Study On N₂O Emission Characteristics And Source Mechanism Of Soils Exposed To Fermented Pig Slurry

The application of fermented pig slurrys in FPSmland is a common and economically feasible method for pollutant treatment and resource utilization.However,there are many risks of environmental pollution in the application process,and its research hotspot is the emission of N₂O.Therefore,it's necessary to understand its role in affecting N₂O emissions,especially the source and mechanism of post-application N₂O emissions.It was used to reveal the effects of different drying methods on the chemical properties of fermented pig slurrys,carried out experiments on the effects of vacuum freeze drying,air drying and hot air drying on the chemical properties and substrate content of fermented pig slurrys.Secondly,three kinds of fermented pig slurrys levels(0 g·kg^-1,10 g·kg^-1,25 g·kg^-1 dry soil)and three water content gradient?50%,75%,100%WHC?,random block design,a total of nine processing were set up to investigate the soil N₂O emission characteristics and chemical properties of soil fermented pig slurrys application.The characteristics of soil N₂O emission under a certain period of time were studied using the indoor culture greenhouse gas collection method with typical texture soil.As fermented pig slurrys were increasingly being applied to fermented pig slurrys mland,which required understanding their role in influencing N₂O emissions,particularly in terms of the sources and mechanisms of post-application N₂O emissions.The ¹⁵N-labeled sulfate was used to modify the soil to distinguish the sources of N₂O and the different pathways of nitrification and denitrification.Based on the above studies to establish a more reasonable application strategy to meet the production needs,reduce the impact of fermented pig slurrys on the environment,and ease the N₂O emissions in agricultural soil.The main conclusions were as follows:?1?The results showed that vacuum freeze drying had the least loss of the chemical components than the other two methods,which indicated that the vacuum freeze drying process could maintain high physical and chemical properties.In this study,the effects of different pre-freezing time on the chemical properties of fermented pig slurrys were also analyzed.There is no significant difference to the characterizations of fermented pig slurrys between 3 hours and6 hours of freeze-drying.Thus,freeze drying for 3 hours was suggested as the best pretreatment because of easy operation,short time,convenient and easy to operate,and it is recommended as a treatment pretreatment method selected for agricultural production and scientific research.At the same time,applications in production or research should also consider cost and research objectives.?2?Both fermented pig slurry and moistures and their interactions had significant effects on soil N₂O fluxes,so the application of fermented pig slurry was minimized while satisfying production requirements,thereby reducing the N₂O emission of soil.In addition,the application of fermented pig slurrys will significantly promote the short-term emissions of N₂O.During the incubation period,these N₂O emissions initially exhibited an increasing trend,and subsequently decreased,and the application of fermented pig slurrys did not change this trend.The characteristics of soil N₂O emissions from different moisture were 75%WHC>50%WHC>100%WHC.The production of N₂O in soil is a complex and changeable process,which was positively correlated with moisture,DOC content and NH₄⁺-N content.At the same time,the contents of ammonium nitrogen and DOC in soil decreased gradually,which was significantly positively correlated with the N₂O emission flux?p<0.05?.Nitrate nitrogen content increased gradually,and the CO₂ flux of soil increased first and then decreased.However,more research is required on the combined effects of fermented pig slurrys in agricultural production on environmental and climate change,in order to further understand this and developing strategies that could effectively mitigate greenhouse gas emissions,while meeting production needs.At the same time,the moisture also affects the N₂O emission of soil.Therefore,in the actual production and application,the supply of moisture must be strictly controlled so as to meet both the production needs and the emission of greenhouse gases.Based on the comprehensive test results,it is preliminarily concluded that the application amount of fermented pig slurry is 10 g·kg^-1 and the moisture is 50%WHC,which is a favorable condition for controlling soil N₂O emission.?3?Soil nitrogen sources were the sole source of N₂O emissions from soils that have not been treated with fermented pig slurrys.The fermented pig slurrys nitrogen sources were the main source of N₂O production from treated soils.The application of fermented pig slurry significantly reduced the contribution of soil nitrogen to N₂O production,but the cumulative N₂O emissions from soil contribution increased with the increase in the application of fermented pig slurry.In addition,the application of fermented pig slurry promotes the soil nitrification and denitrification,but the dominant role of N₂O in the three moistures was still nitrification.In addition,the combined effects of the amount of fermented pig slurry and the moisture also stimulated the use of soil nitrogen source.Therefore,a more rational application strategy can be established to reduce the impact of fermented pig slurry on the environment and reduce N₂O emissions from agricultural soils while meeting the needs of agricultural production.