Inhibitory Effects of Biochar on N2O Emissions through Soil Denitrification in Huanghuaihai Plain of China and Estimation of Influence Time

Abstract

Biochar application is considered an effective method for reducing nitrous oxide (N2O) emissions from soil. However, the mechanisms underlying the influence of various biochar dosages on soil N2O emissions and the duration of one-time biochar application remain unclear. The effects of different biochar application rates and a one-time application on soil N2O emissions in the Huanghuaihai Plain of China were investigated through a field experiment from 2020 to 2022. In the wheat and maize rotation system, six treatments were administered: no biochar (C0); 2 (C1), 4 (C2), 8 (C3), and 12 t/hm2 biochar (C4) applied annually; and a one-time application of 12 t/hm2 biochar (CS) in 2018. Our results indicate that, compared with C0, biochar significantly inhibited soil N2O emissions, particularly in the C3 and C4 treatments, with reductions of 31.36–56.21% and 36.92–52.45%, respectively. However, CS did not significantly affect soil N2O emissions during the study period. These findings suggest that the biochar’s inhibitory effect on soil N2O emissions is contingent upon the dosage and frequency of application. A structural equation model revealed that biochar decreases soil N2O emissions by enhancing the reduction in N2O during denitrification. Under the conditions of this experiment, based on a logistic ecological model, a one-time application of 12 t/hm2 biochar was projected to significantly reduce soil N2O emissions for approximately 1.77 years. On the whole, biochar reduces soil N2O emissions mainly by regulating N2O production through denitrification, and the duration of this inhibition of N2O emissions mainly depends on the application amount and frequency of biochar application.