The Influence Of Residue Mixing On The Degradation Of Tomato Root Residues

Degradation of residue plays an important role in terrestrial ecosystems,and the composition and diversity of residue will affect the degradation rate of residue.Tomato(Solanum lycopersicum)is one of the important facility vegetables,but soil sickness severely restricts the sustainable production of facility tomato.The autotoxicity caused by the accumulation of crop residues is one of the important factors for soil sickness.Intercropping,crop rotation,and cover cropping can effectively relieve soil sickness,while also changing the underground diversity and composition.This change may have an impact on the degradation rate of the residue.Increasing the degradation rate of tomato root residue can reduce the accumulation of autotoxicity,thereby relieving soil sickness of tomato in facility.However,the effect of residue mixing in agro-ecosystems on residue degradation rate and degrading microbial flora is still unclear.In this experiment,five kinds of residues that can be put into the soil that can relieve soil sickness in production are selected.Tomato root residue is used as the test material,and 4 kinds of diversity are set for mixing residues to degradation.The effect of residue mixing on the degradation rate of tomato root residue is analyzed.Quantitative PCR and high-throughput sequencing are used to analyze the changes of the microbial community in the tomato root resiude and the influencing factors,which provide a theoretical basis for relieving soil sickness of tomato and maintaining the sustainable development of the facility soil.The main results obtained are as follows:(1)When the 6 residues were degraded according to different diversity for 15 d and 90 d,the residue degradation rate and residue nitrogen content were positively correlated with diversity,and the residue degradation rate and nitrogen content also showed a positive correlation,indicating that the degradation rate of residue is significantly affected by the diversity of residues,incubation time and nitrogen content.After the tomato root residue was mixed and degraded with the other 5residues,the degradation rate increased during the three sampling periods,and the diversity was positively related to the degradation rate.Residue diversity and degradation rate are positively correlated with tomato root residue nitrogen content at 45 d and 90 d sampling,but there is no significant correlation between tomato root residue phosphorus content and degradation rate,indicating that the increase in tomato root residue degradation rate is related to the increasing content of nitrogen.The incubation time of the residue,the existence of the residue species and the interaction of influencing factors also have a significant impact on the increase of the degradation rate of tomato root residue.(2)Analysis of q PCR showed that when the residue was degraded at 15 and 45 d,the mixed residues with diversity of 4 and 6 increased the abundance of bacterial communities in tomato root residue with diversity of 1 and 2,while the residue was degraded at 90 d,residue diversity had no significant effect on the bacterial community abundance of tomato root residue.The degradation rate of tomato root residue was positively correlated with the abundance of bacterial community in all sampling periods.However,the fungal community abundance in tomato root residue was only negatively correlated with diversity when it was degraded for 90 days,but there was no significant correlation with the degradation rate.(3)High-throughput sequencing analysis showed that the Shannon index of the bacterial community in the tomato root residue was positively correlated with diversity,and the alpha diversity index of the fungal community was also positively correlated with diversity,and the diversity of 6 in residue mixtures increased the α diversity index of the microbial community of single tomato root residue.The content of nitrogen and phosphorus in tomato root residue was negatively correlated with the alpha diversity index of the bacterial community,and the phosphorus content was positively correlated with the number of OTU of the fungal community.The residue incubation time,diversity,existence of special residues and the interaction of the above factors significantly changed the microbial community structure of tomato root residue.There was no significant difference in the fungal community structure of tomato root residue with diversity of 4 and 6 when the residue was degraded at 45 d and 90 d,while there were significant differences in the fungal community structure of tomato root residue at other diversity levels.The nitrogen and phosphorus content of tomato root residue is also positively correlated with the structure of microbial community.Random forest analysis showed that the β diversity and abundance of bacterial and fungal communities in tomato root residue are important indicators to predict the degradation rate of tomato root stubble,and the increase in relative abundance of OTUs is also a potential factor affecting the change of tomato root residue decomposing rate.The OTUs which were related with the degradation rate of tomato root residue mainly belonged to the Proteobacteria and Ascomycota,and the relative abundance of Firmicutes,Actinomycetes and Bacteroides increased with decomposing.(4)The results of pot experiments showed that the increase of residue diversity would increase the aboveground,underground and whole plant dry weight of tomato seedlings,and the degradation rate of residue was positively correlated with dry weight of tomato seedling and the residue treatment with a diversity of 6 promoted the growth of tomato seedlings.In summary,incubation time,residue diversity and composition are important factors affecting the degradation rate of tomato root residue,and the β diversity,abundance and composition of the microbial community of tomato root residue are important factors which might affect the degradation rate as potential microbial indicators.Increasing the diversity of residues can increase the nitrogen content and bacterial community abundance of tomato root residue,change the structure and composition of microbial community,thereby promoting the degradation of tomato root residue;and the increase of phosphorus content in tomato root residue can increase the number of fungal community OTU,indirectly affect the degradation of tomato root residue.The rapid degradation of tomato root residue is one of the reasons for the accelerated growth of tomato seedlings.