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大豆需氮的两个关键时期有人认为大豆是豆科作物，其根瘤菌能固氮，不需要施用氮肥。其实，大豆需肥量很大，其需氮量比小麦玉米多１～２倍，根瘤菌从空气中固定的游离氮素仅能供给大豆生育所需氮素的三分之一到二分之一，远远不能满足大豆生长发育的需要，其余还要从土壤...
It is thought that soybeans are leguminous crops at two crucial junctures of nitrogen demand for nitrogen. Rhizobium can fix nitrogen and does not require nitrogen fertilizer. In fact, soybeans need a large amount of fertilizer, which requires 1 to 2 times more nitrogen than wheat and corn. The immobilized free nitrogen from rhizobium can only supply one-third to half of the nitrogen needed for soybean growth First, far from meeting the needs of soybean growth and development, the rest but also from the soil ...