Preparation method of saline-alkali soil remediation agent

Abstract

The invention belongs to the technical field of soil remediation, and provides a preparation method of a saline-alkali soil remediation agent aiming at the problem of insufficient long-acting stability caused by uncontrollable Ca < 2 + > release of an existing saline-alkali soil remediation agent. The method comprises the following steps: by taking alfalfa residues as raw materials, fermenting to generate acidic fermentation liquor, dissolving soil carbonate, reducing pH, triggering coordinate bond dissociation of chelated calcium gel, realizing pH responsiveness of releasing Ca < 2 + >, and releasing Ca < 2 + > to replace Na < + >; meanwhile, quinonyl on the surface of the modified biochar is used for activating extracellular electron transfer of the Prussella adamsii, and hydroxyl ion secretion is promoted to neutralize salt groups; the alfalfa humification fermentation material and exopolysaccharides secreted by flora are crosslinked through hydrogen bonds to form a cementation layer, soil aggregates are stabilized through a modified charcoal pore framework, calcium slow release balance is regulated and controlled, the problem of local hardening caused by sudden release of Ca < 2 + > is cooperatively solved, and long-acting repair and improvement of the saline-alkali soil are achieved.

Description

Technical Field

[0001] The present application relates to the technical field of soil remediation, and in particular to a method for preparing a saline-alkali soil remediation agent. Background Art

[0002] Soil remediation and improvement technology for saline-alkali land is a current research hotspot in the fields of agriculture and environment. Its core goal is to achieve sustainable land use by reducing soil salinity, improving structure, and increasing fertility. Traditional technologies mainly rely on physical improvement (such as irrigation to wash salt, underground pipe salt drainage), chemical conditioning (such as gypsum, organic acid, etc.) and biological remediation (such as salt-tolerant plants, microbial agents). However, a single technology often has limitations and is insufficient to meet the needs of soil improvement. The Chinese patent application with publication number CN118459281A discloses a saline-alkali soil conditioner, which contains organic fertilizer, crop straw, straw biochar, humic acid and microbial agents, which are prepared through two fermentation processes and equipped with underground pipe salt drainage, deep loosening and film covering planting methods. The invention uses organic materials to improve soil fertility, biochar to enhance adsorption and slow release capacity, humic acid to promote aggregate formation, microbial agents to activate nutrients, and engineering measures to strengthen desalination. Salt reduction and fertility improvement are achieved through multi-component composite. However, the conditioner lacks Ca 2+ The release rate regulation of Ca 2+ The concentrated release of oxygen causes soil compaction. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the present application provides a method for preparing a saline-alkali soil remediation agent. Using alfalfa residue as raw material, fermentation generates acidic fermentation liquid, dissolves soil carbonate and lowers pH, triggers the coordination bond dissociation of chelated calcium gel, and realizes Ca 2+ pH-responsive, Ca release 2+ To replace Na + At the same time, the quinone groups on the surface of modified biochar were used to activate the extracellular electron transfer of Priestia aryabhattai, promoting the secretion of hydroxyl ions to neutralize the salt base; the extracellular polysaccharides secreted by alfalfa humification fermentation material and the bacterial community were cross-linked through hydrogen bonds to form a cementing layer, relying on the porous skeleton of modified biochar to stabilize soil aggregates and regulate the calcium slow-release balance, synergistically solving the problem of Ca 2+ The problem of local compaction caused by sudden release has been solved, achieving long-term restoration and improvement of saline-alkali land.

[0004] To achieve the above objectives, this application adopts the following technical solutions:

[0005] The present application provides a method for preparing a saline-alkali soil remediation agent, comprising the following steps:

[0006] S1. Grinding alfalfa residue and mixing it with an inorganic acid to obtain an acid mixture, and fermenting it with Aspergillus niger to obtain an acidic fermentation liquid;

[0007] S2. adjusting the pH of the acidic fermentation broth to neutral, adding a nitrogen source, and aerobically fermenting the broth with Bacillus subtilis to obtain an alfalfa humification fermentation material;

[0008] S3, mixing the acidic fermentation liquid with industrial by-product gypsum to obtain a chelated calcium gel;

[0009] S4, producing biochar by oxygen-limited pyrolysis of biomass, and impregnating and modifying the biochar by alfalfa humification fermentation material to obtain modified biochar;

[0010] S5. reconstitute the lyophilized powder of Priestia aryabhattai into a bacterial agent;

[0011] S6. Mixing the alfalfa humification fermentation material, chelated calcium gel, modified biochar, bacterial agent and adhesive to form granules to obtain the saline-alkali land soil remediation agent.

[0012] Beneficial technical effects:

[0013] After the saline-alkali soil remediation agent of the present invention is mixed into the saline-alkali land, the organic acid in the acidic fermentation liquid generated by fermentation of alfalfa residues quickly dissolves soil carbonate and lowers the pH, triggering the chelated calcium gel to react with humic acid and Ca 2+ Coordinate bonds dynamically dissociate, releasing Ca 2+ Replacement of Na + At the same time, the quinone groups added to the modified biochar surface activated the extracellular electron transfer of Priestia aryabhattai, promoting OH - Secretion, binding Na + In the later stage of restoration, the alfalfa humification fermentation material and the extracellular polysaccharides secreted by the bacterial community form a cementing layer through hydrogen bond cross-linking, which stabilizes the aggregates and maintains the calcium slow-release balance, avoiding Ca 2+ The sudden release of cementation caused by the organic acid of alfalfa humification fermentation material initiates desalination, the pH responsiveness of the chelated calcium gel maintains calcium supply, the electron transfer of the modified biochar activates the metabolism of the bacterial community, and the bacterial metabolites complete the construction of the cementation network, forming a synergistic mechanism. 2+ Under the premise of slow release, a high-efficiency and long-term saline-alkali soil remediation and improvement effect is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the preparation method of the saline-alkali soil remediation agent of the present invention. DETAILED DESCRIPTION

[0015] In order to make the technical problems, technical solutions, and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below with reference to the following examples. However, this should not be construed as limiting the scope of this application to the following examples. Without departing from the above-mentioned method concepts of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0016] In this application, the terms used in this application are for the purpose of describing specific embodiments only and are not intended to be limiting of the application.

[0017] As used in this application, the singular forms "for," "or," "an," "any," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0018] In addition, the terms “first” and “second”, if used, are only used for descriptive purposes and should not be understood as indicating or implying relative importance.

[0019] The lyophilized powder of Priestia aryabhattai used in the present invention was purchased from Wuhan Huizao Biotechnology Co., Ltd. with the product number HZB139387; Aspergillus niger was purchased from Ningbo Mingzhou Biotechnology Co., Ltd. with the product number BMZ135481; and Bacillus subtilis was purchased from Ningbo Mingzhou Biotechnology Co., Ltd. with the product number BMZ135815.

[0020] The present application provides a method for preparing a saline-alkali soil remediation agent, comprising the following steps:

[0021] S1. Grinding alfalfa residue and mixing it with an inorganic acid to obtain an acid mixture, and fermenting it with Aspergillus niger to obtain an acidic fermentation liquid;

[0022] S2. adjusting the pH of the acidic fermentation broth to neutral, adding a nitrogen source, and aerobically fermenting the broth with Bacillus subtilis to obtain an alfalfa humification fermentation material;

[0023] S3, mixing the acidic fermentation liquid with industrial by-product gypsum to obtain a chelated calcium gel;

[0024] S4, producing biochar by oxygen-limited pyrolysis of biomass, and impregnating and modifying the biochar by alfalfa humification fermentation material to obtain modified biochar;

[0025] S5. reconstitute the lyophilized powder of Priestia aryabhattai into a bacterial agent;

[0026] S6. Mixing the alfalfa humification fermentation material, chelated calcium gel, modified biochar, bacterial agent and adhesive to form granules to obtain the saline-alkali land soil remediation agent.

[0027] In a feasible implementation scenario, the alfalfa residue is alfalfa stem and leaf portion with a moisture content of ≤15%; and the particle size of the alfalfa residue after pulverization is ≤3.0 mm.

[0028] In a feasible implementation scenario, the inorganic acid is one of sulfuric acid, hydrochloric acid and phosphoric acid; and the mass ratio of the alfalfa residue to the inorganic acid is 1:(2-4).

[0029] In a feasible implementation scenario, the inoculum amount of Aspergillus niger is: the concentration of Aspergillus niger in the acid mixture is 3×10 5 -5×10 5 CFU / mL, the inoculum amount of Bacillus subtilis is: the concentration of Bacillus subtilis in the acidic fermentation broth is 2×10 6 -3×10 6 CFU / mL.

[0030] After alfalfa residues are crushed and mixed with inorganic acids, they are fermented by Aspergillus niger to produce organic acids such as oxalic acid and citric acid. The inorganic acids provide an initial acidic environment, promoting the decomposition of alfalfa fiber; Aspergillus niger secretes cellulase and organic acids to further degrade organic matter, forming an acidic fermentation liquid rich in organic acids, which provides acidic conditions for subsequent steps, dissolving soil carbonates and lowering pH, triggering Ca 2+ release.

[0031] In a feasible implementation, the nitrogen source is one of urea, ammonium sulfate and ammonium carbonate, and the added amount of the nitrogen source is 0.5%-1.0% of the mass of the acidic fermentation broth.

[0032] After the acidic fermentation broth is neutralized with calcium hydroxide, a nitrogen source is added and Bacillus subtilis is inoculated for aerobic fermentation. Bacillus subtilis uses the nitrogen source and residual organic matter to produce humic acid, while stabilizing the organic matter through oxidation. Humic acid has chelating ability and colloidal properties, which provides a basis for subsequent Ca 2+It provides a basis for chelation and soil aggregate formation. At the same time, the π-π stacking effect between the aromatic ring of lignin contained in alfalfa residue and humic acid enhances the stability of alfalfa humification fermentation material.

[0033] In a feasible implementation scenario, the solid-liquid mass ratio of the acidic fermentation liquid to the industrial by-product gypsum is (2-4):1; the industrial by-product gypsum is one of phosphogypsum, desulfurized gypsum and citric acid gypsum.

[0034] Humic acid in the acidic fermentation broth reacts with industrial by-product gypsum, and the carboxyl and phenolic hydroxyl groups of humic acid react with Ca 2+ Dynamic coordination bonds are formed to generate pH-responsive chelated calcium gel. When the soil pH decreases, the coordination bonds dissociate and Ca is preferentially released. 2+ Replacement of Na + , to regulate Ca 2+ The effect of release rate can avoid local hardening and achieve efficient sodium-calcium replacement.

[0035] In a feasible implementation scenario, the biomass is one of rice husks, straw and sawdust; and the mass ratio of the biochar to the alfalfa humification fermentation material is 1:(4-6).

[0036] Biomass is pyrolyzed at high temperature under oxygen-limited conditions to generate porous biochar, which is then impregnated with alfalfa humification fermentation material. Humic acid is loaded on the surface of the biochar through physical adsorption and chemical bonding, introducing active groups such as quinone groups (C=O). The quinone groups are redox active and act as electron acceptors, activating the extracellular electron transfer of Priestia aryabhattai and promoting OH - Secretion, binding Na + Forming washable NaOH; at the same time providing a habitat for bacteria.

[0037] In a feasible implementation scenario, the viable cell count of the freeze-dried powder of Priestia aryabhattai is ≥1×10 10 CFU / g, the mass ratio of the lyophilized powder of Priestia aryabhattai to deionized water during reconstitution is 1:(50000-100000).

[0038] After reconstitution, the freeze-dried powder of Priestia aryabhattai recovers its metabolic activity, secretes extracellular polysaccharides and enzymes, degrades organic matter and regulates salt conversion. Priestia aryabhattai transfers the electrons generated by metabolism (such as electrons from the oxidation of organic substrates) to the quinone group of modified biochar through cytochrome c protein or nanowires on the cell membrane, completing extracellular electron transfer; the extracellular electron transfer process accelerates the energy metabolism of the bacteria, promotes the efflux of intracellular protons to maintain charge balance, and leads to extracellular OH - At the same time, the bacteria oxidize humic acid to generate CO2 and H2O through the action of dehydrogenase and oxidase, further releasing OH - OH - Na adsorbed in soil + The combination generates soluble NaOH, which is washed out of the soil through irrigation or precipitation, significantly reducing the salt content. In alfalfa humification fermentation feed, the phenolic hydroxyl groups of humic acid form intermolecular hydrogen bonds with the hydroxyl and carboxyl groups in the extracellular polysaccharides, cross-linking to form a cementing layer, binding the loose particles into water-stable aggregates.

[0039] In a feasible implementation, the binder is one of carboxymethyl cellulose and bentonite.

[0040] In a feasible implementation scenario, the mass ratio of the alfalfa humification fermentation material, the chelated calcium gel, the modified biochar, the bacterial agent and the adhesive is (50-60):(25-35):(8-12):(3-7):(2-5).

[0041] The following will describe in detail a method for preparing a saline-alkali soil remediation agent provided by the present application in combination with different embodiments.

[0042] Example 1:

[0043] like Figure 1 As shown, a method for preparing a saline-alkali soil remediation agent comprises the following steps:

[0044] 1. The harvested alfalfa stems and leaves were naturally air-dried to a moisture content of ≤15% to obtain alfalfa residue. The alfalfa residue was crushed to a particle size of ≤3 mm, mixed with 0.3 mol / L sulfuric acid at a mass ratio of 1:4, and stirred at 40°C for 2 h to obtain an acid mixture. After cooling, the mixture was inoculated with Aspergillus niger to a concentration of 3×10 5 CFU / mL, and fermented in a sealed container at 40°C for 48 h, stirring at 30 rpm for 10 min every 6 h to obtain an acidic fermentation broth;

[0045] 2. The pH of the acidic fermentation broth was adjusted to neutral with calcium hydroxide, and ammonium carbonate (0.5% by mass of the acidic fermentation broth) was added. Bacillus subtilis was inoculated to a concentration of 3×10 6 CFU / mL, and aerobically fermented at 50℃ for 5 days to obtain alfalfa humification fermentation material;

[0046] 3. The acidic fermentation broth was mixed with phosphogypsum in a mass ratio of 3:1, stirred at 60°C for 4 hours, and crushed and sieved to obtain a chelated calcium gel with a particle size of less than 4 mm;

[0047] 4. The biochar was obtained by pyrolyzing rice husks at 600°C for 2 hours in an oxygen-limited atmosphere (a mixture of oxygen and nitrogen at a volume ratio of 1:19). The biochar was then immersed in alfalfa humification fermentation feed at a solid-liquid ratio of 1:4, ultrasonically treated for 1 hour, and then dried to obtain the modified biochar.

[0048] 5. Set the viable count to ≥1×10 10 The lyophilized powder of Priestia aryabhattai at 100 CFU / g was reconstituted with deionized water to obtain a bacterial agent, wherein the mass ratio of the lyophilized powder to the water was 1:50000;

[0049] 6. The alfalfa humified fermentation material, chelated calcium gel, modified biochar, bacterial agent and carboxymethyl cellulose were mixed in a mass ratio of 50:35:8:3:2 to obtain a blend, and granulated to obtain the saline-alkali soil remediation agent.

[0050] Example 2:

[0051] like Figure 1 As shown, a method for preparing a saline-alkali soil remediation agent comprises the following steps:

[0052] 1. The harvested alfalfa stems and leaves were naturally air-dried to a moisture content of ≤15% to obtain alfalfa residue. The alfalfa residue was crushed to a particle size of ≤3 mm, mixed with 0.3 mol / L hydrochloric acid at a mass ratio of 1:2, and stirred at 40°C for 2 h to obtain an acid mixture. After cooling, the mixture was inoculated with Aspergillus niger to a concentration of 5×10 5 CFU / mL, with an inoculum size of 5%, the mixture was sealed and fermented at 40°C for 48 h, with stirring at 30 rpm for 10 min every 6 h to obtain an acidic fermentation broth;

[0053] 2. The pH of the acidic fermentation broth was adjusted to neutral with calcium hydroxide, and ammonium sulfate (1.0% by weight of the acidic fermentation broth) was added. Bacillus subtilis was inoculated to a concentration of 2×10 6 CFU / mL, and aerobically fermented at 50℃ for 5 days to obtain alfalfa humification fermentation material;

[0054] 3. The acidic fermentation broth and desulfurized gypsum were mixed in a mass ratio of 4:1, stirred at 60°C for 4 hours, and crushed and sieved to obtain a chelated calcium gel with a particle size of less than 4 mm;

[0055] 4. The straw was pyrolyzed at 600°C for 2 hours in an oxygen-limited atmosphere (a mixture of oxygen and nitrogen at a volume ratio of 1:19). The biochar was then immersed in alfalfa humification fermentation feed at a solid-liquid ratio of 1:5, ultrasonically treated for 1 hour, and then dried to obtain the modified biochar.

[0056] 5. Set the viable count to ≥1×10 10 The lyophilized powder of Priestia aryabhattai at 100 CFU / g was reconstituted with deionized water to obtain a bacterial agent, wherein the mass ratio of the lyophilized powder to the water was 1:80000;

[0057] 6. The alfalfa humified fermentation material, chelated calcium gel, modified biochar, bacterial agent and bentonite were mixed in a mass ratio of 55:30:10:5:3 to obtain a blend, and granulated to obtain the saline-alkali soil remediation agent.

[0058] Example 3:

[0059] like Figure 1 As shown, a method for preparing a saline-alkali soil remediation agent comprises the following steps:

[0060] 1. The harvested alfalfa stems and leaves were naturally air-dried to a moisture content of ≤15% to obtain alfalfa residue. The alfalfa residue was crushed to a particle size of ≤3 mm, mixed with 0.3 mol / L phosphoric acid at a solid-liquid ratio of 1:3, and stirred at 40°C for 2 h to obtain an acid mixture. After cooling, the mixture was inoculated with Aspergillus niger to a concentration of 4×10 5 CFU / mL, with an inoculum size of 4%, the mixture was sealed and fermented at 40°C for 48 h, with stirring at 30 rpm for 10 min every 6 h to obtain an acidic fermentation broth;

[0061] 2. The pH of the acidic fermentation broth was adjusted to neutral with calcium hydroxide, urea (0.8% by weight of the acidic fermentation broth) was added, and Bacillus subtilis was inoculated to a concentration of 2.5×10 6 CFU / mL, and aerobically fermented at 50℃ for 5 days to obtain alfalfa humification fermentation material;

[0062] 3. The acidic fermentation broth was mixed with citric acid gypsum in a mass ratio of 2:1, stirred at 60°C for 4 hours, and crushed and sieved to obtain a chelated calcium gel with a particle size of 2-4 mm;

[0063] 4. The biochar was obtained by pyrolyzing sawdust at 600°C for 2 hours in an oxygen-limited atmosphere (a mixture of oxygen and nitrogen at a volume ratio of 1:19). The biochar was then immersed in alfalfa humification fermentation feed at a solid-liquid ratio of 1:6, ultrasonically treated for 1 hour, and then dried to obtain the modified biochar.

[0064] 5. Set the viable count to ≥1×10 10 The lyophilized powder of Priestia aryabhattai at 100 CFU / g was reconstituted with deionized water to obtain a bacterial agent, wherein the mass ratio of the lyophilized powder to the water was 1:100000;

[0065] 6. The alfalfa humified fermentation material, chelated calcium gel, modified biochar, bacterial agent and bentonite were mixed in a mass ratio of 60:25:12:7:5 to obtain a blend, and granulated to obtain the saline-alkali land soil remediation agent.

[0066] Comparative Example 1

[0067] A method for preparing a saline-alkali soil remediation agent, wherein the preparation steps and parameters are the same as those in Example 3, except that citric acid gypsum, an industrial by-product of gypsum, is not treated with acidic fermentation liquid and is directly used instead of chelated calcium gel.

[0068] Comparative Example 2

[0069] A method for preparing a saline-alkali soil remediation agent, wherein the preparation steps and parameters are the same as those in Example 3, except that the biochar is not modified.

[0070] Comparative Example 3

[0071] A method for preparing a saline-alkali soil remediation agent, wherein the preparation steps and parameters are the same as those in Example 3, except that the bacterial agent prepared by Priestia aryabhattai is not added.

[0072] Performance testing:

[0073] The test soil was collected from saline-alkali land in a coastal area. Before testing, the soil samples were air-dried and passed through a 2 mm sieve to remove impurities. 10 g of the saline-alkali soil remediation agents prepared in Examples 1-3 and Comparative Examples 1-3 were added to every 150 g of soil sample. Three months later, the pH, salinity, organic matter content, bulk density, porosity, and water-stable aggregate content were measured. The results are shown in Table 1.

[0074] The salt content is determined by the conductivity method according to the "Determination of Soluble Salt in Soil" (LY / T 1251-1999). The lower the salt content, the better the saline-alkali soil remediation agent prepared by the present invention has in restoring and improving saline-alkali land.

[0075] The organic matter content is determined according to the "Determination of Soil Organic Matter" (NY / T 1121.6-2006) using the potassium dichromate oxidation method. The higher the organic matter content, the better the saline-alkali land soil remediation agent prepared by the present invention has in remediating and improving saline-alkali land.

[0076] Bulk density and porosity: According to the "Determination of Soil Bulk Density" (NY / T 1121.4-2006) and the "Determination of Soil Porosity", calculated by the ring knife method, the lower the bulk density and the higher the porosity, the better the saline-alkali land soil remediation agent prepared by the present invention has a better remediation and improvement effect on saline-alkali land.

[0077] Water-stable aggregate content: According to the "Determination of Water-stable Aggregates in Soil" (NY / T 2957-2016), the content of water-stable aggregates with a particle size of ≥0.25 mm was calculated. The higher the water-stable aggregate content, the better the saline-alkali soil remediation agent prepared by the present invention has on the restoration and improvement of saline-alkali land.

[0078] Table 1 Performance test results

[0079]

[0080] As shown in Table 1, after the saline-alkali soil of Examples 1-3 was repaired and improved by the saline-alkali soil repair agent, the pH value dropped from 9.53 to 7.18-7.30, and the pH value was close to neutral; the salt content dropped from 4.12 g / kg to between 2.28-2.41 g / kg; the organic matter content increased from the initial 0.85% to 3.05%-3.20%; the bulk density increased from 1.32 g / cm 3 Down to 0.94-0.98g / cm 3 ; Porosity increased from 35.2% to 47.8%-49.2%; The content of water-stable aggregates increased from 12.5% ​​to 65.7-70.1%.

[0081] After the saline-alkali soil remediation agent prepared in Example 1-3 is mixed into the saline-alkali soil, the oxalic acid and citric acid produced in the acidolysis stage of the alfalfa humification fermentation material dissolve the soil carbonate and reduce the pH during the rapid desalination period, triggering the chelated calcium gel to react with the humic acid and Ca 2+ The dynamic dissociation of the coordination bond makes Ca 2+ Preferentially releases and replaces Na + At the same time, the humic acid loaded on the surface of the modified biochar accepts the electrons produced by the metabolism of Priestia aryabhattai through the quinone group (C=O), promotes its extracellular electron transfer process, and significantly increases the secretion of OH by the bacteria. - The efficiency of Na adsorption by modified biochar was +In the long-term remediation stage, the alfalfa humification fermentation material undergoes hydrogen bond cross-linking with the extracellular polysaccharides secreted by the bacteria through phenolic hydroxyl groups, forming a hybrid cementation layer supported by the modified biochar pore skeleton. This structure not only stabilizes soil aggregates, but also maintains the interaction between humic acid and Ca in the chelated calcium gel through microenvironmental regulation. 2+ The slow-release balance avoids the traditional repair agent from Ca 2+ Local compaction caused by sudden release. During this process, the organic acids in the alfalfa humification fermentation material initiate desalination, the pH responsiveness of the chelated calcium gel maintains calcium supply, the electron transfer of the modified biochar activates bacterial metabolism, and the bacterial metabolites complete the construction of the cementing network, forming a synergistic mechanism and achieving efficient and long-term saline-alkali soil remediation and improvement effects.

[0082] Comparative Example 1 used untreated gypsum, and the repair and improvement effect decreased, with the pH only reduced to 8.62 and the bulk density 1.18 g / cm 3 Ordinary gypsum lacks humic acid chelation and cannot achieve pH-responsive calcium release, resulting in insufficient neutralization of soil acidity and insignificant pH drop. 2+ Sudden release causes soil compaction, resulting in a dense soil with a bulk density of 1.18g / cm 3 , the pore connectivity is reduced by the hardening, the porosity is 40.1%, and the salt leaching is hindered after the hardening, and the hardening Na + The replacement efficiency is low, and the salt content is still 3.67g / kg; there is a lack of dynamic release of humic acid, which inhibits microbial activity and limits the accumulation of organic matter, with a content of 2.10%; no cementing layer is formed, the aggregates are easy to disintegrate, and the content of water-stable aggregates is only 28.9%.

[0083] In Comparative Example 2, the biochar was not modified, the pH dropped to 8.15, and the porosity was only 42.3%. This was attributed to the lack of humic acid loading on the biochar surface, the absence of quinone groups (C=O), the insufficient extracellular electron transfer activity of Priestia aryabhattai, and the OH - Decreased secretion, Na + The binding efficiency is low, the desalination effect is poor, and a stable cementing layer cannot be formed. Without humic acid loading, the organic matter adsorption and stabilization capacity decreases, the organic matter content is only 2.45%, and the water-stable aggregate content is 45.2%.

[0084] Comparative Example 3 did not add the bacterial agent prepared by Priestia aryabhattai, which lacked the OH secreted by the bacterial community. - , Na + Neutralization efficiency is low, pH drops to 8.40, salt content is 3.55g / kg; organic matter content is only 1.98%, bulk density is 1.16g / cm 3Due to the lack of extracellular polysaccharides secreted by the bacterial community, the alfalfa humified fermentation material could not form a cementing layer through hydrogen bonds, resulting in poor soil aggregate stability, with the content of water-stable aggregates being 21.4%, and insufficient organic matter accumulation of only 1.98%.

[0085] The above results show and describe the basic principles and main features of this application as well as the advantages of this application.

[0086] Those skilled in the art should understand that the present application is not limited to the above-described embodiments. The above-described embodiments and descriptions are merely illustrative of the principles of the present application. Various changes and improvements may be made to the present application without departing from the spirit and scope of the present application. Such changes and improvements are intended to fall within the scope of the present application. The scope of protection claimed in the present application is defined by the equivalents of the appended claims.

Claims

1. A method for preparing a saline-alkali soil remediation agent, characterized in that: The following steps are involved: S1, grinding alfalfa residue and mixing it with inorganic acid to obtain an acid mixture, and fermenting it with Aspergillus niger to obtain an acidic fermentation liquid; S2. Adjusting the pH of the acidic fermentation broth to neutral, adding a nitrogen source, and aerobically fermenting the broth with Bacillus subtilis to obtain an alfalfa humified fermentation material; S3, mixing the acidic fermentation liquid with industrial by-product gypsum to obtain a chelated calcium gel; S4, producing biochar by oxygen-limited pyrolysis of biomass, and impregnating and modifying the biochar by alfalfa humification fermentation material to obtain modified biochar; S5, reconstitute the lyophilized powder of Priesteria affluent into a bacterial agent; S6. Mixing the alfalfa humification fermentation material, chelated calcium gel, modified biochar, bacterial agent and adhesive to form granules to obtain the saline-alkali land soil remediation agent.

2. The method for preparing a saline-alkali soil remediation agent according to claim 1, wherein The alfalfa residue is the part of alfalfa stems and leaves with a water content of ≤15%; and the particle size of the alfalfa residue after being crushed is ≤3.0mm.

3. The method for preparing a saline-alkali soil remediation agent according to claim 1, wherein The inorganic acid is one of sulfuric acid, hydrochloric acid and phosphoric acid; the mass ratio of the alfalfa residue to the inorganic acid is 1:(2-4).

4. The method for preparing a saline-alkali soil remediation agent according to claim 1, wherein The inoculation amount of Aspergillus niger is as follows: the concentration of Aspergillus niger in the acid mixture is 3×10 5 -5×10 5 CFU / mL, the inoculum amount of the Bacillus subtilis is: the concentration of Bacillus subtilis in the acidic fermentation broth is 2×10 6 -3×10 6 CFU / mL.

5. The method for preparing a saline-alkali soil remediation agent according to claim 1, wherein: The nitrogen source is one of urea, ammonium sulfate and ammonium carbonate, and the added amount of the nitrogen source is 0.5%-1.0% of the mass of the acidic fermentation liquid.

6. The method for preparing a saline-alkali soil remediation agent according to claim 1, wherein: The solid-liquid mass ratio of the acidic fermentation liquid to the industrial by-product gypsum is (2-4):1; the industrial by-product gypsum is one of phosphogypsum, desulfurized gypsum and citric acid gypsum.

7. The method for preparing a saline-alkali soil remediation agent according to claim 1, wherein: The biomass is one of rice husks, straw and sawdust; the mass ratio of the biochar to the alfalfa humification fermentation material is 1:(4-6).

8. The method for preparing a saline-alkali soil remediation agent according to claim 1, wherein: The viable bacterial count of the freeze-dried powder of Priesteria aegypti is ≥1×10 10 CFU / g, and the mass ratio of the lyophilized powder of Priesteria afusiformis to deionized water during reconstitution is 1:(50000-100000).

9. The method for preparing a saline-alkali soil remediation agent according to claim 1, wherein: The binder is one of carboxymethyl cellulose and bentonite.

10. The method for preparing a saline-alkali soil remediation agent according to claim 1, characterized in that: The mass ratio of the alfalfa humification fermentation material, the chelated calcium gel, the modified biochar, the bacterial agent and the adhesive is (50-60):(25-35):(8-12):(3-7):(2-5).

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