Study On Heating Regularity And Microbial Community Change Characteristics Of North China Tidal Soil And Northeast China Black Soil Based On Microwave Irradiation

Continuous or monoculture cultivation tends to over-consume arable land,resulting in imbalance of soil nutrient content and slabbing.Long-term accumulation of various pathogens often leads to large outbreaks of soil-borne diseases,which can reduce crop yields and even destroy seeds.Based on the above problems,soil disinfection as an important agronomic initiative can effectively prevent and control soil-borne disease,insect and weed outbreaks,solve the problem of heavy crops of high value-added crops,and improve the quality and yield of crops while improving the soil environment.Compared to traditional chemical soil disinfection methods,microwave has the great advantage of no pollution,no residue,green and environmental protection after application.Compared with other physical soil disinfection methods,microwave application process reflects the unique"penetration",similar to the chemical fumigation,can make the internal temperature of the soil rapidly,soil temperature is an important condition for the inactivation of pathogenic bacteria and harmful organisms;where the soil physical and chemical properties and changes in soil microbial community is the microwave soil disinfection results The soil temperature is an important condition for the inactivation of pathogenic bacteria and harmful organisms.To address these issues,this paper investigates the optimal operating conditions for microwave soil disinfection in north China tidal soils and northeastern black soils,and the main contents and conclusions are as follows:（1）A 2.45 GHz soil microwave irradiation test system was designed,equipped with self-designed multi-point soil internal temperature testing system.The combination of modeling simulation and experimental verification was used to construct a soil electromagnetic field interaction model under microwave irradiation and to confirm the validity of the microwave generation system and soil simulation model.The microwave output power,irradiation time and soil moisture content were investigated to determine the effect of microwave output power,irradiation time and soil moisture content on the soil temperature distribution pattern.The results show that as the soil moisture content increases the electric field strength value inside the soil at the same depth decreases and the wave frequency increases;penetrating the soil model microwave outgoing field strength size is three orders of magnitude lower than the incident field strength.Low output power microwave loss in lossy media is greater,so 2KW microwave output power is more suitable for soil disinfection.The highest temperature after microwave irradiation occurs at the soil surface not inside the soil,but the soil surface temperature is often plummeted by the external environment.The soil moisture content increases so that the location of the maximum temperature value inside the soil after microwave irradiation is getting closer to the soil surface.The greater the field strength inside the soil,the higher the temperature value tends to be,and the maximum temperature inside the microwave irradiated soil tends to appear at the first peak of the microwave.（2）The heat production patterns of north China tidal soils and northeast black soils under microwave action were revealed and compared.Based on the above study,the microwave soil irradiation system with 2KW microwave output power was selected as the condition to simulate the temperature field for the soil model.Microwave irradiation tests were conducted for 1～12 min for north China tidal soils and northeast black soils in the range of 10%～23%natural water content,respectively.The results show that soil moisture content,irradiation time,and soil type are the main factors affecting the microwave soil heat production law.The surface temperature of the soil had a positive correlation with the moisture content,and the maximum surface temperature of the black soil was higher than that of the tidal soil.The average internal temperature?T_αin the microwave irradiated area varied with soil water content as follows:?Tα15%>?Tα20%>?Tα10%>?Tα23%（tidal soil）;Tα10%>?Tα15%>?Tα20%>?Tα_23%;T_{αBlack soil}>?T_{αmoist soil}（black soil）;the average internal temperature of black soil was higher in the same test conditions.To further investigate the relationship between internal soil temperature and microwave time,soil moisture content and soil depth,the"irradiation time-soil moisture content"microwave effective irradiation area average temperature model and"irradiation time-soil depth"average temperature model were constructed for the tidal soils in North China and the black soils in Northeast China,respectively.The"irradiation time-soil water content"average temperature model and"irradiation time-soil depth"average temperature model were constructed for the tidal soils in North China and the black soils in Northeast China.The optimum soil moisture content of 14.63%（tidal soils）and 10%（black soils）was determined for the highest soil temperature conditions in the tidal soils of North China and the black soils of Northeast China,which provided data to support the optimum soil conditions for microwave soil disinfection applications.（3）To investigate the effect of microwave on the physicochemical properties and soil microbial community of North China tidal soils,and to determine a more suitable microwave soil disinfection for North China tidal soils in the 3min period.Soil physicochemical properties and soil microbial community changes are an important reflection of the results of microwave action.Based on the water content condition（14.63%）where the optimal heat production law of microwave North China tide soil is located,the soil was irradiated for 3,6,9 and 12 min,and the soil samples were tested for physicochemical properties and soil microbial high-throughput sequencing after 30 days of incubation in the greenhouse.The results showed that microwave treatment had significant effects on soil p H,TN,C/N,AP,NO₃^--N and NH₄⁺-N.Microwave treatment had significant effects on soil microbial community richness and species number;irradiation duration was an important factor affecting microbial community richness.The relative abundance of Fictibacillus and Bacillus increased with microwave irradiation time;for soil fungi,the relative abundance of Aspergillus,Alternaria,Cladosporium,Acremonium,Penicillium and Coprinellus increased after microwave The relative abundance of Aspergillus,Alternaria,Cladosporium,Acremonium,Penicillium,and Coprinellus increased after microwave treatment.The relative abundance of the saprophytic nutritional fungi Undefined Saprotroph increased with the increase of microwave irradiation time.The pathotrophic fungi Plant Pathogen decreased in the microwave treatment at 3,6 and 12 min compared to the control,and the microwave treatment at specific times helped to eliminate some of the harmful bacteria in the soil that damaged the host cell types.Soil microbial communities were driven by p H,C/N,NO₃^--N,NH₄⁺-N,AP,SOC,TN soil physicochemical properties.Soil NH₄⁺-N,NO₃^--N and AP are important factors affecting the diversity of soil microbial communities.（4）The effect of microwave irradiation on the physicochemical properties and soil microbial community of northeastern black soil was investigated using the same experimental methods as those for northern China tidal soils.Based on the investigation of microwave heat production in northeastern black soils,a 10%water content soil was selected for the test under the best heat production conditions,and a 6-min period was determined to be more suitable for microwave soil disinfection in north China tidal soils.Microwave treatment showed faster recovery of beneficial soil microorganisms despite altering the soil microbial community.Microwave treatment increased soil p H,NO₃^--N,NH₄⁺-N and AP content.Soil physicochemical properties p H,C/N and SOC were important factors affecting microbial community diversity;soil microbial communities were driven by soil p H,C/N,NO₃^--N,AP,and SOC.Soil Shannon index,Chao index,respectively,and Ace index showed a decreasing trend with increasing microwave irradiation duration.Fungal functional prediction analysis revealed that the relative abundance of saprophytic nutritional fungi such as Undefined Saprotroph had a significant increase in all microwave irradiation periods compared to the control group;Plant Pathogen had a significant decrease in relative abundance compared to the control group.