| Biochar is a kind of carbon-rich multi-functional material produced by pyrolysis of biomass at high temperature（>300 C）under anoxic conditions,which has high porosity,large specific surface area and strong stability.Its potential in soil fertility conservation,texture improvement and pollution remediation has been widely concerned.At present,there is no unified conclusion about the soil ecological regulation function of biochar.Exploring the agronomic effect and ecological response characteristics of biochar soil input and revealing its potential function and regulation mechanism systematically are of positive significance for the rational use of biochar in agriculture.In this study,soil culture,q PCR detection and PLFAs analysis were used to observe the change characteristics of Caenorhabditis elegans,fungal bacterial communities and the infection of tomato wilt under the conditions of adding different raw materials of biochar and modified biochar,and to explore its possible mechanism.The main results are as follows:（1）Biochar input significantly increased soil p H value,electrical conductivity（EC）and ammonium nitrogen content,and decreased nitrate nitrogen concentration.Compared with CK（p H7.79）,p H increased to 7.87-8.35,conductivity increased by 1.17%-65.79%,and the effect was MBC > PBC > BBC > ABC.The content of ammonium nitrogen increased by 12.74%-159.2% and nitrate nitrogen decreased by 68.83%-78.02%.Compared with unmodified biochar,the application of oxidized biochar（HPBC）and nitrogen-loaded biochar（NPBC）significantly increased soil organic matter content by 5.8%-94.5% and 8.9%-82.2%,respectively.Among them,the total nitrogen content of the soil added with NPBC increased by 0.04-0.34 g·kg-1,nitrate nitrogen and ammonium nitrogen content.Increase in the amount of water increased by 11.28-27.72 g·kg-1 and 0.26-1.53 g·kg-1,respectively.（2）The application of PBC,MBC and ABC could promote the total microbial biomass and bacterial biomass in soil,but the increase rate decreased with the increase of biochar concentration,while the addition of BBC could significantly reduce the total microbial biomass and bacterial biomass in soil;PBC,MBC,ABC and BBC could significantly promote the fungal-bacterial ratio in soil;appropriate addition of biochar(20.0,40.0,80.0 g·kg-1)It can promote the reproduction of fungi,but the addition of PBC and BBC in large quantities(160 g·kg-1)can significantly inhibit the growth of fungi.After the application of biochar,the changes of soil acidity and alkalinity,soil conductivity and other indicators caused by biochar are the main factors leading to the changes of soil bacterial fungi community.Proper application of ABC and PBC is more conducive to the development of soil bacterial fungi community structure than that of BBC and MBC.（3）Biochar significantly inhibited the growth and reproduction of nematodes.Compared with the environment without biochar,the length of nematodes decreased by 8.7%-28.0%,and the number of offspring decreased by 19.1%-41.21%.The inhibition effect was ABC > BBC > MBC > PBC.However,the four biochars had no severe oxidative toxicity to nematodes.The volatile substances or odors contained in the four biochars could stimulate the olfaction of nematodes,and nematodes had a certain tendency towards them.The number of differentially expressed genes and specific genes in nematodes treated with PBC were lower than those treated with ABC,BBC and MBC.The effects of ABC,BBC and MBC treatments on differentially expressed genes of nematodes were basically the same,including cell metabolism,primary metabolism,nitrogen metabolism,biochemical synthesis of cell components,and cyclic metabolism of organic matter.PBC treatment affected the biosynthesis and metabolism of polypeptides,nitrogen and organic nitrides,amide compounds and metabolic functions of differentially expressed genes in nematodes.The metabolic response pathways of differentially expressed genes in all biocharcoal-treated nematodes were the same.The expression of perm,col,vit,rpl,rps and other family genes were significantly affected.The difference of gene expression was the fundamental reason for the phenotypic changes of nematodes.（4）The addition of biochar to soil had a significant inhibitory effect on the infection of Tomato Seedlings by Rhizoctonia solani.Compared with no treatment,it delayed the onset time of Tomato Seedlings by 1-3 days,reduced the disease index（AUMPC）of the infected tomato seedlings,and reduced the infection rate of Rhizoctonia solani to tomato seedlings.The application of biochar with low amount(20,40 g·kg-1)was better than that with high amount(80,160 g·kg-1)treatment.Modified and unmodified biochar had the best control effect on Tomato Seedling Blight at the application rate of 20 g·kg-1.The effects of HPBC and NPBC are due to PBC. |
