Fig. 3From: Greenhouse gas emissions from synthetic nitrogen manufacture and fertilization for main upland crops in ChinaEstimated average annual direct N2O emissions from synthetic N fertilization for wheat and maize in different agricultural regions of China (2015–2017). Error bars in the figure represent standard deviation. NEC Northeast China, NC North China, MLYR Middle and lower reaches of Yangtze River, NWC Northwest China, SSWC South and Southwest ChinaBack to article page