豆科绿肥为什么是一种最优良的绿肥呢?这由于根瘤菌能在它的根上形成根瘤,进行共生固氮作用,把空气中的游离氮固定下来变为化合态氮,提高了植物体内的含氮量,积累和丰富了土壤中的氮素。当根瘤菌与豆科植物达到高度共生关系时,它们的固氮量是很可观的。根据国外许多资料估计,豆科植物体内的全部氮素,约有 Why legume green manure is one of the best green manure it? This because rhizobia can form nodules in its roots, symbiotic nitrogen fixation, the free nitrogen in the air fixed into the compound nitrogen, increased plant body containing Nitrogen content, accumulation and enrichment of nitrogen in soil. When rhizobia and legumes achieve a high degree of symbiotic relationship, their nitrogen fixation is very substantial. According to many foreign estimates, all the legume nitrogen, about