基于稻田中氮肥配施生物炭的田间定位试验，研究了施用生物炭与氮肥对旱季稻田土壤理化性质、甲烷氧化与产生潜势及甲烷氧化菌和产甲烷菌丰度的影响。田间试验共设置5个处理：单施生物炭、单施氮肥、氮肥配施生物炭（生物炭设置两个水平）以及对照。结果表明：施用生物炭三年后显著提高了有机碳和微生物生物量碳含量（p﹤0.05），与单施氮肥处理相比，氮肥配施生物炭后可显著提高土壤pH。与对照相比，单施生物炭显著提高土壤甲烷氧化潜势。在施氮条件下，甲烷氧化潜势与生物炭施用量之间存在正相关关系，与氮肥配施20 t hm-2处理相比，40 t hm-2生物炭处理甲烷氧化潜势增长53.8%。氮肥配施高倍生物炭与配施低倍生物炭处理相比产甲烷潜势由0.001提高至0.002 mg kg-1 h-1；氮肥施用一定程度上抑制了甲烷氧化菌数量的增长，单施氮肥处理中产甲烷菌数量较对照处理显著增加了3.0%；单施或配施低水平生物炭显著增加土壤甲烷氧化菌数量。氮肥显著降低了甲烷氧化菌与产甲烷菌基因丰度比（pmoA/mcrA）。而在同氮肥水平下施加生物炭显著增加了土壤pmoA/mcrA比值，即生物炭对甲烷氧化菌的促进作用显著高于产甲烷菌，提高了旱季稻田土壤的甲烷氧化能力，因此有助于减少稻田土壤甲烷的排放。%Abstract[Objective]Amendment of biochar has a significant impact on methane(CH4)emission in paddy field,but it is still unclear about its mechanism,so further study should be done to clarify the issue and to provide a scientific basis for the use of biochar in the rice-wheat rotation system.[Method]Soil samples were collected from a paddy field of a field experiment on amendment of biochar and nitrogen (N)fertilizer after the crop of wheat was harvested in 2015 for analysis to assess effects of biochar and N fertilizer amendment on soil physiochemical properties,methane oxidation potential and methane production potential as well as gene abundances of methanotrophs and methanogens with thereal-time PCR technology. Biochar was added once to the paddy field before rice transplanting on June 10,2012. The field experiment was designed to have five treatments in triplicate,that is,Treatment N0B0(no nitrogen(N)and biochar (B)amended)as control,Treatment N0B1(only biochar amended,20 t hm-2),Treatment N1B0 (only N fertilizer amended,250 kg hm-2 urea),Treatment N1B1(250 kg hm-2 urea and 20 t hm-2 biochar amended,and Treatment N1B2(250 kg hm-2 urea and 40 t hm-2 biochar).[Result]Results show that Treatments N1B1 and N1B2 significantly increased soil organic carbon and microbial biomass carbon (p< 0.05),and soil pH,too,as compared with Treatment N1B0 treatment. Moreover,the abundance of methanotrophs and methanogens were found significantly related to some soil physiochemical properties. Statistical analysis shows that the copy number ofpmoAgene was significantly and positively correlated with soil microbial biomass carbon(r = 0.563,p< 0.05),but negatively with soil NH4+-N content (r = -0.573,p< 0.05). In addition,the copy number ofmcrA gene was positively related to soil total N(r = 0.675,p< 0.01),microbial biomass carbon(r = 0.713,p< 0.01)and soil organic carbon (r = 0.696,p< 0.01). Besides,methane oxidation potential was positively related to biochar application rate in the presence of N fertilizer(p< 0.05),and in Treatment N1B2,methane production potential increased from 0.001 mg kg-1 h-1 in Treatment N1B1 to 0.002 mg kg-1 h-1. Methane oxidation potential was 44.4% higher in Treatment N1B1 than in Treatment N1B0,while being 31.6% lower than in Treatment N0B1. Relative to Treatment N1B1,Treatment N1B2 increased methane oxidation potential from 0.26 to 0.40 CH4 mg kg-1 h-1. Treatment N0B1 significantly increased the log copy number ofpmoA gene,from 6.57 g-1dry soil in Treatment N0B0 up to 6.94 g-1 dry soil(p< 0.05). Compared with the control or Treatment N0B0,Treatment N1B0 inhibited increase in copy number ofpmoA gene a certain extent,while increasing the copy number ofmcrA gene by 3.0%,which indicates that nitrogen fertilizer can significantly stimulate growth of methanogens. Compared with Treatment N1B0,Treatment N1B2 was higher in copy number of both pmoA gene andmcrA gene,but Treatment N1B1 remained almost unchanged,which suggests that biochar amendment at 40 t hm-2 can significantly raise the abundance of methanotrophs and methanogens. Compared with Treatment N0B1,Treatment N1B1 greatly decreasedpmoA/mcrA ratio from 1.01 to 0.94,and methane oxidation potential by 31.6%. However,biochar amendment increasedpmoA/mcrA ratio in the treatments the same in nitrogen fertilizer level(p< 0.05).[Conclusion]All the findings in this experiment demonstrate that biochar amendment promotes methanotrophs and methanogens in abundane,but the effect is much higher on the former than on the latter,and consequently on methane oxidation capacity than on methane production potential. Therefore,it can be concluded that the practice of biochar amendment helps mitigate methane emissions in the paddy field during the wheat growing season.
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