Monday, November 2, 2009


Land can be improved by regulating the water supply: the soil aeration can be improved, bacterial activity stimu­lated, crop yields improved. Further, irrigation and draining can bring marginal lands, such as deserts and swamps, into agricultural use.

IRRIGATION If natural precipitation cannot meet the moisture requirements of plants, an artificial supply of water becomes necessary. This is irrigation. Irrigation has certain advantages: (i) regular and reliable supply of water; (ii) supply of silt if irrigation is from river waters; (iii) year­round cultivation; (iv) reduction of soil salinity in .deserts (but if water is allowed to evaporate from the fields, salinity will increase).

Types of Irrigation Lifting devices include wells, water wheels and, now, pumps. Basin irrigation involves letting flood water collect in basin-like fields on either side of the river. It was an ancient practice in Egypt. In USA, it is practised on canal water to grow paddy. Tanks are small reservoirs storing rain water. Canals can lead water from rivers or storage lakes to agricultural lands, and form an important feature of irrigated lands. Inundation canals lead water from rivers at times of flood, while perennial canals are fed by large dams or barrages and supply water all round the year. Overhead irrigation is a modern practice involving the use of sprays and sprinklers (common in Europe and USA).

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