Abstract:

The research on variations of P in paddy fields in riceduck (RD) and ricefish (RF) complex ecosystems and its environmental impact were conducted by field experiments from May to September in 2007.It is found that the P concentrations of soil and floodwater reached peaks immediately after the application of P fertilizer,and then decreased 1 week after fertilization.Compared with CK(coventional rice 〖JP2〗fields),RD and RF could significantly enhance total P concentrations in floodwater,dissolved P concentrations in floodwater,available P concentrations in soil and P uptake by rice plants,and slightly increase total P concentrations in soil.Close relationships were observed between dissolved P concentrations in floodwater,available P concentrations in soil and P uptake by rice plants.The analysis on environmental impacts of floodwater P showed that it was a pivotal time in one week after fertilization to control P losses by leaching from paddy fields.While ducks and fishes were reared,drainage of water from paddy fields and leaching due to runoff should be controlled.Moreover,since RD and RF could enhance contents of soil available nutrient,the consumption of fertilizers may be reduced,leading to the reduced detrimental impact on environment.

Key words: riceduck, ricefish ecosystems, available P, dissolved P, P uptake