相当一段时间以来人们就已知道土壤中一部分氮系以固定态铵态存在,但一般认为,这部分氮难于为作物所利用,因而它较少受到注意。近年来,Kowalenko等和Mengel等指出’固定态铵处于不断的变动中,部分可为作物吸收利用,它是作物的氮素来源之一,是土壤氮 It has been known for quite some time that a part of the nitrogen in the soil is in the form of a fixed ammonium, but it is generally considered that this part of nitrogen is hard to be utilized by the crop and thus it is less noticed. In recent years, Kowalenko et al. And Mengel et al. Pointed out that ’fixed ammonium is in constant flux and can be partly absorbed by crops. It is one of the nitrogen sources of crop and is soil nitrogen