A STUDY ON ECOLOGICAL CHARACTERISTICS OF LOCUST NODULATION AND NITROGEN FIXATION
刺槐结瘤固氮生态特性的研究

It is mainly from April to August for the locust Rhizobium to infect the plant. After nodulation the nodules kept on growing fine and had higher N2-fixing activity. Their greater part died in winter. After surviving winter the others grew continuously in next year. The plants picked nodules and the replanted plants got a fast renodulation from April to August and showed high power of revivifying nodule. After August renodulation grew few this year until the next spring.Seasonal variation in the N2-fixation activity was observed. Its recommencement in first ten day of april was associated with leaf expansion. The N2 are activity increaced rapidly and attained a higher level in the summer and autumn period, generally 6-10nmol/g.h, however, it was minimized or entirely stopped throughout winter, from the middle ten days of November to the end of March. The daily variation of the activity in the autumn showed that activity was lower in the morning and bacame higher quick, kept up a higher level in the afternoon and night. Soil conditions apparently influenced nitrogen fixation capacity. It was high on the neutral, weak acid and low calcareous soils, but low on stronghly calcareous and strong acid soils.N2-fixing activty was related obviously with soil moisture content. The nitrogen fixation evidently promoted the plant growth.