水氮耦合对设施农田土壤自养和异养硝化作用的影响

Interactive effects of water and nitrogen on autotrophic and heterotrophic nitrification in greenhouse soil

水氮措施影响设施土壤氮素的转化及硝化微生物活性,但水氮耦合对设施土壤自养和异养硝化作用差异的影响尚不明确。以连续8年设施水氮耦合田间定位试验土壤为研究对象,控制不同土壤田间持水量(WHC)(40%WHC、60%WHC和80%WHC)进行室内微宇宙培养试验,通过添加乙炔抑制剂抑制自养硝化途径,研究水氮耦合对设施土壤自养和异养硝化速率及参与自养硝化的氨氧化微生物的影响,分析氨氧化微生物氨氧化古细菌(AOA)和氨氧化细菌(AOB)对自养硝化作用的贡献。结果表明,水氮耦合下,不同硝化途径NH_(4)^(+)-N、NO_(3)^(-)-N含量以及参与自养硝化的AOA amo A和AOB amo A基因拷贝数均有显著差异。无乙炔培养7 d后,NO_(3)^(-)-N含量显著增加,而NH_(4)^(+)-N含量显著降低,AOA amo A和AOB amo A的基因丰度显著增加。添加乙炔后,NO_(3)^(-)-N、NH_(4)^(+)-N含量基本保持恒定,AOA amo A和AOB amo A基因丰度显著减少。水氮耦合显著影响自养和异养硝化速率,冗余分析(RDA)表明,NH_(4)^(+)-N含量、AOB amo A、NO_(3)^(-)-N-C_(2)H_(2)、AOA amo A可分别解释自养和异养硝化速率变异的68.9%、34.9%、32.8%和24.4%。设施土壤存在自养硝化和异养硝化两种途径,60%~80%WHC各施氮处理均以自养硝化为主,占总硝化速率的65%~86%;仅40%WHC下,氮纯养分量300和525 kg·hm^(-2)处理以异养硝化为主,占总硝化速率的61%~77%。AOB和AOA共同驱动自养硝化,且AOB贡献更大。

Water and nitrogen measures affect nitrogen conversion and nitrifying microbial activity in greenhouse soil,but the difference between autotrophic and heterotrophic nitrification under the interactive effects of water and nitrogen remains unclear.From an eight-year long term field experiment of irrigation and nitrogen in greenhouse,the greenhouse soils were used as the experimental soil,and an indoor microcosm experiment was conducted to control soil water holding capacity(WHC)(40%WHC,60%WHC and 80%WHC)and add acetylene inhibits heterotrophic nitrification.The interactive effects of water and nitrogen on soil autotrophic and heterotrophic nitrification rates and ammonia oxidizing microorganisms were explored,and the contribution of ammonia oxidizing microorganisms ammonia-oxidizing archaea(AOA)and ammonia-oxidizing bacteria(AOB)to nitrification was also investigated.The results showed that NH_(4)^(+)-N and NO_(3)^(-)-N contents,copy number of AOA amoA and AOB amoA genes had significant difference in different nitrification pathways under the interactive effects of water and nitrogen.After 7 days incubation without acetylene,NO_(3)^(-)-N content was increased significantly,while NH_(4)^(+)-N content was decreased significantly.The gene abundance of AOA amoA and AOB amoA were increased significantly.After adding acetylene,NO_(3)^(-)-N and NH_(4)^(+)-N content remained constant,the gene abundance of AOA amoA and AOB amoA decreased significantly.The interactive effects of water and nitrogen had a significant effect on the autotrophic and heterotrophic nitrification rates.Redundancy analysis indicated that NH_(4)^(+)-N content,AOB amoA,NO_(3)^(-)-N-C_(2)H_(2),and AOA amoA could explain 68.9%,34.9%,32.8%and 24.4%of the variation in autotrophic and heterotrophic nitrification rate,respectively.There are two nitrification pathways of autotrophic and heterotrophic nitrification in the greenhouse soils.All nitrogen treatments were dominated by autotrophic nitrification under 60%-80%WHC,accounting for 65%-86%of total nitrification rate.Heterotrophic nitrification was the main nitrification pathway only under 300 and 525 kg·hm^(-2)treatments of 40%WHC,accounting for 61%-77%of total nitrification rate.Both AOA amoA and AOB amoA can drive the autotrophic nitrification,and AOB amoA has more contribution.