Changes in paddy cropping system enhanced economic profit and ecological sustainability in central China

In China,the traditional early and late season double rice(DR)system is declining accompanied by the fast increase of two newly developed cropping systems:ratoon rice(RR)and rice-crawfish(RC).Three methodologies:economic analysis,emergy evaluation and life cycle assessment(LCA)were employed to evaluate the economics and sustainability of this paddy cropping system change.Economic analysis indicated that the income and profit of the RC system were far larger than those of RR and DR.The income to costs ratio of RR and RC increased by 25.5 and 122.7%compared with that of DR,respectively.RC had the highest emergy input thanks to increasing irrigation water,electricity,juvenile crawfish and forage input while RR showed a lower total emergy and nonrenewable emergy input,such as irrigation water,electricity,fertilizers and pesticides than DR.The environmental loading ratios decreased by 16.7-50.4%when cropping system changed from DR to RR or from DR to RC while the emergy sustainability indexes increased by 22.6-112.9%.The life cycle assessment indicated lower potential environmental impacts of RR and RC,whose total environmental impact indexes were 35.0-61.0%lower than that of DR.Grain yield of RR was comparable with that of DR in spite of less financial and emergy input of RR,but RC had a much lower grain yield(a 53.6%reduction compared to DR).These results suggested that RR is a suitable cropping system to achieve the food security,economic and environmental goals.