新疆棉田灰漠土氨氧化微生物群落对灌溉水盐度和施氮量的响应

Response of ammonia-oxidizing microbial community to irrigation water salinity and nitrogen application in grey desert soil of cotton field in Xinjiang

采用灌溉水盐度和施氮量两因素试验,其中灌溉水盐度设置2个水平:0.35 dS·m^(-1)(淡水,FW)和8.04 dS·m^(-1)(咸水,SW),施氮量设2个水平:0(不施氮,N0)和360 kg·hm^(-2)(施氮,N360),以咸水滴灌的棉田土壤为材料,测定了土壤理化性质和生物学指标,结果显示:(1)咸水滴灌显著增加土壤EC 1∶5和NH_(4)^(+)-N含量,分别增加了457.74%和73.02%,但显著降低土壤NO_(3)^(-)-N含量,降低了35.88%;施氮显著增加土壤EC 1∶5、NO_(3)^(-)-N和NH_(4)^(+)-N含量,分别增加了32.09%、668.33%和39.88%。(2)咸水滴灌显著降低了土壤潜在硝化势,较淡水处理降低了28.97%;施氮显著增加了土壤潜在硝化势,较不施氮处理增加了317.27%。(3)咸水滴灌显著降低氨氧化细菌(AOB)和全程氨氧化细菌A分支(amoA-clade-A)和B分支(amoA-clade-B)的基因拷贝数,分别降低了81.27%、73.49%和62.51%,但显著增加氨氧化古菌(AOA)的基因拷贝数,增加了487.94%;氮肥施用均显著增加了氨氧化微生物的基因拷贝数,分别增加了511.20%(AOA)、958.13%(AOB)、72.66%(amoA-clade-A)和31.18%(amoA-clade-B)。(4)氨氧化微生物优势菌属为假单胞菌属、嗜甲基菌属、亚硝化螺菌属、慢生根瘤菌属、链霉菌属、硝化螺菌属、寡养单胞菌属、食甲基菌属、螯台球菌属、囊胞杆菌属、亚硝基单胞菌属、红假单胞菌属、芽孢杆菌属和拉姆利式杆菌。(5)咸水滴灌降低了AOA的多样性和丰富度及amoA-clade-A的多样性,但增加了AOB和amoA-clade-B的多样性和丰富度及amoA-clade-A的丰富度;氮肥施用显著降低了AOA和AOB的丰富度及amoA-clade-A的丰富度和多样性,但增加了amoA-clade-B的丰富度和多样性。综上,盐分是影响氨氧化微生物群落结构的主要驱动因子,氨氧化古菌是土壤氨氧化作用的优势物种,而氨氧化细菌和全程氨氧化细菌A分支是咸水滴灌棉田氨氧化作用的主导微生物种群。

Irrigation water salinity and nitrogen application were used in this experiment.Two levels of irrigation water salinity were set as 0.35 dS·m^(-1)(fresh water)and 8.04 dS·m^(-1)(saline water),and two levels of nitrogen application were set as 0(no nitrogen application)and 360(nitrogen application)kg·hm^(-2)(represented by FWN0,FWN360,SWN0 and SWN360,respectively).In this study,cotton soil with saline water drip irrigation was used as material to measure the physicochemical properties and biological indexes,and the results showed that:(1)Saline water drip irrigation significantly increased soil EC 1∶5 and NH_(4)^(+)-N contents by 457.74%and 73.02%,but significantly decreased NO_(3)^(-)-N content by 35.88%;Nitrogen application significantly increased the contents of EC 1∶5,NO_(3)^(-)-N and NH_(4)^(+)-N in soil by 32.09%、668.33%and 39.88%.(2)Saline water drip irrigation significantly reduced the nitrification potential of soil,which was 28.97%lower than that of freshwater treatment.Nitrogen application significantly increased the nitrification potential of soil,which was 317.27%higher than that without nitrogen application.(3)Saline water drip irrigation significantly decreased the gene copies number of ammonia-oxidizing bacteria(AOB)and the A branch(amoA-clade-A)and B branch(amoA-clade-B)of complete ammonia oxidizing bacteria by 81.27%,73.49%and 62.51%,but significantly increased the gene copies number of ammonia-oxidizing archaea(AOA)by 487.94%.Nitrogen fertilizer application significantly increased the gene copies number of ammonia oxidizing microorganisms by 511.20%(AOA),958.13%(AOB),72.66%(amoA-clade-A)and 31.18%(amoA-clade-B).(4)The dominant bacteria genera of ammonia oxidizing microorganisms were Pseudomonas,Candidatus nitrosocosmicus,Nitrosospira,Bradyrhizobium,Streptomyces,Nitrospira,Stenotrophomonas,Methylovorus,Chelatococcus,Cystobacter,Nitrosomonas,Rhodopseudomonas,Bacillus and Ramlibacter.(5)Saline water drip irrigation decreased the diversity and abundance of AOA and the diversity of amoA-clade-A but increased the abundance and diversity of AOB and amoA-clade-B,and the abundance of amoA-clade-A.Nitrogen application significantly decreased the abundance of AOA and AOB,and the abundance and diversity of amoA-clade-A but increased the abundance and diversity of amoA-clade-B.In conclusion,salinity was the main driving factor affecting the community structure of ammonia-oxidizing microbial community,ammonia-oxidizing archaea were the dominant species of soil ammoxidation,and ammonia-oxidizing bacteria and the A branch of complete ammonia oxidizing bacteria were the dominant microbial populations of ammoxidation in saline water drip irrigation cotton fields.