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An agricultural drainage system is a system by which the water level on or in the soil is controlled to enhance agricultural crop production. ==Classification== Agriculture drainage is mainly of two types.. (1). Surface drainage (2). Sub Surface Drainage. However there are some other drainage systems also. Figure 1 classifies the various types of drainage systems. It shows the field (or internal) and the main (or external) systems.〔''Agricultural Drainage Criteria''. Chapter 17 in: H.P.Ritzema (ed. 1994), Drainage Principles and Applications, ILRI Publication 16, p.635-690. International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands. ISBN 90-70754-33-9. Free download from : () , under nr. 1, or directly as PDF : ()〕 The function of the field drainage system is to control the water table, whereas the function of the main drainage system is to collect, transport, and dispose of the water through an outfall or outlet. In some instances one makes an additional distinction between collector and main drainage systems. 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 on certain occasions only (e.g. during the harvest period). If allowed to function continuously, excessive quantities of water would be lost. Such a system is therefore called a checked, or controlled, drainage system. More usually, however, the drainage system is meant to function as regularly as possible to prevent undue waterlogging at any time and one employs a regular drainage system. In literature, this is sometimes also called a "relief drainage system". 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Drainage system (agriculture)」の詳細全文を読む スポンサード リンク
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