[Effects of Nitrogen Fertilizer and Straw Returning Methods on NO Emissions in Wheat-Maize Rotational Soils].

In order to explore the impacts of nitrogen fertilizer and straw returning methods on NO emissions, a two-factor split-zone design was adopted for experimentation under the winter wheat-summer maize rotation model in the Guanzhong area of Shanxi, China. The main areas of interest were conventional nitrogen (G) and reduced nitrogen (70% G); the sub-areas were straw no return (N), straw return (S), and straw return + biochar (SB); we analyzed their impacts on NO emissions and crop yield, and the relationships with related impact factors. The results showed that the NO emissions peaks appeared in the wheat season and maize season treatments within 5-16 days after fertilization, and also appeared after rainfall. The NO flux was significantly and positively correlated with soil temperature and NH-N content. Regardless of the wheat season, maize season, or annual total NO emissions, the 70% GSB treatment was the lowest and the GS treatment was the highest. At the same level of nitrogen application, S treatment increased NO emissions, SB treatment could reduce NO emissions, both S and SB treatments could significantly increase crop yields, and SB production increased more; 70%G-level annual NO emissions, when compared with the G level, had been reduced by 40% to 48%, while the yield has not decreased significantly. Through comprehensive consideration, a reduction of nitrogen by 30% was achieved through the combination of straw + biochar on the basis of conventional nitrogen application, while ensuring high crop yields and the best NO emissions reduction.