Effects of warming and elevated O3 concentrations on N2O emission and soil nitrification and denitrification rates in a wheat-soybean rotation cropland

The effects of warming and elevated ozone (O-3) concentrations on nitrous oxide (N2O) emission from cropland has received increasing attention; however, the small number of studies on this topic impedes understanding. A field experiment was performed to explore the role of warming and elevated O-3 concentrations on N2O emission from wheat-soybean rotation cropland from 2012 to 2013 using opentop chambers (OTCs). Experimental treatments included ambient temperature (control), elevated temperature (+2 C), elevated O-3 (100 ppb), and combined elevated temperature (+2 C) and 03 (100 ppb). Results demonstrate that warming significantly increased the accumulative amount of N2O (MN) emitted from the soil-winter wheat system due to enhanced nitrification rates in the wheat farmland and nitrate reductase activity in wheat leaves. However, elevated 03 concentrations significantly decreased MN emission from the soil -soybean system owing to reduced nitrification rates in the soybean farmland. The combined treatment of warming and elevated 03 inhibited the emission of N2O from the soybean farmland. Additionally, both the warming and combined treatments significantly increased soil nitrification rates in winter wheat and soybean croplands and decreased denitrification rates in the winter wheat cropping system. Our results suggest that global warming and elevated O-3 concentrations will strongly affect N2O emission from wheat-soybean rotation croplands. (C) 2019 Elsevier Ltd. All rights reserved.