Carbon and water footprints of major cereal crops production in China

Greenhouse gas (GHG) emissions and freshwater scarcity are central environmental concerns in China. They are closely linked to crop production. Based on a national-scale survey and statistics, we estimated the carbon footprint (CF) and water footprint (WF) of rice, wheat, and corn in China in 2011. The GHG emissions were 9.9, 3.9, and 3.7 tons of carbon dioxide equivalents per hectare (t CO(2)e ha(-1)) for rice, wheat, and corn, respectively. Carbon sequestration due to straw return mitigated 202-478 kg CO(2)e ha(-1). Therefore, the farm CFs were 9.7, 3.5, and 3.4 t CO(2)e ha(-1) for rice, wheat, and corn; while the product CFs were 1.4, 0.7, and 0.6 kg CO(2)e kg(-1) respectively. The product WFs were 1.5, 1.1, and 1 m(3) kg(-1) for rice, wheat, and corn, respectively. Blue water made a greater contribution to WF in the north and northwest than to the other regions, and gray water occupied 27% of the total WF. Our results indicated that cereal production in China depended more on fertilization and irrigation than global average production requirements. The significantly positive relationships between the CF and WF indicated the possibility for simultaneous mitigation. Based on our results and other studies, we recommended potential practices, especially optimized fertilization and irrigation, and straw returns, to mitigate GHG emissions and water use to achieve environmentally sustainable agriculture in China. (C) 2018 Published by Elsevier Ltd.