Does extending recycling chain of using rice straw contribute to improving yield and reducing GHGs emissions in paddy field? An integrated analysis based on field research and system assessment

Abstract

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.