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Irrigation schemes in the world use about 3 500 km 3 water per year, of which 74% is evaporated by the crops. [7] This is some 80% of all water used by mankind (4 400 km 3 per year). The water used for irrigation is roughly 25% of the annually available water resources (14 000 km 3 ) and 9% of all annual river discharges in the hydrological cycle .
Inf = Irr + Wel, where Irr = surface irrigation from the canal system, and Wel = the irrigation from wells; The field irrigation efficiency (Ff < 1) is: Ff = Era / Inf, where Era = the evapotranspiration of the crop (consumptive use) The value of Era is less than Inf, there is an excess of irrigation that percolates down to the subsoil (Per):
A satellite image of circular fields characteristic of center pivot irrigation, Kansas Farmland with circular pivot irrigation. Center-pivot irrigation (sometimes called central pivot irrigation), also called water-wheel and circle irrigation, is a method of crop irrigation in which equipment rotates around a pivot and crops are watered with sprinklers.
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 ...
With modern advancements, crops are being cultivated year round in countries all around the world. [citation needed] As water usage becomes a more pervasive global issue, irrigation practices for crops are being refined and becoming more sustainable. While several irrigation systems are used, these may be grouped into two types: high flow and ...
However, there is some question as to the benefit of increased water-use efficiency of plants in agricultural systems, as the processes of increased yield production and decreased water loss due to transpiration (that is, the main driver of increases in water-use efficiency) are fundamentally opposed.
Irrigation is the artificial exploitation and distribution of water at project level aiming at application of water at field level to agricultural crops [1] in dry areas or in periods of scarce rainfall to assure or improve crop production.
In agriculture, leaching is the loss of water-soluble plant nutrients from the soil, due to rain and irrigation. Soil structure, crop planting, type and application rates of fertilizers, and other factors are taken into account to avoid excessive nutrient loss.