Acidified biochar composite modifier for saline-alkali soil improvement and preparation method of acidified biochar composite modifier

Abstract

The invention discloses an acidified charcoal composite modifier for improving saline-alkali soil and a preparation method thereof, and belongs to the technical field of soil improvement. In order to solve the problems that in the prior art, a traditional saline-alkali soil single improvement material or a simple compounding technology can only aim at a single pain point, and the effect is difficult to last and stabilize, the invention provides an acidified biochar composite modifier for saline-alkali soil improvement. According to the acidified biochar composite modifier, humic acid grafted modified acidified biochar is used as a core salt-reducing alkali-reducing base material, vinasse is used as a fertilizing carrier, a DNA-calcium phosphate composite gel precursor is introduced, natural zeolite and a composite salt-tolerant microbial agent are matched, and a granular product is prepared through a gel granulation process; a synergistic mechanism of targeting adsorption-chemical neutralization-biological synergism-mineralization immobilization is constructed, and the composite material has the advantages of high salt and alkali reduction efficiency, long-acting stability, environmental friendliness and simple preparation.

Description

Technical Field

[0001] This invention belongs to the field of soil improvement technology, and in particular relates to an acidified biochar composite amendment for saline-alkali land improvement and its preparation method. Background Technology

[0002] Saline-alkali soil is a type of soil degraded by salinization, and it is widely distributed globally. Saline-alkali soil is often accompanied by problems such as lack of humus fertilizer sources and low cation exchange capacity, resulting in soil compaction, poor aeration and permeability, and nutrient loss and deficiency, which in turn leads to a decline in crop yield and quality.

[0003] Traditional soil improvement techniques mainly include: First, water conservancy improvement measures, such as irrigation to leach soluble salts and alkalis from the topsoil. However, this requires a large-scale irrigation and drainage system, consuming significant manpower and resources, resulting in high costs. Second, biological improvement measures, through planting. However, coastal wetlands have high salt content, limiting the types of plants that can grow there, and most are non-economic crops, making resource reuse impossible after the plants mature and die. Third, chemical improvement measures. By applying gypsum and other chemical modifiers, free alkali and exchangeable sodium are eliminated, alkalinity is reduced, and physical properties are improved, increasing crop yields. However, while chemical methods are quick to take effect, they are prone to causing secondary pollution.

[0004] Furthermore, traditional single-material improvement techniques or simple compounding technologies often only address specific pain points and are insufficient for long-term, systematic remediation. For example, while acidified biochar can adsorb some sodium ions and regulate pH, its ability to build soil aggregates and its ability to provide sustained nutrient supply are inadequate. Organic wastes such as distiller's grains can supplement carbon sources and stimulate microbial activity, but their loose structure and easy decomposition make it difficult to maintain stable functionality under high saline-alkali stress. Therefore, developing a multifunctional composite system that deeply integrates physical structure reconstruction, chemical ion balance, and biological function activation is key to overcoming the current bottlenecks in saline-alkali land improvement technology. Summary of the Invention

[0005] To address the problem that traditional single-material or simple compounding techniques for improving saline-alkali land can only target a single problem and have limited long-term and stable effects, this invention provides an acidified biochar composite improver for improving saline-alkali land and its preparation method.

[0006] One of the objectives of this invention is to provide an acidified biochar composite amendment for improving saline-alkali land. The acidified biochar composite amendment, by weight, consists of 12-18 parts of humic acid-grafted modified acidified biochar, 10-16 parts of distiller's grains, 0.4-0.7 parts of DNA-calcium phosphate composite gel precursor, 2-4 parts of zeolite, and 0.1-0.2 parts of composite salt-tolerant bacteria agent.

[0007] In a preferred embodiment of the present invention, the acidified biochar composite modifier, by weight, consists of 15 parts of humic acid-grafted modified acidified biochar, 14 parts of distiller's grains, 0.6 parts of DNA-calcium phosphate composite gel precursor, 3 parts of zeolite, and 0.15 parts of composite salt-tolerant bacteria agent.

[0008] In a preferred embodiment of the present invention, the preparation method of the humic acid grafted modified acidified biochar includes the following steps: adding acidified biochar to a humic acid solution with a mass fraction of 8% at a solid-liquid ratio of 1:15, reacting at a constant temperature of 60°C and 120 r / min for 6 h, filtering after the reaction, and drying at 80°C to constant weight to obtain humic acid grafted modified acidified biochar.

[0009] In a preferred embodiment of the present invention, the preparation method of the acidified biochar includes the following steps: crushing corn stalk biochar, passing it through a 100-mesh sieve, adding it to 30% industrial phosphoric acid at a solid-liquid ratio of 1:20, maintaining the temperature at 25°C in a magnetic stirrer, stirring thoroughly for 12 h to allow the biochar and industrial phosphoric acid to fully react, then filtering to separate the phosphoric acid from the biochar, washing repeatedly with deionized water until neutral, and drying in an oven until the weight remains unchanged to obtain acidified biochar.

[0010] In a preferred embodiment of the present invention, the method for preparing the lees includes the following steps: placing fresh lees in a 60°C oven to dry for 12 hours, crushing them, passing them through a 100-mesh sieve, and sealing them for later use.

[0011] In a preferred embodiment of the present invention, the preparation method of the DNA-calcium phosphate composite gel precursor includes the following steps: placing salmon sperm DNA powder in deionized water and dissolving it for 30 min at 37°C and 100 r / min under magnetic stirring to form a DNA aqueous solution with a mass concentration of 0.8%, ensuring that the DNA in the aqueous solution is completely dissolved without precipitation; adding calcium phosphate nanoparticles to the DNA aqueous solution at a weight ratio of 3:1 while stirring at a stirring rate of 150 r / min to obtain a mixture; adjusting the pH of the mixture to 7.0-7.5 using 0.1 mol / L hydrochloric acid or sodium hydroxide solution, and allowing it to stand at 25°C for 2 h to obtain the DNA-calcium phosphate composite gel precursor.

[0012] In a preferred embodiment of the present invention, the method for preparing the zeolite includes the following steps: crushing the zeolite and passing it through a 100-mesh sieve, then sealing it for later use.

[0013] In a preferred embodiment of the present invention, the preparation method of the composite salt-tolerant bacterial agent includes the following steps: S1: Strain activation and pure culture: Nitrogen-fixing bacteria were inoculated into nitrogen-free Assumption liquid medium and cultured at 30°C and 180 rpm with shaking for 24–36 h until the bacterial concentration was ≥5 × 10⁻⁶. 9 CFU / mL; Bacillus megaterium was inoculated into LB liquid medium and cultured with shaking at 30°C and 180 rpm for 18–24 h until the bacterial concentration was ≥8 × 10⁻⁶. 9 CFU / mL; Salt-tolerant actinomycetes were inoculated into modified high-salt Gause I liquid medium and cultured with shaking at 30℃ and 180 rpm for 48-60 h until the bacterial concentration was ≥3×10⁻⁶. 9 CFU / mL; S2: Expanded culture: The activated bacterial cultures of *Azotobacter beyerridis*, *Bacillus megaterium*, and halophilic actinomycetes obtained in S1 were mixed at a viable cell ratio of 2:2:1 to obtain a mixed culture. This mixed culture was inoculated into cooled fermentation medium at a 5% (v / v) inoculum and fermented at 30℃, 200 rpm, and an aeration rate of 1:0.8 (v / v·min) for 48 h. pH was monitored every 6 h, and the pH was adjusted to 7.0-7.5 using sterile acid / alkali solution. The final fermentation concentration was ≥1.0 × 10⁻⁶. 10 CFU / mL; S3: Carrier adsorption and drying / forming: Diatomaceous earth was selected, pulverized through a 200-mesh sieve, sterilized by moist heat at 121℃ for 2 h, and then dried to a moisture content ≤5% to obtain a pretreated diatomaceous earth carrier. 5% (w / v) of the pretreated diatomaceous earth carrier was added to the fermentation endpoint bacterial solution in S2, and the mixture was stirred and adsorbed for 30 min at 25℃ and 100 rpm. The solution was then dried using a spray drying tower with the inlet temperature controlled at 120±5℃, the outlet temperature controlled at 40±2℃, and the feed rate at 10 mL / min to obtain a powdered composite salt-tolerant bacterial agent. The effective viable count of the composite salt-tolerant bacterial agent was ≥2.0×10⁹ CFU / g, the moisture content was ≤8%, and the pH was 7.0-7.5. It was stored in a cool, dry place in a sealed container.

[0014] In a preferred embodiment of the present invention, the composition of the Ashube nitrogen-free liquid culture medium is: 10g glucose, 0.2g KH2PO4, and MgSO4. 0.2 g of 7H2O, 0.2 g of NaCl, 5 g of CaCO3, 1000 mL of distilled water, pH=7.2; The LB liquid culture medium consists of: 10 g tryptone, 5 g yeast extract, 10 g NaCl, 1000 mL distilled water, pH=7.2; The modified high-salt Gause I liquid culture medium consists of: 20 g soluble starch, 1 g KNO3, and K2HPO4. 0.5 g of 3H₂O and MgSO₄ 7H2O 0.5 g, NaCl 100 g, FeSO4 0.01 g of 7H2O, 1000 mL of distilled water, pH=7.4; The fermentation medium consisted of: 20 g glucose, 10 g peptone, 15 g NaCl, 3 g KH2PO4, 1 g MgSO4·7H2O, 5 g CaCO3, 3 g yeast extract, 1000 mL distilled water, and pH=7.2.

[0015] The second objective of this invention is to provide a method for preparing the above-mentioned acidified biochar composite modifier. The preparation method includes the following steps: weighing humic acid-grafted modified acidified biochar, distiller's grains, zeolite, and composite salt-tolerant bacteria agent according to weight parts, placing them in a magnetic stirrer, and stirring at 200 r / min for 30 min to obtain a mixed powder; adding DNA-calcium phosphate composite gel precursor to the mixed powder, with each addition interval of 5 min, and stirring at 150 r / min for 20 min, finally forming a viscous, uniform, non-lumpy, and highly plastic paste slurry, then making small particles with a diameter of 2 mm, spreading them evenly on a tray, placing them in a 37℃ constant temperature and humidity chamber, letting them stand for 40 min, then placing the solidified particles in a 50℃ forced-air drying oven, drying for 8 h, cooling to room temperature, sieving to remove debris, and obtaining the acidified biochar composite modifier.

[0016] Compared with existing technologies, the beneficial effects of this invention are: This invention innovatively constructs a multi-level, multi-target synergistic improvement system. This system uses humic acid-grafted modified acidified biochar as its structural framework and adsorption core. Through dual modification of acidification and humic acid grafting, it significantly enhances its adsorption capacity for Na+. + It possesses specific adsorption capacity and acid-base buffering capacity, while its stable porous carbon network provides a long-lasting water-holding and air-permeable space for the entire system.

[0017] This invention addresses the physical challenges of particle dispersion and structural compaction in saline-alkali soils by introducing a "DNA-calcium phosphate" composite adhesive-targeting system (DNA-calcium phosphate composite gel precursor). This biomimetic material utilizes a network-like complex formed by salmon DNA and calcium phosphate nanoparticles as an "ecological intelligent cementing agent." It precisely acts at the soil micro-interface, promoting the formation of stable aggregates and thus solidifying the soil structure. The slowly released phosphorus and calcium ions also provide nutritional supplementation. To further enhance ion exchange and long-term salt control capabilities, zeolite is added to the system. Its unique porous structure allows beneficial nutrient ions (such as Ca2+) to be released.2+ K + Selective retention of Na + The gradual replacement ensures the stability and sustainability of the desalination process.

[0018] This invention aims to activate and maintain soil ecological functions by integrating fast and slow organic carbon sources and functional microorganisms. Distillers' grains, as highly active and easily degradable organic matter, act as "starting fuel," rapidly stimulating the activity of indigenous and exogenous microorganisms, whose produced organic acids help reduce alkalinity. Biochar and humic acid, on the other hand, serve as a stable carbon pool, ensuring the long-term, slow release of carbon. Finally, a customized composite salt-tolerant bacterial agent colonizes and proliferates in this optimized physicochemical environment, performing key biological functions such as nitrogen fixation, phosphorus solubilization, and secretion of growth-promoting substances, driving the soil micro-ecosystem into a virtuous cycle.

[0019] The core innovation of the acidified biochar composite amendment provided by this invention lies not in the simple stacking of materials, but in the construction of a complete functional chain through the precise design and synergistic interaction of the functions of each component. This chain extends from "nano-micro cementation to improve structure" to "selective adsorption to regulate salinity and alkali" and then to "stepped carbon source-driven bioremediation". The aim is to develop a new composite material that combines efficient salinity and alkali reduction, nutrient supply and soil structure improvement, providing technical support for the resource utilization of saline-alkali land.

[0020] The acidified biochar composite modifier provided by this invention forms an inseparable synergistic system through functional complementarity and mechanistic linkage, as detailed below: (1) Humic acid-grafted modified acidified biochar + DNA-calcium phosphate composite gel precursor: precise salt fixation and long-lasting effect. Humic acid-grafted modified acidified biochar can rapidly capture Na by relying on surface functional groups and porous structure. + OH - The DNA-calcium phosphate composite gel precursor, through the specific recognition of DNA molecular chains, directionally anchors modified biochar to saline-alkali enriched areas, enhancing adsorption efficiency. Its cementing effect also binds the material to soil particles into stable aggregates, preventing the loss of modified biochar and extending the adsorption period. Furthermore, the calcium phosphate releases Ca... 2+ Compatible with Na + The exchange process, combined with biochar adsorption and DNA-calcium phosphate system fixation, forms a complete desalination process.

[0021] (2) Humic acid grafted modified acidified biochar + distiller's grains: carbon source is supplied in a stepwise manner, and nutrients are retained in the distiller's grains as easily degradable organic matter. After being utilized by microorganisms, it produces acid and reduces alkali, while activating microbial activity and accelerating nutrient conversion. The porous structure of humic acid grafted modified acidified biochar can act as a "nutrient reservoir", reducing the rapid leaching of nutrients from the distiller's grains. The humic acid it carries can also combine with the organic components of the distiller's grains to form an "easily degradable + stable" composite carbon pool. The distiller's grains provide a short-term carbon source to start microorganisms, and the biochar provides a long-term carbon source to maintain their activity, thus providing continuous energy for the micro-ecology.

[0022] (3) Humic acid grafted modified acidified biochar + zeolite: a combination of fast and slow, continuous salt control. Modified biochar has a large number of adsorption sites, which can quickly adsorb high concentrations of salt and alkali ions to achieve initial salt and alkali reduction; since single biochar has the problem of adsorption saturation, the gradual ion exchange performance of zeolite can replace Na for a long time. + and release Ca 2+ K + The modified biochar absorbs beneficial ions, compensating for this shortcoming. Simultaneously, the modified biochar adsorbs nutrients released by zeolite, enabling slow release. The porous network constructed by both also improves soil aeration and water retention, enhancing its physical structure.

[0023] (4) Composite salt-tolerant bacteria agent + other components: Microecological activation, bidirectional enhancement of the colonization and function of composite salt-tolerant bacteria agent, relying on the synergistic support of each component: Humic acid grafted modified acidified biochar provides a "shelter" to avoid high salt, and the lees and zeolite supply nutrients. The "DNA-calcium phosphate" system stabilizes the microenvironment; while the metabolic activity of the bacteria agent also enhances the material performance in reverse: acid production activates the adsorption and exchange functions of modified biochar and zeolite, while nitrogen fixation and nitrogen supplementation, phosphorus solubilization and efficiency improvement, forming a virtuous cycle of "protection-supply-enhancement".

[0024] (5) Overall synergy: "Modified biochar + zeolite" achieves rapid reduction and long-term maintenance of salinity through "rapid adsorption + continuous exchange". The "DNA-calcium phosphate" system improves the accuracy of action and improves soil structure through "targeted anchoring + structural cementation". "Distillers' grains + compound salt-tolerant bacteria agent" activates the micro-ecology and improves fertility through "carbon source supply + biological function". Finally, through the multi-dimensional linkage of "targeted salt fixation - chemical alkali reduction - ion replacement - structural improvement - biological enhancement", the systemic and long-term improvement of saline-alkali land is achieved, rather than the short-term improvement of a single indicator.

[0025] The acidified biochar composite amendment provided by this invention not only realizes the high-value utilization of agricultural waste (corn stalks, distiller's grains) and natural minerals (zeolite), but also establishes a complete functional chain of "nano-micro structure reshaping - salt and alkali ion targeted regulation - tiered carbon source driving - functional microbial colonization", and achieves both "symptomatic and radical treatment" of saline-alkali obstacles and long-term cultivation of soil health. Attached Figure Description

[0026] Figure 1 This is a graph showing the dynamic response of soil pH. Figure 2 This is a graph showing the dynamic response changes in soil electrical conductivity. Figure 3 This is a graph showing the dynamic response changes in soil organic matter content. Figure 4 This is a graph showing the dynamic response changes in available phosphorus content in the soil. Figure 5 This is a graph showing the dynamic response changes in soil ammonium nitrogen content. Figure 6 This is a graph showing the dynamic response changes in soil nitrate nitrogen content. Detailed Implementation

[0027] Those skilled in the art can refer to the content of this document and appropriately improve the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can obviously make modifications or appropriate alterations and combinations to the methods and applications described herein without departing from the content and scope of this invention to implement and apply the technology of this invention.

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0029] The nitrogen-fixing bacteria used in the following examples Azotobacter beijerinckii Purchased from the China General Microbiological Culture Collection Center, accession number CGMCC 1.9044; Bacillus megaterium Bacillus megaterium Purchased from the China General Microbiological Culture Collection Center, accession number CGMCC 1.10466; Salt-tolerant actinomycetes Streptomyces rochei Purchased from China General Microbiological Culture Collection Center, accession number CGMCC No. 30450.

[0030] Example 1: 1. Preparation of humic acid-grafted modified acidified biochar: Corn stalk biochar was crushed, passed through a 100-mesh sieve, and added to 30% industrial phosphoric acid at a solid-liquid ratio of 1:20. The mixture was stirred at 25℃ in a magnetic stirrer for 12 h to allow the biochar and industrial phosphoric acid to react fully. After stirring, the mixture was filtered to separate the phosphoric acid from the biochar. The biochar was washed several times with deionized water until neutral and dried in an oven until the weight remained constant to obtain acidified biochar. The acidified biochar was then added to an 8% humic acid solution at a solid-liquid ratio of 1:15 and reacted at 60℃ and 120 r / min under constant temperature shaking conditions for 6 h. After the reaction was completed, the mixture was filtered and dried at 80℃ to constant weight to obtain humic acid-grafted modified acidified biochar.

[0031] 2. Preparation of lees: Fresh lees obtained from the brewery are dried in an oven at 60℃ for 12 hours, crushed and passed through a 100-mesh sieve, and then sealed for later use.

[0032] 3. Preparation of DNA-calcium phosphate composite gel precursor: Salmon sperm DNA powder was placed in deionized water and dissolved for 30 min at 37℃ and 100 r / min under magnetic stirring to form a DNA aqueous solution with a mass concentration of 0.8%, ensuring that the DNA in the aqueous solution was completely dissolved without precipitation; calcium phosphate nanoparticles were added to the DNA aqueous solution at a weight ratio of 3:1 while stirring at a stirring rate of 150 r / min to obtain a mixture; the pH value of the mixture was adjusted to 7.0-7.5 using 0.1 mol / L hydrochloric acid or sodium hydroxide solution, and the mixture was allowed to stand at 25℃ for 2 h to obtain the DNA-calcium phosphate composite gel precursor.

[0033] 4. Preparation of zeolite: Purchase natural clinoptilolite ore, crush it, pass it through a 100-mesh sieve, and seal it for later use.

[0034] 5. Preparation of compound salt-tolerant bacterial agents: S1: Strain activation and pure culture: *Azotobacter beyeris* was inoculated onto Assumption nitrogen-free liquid medium (the composition of Assumption nitrogen-free liquid medium was: 10 g glucose, 0.2 g KH₂PO₄, MgSO₄). The bacterial culture was prepared by shaking at 30℃ and 180 rpm for 24-36 h with 0.2 g of 7H2O, 0.2 g of NaCl, 5 g of CaCO3, and 1000 mL of distilled water (pH=7.2) until the bacterial concentration reached ≥5×10⁻⁶. 9 CFU / mL; Bacillus megaterium was inoculated into LB liquid medium (LB liquid medium composition: 10 g tryptone, 5 g yeast extract, 10 g NaCl, 1000 mL distilled water, pH=7.2) and cultured with shaking at 30℃ and 180 rpm for 18-24 h until the bacterial concentration was ≥8×10⁻⁶. 9 CFU / mL; Salt-tolerant actinomycetes were inoculated into modified high-salt Gause I liquid medium (the composition of modified high-salt Gause I liquid medium is: 20 g soluble starch, 1 g KNO3, and K2HPO4). 0.5 g of 3H₂O and MgSO₄ 7H2O 0.5 g, NaCl100 g, FeSO4 In a culture containing 0.01 g of 7H2O and 1000 mL of distilled water (pH=7.4), incubate at 30℃ and 180 rpm with shaking for 48-60 h until the bacterial concentration is ≥3×10⁻⁶. 9 CFU / mL; S2: Scale-up culture: The activated bacterial solutions of *Azotobacter beyeris*, *Bacillus megaterium*, and salt-tolerant actinomycetes obtained in S1 were mixed at a viable cell ratio of 2:2:1 to obtain a mixed culture. The mixed culture was inoculated at a rate of 5% (v / v) into the cooled fermentation medium (the composition of the fermentation medium is: 20 g glucose, 10 g peptone, 15 g NaCl, 3 g KH2PO4, 1 g MgSO4·7H2O, 5 g CaCO3, 3 g yeast extract, 1000 mL distilled water, pH=7.2). Fermentation was carried out at 30℃, 200 rpm, and an aeration rate of 1:0.8 (v / v·min) for 48 h. During this period, the pH was measured every 6 h, and the pH was adjusted to 7.0-7.5 using sterile acid / alkali solution. The total bacterial concentration at the end of fermentation was ≥1.0×10⁻⁶. 10 CFU / mL; S3: Carrier Adsorption and Drying: Diatomaceous earth was selected, pulverized through a 200-mesh sieve, sterilized by moist heat at 121℃ for 2 h, and then dried until the moisture content was ≤5% to obtain a pretreated diatomaceous earth carrier. 5% (w / v) of the pretreated diatomaceous earth carrier was added to the fermentation endpoint bacterial solution in S2, and the mixture was stirred and adsorbed for 30 min at 25℃ and 100 rpm. Drying was then carried out using a spray drying tower, with the inlet temperature controlled at 120±5℃, the outlet temperature controlled at 40±2℃, and the feed rate at 10 mL / min, to obtain a powdered composite salt-tolerant bacterial agent. The total effective viable count of the composite salt-tolerant bacterial agent was ≥2.0×10⁻⁶. 9 CFU / g, moisture content ≤8%, pH=7.0-7.5, store in a cool, dry place in a sealed container.

[0035] 6. Preparation of an acidified biochar composite amendment for saline-alkali land improvement: Weigh out 15 parts by weight of the above-mentioned humic acid-grafted modified acidified biochar, 14 parts of distiller's grains, 3 parts of zeolite, and 0.15 parts of the composite salt-tolerant bacterial agent. Place them in a magnetic stirrer and stir for 30 min at 200 r / min to obtain a powder mixture. Add 0.6 parts of the above-mentioned DNA-calcium phosphate composite gel precursor (composed of 0.45 parts of salmon DNA and 0.15 parts of calcium phosphate nanoparticles) to the powder mixture, with each addition at 5 min intervals. Stir at 150 r / min for 20 min until a viscous, uniform, lump-free, and highly plastic paste is formed. Then, make small particles with a diameter of 2 mm, spread them evenly on a tray, and place them in a 37℃ constant temperature and humidity chamber. After standing for 40 min, place the solidified particles in a 50℃ forced-air drying oven and dry for 8 minutes. h, after cooling to room temperature, the residue is removed by sieving to obtain acidified biochar composite modifier, abbreviated as T6 (humic acid grafted modified acidified biochar + distiller's grains + DNA-calcium phosphate composite gel precursor + zeolite + composite salt-tolerant bacteria agent).

[0036] Comparative Example 1: The composite modifier prepared in this comparative example consists only of acidified biochar, and is referred to as T1.

[0037] The preparation steps of the acidified biochar are as follows: crush corn stalk biochar, pass it through a 100-mesh sieve, add it to 30% industrial phosphoric acid at a solid-liquid ratio of 1:20, maintain the temperature at 25°C in a magnetic stirrer, stir thoroughly for 12 h to allow the biochar and industrial phosphoric acid to react fully, filter to separate the phosphoric acid and biochar, wash repeatedly with deionized water until neutral, and dry in an oven until the weight remains unchanged to obtain acidified biochar.

[0038] Comparative Example 2: The composite modifier prepared in this comparative example consists of acidified biochar and distiller's grains, and is referred to as T2 (acidified biochar + distiller's grains).

[0039] The preparation steps of the acidified biochar are as follows: crush corn stalk biochar, pass it through a 100-mesh sieve, add it to 30% industrial phosphoric acid at a solid-liquid ratio of 1:20, maintain the temperature at 25°C in a magnetic stirrer, stir thoroughly for 12 h to allow the biochar and industrial phosphoric acid to react fully, filter to separate the phosphoric acid and biochar, wash repeatedly with deionized water until neutral, and dry in an oven until the weight remains unchanged to obtain acidified biochar.

[0040] The preparation steps of the lees are as follows: fresh lees obtained from the brewery are placed in a 60℃ oven and dried for 12 hours, then crushed and passed through a 100-mesh sieve, and sealed for later use.

[0041] Comparative Example 3: The composite modifier prepared in this comparative example consists of acidified biochar, distiller's grains, and DNA-calcium phosphate composite gel precursor, and is referred to as T3 (acidified biochar + distiller's grains + DNA-calcium phosphate composite gel precursor).

[0042] The preparation steps of the acidified biochar are as follows: crush corn stalk biochar, pass it through a 100-mesh sieve, add it to 30% industrial phosphoric acid at a solid-liquid ratio of 1:20, maintain the temperature at 25°C in a magnetic stirrer, stir thoroughly for 12 h to allow the biochar and industrial phosphoric acid to react fully, filter to separate the phosphoric acid and biochar, wash repeatedly with deionized water until neutral, and dry in an oven until the weight remains unchanged to obtain acidified biochar.

[0043] The preparation steps of the lees are as follows: fresh lees obtained from the brewery are placed in a 60℃ oven and dried for 12 hours, then crushed and passed through a 100-mesh sieve, and sealed for later use.

[0044] The preparation steps of the DNA-calcium phosphate composite gel precursor are as follows: salmon sperm DNA powder is placed in deionized water and dissolved for 30 min at 37℃ and 100 r / min under magnetic stirring to form a DNA aqueous solution with a mass concentration of 0.8%, ensuring that the DNA in the aqueous solution is completely dissolved without precipitation; calcium phosphate nanoparticles are added to the DNA aqueous solution at a weight ratio of 3:1 while stirring at a stirring rate of 150 r / min to obtain a mixture; the pH value of the mixture is adjusted to 7.0-7.5 using 0.1 mol / L hydrochloric acid or sodium hydroxide solution, and the mixture is allowed to stand at 25℃ for 2 h to obtain the DNA-calcium phosphate composite gel precursor.

[0045] Comparative Example 4: The composite modifier prepared in this comparative example consists of acidified biochar, distiller's grains, and a composite salt-tolerant bacteria agent, and is referred to as T4 (acidified biochar + distiller's grains + composite salt-tolerant bacteria agent).

[0046] The preparation steps of the acidified biochar are as follows: crush corn stalk biochar, pass it through a 100-mesh sieve, add it to 30% industrial phosphoric acid at a solid-liquid ratio of 1:20, maintain the temperature at 25°C in a magnetic stirrer, stir thoroughly for 12 h to allow the biochar and industrial phosphoric acid to react fully, filter to separate the phosphoric acid and biochar, wash repeatedly with deionized water until neutral, and dry in an oven until the weight remains unchanged to obtain acidified biochar.

[0047] The preparation steps of the lees are as follows: fresh lees obtained from the brewery are placed in a 60℃ oven and dried for 12 hours, then crushed and passed through a 100-mesh sieve, and sealed for later use.

[0048] The preparation steps of the composite salt-tolerant bacterial agent are the same as in Example 1.

[0049] Comparative Example 5: The difference between this comparative example and Example 1 is that the humic acid-grafted modified acidified biochar in the acidified biochar composite modifier is replaced with acidified biochar. The other steps are the same as in Example 1. The prepared composite modifier is referred to as T5 (acidified biochar + distiller's grains + DNA-calcium phosphate composite gel precursor + zeolite + composite salt-tolerant bacteria agent).

[0050] The preparation steps of the acidified biochar are as follows: crush corn stalk biochar, pass it through a 100-mesh sieve, add it to 30% industrial phosphoric acid at a solid-liquid ratio of 1:20, maintain the temperature at 25°C in a magnetic stirrer, stir thoroughly for 12 h to allow the biochar and industrial phosphoric acid to react fully, filter to separate the phosphoric acid and biochar, wash repeatedly with deionized water until neutral, and dry in an oven until the weight remains unchanged to obtain acidified biochar.

[0051] Effect Experiment: 1. The saline-alkali soil used in this experiment was taken from Bayannur Sumu, Horqin Right Wing Middle Banner, Xing'an League, Inner Mongolia Autonomous Region. The sampled soil has typical salinization characteristics. Soil samples were taken at a depth of 0-20 cm and stored in a refrigerator at 4℃ after being brought back to the laboratory. The physicochemical properties of the saline-alkali soil are shown in Table 1.

[0052] Table 1

[0053] 2. Indoor potted plant experiment: The potted plant experiment used plastic flower pots, with a soil mass of 1 kg per pot. The soil was air-dried and pretreated by passing it through a 2 mm sieve. Three parallel replicates were set up for each treatment.

[0054] The acidified biochar composite amendment (T6) prepared in Example 1 and the composite amendments (T1-5) prepared in Comparative Examples 1-5 were used as a control group (CK) without the application of the composite amendment. They were applied to the surface of the soil in the flower pots at an application rate of 2 tons / acre and stirred evenly to ensure that the amendment was fully mixed with the soil.

[0055] 3. Soil physicochemical property determination: Soil samples from flowerpots in each treatment were collected on day 56 of the experiment to determine the main physicochemical properties. The measured indicators included: soil pH, electrical conductivity, organic matter, available phosphorus, ammonium nitrogen, and nitrate nitrogen content, in order to evaluate the effect of acidified biochar composite material used for saline-alkali land improvement on soil physicochemical properties.

[0056] Dynamic changes in soil pH as follows Figure 1As shown, the pH of the control group was 9.16, while the soil pH of the treatment groups T1 to T6 decreased continuously (T1 was 8.72, T6 was 7.53). In particular, the acidification biochar composite amendment provided by this invention, which contains DNA-calcium phosphate composite gel precursor, composite bacterial agent and humic acid grafted modified acidification biochar, showed a more significant effect in reducing alkalinity. It can be seen that the components of the acidification biochar composite amendment provided by this invention enhance the ability to regulate salt and alkali ions through targeted adsorption, bio-enhancing and other synergistic effects.

[0057] Dynamic changes in soil electrical conductivity, such as Figure 2 As shown, the electrical conductivity gradually decreased from 626 μs / cm in the control group to 417 μs / cm in the T6 group, a decrease of 33.4%. The data indicate that single or partial components can only achieve limited salt reduction, while the full-component combination of humic acid-grafted acidified biochar, distiller's grains, DNA-calcium phosphate composite gel precursor, and composite salt-tolerant bacteria agent achieves efficient and deep reduction of soil salinity through multi-dimensional synergistic effects of "physical adsorption-chemical neutralization-biotransformation-structural fixation".

[0058] The dynamic response changes of soil organic matter content are as follows: Figure 3 As shown, the organic matter content increased from 24.7 g / kg in the control group to 38.8 g / kg in T6, exhibiting a gradual and significant upward trend, with T6 reaching the highest value, an increase of approximately 57.1% compared to the control group. The results indicate that the increase in organic matter not only depends on exogenous addition (distillers' grains), but also benefits from the synergistic effect of structural stability (DNA-calcium phosphate composite gel precursor), biotransformation (composite salt-tolerant bacterial agent), and adsorption retention (humic acid-grafted acidified biochar). The soil treated with T6 had the highest organic matter content, further validating the integrity and necessity of the whole-component system in improving soil fertility.

[0059] The dynamic response of soil available phosphorus content changes as follows Figure 4 As shown, the available phosphorus content in the control group was 13.29 mg / kg, while the available phosphorus content in the soil of the treatment groups T1 to T6 gradually increased (T1 was 27.2 mg / kg, and T6 was 48.7 mg / kg). The results indicate that the increase in available phosphorus content is the result of a synergistic effect of "chemical phosphorus supply—biological phosphorus release—structural phosphorus retention." The acidified biochar composite amendment provided by this invention achieves a dual synergistic effect of exogenous addition and endogenous activation, further verifying the systemic functional advantages of this composite amendment in simultaneously addressing salinity and nutrient deficiencies.

[0060] Dynamic changes in soil ammonium nitrogen content, as follows Figure 5As shown, the ammonium nitrogen content in the control group was 21.6 mg / kg, while the soil ammonium nitrogen content in the treatment groups T1 to T6 gradually increased (T1 was 26.5 mg / kg, and T6 was 48.7 mg / kg). This indicates that the increase in ammonium nitrogen mainly relies on the synergy of biological nitrogen fixation and chemical protection. The acidified biochar composite amendment provided by this invention achieves a highly efficient nitrogen cycle from "conversion" to "fixation".

[0061] The dynamic response of soil nitrate nitrogen content as follows Figure 6 As shown, the nitrate nitrogen content gradually increased from 11.6 mg / kg in the control group to 18.5 mg / kg in T6, an increase of approximately 59.5%. This indicates that the accumulation of nitrate nitrogen depends on the synergy of "structural protection-microbial transformation-organic adsorption". The acidified biochar composite amendment provided by this invention exhibits the best synergy in promoting the effective transformation and maintenance of nitrogen forms, further confirming the overall activation and stabilization effect of this amendment on the soil nutrient system.

[0062] The specific embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. An acidified biochar composite conditioner for improving saline-alkali land, characterized in that, The acidified biochar composite modifier, by weight, consists of 12-18 parts of humic acid-grafted modified acidified biochar, 10-16 parts of distiller's grains, 0.4-0.7 parts of DNA-calcium phosphate composite gel precursor, 2-4 parts of zeolite, and 0.1-0.2 parts of composite salt-tolerant bacteria agent.

2. The acidified biochar composite modifier according to claim 1, characterized in that, The acidified biochar composite modifier, by weight, consists of 15 parts of humic acid-grafted modified acidified biochar, 14 parts of distiller's grains, 0.6 parts of DNA-calcium phosphate composite gel precursor, 3 parts of zeolite, and 0.15 parts of composite salt-tolerant bacteria agent.

3. The acidified biochar composite modifier according to claim 1, characterized in that, The preparation method of the humic acid grafted modified acidified biochar includes the following steps: adding acidified biochar to a humic acid solution with a mass fraction of 8% at a solid-liquid ratio of 1:15, reacting at a constant temperature of 60℃ and 120 r / min for 6 h, filtering after the reaction, and drying at 80℃ to constant weight to obtain humic acid grafted modified acidified biochar.

4. The acidified biochar composite modifier according to claim 3, characterized in that, The preparation method of the acidified biochar includes the following steps: crushing corn stalk biochar, passing it through a 100-mesh sieve, adding it to 30% industrial phosphoric acid at a solid-liquid ratio of 1:20, maintaining the temperature at 25°C in a magnetic stirrer, stirring thoroughly for 12 hours to allow the biochar and industrial phosphoric acid to fully react, then filtering to separate the phosphoric acid from the biochar, washing repeatedly with deionized water until neutral, and drying in an oven until the weight remains unchanged to obtain acidified biochar.

5. The acidified biochar composite modifier according to claim 1, characterized in that, The method for preparing the lees includes the following steps: placing fresh lees in a 60°C oven to dry for 12 hours, crushing them, passing them through a 100-mesh sieve, and sealing them for later use.

6. The acidified biochar composite modifier according to claim 1, characterized in that, The method for preparing DNA-calcium phosphate complex gel precursor includes the following steps: Salmon DNA powder was placed in deionized water and dissolved for 30 min at 37°C and 100 r / min with magnetic stirring to form a DNA aqueous solution with a mass concentration of 0.8%, ensuring that the DNA was completely dissolved without precipitation. Calcium phosphate nanoparticles were added to the DNA aqueous solution at a weight ratio of 3:1 while stirring at a rate of 150 r / min to obtain a mixture. The pH of the mixture was adjusted to 7.0-7.5 using 0.1 mol / L hydrochloric acid or sodium hydroxide solution, and the mixture was allowed to stand at 25°C for 2 h to obtain the DNA-calcium phosphate composite gel precursor.

7. The acidified biochar composite modifier according to claim 1, characterized in that, The method for preparing the zeolite includes the following steps: crushing the zeolite and passing it through a 100-mesh sieve, then sealing it for later use.

8. The acidified biochar composite modifier according to claim 1, characterized in that, The preparation method of the composite salt-tolerant bacterial agent includes the following steps: S1: Strain activation and pure culture: Nitrogen-fixing bacteria were inoculated into nitrogen-free Assumption liquid medium and cultured at 30°C and 180 rpm with shaking for 24-36 hours until the bacterial concentration was ≥5×10⁻⁶. 9 CFU / mL; Bacillus megaterium was inoculated into LB liquid medium and cultured with shaking at 30°C and 180 rpm for 18-24 h until the bacterial concentration was ≥8×10⁻⁶. 9 CFU / mL; Salt-tolerant actinomycetes were inoculated into modified high-salt Gause I liquid medium and cultured with shaking at 30℃ and 180 rpm for 48-60 h until the bacterial concentration was ≥3×10⁻⁶. 9 CFU / mL; S2: Expanded culture: The activated bacterial cultures of *Azotobacter beyerridis*, *Bacillus megaterium*, and halophilic actinomycetes obtained in S1 were mixed at a viable cell ratio of 2:2:1 to obtain a mixed culture. This mixed culture was inoculated into cooled fermentation medium at a 5% (v / v) inoculum and fermented at 30℃, 200 rpm, and an aeration rate of 1:0.8 (v / v·min) for 48 h. pH was monitored every 6 h, and the pH was adjusted to 7.0-7.5 using sterile acid / alkali solution. The final fermentation concentration was ≥1.0 × 10⁻⁶. 10 CFU / mL; S3: Carrier adsorption and drying / forming: Diatomaceous earth was selected, pulverized through a 200-mesh sieve, and sterilized by moist heat at 121℃ for 2 h, then dried until the moisture content was ≤5% to obtain a pretreated diatomaceous earth carrier. 5% (w / v) of the pretreated diatomaceous earth carrier was added to the fermentation endpoint bacterial solution in S2, and the mixture was stirred and adsorbed for 30 min at 25℃ and 100 rpm. Drying was then carried out using a spray drying tower, with the inlet temperature controlled at 120±5℃, the outlet temperature controlled at 40±2℃, and the feed rate at 10 mL / min, to obtain a powdered composite salt-tolerant bacterial agent. The total effective viable count of the composite salt-tolerant bacterial agent was ≥2.0×10⁻⁶. 9 CFU / g, moisture content ≤8%, pH=7.0-7.5, store in a cool, dry place in a sealed container.

9. The acidified biochar composite modifier according to claim 8, characterized in that, The composition of the Ashube nitrogen-free liquid culture medium is: 10 g glucose, 0.2 g KH2PO4, and MgSO4. 0.2 g of 7H2O, 0.2 g of NaCl, 5 g of CaCO3, 1000 mL of distilled water, pH=7.2; The composition of the LB liquid culture medium is: 10 g tryptone, 5 g yeast extract, 10 g NaCl, 1000 mL distilled water, pH=7.2; The modified high-salt Gause I liquid culture medium consists of: 20 g soluble starch, 1 g KNO3, and K2HPO4. 0.5 g of 3H₂O and MgSO₄ 7H2O 0.5 g, NaCl 100 g, FeSO4 0.01 g of 7H2O, 1000 mL of distilled water, pH=7.4; The fermentation medium consisted of: 20 g glucose, 10 g peptone, 15 g NaCl, 3 g KH2PO4, 1 g MgSO4·7H2O, 5 g CaCO3, 3 g yeast extract, 1000 mL distilled water, and pH=7.

2.

10. A method for preparing the acidified biochar composite modifier according to any one of claims 1 to 9, characterized in that, The preparation method includes the following steps: Weigh out the humic acid-grafted modified acidified biochar, distiller's grains, zeolite, and composite salt-tolerant bacteria agent according to the specified weight parts. Place them in a magnetic stirrer and stir for 30 min at 200 r / min to obtain a powder mixture. Add the DNA-calcium phosphate composite gel precursor to the powder mixture, with each addition at 5 min intervals. Stir at 150 r / min for 20 min until a viscous, uniform, lump-free, and highly plastic paste is formed. Then, make small particles with a diameter of 2 mm, spread them evenly on a tray, and place them in a 37℃ constant temperature and humidity chamber. After standing for 40 min, place the solidified particles in a 50℃ forced-air drying oven and dry for 8 h. After cooling to room temperature, sieve to remove the debris to obtain the acidified biochar composite modifier.

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