Effects of nitrogen levels on nodule growth of soybean using 15N tracing method

In order to definite the effects of soybean nodules growth, 15N tracing and sand culture were used to study the effects of nitrogen nutrition levels on nodule growth and nodule nitrogen fixation of soybean cultivar, DN 47. The results show that the dry weights of nodules are increased earlier and decreased later when the exogenous-N levels are gradually increased, and the dry weight of nodules is maximum when the nitrogen concentration is 50 mg/L. Nodules growth needs startup-N, and the best effect of the startup-N on nodule growth is before the V3 period. Growth of nodules is inhibited while applying exogenous-N during the R4-R5. There are significant correlations between dry weight of nodules, N-accumulation of nodules, N ratio in nodules and N-accumulation in plants.