EFFECTS OF BIOCHAR ON N_2O AND CH_4 EMISSIONS FROM PADDY FIELD UNDER RICE-WHEAT ROTATION DURING RICE AND WHEAT GROWING SEASONS RELATIVE TO TIMING OF AMENDMENT
通过分别在水稻季(R)和小麦季(W)设置对照(RB_0-N_0、WB_0-N_0)、单施氮肥(RB_0-N_1、WB_0-N_1)、20 t hm~(-2)生物炭与氮配施(RB_1-N_1、WB_1-N_1)、40 t hm~(-2)生物炭与氮配施(RB_2-N_1、WB_2-N_1)等8个处理,研究稻麦轮作周年系统N_2O和CH_4排放规律及其引起的综合温室效应(Global warming potential, GWP)和温室气体强度(Greenhouse gas intensity, GHGI)特征。结果表明:稻季配施20 t hm~(-2)生物炭对N_2O和CH_4的排放、作物产量及GWP和GHGI均都无明显影响;稻季配施40 t hm~(-2)生物炭能显著降低8.6%的CH_4的排放和9.3%的GWP,显著增加作物产量17.2%。麦季配施20 t hm~(-2)生物炭虽然对温室气体及GWP影响不明显,但显著增加21.6%的作物产量,从而显著降低21.7%的GHGI;麦季配施40 t hm~(-2)生物炭能显著降低20.9%和11.3%的N_2O和CH_4排放,显著降低15.7% 和23.5%的GWP和GHGI。因此麦季配施生物炭对减少N_2O和CH_4的排放、增加稻麦轮作产量及降低GWP和GHGI的效果较稻季配施生物炭效果更好。
英文摘要:
A field experiment was carried out in a paddy field under rice-wheat rotation, to study effects of biochar amended at the rice or wheat season on paddy CH_4 and N_2O emissions throughout the cycle of rotation, their consequential global warming potential (GWP) and greenhouse gas intensity (GHGI), with a view to providing some scientific basis for extrapolation of the use biochar in mitigating global warming potentials and in agricultural production as well. The field experiment was designed to last an entire cycle of crop rotation, that is, two cropping seasons, rice season and wheat season, and to have eight treatments in triplicate, i.e. Treatment RB_0-N_0 or CK (zero N fertilizer applied & zero biochar amended in the rice season),Treatment RB_0-N_1 (250 kg hm~(-2) N fertilizer applied & zero biochar amended in the rice season), Treatment RB_1-N_1 (250 kg hm~(-2) N fertilizer applied & 20 t hm~(-2) biochar amended in the rice season), Treatment RB_2-N_1 (250 kg hm~(-2) N fertilizer applied & 40 t hm~(-2) biochar amendment at rice season), Treatment WB_0-N_0 (zero N fertilizer applied & zero biochar amended in the wheat season),Treatment WB_0-N_1 (250 kg hm~(-2) N fertilizer applied & biochar amended in the wheat season),Treatment WB_1-N_1 (250 kg hm~(-2) N fertilizer applied & 20 t hm~(-2) biochar amended in the wheat season),and Treatment WB_2-N_1 (250 kg hm~(-2) N fertilizer applied & 40 t hm~(-2) biochar amended in the wheat season). Biochar was amended before rice transplanting on June 10,2012 and wheat seeding on November 10,2012. CH_4 and N_2O gas emission fluxes were monitored with the static chamber and gas chromatography method. Results show that Relative to Treatment RB_0-N_1 Treatment RB_1-N_1 did not have much significant effect on N_2O and CH_4 emissions, GWP and GHGI, while Treatment RB_2-N_1 significantly improved crop yield by 17.2%, and significantly reduced total CH_4 emissions and GWP by 8.6% and 9.3%, respectively. Treatment WB_1-N_1 did not have much effect on GHGI and GWP, but did increase wheat yield by 21.6%, which in turn significantly reduced GHGI by 21.7%. Treatment WB_2-N_1 significantly reduced N_2O and CH_4 emissions by 20.9% and 11.3%, respectively and GWP and GHGI by 15.7% and 23.5%, respectively. In terms of total GWP on a 100-year horizon, the treatments followed an order of RB_0-N_1 > RB_1-N_1 > WB_0-N_1 > WB_1-N_1 > RB_2-N_1 > WB_2-N_1 > RB_0-N_0 > RB_0-N_0,while in terms of GWPs per unit crop grain yield, they followed another, i.e. RB_0-N_1 > WB_0-N_1 > RB_1-N_1 > RB_2-N_1 > RB_0-N_0 > WB_1-N_1 > WB_0-N_0 > WB_2-N_1. Obviously biochar application is more effective in the wheat season than in the rice season, in reduciing N_2O and CH_4 emissions, lowering the GWP and GHGI and increasing crop yield of the rotation system. Although Treatment WB_2N_1 was lower than Treatment WB_1N_1 in N_2O and CH_4 emission, and also in wheat yield which to use depends on balance between GHG mitigation and grain yield. However, consequential effects and underlying mechanisms of the use of biochar in the field on scale need further field study Results incorporation at rice season had no significant difference on N_2O and CH_4 emissions, GWP and GHGI. Relative to the RB_0-N_1 treatment, the RB_2-N_1 treatment significantly improved crop yield by 17.2%, significantly reduced the total CH_4 emissions and GWP by 8.6% and 9.3%, respectively. The crop yield of biochar incorporation at wheat season with 20 t hm~(-2) significantly improved by 21.6%, and significantly reduced 21.7% GHGI compare with WB_0-N_1.