About 68% of this area is in Asia, 17% in the Americas, 9% in Europe, 5% in Africa and 1% in Oceania. In 2000, the total fertile land was 2,788,000 km 2 (689 million acres) and it was equipped with irrigation infrastructure worldwide. Over-irrigation can cause deep drainage from rising water tables that can lead to problems of irrigation salinity requiring watertable control by some form of subsurface land drainage.Įxtent Share of agricultural land which is irrigated (2015) Soil can be over-irrigated due to poor distribution uniformity or management wastes water, chemicals, and may lead to water pollution. Amongst some of these problems is depletion of underground aquifers through overdrafting. The effects stem from the altered hydrological conditions caused by the installation and operation of the irrigation scheme. 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 basins and downstream of an irrigation scheme. 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. Irrigation can be supplementary to rainfall, 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. Irrigation water can come from groundwater (extracted from springs or by using wells), from surface water (withdrawn from rivers, lakes or reservoirs) or from non-conventional sources like treated wastewater, desalinated water, drainage water, or fog collection. It involves artificially raising the water table to moisten the soil below the root zone of plants. Subirrigation has been used in field crops in areas with high water tables for many years. Drip irrigation delivers water directly to the root zone of plants. Micro-irrigation uses less pressure and water flow than sprinkler irrigation. 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. In sprinkler irrigation, water is piped to one or more central locations within the field and distributed by overhead high-pressure water devices. Surface irrigation, also known as gravity irrigation, is the oldest form of irrigation and has been in use for thousands of years. There are several methods of irrigation that differ in how water is supplied to plants. Drainage, which involves the removal of surface and sub-surface water from a given location, is often studied in conjunction with irrigation. It is also used to cool livestock, reduce dust, dispose of sewage, and support mining operations. In addition to these uses, irrigation is also employed to protect crops from frost, suppress weed growth in grain fields, and prevent soil consolidation. Irrigation helps to grow crops, maintain landscapes, and revegetate disturbed soils in dry areas and during times of below-average rainfall. Irrigation has been a key aspect of agriculture for over 5,000 years and has been developed by many cultures around the world. Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation of agricultural fields in Andalusia, Spain.
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