Bio-straw resource recycling systems: Agricultural productivity and green development

Abstract

Bio-straw is one of the valuable and renewable organic resources. China produces most of the world's bio-straw. Straw recycling is closely associated with global carbon and nitrogen cycles, agricultural productivity, and green development. We systematically integrated straw recycling systems from 1979 to 2019 into three major cereal crops to identify patterns of crop productivity and greenhouse gas (GHG) emissions in a life cycle assessment, and to explore GHG mitigation potential using scenario analyses. Straw recycling partially alleviated the negative potassium surplus caused by straw removal and increased wheat, maize, and rice yields by 7.8%, 5.2%, and 5.0%, respectively. We developed a new empirical model for nitrous oxide (N2O) and methane (CH4) emissions from straw recycling systems in regional crops. Straw recycling promoted direct N2O emissions from upland crops, especially maize. Nonetheless, straw recycling reduced net GHG emissions by 33.1% in wheat and 12.1% in maize due to high rates of soil carbon sequestration relative to inorganic fertilizer management alone. In rice, straw recycling depressed N2O emissions but increased net GHG emissions by 59.8% because CH4 emissions were 2.06 times greater than those under fertilizer management. When combined with optimal fertilizer inputs based on zero nutrient surplus, 100% straw recycling further reduced net GHG emissions by 28.0% in wheat and 19.5% in maize, whereas 60% straw recycling produced better results in rice (20.6% emissions reduction), in spite of increasing fertilizer-induced emissions. Enhancing the quantity and quality of straw recycling, based on crop-specific recycling targets, should contribute to the dual targets of achieving higher crop yields and green development.