An agricultural drainage system is a system by which water is drained on or in the soil to enhance agricultural production of crops.
It may involve any combination of stormwater control, erosion control, and watertable control.
Field drainage systems are differentiated in surface and subsurface field drainage systems.
Sometimes (e.g., in irrigated, submerged rice fields), a form of temporary drainage is required whereby the drainage system is allowed to function only on certain occasions (e.g., during the harvest period).
The field drains (or laterals) discharge their water into the collector or main system either by gravity or by pumping.
The wells (which may be open dug wells or tubewells) have normally to be pumped, but sometimes they are connected to drains for discharge by gravity.
When the drain discharge takes place entirely by gravity, both types of subsurface systems have much in common, except that the checked systems have control gates that can be opened and closed according to need. A checked drainage system also reduces the discharge through the main drainage system, thereby reducing construction costs.
When the discharge takes place by pumping, the drainage can be checked simply by not operating the pumps or by reducing the pumping time.
They consist of reshaped or reformed land surfaces and can be divided into: The bedded and graded systems may have ridges and furrows.Modern buried pipe drains often consist of corrugated, flexible, and perforated plastic (PE or PVC) pipe lines wrapped with an envelope or filter material to improve the permeability around the pipes and to prevent entry of soil particles, which is especially important in fine sandy and silty soils.The surround may consist of synthetic fibre (geotextile).In northwestern India, this practice has increased the irrigation efficiency and reduced the quantity of irrigation water needed, and has not led to any undue salinization.The subsurface field drainage systems consist of horizontal or slightly sloping channels made in the soil; they can be open ditches, trenches, filled with brushwood and a soil cap, filled with stones and a soil cap, buried pipe drains, tile drains, or mole drains, but they can also consist of a series of wells.