Nitrous Oxide And Nitric Oxide Emissions From A Tea Plantation With Biochar Application

Nitrous oxide(N2O)is one of six Greenhouse Gases(GHGs)defined in Kyoto Protocol which has the effect of global warming.Though nitric oxide(NO)is not one of the GHGs,it is involved in the process of ozone depletion as catalyst.Besides,it is easy to be oxidized into nitrogen dioxide(NO2).And the enrichment of NO2 may result in acid precipitation.N2O and NO are the two main reactive nitrogen gases which participate in the global nitrogen cycle process at atmosphere.Lots of researchers had continuously focused on the environmental problems such as global warming and air pollution incurred by N2O and NO.These two reactive nitrogen gases mainly come from farmland ecosystem including tea plantation through nitrification and denitrification in farmland soils.It is worth noting that the tea plantation is regarded as the main anthropogenic emission source of N2O and NO,while there were few researches on situ observation of N2O and NO emission from this field.In recent years,soil acidification at the tea plantation had presented the extensive and severe trend in China,especially in Jiangsu province.The existing research had indicated soil acidification could not only have bad effects on tea growing,tea yield and tea quality but also incur substantial N2O and NO emissions.Meanwhile,in-depth research on the character and function of biochar had been doing.More and more researchers apply it in soil to get the effect of nitrogen fixation and greenhouse gases mitigation.This study performed situ observation of N2O and NO emission using a closed Chamber-Gas Chromatography method.One study content is researching the seasonal characters of N2O and NO emissions from soil between rows with biochar application and chemical fertilizer application.The other study content is estimating seasonal and annual accumulative emissions of N2O and NO respectively.The ultimate goal is to analyze the environmental factors responsible for changes in N2O and NO emissions.Through this study,the results were as follows:1)N2O emission in the soil with application of chemical fertilizer mixed biochar presented obvious seasonal character,which was high emissions in the period from summer to autumn and low emissions in the period from winter to spring.During annual observation period,the average fluxes of N2O was 372.35 ?g N2O-N m-2 h-1.N2O annual cumulative emission was 32.21 kg N2O-N ha-1 wherein cumulative emission of winter,spring,summer and autumn were respectively 0.99 kg N2O-N ha-1,4.35 kg N2O-N ha-1,20.24 kg N2O-N ha-1 and 6.21 kg N2O-N ha-1.And N2O cumulative emissions of summer plus autumn was accounting for 83%of annual total N20 cumulative emissions.NO emission in the soil with application of chemical fertilizer mixed biochar presented obvious seasonal character,which was high emissions in the spring and autumn while low emissions in the winter and summer.Across annual observation period,the average fluxes of NO was 14.23 ?g NO-N m-2 h-1.NO annual cumulative emission was 1.66 kg NO-N ha-1,wherein cumulative emission of winter,spring,summer and autumn were respectively 0.16 kg NO-N ha-1,0.43 kg NO-N ha-1,0.34 kg NO-N ha-1 and 0.73 kg NO-N ha-1.And NO cumulative emissions of spring plus autumn was accounting for 70%of annual total NO cumulative emissions.2)N2O emission in the soil with chemical fertilizer application presented obvious seasonal character,which was high emissions in the period from summer to autumn and low emissions in the period from winter to spring.During annual observation period,the average fluxes of N20 was 452.57 ?g N2O-N m-2 h-1.N20 annual cumulative emission was 38.02 kg N2O-N ha-1,wherein cumulative emission of winter,spring,summer and autumn were respectively 0.80 kg N2O-N ha-1,6.08 kg N2O-N ha-1,23.92 kg N2O-N ha-1 and 8.09 kg N2O-N ha-1.And N2O cumulative emissions of summer plus autumn was accounting for 84%of annual total N2O cumulative emissions.NO emission in the soil with chemical fertilizer application presented obvious seasonal character,which was high emissions in the summer and autumn while low emissions in the winter and spring.Across annual observation period,the average fluxes of NO was 17.68 ?gg m-2 h-1.NO annual cumulative emission was 1.65 kg NO-N ha-1,wherein cumulative emission of winter,spring,summer and autumn were respectively 0.06 kg NO-N ha-1 0.35 kg NO-N ha-1,0.47 kg NO-N ha-1 and 0.76 kg NO-N ha-1 And NO cumulative emissions of summer plus autumn was accounting for 75%of annual total NO cumulative emissions.3)It could enhance soil pH with biochar application.This study showed that the annual average soil pH enhanced 0.7 after applying 20 t ha-1 biochar.The annual total N2O cumulative emissions of soil with application of chemical fertilizer mixed biochar decreased by 15%compared with that of soil with chemical fertilizer application,while there was no difference between the annual total NO cumulative emissions of soil with application of chemical fertilizer mixed biochar and that of soil with chemical fertilizer application.4)Biochar could improve soil moisture retention property.In this study,the annual average moisture of soil with chemical fertilizer application was 51.4%WFPS(Water Filled Pore Space).And the annual average moisture of soil with application of chemical fertilizer mixed biochar was 77.8%WFPS.The result was soil moisture enhanced by 51%with biochar amendment.5)N2O fluxes in the soil between rows had significant positive correlations with soil temperature and moisture.However,there was a significant negative correlation between N2O flux and soil pH.NO fluxes in the soil between rows had significant positive correlations with soil temperature.However,there was a significant negative correlation between NO fluxes and soil moisture.As for the correlation between NO fluxes and soil pH,it was unapparent.