Analysis Of Factors Influencing The Effect Of Strong Reducing Soil Treatment

Reductive soil disinfestation(RSD)is a soil disinfestation method that relies on adding a large number of easily decomposed organic materials,irrigating to the maximum field capacity and creating an anaerobic environment through mulching.It has multiple functions such as killing a variety of soil borne pathogens,improving soil physical and chemical properties,and reconstructing soil microflora,etc.,which can effectively alleviate the continuous cropping obstacles caused by high-intensity planting.Therefore,it is of great significance to study the influencing factors of RSD treatment and the relationship between the types of organic materials and the disinfestation efficacy of RSD.The results of this study will benefit-for scientifically selecting of the type and dosage of organic materials,formulating an appropriate RSD treatment scheme and ensuring the best soil remediation effect.In this study,we employ high performance liquid chromatography and real-time quantitative PCR,etc.,to(1)study the main factors that influence the effect of RSD treatment under field conditions through field experiments;(2)decipher the internal relationship between "organic material type-reduction of Eh,accumulation of organic acid-sterilization effect" during RSD treatment by using laboratory culture experiments;(3)determine the inhibition effect of organic acid in different type amd concentration on the mycelial growth of different pathogens by using the growth rate methods.The main results were as follows:Field experiments showed that the degree of soil degradation before RSD treatment had a certain impact on the treatment effect.For soils with low degradation degree,RSD treatment had no significant effect on soil p H and EC,but had a significant effect on the killing effect of Fusarium oxysporum.For severely degraded soils,RSD treatment had significant impact on soil p H,EC,and the populations of soil-borne pathogens.The main factors that affect the effect of RSD treatment on mitigating soil acidification and salinization are the treatment temperature and the type of organic materials used.The main factors of the sterilization effect are the treatment temperature,duration time and the type of organic materials used.Therefore,the type of organic materials is the key factor affecting the RSD treatment effect.Culture experiment showed that the chemical properties of organic materials such as easily oxidized organic carbon(EOC)content and C/N ratio signicantly affected the rate of soil Eh decline,accumulation of soil Eh,the rate of organic acid production,and the accumulation of organic acid during RSD process.The EOC content of organic materials was significantly and negatively correlated with the cumulative amount of soil Eh,while the EOC content of organic materials was significantly and positively correlated with the decrease rate of soil Eh.The C/N ratio was significantly and positively correlated with the cumulative amount of soil Eh,while the C/N ratio was significantly and negatively correlated with the decrease rate of soil Eh.The EOC content of organic materials was significantly and positively correlated with accumulation and production rate of organic acids,while C/N ratio was significantly and negatively correlated with the accumulation and production rate of organic acids.Quantitative PCR analysis showed that the nature of the organic material had a significant impact on the killing efficiency of soil-boren pathogens during RSD process.Organic materials with high EOC content can achieve a high sterilization rate in the early stage of RSD treatment,while organic materials with low EOC content declined the pathogen size slowly in the early stage of RSD treatment,but the sterilization rate gradually increased as the treatment progressed.All RSD treatments can reach a high sterilization rate(99.0%-99.9%)after incubation for 28 days.Correlation analysis showed that during the RSD treatment,the EOC content of organic materials,the decline rate of soil Eh,the production rate and accumulation of organic acid were significantly and positively correlated with the sterilization rate;while the C/N ratio of organic materials was significantly and negatively correlated with the sterilization rate,the cumulative amount of soil Eh was no significantly correlated with the sterilization rate.Therefore,organic materials with high EOC content and low C/N ratio can exhibit a effective disinfestation efficiency in the early stage of RSD treatment through quickly forming a strict anaerobic environment and producing sufficient concentrations of bactericidal substances such as organic acids.Plate experiments showed that organic acids can effectively inhibit the mycelial growth of soil-borne pathogens,and the inhibition effects varied with type and concentration of organic acids.The inhibitory effect of organic acids on soil-borne pathogens was gradually increased with the increment of its concentrations.For example,the inhibition effects of organic acids on the growth of Rhizoctonia solani increased from 30% to 60% when its concentration increased from 1 to 10 mmol/L.At the same time,the inhibitory effect on soil-borne pathogen differed among different type of organic acids.For example,propionic acid,butyric acid,and isovaleric acid with a concentration of 5 mmol/L had an inhibitory effect on R.solani over 90%,while oxalic acid with 5 mmol/L only had an inhibitory effect of 42.55%.In addition,different soil-borne pathogens had different degrees of tolerance to the type and concentration of organic acids.For example,10 mmol/L of organic acid had an inhibitory effect exceeding 55% on the growth of R.solani and F.oxysporum,while its only had about 20% of inhibitory effect on Alternaria alternate and Fusarium solani.In conclusion,the main factors affecting the effect of RSD treatment under field conditions are the degree of soil degradation,treatment duration,temperature and the type of organic materials.Adding organic materials with high EOC content and low C/N ratio can achieve better sterilization effect by improving the generation of toxic organic acids and creating a more severe anaerobic environment during RSD treatment.The inhibition effect of organic acids on mycelial growth of soil-borne pathogens increased with the increase of organic acid concentration,and the inhibition effect of different organic acids on the same pathogen and the inhibition effect of the same organic acid on different pathogens were different.For the degradated soil with specific soil borne pathogens,we can ensure the sterilization effect RSD treatment through regulating the production of bactericidal substances by selecting the appropriate type and amount of organic materials.The results of this study provided a theoretical basis for the scientific selection of organic material,precise processing,and improving the treatment efficiency in the the process of large-scale popularization and application of RSD in the future.