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普遍认为与雨水补给的农业比较,灌溉农业可导致谷物产量增加6倍,块根作物产量增加4倍。当肥沃的土地变得越来越少,灌溉可使目前的地里获得较高的产量,对于新的耕作区实质上就是拿水来换取粮食。1974年在罗马举行的世界粮食会议发表的资料数据表明世界上灌溉面积超过了2亿公顷。新的灌溉工程在今后十年内应给增加的2 300万公顷田地供水。
It is generally agreed that irrigated agriculture can result in a sixfold increase in cereal production and a fourfold increase in root crop production compared to rainfed agriculture. When the fertile land becomes less and less, irrigation can make the current crop more productive, and in the new farming area essentially water is used in exchange for food. Data published at the World Food Conference in Rome in 1974 show that the world’s irrigated area exceeds 200 million hectares. The new irrigation project should supply an additional 23 million hectares of land in the next ten years.