[Effects of Nitrogen Fertilizer and Straw Returning Methods on N 2 O Emissions in Wheat-Maize Rotational Soils].

In order to explore the impacts of nitrogen fertilizer and straw returning methods on N ₂ O 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 N ₂ O emissions and crop yield, and the relationships with related impact factors. The results showed that the N ₂ O emissions peaks appeared in the wheat season and maize season treatments within 5-16 days after fertilization, and also appeared after rainfall. The N ₂ O flux was significantly and positively correlated with soil temperature and NH ₄ ⁺ -N content. Regardless of the wheat season, maize season, or annual total N ₂ O 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 N ₂ O emissions, SB treatment could reduce N ₂ O emissions, both S and SB treatments could significantly increase crop yields, and SB production increased more; 70%G-level annual N ₂ O 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 N ₂ O emissions reduction.