Biochar-based soil amendment for saline-alkali soil and application thereof

Abstract

The application discloses a soil modifier for saline-alkali soil based on biochar and application, and belongs to the technical field of saline-alkali soil improvement. The soil modifier is composed of the following components in parts by weight: 40-45 parts of saline-alkali improvement biochar, 18-20 parts of mature organic fertilizer, 4-5 parts of water-retaining agent and 4-5 parts of saline-alkali resistant microbial gel beads; the saline-alkali improvement biochar is prepared from biochar material through pyrolysis, nano solution soaking and composite enzyme solution crosslinking; and the saline-alkali resistant microbial gel beads are prepared by mixing microbial liquid and embedding liquid and then dropping into a calcium chloride solution. The soil modifier prepared by the application has a remarkable effect on soil salt removal and soil pH value improvement, and can be applied in secondary saline-alkali soil in irrigated agricultural areas.

Description

Technical Field

[0001] This invention belongs to the field of saline-alkali land improvement technology, specifically relating to biochar-based soil conditioners for saline-alkali land and their applications. Background Technology

[0002] Soil salinization has become a serious global problem threatening agricultural production, food security, and sustainable ecological development. Due to the scarcity of freshwater resources, low-lying terrain, and high groundwater levels, saline-alkali lands face extreme difficulties in desalination, leading to a series of problems such as declining soil fertility, hindered crop growth, and fragile ecological environments. These issues severely restrict regional agricultural and forestry development and urbanization.

[0003] The formation mechanism of saline-alkali land is complex, influenced by a variety of natural and anthropogenic factors. Natural factors include arid climates and high evaporation rates, causing soil salts to rise with water and accumulate on the surface; salt-rich parent materials gradually exhibit salinization characteristics over long-term soil formation; and low-lying terrain and poor drainage hinder salt leaching, further exacerbating soil salinization. Anthropogenic factors include improper irrigation methods, such as flood irrigation, which raise the water table and promote salt accumulation on the soil surface; and long-term excessive application of chemical fertilizers, which alters the soil's chemical properties and increases salinity. Furthermore, severe vegetation destruction in some areas, resulting in the loss of surface cover and protection, intensifies soil moisture evaporation, leading to increased salt concentration and accelerating the salinization process.

[0004] Currently, methods for improving saline-alkali land mainly encompass physical, chemical, and engineering measures. Physical improvement measures include land leveling, deep tillage, and irrigation / drainage for salt leaching. Land leveling can eliminate localized salt accumulation and make salt distribution relatively uniform; deep tillage breaks up the plow pan, improving soil aeration and permeability, which facilitates salt leaching. Irrigation / drainage dissolves salt in the soil through irrigation water and drains it out, but this method consumes a large amount of water and is difficult to implement on a large scale in areas with scarce freshwater resources. Chemical improvement methods often use chemicals such as gypsum, ferrous sulfate, and sulfur powder. Calcium ions in gypsum can replace sodium ions on soil colloids, reducing the sodium adsorption ratio of the soil and improving soil structure; ferrous sulfate and sulfur powder, after oxidation in the soil, can produce acidic substances that neutralize soil alkalinity and lower the soil pH. However, long-term use of chemical amendments may cause soil compaction, environmental pollution, and some amendments are expensive. Engineering improvement measures include constructing terraced fields and strip fields, and installing underground drainage systems. Constructing terraced fields and strip fields can raise the ground level, lower the groundwater level, and reduce the impact of salt on crop roots; underground drainage systems can effectively remove excess water and salt from the soil, but the construction cost is high and the maintenance is difficult.

[0005] Therefore, the purpose of this invention is to provide a biochar-based soil conditioner for saline-alkali land and its application, in order to solve the technical problems in the prior art where biochar alone is highly alkaline, has insufficient salt adsorption capacity, and has limited effect on improving saline-alkali soil, and cannot synergistically improve the soil's physical and chemical properties and microbial ecology. Summary of the Invention

[0006] The purpose of this invention is to provide a biochar-based soil conditioner for saline-alkali land and its application, in order to solve the technical problems in the prior art where biochar alone is highly alkaline, has insufficient salt adsorption capacity, and has limited effect on improving saline-alkali soil, and cannot synergistically improve the physical and chemical properties of soil and microbial ecology.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A biochar-based soil conditioner for saline-alkali land comprises the following components by weight: 40-45 parts saline-alkali improved biochar, 18-20 parts well-rotted organic fertilizer, 4-5 parts water-retaining agent, and 4-5 parts salt-alkali tolerant microbial gel beads; wherein the saline-alkali improved biochar is prepared by pyrolysis, nano-solution soaking, and cross-linking with a composite enzyme solution; the water-retaining agent is obtained by mixing polyacrylamide and carboxymethyl cellulose in equal mass; and the salt-alkali tolerant microbial gel beads are prepared by adding a mixture of microbial inoculum and encapsulation solution to a calcium chloride solution.

[0009] The nano-solution comprises a mixture of nano-ferric oxide solution, nano-silica solution, nano-calcium carbonate solution, and nano-montmorillonite solution; the volume ratio of the nano-ferric oxide solution, nano-silica solution, nano-calcium carbonate solution, and nano-montmorillonite solution is 2:2:2-3:3; the concentration of the nano-ferric oxide solution is 2-3 g / L, the concentration of the nano-silica solution is 7-8 g / L, the concentration of the nano-calcium carbonate solution is 6-8 g / L, and the concentration of the nano-montmorillonite solution is 8-9 g / L.

[0010] The complex enzyme solution is prepared by mixing laccase phosphate buffer, manganese peroxidase phosphate buffer, and halophilic alkaline protease phosphate buffer, wherein the volume ratio of laccase phosphate buffer, manganese peroxidase phosphate buffer, and halophilic alkaline protease phosphate buffer is 50-55:33-37:12-15, the concentration of laccase phosphate buffer is 8-10 U / mL, the concentration of manganese peroxidase phosphate buffer is 5-7 U / mL, and the concentration of halophilic alkaline protease phosphate buffer is 4-5 U / mL.

[0011] Furthermore, the preparation method of saline-alkali modified biochar includes the following steps:

[0012] S1. The biochar material is crushed, washed, dried, and pyrolyzed to obtain raw biochar; the raw biochar is soaked in a nano solution, sonicated, and pyrolyzed a second time to obtain nano biochar.

[0013] S2. Mix the composite enzyme solution with the chitosan solution, add glutaraldehyde solution for cross-linking, then add nano-biochar, stir the reaction, wash, and dry to obtain salt-alkali modified biochar.

[0014] Preferably, the biochar material in S1 includes one or more of corn stalks, sawdust, and rice husks; the particle size of the pulverized biochar material is 2-5 mm, the pyrolysis temperature is 500-700℃, the pyrolysis time is 2-4 h, the ultrasonic time is 1-2 h, the secondary pyrolysis temperature is 200-300℃, and the secondary pyrolysis time is 1-2 h.

[0015] Preferably, in S2, the concentration of chitosan solution is 1-3 wt%, the concentration of glutaraldehyde solution is 2-2.5 wt%, and the ratio of the amount of composite enzyme solution, chitosan solution, glutaraldehyde solution and nano-biochar is (35-50) mL: (1-2) mL: (0.1-0.2) mL: 1 g; the stirring speed is 100-150 rpm, the stirring time is 2-4 h; the drying temperature is 30-40℃, and the drying time is 12-24 h.

[0016] Furthermore, the preparation method of salt- and alkali-tolerant microbial gel beads includes the following steps:

[0017] Q1. Inoculate Bacillus halophilus and Pseudomonas fluorescens separately, and culture with shaking to obtain Bacillus halophilus solution and Pseudomonas fluorescens solution respectively. Mix Bacillus halophilus solution and Pseudomonas fluorescens solution to obtain microbial culture solution.

[0018] Q2. Add the microbial culture to the embedding solution while stirring to obtain a mixed solution; use a syringe or dropper to add the mixed solution to the calcium chloride solution to obtain gel beads; continue to soak the gel beads in the calcium chloride solution, wash, and dry to obtain salt- and alkali-resistant microbial gel beads.

[0019] Preferably, in Q1, *Bacillus halophilus* was inoculated onto LB medium containing 3 wt% NaCl. LB medium containing 3 wt% NaCl was prepared by adding 10 parts tryptone, 5 parts yeast extract, and 30 parts sodium chloride to 1000 parts distilled water, adjusting the pH to 7.0-7.2 with 1 mol / L sodium hydroxide or hydrochloric acid, and then autoclaving at 121℃ for 20-30 min. The shaking culture temperature for *Bacillus halophilus* was 35-37℃, and the shaking speed was 150-200 r / min. *Pseudomonas fluorescens* was inoculated onto King's B medium. Culture medium B is prepared by adding 20 parts peptone, 10 parts glycerol, 1.5 parts dipotassium hydrogen phosphate, and 1.5 parts magnesium sulfate to 1000 parts distilled water, adjusting the pH to 7.0-7.2 with 1 mol / L sodium hydroxide or hydrochloric acid, and then autoclaving at 121℃ for 20-30 min. The temperature for shaking culture of *Pseudomonas fluorescens* is 25-30℃, and the shaking speed is 150-200 r / min. Shaking culture continues until OD... 600 =0.6-0.8; the volume ratio of Bacillus halophilus suspension to Pseudomonas fluorescens suspension is (1-1.2):1.

[0020] Preferably, the embedding solution in Q2 is prepared by dissolving sodium alginate and diatomaceous earth in sterile water, wherein the mass ratio of sodium alginate, diatomaceous earth and sterile water is (2-3):(1-2):100; the volume ratio of microbial inoculum to embedding solution is 1:(1-1.5); the concentration of calcium chloride solution is 2-5wt%, the dropping rate is 1-2 mL / min, and the soaking time is 30-60 min.

[0021] This invention also provides the application of biochar-based soil conditioners for saline-alkali land in secondary saline-alkali land in irrigated agricultural areas.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] 1. This invention prepares a biochar-based soil conditioner for saline-alkali land by compounding saline-alkali improved biochar, well-rotted organic fertilizer, water-retaining agent, and salt-alkali tolerant microbial gel beads in a specific ratio. The well-rotted organic fertilizer increases soil organic matter content and improves soil structure; the water-retaining agent enhances soil water retention capacity; and the synergistic effect of saline-alkali improved biochar and salt-alkali tolerant microbial gel beads reduces soil salinity, regulates pH, and improves the soil microbial ecological environment, thus achieving a synergistic improvement of soil physicochemical properties and microbial ecology. Therefore, this soil conditioner enhances the improvement effect on saline-alkali land, helps improve soil quality and fertility, and creates favorable soil conditions for crop growth.

[0024] 2. This invention alters the structure of biochar through a series of treatments, including pyrolysis, nano-solution soaking, and cross-linking with a composite enzyme solution. The nano-solution soaking introduces nanomaterials such as nano-ferric oxide, nano-silica, nano-calcium carbonate, and nano-montmorillonite, increasing the specific surface area and surface active sites of the biochar and enhancing its adsorption capacity for salt ions in the soil, thereby effectively reducing soil salinity. The nano-ferric oxide solution imparts magnetic properties to the biochar, enabling its repeated recycling and preventing residual salt accumulation in the biochar particles. The cross-linking with the composite enzyme solution further modifies the surface of the biochar, improving its adsorption selectivity and capacity for salt, thus better addressing the problem of insufficient salt adsorption capacity of single-origin biochar.

[0025] 3. This invention alters the strong alkalinity of biochar by soaking in nano-solution and cross-linking with composite enzyme solution, enabling it to better regulate soil pH while reducing soil salinity, thus avoiding adverse effects on the soil caused by excessive alkalinity of biochar.

[0026] 4. This invention uses halophilic Bacillus and fluorescent Pseudomonas to prepare microbial gel beads. The gel beads can provide a stable living environment for microorganisms, improve the survival rate and activity of microorganisms in saline-alkali soil. Halophilic Bacillus and fluorescent Pseudomonas can participate in a variety of biochemical reactions in the soil, such as decomposing organic matter, fixing nitrogen, and solubilizing phosphorus and potassium, promoting the transformation and release of nutrients in the soil, improving soil fertility, and providing more usable nutrients for plant growth.

[0027] 5. This invention can increase the number and types of beneficial microorganisms in the soil by adding salt-tolerant microbial gel beads, improve the soil microbial community structure, inhibit the growth of harmful microorganisms, enhance the biological activity and ecological function of the soil, and help build a healthy and stable soil ecosystem. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In this invention:

[0030] Halobacillus sp. CICC 10443; China Industrial Microbial Culture Collection Center

[0031] Fluorescent Pseudomonas: Pseudomonas fluorescens CICC 21620; China Industrial Microbial Culture Collection Center.

[0032] Example 1

[0033] 1. A method for preparing saline-alkali modified biochar, comprising the following steps:

[0034] S1. Corn stalks, sawdust, and rice husks are crushed to 2 mm, washed, dried, and then pyrolyzed at 500℃ for 2 hours to obtain raw biochar. The raw biochar is then soaked in a nano solution, which consists of a mixture of 200 mL of 2 g / L nano iron oxide solution, 200 mL of 7 g / L nano silica solution, 200 mL of 6 g / L nano calcium carbonate solution, and 300 mL of 8 g / L nano montmorillonite solution. The mixture is sonicated for 1 hour and then pyrolyzed a second time at 200℃ for 1 hour to obtain nano-biochar.

[0035] S2. Mix 350 mL of the complex enzyme solution with 10 mL of 1 wt% chitosan solution. The complex enzyme solution is prepared by mixing 500 mL of 8 U / mL laccase phosphate buffer, 330 mL of 5 U / mL manganese peroxidase (MnP) phosphate buffer, and 120 mL of 4 U / mL halophilic alkaline protease phosphate buffer. Add 1 mL of 2 wt% glutaraldehyde solution for cross-linking, then add 10 g of nano-biochar, and stir the reaction at 100 rpm for 2 h. Wash and dry at 30 °C for 12 h to obtain salt-alkali modified biochar.

[0036] 2. A method for preparing salt- and alkali-resistant microbial gel beads, comprising the following steps:

[0037] Q1. Inoculate *Bacillus halophilus* and *Pseudomonas fluorescens* separately. Inoculate *Bacillus halophilus* at a 1% (v / v) inoculation rate into LB medium containing 3 wt% NaCl. The LB medium containing 3 wt% NaCl is prepared by adding 10 parts tryptone, 5 parts yeast extract, and 30 parts sodium chloride to 1000 parts distilled water, adjusting the pH to 7.0 with 1 mol / L sodium hydroxide or hydrochloric acid, and autoclaving at 121℃ for 20 min. The shaking culture temperature for *Bacillus halophilus* is 35℃, and the shaking speed is 150 r / min.

[0038] *Pseudomonas fluorescens* was inoculated at a rate of 1 v / v on King's B medium. King's B medium was prepared by adding 20 parts peptone, 10 parts glycerol, 1.5 parts dipotassium hydrogen phosphate, and 1.5 parts magnesium sulfate to 1000 parts distilled water, adjusting the pH to 7.0 with 1 mol / L sodium hydroxide or hydrochloric acid, and autoclaving at 121°C for 20 min. *Pseudomonas fluorescens* was cultured with shaking at 25°C and a shaking speed of 150 rpm until OD (overflow retardation). 600 =0.6, respectively obtained halophilic Bacillus solution and fluorescent Pseudomonas solution, 100mL of halophilic Bacillus solution and 100mL of fluorescent Pseudomonas solution were mixed to obtain microbial solution;

[0039] Q2. Add 100 mL of microbial culture to 150 mL of embedding solution. The embedding solution is prepared by dissolving 4 g of sodium alginate and 2 g of diatomaceous earth in 200 g of sterile water. Stir while adding to obtain a mixed solution. Use a syringe to dropwise add the mixed solution to a 2 wt% calcium chloride solution at a rate of 1 mL / min to obtain gel beads. Continue to soak the gel beads in the calcium chloride solution for 30 min. Wash and dry to obtain salt-alkali resistant microbial gel beads.

[0040] 3. A biochar-based soil conditioner for saline-alkali land, comprising the following components by weight: 40 parts saline-alkali improved biochar, 18 parts well-rotted organic fertilizer, 4 parts water-retaining agent, and 4 parts salt-alkali tolerant microbial gel beads. Mix thoroughly before use.

[0041] Example 2

[0042] 1. A method for preparing saline-alkali modified biochar, comprising the following steps:

[0043] S1. Corn stalks, sawdust, and rice husks are crushed to 5mm, washed, dried, and then pyrolyzed at 700℃ for 4 hours to obtain raw biochar. The raw biochar is then soaked in a nano-solution, which is a mixture of 200mL 3g / L nano iron oxide solution, 200mL 8g / L nano silica solution, 300mL 8g / L nano calcium carbonate solution, and 300mL 9g / L nano montmorillonite solution. The mixture is sonicated for 2 hours and then pyrolyzed a second time at 300℃ for 2 hours to obtain nano-biochar.

[0044] S2. Mix 500 mL of the complex enzyme solution with 20 mL of 3 wt% chitosan solution. The complex enzyme solution is prepared by mixing 550 mL of 10 U / mL laccase phosphate buffer, 370 mL of 7 U / mL manganese peroxidase phosphate buffer, and 150 mL of 5 U / mL halophilic alkaline protease phosphate buffer. Add 2 mL of 2.5 wt% glutaraldehyde solution for cross-linking, then add 10 g of nano-biochar, and stir the reaction at 150 rpm for 4 h. Wash and dry at 40 °C for 24 h to obtain salt-alkali modified biochar.

[0045] 2. A method for preparing salt- and alkali-tolerant microbial gel beads, comprising the following steps:

[0046] Q1. Inoculate *Bacillus halophilus* and *Pseudomonas fluorescens* separately. *Bacillus halophilus* was inoculated at a 3% (v / v) inoculation rate on LB medium containing 3 wt% NaCl. LB medium containing 3 wt% NaCl was prepared by adding 10 parts tryptone, 5 parts yeast extract, and 30 parts sodium chloride to 1000 parts distilled water, adjusting the pH to 7.2 with 1 mol / L sodium hydroxide or hydrochloric acid, and autoclaving at 121°C for 30 min. The *Bacillus halophilus* was cultured with shaking at 37°C and a shaking speed of 200 r / min. *Pseudomonas fluorescens* was inoculated at a 2% (v / v) inoculation rate on King's B medium. Medium B was prepared by adding 20 parts peptone, 10 parts glycerol, 1.5 parts dipotassium hydrogen phosphate, and 1.5 parts magnesium sulfate to 1000 parts distilled water, adjusting the pH to 7.2 with 1 mol / L sodium hydroxide or hydrochloric acid, and then autoclaving at 121°C for 30 min. The *Pseudomonas fluorescens* culture was carried out at 30°C with a shaking speed of 200 rpm until the OD (October Observation Time) was reached. 600 =0.8, respectively obtained Bacillus halophilus solution and Pseudomonas fluorescens solution, and 120 mL of Bacillus halophilus solution and 100 mL of Pseudomonas fluorescens solution were mixed to obtain microbial solution;

[0047] Q2. Add 100 mL of microbial culture to 100 mL of embedding solution. The embedding solution is prepared by dissolving 6 g of sodium alginate and 4 g of diatomaceous earth in 200 g of sterile water. Stir while adding to obtain a mixed solution. Use a dropper to add the mixed solution to a 5 wt% calcium chloride solution at a rate of 2 mL / min to obtain gel beads. Continue to soak the gel beads in the calcium chloride solution for 60 min. Wash and dry to obtain salt-alkali resistant microbial gel beads.

[0048] 3. A biochar-based soil conditioner for saline-alkali land, consisting of the following components by weight: 42 parts saline-alkali improved biochar, 19 parts decomposed organic fertilizer, 4.5 parts water-retaining agent, and 4.5 parts salt-alkali tolerant microbial gel beads.

[0049] Example 3

[0050] 1. A method for preparing saline-alkali modified biochar, comprising the following steps:

[0051] S1. Corn stalks, sawdust, and rice husks are crushed to 3mm, washed, dried, and then pyrolyzed at 600℃ for 3 hours to obtain raw biochar. The raw biochar is then soaked in a nano-solution, which is a mixture of 200mL of 2.5g / L nano-ferric oxide solution, 200mL of 7.5g / L nano-silica solution, 250mL of 7g / L nano-calcium carbonate solution, and 300mL of 8.5g / L nano-montmorillonite solution. The mixture is then sonicated for 1.5 hours and then pyrolyzed again at 250℃ for 1.5 hours to obtain nano-biochar.

[0052] S2. Mix 400 mL of the complex enzyme solution with 15 mL of 2 wt% chitosan solution. The complex enzyme solution is prepared by mixing 530 mL of 9 U / mL laccase phosphate buffer, 360 mL of 6 U / mL manganese peroxidase phosphate buffer, and 130 mL of 4.5 U / mL halophilic alkaline protease phosphate buffer. Add 1.5 mL of 2.3 wt% glutaraldehyde solution for cross-linking, then add 10 g of nano-biochar, and stir the reaction at 130 rpm for 3 h. Wash and dry at 35 °C for 18 h to obtain salt-alkali modified biochar.

[0053] 2. A method for preparing salt- and alkali-tolerant microbial gel beads, comprising the following steps:

[0054] Q1. Inoculate *Bacillus halophilus* and *Pseudomonas fluorescens* separately. *Bacillus halophilus* was inoculated at a 5% (v / v) inoculation rate on LB medium containing 3 wt% NaCl. LB medium containing 3 wt% NaCl was prepared by adding 10 parts tryptone, 5 parts yeast extract, and 30 parts sodium chloride to 1000 parts distilled water, adjusting the pH to 7.1 with 1 mol / L sodium hydroxide or hydrochloric acid, and autoclaving at 121°C for 25 min. The *Bacillus halophilus* was cultured with shaking at 36°C and a shaking speed of 180 r / min. *Pseudomonas fluorescens* was inoculated at a 3% (v / v) inoculation rate on King's B medium. Medium B was prepared by adding 20 parts peptone, 10 parts glycerol, 1.5 parts dipotassium hydrogen phosphate, and 1.5 parts magnesium sulfate to 1000 parts distilled water, adjusting the pH to 7.1 with 1 mol / L sodium hydroxide or hydrochloric acid, and then autoclaving at 121°C for 25 min. The temperature for shaking culture of *Pseudomonas fluorescens* was 28°C, and the shaking speed was 180 r / min. The culture was continued until the OD (October Observation Time) reached... 600 =0.7, Bacillus halophilus solution and Pseudomonas fluorescens solution were obtained respectively. 110 mL of Bacillus halophilus solution and 100 mL of Pseudomonas fluorescens solution were mixed to obtain microbial inoculum.

[0055] Q2. Add 100 mL of microbial culture to 130 mL of embedding solution, which is prepared by dissolving 5 g of sodium alginate and 3 g of diatomaceous earth in 200 g of sterile water. Stir while adding to obtain a mixed solution. Use a dropper to add the mixed solution to a 3 wt% calcium chloride solution at a rate of 1.5 mL / min to obtain gel beads. Continue to soak the gel beads in the calcium chloride solution for 50 min, wash, and dry to obtain salt-alkali resistant microbial gel beads.

[0056] 3. A biochar-based soil conditioner for saline-alkali land, consisting of the following components by weight: 45 parts saline-alkali improved biochar, 20 parts decomposed organic fertilizer, 5 parts water-retaining agent, and 5 parts salt-alkali tolerant microbial gel beads.

[0057] Comparative Example 1

[0058] Compared with Example 3, Comparative Example 1 did not involve soaking in a nano-solution during the preparation of the biochar-based soil conditioner for saline-alkali land. The specific preparation method of the soil conditioner for saline-alkali land was as follows:

[0059] S1. Crush corn stalks, sawdust, and rice husks to 2mm, wash, dry, and pyrolyze them at 500℃ for 2 hours to obtain raw biochar.

[0060] S2. Mix 350 mL of the complex enzyme solution with 10 mL of 1 wt% chitosan solution. The complex enzyme solution is prepared by mixing 500 mL of 8 U / mL laccase phosphate buffer, 330 mL of 5 U / mL manganese peroxidase phosphate buffer, and 120 mL of 4 U / mL halophilic alkaline protease phosphate buffer. Add 1 mL of 2 wt% glutaraldehyde solution for cross-linking, then add 10 g of raw biochar, and stir the reaction at 100 rpm for 2 h. Wash and dry the biochar at 30 °C for 12 h to obtain salt-alkali modified biochar.

[0061] Other conditions are the same as in Example 3.

[0062] Comparative Example 2

[0063] Compared with Example 3, Comparative Example 2 did not add a compound enzyme solution during the preparation of the biochar-based soil conditioner for saline-alkali land, while all other conditions remained unchanged. The specific preparation method of the soil conditioner for saline-alkali land is as follows:

[0064] S1, Same as Example 3;

[0065] S2. Mix 350 mL of the complex enzyme solution with 10 mL of 1 wt% chitosan solution. The complex enzyme solution is prepared by mixing 500 mL of 8 U / mL laccase phosphate buffer, 330 mL of 5 U / mL manganese peroxidase phosphate buffer, and 120 mL of 4 U / mL halophilic alkaline protease phosphate buffer. Add 1 mL of 2 wt% glutaraldehyde solution for cross-linking, then add 10 g of nano-biochar, and stir the reaction at 100 rpm for 2 h. Wash and dry at 30 °C for 12 h to obtain salt-alkali modified biochar.

[0066] Comparative Example 3

[0067] Compared with Example 3, Comparative Example 3 did not add salt-tolerant microbial gel beads during the preparation of biochar-based soil conditioner for saline-alkali land, while all other conditions remained unchanged.

[0068] Performance test example:

[0069] Application of biochar-based soil conditioners for saline-alkali land in secondary saline-alkali land in irrigated agricultural areas. The secondary saline-alkali land in the Manas region of Xinjiang was selected as the irrigated agricultural area. The performance of the biochar-based soil conditioners for saline-alkali land prepared in Examples 1-3 and Comparative Examples 1-3 was tested. The test methods are as follows:

[0070] (1) The biochar-based soil conditioners for saline-alkali land prepared in Examples 1-3 and Comparative Examples 1-3 were mixed with water at a mass ratio of 1:200 in a water distribution tank. The mixing speed was 200 rpm and the mixing time was 45 min to obtain irrigation water.

[0071] (2) Irrigate twice with drip water at an irrigation intensity of 15-20 mm / h, with an interval of 3 days. Each drip irrigation lasts for 6 hours, and the irrigation water is at a rate of 150 m³ / h. 3 Irrigation is carried out at a rate of 25cm between drip emitters per acre. Crops are sown 15 days after drip irrigation. After the crops are harvested, a geomagnetic device is used to adsorb the magnetic soil conditioner to prevent residual salt accumulation from biochar particles.

[0072] 1. Soil salinity removal rate test

[0073] According to NY / T 1121.16-2023 "Soil Testing Part 16: Determination of Total Water-Soluble Salts in Soil", based on step 1, the soil salinity removal rate of the biochar-based soil conditioners for saline-alkali land prepared in Examples 1-3 and Comparative Examples 1-3 was tested. Soil salinity was tested before irrigation, 15 days after drip irrigation, and 90 days after drip irrigation. The measurement temperature was 25℃. The initial conductivity EC0 was measured using a conductivity meter before irrigation, and the conductivity after drip irrigation was recorded as EC0. t Salt removal rate = (EC0 - EC) t The test results are shown in Table 1: (EC0×100%)

[0074] Table 1 Results of soil salinity removal rate test

[0075]

[0076] According to the test results in Table 1, compared with Comparative Examples 1-3, the soil salinity removal rate of the biochar-based soil conditioner for saline-alkali land prepared in Examples 1-3 was significantly improved. Specifically, the soil salinity removal rate of the biochar-based soil conditioner for saline-alkali land prepared in Examples 1-3 reached 64.7% 90 days after drip irrigation application, which is higher than the national standard Class I (National Standard Class I is greater than 60%). In Comparative Example 1, no nano-solution was added, resulting in a decrease in the specific surface area of ​​the biochar, which led to a decrease in sodium ion adsorption and thus a decrease in the soil salinity removal rate. In Comparative Example 2, no nano-solution was added. The addition of a compound enzyme solution prevented the degradation of phenolic toxins in the soil, inhibiting the desorption of salt ions and thus reducing the soil salinity removal rate. In Comparative Example 3, the absence of salt-tolerant microbial gel beads resulted in a decrease in the survival rate and content of salt-tolerant microorganisms, as well as insufficient organic acid secretion, leading to a further reduction in soil salinity removal. Therefore, it can be seen that soaking in a nano-solution, adding a compound enzyme solution, and adding salt-tolerant microbial gel beads during the preparation of biochar-based soil conditioners for saline-alkali land can help improve the soil salinity removal rate, and the resulting soil conditioner is suitable for saline-alkali land.

[0077] 2. Soil pH test

[0078] Soil pH was tested according to LY / T 1229-2023 "Determination of pH Value of Forest Soils". The soil pH values ​​of the biochar-based saline-alkali soil conditioners prepared in Examples 1-3 and Comparative Examples 1-3 were tested. The biochar-based saline-alkali soil conditioners prepared in Examples 1-3 and Comparative Examples 1-3 were applied according to Example 4, and soil pH values ​​were tested before irrigation, 15 days after drip irrigation, and 90 days after drip irrigation. The test results are shown in Table 2.

[0079] Table 2 Soil pH test results

[0080]

[0081] According to the test results in Table 2, compared with Comparative Examples 1-2, the biochar-based soil conditioners for saline-alkali land prepared in Examples 1-3 showed a more significant decrease in soil pH 90 days after drip irrigation application. Notably, Comparative Example 1 did not include nano-solution and lacked nano-CaCO3 slow-release Ca. 2+ HCO3 - Insufficient neutralization led to a decrease in acid production, resulting in an increase in soil pH compared to Examples 1-3. In Comparative Example 2, no compound enzyme solution was added, leading to a deficiency of laccase in the soil, undegraded phenolic toxins, and bound OH groups. -The ions increase the soil pH compared to Examples 1-3; therefore, it can be seen that soaking in a nano solution and adding a compound enzyme solution during the preparation of the biochar-based soil conditioner for saline-alkali land helps to reduce the soil pH, and the prepared soil conditioner is suitable for saline-alkali land.

[0082] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, 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. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A biochar-based soil conditioner for saline-alkali land, characterized in that, It is composed of the following components by weight: 40-45 parts of salt-alkali modified biochar, 18-20 parts of well-rotted organic fertilizer, 4-5 parts of water-retaining agent, and 4-5 parts of salt-alkali tolerant microbial gel beads; the salt-alkali modified biochar is prepared by pyrolysis of biochar material, soaking in nano solution, and cross-linking with composite enzyme solution; the salt-alkali tolerant microbial gel beads are prepared by adding a mixture of microbial inoculum and encapsulation solution dropwise into calcium chloride solution; The nano-solution comprises a mixture of nano-ferric oxide solution, nano-silica solution, nano-calcium carbonate solution, and nano-montmorillonite solution; the volume ratio of the nano-ferric oxide solution, nano-silica solution, nano-calcium carbonate solution, and nano-montmorillonite solution is 2:2:2-3:3; the concentration of the nano-ferric oxide solution is 2-3 g / L, the concentration of the nano-silica solution is 7-8 g / L, the concentration of the nano-calcium carbonate solution is 6-8 g / L, and the concentration of the nano-montmorillonite solution is 8-9 g / L. The complex enzyme solution is prepared by mixing laccase phosphate buffer, manganese peroxidase phosphate buffer, and halophilic alkaline protease phosphate buffer, wherein the volume ratio of laccase phosphate buffer, manganese peroxidase phosphate buffer, and halophilic alkaline protease phosphate buffer is 50-55:33-37:12-15, the concentration of laccase phosphate buffer is 8-10 U / mL, the concentration of manganese peroxidase phosphate buffer is 5-7 U / mL, and the concentration of halophilic alkaline protease phosphate buffer is 4-5 U / mL. The method for preparing the saline-alkali modified biochar includes the following steps: S1. The biochar material is crushed, washed, dried, and pyrolyzed to obtain raw biochar; the raw biochar is soaked in a nano solution, sonicated, and pyrolyzed a second time to obtain nano biochar. S2. Mix the composite enzyme solution with the chitosan solution, add glutaraldehyde solution for cross-linking, then add nano-biochar, stir the reaction, wash, and dry to obtain salt-alkali modified biochar. The preparation method of the salt- and alkali-resistant microbial gel beads includes the following steps: Q1. Inoculate Bacillus halophilus and Pseudomonas fluorescens separately, and culture with shaking to obtain Bacillus halophilus solution and Pseudomonas fluorescens solution respectively. Mix Bacillus halophilus solution and Pseudomonas fluorescens solution to obtain microbial culture solution. Q2. Add the microbial culture to the embedding solution while stirring to obtain a mixed solution; add the mixed solution dropwise to the calcium chloride solution to obtain gel beads; continue to soak the gel beads in the calcium chloride solution, wash, and dry to obtain salt- and alkali-resistant microbial gel beads.

2. The biochar-based soil conditioner for saline-alkali land according to claim 1, characterized in that, In S1, the biochar material includes one or more of corn stalks, sawdust, and rice husks.

3. The biochar-based soil conditioner for saline-alkali land according to claim 1, characterized in that, The ratio of the amount of compound enzyme solution, chitosan solution, glutaraldehyde solution and nano-biochar in S2 is 35-50 mL: 1-2 mL: 0.1-0.2 mL: 1 g.

4. The biochar-based soil conditioner for saline-alkali land according to claim 1, characterized in that, The volume ratio of Bacillus halophilus suspension to Pseudomonas fluorescens suspension in Q1 is 1-1.2:

1.

5. The biochar-based soil conditioner for saline-alkali land according to claim 1, characterized in that, The embedding solution in Q2 was prepared by dissolving sodium alginate and diatomaceous earth in water, wherein the mass ratio of sodium alginate, diatomaceous earth and water was 2-3:1-2:

100.

6. The biochar-based soil conditioner for saline-alkali land according to claim 1, characterized in that, In Q2, the volume ratio of microbial inoculum to encapsulation solution is 1:1-1.5; the concentration of calcium chloride solution is 2-5 wt%.

7. The application of the biochar-based soil conditioner for saline-alkali land according to any one of claims 1-6 in secondary saline-alkali land in irrigated agricultural areas.

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