[Effects of biochar application three-years ago on global warming potentials of CH 4 and N 2 O in a rice-wheat rotation system.]

To evaluate the long-term effects of biochar amendment on greenhouse gas emissions (GHGs), a field experiment was conducted to examine the effects of 3-year field-aged biochar (B3 ) and fresh biochar (B0 ) on global warming potential (GWP) and greenhouse gas intensity (GHGI) of methane (CH4 ) and nitrous oxide (N2 O) in a typical rice-wheat rotation system. Four treatments were established as control without nitrogen fertilizer (CK), urea without biochar (N), urea with fresh biochar amended in 2015 (NB0 ), and urea with 3-year field-aged biochar amended in 2012 (NB3 ). Results showed that both the NB0 and NB3 treatments obviously increased soil pH, soil organic carbon (SOC), total nitrogen (TN) and influenced the potential activity of functional microorganisms related to GHGs compared to the N treatment. Relative to the N treatment, the NB3 treatment significantly improved crop yield by 14.1% while reduced the CH4 and N2 O emissions by 9.0% and 34.0%, respectively. In addition, the NB0 treatment significantly improved crop yield by 9.3%, while reduced the N2 O emission by 38.6% though increased the CH4 emissions by 4.7% relative to the N treatment. Moreover, both the NB0 and NB3 treatments could significantly reduce both GWP and GHGI, with NB3 being more effective in simultaneously mitigating the GHGs emissions and enhancing crop yield. Since field-aged biochar showed obvious effects on GHGs mitigation and carbon sequestration after 3 years, biochar incorporations had long-term effect on GHGs mitigation and crop production in the rice-wheat rotation system.