Irrigation

The irrigation is the operation consisting in artificially bringing Eau to cultivated Végétaux to increase the production, and to allow by it their normal development in the event of water deficit induced by a pluviometric deficit , an excessive drainage or a fall of tablecloth, in particular in the arid regions.

The irrigation can also have other applications:

  • the contribution of fertilizing elements either on the ground, or, by sprinkling, with the sheets (foliar Fertilization); in the hydroponic culture, the irrigation merges completely with the fertilization;
  • the fight against the Freezing, by water sprinkling on the foliage (Orchard S, vineyards) can make it possible to gain a few degrees of invaluable temperature at the time of the late frosts, even in certain cases by flood.

Generally one speaks about “Arrosage” for small surfaces (Jardinage) holding the term of “irrigation” for more important surfaces (Agriculture of full field, Horticulture), but there is no standard on the matter.

According to the international glossary of hydrology, the irrigation it is an artificial water contribution on grounds at agricultural ends.

Techniques of irrigation

One can distinguish several techniques from irrigation:
  • manual (watering-can, bucket…), reserved on the very small surfaces;
  • by flow of surface, under the simple effect of gravity, by means of channels and drains;
  • by sprinkling, technique which consists in reproducing the rain;
  • by Microphone-irrigation or drop by drop, which is a sparing water technique, and which makes it possible to avoid the streaming;
  • by infiltration, by means of buried porous pipes, alternative of the technique of drop by drop;
  • by flood or immersion (it is the technique applied in the Rizière S).

Determination of the requirements out of water

The requirements out of water for the plants depend on several factors, intrinsic or extrinsic with the culture: nature of the crop plants (species, variety), stage of vegetation, nature and state of moisture of the ground, data climatic (precipitations, insolation, wind…).

It is advisable to take account of the water reserves of the ground, of the evaporation on the level of the ground, of the Transpiration of the plants, the evapotranspiration which cumulates the two phenomena.

Material of irrigation

One can distinguish two categories of materials or installations necessary to the irrigation:
  • those being used to bring water since the sources available (River, Lake S or retained, Ground water);
  • those being used for the irrigation itself, i.e. to distribute water to the plants.

In the first category, one will find: drilling, Pump S, networks of irrigations, channels, Noria S…

In the second: asperseurs, rain guns, sprinklers motorized, goutteurs. There exists for example a system of Irrigation to central pivot.

Interest and limits of the irrigation

In the world, 277 million hectares is irrigated (year 2002, source FAO) on 1,4 billion hectares of arable lands on the whole. They provide approximately 1/3 of the world food production.

Three countries (India, China, the United States) account for 50% of total irrigated surfaces. 80% of the food produced with the Pakistan come from irrigated grounds, 70% for China, but less than 2% for the Ghana, the Mozambique or the Malawi.

In France agriculture, as in the rest of the world, is the first activity consuming water (more than 50% of consumed volumes and up to 80% in summer). In 2000, 1,9 million arable hectares of lands was irrigated, with annual variations explained by meteorology. in 1970 this surface was of 0,8 million in 1970. 5,7% of the agricultural surface used (SAU) are irrigated (of which the Maïs represents about half). The areas irrigating more are the Aquitaine, the valley of the the Rhone, the Beauce, the Pays of the Loire and the Poitou-Charentes. The rate of equipment of irrigation (or surfaces irrigable) seems to be stabilized to 2,7 million ha equipped. Agricultural regional specializations lead so that 3 areas (Aquitaine, Center and the Midday-Pyrenees) concentrate 50% of irrigated surfaces. In 2006 nearly 90% of the exploitations had a volumetric water meter (but they were only half in 2000). Part of the irrigation is not déclarée. Le Monde of August 9th, 2005

Source: 2005, national Strategic planning of the Ministry for agriculture , which is the strategic directions that each Member State of the EU must finalize within the framework of the installation of the future FEADER (the second pillar of the CAP).

The need for preserving the water resources brings more and more to a regulation and the tax on the taking away.

An unsuited or badly conceived irrigation can cause , diffusion of organizations Pathogène S (Pseudomonas by ex) Polluant S in the culture, or arid region, phenomenon of Salinisation.

The irrigation can also affect the ecosystem S, the landscape or agriculture upstream or downstream, because of diverted volumes of water of the rivers. One often quotes the example of the Mer of Aral polluted and partly emptied because of the irrigation of cotton upstream.

Also let us note that the irrigation constitutes an insurance of income for the farmers, in particular for special cultures (fruits, vegetables…), and that it represents a large constraint in the process of production. In France, irrigated agriculture employs between 2 and 5 times more people with the hectare than rain agriculture, it generate an equivalent number of employment upstream and downstream.

See too

  • One also speaks about irrigation in connection with the circulation of the Sang in the bodies of the Human body or in the animals.

External bonds

  • Graph, Surfaces irrigated in the world (UNO, report/ratio GEO3)
  • Memorandum on the irrigation of the cultures - Document to the format pdf,
  • Reverdir the desert, contains a passage on the irrigation drip.

Simple: Irrigation

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