| At present,the global climate is changing.The concentration of atmospheric CO2 increased dramatically.At the same time,due to the increase of CO2 concentration,the global temperature is also increased,and increased faster and faster.As the feedback of soil ecosystem,soil microbial ecosystem will be changed by this influence.Farmland soil is the main source of N2 O emission,and nitrogen availability is one of the most important factors affecting N2 O emission from farmland.Therefore,this experiment designed a simulated environment of control environment(T0C0),elevated atmospheric CO2 concentration(T0C1),increased temperature(T1C0),and the combination(T1C1).In order to explore the effects of different nitrogen treatments on enzymes and microorganism associated with N2 O emission wheat fields under the background of climate change,the abundance of enzymes and microorganisms associated with N2 O emission in soil were measured by using urea,slow-release nitrogen fertilizer and nitrification inhibitor nitrogen fertilizer.These will provide a theoretical basis for future wheat production to cope with climate change.In this study,soil samples at jointing-stage and booting stage of wheat in 2018 and 2019 were selected.Soil urease activity,soil protease activity,hydroxylamine reductase,nitrate reductase and nitrite reductase activities were measured by the sodium phenol-sodium hypochlorite colorimetry and the ninhydrin colorimetry.Solarbio kit(micromethod)were used to determine the activities of soil urease.The content of nitrate nitrogen and ammonium nitrogen of fresh soil in 2019 was determined by UV spectrophotometry.DNA was extracted and the abundance of related genes was determined by fluorescence PCR test.In addition,a part of the soil at booting stage in 2018 was selected for microbial community to analyze the abundance and structure of microbial community.The N2 O emission of each treatment in growing season of wheat from 2018 to 2019 was measured by static chamber method.Through the experiment,the main results of this study are as follows:(1)Slow-release nitrogen fertilizer and nitrification inhibitor had significant effects on the contents of ammonium and nitrate nitrogen in wheat field soil.The effect of slow-release nitrogen fertilizer was as follows: slow release of fertilizer reduced the contents of ammonium nitrogen and nitrate nitrogen at jointing stage in wheat field.The contents of nitrate nitrogen and ammonium nitrogen in soil at booting stage were higher than those of normal urea and nitrification inhibitor.The effect of nitrification inhibitor nitrogen fertilizer was as follows: the conversion of ammonium nitrogen to nitrate nitrogen was inhibited at jointing stage,and the content of ammonium nitrogen was significantly increased,while the content of nitrate nitrogen was decreased.At booting stage,there was no significant change in urea treatment compared with the control.(2)The activity of nitrite reductase in wheat field was consistent over four stages.The activity of nitrite reductase at jointing stage was significantly lower than that of control,but the activity of nitrite reductase at booting stage was significantly higher than that of control due to slow release of fertilizer effect.Nitrification inhibitor nitrogenous fertilizer had lower enzyme activity than control or no significant change compared with control.Slow-release nitrogen fertilizer could inhibit the urease activity in wheat field at booting stage.Nitrification inhibitor nitrogenous fertilizer had no significant effect on the urease activity in T0C1 at jointing stage except for the control environment at booting stage.In 2018,the activity of hydroxylamine reductase at jointing stage was significantly increased under all the conditions except T1C0,in which it was significantly inhibited by the two nitrogen fertilizers.Nitrification inhibitor reduced hydroxylamine reductase activity at the boot stage,and slow-release N significantly increased the activity of hydroxylamine reductase under T0C0 and T0C1.In 2019,the activity of the enzyme was increased by slow-release nitrogen and nitrification inhibitor under T0C0 and T1C0,and decreased or not changed significantly under the T1C0 or T0C1.The changes of nitrate reductase at four stages were different.At the jointing stage of 2019,slow-release nitrogen decreased the activity of protease in T0C0 and T0C1,while increased the activity of protease in T0C0 and T0C1.Nitrification inhibitor nitrogenous fertilizer significantly increased the activity of the enzyme in T1C1,but significantly decreased the activity of the enzyme in other environments.At booting stage,slow-release N fertilizer increased the activity of this enzyme in all treatments.Nitrification inhibitor Nitrogen fertilizer increased protease activity except in control environment.(3)The reduction in N2 O emissions from 2018 to 2019 was significant under slow-release nitrogen fertilizer or nitrification inhibitor nitrogen fertilizer,and the emission reduction effects of both were similar.(4)Bacterial amo A gene expression was inhibited by nitrification inhibitor and slow-release nitrogen fertilizer.The abundance of each treatment was significantly lower than that of the control.Under nitrification inhibitor nitrogen treatment,gene abundance of amo A,nir S,nir K and nos Z of Archaea were increased under T1C0 and T0C1,but decreased under the other treatments.Under the treatment of slow-release nitrogen fertilizer,the changes of the archaea amo A and nirS genes and nitrification inhibitor nitrogen fertilizer were consistent.(5)Slow-release nitrogen fertilizer and nitrification inhibitor nitrogen fertilizer had significant effects on microbial community structure in wheat field.Proteobacteria was the dominant species in the bacterial community.Ascomycetes was the dominant species in the fungal community.The effect of elevated CO2 concentratrion and increased temperature on the community was greater than that of different nitrogen treatments,and the effect of elevated CO2 concentratrion on the bacterial community was greater than that of fungi. |
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