Evaluation on environmental consequences and sustainability of three rice-based rotation systems in Quanjiao, China by an integrated analysis of life cycle, emergy and economic assessment

The rice-based cultivation system in the middle and lower reaches of the Yangtze River of China is changing gradually during recent years which arouses more attentions and concerns on environmental performance and sustainability. In this study, the integrated analysis of life cycle assessment (LCA), emergy evaluation (EME) and economic analysis (ECA) were applied and Quanjiao county was selected as a case study to estimate the pollution emissions, emergy efficiency and economic benefits of three typical rice-based rotation systems depended on a detailed farming practice filed investigation of 157 valid samples under structured questionnaire. The three typical rice-based rotation systems are rice-wheat rotation (RW), rice-fallow rotation (RF) and rice-crayfish rotation (RC), respectively. The LCA results showed that the area-based potential environmental impact for RW, RF and RC are 34.08, 13.71 and 39.98, the profit-based potential environmental impacts are 2.62, 1.16 and 1.98. The EME results indicated that the RC shows the highest emergy input, around 1.23E+17 sej/ha/yr, more than that of RW and RF, around 3.88E+16 sej/ha/yr and 3.40E+16 sej/ha/yr, respectively. From the emergy indices of the three systems, the RC results in higher environmental pressure and lower sustainability compared with the RW and RF. Fertilizer, diesel oil, water, electricity and forage are the crucial factors of environmental consequences, herein forage, water and electricity inputs are becoming new factors that are increasingly prominent and often neglected. From an economic perspective, the cost and income of the RC are highest because of more input and higher sale value, the area-based profit of the RC (20142 ¥/ha) is higher than that of RF (11848 ¥/ha) and RW (13031 ¥/ha). Generally, during the rice planting system transferring, the development of farming technologies and standards should be promoted to avoid the disorder of agricultural production, and then gearing up to the better economic performance and environmental sustainability for the rice-based rotation systems. Moreover, proper agricultural development policies should be made and promoted to stimulate farmers’ willingness to adopt advanced farming practices and techniques to reduce environmental emissions and enhance agricultural system sustainability as well as increasing farmers' income.