Saline-alkali soil conditioner loaded with compound microorganisms as well as preparation method and application of saline-alkali soil conditioner

Abstract

The invention relates to the technical field of saline-alkali soil improvement, in particular to a compound microorganism-loaded saline-alkali soil conditioner as well as a preparation method and application thereof. Compound microorganisms loaded on the saline-alkali soil conditioner comprise Ralstonia sp. Ralstonia Bul-1 and Bacillus sp. Bacillus Zn-B. The preparation method of the saline-alkali soil conditioner comprises the following steps: (1) pretreating straws by using a zinc chloride solution, and carrying out hydrothermal carbonization on the pretreated straws; (2) respectively preparing a Ralstonia seed solution and a bacillus seed solution, and then mixing to prepare a compound bacterium seed solution; and (3) compounding the zinc-modified hydrothermal carbon and the compound bacteria seed solution to form a composite material, and then mixing the composite material with decomposed mushroom dregs or an organic fertilizer and a calcium magnesium phosphate fertilizer for granulation to form the saline-alkali soil conditioner. During application, the composite soil conditioner is applied to saline-alkali soil, and the dosage per mu is 300-500 kg. Through the synergistic effect of biochar, organic fertilizer, microorganisms and the like, the pH and salinity of the saline-alkali soil are remarkably reduced, the content of organic matter and aggregates is increased, the soil structure is improved, plant growth is promoted, and remarkable economic, ecological and social benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of saline-alkali soil improvement technology, and in particular to a saline-alkali soil conditioner loaded with composite microorganisms, its preparation method, and its application. Background Technology

[0002] Soil salinization refers to the process by which salts from the subsoil or groundwater rise to the surface via capillary action, and then accumulate in the topsoil after the water evaporates. It is also known as salinization or alkalinization, referring to the accumulation of easily soluble salts in the soil surface.

[0003] With the increasing salinization of land globally, traditional soil improvement methods (such as freshwater desalination and chemical amendments) are costly, prone to repetitive processes, and susceptible to secondary pollution. Biological soil improvement methods primarily utilize beneficial microorganisms to absorb soil salts, convert them into organic matter, and neutralize soil alkalinity, thus achieving soil improvement. Biological methods for soil improvement, with their advantages of lower cost and no secondary pollution or harmful substance generation, have become a research hotspot and a target for widespread application.

[0004] However, existing soil conditioners still fall short in improving soil fertility and promoting crop growth. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a saline-alkali soil conditioner loaded with composite microorganisms, its preparation method and application, which can better improve soil fertility and promote crop growth.

[0006] This invention is implemented as follows:

[0007] This invention first provides a saline-alkali soil conditioner loaded with composite microorganisms, wherein the composite microorganisms include Ralstonia sp. Ralstonia Bcul-1 and Bacillus sp. Bacillus Zn-B;

[0008] The Ralstonia sp. Ralstonia Bcul-1 mentioned therein is deposited at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, on April 12, 2019, with accession number CGMCCNO.17565.

[0009] The Bacillus sp. Bacillus Zn-B is deposited at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences. The deposit date is April 12, 2019, and the accession number is CGMCC No. 17563.

[0010] Furthermore, in the composite microorganism, the ratio of viable Bacillus sp. Bacillus Zn-B to Ralstonia sp. Ralstonia Bcul-1 is 2:1.

[0011] Furthermore, the composite microorganisms were loaded onto hydrothermal carbon.

[0012] Furthermore, the hydrothermal carbon is zinc-modified hydrothermal carbon, and the preparation method of the zinc-modified hydrothermal carbon includes the following steps:

[0013] (a) Crush crop straw to a particle size of <2mm;

[0014] (b) Add 0.2-0.5 mol / L zinc chloride solution to the crushed straw at a solid-liquid ratio of 1:4-1:6 and soak for more than 12 hours, stirring 3 times during the process;

[0015] (c) The straw mixture obtained in step b is transferred to a hydrothermal reactor and hydrothermally carbonized at 300℃-320℃ for 4-6 hours; after cooling, solid-liquid separation is performed to obtain zinc-modified hydrothermal carbon.

[0016] Furthermore, the method of loading the composite microorganisms with hydrothermal carbon is as follows: the raw materials are mixed to obtain a mixed solution, then left to stand overnight at room temperature, and finally the solid and liquid are separated and freeze-dried to obtain the hydrothermal carbon-based composite microbial material. The raw materials include hydrothermal carbon and composite bacterial seed liquid; wherein the mass concentration of the hydrothermal carbon is 10%-15%, and the proportion of the composite bacterial seed liquid is 5%-10% (volume ratio).

[0017] Furthermore, the raw materials for the saline-alkali soil conditioner also include decomposed fungal residue or organic fertilizer.

[0018] Furthermore, the raw materials for the saline-alkali soil conditioner also include calcium magnesium phosphate fertilizer.

[0019] Furthermore, the raw materials of the saline-alkali soil conditioner are as follows by mass ratio: 30%-40% zinc-modified hydrothermal carbon-supported composite microbial material, 40%-45% decomposed bacterial residue or organic fertilizer, 10%-15% calcium magnesium phosphate fertilizer, and 5% binder.

[0020] The present invention also provides a method for preparing the saline-alkali soil conditioner, which specifically includes the following steps:

[0021] (1) Crush the crop straw to a particle size of <2mm;

[0022] (2) Prepare a 0.2-0.5 mol / L zinc chloride solution, add it to the straw at a solid-liquid ratio of 1:4-1:6 and soak for more than 12 hours, stirring 3 times during the process;

[0023] (3) The obtained straw mixture was transferred to a hydrothermal reactor and hydrothermally carbonized at 300℃-320℃ for 4-6 hours; after water cooling, solid-liquid separation was performed to obtain zinc-modified hydrothermal carbon.

[0024] (4) Preparation of compound bacterial seed liquid:

[0025] a. In LB broth, Bacillus sp. Zn-B strain was incubated at 30°C for 150 rpm. -1 Incubate for 12-24 hours under the specified conditions, then at 12000 r·min -1 Centrifuge for 5 min to collect bacterial cells. Wash the bacterial cells three times with sterile water rinse solution and resuspend them in an equal volume of sterile water to prepare seed culture. The effective viable count in the seed culture is >10. 9 cfu / ml;

[0026] b. Ralstonia sp. Ralstonia Bcul-1 strain was incubated in LB liquid medium at 30°C for 150 rpm. -1 Incubate for 9-24 hours under the specified conditions, then at 12000 r·min -1 Centrifuge for 5 min to collect bacterial cells. Wash the bacterial cells three times with sterile water rinse solution and then resuspend them in an equal volume of sterile water to prepare seed culture. The effective viable count in the seed culture is >10. 9 cfu / ml;

[0027] c. Prepare a compound bacterial seed solution by mixing Bacillus sp. Bacillus Zn-B seed solution and Ralstonia sp. Ralstonia Bcul-1 seed solution at a volume ratio of 2:1.

[0028] (5) Preparation of zinc-modified hydrothermal carbon-supported composite microbial material: The zinc-modified hydrothermal carbon and the composite bacterial seed liquid are mixed. In the mixed solution, the mass concentration of the zinc-modified hydrothermal carbon is 10%-15%, the proportion of the composite bacterial seed liquid is 5%-10% (volume ratio), and the remainder is sterile water. The prepared mixed solution is allowed to stand overnight at room temperature, then the solid and liquid are separated and freeze-dried.

[0029] (6) Prepare a saline-alkali soil conditioner loaded with composite microorganisms. The raw materials are in the following mass ratio: 30%-40% zinc-modified hydrothermal carbon loaded with composite microorganisms, 40%-45% decomposed bacterial residue or organic fertilizer, 10%-15% calcium magnesium phosphate fertilizer, and 5% binder.

[0030] This invention also provides the application of a saline-alkali soil conditioner in saline-alkali soil, wherein the composite soil conditioner is applied to the saline-alkali soil at a dosage of 300-500 kg per acre.

[0031] The present invention has the following advantages:

[0032] (1) The saline-alkali soil conditioner of the present invention is loaded with composite microorganisms. By utilizing the synergistic effect of Rawstone bacteria and Bacillus, it can improve the crop's ability to withstand saline-alkali stress, thereby reducing costs and preparation complexity.

[0033] (2) The saline-alkali soil conditioner of the present invention is a microbial compound agent loaded with zinc-modified biochar. The purpose of zinc modification is: first, to improve the enzyme activity of the strains, and second, to promote their reproduction in the soil.

[0034] (3) The saline-alkali soil conditioner of the present invention is specifically composed of zinc-modified biochar-loaded microbial compound inoculant (Rolstonia + Bacillus), decomposed inoculant residue or organic fertilizer, and calcium magnesium phosphate fertilizer. Through the synergistic effect of zinc-modified biochar, organic fertilizer, and microorganisms, it significantly reduces the pH and salinity of saline-alkali land, increases the content of organic matter and aggregates, improves soil structure, and promotes plant growth, thus having significant economic, ecological, and social benefits.

[0035] (4) This invention uses agricultural waste as raw material to create a multifunctional soil conditioner that integrates salt reduction, alkali improvement, fertilization and growth promotion, and builds a low-cost, high-efficiency and environmentally friendly green technology system. Attached Figure Description

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] Figure 1 The pH changes of saline-alkali soil in different implementation cases (soil pH was measured by potentiometric method, according to "HJ 962-2018 Determination of Soil pH by Potentiometric Method").

[0038] Figure 2 The variation of salinity in saline-alkali soil in different implementation cases (soil salinity was determined in accordance with NY / T 1121.16-2006 Soil Testing Part 16: Determination of Total Water-Soluble Salts in Soil).

[0039] Figure 3The variation of soil organic matter content in different implementation cases (soil organic matter was determined by potassium dichromate oxidation method, according to "NY / T 1121.6-2006 Soil Testing Part 6: Determination of Soil Organic Matter").

[0040] Figure 4 The variation of soil ammonium nitrogen content in different implementation cases was studied (soil ammonium nitrogen content was determined by potassium chloride solution extraction-spectrophotometry, according to "HJ 634—2012 Determination of Soil Ammonia Nitrogen, Nitrite Nitrogen and Nitrate Nitrogen by Potassium Chloride Solution Extraction-Spectrophotometry").

[0041] Figure 5 The changes in soil urease activity in different implementation cases (soil urease activity was determined by the indophenol blue colorimetric method, according to GB / T 23744-2009 Determination of Soil Urease Activity by Indophenol Blue Colorimetric Method).

[0042] Figure 6 The changes in the number of Bacillus subtilis in different implementation cases were investigated (the number of Bacillus subtilis in the soil was determined by quantitative PCR, and soil DNA was extracted using a dye-based quantitative PCR kit with primers BacF / 1378R, following the method described in the reference [Wang Jing, Yang Jinglin, Liao Jiancheng, et al. Study on the effect of rice-rice-rapeseed rotation on the number of Bacillus subtilis in soil. Journal of Jiangxi Agricultural University, 2019, 41(1):43-49]). Detailed Implementation

[0043] The technical solution of the present invention will now be clearly and completely described in conjunction with the accompanying drawings and specific embodiments. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0044] The present invention discloses a method for preparing a saline-alkali soil conditioner loaded with composite microorganisms, which specifically includes the following steps:

[0045] (1) Crush the crop straw to a particle size of <2mm;

[0046] (2) Prepare a 0.2-0.5 mol / L zinc chloride solution, add it to the straw at a solid-liquid ratio of 1:4-1:6 and soak for more than 12 hours, stirring 3 times during the process;

[0047] (3) The obtained straw mixture was transferred to a hydrothermal reactor and hydrothermally carbonized at 300℃-320℃ for 4-6 hours; after water cooling, solid-liquid separation was performed to obtain zinc-modified hydrothermal carbon.

[0048] (4) Preparation of compound bacterial seed liquid:

[0049] a. In LB broth, Bacillus sp. Zn-B strain was incubated at 30°C for 150 rpm. -1 Incubate for 12-24 hours under the specified conditions, then at 12000 r·min -1 Centrifuge for 5 min to collect bacterial cells. Wash the bacterial cells three times with sterile water rinse solution and resuspend them in an equal volume of sterile water to prepare seed culture. The effective viable count in the seed culture is >10. 9 cfu / ml;

[0050] b. Ralstonia sp. Ralstonia Bcul-1 strain was incubated in LB liquid medium at 30°C for 150 rpm. -1 Incubate for 9-24 hours under the specified conditions, then at 12000 r·min -1 Centrifuge for 5 min to collect bacterial cells. Wash the bacterial cells three times with sterile water rinse solution and then resuspend them in an equal volume of sterile water to prepare seed culture. The effective viable count in the seed culture is >10. 9 cfu / ml;

[0051] c. Prepare a compound bacterial seed solution by mixing Bacillus sp. Bacillus Zn-B seed solution and Ralstonia sp. Ralstonia Bcul-1 seed solution at a volume ratio of 2:1.

[0052] (5) Preparation of zinc-modified hydrothermal carbon-supported composite microbial material: The zinc-modified hydrothermal carbon and the composite bacterial seed liquid are mixed. In the mixed solution, the mass concentration of the zinc-modified hydrothermal carbon is 10%-15%, the proportion of the composite bacterial seed liquid is 5%-10% (volume ratio), and the remainder is sterile water. The prepared mixed solution is allowed to stand overnight at room temperature, then the solid and liquid are separated and freeze-dried.

[0053] (6) Prepare a saline-alkali soil conditioner loaded with composite microorganisms. The raw materials are in the following mass ratio: 30%-40% zinc-modified hydrothermal carbon loaded with composite microorganisms, 40%-45% decomposed bacterial residue or organic fertilizer, 10%-15% calcium magnesium phosphate fertilizer, and 5% binder.

[0054] (7) Apply the saline-alkali soil conditioner into the saline-alkali soil at a rate of 300-500 kg per mu.

[0055] Implementation Case 1:

[0056] Rice straw is added to distilled water at a solid-liquid ratio of 1:4 and hydrothermally carbonized at 300℃ for 4 hours to obtain hydrothermal carbon. Then, a composite soil conditioner is prepared by mixing 45% rice straw hydrothermal carbon, 50% composted fungal residue, and 5% binder and granulating the mixture. The conditioner is then applied to vegetable fields at a rate of 300 kg per acre.

[0057] Implementation Case 2:

[0058] Unlike Implementation Case 1, hydrothermal charcoal made from rice straw was replaced with a hydrothermal charcoal-Bacillus Zn-B composite material. A mixed aqueous solution was prepared with 10% hydrothermal charcoal by mass and 10% Bacillus Zn-B seed liquid by volume. After standing overnight at room temperature, solid-liquid separation and drying were performed to obtain the hydrothermal charcoal-Bacillus Zn-B composite material. Then, a composite soil conditioner was prepared by mixing 45% hydrothermal charcoal-Bacillus Zn-B composite material, 50% composted fungal residue, and 5% binder, and granulating the mixture. This was applied to the vegetable field at a rate of 300 kg per acre.

[0059] Implementation Case 3:

[0060] Unlike Implementation Case 2, Bacillus Zn-B seed solution was replaced with Ralstonia Bcul-1 seed solution to prepare a hydrothermal charcoal-Ralstonia Bcul-1 composite material. A composite soil conditioner was prepared by mixing and granulating 45% hydrothermal charcoal-Ralstonia Bcul-1 composite material, 50% composted fungal residue, and 5% binder, and applied to the vegetable field at a rate of 300 kg per acre.

[0061] Implementation Case 4:

[0062] Unlike Implementation Case 2, Bacillus Zn-B seed liquid was replaced with compound bacterial seed liquid to prepare hydrothermal charcoal-composite microbial material, in which the ratio of viable bacteria of the two strains was 1:1. A composite soil conditioner was prepared by mixing and granulating 45% hydrothermal charcoal-composite microbial material, 50% composted bacterial residue, and 15% binder, and applied to the vegetable field at a rate of 300 kg per acre.

[0063] Implementation Case 5:

[0064] Unlike Implementation Case 4, the ratio of viable bacteria counts of the two strains in the compound bacterial seed solution was 2:1.

[0065] Implementation Case 6:

[0066] Unlike Implementation Case 5, zinc-modified hydrothermal charcoal was used instead of rice straw hydrothermal charcoal. Rice straw was added to a 0.3 mol / L ZnCl2 aqueous solution at a solid-liquid ratio of 1:4 and soaked for 12 hours. Then, it was hydrothermally carbonized at 300℃ for 4 hours to obtain zinc-modified hydrothermal charcoal. Finally, a composite soil conditioner was prepared by mixing and granulating 45% zinc-modified hydrothermal charcoal with composite microbial material, 50% composted microbial residue, and 5% binder. This mixture was applied to vegetable fields at a rate of 300 kg per acre.

[0067] Implementation Case 7:

[0068] Unlike Implementation Case 6, the raw material formula of the saline-alkali soil conditioner is different. The compound soil conditioner is prepared by mixing and granulating 45% zinc-modified hydrothermal carbon-composite microbial material, 40% composted bacterial residue, 10% calcium magnesium phosphate fertilizer, and 5% binder, and is applied to the vegetable field at a rate of 300 kg per acre.

[0069] The implementation results of each case study are shown in Table 1 and Figure 1-Figure 5 As shown.

[0070] Table 1. Implementation Results of Different Implementation Cases

[0071]

[0072]

[0073] Compared with Case 1, the yields of leafy sweet potatoes in Cases 2 and 3 increased by 9.8% and 3.3%, respectively, and the protein content also increased to varying degrees. In Cases 2 and 3, the soil conditioners, loaded with Bacillus Zn-B and Ralstonia Bcul-1, respectively, reduced the pH of saline-alkali soil by 0.02 and 0.05 units, respectively; decreased soil salinity by 1.9% and 1.3%, respectively; increased soil organic matter content by 5.8% and 1.9%, respectively; increased ammonium nitrogen content by 14.8% and 8.0%, respectively; and increased urease activity by 24.9% and 19.7%, respectively. This indicates that loading the soil conditioner with both strains can improve the properties of saline-alkali soil, enhance soil fertility, and promote crop growth.

[0074] Compared with Case 2, Case 3 showed a 6.3% increase in sweet potato yield, a 0.1-unit decrease in pH of saline-alkali soil, a 0.7% decrease in soil salinity, a 3.8% increase in soil organic matter content, a 6.3% increase in ammonium nitrogen content, and a 4.3% increase in urease activity. This indicates that soil conditioner loaded with Bacillus Zn-B is more effective than Ralstonia Bcul-1 in promoting organic matter decomposition, nutrient release, and crop growth.

[0075] Compared with Case 2, Cases 4 and 5 showed an increase in sweet potato yield of 1.5% and 7.5%, respectively, and also an increase in protein content to varying degrees. In Cases 4 and 5, the soil conditioner, simultaneously loaded with both Bacillus Zn-B and Ralstonia Bcul-1 strains, resulted in a decrease in saline-alkali soil pH of 0.19 and 0.1 units, a decrease in soil salinity of 2.6% and 6.6%, an increase in soil organic matter content of 1.8% and 3.6%, an increase in ammonium nitrogen content of 9.2% and 11.7%, and an increase in urease activity of 8.7% and 12.8%, respectively. This indicates that loading the soil conditioner with the two strains can produce a synergistic effect, which is more beneficial for saline-alkali soil improvement and crop growth.

[0076] Compared with Case 4, Case 5 showed a 5.9% increase in sweet potato yield, a 0.03-unit decrease in pH of saline-alkali soil, a 4.1% decrease in soil salinity, a 1.8% increase in soil organic matter content, a 2.3% increase in ammonium nitrogen content, and a 3.8% increase in urease activity. This indicates that a 2:1 ratio of viable Bacillus Zn-B to Ralstonia Bcul-1 cells is more effective than a 1:1 treatment.

[0077] Compared with Case 5, Case 6 showed an 11.1% increase in sweet potato yield, a 0.1-unit decrease in pH of saline-alkali soil, a 6.2% decrease in soil salinity, a 7.0% increase in soil organic matter content, a 9.2% increase in ammonium nitrogen content, and a 14.3% increase in urease activity. This indicates that zinc-modified hydrothermal carbon can improve the enzyme activity of the supported strains and enhance the soil amendment effect on saline-alkali soil under the same conditions.

[0078] Compared with Case 6, Case 7 showed a 6.4% increase in sweet potato yield, a 0.08-unit decrease in pH of saline-alkali soil, an 8.3% decrease in soil salinity, a 4.9% increase in soil organic matter content, an 8.1% increase in ammonium nitrogen content, and an 8.8% increase in urease activity. This indicates that by further adding calcium magnesium phosphate fertilizer to the zinc-modified hydrothermal carbon-supported microorganisms, magnesium ions can replace sodium ions in saline-alkali soil, reducing their activity and further improving the soil improvement effect.

[0079] Compared with Case 5, the number of Bacillus in the soil of Case 6 and Case 7 increased by 25.6% and 29.0%, respectively, indicating that when zinc-modified hydrothermal carbon is used as a carrier matrix, its unique porous structure and surface functional groups (such as carboxyl groups and phenolic hydroxyl groups) can significantly improve the bioavailability of soil microorganisms.

[0080] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and not intended to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A soil conditioner for saline-alkali soil loaded with composite microorganisms, characterized in that: The loaded composite microorganisms include Ralstonia sp. Ralstonia Bcul-1 and Bacillus sp. Bacillus Zn-B; The Ralstonia sp. Ralstonia Bcul-1 mentioned therein is deposited at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, on April 12, 2019, with accession number CGMCCNO.17565. The Bacillus sp. Bacillus Zn-B is deposited at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences. The deposit date is April 12, 2019, and the accession number is CGMCC No. 17563.

2. The saline-alkali soil conditioner loaded with composite microorganisms according to claim 1, characterized in that: In the composite microorganism, the ratio of viable Bacillus sp. Bacillus Zn-B to Ralstonia sp. Ralstonia Bcul-1 is 2:

1.

3. The saline-alkali soil conditioner loaded with composite microorganisms according to claim 1, characterized in that: The composite microorganisms were loaded using hydrothermal carbon.

4. The saline-alkali soil conditioner loaded with composite microorganisms according to claim 3, characterized in that: The hydrothermal carbon is zinc-modified hydrothermal carbon, and the preparation method of the zinc-modified hydrothermal carbon includes the following steps: (a) Crush crop straw to a particle size of <2mm; (b) Add 0.2-0.5 mol / L zinc chloride solution to the crushed straw at a solid-liquid ratio of 1:4-1:6 and soak for more than 12 hours, stirring 3 times during the process; (c) The straw mixture obtained in step b is transferred to a hydrothermal reactor and hydrothermally carbonized at 300℃-320℃ for 4-6 hours; after cooling, solid-liquid separation is performed to obtain zinc-modified hydrothermal carbon.

5. The saline-alkali soil conditioner loaded with composite microorganisms according to claim 3, characterized in that: The method for loading the composite microorganisms with hydrothermal char is as follows: the raw materials are mixed to obtain a mixed solution, then left to stand overnight at room temperature, and finally the solid and liquid are separated and freeze-dried to obtain the hydrothermal char-based composite microbial material; the raw materials include hydrothermal char and composite bacterial seed liquid; wherein the mass concentration of the hydrothermal char is 10%-15%, and the volume percentage of the composite bacterial seed liquid is 5%-10%.

6. The saline-alkali soil conditioner loaded with composite microorganisms according to claim 1, characterized in that: The raw materials for the saline-alkali soil conditioner also include decomposed fungal residue or organic fertilizer.

7. The saline-alkali soil conditioner loaded with composite microorganisms according to claim 1, characterized in that: The raw materials for the saline-alkali soil conditioner also include calcium magnesium phosphate fertilizer.

8. The saline-alkali soil conditioner loaded with composite microorganisms according to claim 1, characterized in that: The raw materials of the saline-alkali soil conditioner are as follows by mass ratio: 30%-40% zinc-modified hydrothermal carbon-supported composite microbial material, 40%-45% decomposed bacterial residue or organic fertilizer, 10%-15% calcium magnesium phosphate fertilizer, and 5% binder.

9. A method for preparing a saline-alkali soil conditioner loaded with composite microorganisms, characterized in that: Specifically, the steps include the following: (1) Crush the crop straw to a particle size of <2mm; (2) Prepare a 0.2-0.5 mol / L zinc chloride solution, add it to the straw at a solid-liquid ratio of 1:4-1:6 and soak for more than 12 hours, stirring 3 times during the process; (3) The obtained straw mixture was transferred to a hydrothermal reactor and hydrothermally carbonized at 300℃-320℃ for 4-6 hours; after water cooling, solid-liquid separation was performed to obtain zinc-modified hydrothermal carbon. (4) Preparation of compound bacterial seed liquid: a. In LB broth, Bacillus sp. Zn-B strain was incubated at 30°C for 150 rpm. -1 Incubate for 12-24 hours under the specified conditions, then at 12000 r·min -1 Centrifuge for 5 min to collect bacterial cells. Wash the bacterial cells three times with sterile water rinse solution and resuspend them in an equal volume of sterile water to prepare seed culture. The effective viable count in the seed culture is >10. 9 cfu / ml; b. Ralstonia sp. Ralstonia Bcul-1 strain was incubated in LB liquid medium at 30°C for 150 rpm. -1 Incubate for 9-24 hours under the specified conditions, then at 12000 r·min -1 Centrifuge for 5 min to collect bacterial cells. Wash the bacterial cells three times with sterile water rinse solution and then resuspend them in an equal volume of sterile water to prepare seed culture. The effective viable count in the seed culture is >10. 9 cfu / ml; c. Prepare a compound bacterial seed solution by mixing Bacillus sp. Bacillus Zn-B seed solution and Ralstonia sp. Ralstonia Bcul-1 seed solution at a volume ratio of 2:1; (5) Preparation of zinc-modified hydrothermal carbon-supported composite microbial material: The zinc-modified hydrothermal carbon and the composite bacterial seed liquid are mixed. In the mixed solution, the mass concentration of the zinc-modified hydrothermal carbon is 10%-15%, the volume ratio of the composite bacterial seed liquid is 5%-10%, and the remainder is sterile water. The prepared mixed solution is allowed to stand overnight at room temperature, then the solid and liquid are separated and freeze-dried. (6) Prepare a saline-alkali soil conditioner loaded with composite microorganisms. The raw materials are in the following mass ratio: 30%-40% zinc-modified hydrothermal carbon loaded with composite microorganisms, 40%-45% composted bacterial residue or organic fertilizer, 10%-15% calcium magnesium phosphate fertilizer, and 5% binder. Mix the raw materials and granulate to obtain the saline-alkali soil conditioner loaded with composite microorganisms.

10. The application of the saline-alkali soil conditioner as described in claims 1-8 or the saline-alkali soil conditioner prepared by the method described in claim 9 in saline-alkali soil, characterized in that: Apply the compound soil conditioner to saline-alkali soil at a rate of 300-500 kg per acre.

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