Abstract:

In order to evaluate the growth, nodulation and N-fixation of Sesbania rostrata-Azorhizobium caulinodans symbiosis on different water and N fertilizer conditions, a greenhouse experiment in Guangzhou was conducted in summer. Pots were filled with 1 kg homogenized, dried loam red soil. NH4NO3 was applied to obtain concentrations of 10, 20, 40 mg N·kg-1 in the soil. According to water supply to the experimental soil, the pots were divided into three groups as below: W1－no waterlogging, W2－shallowly waterlogged (soil water in field capacity) and W3－flooded. The results showed that the growth and nodulation of the symbiosis were greatly influenced by water supply. Though flooding depressed root nodulation, it, however, stimulated stem nodulation and roots growth. S. rostrata grew and nodulated best, and got the maximum N accumulation under the condition of field water capacity. The effect of mineral N on the symbiosis was affected by water supply. In the range of the applied N concentrations in the experiment, both nodulation and N accumulation showed no negative reaction to mineral N, such a result implied that S. rostrata-A. caulinodans symbiosis was quite different to ordinary leguminous root nodule N-fixation symbiosis in the aspect of mineral N reaction.