生物炭对褐土旱地玉米季氮转化功能基因、丛枝菌根真菌及N_(2)O释放的影响

Effects of biochar on nitrogen transformation functional genes abundances,arbuscular mycorrhizal fungi and N_(2) O emission of rainfed maize season in cinnamon soil

以豫西旱地玉米农田为研究对象,设置不同生物炭施用量处理(T0:不施用生物炭;T1:施用生物炭20 t/hm^(2);T2:施用生物炭40 t/hm^(2)),采用密闭式静态箱法测定N_(2)O排放通量和荧光定量PCR法分析丛枝菌根(arbuscular mycorrhizal,AM)真菌、氨单加氧酶(amoA)、亚硝酸盐还原酶(nirS、nirK)以及氧化亚氮还原酶(nosZ)的基因丰度,同时测定土壤理化性状的变化。研究结果表明,随着生物炭施用量的增加,土壤pH和含水量呈增加趋势,土壤有机碳、全氮和铵态氮含量显著提高,土壤容重和硝态氮含量显著降低。T1和T2处理土壤有机碳含量分别较T0显著提高38.44%和71.01%;T1和T2处理土壤铵态氮含量分别较T0显著增加15.89%和30.46%;T2处理土壤全氮含量较T0处理显著提高14.87%;T1和T2处理土壤硝态氮含量分别较T0减少10.57%和21.40%。随着生物炭施用量的增加,AM真菌侵染率显著增加,T1和T2处理分别较T0处理提高71.88%和115.88%;AOA、AOB、nirK和nirS基因丰度显著降低;nosZ基因丰度增加。施加生物炭处理的N_(2)O排放通量和累积排放量均低于不施生物炭处理,具体表现为:T0>T1>T2。相关分析表明,生物炭施用量与AM真菌基因丰度呈显著正相关;与nosZ基因丰度呈正相关;与AOA、AOB、nirK、nirS基因丰度呈极显著负相关。N_(2)O排放通量与AOA、nirK、nirS基因丰度呈极显著正相关;与土壤含水量和土壤硝态氮含量呈显著正相关;与AM真菌、nosZ基因丰度、易提取球囊霉素含量、铵态氮含量呈极显著负相关。集成推进树(ABT)分析表明,AOA对N_(2)O排放的影响最大,其次是AM真菌和nirS。总之,生物炭处理改善土壤理化性质、提高土壤AM真菌侵染率、调节硝化、反硝化相关功能基因的丰度,减少N_(2)O气体排放,为旱地农田合理施用生物炭减少N_(2)O气体排放提供理论依据。

Biochar soil amendments are attracting the increased attention as one strategy to improve soil microbially ecological environment and regulate soil nitrogen cycle.The rainfed maize cropland in the western Henan was established to study the effects of biochar application rates(T0:0 t/hm^(2),T1:20 t/hm^(2),and T2:40 t/hm^(2))on soil physicochemical properties and N_(2)O emission fluxes using the static chamber/gas chromatography method,and the function marker genes of arbuscular mycorrhizal(AM)fungi,ammonia monooxygenase gene(amoA),nirK,nirS and nosZ,which were responsible for nitrification and denitrification using real⁃time fluorescence quota PCR.The results showed that the soil pH and water content increased,soil organic carbon,total nitrogen and ammonium nitrogen content increased significantly,and soil bulk density and nitrate nitrogen content decreased significantly with increasing biochar applied.Compared with T0 treatment,soil organic carbon increased significantly by 38.44%and 71.01%under T1 and T2 treatments,respectively;soil ammonium nitrogen content increased significantly by 15.89%and 30.46%under T1 and T2 treatments,respectively;soil total nitrogen content increased significantly by 14.87%under T2 treatment;nitrate nitrogen content decreased by 10.57%and 21.40%under T1 and T2 treatments,respectively.Moreover,the AM fungi colonization rate and nosZ gene abundance increased significantly,and AOA,AOB,nirK and nirS gene abundance decreased significantly with increasing biochar applied.Compared with T0 treatment,AM fungi increased significantly by 71.88%and 115.88%under T1 and T2 treatments,respectively.The N_(2)O emission fluxes and emission accumulations under biochar addition were all lower than those under no biochar,ranked as T0>T1>T2.The correlation analysis showed that the abundance of AM fungi was significantly positively(P<0.05)correlated with the biochar rate,and the abundance of nosZ gene and biochar rate was significant.There was a significantly negative correlation between AOA,AOB,nirK,nirS gene abundance and biochar rate(P<0.01).The N_(2)O emission fluxes showed a significantly positive correlation(P<0.01)with AOA,nirK,nirS,soil water content and nitrate nitrogen,but significantly negatively(P<0.01)correlated with AM fungi,nosZ,ammonium nitrogen and extractable glomalin related soil protein content.Aggregated boosted trees(ABT)analysis showed that the relative influence of AOA on N_(2)O emission fluxes was the largest,followed by AM fungi and nirK.In summary,the application of biochar improved soil physicochemical properties,increased soil AM fungi colonization rates,regulated nitrification and denitrification functional genes,and reduced N_(2)O emission,which provided a theoretical basis for the rational application of biochar and reduction of N_(2)O emissions in rainfed maize cropland.