Effects of Enhanced UV-B Radiation on N2O Emission in a Soil-Winter Wheat System

An outdoor pot experiments was conducted to investigate the effects of enhanced ultraviolet-B (UV-B) radiation on nitrous oxide (N2O) emissions from soil-winter wheat systems. The enhanced UV-B radiation treatments were simulated by 20% increase in its intensity. N2O fluxes were measured with a static opaque chamber-gas chromatograph method. The results showed that enhanced UV-B radiation did not change the seasonal patterns of N2O emissions. Compared to the controls, the enhanced UV-B radiation reduced N2O fluxes by 16.4% (p = 0.015) during the elongation-booting stage, while it had no significant effects on N2O fluxes in the turning-green and heading-maturity phases. During the turning green-overall heading span, the accumulative N2O was largely decreased by the enhanced UV-B radiation (p < 0.05). From the overall heading to maturity, however, the effects of enhanced UV-B on N2O emissions were not pronounced (p > 0.10). At the elongation-booting stage, enhanced UV-B increased soluble proteins content in leaves, NO3--N and NO4+-N content in rhizosphere soil, and soil microbial biomass C (Cmic) and N (Nmic; p < 0.05), as well as microbial biomass C:N ratio changing from 5.0 to 6.8. Our findings suggest that the effects of enhanced UV-B radiation on N2O emissions differed with winter wheat developmental stages. To assess the overall effects of enhanced UV-B radiation on N2O emissions from agroecosystems, nevertheless, more field measurements deserve to be carried out in various cropping systems.