Effects of nitrogen co-application by different biochar materials on rice production potential and greenhouse gas emissions in paddy fields in northern China

The effects of the co-application of nitrogen (N) fertilizers and different biochar materials on rice yields and the GWP of paddy fields in northern China remain unclear. Herein, we conducted a 2-year field experiment to evaluate the effect of combined N fertilizer (three levels: N0, 0 kg N ha-1; N1, 210 kg N ha-1; and N2, 168 kg N ha-1) and biochar application (two levels: BM, maize straw biochar; and BR, rice-husk biochar) on rice yield and greenhouse gas (GHG) emissions. BR and BM significantly increased rice yield, in particular when applied with N2 fertilizer, by 4.89% and 4.48%, respectively, compared with no biochar. This was associated with a substantial increase in the effective panicles. Generally, the soil NH+4 -N after BR application was greater than that of BM, however, biochar addition reduced NO-3 -N. BM and BR addition also significantly reduced N2O emissions by 44.04-50.53% and 52.13-55.37%, and CH4 emissions by 38.72-39.74% and 26.40-33.55%, respectively. Moreover, N2 levels can further mitigate N2O and CH4 emissions. For each level of N application, BM and BR significantly reduced the GWP and GHGI, with the N2BM showing the best outcome. Overall, biochar application (especially maize straw biochar) in combination with 168 kg N ha-1 can stabilize rice yields and reduce GHG emissions from agricultural areas in northern China.& COPY; 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).