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Excess water in the crop root zone soil is injurious to plant growth. Artificial drainage is essential on poorly drained agricultural fields to provide optimum air and salt environments in the root zone. Crop yields are drastically reduced on poorly drained soils, and, in cases of prolonged waterlogging, plants eventually die due to a lack of oxygen in the root zone.Waterlogging in irrigated regions may result in excess soil salinity, i.e., the accumulation of salts in the plant root zone.


Sources of excess soil water that result in high water tables include: high precipitation in humid regions; surplus irrigation water and canal seepage in the irrigated lands; and artesian pressure.Agricultural drainage is the removal of excess water from the soil surface and/or soil profile of cropland, by either gravity or artificial means. In some soils, the natural drainage processes are sufficient for growth and production of agricultural crops, but in many other soils, artificial drainage is needed for efficient agricultural production.


Agricultural drainage improvement can help reduce the year-to-year variability in crop yield, which helps reduce the risks associated with the production of abundant, high quality, affordable food. Improved access of farm equipment to the field provides more time for field activities, can help extend the crop production season, and helps reduce crop damage at harvest.


Agricultural drainage conditions around the world can be grouped according to three agro-climatic zones: the temperate zone, the arid and semi-arid zone and the humid and sub-humid zone.


In the temperate agro-climatic zone the major role of drainage is to prevent waterlogging, i.e., excess water in the root zone of crops from surplus rainfall. It also serves the purpose of improving the traffic ability of the farms for farm machinery etc. The field drainage system is generally sub-surface.


In arid and semi-arid zone the function of drainage is to prevent irrigation induced waterlogging and salinization of soils. These zones suffer from population pressure and intensive agriculture through irrigation is resorted to which makes drainage provision essential to maintain the sustainability of agricultural lands.


In humid and semi-humid regions the role of drainage is a combination of waterlogging control, salinization prevention and flood protection. Generally open drainage systems are applied as the rainfall intensities are so high that the sub-surface drainage becomes insufficient or exorbitantly inexpensive.