Emergy-based benefit analysis of integrated rice-frog farming

Integrated rice-frog farming (IRFF) is an ecological farming method that can improve production efficiency and promote sustainable development in agriculture. However, few studies have analyzed the benefits of IRFF. This study performed an emergy analysis to evaluate the IRFF system energy input and output in the Qingpu District, Shanghai, China, from 2015 to 2019 and calculated the self-sufficiency, emergy investment ratio, emergy yield ratio, the environmental loading ratio, and the sustainable development index. The results showed that irrigation water, rainfall chemical energy, compound fertilizer, organic fertilizer, and infrastructure were the primary IRFF system energy inputs; rice, straw, frogs, and policy income were the primary energy outputs. The average emergy self-sufficiency and investment ratios from 2015 to 2019 were 0.18 and 4.86, respectively, with no significant changes over the five years. The average emergy yield ratio was 3.65, which generally increased annually. The average environmental loading ratio was 0.46, trending downwards, and the average sustainable development index was 8.52, trending upwards. Compared with similar farming systems, the IRFF system emergy indices performed better because of the differences in study areas and management modes. In the IRFF system, the natural resource input was less, and the purchasing emergy input and output efficiency were higher than in other systems. These results indicated that the IRFF system had a low dependence on natural resources and placed minimal pressure on the environmental system. The IRFF system had great potential for sustainable development and ecological production, but the results showed that the IRFF system was weak in self-sustainment and fluctuated greatly under the influence of economy and society. The energy value investment and net energy value output rates were also low, and the use of resources was insufficient, but there was development potential. Therefore, to further develop the IRFF system in the Qingpu District, more input emergy should be invested, and diversified commodities should be developed to improve the total output efficiency.