Editing Irrigation (section)

{{Short description|Agricultural artificial application of water to land}}
{{about|irrigation for agriculture and landscapes||}}
{{Redirect|Watering|the river in Germany|Wätering}}
{{Use mdy dates|date=December 2022}}[[File:Fields SW from Sevilla.jpg|thumb|Irrigation of agricultural fields in [[Andalusia]], Spain. Irrigation canal on the left.]]
'''Irrigation''' (also referred to as '''watering''' '''of plants''') is the practice of applying controlled amounts of [[water]] to [[land]] to help grow [[crop]]s, [[landscape plant]]s, and [[lawn]]s. Irrigation has been a key aspect of [[agriculture]] for over 5,000 years and has been developed by many cultures around the world. Irrigation helps to grow crops, maintain landscapes, and [[revegetation|revegetate]] disturbed soils in dry areas and during times of below-average rainfall. In addition to these uses, irrigation is also employed to protect crops from [[frost]],<ref>{{cite book |last1=Snyder |first1=R. L. |url=http://www.fao.org/docrep/008/y7223e/y7223e00.htm |title=Frost protection: fundamentals, practice, and economics |last2=Melo-Abreu |first2=J. P. |publisher=Food and Agriculture Organization of the United Nations |year=2005 |isbn=978-92-5-105328-7 |volume=1 |issn=1684-8241}}</ref> suppress [[weed]] growth in [[grain]] fields, and prevent [[soil consolidation]]. It is also used to cool [[livestock]], reduce [[dust]], dispose of [[sewage]], and support [[mining]] operations. [[Drainage]], which involves the removal of surface and sub-surface water from a given location, is often studied in conjunction with irrigation.

There are several methods of irrigation that differ in how water is supplied to plants. [[Surface irrigation]], also known as gravity irrigation, is the oldest form of irrigation and has been in use for thousands of years. In [[Irrigation sprinkler|sprinkler irrigation]], water is piped to one or more central locations within the field and distributed by overhead high-pressure water devices. [[Micro-irrigation]] is a system that distributes water under low pressure through a piped network and applies it as a small discharge to each plant. Micro-irrigation uses less pressure and water flow than sprinkler irrigation. [[Drip irrigation]] delivers water directly to the root zone of plants. [[Subirrigation]] has been used in field crops in areas with high water tables for many years. It involves artificially raising the water table to moisten the soil below the root zone of plants.

Irrigation water can come from [[groundwater]] (extracted from [[Spring (hydrosphere)|springs]] or by using [[Water well|wells]]), from surface water (withdrawn from [[river]]s, [[lake]]s or [[reservoirs]]) or from non-conventional sources like [[reclaimed water|treated wastewater]], [[desalinated water]], [[drainage|drainage water]], or [[fog collection]]. Irrigation can be supplementary to [[rain]]fall, which is common in many parts of the world as [[rainfed agriculture]], or it can be full irrigation, where crops rarely rely on any contribution from rainfall. Full irrigation is less common and only occurs in arid landscapes with very low rainfall or when crops are grown in semi-arid areas outside of rainy seasons.

The environmental effects of irrigation relate to the changes in quantity and quality of [[soil]] and [[water]] as a result of irrigation and the subsequent effects on natural and social conditions in [[river basin]]s and downstream of an [[irrigation scheme]]. The effects stem from the altered [[Hydrology|hydrological conditions]] caused by the installation and operation of the irrigation scheme. Amongst some of these problems is depletion of underground [[aquifers]] through [[overdrafting]]. Soil can be over-irrigated due to poor [[distribution uniformity]] or [[Irrigation scheduling|management]] [[waste]]s water, chemicals, and may lead to [[water pollution]]. Over-irrigation can cause deep drainage from rising water tables that can lead to problems of irrigation [[Soil salinity|salinity]] requiring [[watertable control]] by some form of [[Drainage system (agriculture)|subsurface land drainage]].
{{TOC limit|3}}