Employing emergy value evaluation method,this paper compared the ecological and economic benefits of rice-duck
organic farming
system (modeⅠ) and conventional rice-wheat rotation system (modeⅡ) in Shanghai suburb.The results showed that modeⅠhad better emergy benefits,higher self-organizing ability and sustainability,and higher product safety.The net emergy yield ratio (EYR),feedback ratio of yield emergy (FYE ),and emergy sustainable index (ESI) of modeⅠwere
respectively 1.57,14.1,and 8.71 times as much as those of modeⅡ,and the emergy index of product safety (EIPS) was 0 in modeⅠbut-0.66 in modeⅡ.The emergy investment ratio (EIR) and environmental loading ratio (ELR) of modeⅠwere 40.1% and 18.3% of modeⅡ,respectively,suggesting that modeⅠhad less environmental pressure than modeⅡ.ModeⅠhad lower economic benefits than modeⅡ.The economic output,gross income,and net income of modeⅠwere 15.7%,9.6%,and 29.6% less than those of modeⅡ,respectively.As for Em$,the output,gross income,and net income of modeⅠwere respectively 50%,102.6%,and 136.4% higher than those of modeⅡ.With the system optimization and the development of organic food market,modeⅠhad the potential to improve its economic benefits.