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Irrigation is when people add water to plants, to help them grow when there is not enough rain. Irrigation water can be pumped from rivers, natural lakes or lakes created by dams, from wells or allowed to flow to the fields by the force of gravity along pipes or open canals.
Types of Irrigation
Irrigation water can be applied to the plants from above by sprinklers that throw water out under pressure, or from watering cans. In sprinkler irrigation, water is moved through pipes to sprinklers scattered around and within the field. Center pivot irrigation is a type of sprinkler irrigation. In drip irrigation water is brought to the plants via pipes having small holes or special emitters spaced along the pipe.
Surface methods allow water to flow onto the soil surface from canals or pipes. Traditional methods allow water to flow over the entire surface of the field but drip irrigation allows water to be directed to the roots of each plant and much less water is lost by soaking into the ground.
Sub-surface irrigation raises the water table so that it can be accessed by the roots of the crop and less water is dried up by the air.
Irrigation can let more crops be grown on the same land, or allow a crop to grow in a dry period. It is expensive and care should be taken to ensure that the benefits from increased crop yields are not exceeded by the installation and operating costs of the irrigation scheme.
Irrigation causes a subsequent rise in watertables. If saline water is below, it may rise to the surface. Sometimes salinity becomes high enough to kill the plants. Irrigation water itself can carry salt and sometimes other toxic materials that hurt the plants. To prevent this, irrigation projects must also assure good drainage.