Abstract: To understand the operation mechanism of the rice and fishery complex system in the saline land,the water,soil,and rice crabs in the paddy fields,ring ditch,and main ditch of the system were sampled from April to September 2021 to determine the contents of nitrogen,phosphorus,and potassium,and the interception rate and material flow analysis methods were applied to study the accumulation characteristics and transport of nutrients in the rice and fishery complex system. The results showed that the system effectively intercepted nutrients,among which the soil accumulation capacity of the system was weak and released some nutrients,and the cumulative effect of soil nutrients showed rice field > main ditch > ring ditch;the material flow analysis showed that the nutrients of the system had a relatively good out-in ratio and output-input ratio,with total nitrogen being used mainly by rice crabs,and the system had a high surplus of total phosphorus and total potassium. It could be seen that the system intercepted nutrients effectively, the rice crabs were able to use the nutrients,especially the ability to use total nitrogen,and total potassium was also stored in the soil; the system effectively purified the water body,and the input nutrients could meet the growth demand of rice crabs and other organisms.

Key words: rice and fishery, complex system, nutrients, accumulation characteristics, transport