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Inhibited effect of biochar application on N2O emissions is amount and time-dependent by regulating denitrification in a wheat-maize rotation system in North China

Liu, Hongyuan, Li, Hongbo, Zhang, Aiping, Rahaman, Md Arifur, Yang, Zhengli
The Science of the total environment 2020 v.721 pp. 137636
Zea mays, biochar, corn, crop rotation, denitrification, field experimentation, gene dosage, greenhouse gas emissions, nitrous oxide, soil, winter wheat, China
Biochar application is considered an effective method of reducing nitrous oxide (N₂O) emissions in soil. However, the mechanism and temporal effect of different doses of biochar on N₂O emissions is still obscure. Here, we conducted a two-year field experiment to test the effects of different input amounts and frequencies of biochar on soil N₂O emissions in North China. Biochar was applied in six different treatments in a winter wheat and summer maize rotation system: applications of 0 t/ha biochar (C0), 2.25 t/ha biochar (C1), 4.5 t/ha biochar (C2), 9 t/ha biochar (C3), and 13.5 t/ha biochar (C4) each year, and a single application of 13.5 t/ha biochar (CS) in the first year. The results showed that biochar could inhibit N₂O emissions, reaching 20.6% to 60.1% in the wheat season and 18.1% to 39.4% in the maize season. The inhibitory effect of biochar on soil N₂O emissions was dependent on amount and time. C3 had the best results in the wheat season, although its inhibitory effect in the maize season was not as good relative to C4 due to the lower biochar application. In addition, CS significantly reduced (27.7%) the cumulative N₂O emissions in the first year, although the inhibitory effect disappeared in the second year. Biochar increased the nosZ gene copy numbers and promoted a reduction of N₂O in the soil via the denitrification process. In conclusion, the inhibition of N₂O emissions during denitrification is an important factor for reducing soil N₂O emissions by biochar, and the inhibition of biochar is influenced by the input amount and time.