Characteristics Of Nitrous Oxide Emissions From Citrus Orchard Soil Under Different Fertilization Treatments

N₂O is an important greenhouse gas that accelerates global warming and causes ozone hole.Citrus industry is the backbone of China's fruit industry,and in the process of citrus production,in order to improve yields of fruit,citrus orchards often apply a large amount of chemical fertilizers,resulting in soil stagnation,soil fertility declines,orchard ecological degradation and other environmental pollution problems.N₂O emissions are one of the major loss pathways for fertilizers.At present,there is very little research on N₂ O emissions from citrus orchards,and even less research on how to apply fertilizer scientifically in citrus orchards to reduce N₂ O emissions.Therefore,this study seeks to find a reasonable use of fertilizer in citrus orchards through different fertilizer application and treatment experiments to provide a reference for mitigating N₂ O emissions from citrus orchards.In order to investigate the emission characteristics and generation mechanism of N₂ O from citrus orchards,three types of optimized fertilization treatments were set up at the Fenghuang Hill citrus planting base in Banyue Town,Danyang,Yichang City,Hubei Province.N₂ O fluxes were analyzed by the static opaque chamber and gas chromatography techniques.The main results are as follows:?1?N₂O emissions from citrus soils show a clear seasonal pattern,with N₂ O emissions from spring to summer?April?August?being significantly higher than those from autumn to winter?September?March?,and N₂ O emissions from summer being more concentrated than those from spring,accounting for 49.10 percent of total N₂ O emissions during the observation period,the main reason for these phenomena is that the soil temperature,moisture,and soil carbon and nitrogen contents have a seasonal dynamic change.Due to seasonal differences in N₂ O emissions,N₂ O emissions in 2018 are lower than those in 2019.?2?The N₂O fluxes from nitrogen treatment are significantly higher than those from non-nitrogen treatment?P < 0.01?,indicating that nitrogen fertilizer application can significantly promote N₂ O emissions but N₂ O fluxes does not increase with the increase of nitrogen fertilizer application.This is because with too much nitrogen applied,more nitrogen is lost in the soil in other pathways.?3?Organic fertilizer and green manure significantly promote soil N₂ O emissions at 0%,75%,100% nitrogen application levels,while organic fertilizer and green manure inhibit soil N₂ O emissions at 85% nitrogen application level.Due to the significant increase in soil DOC content?P < 0.01?at 85% nitrogen application level,adjusting the soil C/N ratio,while organic fertilizers consume a large amount of O2 in soil during the decomposition process,ultimately reducing N₂ O emissions.?4?Soil temperature,moisture,inorganic nitrogen contents and dissolved organic carbon contents were positively correlated with soil N₂ O emission fluxes,but only soil temperature and soil nitrate nitrogen contents were positively correlated with soil N₂ O emission fluxes?P < 0.01?.Green manure significantly improves the water holding capacity of the soil?P < 0.01?.?5?Soil temperature,moisture and nitrate are the main contributors to soil N₂ O emissions from citrus orchard.The contribution of soil temperature to soil N₂ O emissions was about 28.56%?57.40%.The contribution of moisture to soil N₂ O emissions was about 25.16%.The contribution of nitrate to soil N₂ O emissions was about 26.32%?34.71%.In summary,in the actual production process in the citrus production area of Danyang,Hubei province,it can be considered to reduce the application of nitrogen fertilizer by 15% on the increase of organic fertilizers or Green manure planting,which is beneficial for mitigating soil N₂ O emissions.