生物炭和有机肥对菜地土壤N2O排放及硝化、反硝化微生物功能基因丰度的影响

通过室内培养试验和实时荧光定量PCR技术,研究了田间施用生物炭和有机肥对菜地土壤氧化亚氮(N_2O)排放、氨单加氧酶(amo A)和亚硝酸盐还原酶(nir S、nir K)、氧化亚氮还原酶(nos Z)基因丰度的影响,并探讨功能基因丰度对N_2O排放的影响.试验设置5个处理:CK(对照)、N(尿素)、N+BC(尿素和生物炭)、N+M(尿素和有机肥)和N+BC+M(尿素、生物炭和有机肥).结果表明,与CK处理相比,各施肥处理均降低了土壤氨氧化细菌(AOB)和氨氧化古菌(AOA)丰度,增加了nir K、nir S和nos Z基因丰度,并提高了培养期间N_2O累积排放量.与N处理相比,N+BC处理的土壤p H值提高了11.1%,并增加了AOB、AOA、nir S、nir K和nos Z基因丰度,增幅分别为105.8%、57.3%、22.0%、176.2%和204.9%,同时显著降低了培养期间N_2O累积排放量,降幅为58.1%;N+M处理增加了nir K和nir S基因丰度,增幅分别为58.8%和7.1%,对N_2O排放的影响不显著;N+BC+M处理增加了AOB、nir K、nir S和nos Z基因丰度,增幅分别为30.7%、68.7%、6.5%和84.5%,降低了N_2O累积排放量,降幅为14.4%.生物炭通过增加amo A、nir S和nir K基因丰度间接增加N_2O排放,同时通过增加nos Z基因丰度促进N_2O还原,综合效应表现为降低了菜地土壤N_2O排放.因此,通过施用生物炭改善土壤性质,增加功能基因丰度,降低土壤N_2O排放,是一种较好的N_2O减排措施.施用有机肥可以增加反硝化作用功能基因丰度,但对N_2O减排效果不显著.

Effects of biochar and organic manure on N2O emissions and the functional gene abundance of nitrification and denitrification microbes under intensive vegetable production

A 6-week incubation experiment with vegetable soils was conducted using real-time quantitative polymerase chain reaction (PCR) method to investigate the effects of biochar and organic manure on N₂O emissions and functional marker genes of ammonia monooxygenase gene (amoA), nirK, nirS and nosZ, which are responsible for nitrification and denitrification. The field experiment included five treatments as following, CK:control, N:urea nitrogen fertilizer, N+BC:urea nitrogen fertilizer+biochar, N+M:urea nitrogen fertilizer+organic manure fertilizer and N+BC+M:urea nitrogen fertilizer+biochar+organic manure fertilizer. Results showed that compared with the CK treatment, the treatments receiving urea (N, N+BC, N+M and N+BC+M) greatly inhibited the copies of ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA), stimulated the copies of nirS, nirK and nosZ genes and increased N₂O cumulative emissions throughout the incubation period. Compared with the N treatment, the N+BC treatment significantly increased soil pH by 11.1%, and simulated the copies of AOB, AOA, nirS, nirK and nosZ genes by 105.8%, 57.3%, 22.0%, 176.2% and 204.9%, respectively, thus decreased cumulative N₂O emissions by 58.1%. Although it greatly increased nirK and nirS genes by 58.8% and 7.1%, respectively, the N+M treatment had no significant influence on N₂O emissions as compared with the N treatment. The N+BC+M treatment greatly stimulated AOB, nirK, nirS and nosZ gene copies by 30.7%, 68.7%, 6.5% and 84.5%, respectively, and finally decreased cumulative N₂O emissions by 14.4% as compared with the N treatment. Results suggested that biochar addition decreased overall N₂O emissions by enhancing the expression of nosZ gene although it enhanced N₂O production by stimulating the expression of amoA, nirK and nirS genes. In conclusion, the addition of biochar could serve as an appropriate practice for mitigating N₂O emissions and increasing N-cycling microbial community under intensive vegetable fields. However, the addition of organic manure had little effects on N₂O emission although it increased the gene abundance of denitrification microbes.