大豆的氮素营养来源主要是根瘤菌共生固定大气中的氮和土壤供氮(包括施氮肥)。然而大豆播种后的一个月内共生固氮量甚微,且我国不少地区农田土壤缺氮。在缺氮的土壤条件下,如果早期不施氮肥,往往出现大豆氮素饥饿,营养生长势弱,并导致整个生育期间植株矮小,叶片发黄,光合作用效率不高,产量很低。配合其它肥料施用适量 The main source of nitrogen nutrition of soybean rhizobium symbiotic fixed atmospheric nitrogen and soil nitrogen (including nitrogen fertilizer). However, within a month after sowing, the amount of symbiotic nitrogen fixation is very small, and nitrogen deficiency in farmland in many parts of China. Under nitrogen-deficient soil conditions, nitrogen starvation was often observed in soybean without nitrogen fertilizer in the early stage, and vegetative growth tended to weaken. During the whole growth period, the plants were shortened, the leaves were yellow, the photosynthesis was not efficient, and the yield was very low. With other fertilizers appropriate amount