| Nitrous oxide?N2O?is one of third major greenhouse gases carbon dioxide?CO2?and methane?CH4?and attracted great attention of intermational society with it's great warming potential.A large amout nitrogen fertilizer was applied to tea field in hilly area in subtropical China,aiming to produce high qulity of fresh leaves.In a nother way,tea field may be an important N2O source with large amount nitrogen fertilizer application and it's acidic soil environment resulting from excessive chemical fertilizer;however,there are few of reports about N2O emission from tea field for long-term observation,especially in subtropical hilly eare in China.In this study,tea field was taken as research subject,N2O emissions strength of tea field and main driving factor were investigated by field experiments and indoor culture experiments and analyzed the soil samples and gas samples,and spatial distribution characteristics of N2O emissions in tea field in dry and wet season were verified,besides,annual N2O emissions in tea field and its emission factors were estimated,besides,the N2O emission factor of tea field was calculated by stepstep regression equation to explain the environmental factors of N2O emission in tea field.The main results were summarized as follows:1.The results of field experiment1)The two forms of mineral nitrogen in tea field soil have similarity and diversity in seasonal change and year-to–year variation under different under different fertilization management.The content of NH4+-N in soil,which similarity express in high-levels in spring and summer while low-levels in autumn and winter,besides,the extent of NH4+-N change level in spring and summer more than autumn and winter.From 2014 to 2016,The content of NH4+-N levels in soil,ecological engineering?EE?higher than carbon of biomass?BC40?,besides,the peak of NH4+-N appeared in the early April to the end of April under the treatment of EE,and the treatment of BC40 processing was delayed about half a month than EE.The similarity and difference of the content of NO3--N in soil under the two treatments are roughly the same as that of NH4+-N,but the content of NH4+-N in soil is much higher than that of NO3--N.2)During the observation period,BC40 has the ability to improve the dissolved organic carbon and reduce the variation of it in the tea field,but as time goes on,this ability will gradually decrease.The content of DOC in soil is greater than that of BC40,but the variation of DOC is more than that of BC40 in seasonal change and year-to–year variation.3)During the observation period,under the BC40 management,soil water content higher than EE mannegement,but the annual change of soil water content under EE treatment was less than that of BC40.The rate of N2O emission BC40 treatment is higher than that of EE,Therefore,the soil N2O emission of BC40 is greater than that of EE in tea field.According to the research results of tea plantation yield,it shows that EE treatment not only reduce N2O emission but also realize win-win situation between economy and environment.2.Analysis of main control factor of soil N2O emission in tea field under different managementThe N2O emission is significantly correlated with the content of mineral nitrogen and soil water content and 5cm temperature of soil surface under BC40 and EE treatment.The dissolved organic carbon is significantly correlated with the N2O emission under BC40 treatment,but under EE treatment,it's correlated with the N2O emission.In monsoon period,the N2O emission is significantly correlated with soil nitrogen?NH4+-N and NO3--N?,content,soil water content?SWC?and dissolved organic carbon?DOC?.The N2O emission is a significant negative correlation with the surface 5cm temperature under BC40 treatment,and it is a weak positive correlation under EEtreatment.In dry season,the N2O emission is significant correlation with the content of NH4+-N under EE treatment,while the correlation of BC40treatment is not obvious.The N2O emission is not obvious correlation with the content of NO3--N and DOC under BC40 and EE treatment,besides,it's showed significant negative correlation with SWC and significant positive correlation with urface 5cm temperature.Based on the calculation of the selected five indicators,it is shown that the five indexes can explain the reason of 59.2%N2O emission in BC40treatment,and only 55.7%in EE treatment.3.Soil culture experiment of indoor tea field.The N2O cumulative emission of soil was significantly correlated with the soil moisture content under M0 and M2 treatment.It showed drastic change under 80%WFPS.M2 treatment promotes N2O emissions in tea soil and it increased with the improved soil water content obviously.Both the M0 and M2 treatments showed their largest N2O emissions under 100%WFPS.When the dry soil without pre-culture,the began of experiment appear a dry-wet alternate process after adding solution,wihich lead to the stimulating effect,so it make N2O emissions of high value in the initial experiment,therefore,soil pre-culture should be carried out in subsequent culture experiments to avoid this phenomenon. |
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