrigation===
{{Main|Micro-irrigation}}

[[File:Dripperwithdrop.png|thumb|Drip irrigation – a dripper in action]]
''Micro-irrigation'', sometimes called '''localized irrigation''', '''low volume irrigation''', or '''trickle irrigation''' is a system where water is distributed under low pressure through a piped network, in a pre-determined pattern, and applied as a small discharge to each plant or adjacent to it. Traditional drip irrigation use individual emitters, subsurface drip irrigation (SDI), micro-spray or micro-sprinklers, and mini-bubbler irrigation all belong to this category of irrigation methods.<ref>{{cite book | last1 = Frenken | first1 = K. | chapter = Irrigation in Africa in figures&nbsp;– AQUASTAT Survey&nbsp;– 2005 | title = Water Report 29 | publisher = Food and Agriculture Organization of the United Nations | year = 2005 | url = ftp://ftp.fao.org/agl/aglw/docs/wr29_eng.pdf | archive-url = https://web.archive.org/web/20170706015452/ftp://ftp.fao.org/agl/aglw/docs/wr29_eng.pdf | url-status = dead | archive-date = 2017-07-06 | isbn = 978-92-5-105414-7 | access-date = 2007-03-14 }}</ref>

==== Drip irrigation ====
{{Main|Drip irrigation}}
[[File:dripirrigation.gif|thumb|Drip irrigation layout and its parts]]

Drip irrigation, also known as microirrigation or trickle irrigation, functions as its name suggests. In this system, water is delivered at or near the [[root]] zone of plants, one drop at a time. This method can be the most water-efficient method of irrigation,<ref>{{cite journal | last = Provenzano | first = Giuseppe | title = Using HYDRUS-2D Simulation Model to Evaluate Wetted Soil Volume in Subsurface Drip Irrigation Systems | journal = Journal of Irrigation and Drainage Engineering| volume = 133 | issue = 4 | pages = 342–350 | year = 2007 | doi = 10.1061/(ASCE)0733-9437(2007)133:4(342)| bibcode = 2007JIDE..133..342P }}</ref> if managed properly; evaporation and runoff are minimized. The field [[water efficiency]] of drip irrigation is typically in the range of 80 to 90% when managed correctly.

In modern agriculture, drip irrigation is often combined with [[plastic mulch]], further reducing evaporation, and is also the means of delivery of fertilizer. The process is known as [[fertigation]].

Deep percolation, where water moves below the root zone, can occur if a drip system is operated for too long or if the delivery rate is too high. Drip irrigation methods range from very high-tech and computerized to low-tech and labor-intensive. Lower water pressures are usually needed than for most other types of systems, with the exception of low-energy center pivot systems and surface irrigation systems, and the system can be designed for uniformity throughout a field or for precise water delivery to individual plants in a landscape containing a mix of plant species. Although it is difficult to regulate pressure on steep slopes, pressure compensating [[Drip irrigation#Emitter|emitters]] are available, so the field does not have to be level. High-tech solutions involve precisely calibrated emitters located along lines of tubing that extend from a computerized set of [[valves]].<ref>{{Cite web |title=Drip Irrigation System for sustainable agriculture |url=https://www.agriculturelandusa.com/2023/07/Drip-Irrigation-system.html |access-date=2024-03-07 |website=Agriculture land usa}}</ref>

=== Sprinkler irrigation ===
{{Further|Irrigation sprinkler}}
[[File:Crop sprinklers Rio Vista California 15 Jul 2004-002.jpg|thumb|Crop sprinklers near [[Rio Vista, California]], US]]
[[File:TravellingSprinkler.JPG|thumb|A traveling sprinkler at Millets Farm Centre, [[Oxfordshire]], United Kingdom]]

In ''sprinkler'' or overhead irrigation, water is piped to one or more central locations within the field and distributed by overhead high-pressure sprinklers or guns. A system using sprinklers, sprays, or guns mounted overhead on permanently installed risers is often referred to as a ''solid-set'' irrigation system. Higher pressure sprinklers that rotate are called ''rotors'' and are driven by a ball drive, gear drive, or impact mechanism. Rotors can be designed to rotate in a full or partial circle. Guns are similar to rotors, except that they generally operate at very high pressures of 275 to 900 kPa (40 to 130 psi) and flows of 3 to 76 L/s (50 to 1200 US gal/min), usually with nozzle diameters in the range of 10 to 50&nbsp;mm (0.5 to 1.9 in). Guns are used not only for irrigation, but also for industrial applications such as dust suppression and [[logging]].

Sprinklers can also be mounted on moving platforms connected to the water source by a hose. Automatically moving wheeled systems known as ''traveling sprinklers'' may irrigate areas such as small farms, sports fields, parks, pastures, and cemeteries unattended. Most of these use a length of polyethylene tubing wound on a steel drum. As the tubing is wound on the drum powered by the irrigation water or a small gas engine, the sprinkler is pulled across the field. When the sprinkler arrives back at the reel the system shuts off. This type of system is known to most people as a "waterreel" traveling irrigation sprinkler and they are used extensively for dust suppression, irrigation, and land application of waste water.

Other travelers use a flat rubber hose that is dragged along behind while the sprinkler platform is pulled by a cable.

==== Center pivot ====
{{Main|Center pivot irrigation}}
[[File:Center Pivot.jpg|thumb|A small center pivot system from beginning to end]]
[[File:Nelson A3000 Accelerator.png|thumb|Rotator style pivot applicator sprinkler]]
[[File:PivotWithDrops.JPG|thumb|Center pivot with drop sprinklers]]
[[File:WheelLineIrrigation.JPG|thumb|Wheel line irrigation system in [[Idaho]], US, 2001]]
[[File:Crop Triangle South Africa.jpg|alt=Center pivot irrigation|thumb|[[Center pivot irrigation]]]]
Center pivot irrigation is a form of sprinkler irrigation utilising several segments of pipe (usually galvanized steel or aluminium) joined and supported by [[truss]]es, mounted on wheeled towers with sprinklers positioned along its length.<ref>{{cite web
| url= http://www.thefencepost.com/article/20100525/NEWS/100529954
| title= Center pivot irrigation revolutionizes agriculture
| work= The Fence Post Magazine
| date= May 25, 2010
| access-date= June 6, 2012
| author= Mader, Shelli
| archive-url= https://web.archive.org/web/20160908232107/http://www.thefencepost.com/article/20100525/NEWS/100529954
| archive-date= September 8, 2016
| url-status= dead
}}</ref>
The system moves in a circular pattern and is fed with water from the pivot point at the center of the arc. These systems are found and used in all parts of the world and allow irrigation of all types of terrain. Newer systems have drop sprinkler heads as shown in the image that follows.

{{As of | 2017}} most center pivot systems have drops hanging from a U-shaped pipe attached at the top of the pipe with sprinkler heads that are positioned a few feet (at most) above the crop, thus limiting evaporative losses. Drops can also be used with drag hoses or bubblers that deposit the water directly on the ground between crops. Crops are often planted in a circle to conform to the center pivot. This type of system is known as LEPA (Low Energy Precision Application). Originally, most center pivots were water-powered. These were replaced by hydraulic systems (''[[T-L Irrigation]]'') and electric-motor-driven systems (Reinke, Valley, Zimmatic). Many modern pivots feature [[GPS]] devices.<ref>{{Cite web|url=https://www.agriculture.com/machinery/irrigation-equipment/gps-swing-arms-prove-their-worth|title=GPS SWING ARMS PROVE THEIR WORTH|last=Gaines|first=Tharran|date=January 7, 2017|website=Successful Farming|access-date=February 1, 2018}}</ref>

==== Irrigation by lateral move (side roll, wheel line, wheelmove) ====

A series of pipes, each with a wheel of about 1.5 m diameter permanently affixed to its midpoint, and sprinklers along its length, are coupled together. Water is supplied at one end using a large hose. After sufficient irrigation has been applied to one strip of the field, the hose is removed, the water drained from the system, and the assembly rolled either by hand or with a purpose-built mechanism, so that the sprinklers are moved to a different position across the field. The hose is reconnected. The process is repeated in a pattern until the whole field has been irrigated.

This system is less expensive to install than a center pivot, but much more labor-intensive to operate – it does not travel automatically across the field: it applies water in a stationary strip, must be drained, and then rolled to a new strip. Most systems use 100 or 130&nbsp;mm (4 or 5 inch) diameter aluminum pipe. The pipe doubles both as water transport and as an axle for rotating all the wheels. A drive system (often found near the centre of the wheel line) rotates the clamped-together pipe sections as a single axle, rolling the whole wheel line. Manual adjustment of individual wheel positions may be necessary if the system becomes misaligned.

Wheel line systems are limited in the amount of water they can carry, and limited in the height of crops that can be irrigated. One useful feature of a lateral move system is that it consists of sections that can be easily disconnected, adapting to field shape as the line is moved. They are most often used for small, rectilinear, or oddly-shaped fields, hilly or mountainous regions, or in regions where labor is inexpensive.<ref>{{cite web|last1=Peters|first1=Troy|title=Managing Wheel - Lines and Hand - Lines for High Profitability|url=http://irrigation.wsu.edu/Content/Fact-Sheets/Set-Move-Management.pdf|access-date=29 May 2015|archive-url=https://web.archive.org/web/20161021014252/http://irrigation.wsu.edu/Content/Fact-Sheets/Set-Move-Management.pdf|archive-date=21 October 2016|url-status=dead}}</ref><ref>{{cite web|last1=Hill|first1=Robert|title=Wheelmove Sprinkler Irrigation Operation and Management|url=http://extension.usu.edu/files/publications/publication/ENGR_BIE_WM_08.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://extension.usu.edu/files/publications/publication/ENGR_BIE_WM_08.pdf |archive-date=2022-10-09 |url-status=live|access-date=29 May 2015}}</ref>

==== Lawn sprinkler systems ====
A lawn sprinkler system is permanently installed, as opposed to a hose-end sprinkler, which is portable. Sprinkler systems are installed in residential lawns, in commercial landscapes, for churches and schools, in public parks and cemeteries, and on [[golf course]]s. Most of the components of these irrigation systems are hidden under ground, since aesthetics are important in a landscape. A typical lawn sprinkler system will consist of one or more zones, limited in size by the capacity of the water source. Each zone will cover a designated portion of the landscape. Sections of the landscape will usually be divided by [[microclimate]], type of plant material, and type of irrigation equipment. A landscape irrigation system may also include zones containing drip irrigation, bubblers, or other types of equipment besides sprinklers.

Although manual systems are still used, most lawn sprinkler systems may be operated automatically using an [[Controller (irrigation)|irrigation controller]], sometimes called a clock or timer. Most automatic systems employ electric [[solenoid valve]]s. Each zone has one or more of these valves that are wired to the controller. When the controller sends power to the valve, the valve opens, allowing water to flow to the sprinklers in that zone.

There are two main types of sprinklers used in lawn irrigation, pop-up spray heads and rotors. Spray heads have a fixed spray pattern, while rotors have one or more streams that rotate. Spray heads are used to cover smaller areas, while rotors are used for larger areas. Golf course rotors are sometimes so large that a single sprinkler is combined with a valve and called a 'valve in head'. When used in a turf area, the sprinklers are installed with the top of the head flush with the ground surface. When the system is pressurized, the head will pop up out of the ground and water the desired area until the valve closes and shuts off that zone. Once there is no more pressure in the lateral line, the sprinkler head will retract back into the ground. In flower beds or shrub areas, sprinklers may be mounted on above ground risers or even taller pop-up sprinklers may be used and installed flush as in a lawn area.

==== Hose-end sprinklers ====
[[File:Irrigational sprinkler.jpg|thumb|An [[impact sprinkler]] watering a lawn, an example of a hose-end sprinkler]]
Hose-end sprinklers are devices attached to the end of a garden hose, used for watering lawns, gardens, or plants. They come in a variety of designs and styles, allowing you to adjust the water flow, pattern, and range for efficient irrigation. Some common types of hose-end sprinklers include:

Oscillating Sprinklers: These spray water back and forth in a rectangular or square pattern. They are good for covering large, flat areas evenly.

Impact (or Pulsating) Sprinklers: These create a rotating, pulsating spray, which can cover a circular or semi-circular area. They are useful for watering large lawns.

Stationary Sprinklers: These have a fixed spray pattern and are best for smaller areas or gardens.

Rotary Sprinklers: These use spinning arms to distribute water in a circular or semi-circular pattern.

Traveling Sprinklers: These move along the hose path on their own, watering as they go, ideal for covering long, narrow spaces.

Each type offers different advantages based on garden size and shape, water pressure, and specific watering needs.

=== Subirrigation ===
[[Subirrigation]] has been used for many years in field crops in areas with high [[water table]]s. It is a method of artificially raising the water table to allow the [[soil]] to be [[wikt:moisten|moistened]] from below the plants' [[root]] zone. Often those systems are located on permanent grasslands in lowlands or river valleys and combined with drainage infrastructure. A system of pumping stations, canals, weirs and gates allows it to increase or decrease the water level in a network of ditches and thereby control the water table.

Subirrigation is also used in the [[commerce|commercial]] [[greenhouse]] production, usually for [[potted plant]]s. Water is delivered from below, absorbed by upwards, and the excess collected for recycling. Typically, a solution of water and [[nutrient]]s floods a container or flows through a trough for a short period of time, 10–20 minutes, and is then pumped back into a holding [[Water tank|tank]] for reuse. Sub-irrigation in greenhouses requires fairly sophisticated, expensive equipment and management. Advantages are water and nutrient conservation, and labor savings through reduced system maintenance and [[automation]]. It is similar in principle and action to subsurface basin irrigation.

Another type of subirrigation is the self-watering container, also known as a [[sub-irrigated planter]]. This consists of a planter suspended over a reservoir with some type of wicking material such as a polyester rope. The water is drawn up the wick through capillary action.<ref>{{cite web|url=http://www.entheogen.com/forum/showthread.php?t=13076 |title=Polyester ropes natural irrigation technique |publisher=Entheogen.com |access-date=2012-06-19 |url-status=dead |archive-url=https://web.archive.org/web/20120412031536/http://www.entheogen.com/forum/showthread.php?t=13076 |archive-date=April 12, 2012 }}</ref><ref>{{cite web|url=http://www.instructables.com/id/Self-watering-recycled-plant-pot-for-growing-herbs/ |title=DIY instructions for making self-watering system using ropes |publisher=Instructables.com |date=2008-03-17 |access-date=2012-06-19}}</ref> A similar technique is the [[wicking bed]]; this too uses capillary action.