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To facilitate crop growth excess water should be drained from the rooting zone to allow root development of the crop and from the soil surface to facilitate access to the field. Basically, there are three drainage methods from which the designer can select being; surface drains, pumped tube wells and horizontal pipe drains. The selection between these techniques is not very straightforward and depends to a certain extend on the preferences of the designer. Yet, guidance is given in this paper on the basis of a set of questions that are grouped in a flowchart. Although the flowchart suggests sharp choices between alternative drainage methods, in reality the choice between the recommended methods overlaps. Partly this is because the values in the selection criteria (questions) are indicative. Further overlap is caused by the construction and operation and maintenance cost of the drainage system under local conditions. These costs are not included in the flowchart. |
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