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灌溉的目的除了使农作物获得足够消耗的水份,也是为了使植物所需的养料和水相溶解,变成可给状态供植物吸取。灌溉适当还可增进土壤的实效肥沃性,不能看成单纯供给作物所需水量。灌溉的水份过少固然影响作物的生长,水份过多其恶果更为严重。用水过多,长期用大畦漫灌的方法浇水,将使土壤结构破壤,表土板结;土壤中的肥料因用水过多渗透到地下水层而随之流失。无结构的土壤增加了毛细管作用,促使地下水易於上升,增高地下水水位,并将土壤底层的鹽類带到表土上来,
The purpose of irrigation is to obtain sufficient water for the crops, and also to dissolve the nutrients and water needed by the plants, so that they can be used for plant absorption. Appropriate irrigation can also increase the effective fertility of the soil and cannot be regarded as simply the amount of water needed to supply crops. Excessively irrigated water does affect the growth of the crop. Excessive water content is even worse. Excessive use of water, long-term watering with a large flood irrigation method, will make the soil structure destroyed, topsoil compaction; fertilizer in the soil due to excessive penetration into the groundwater layer with the loss. Unstructured soils increase capillary action, promote groundwater prone to rise, increase groundwater levels, and carry salts from the bottom of the soil to the topsoil.