生物炭和脱硫石膏混施对稻田碳排放的影响

为探究脱硫石膏和生物炭混施对稻田CO₂、CH₄减排和碳收支的影响,在黄壤性稻田中设置了生物炭与脱硫石膏施用剂量比不同的6个处理,并利用静态箱-气相色谱法对土壤CO₂、CH₄排放通量进行了为期一年的监测。试验的6个处理分别为裸地(B)、种植水稻(R)、种植水稻+4 t·hm^-2生物炭(RC4)、RC4+4 t·hm^-2脱硫石膏(RC4G4)、RC4+8 t·hm^-2脱硫石膏(RC4G8)和RC4+16 t·hm^-2脱硫石膏(RC4G16)。结果表明,处理R在稻季的CH₄排放量为86 kg·hm^-2;单施生物炭使CH₄排放量增加了52%,进一步混施脱硫石膏则使CH₄排放量下降了69%~91%。各处理在休闲期的CH₄排放量都比较低(6.24~13.4 kg·hm^-2)。施用生物炭和脱硫石膏对稻季土壤CO₂排放无显著影响;与其他处理相比,RC4G4处理在休闲期的CO₂排放量有所增加。不同处理的土壤CO₂年排放量为4 525~6 634 kg·hm^-2,其中休闲期的贡献率为68%~76%。就全年而言,仅RC4G16处理的碳输入略大于碳输出,表现为碳中和效应;其他处理则皆表现为大气碳源,净排放量为573~4 065 kg·hm^-2。综上所述,本试验中单施生物炭促进了温室气体排放,而脱硫石膏的施用抵消了生物炭对温室气体减排的负面效应,且施用效果随剂量的增加而增强。

Effects of mixed application of biochar and desulfurized gypsum on carbon emissions from a paddy field

To investigate the effectiveness of the combined application of biochar and desulfurized gypsum in reducing CO₂ and CH₄ emissions and the carbon budget in rice fields, six treatments were established in a paddy field and the soil CO₂ and CH₄ fluxes were measured for one year using the static chamber-GC method. The treatments were as follows:bare plot(B), rice planting plot(R), R amended with biochar at a rate of 4 t·hm^-2(RC4), RC4 plus desulfurized gypsum(G) applied at a rate of 4 t·hm^-2(RC4G4), RC4 plus G applied at a rate of 8 t·hm^-2(RC4G8), and RC4 plus G applied at a rate of 16 t·hm^-2(RC4G16). During the rice growing season, the R plot released CH₄ at a rate of 86 kg·hm^-2. Compared with the amount emitted by R, CH₄ emission was enhanced by 52% with the exclusive application of biochar(RC4), but this was suppressed by 69%-91% with the application of desulfurized gypsum. CH₄ emissions during the fallow period were relatively low for the different treatments(6.24-13.4 kg·hm^-2). By contrast, the impacts of biochar and desulfurized gypsum on the soil CO₂ flux were much more significant during the fallow period than during the rice growing season. The annual soil CO₂ emissions from the differently treated plots ranged from 4 525 to 6 634 kg·hm^-2, 68%-76% of which were emitted during the fallow period. According to the annual carbon budget, the RC4G16 treatment was carbon neutral, whereas the other treatments acted as a net atmospheric carbon source with emission intensity values ranging from 573 to 4 065 kg·hm^-2. In conclusion, in this study, the application of biochar alone promoted greenhouse gas emissions, whereas the additional application of desulfurized gypsum offset the negative effect of biochar and reduced greenhouse gas emissions, with the effect increasing with increase in the dosage.