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The rapid growth of grain yield in China accelerates a discussion on whether the grain system in China is sustainable. To answer the question, a comprehensive assessment from economic and environmental points is necessary. This study jointly used economic analysis (ECA), emergy evaluation (EME) and carbon footprint (CF) to analyze the environmental and economic sustainability of the grain production system in China based on the national statistical data during 2000–2015. Results showed that the costs of maize, wheat, rice and soybean had increased by 252–346% from 2000 to 2015, causing the lower profit of grain system in recent years. The situation resulted in a serious problem on economic sustainability of grain system in China. Meanwhile, the emergy sustainability index (ESI) of maize, wheat, rice and soybean systems were increasing during 2000–2015, and the CF on unit yield of the crops had been reduced by 10–30% in the study period. The results reflected the improved environmental sustainability of grain system in China during 2000–2015. Nevertheless, the emergy flow of industrial inputs for the crops were increased by 4–22% in the study period, and the CF from the inputs presented a growth rate of 16–23% as well during the same period. The results implied that the grain system in China was relying more on fossil-based inputs. Finally, according to the key points of cost, emergy and CF, we suggest that improving labor efficiency, advanced agricultural practices and optimizing cropping pattern will be effective ways to further improve the economic and environmental sustainability of grain system in China.

Recycling agriculture is an effective way to reduce greenhouse gases (GHGs) emissions and improve yield of agricultural systems. The core practice of the recycling agriculture model is to extend the industrial chain of agricultural activities and to return the wasted organic materials that resulted from each step of the recycling chain into farmland for completely treating them. In this context, people is asking a question about if the longer recycling chain means the better effectives on yield growth and agricultural GHGs mitigation. For answering the question, therefore, this study compared the yield and net GHGs emissions by applying mineral fertilizer (CK), rice straw (CS), cow manure (CM), biogas residue (BR) and commercial organic fertilizer (MO) into paddy field during 2017–2018 in the South China. All of the organic materials were derived from the different steps of recycling chain of rice straw. The results indicated that the yields of CS, CM, BR and MO were 9.4%, 12.7%, 19.7% and 14.2% higher than CK, respectively. The field-based net GHGs emissions (NGHGD) of CS, CM, BR and MO were 7.2%, 9.7%, 24.1% and 66.4% lower than the CK, respectively. The results demonstrated that, from the farmland level, extending recycling chain of using rice straw indeed contributed to improving yield and reducing GHGs emissions in paddy field. Nevertheless, if the NGHG accounting of different treatments considered the upstream GHGs emissions under the condition of ignoring substituted effects, the longer recycling chain of using rice straw did not contribute to reducing the NGHG of the whole recycling agriculture pathways. Specifically, the system-based net GHGs emission (NGHG) of CS was decreased by 13.0% compared to the CK, while the indices of CM, BR and MO were increased by 96.0%, 14.7% and 26.6%, respectively. The information will contribute to the development of circular economy and clean production in agricultural systems.