| Plastic film mulching can improve soil conditions and increase crop yields,and is an important and common farmland management measure.Biochar is a new type of carbon sequestration and emission reduction material,and its impact on crop growth,soil environment and greenhouse effect has been studied and reported by many scholars.However,the mitigation effect of biochar varies with the type of biochar,the amount of biochar added,and the type of soil,and the effect of biochar on soil N2O emissions over time is uncertain.Moreover,the simultaneous effects of plastic film mulching and biochar addition on N2O in vegetable fields are still unclear.In response to the above problems,this article takes a typical hot pepper-radish rotation vegetable field in Southwest China as the research object,using static dark box/gas chromatography,and at the National Purple Soil Fertility and Fertilizer Benefit Monitoring Station of Southwest University from October 2019 to December 2020.The in-situ observation time was carried out to study the effects of different mulching treatments（film mulching,namely,F treatment;non-film mulching,namely,NF treatment）on vegetable soil N2O emission flux,cumulative emissions,soil profile N2O concentrations,soil moisture,temperature and soil carbon and nitrogen content under the biochar addition levels of 0,20 and 40 t·hm-2（using B0,B20 and B40,respectively）,in order to reveal the effect of plastic film mulching and biochar application on vegetable soil N2O emission,time effect and the influence law of driving factors.Provide a theoretical basis for exploring farmland management measures to reduce N2O emissions from vegetable fields.The main conclusions are as follows:（1）The effect of film mulching on N2O emission from ridges was greater than that on furrows.Film mulching significantly increased the N2O emission fluxes on ridges during the radish season（P<0.05）.In the first year and the second year of the radish season,the film mulching increased the N2O emission flux on the ridges treated with B0,B20,and B40 by 24.07%,24.24%,62.88%and 45.61%,3.99%,and 48.47%,respectively.There were no significant effect on the N2O emission flux from the ridges and furrows of the hot pepper season and the furrows of the radish seasons（P>0.05）.the effect of biochar on the radish season in the first year and the effect of the N2O emission flux on the ridge in the hot pepper season were not significant（P>0.05）,but it significantly reduced the N2O emission flux on the ridge in the radish season in the second year（P<0.05）.In the second year of radish season,compared with B0,B20 and B40 significantly reduced the N2O emission flux under F and NF treatments by 79.51%,58.18%and 60.76%,60.38%,respectively.In addition,biochar also significantly increased the N2O emission flux in the furrows of the first year of radish season under F treatment at the B40 addition level,by 67.56%（P<0.05）.However,biochar had no significant effect on the N2O emission flux from furrows in other planting seasons（P>0.05）.（2）Plastic film mulching promoted the N2O emission from vegetable field,especially the radish season（P<0.05）.Film mulching significantly increased the weighted average N2O emission fluxes of the test plots at the level of B0,B20 and B40biochar addition by 17.56%,28.17%and 64.14%during the first year of the radish season,and increased the weighted average of N2O emission fluxes in the test plots at the levels of B0,by 32.60%,during the seconrd radish season;Biochar had no significant effect on N2O emissions in the first year of radish season and hot pepper season（P>0.05）,but it significantly reduced the N2O emissions in the second year of radish season（P<0.001）.During the second radish season,the weighted mean values of the average N2O emission fluxes of F-B0,F-B20 and F-B40 were 130.79±26.24,42.05±7.29 and 67.15±5.68μg·m-2h-1,respectively.And the weighted mean values of the average N2O emission fluxes of NF-B0,NF-B20 and F-B40 were 88.15±5.98,62.66±21.98 and 45.71±1.61μg·m-2h-1,respectively.Compared with B0,B20 and B40reduced the weighted average value of N2O emission flux of each test plot of F treatment and NF treatment by 67.85%（P<0.05）,48.66%（P<0.05）and 28.92%,48.76%（P<0.05）,respectively.（3）Plastic film mulching increased the N2O cumulative emissions of vegetable fields.In the first year of the radish season,F significantly increased the weighted average of the cumulative N2O emissions of B0,B20 and B40 treatments by 35.04%、1.11%和58.80%respectively（P<0.05）.In the hot pepper season,F significantly increased the weighted average of the cumulative N2O emissions of each biochar treatment by 40.39%、33.2%和33.16%（P<0.05）,respectively.In the second year of the radish season,mulching significantly increased the weighted mean value of the cumulative N2O emissions of B0 treatment by 33.12%（P<0.05）,while the impact on N2O emissions of other biochar treatments was not significant（P>0.05）;Biochar showed the promotion of N2O emission in the first year of radish season（P>0.05）,while shows the effect of reducing N2O in the hot pepper season and the second year of radish season.In the second year of the radish season,under treatment F,compared with B0,B20 and B40 significantly reduced the weighted average of cumulative N2O emissions by 67.71%and 48.89%（P<0.05）.Under NF treatment,B20 and B40 reduced the weighted average value of cumulative N2O emissions by 28.67%和48.00%,respectively,and the emission reduction effect of B40 reached a significant level（P<0.05）.（4）Plastic film mulching significantly increased the yield of radish（P<0.05）.In the first and second years of radish season,mulching significantly increased the yields of B0,B20 and B40 biochar treatments by 18.06%,24.70%,9.98%,and 41.80%,30.52,43.11%;The effect of biochar on the yield of radish was not significant（P>0.05）.Moreover,Our results demonstrated that NF with 20t·hm-2 biochar application in the second year of radish season when biochar showed emission reduction effect is a more suitable agronomic practice to simultaneously mitigate N2O emissions while increasing crop yields,because of the lowest yield-scaled N2O emission under F-B20 treatment.（5）The results of the three-factor analysis of variance showed that both plastic mulching and biochar significantly increased the N2O concentration in the two-year radish season（P<0.05）,but they had no significant effect on the N2O concentration in the hot pepper season（P>0.05）,Indicating that biochar has increased the potential risk of N2O emissions in the radish season.（6）In the radish season,the mulching film and the addition of biochar had no significant effect on the soil weight and water content and soil temperature（P>0.05）.The soil moisture in the radish season as a whole showed that the F treatment was higher than the NF treatment,and the hot pepper season The opposite is true.In the hot pepper season,the effect of film mulching on soil moisture was not significant（P>0.05）,but it significantly increased the soil temperature of 5cm underground（P<0.05）.The soil temperature of different treatments at the addition level of B0,B20 and B40 biochar were respectively F（25.67℃）>NF（24.95℃）,F（26.25℃）>NF（24.65℃）and F（25.67℃）>NF（23.92℃）,the mild and humid climate in southwestern China is the warming and moisturizing of the film.The important reason why the effect is not obvious.In addition,biochar has little effect on soil moisture and temperature in the hot pepper season（P>0.05）;in the entire planting season,soil nitrate nitrogen（P<0.05）,ammonium nitrogen（P<0.05）and organic carbon（P>0.05）>0.05)The content is basically that the F treatment is higher than the NF treatment,but the effect of film mulching on the total nitrogen content of the soil is not obvious（P>0.05）;biochar reduces the soil inorganic nitrogen content of the F treatment to a certain extent,and has a negative effect on the NF The influence of inorganic nitrogen content in the treatment is not obvious（P>0.05）.Biochar reduced the soil ammonium nitrogen content of F treatment（P>0.05）and the soil nitrate nitrogen content of radish season F treatment in the three planting seasons,and the F-B40 treatment in the second year of radish season made the soil nitrate nitrogen The content was significantly reduced by 95.24%（P<0.05）;the soil organic carbon content increased with the increase of the amount of biochar,and the biochar had the most significant increase in the soil organic carbon content in the first year of the radish and hot pepper seasons（P<0.05）.（7）In the radish season,the N2O emission of the vegetable field covered with plastic film was significantly positively correlated with the soil temperature,soil ammonium nitrogen and organic carbon content of 5cm underground（P<0.05）,and the N2O emission of the vegetable field without plastic film covered only correlated with the soil 5cm underground.Temperature and soil ammonium nitrogen content are significantly positively correlated（P<0.01）.In the hot pepper season,all environmental factors had no significant effect on soil N2O emissions（P>0.05）.Soil temperature and carbon and nitrogen content were important factors affecting N2O emissions from vegetable fields in autumn and winter. |
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