| Atrazine is a triazine herbicide commonly used in the main crop producing areas of Northeast China.Its residue in farmland can cause phytotoxicity to sensitive crops such as soybeans and pose a great threat to food security.In addition,agricultural organic solid waste has long been considered as an important agricultural non-point source pollutant.Whether it can reduce the residue of Atrazine in farmland and realize the utilization of agricultural organic solid wastes is worthy of in-depth research and discussion.In this paper,the effects of inoculating exogenous bacteria on the maturity of cattle manure and corn stalk composting were studied.Based on the above research,a new bio-organic fertilizer with atrazine degradation function was prepared by using cow manure organic fertilizer,Arthrobacter sp.DNS10 and biochar as main materials.Then the in-depth discussion of the above-mentioned new bio-organic fertilizer’s ability and related mechanism to relieve the residual atrazine in black soil on soybean seedlings is expected to provide a theoretical basis and technical support for the simultaneous realization of Atrazine-contaminated farmland soil remediation and the utilization of agricultural organic solid waste.The main research contents and conclusions are summarized as follows:In this paper,the physical and chemical properties and maturity of materials in the process of high temperature composting of cattle manure inoculated with 2%compound bacteria（v/v）were studied.The results show that during the composting process,the water content of the pile gradually decreases.Among the 3rd to 6th weeks,the water content of different areas of the pile decreased by middle layer>upper layer>lower layer.The water content of the inoculum pile was6.86-18.83%more than that of the inoculum pile.During the composting process,the total organic carbon content of the inoculated and uninoculated microbial inoculum pile gradually decreased,and tended to stabilize within the range of 35.00%to 38.00%and 39.00%to 42.00%after 6 weeks.The germination index of the inoculated and uninoculated inoculum piles gradually increased with the composting time,and stabilized at 100%-110%and 90%-100%after the 6th week.The inoculum can prolong the high temperature duration of the compost for 2-3 days,and the upper layer of the reactor body enters the high temperature stage 6 days earlier than the middle and lower layers.Combined with the organic fertilizer safety production standard（NY525-2012）,it was determined that the inoculated and uninoculated inoculum reactors reached maturity at the 6th week.In addition,through the correlation analysis of maturity indicators in this study,it is suggested that GI,C/N,E465/E665,NH4+-N/NO3--N are suitable as auxiliary evaluation indicators for the compost maturity of cattle manure.The degree of humification of dissolved organic matter during different periods of cattle manure composting was studied by UV-visible and fluorescence spectra.The research results show that the UV-visible spectral parameters of dissolved organic matter A226-400nm,A260-280nm,SUVA254 and SUVA280 during the composting process gradually increased from 2.57/2.46,15.94/14.70,0.15/0.15,0.12/0.11 to 8.96/9.10,56.99/57.66,0.50/0.51,0.42/0.43（inoculated/uninoculated）.Based on the fluorescence spectrum integral analysis and parallel factor analysis of the fluorescence spectrum,it was determined that the fluorescence intensity of the component 1 in the dissolved organic matter,which is a protein-like substance,gradually decreased or even disappeared during the high-temperature composting process of cow manure.The fluorescence intensity of component 3 and component 4,which are humus-like substances,increased by 0.87,0.49 times and 2.32,1.78times in the inoculated and uninoculated bacterial agent stacks,respectively.Based on the above results,it is shown that the degree of aromatization and humification of compost materials gradually increases with the degradation of protein-like substances and humus-like substances during the composting process.To investigate the feasibility of removing atrazine from soil and alleviating the stress of atrazine on the growth of soybean by application a novel bio-organic fertilizer developed by agricultural solid wastes,such as cow manure organic fertilizer,biochar and poly-（γ-glutamic acid）,as well as an atrazine-degrading strain Arthrobacter sp.DNS10.The D-optimal mixing experiment design method was used to select and verify the formula with the best removal capacity of atrazine.As a result,the optimal formulation of bio-organic fertilizer（named as DNBF10）was produced by the cow manure organic fertilizer 76.20%,biochar 4.46%,poly-（γ-glutamic acid）8.63%（m/m）and the number of Arthrobacter sp.DNS10 with 0.91×108 CFU·g-1.The new functional bio-organic fertilizer was applied to the contaminated soil with an initial atrazine concentration of 15.26±0.49mg·kg-1 at a dosage of 5 mg·kg-1,and the removal rate of atrazine in the soil could be as high as95.05%after 10 days’application.The pot experiment was used to study the effects of atrazine stress on the growth of soybean seedlings and the effect of the new bio-organic fertilizer on stress relief.The results showed that atrazine stress significantly inhibited the growth and photosynthetic pigment synthesis of soybean seedlings.With the increase of the culture time,the plant and root weights were 50.66%-85.18%and 74.77%-68.28%of the blank treatment respectively,the chlorophyll inhibition rate was49.34%-14.81%.In addition,with the extension of the culture time,the content of malondialdehyde in the leaves was increased by 31.42%-72.33%compared with the blank treatment,proline was accumulated in a large amount,and the SOD activity was significantly increased.However,with the application of new bio-organic fertilizer under atrazine stress,the growth index of soybean seedlings could return to normal levels with the extension of the cultivation time.The chlorophyll content was significantly increased,and 16.19%-25%higher than that of the blank treatment with the extension of the cultivation time.The content of malondialdehyde in leaves gradually decreased to 18.54±4.26μmol·g-1·FW,which was not significantly different from the blank treatment.The content of proline in the leaves decreased by28.34%-11.98%with the extension of the cultivation time,and finally reached the level of blank treatment.The leaf SOD activity was enhanced,which was 1.00 to 1.29 times that under atrazine stress with the extension of the cultivation time.Therefore,combining the above results can show that the application of new bio-organic fertilizer can alleviate the stress of atrazine on the growth of soybean seedlings.Transcriptome technology was used to explore the mechanism of the new bio-organic fertilizer relieving atrazine on soybean seedling growth stress at the molecular level.The results of GO functional enrichment analysis and KEGG pathway enrichment analysis showed that when soybean seedlings were stressed by atrazine(10±0.00 mg·kg-1),the lipid metabolism process,photosynthesis,metabolism of organic hydroxyl compounds Cofactor metabolism is inhibited or destroyed.The new functional bio-organic fertilizer mainly regulates the expression of genes related to plant circadian rhythm,protein folding,classification and degradation,carbohydrate metabolism,secondary metabolism,metabolism and other pathways to alleviate the stress of atrazine on soybean seedling leaves.Based on gene co-expression network analysis,9 gene transcription factors from the C2H2,MYB,FAR1,GRAS,and m TERF transcription families were identified as core regulatory centers in response to the application of new functional bio-organic fertilizers under atrazine stress.The new functional bio-organic fertilizer can alleviate the growth stress of Atrazine on soybean seedlings and its up-regulated expression of gene transcription factors regulating the above five transcription families. |
