[Effects of Straw Returning and Biochar Application on Summer Maize Yield and Soil N₂O Emission in Guanzhong Plain]

Here, we investigated the effects of straw returning combined with biochar application on summer maize yield and soil nitrous oxide (N₂O) emissions, based on a field location trial in the Guanzhong Plain from 2019 to 2020. The soil N₂O emission rates were monitored using the static chamber-chromatography method. A comprehensive analysis of summer maize yields, soil N₂O emissions, and soil labile nitrogen components was conducted to clarify the effects of straw returning combined with biochar application on improving soil fertility, increasing summer maize yield, and reducing greenhouse gas emissions. The three treatments were no straw returning (S₀), straw returning (S), and straw returning combined with biochar application (SB). The results showed that the peak of N₂O emissions from each treatment occurred 10 d after the straw return, and the rate of soil N₂O emissions remained at a low level after 30 d of straw return. The rate of soil N₂O emissions showed highly significant positive correlations (P<0.05) with ammonium nitrogen (NH₄⁺-N), inorganic nitrogen (SIN), microbial nitrogen (MBN), and dissolved organic nitrogen (DON) contents. S significantly increased summer maize yield, cumulative N₂O emissions, yield-scaled N₂O intensity, and total nitrogen (TN) content by 7.4%-13%, 65.8%-132.2%, 54.6%-103%, and 27.8%-33%, respectively, compared to those in S₀. Although the trend for SB to increase summer maize yield (2.5%-3.3%) compared to that in S was not significant (P>0.05), SB significantly reduced cumulative N₂O emissions and yield-scaled N₂O intensity by 24.0%-27.3% and 26.4%-29.2%, respectively, compared to that in S. SB significantly reduced the rate of soil N₂O emissions by 45.1%-69.6% at the peak of N₂O emissions compared to that in S. Biochar application mitigated soil N₂O emissions induced by straw return and had a peak-shaving effect. SB significantly increased soil total N by 9.1%-12.2% compared to that in S. Combining summer maize yield, soil N₂O emissions, and TN content, SB not only improved soil fertility and summer maize yield but also reduced yield-scaled N₂O intensity, making it a suitable management practice that can be replicated to balance crop yield and environmental friendliness.