A biochar loaded halotolerant bacteria amendment for saline soil and a method of amendment

Abstract

The application discloses a kind of saline soil's biochar load salt-tolerant bacteria's modifier and improvement method, the modifier includes: modified biochar load salt-tolerant bacteria, pre-wetting liquid, cementing liquid and nitrifying bacteria liquid;Wherein, according to every kilogram of body dry soil calculation, the added mass of modified biochar load salt-tolerant bacteria is 2%~5%, the volume of pre-wetting liquid is (60-200) mL / kg, the volume of cementing liquid is (30-80) mL / kg, the volume of nitrifying bacteria liquid is (1-3.5) mL / kg, the improvement method will be 1g modified biochar: (5-15) mL of salt-tolerant bacteria liquid is oscillated, and modified biochar load salt-tolerant bacteria is obtained, pre-wetting liquid is then added and fully stirred, is sprayed by cementing liquid in multiple times, finally nitrifying bacteria liquid is applied, and the improvement of saline soil's biochar load salt-tolerant bacteria is completed;The application takes modified biochar load salt-tolerant bacteria as core, is matched with pre-wetting liquid and gradient concentration cementing liquid, and can complete "carrier bacteria→chemical salt adjustment→biological consolidation" accurate regulation.

Description

Technical Field

[0001] This invention relates to the field of saline-alkali land improvement, specifically to a biochar-loaded salt-tolerant bacteria improver and improvement method for saline soil. Background Technology

[0002] my country has a wide distribution of saline soil resources, mainly coastal chloride saline soils and inland sulfate saline soils. These soils generally suffer from high salt content, high alkalinity, high sodium adsorption ratio (SAR), loose structure, poor permeability, and weak microbial activity, severely hindering agricultural production and ecological restoration. Coastal saline soils, due to seawater infiltration, have extremely high chloride and sodium ion content and high sodium saturation in soil colloids, leading to dispersed soil particles and structural damage. They easily form crusts after rain or irrigation, becoming hard and compacted when dry, resulting in extremely poor water and air permeability. Inland sulfate saline soils, due to the effects of sodium sulfate and magnesium sulfate, exhibit obvious salt crusts and salt spots. After irrigation, the salt dissolves but quickly accumulates on the surface after water evaporation, making crop emergence difficult and hindering growth. The high-salt environment inhibits the metabolism and reproduction of most soil microorganisms, resulting in slow mineralization of organic matter and impaired nutrient cycling in saline soils. Even with the application of nitrogen, phosphorus, and potassium fertilizers, crop absorption efficiency is very low.

[0003] Existing saline soil improvement technologies have significant limitations: single chemical amendments (such as gypsum, aluminum sulfate, and polyacrylamide) show rapid effects in reducing salinity and adjusting alkalinity, but are prone to rebound, and long-term use can lead to soil compaction and secondary salinization; common microbial agents have poor salt tolerance and resilience, making it difficult to colonize and survive in high-salt environments, resulting in insufficient functional sustainability, with the bacterial count often declining significantly after one week of application; conventional biochar and organic materials have limited adsorption capacity, single functions, and unclear synergistic mechanisms with microorganisms, leading to unstable improvement effects. Furthermore, while some compound formulations have diverse components, they are cumbersome to operate and costly, making them difficult to promote and apply at the grassroots level. In short, saline soils in many parts of my country (whether coastal or inland) are generally characterized by high salt content, high alkalinity, loose soil particles, poor aeration, inability to utilize nutrients, and poor microbial activity, making it difficult for crops to grow. Current commonly used improvement methods all have shortcomings: chemical agents reduce salt quickly but are prone to rebound and damage the soil; ordinary microbial agents are sensitive to salt and die quickly after application; biochar or organic fertilizers have limited effects and their combined effect with microorganisms is unstable; complex formulas are costly and difficult to promote. Therefore, there is an urgent need to develop a practical improvement technology that can simultaneously achieve "soil stabilization + salt reduction + microbial cultivation + fertilization". Summary of the Invention

[0004] The purpose of this invention is to provide a modifier for biochar-loaded salt-tolerant bacteria in saline soil, which can improve the survival rate and activity duration of bacteria in high-salt soil, ensure that the bacteria can metabolize and produce enzymes and acids normally in saline soil, continuously participate in the decomposition and mineralization of organic matter, and complete the precise regulation of "carrier solidification of bacteria → chemical salt regulation → biological solidification".

[0005] To achieve the above objectives, a biochar-supported salt-tolerant bacteria amendment for saline soil comprises: Modified biochar loaded with salt-tolerant bacteria, pre-wetted solution, cementing solution and nitrifying bacteria solution; Based on soil, the modified biochar load contains 2%-5% salt-tolerant bacteria by mass. The volume ratio of the pre-wetting liquid to each kilogram of soil is (60-200) mL / kg; The volume ratio of the cementing liquid to every kilogram of soil is (30-80) mL / kg; The volume ratio of nitrifying bacteria solution to soil is (1-3.5) mL / kg.

[0006] In some examples of the present invention, the modified biochar is loaded with 3% salt-tolerant bacteria per kilogram of soil; The volume of the pre-wetting liquid is 100 mL / kg of soil. The volume ratio of the cementing solution to every kilogram of soil is 50 mL / kg; The volume ratio of nitrifying bacteria solution to soil is 2 mL / kg.

[0007] In some examples of the present invention, the modified biochar-supported salt-tolerant bacteria are obtained by mixing modified biochar and salt-tolerant bacteria. Modified biochar is obtained from corn stalks / rice husks through acid washing activation and pyrolysis activation. Salt-tolerant bacteria are salt-tolerant and domesticated strains of Bacillus pasteurellii.

[0008] In some examples of the present invention, the pre-wetting solution comprises a mixture of 1%-3.2% w / v calcium lignosulfonate and 0.36%-0.65% w / v polyaspartic acid; or: The pre-wetting solution is a mixture of 1%-3.2% w / v calcium lignosulfonate, 0.03%-0.06% w / v sodium alginate, and 0.3%-0.7% w / v carboxymethyl cellulose.

[0009] In some examples of the present invention, the pre-wetting solution comprises 2% w / v calcium lignosulfonate and 0.5% w / v polyaspartic acid; or: The pre-wetting solution includes 2% w / v calcium lignosulfonate, 0.05% w / v sodium alginate, and 0.5% w / v carboxymethyl cellulose.

[0010] In some examples of the present invention, the cementing solution is composed of (0.5-1) mol / L calcium chloride, (0.5-1) mol / L urea, and (0.008%-0.011%) w / v rhamnolipid; The nitrifying bacteria solution includes Nitrosomonas and Nitrobacterium, with a total viable count ≥1×10⁻⁶. 8 CFU / mL.

[0011] The purpose of this invention is to provide an improved method for loading salt-tolerant bacteria onto biochar in saline soil. The method uses modified biochar loaded with salt-tolerant bacteria as the core, combined with pre-wetting liquid and cementing liquid of varying concentrations, to achieve precise control of "carrier solidification of bacteria → chemical salt adjustment → biological solidification". This method can ensure that the bacteria continuously participate in the decomposition and mineralization of organic matter in saline soil.

[0012] A method for improving the biochar loading of halophilic bacteria in saline soil specifically includes the following steps: S1, Preparation of modified biochar-supported salt-tolerant bacteria; S1-1, made from corn stalks / rice husks, crushed through a 10-50 mesh sieve; The pulverized raw material is first mixed with (0.4-0.6) mol / L hydrochloric acid at a material-to-water ratio of 1:(12-20) and soaked for 1.5-2.4 h. Then it is heated with (1.8-2.4) mol / L KOH at a ratio of 1:(8-12) in a (70-90)℃ water bath for (18-36) hours to obtain a mixture. The mixture was pyrolyzed and activated to obtain modified biochar; S1-2, prepare a basic culture medium containing yeast extract, ammonium sulfate, and buffer solution, and add trace amounts of Mn and Zn trace elements; Starting with Bacillus pasteurellii, salt-tolerant strains of Bacillus pasteurellii were obtained by gradually increasing the NaCl concentration from 0.5% to 2% to achieve salt tolerance. S1-3, shake the modified biochar solution at a ratio of 1g modified biochar to (5-15)mL of salt-tolerant bacteria to ensure sufficient adsorption and obtain modified biochar loaded with salt-tolerant bacteria; S2, first add the modified biochar loaded with salt-tolerant bacteria to the dry soil and mix evenly, then add the pre-wetting liquid and stir thoroughly to pre-wet the soil, and then spray the cementing liquid in multiple times; after each spray, let it stand and cure at 25-30℃, keeping the soil moist but not waterlogged, until the next spray. S3, at least 24 hours after the 5th spray, apply nitrifying bacteria solution to complete the improvement of saline soil with biochar-loaded salt-tolerant bacteria.

[0013] In some examples of the present invention, the preparation method of the cementing solution is as follows: urea and calcium chloride are dissolved in deionized water, and the pH is adjusted to 7.2-7.5; In step S2, the cementing solution is sprayed in five stages. In the first spray, the cementing solution is a mixture of 0.5 mol / L calcium chloride, 0.5 mol / L urea and 0.01% w / v rhamnolipid. During the second and third spraying, the cementing solution was mixed with 0.75 mol / L calcium chloride, 0.75 mol / L urea and 0.01% w / v rhamnolipid; During the fourth and fifth spraying, the cementing solution was a mixture of 1 mol / L calcium chloride, 1 mol / L urea, and 0.01% w / v rhamnolipid.

[0014] In some examples of the present invention, in step S1-1, corn stalks / rice husks are used as raw materials and crushed through a 20-mesh sieve; The pulverized raw material was first mixed with 0.5 mol / L hydrochloric acid at a material-to-water ratio of 1:15 and soaked for 2 hours. Then it was heated with 2 mol / L KOH at a ratio of 1:10 in an 80°C water bath for 24 hours to obtain a mixture. The mixture was pyrolyzed and activated under 500°C and oxygen-deficient conditions for 2 hours to obtain pyrolytic char. The pyrolytic char was then ground through a 50-mesh sieve and packaged and stored under aseptic conditions for later use to obtain modified biochar. In steps S1-2, a basic culture medium is prepared comprising 20 g / L yeast extract, 10 g / L ammonium sulfate, and 0.13 mol / L Tris buffer. Start with a NaCl concentration of 0.5%, and increase it by 0.3-0.5% each time, gradually reaching 2% NaCl.

[0015] In some examples of the present invention, the preparation method of the pre-wetting liquid includes: first dissolving calcium lignosulfonate in deionized water, then adding polyaspartic acid, stirring until completely dissolved, and adjusting the pH to 7.0.

[0016] Compared with existing technologies, a biochar-supported salt-tolerant bacteria amendment for saline soil uses modified biochar-supported salt-tolerant bacteria as its core, combined with pre-wetting liquid and gradient concentration cementing liquid, to achieve precise control of "carrier solidification → chemical salt adjustment → biological solidification". The porous structure and high specific surface area of ​​the modified biochar provide physical protection and a nutrient microenvironment for the salt-tolerant bacteria, improving their survival rate and activity duration in high-salt soils. The salt-tolerant bacteria are salt-tolerant Bacillus pasteurellii strains, ensuring normal metabolism and enzyme and acid production in saline soils, continuously participating in organic matter decomposition and mineralization. Furthermore, the use of gradient concentration spraying cementing liquid avoids the initial high concentration's impact on microorganisms and gradually strengthens soil particle solidification. Biochar adsorbs sodium and chloride ions, while calcium lignosulfonate and polyaspartic acid promote sodium ion leaching. Combined with the buffering effect of calcium carbonate mineralization on soil pH, both soil electrical conductivity and pH decrease. The addition of nitrifying bacteria solution in the later stage accelerates nitrogen conversion and improves ammonium nitrogen utilization. Attached Figure Description

[0017] Figure 1This is a flowchart of the improved method for loading salt-tolerant bacteria onto biochar in saline soil according to the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, “an” or “a” and similar terms do not necessarily indicate a quantity limitation. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0020] A biochar-supported salt-tolerant bacteria modifier for saline soil includes: Modified biochar loaded with salt-tolerant bacteria, pre-wetted solution, cementing solution and nitrifying bacteria solution; Based on soil, the modified biochar is loaded with 2%-5% salt-tolerant bacteria by mass, preferably 3%; The volume ratio of the pre-wetting liquid to each kilogram of soil is (60-200) mL / kg, preferably 100 mL / kg; The volume ratio of the cementing liquid to each kilogram of soil is (30-80) mL / kg, preferably 50 mL / kg; The volume ratio of nitrifying bacteria solution to soil is (1-3.5) mL / kg, preferably 2 mL / kg; Furthermore, modified biochar loaded with salt-tolerant bacteria is obtained by mixing modified biochar and salt-tolerant bacteria. Modified biochar is obtained from corn stalks / rice husks through acid washing activation and pyrolysis activation. Salt-tolerant bacteria are salt-tolerant, domesticated strains of Bacillus pasteurellii. Furthermore, the pre-wetting solution comprises a mixture of 1%-3.2% w / v calcium lignosulfonate and 0.36%-0.65% w / v polyaspartic acid; preferably, the pre-wetting solution comprises 2% w / v calcium lignosulfonate and 0.5% w / v polyaspartic acid. or: The pre-wetting solution comprises a mixture of 1%-3.2% w / v calcium lignosulfonate, 0.03%-0.06% w / v sodium alginate, and 0.3%-0.7% w / v carboxymethyl cellulose; preferably, the pre-wetting solution comprises 2% w / v calcium lignosulfonate, 0.05% w / v sodium alginate, and 0.5% w / v carboxymethyl cellulose. Furthermore, the cementing solution is composed of (0.5-1) mol / L calcium chloride, (0.5-1) mol / L urea, and (0.008%-0.011%) w / v rhamnolipid. Specifically, when the pre-wetting solution includes calcium lignosulfonate and polyaspartic acid, polyaspartic acid can rapidly chelate Na+. + As it moves downwards with moisture, it can accelerate desalination when combined with subsequent cementing solutions (urea + calcium chloride). In particular, when combined with subsequent cementing solutions containing urea and calcium chloride, it can accelerate desalination and is suitable for coastal chloride saline soils with high sodium content, easy compaction, and good leaching conditions. When the pre-wetting solution includes calcium lignosulfonate, sodium alginate, and carboxymethyl cellulose, carboxymethyl cellulose can increase the solution viscosity and reduce surface aggregation caused by evaporation; sodium alginate reacts with the Ca in calcium lignosulfonate. 2+ It forms a thin gel layer that can temporarily seal surface cracks and inhibit salt "return". At the same time, it needs to be covered or drip-irrigated to avoid excessive surface crusting. It is suitable for inland sulfate soils with drought, high evaporation and severe salt accumulation. Alternatively, the two pre-wetting solutions mentioned above can be used together. Initially, sodium alginate and carboxymethyl cellulose are used to solidify the solution and inhibit salt return. After a certain interval, calcium lignosulfonate and polyaspartic acid are used to promote deep leaching of sodium ions. This interval can be 3-5 days or until slight signs of salt return appear in the surface soil. In addition, the total water volume should be controlled to avoid excessive soil moisture leading to oxygen deficiency. This method is suitable for well-drained soils, or the total water volume can be adjusted according to the soil texture. The cementing solution was sprayed multiple times, with 0.01% w / v rhamnolipin added to each spray. This rhamnolipin acts as a wetting and dispersing agent. The nitrifying bacteria solution promotes the conversion of ammonium nitrogen to nitrate nitrogen, reduces ammonia volatilization loss, and improves nitrogen availability. Simultaneously, the H2 produced by nitrification... + It can help lower soil pH; A biochar-supported salt-tolerant bacteria amendment for saline soils, using modified biochar-supported salt-tolerant bacteria as its core, combined with pre-wetting solution and gradient concentration cementing solution, can achieve precise control of "carrier-based bacterial fixation → chemical salt regulation → biological consolidation". The porous structure and high specific surface area of ​​the modified biochar provide physical protection and a nutrient microenvironment for the salt-tolerant bacteria, improving their survival rate and activity duration in high-salt soils. The salt-tolerant bacteria are salt-tolerant Bacillus pasteurellii strains, ensuring normal metabolic enzyme and acid production in saline soils, continuously participating in organic matter decomposition and mineralization. Furthermore, the use of gradient concentration spraying cementing solution avoids the initial high concentration's impact on microorganisms and gradually strengthens soil particle consolidation. Biochar adsorbs sodium and chloride ions, while calcium lignosulfonate and polyaspartic acid promote sodium ion leaching. Combined with the buffering effect of calcium carbonate mineralization on soil pH, both soil electrical conductivity and pH decrease. The addition of nitrifying bacteria solution in the later stage accelerates nitrogen conversion and improves ammonium nitrogen utilization.

[0021] like Figure 1 As shown, a method for improving the biochar-supported salt-tolerant bacteria in saline soil specifically includes the following steps: S1, Preparation of modified biochar-supported salt-tolerant bacteria; S1-1, made from corn stalks / rice husks, crushed through a 10-50 mesh sieve; The pulverized raw material is first mixed with (0.4-0.6) mol / L hydrochloric acid at a material-to-water ratio of 1:(12-20) and soaked for 1.5-2.4 h. Then it is heated with (1.8-2.4) mol / L KOH at a ratio of 1:(8-12) in a (70-90)℃ water bath for (18-36) hours to obtain a mixture. The mixture was pyrolyzed and activated to obtain modified biochar; S1-2, prepare a basic culture medium containing yeast extract, ammonium sulfate, and buffer solution, and add trace amounts of Mn and Zn trace elements; Starting with Bacillus pasteurellii, salt-tolerant strains of Bacillus pasteurellii were obtained by gradually increasing the NaCl concentration from 0.5% to 2% to achieve salt tolerance. S1-3, shake the modified biochar solution at a ratio of 1g modified biochar to (5-15)mL of salt-tolerant bacteria to ensure sufficient adsorption and obtain modified biochar loaded with salt-tolerant bacteria; S2, first add the modified biochar loaded with salt-tolerant bacteria to the dry soil and mix evenly, then add the pre-wetting liquid and stir thoroughly to pre-wet the soil, and then spray the cementing liquid in multiple times; after each spray, let it stand for curing at 25-30℃, keeping the soil moist but not waterlogged, until the next spray.

[0022] S3, at least 24 hours after the 5th spray, apply nitrifying bacteria solution to complete the improvement of saline soil with biochar-loaded salt-tolerant bacteria.

[0023] In some examples of the present invention, the preparation method of the cementing solution is as follows: urea and calcium chloride are dissolved in deionized water, and the pH is adjusted to 7.2-7.5; During the first spraying, the cementing solution was a mixture of 0.5 mol / L calcium chloride, 0.5 mol / L urea, and 0.01% w / v rhamnolipid. During the second and third spraying, the cementing solution was mixed with 0.75 mol / L calcium chloride, 0.75 mol / L urea and 0.01% w / v rhamnolipid; During the fourth and fifth spraying, the cementing solution was a mixture of 1 mol / L calcium chloride, 1 mol / L urea, and 0.01% w / v rhamnolipid. Furthermore, the preparation method of the pre-wetting liquid includes: first dissolving calcium lignosulfonate in deionized water, then adding polyaspartic acid, stirring until completely dissolved, and adjusting the pH to 7.0; Furthermore, the nitrifying bacteria solution includes Nitrosomonas and Nitrobacterium, with a total viable count ≥1×10⁻⁶. 8 CFU / mL; Application Timing: After the fifth application of the cementing solution and one day of settling, once the cementation and mineralization have stabilized, dilute the nitrifying bacteria solution to 5 ml per pot with 100 mL of water and evenly irrigate the soil. Applying the nitrifying bacteria solution promotes the conversion of ammonium nitrogen to nitrate nitrogen, reduces ammonia volatilization loss, and improves nitrogen availability. Simultaneously, the H2 produced by nitrification... + It can help lower soil pH. Example 1

[0024] Preparation of modified biochar-supported salt-tolerant bacteria: S1-1, made from corn stalks / rice husks, crushed through a 20-mesh sieve; The pulverized raw material was first mixed with 0.5 mol / L hydrochloric acid at a material-to-water ratio of 1:15 and soaked for 2 hours. Then it was heated with 2 mol / L KOH at a ratio of 1:10 in an 80°C water bath for 24 hours to obtain a mixture. The mixture was pyrolyzed and activated to create pores and prevent contamination. The pyrolysis conditions were 500℃ and oxygen-deficient for 2 hours to obtain pyrolytic char. The pyrolytic char was ground through a 50-mesh sieve and then packaged and stored under sterile conditions to obtain modified biochar. S1-2, prepare a basic culture medium including 20 g / L yeast extract, 10 g / L ammonium sulfate, and 0.13 mol / L Tris buffer, and add trace elements Mn and Zn; Salt tolerance acclimatization: Starting with Bacillus pasteurellii, bacterial culture was inoculated into a culture medium, and the concentration was increased by 0.3-0.5% NaCl each time, gradually up to 2% NaCl. After three consecutive subcultures, salt-tolerant Bacillus pasteurellii strains were induced and screened to obtain salt-tolerant bacteria. The OD600 of salt-tolerant bacteria needs to reach 1.0-1.2, and should be calibrated using the plate count method to ensure a viable bacterial concentration of approximately 10. 8 It can only be used for loading after reaching CFU / mL; S1-3, according to the ratio of 1g modified biochar to 10mL salt-tolerant bacterial solution, shake at 30℃ and about 150rpm for 2 hours to ensure sufficient adsorption, and obtain modified biochar loaded with salt-tolerant bacteria; S1-4, Preparation of pre-wetting solution: First, dissolve 2% w / v calcium lignosulfonate in deionized water, then add 0.5% w / v polyaspartic acid, stir until completely dissolved, and adjust the pH to 7.0. The purity of calcium lignosulfonate is ≥95%, and the molecular weight of polyaspartic acid is approximately 6000. Preparation of cementing solution: 0.5 mol / L calcium chloride, 0.5 mol / L urea and 0.01% w / v rhamnolipid were mixed to form the cementing solution for the first spraying. A mixture of 0.75 mol / L calcium chloride, 0.75 mol / L urea, and 0.01% w / v rhamnolipid was selected as the cementing solution for the second and third spraying processes. A mixture of 1 mol / L calcium chloride, 1 mol / L urea, and 0.01% w / v rhamnolipid was selected as the cementing solution for the fourth and fifth sprayings. S2, calculated per kilogram of dry soil, first mix 30g of modified biochar loaded with salt-tolerant bacteria with 1kg of soil in the top 0-20cm layer, then add 100mL of pre-wetting solution and stir thoroughly to pre-wet the soil. Then spray the cementing solution in 5 applications, with an interval of 24 hours between each application, allowing the solution to fully penetrate into the soil, keeping the soil moist but not waterlogged, until the next application. After the fifth application, allow the soil to stand at 25-30℃ for 48 hours to allow the induced calcium carbonate precipitation to fully form, cementing soil particles and improving aggregate structure. S3. At least 24 hours after the 5th spray, after the cementation and mineralization have basically stabilized, apply nitrifying bacteria solution. Dilute 5 ml of nitrifying bacteria solution per pot to 100 mL of clean water and then evenly irrigate the soil to complete the improvement of the saline soil with biochar-loaded salt-tolerant bacteria. Example 2

[0025] An experiment was conducted to establish a biochar-supported salt-tolerant bacteria amendment for saline soil, with saline soil selected as the test subject; and corresponding modified biochar-supported salt-tolerant bacteria, pre-wetting solution, cementing solution and nitrifying bacteria solution were prepared. The biochar-loaded salt-tolerant bacteria amendment of the saline soil was mixed with the saline soil in the test chamber according to the amendment method. The entire test cycle was 35 days. During the test cycle, the soil moisture content was kept between 15-20%. The test chamber was weighed and water was replenished. The daily ambient temperature was recorded and kept as constant as possible. Soil pH and EC were measured 24 hours after each cementing solution spraying to monitor the biomineralization process and salinity changes in real time.

[0026] After all spraying is completed (e.g., on day 7, day 14, day 28, and day 35), the samples are tested. The biomineralization reaction process will cause a sharp increase in pH, so pH monitoring is carried out. For example, a pH of 9.0 is used as a threshold. When the pH exceeds this threshold, the total amount of cementing solution sprayed is controlled and the spraying interval is extended. The addition of 0.01% w / v rhamnolipin is to improve wetting and distribution. During the spraying operation, it should be sprayed slowly and evenly to avoid uneven distribution of calcium carbonate due to uneven spraying of the cementing liquid, which would affect the strength. Cross-contamination: Instruments from different treatment groups (especially those containing bacteria and those not containing bacteria) should be strictly separated or thoroughly sterilized before use.

[0027] The foregoing description, with reference to preferred embodiments, details an exemplary embodiment of the biochar-supported salt-tolerant bacteria amendment for saline soil proposed in this invention. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the concept of this invention, and various combinations can be made to the various technical features and structures proposed in this invention without exceeding the protection scope of this invention, which is determined by the appended claims.

Claims

1. A soil conditioner for saline-alkali soil with biochar-supported halophilic bacteria, characterized in that, include: Modified biochar loaded with salt-tolerant bacteria, pre-wetted liquid, cementing liquid and nitrifying bacteria liquid; The amount of modified biochar loaded with salt-tolerant bacteria added is 2% to 5% of the dry weight of the soil; The volume ratio of the pre-wetting liquid to every kilogram of soil is (60-200) mL / kg; The volume ratio of the cementing liquid to every kilogram of soil is (30-80) mL / kg; The volume ratio of nitrifying bacteria solution to soil is (1-3.5) mL / kg.

2. The soil conditioner for saline-alkali soil with biochar-supported halophilic bacteria according to claim 1, characterized in that, The amount of modified biochar loaded with salt-tolerant bacteria added was 3% of the dry weight of the soil; The volume of the pre-wetting liquid is 100 mL / kg of soil. The volume ratio of the cementing solution to every kilogram of soil is 50 mL / kg; The volume ratio of nitrifying bacteria solution to soil is 2 mL / kg.

3. The soil conditioner for saline-alkali soil with biochar-supported halophilic bacteria according to claim 1, characterized in that, The modified biochar loaded with salt-tolerant bacteria is obtained by mixing modified biochar and salt-tolerant bacteria. Modified biochar is obtained from corn stalks / rice husks through acid washing activation and pyrolysis activation. Salt-tolerant bacteria are salt-tolerant and domesticated strains of Bacillus pasteurellii.

4. The soil conditioner for saline-alkali soil with biochar-supported halophilic bacteria according to claim 1, characterized in that, The pre-wetting solution is formed by mixing 1%-3.2% w / v calcium lignosulfonate and 0.36%-0.65% w / v polyaspartic acid; or: The pre-wetting solution is a mixture of 1%-3.2% w / v calcium lignosulfonate, 0.03%-0.06% w / v sodium alginate, and 0.3%-0.7% w / v carboxymethyl cellulose.

5. The soil conditioner for saline-alkali soil with biochar-supported halophilic bacteria according to claim 4, characterized in that, The pre-wetting solution comprises 2% w / v calcium lignosulfonate and 0.5% w / v polyaspartic acid; or: The pre-wetting solution includes 2% w / v calcium lignosulfonate, 0.05% w / v sodium alginate, and 0.5% w / v carboxymethyl cellulose.

6. A soil conditioner for biochar-supported halophilic bacteria in saline soil according to any one of claims 1 to 5, characterized in that, The cementing solution is composed of (0.5-1) mol / L calcium chloride, (0.5-1) mol / L urea, and (0.008%-0.011%) w / v rhamnolipid. The nitrifying bacteria solution includes Nitrosomonas and Nitrobacterium, with a total viable count ≥1×10⁻⁶. 8 CFU / mL.

7. A method for improving the biochar loading of halophilic bacteria in saline soil, characterized in that, Specifically, the following steps are included: S1, Preparation of modified biochar-supported salt-tolerant bacteria; S1-1, made from corn stalks / rice husks, crushed through a 10-50 mesh sieve; The pulverized raw material is first mixed with (0.4-0.6) mol / L hydrochloric acid at a material-to-water ratio of 1:(12-20) and soaked for 1.5-2.4 h. Then it is heated with (1.8-2.4) mol / L KOH at a ratio of 1:(8-12) in a (70-90)℃ water bath for (18-36) hours to obtain a mixture. The mixture was pyrolyzed and activated to obtain modified biochar; S1-2, prepare a basic culture medium containing yeast extract, ammonium sulfate, and buffer solution, and add trace amounts of Mn and Zn trace elements; Starting with Bacillus pasteurellii, salt-tolerant strains of Bacillus pasteurellii were obtained by gradually increasing the NaCl concentration from 0.5% to 2% to achieve salt tolerance. S1-3, shake the modified biochar solution at a ratio of 1g modified biochar to (5-15)mL of salt-tolerant bacteria to ensure sufficient adsorption and obtain modified biochar loaded with salt-tolerant bacteria; S2, first add the modified biochar loaded with salt-tolerant bacteria to the dry soil and mix evenly, then add the pre-wetting liquid and stir thoroughly to pre-wet the soil, and then spray the cementing liquid in multiple times; after each spray, let it stand and cure at 25-30℃, keeping the soil moist but not waterlogged, until the next spray. S3, at least 24 hours after the 5th spray, apply nitrifying bacteria solution to complete the improvement of saline soil with biochar-loaded salt-tolerant bacteria.

8. The method for improving the biochar-loaded salt-tolerant bacteria in saline soil according to claim 7, characterized in that, The preparation method of the cementing solution is as follows: urea and calcium chloride are dissolved in deionized water, and the pH is adjusted to 7.2-7.5; In step S2, the cementing solution is sprayed in five stages. In the first spray, the cementing solution is a mixture of 0.5 mol / L calcium chloride, 0.5 mol / L urea and 0.01% w / v rhamnolipid. During the second and third spraying, the cementing solution was mixed with 0.75 mol / L calcium chloride, 0.75 mol / L urea and 0.01% w / v rhamnolipid; During the fourth and fifth spraying, the cementing solution was a mixture of 1 mol / L calcium chloride, 1 mol / L urea, and 0.01% w / v rhamnolipid.

9. The method for improving the biochar-loaded salt-tolerant bacteria in saline soil according to claim 7, characterized in that, In step S1-1, corn stalks / rice husks are used as raw materials and crushed through a 20-mesh sieve. The pulverized raw material was first mixed with 0.5 mol / L hydrochloric acid at a material-to-water ratio of 1:15 and soaked for 2 hours. Then it was heated with 2 mol / L KOH at a ratio of 1:10 in an 80°C water bath for 24 hours to obtain a mixture. The mixture was pyrolyzed and activated under 500°C and oxygen-deficient conditions for 2 hours to obtain pyrolytic char. The pyrolytic char was then ground through a 50-mesh sieve and packaged and stored under aseptic conditions for later use to obtain modified biochar. In steps S1-2, a basic culture medium is prepared comprising 20 g / L yeast extract, 10 g / L ammonium sulfate, and 0.13 mol / L Tris buffer. Start with a NaCl concentration of 0.5%, and increase it by 0.3-0.5% each time, gradually reaching 2% NaCl.

10. The method for improving the biochar-loaded salt-tolerant bacteria in saline soil according to claim 9, characterized in that, The preparation method of the pre-wetting solution includes: first dissolving calcium lignosulfonate in deionized water, then adding polyaspartic acid, stirring until completely dissolved, and adjusting the pH to 7.0.

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