| Aerated drip irrigation（ADI）is a technique through which delivers water,fertilizer,and gas（oxygen）to crop rhizosphere via subsurface drip irrigation system according to crop requirements,resulting in an increase of available oxygen concentration,enhancing yield and improving water and nitrogen use efficiencies under hypoxic condition.This new technique changes the oxygen concentration and water distribution in soil,and thus affects the nitrogen cycling process,including nitrification and denitrification,and then influences soil nitrous oxide（N2O）emissions.However,the effects of ADI on soil N2O emission under the condition of crop cultivation and non-crop cultivation,and its main influencing factors were both unknown.The aim of this research was to resolve the knowledge gaps in the effects of ADI on N2O emission from greenhouse vegetable soils.To understand the influence of aeration,nitrogen application and irrigation on soil N2O emission in greenhouse vegetable field,indoor incubation experiment and the pepper cultivation experiment in greenhouse were set.Soil N2O flux was monitored via using static chanber-gas chromatograph technique.And soil temperature,air temperature,water-filled pore space（WFPS）,dissolved oxygen（DO）,Oxydation-reduction potential（Eh）,Oxygen diffusion rate（ODR）,soluble organic carbon（DOC）,mineral nitrogen（NO3--N and NH4+-N）content and nitrification and denitrification gene were also measured.Comprehensive contribution of influencing factors（physical,chemical and microbial factors）to N2O emission under ADI was analyzed by correlation,regression and structural equation model（SEM）.In addition,technical scheme of ADI coordinated with economic and environmental effects was proposed.Main results were obtained as below.（1）In the condition of soil incubation experiment,all treatments of soil N2O flux were increased from the beginning,and then became lower.The peak of soil N2O emission occurred at 1 d after irrigation,and the valley value of soil N2O emission occurred at 4 d after irrigation.Aeration and addition of irrigation amount could significantly increase average values,peak values and total values of N2O flux.Compared to drip irrigation,the average values,peak values and total values of ADI increased 49.89%,163.05%,and 112.37%,respectively.The average values,peak values and total values of full irrigation increased 103.27%,125.29%,and 73.46%compared to deficit irrigation,respectively.（2）Aeration could significantly increase soil DO,Eh,and ODR in the depth of 10 and 20cm,improve soil aeration.However,aeration had no significant effect on soil WFPS.An increase of irrigation amount resulted in an increase of soil WFPS in depth of 10 and 20 cm,caused a decrease of soil DO,Eh,and ODR in depth of 10 and 20 cm.Aeration could significantly increase the content of soil NO3--N in the depth of 010 cm.However,aeration had no significant effect on the content of soil of NH4+-N in the depth of 010 cm.An increase of irrigation amount resulted in a decrease of the content of soil NO3--N and NH4+-N.Through analysis SEM of soil N2O emission in the condition of non-planting,the WFPS,Eh,and NO3--N content were main influencing factors under ADI.（3）Aeration and an increase of nitrogen rate and irrigtion amount resulted in an increase of soil N2O emission peak,cumulative N2O emission and yield-scaled N2O emission in greenhouse pepper production system under ADI.The yield-scaled N2O emission of ADI averagely increased 20.03%compared to drip irrigation.Compared to deficit irrigation treatment,yield-scaled N2O emission of full irrigation averagely increased 8.76%.Compared to 75%conventional nitrogen,yield-scaled N2O emission of conventional nitrogen averagely increased 17.37%.Considering crop yield and yield-scaled N2O emission of different combination,the combination of 75%conventional nitrogen aerated deficit drip irrigation was an optimal water-fertilizer-gas implementing model under ADI.（4）In the pepper cultivation experiment,aeration and an increase of nitrogen rate and irrigation amount had no significant on soil temperature.An increase of irrigation amount caused an increase of soil WFPS,while aeration and nitrogen application had no significantly effect on soil WFPS.Aeration could significantly improve pepper field soil DO concentration compared to drip irrigation,while the increase of irrigation amount and nitrogen rate had no significantly effect on soil DO.An increase of nitrogen applicant resulted in an increase of the content of soil NO3--N,while had no effect on the content of soil NH4+-N.Through analysis SEM of soil N2O emission in the condition of planting,the soil temperature,WFPS and NO3--N content were main influencing factors under ADI.This research provides a reference for the selection of water,nitrogen and gas coupling model and demonstrates the great important significance of verifying N2O emission mechanism. |
