Biochar-based organic fertilizer as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of saline-alkali soil improvement, and relates to a charcoal-based organic fertilizer as well as a preparation method and application thereof. The method comprises the following steps: crushing and sieving biomass materials; the preparation method comprises the following steps: uniformly mixing desulfurized gypsum and biomass powder according to a ratio, adding water, immediately and sufficiently stirring, drying, and sieving to obtain a pretreated biomass material; carrying out high-temperature carbonization on the pretreated biomass material under a limited oxygen condition, then cooling to room temperature, drying and sieving to prepare desulfurized gypsum modified biomass charcoal; and uniformly mixing the desulfurized gypsum modified biomass charcoal and the decomposed organic fertilizer according to a ratio, adjusting the pH value by using a wood vinegar conditioner, and then inoculating a microbial agent for fermentation to obtain the charcoal-based organic fertilizer. The biochar-based organic fertilizer provided by the invention is used for saline-alkali soil, and through the synergistic effect of all the raw materials, the soil fertility is improved, soil salinization is relieved, crop root growth is promoted, K < + > / Na < + > in crops is increased, and then the yield of the crops is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of saline-alkali soil improvement, and specifically relates to a preparation method of a biochar-based organic fertilizer and application thereof. Background Art

[0002] Coastal saline-alkali land is an important reserve arable land resource in my country. The orderly development of saline-alkali land that meets the conditions into arable land is an effective way to ensure my country's food security. Coastal saline-alkali land has the characteristics of high soil salt content, low soil fertility level, especially low organic matter content, poor structure, and low number of beneficial microorganisms, which prevents crops from growing normally and leads to very low crop yields.

[0003] Scientific soil improvement is a prerequisite for healthy plant growth. Biochar contains a large amount of organic carbon and nutrients required by crops, which can improve the efficiency of crop nutrient utilization and promote crop growth. In addition, biochar has rich pore structure and strong adsorption performance, which can improve soil structure and adsorb Na in the soil. + , is a major technical approach to treat saline-alkali land. However, since biochar is generally alkaline, excessive application may increase the risk of soil salinization. Wood vinegar is an acidic byproduct of biomass pyrolysis and carbonization. It contains rich small molecular organic matter and has a growth-promoting effect on plants. However, excessive concentration of wood vinegar applied to the soil can easily burn plants. The main component of desulfurized gypsum is CaSO 4 ·2H 2 O, after being applied to the surface soil, its form will change from solid to liquid under the dissolution of water, Ca 2+ Can replace Na on soil colloids + , thereby reducing the alkalinity and pH value of the soil; absorbing Ca 2+ The soil colloids are hydrophobic, and the colloidal particles are not easy to disperse, which is conducive to soil aggregation and improves the soil structure. 2+ It can react with carbonates in the soil that are highly toxic to crops to generate CaCO 3 Precipitation is beneficial to crop growth. Although desulfurized gypsum mainly contains elements such as Ca and S, it is not very effective in improving soil fertility. In addition, microorganisms have become an effective biological tool that can alleviate salt stress in plants through a variety of mechanisms, such as changes in the expression of defense-related proteins, activation of antioxidant mechanisms, accumulation of osmotic substances, and increased plant hormone levels and nutrient absorption. It can also improve plant growth by reducing the toxic effects of saline-alkali soil on plants, while repairing degraded saline-alkali land. However, microorganisms generally need to be made into biofertilizers to better play their role in promoting plant salt tolerance.

[0004] In order to give full play to the role of chemical improvers and functional microorganisms and further enhance the potential of improving saline-alkali land, it is urgently necessary to develop a soil improver that is more suitable for use in saline-alkali land. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a preparation method and application of a biochar-based organic fertilizer soil conditioner in view of the deficiencies in the prior art. The biochar-based organic fertilizer can reduce the salinization degree of soil, increase the nutrient content of soil, and thus promote crop growth.

[0006] Invention idea: Desulfurized gypsum is rich in CaSO 4 , after application into soil, Ca 2+ Can react with CO in soil 3 2- and HCO 3 - The reaction generates CaCO 3 precipitation, and can also absorb the Na + It is replaced, thereby reducing the soil pH and alkalinity. Co-pyrolysis of desulfurized gypsum and biomass to produce modified biochar can not only inhibit the harm of salt and alkali, but also improve soil quality. Compounding desulfurized gypsum-modified biochar with decomposed organic fertilizer to produce charcoal-based organic fertilizer is conducive to the survival of the connected functional microorganisms. In addition, the organic acid in wood vinegar can reduce the alkalinity of biochar, increase the solubility of desulfurized gypsum, and promote the growth of crop roots. Therefore, the comprehensive utilization of chemical modifiers and functional microorganisms to improve saline-alkali soil is of great significance to preventing soil salinization and improving soil productivity, while solving the problem of difficulty in resource utilization of waste.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A biochar-based organic fertilizer for saline-alkali land, characterized by comprising the following steps:

[0009] (1) drying, crushing and sieving the biomass material for later use; mixing the desulfurized gypsum and the biomass powder in a mass ratio of 2 to 4:10, adding water and stirring immediately, drying and sieving through a 2 mm sieve to obtain a pretreated biomass material;

[0010] (2) subjecting the pretreated biomass material obtained in step (1) to high-temperature carbonization under oxygen-limited conditions, cooling to room temperature after carbonization, drying, and passing through a 2 mm sieve to obtain desulfurized gypsum-modified biochar, and collecting the byproduct wood vinegar;

[0011] (3) The desulfurized gypsum-modified biochar obtained in step (2) is uniformly mixed with decomposed organic fertilizer in a weight ratio to obtain a carbon-based organic fertilizer; and calcium lactate and calcium malate are added to the wood vinegar obtained in step (2) to obtain a wood vinegar conditioner.

[0012] (4) adding wood vinegar conditioner to the charcoal-based organic fertilizer obtained in step (3) to adjust the pH, piling at room temperature for 4 to 6 days, turning the pile once a day, inoculating 0.05 mL / g to 1 mL / g of microbial agent, turning the pile once a day, fermenting for 3 to 5 days, and finally evaporating the water content to less than 30% at a temperature below 60° C. to obtain a biochar-based organic fertilizer containing a single functional microorganism; if there are multiple microbial agents, the biochar-based organic fertilizer containing a single functional microorganism is prepared according to the above method and then mixed to obtain a composite biochar-based organic fertilizer.

[0013] In some embodiments, in step (1), the biomass material is any one of corn straw, wheat straw, rice husk, and wood chips, preferably corn straw.

[0014] In some embodiments, in step (1), the particle size of the biomass powder is within 2 mm; the desulfurized gypsum is dried desulfurized gypsum passed through a 100-mesh sieve; and the heavy metal content in the desulfurized gypsum is lower than the limit requirements of national agricultural-related standards.

[0015] In some embodiments, preferably, in step (1), the weight ratio of the desulfurized gypsum to the biomass powder is 1:5, 1:4, 3:10 and 1:2.5, and more preferably 1:4.

[0016] In some embodiments, in step (1), the weight ratio of the added water to the mixture of biomass powder and desulfurized gypsum is 1:1.

[0017] In some embodiments, in step (2), the oxygen-limited condition is carried out in a nitrogen environment; in the high-temperature carbonization, the temperature of the carbonization furnace reactor is increased from room temperature to 450-500°C at a heating rate of 5°C / min and maintained for 2-3h.

[0018] In some embodiments, in step (2), the wood vinegar is the upper clarified portion of the crude wood vinegar obtained by condensing part of the volatile components of the pretreated biomass material during the pyrolysis and carbonization process; 3 to 8 g of calcium lactate and 3 to 8 g of calcium malate are added to every 1 L of wood vinegar, preferably 5 g of calcium lactate and 5 g of calcium malate are added to every 1 L of wood vinegar.

[0019] In some embodiments, in step (3), the decomposed organic fertilizer is any one of decomposed pig manure organic fertilizer, decomposed chicken manure organic fertilizer and decomposed cow dung organic fertilizer, preferably decomposed pig manure organic fertilizer.

[0020] In some embodiments, preferably, in step (3), the weight ratio of the desulfurized gypsum modified biochar to the decomposed organic fertilizer is 1:4, 1:3, and 1:2.5, and more preferably 1:3.

[0021] In some embodiments, in step (4), the pH of the carbon-based organic fertilizer is adjusted to 6.5-7 using the wood vinegar conditioner.

[0022] In some embodiments, in step (4), the pH is adjusted to 6.5-7; the microbial agent is selected from Propionibacterium freudenreichii and Clostridium butyricum; the cell concentration of the microbial agent reaches 1×10 9 CFU mL -1 The content of Propionibacterium freudenreichii or Clostridium butyricum in the biochar-based organic fertilizer reaches 1×10 8 CFU g -1 The above; the biochar-based organic fertilizer containing Propionibacterium freudenreichii and the biochar-based organic fertilizer containing Clostridium butyricum are mixed in a dry weight ratio of 1:1 to prepare a composite biochar-based organic fertilizer.

[0023] The Propionibacterium freudenreichii and Clostridium butyricum strains can be obtained through commercial channels, preferably Propionibacterium freudenreichii subspecies ATCC 6207 and Clostridium butyricum ATCC 19398 provided by Shanghai Preservation Microorganisms Co., Ltd. The Propionibacterium freudenreichii bacterial agent and Clostridium butyricum bacterial agent are fermentation broths of the two bacterial strains.

[0024] The formula of the culture medium used for Propionibacterium freudenreichii subsp. freudenreichii ATCC 6207 is 10g of tryptic peptone, 5g of yeast extract, 10g of sodium lactate, 1L of distilled water, pH7.0-7.2, and sterilization at 121°C for 30min. Adding 1.5% (W / V) agar to the liquid culture medium is a solid culture medium. First, activate Propionibacterium freudenreichii on the solid culture medium, place it in a 30°C incubator for anaerobically cultured for 3 days, inoculate the activated strain into the liquid culture medium, pick a single colony and inoculate it into a test tube containing 3mL of liquid culture medium, and culture it at 30°C and 170rpm for 24h. Inoculate the bacterial solution in the test tube into a triangular flask containing 100ml of liquid culture medium at an inoculum amount of 1% (v / v), draw 5mL of bacterial solution from the triangular flask, add it to a sterile fermenter containing 800ml of liquid culture medium, and culture it at 30°C and 170rpm for 48h to make the bacterial concentration reach 1.0×10 9 CFU / mL, and the obtained fermentation broth was used as the Propionibacterium freudenreichii inoculum.

[0025] The formula of the culture medium used by Clostridium butyricum ATCC 19398 is 10g of tryptone, 10g of beef extract, 5g of glucose, 5g of sodium chloride, 3g of yeast extract, 3g of sodium acetate, 1g of soluble starch, 0.5g of L-cysteine ​​hydrochloride, 1L of distilled water, pH 6.8, and sterilization at 121°C for 30min. Adding 1.5% (W / V) agar to the liquid culture medium is a solid culture medium. First, Clostridium butyricum is activated on the solid culture medium, placed in an incubator at 37°C for anaerobic culture for 3 days, the activated strain is inoculated in the liquid culture medium, and a single colony is picked and inoculated in a test tube containing 3mL of liquid culture medium, and cultured at 30°C and 170rpm for 24h. The bacterial solution in the test tube was inoculated into a flask containing 100 ml of liquid culture medium at a 1% (v / v) inoculation rate. 5 mL of bacterial solution was taken from the flask and added to a sterile fermenter containing 800 ml of liquid culture medium. The culture was cultured at 30°C and 170 rpm for 48 hours. The bacterial concentration reached 1.0×10 9 CFU / mL, and the obtained fermentation broth was used as Clostridium butyricum agent.

[0026] The biochar-based organic fertilizer prepared by the above preparation method is also within the protection scope of the present invention.

[0027] The application of the above-mentioned biochar-based organic fertilizer in improving coastal tidal flat saline-alkali land is also within the protection scope of the present invention.

[0028] Beneficial effects:

[0029] The invention provides a biochar-based organic fertilizer which can promote the growth of crop roots, increase crop yields, and improve the physical and chemical properties of saline-alkali soil.

[0030] (1) The biochar-based organic fertilizer provided by the present invention can promote the growth of soybean roots, enhance root vitality, and improve K + / Na + , effectively increasing the soybean seed yield per plant.

[0031] (2) The biochar-based organic fertilizer provided by the present invention significantly reduces soil pH and salt content, alleviates soil salinity stress, increases soil total nitrogen and organic carbon content, and improves soil quality.

[0032] (3) The biochar-based organic fertilizer provided by the present invention is applied to saline-alkali soil in tidal flats, and the raw materials are coordinated with each other. Desulfurized gypsum, calcium lactate and calcium malate can not only reduce soil pH, but also improve soil structure. Biochar, organic fertilizer and wood vinegar can not only provide nutrient resources for plants, but also absorb salt in the soil and reduce soil alkalinity. Functional microorganisms (Propionibacterium freudenreichii or Clostridium butyricum) can produce propionic acid and butyric acid, which can improve the growth environment of crops. The comprehensive management effect of biochar-based organic fertilizer is remarkable.

[0033] The preparation method of the present invention is easy to operate and low in cost, and can solve the problem of treating agricultural wastes. After the prepared biochar-based organic fertilizer soil conditioner is applied to saline-alkali land, it can not only enhance soil fertility, but also reduce soil salinization, promote crop growth, and thus increase crop yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0035] Figure 1 Effects of different treatments on soybean seed yield per plant.

[0036] Figure 2 Effects of different treatments on soybean stems, leaves and seeds K + / Na + impact.

[0037] Figure 3 Effects of different treatments on soybean root activity.

[0038] Figure 4 Effects of different treatments on the average soil weight diameter.

[0039] Figure 5 Root morphology of soybean under different treatments. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with specific examples, but the protection scope of the present invention is not limited thereto. The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials used in the examples are all commercially available unless otherwise specified.

[0041] The preparation method of the bacterial agent used in the following examples is as follows:

[0042] The formula of the culture medium used for Propionibacterium freudenreichii subsp. freudenreichii ATCC 6207 is 10g of tryptic peptone, 5g of yeast extract, 10g of sodium lactate, 1L of distilled water, pH7.0-7.2, and sterilization at 121°C for 30min. Adding 1.5% (W / V) agar to the liquid culture medium is a solid culture medium. First, activate Propionibacterium freudenreichii on the solid culture medium, place it in a 30°C incubator for anaerobically cultured for 3 days, inoculate the activated strain into the liquid culture medium, pick a single colony and inoculate it into a test tube containing 3mL of liquid culture medium, and culture it at 30°C and 170rpm for 24h. Inoculate the bacterial solution in the test tube into a triangular flask containing 100ml of liquid culture medium at an inoculum amount of 1% (v / v), draw 5mL of bacterial solution from the triangular flask, add it to a sterile fermenter containing 800ml of liquid culture medium, and culture it at 30°C and 170rpm for 48h to make the bacterial concentration reach 1.0×10 9 CFU / mL, and the obtained fermentation broth was used as the Propionibacterium freudenreichii inoculum.

[0043] The formula of the culture medium used by Clostridium butyricum ATCC 19398 is 10g of tryptone, 10g of beef extract, 5g of glucose, 5g of sodium chloride, 3g of yeast extract, 3g of sodium acetate, 1g of soluble starch, 0.5g of L-cysteine ​​hydrochloride, 1L of distilled water, pH 6.8, and sterilization at 121°C for 30min. Adding 1.5% (W / V) agar to the liquid culture medium is a solid culture medium. First, Clostridium butyricum is activated on the solid culture medium, placed in an incubator at 37°C for anaerobic culture for 3 days, the activated strain is inoculated in the liquid culture medium, and a single colony is picked and inoculated in a test tube containing 3mL of liquid culture medium, and cultured at 30°C and 170rpm for 24h. The bacterial solution in the test tube was inoculated into a flask containing 100 ml of liquid culture medium at a 1% (v / v) inoculation rate. 5 mL of bacterial solution was taken from the flask and added to a sterile fermenter containing 800 ml of liquid culture medium. The culture was cultured at 30°C and 170 rpm for 48 hours. The bacterial concentration reached 1.0×10 9 CFU / mL, and the obtained fermentation broth was used as Clostridium butyricum agent.

[0044] Example 1: Preparation of biochar-based organic fertilizer soil conditioner

[0045] (1) Preparation of desulfurized gypsum-modified biochar: The agricultural waste corn stalks were placed in a 65°C oven, and after the stalks were dried to remove moisture, they were crushed into powders within 2 mm. The desulfurized gypsum that met the national agricultural standards was dried and ground through a 100-mesh sieve, and the desulfurized gypsum and biomass powder were mixed evenly at a mass ratio of 1:4. Water was then added to the mixture of desulfurized gypsum and biomass powder at a volume weight ratio of 1:1, and immediately stirred thoroughly. After drying, the mixture was sieved through a 2 mm sieve to obtain a pretreated biomass material. The pretreated biomass material was placed in a closed pyrolysis carbonization furnace, and the temperature was raised from room temperature to 450°C at a rate of 5°C / min under a nitrogen protective atmosphere. After being kept warm for 2 hours, it was cooled to room temperature, and the wood vinegar was collected. The desulfurized gypsum-modified biochar obtained was placed in a 65°C oven for drying for 36 hours and ground through a 2 mm sieve.

[0046] (2) Preparation of wood vinegar conditioner: Add 5 g of calcium lactate and 5 g of calcium malate to every 1 L of wood vinegar, stir and dissolve, to prepare the wood vinegar conditioner.

[0047] (2) Preparation of carbon-based organic fertilizer: The desulfurized gypsum-modified biochar and the decomposed pig manure organic fertilizer were uniformly mixed in a weight ratio of 1:3 to prepare carbon-based organic fertilizer.

[0048] (3) Preparation of biochar-based organic fertilizer: The charcoal-based organic fertilizer was adjusted to pH 6.5-7 with wood vinegar conditioner, and then piled at room temperature for 5 days, turning the pile once a day. 0.05 mL / g of Propionibacterium freudenreichii or 0.05 mL / g of Clostridium butyricum were inoculated, and the pile was turned once a day. After 4 days of fermentation, the content of Propionibacterium freudenreichii or Clostridium butyricum reached 1×10 8 CFU g -1 The above steps are performed, and finally the water content is evaporated to below 30% at a temperature below 60°C to obtain a biochar-based organic fertilizer containing Propionibacterium freudenreichii and a biochar-based organic fertilizer containing Clostridium butyricum, respectively. The two are mixed in a dry weight ratio of 1:1 to obtain a composite biochar-based organic fertilizer.

[0049] Example 2: Potted experiment on improving saline-alkali soil in tidal flats with biochar-based organic fertilizer

[0050] (1) Soil selection: Soil from the coastal tidal flats of Jiangsu Province was selected for potted plant experiments. The soil was air-dried under natural conditions, mixed, and passed through a 2 mm sieve. The basic chemical properties of the soil are shown in Table 1.

[0051] Table 1 Basic chemical properties of the tested soil

[0052]

[0053] (2) Experimental design: A total of four treatments were set up in the potted plant experiment: blank control (CK), microbial agent (MI), decomposed pig manure organic fertilizer (OF), and biochar-based organic fertilizer (BOF), and each treatment was set up with 3 replicates. 6 kg of air-dried soil was added to each pot, and decomposed pig manure organic fertilizer and biochar-based organic fertilizer were applied to the soil at an application rate of 1% (w / w). After the soil sample was potted, 1000 ml of water was added to fully moisten the soil. The biochar-based organic fertilizer used was the composite biochar-based organic fertilizer prepared in Example 1. For the treatment of inoculation with microbial agents, the volume of the agent added to the composite biochar-based organic fertilizer should be kept consistent, that is, 1.5 ml of Propionibacterium freudenreichii fermentation liquid and 1.5 ml of Clostridium butyricum fermentation liquid were diluted to 1000 ml and added to the soil. 0.7 g of diammonium phosphate was applied to each treatment. After the soil environment was stabilized for 4 days, sowing was carried out. The crop planted was soybean (Qihuang 34). After the seeds emerged, 3 plants were left in each pot, and the same amount of water was regularly supplemented. After soybean harvest, the average seed yield per soybean plant, root morphology, root activity, K + / Na + and the basic chemical properties of the soil.

[0054] (3) Test results:

[0055] As attached Figure 1 As shown, compared with the control group, the application of microbial agents, organic fertilizers and biochar-based organic fertilizers significantly increased soybean grain yield, and the soybean grain yield of the biochar-based organic fertilizer treatment was the highest, indicating that the application of biochar-based organic fertilizer soil amendments can further increase soybean grain yield.

[0056] The plant potassium-sodium ratio reflects the ion balance in the plant body and can be used to indicate the degree of damage to the plant caused by salt stress. Figure 2 As shown in a, compared with the control, microbial agent, and organic fertilizer treatments, the potassium-sodium ratio of soybean stems and leaves treated with biochar-based organic fertilizer increased significantly by 184.3%, 76.3%, and 95.9%, respectively. Figure 2 As shown in (b), the potassium-sodium ratio of soybean grains treated with biochar-based organic fertilizer increased significantly by 6.8 times, 3.4 times, and 1.9 times compared with the control, microbial agent, and organic fertilizer treatments, respectively. This indicates that the application of biochar-based organic fertilizer can more effectively alleviate salt stress.

[0057] As shown in Table 2, compared with the control group, the application of biochar-based organic fertilizer significantly reduced soil pH by 0.66 units, soil salt content by 27.3%, and soil alkalinity by 35.5%. The soil salt content in the biochar-based organic fertilizer treatment was the lowest (2.40 g / kg). Compared with the control treatment, the total nitrogen and organic carbon contents in the biochar-based organic fertilizer treatment increased significantly by 40.0% and 99.3%, respectively.

[0058] Table 2 Effects of different treatments on soil chemical properties

[0059]

[0060] As shown in Table 3, compared with other treatments, the application of biochar-based organic fertilizer significantly increased the root length, root surface area, root volume and number of root tips of soybean. Since biochar-based organic fertilizer contains biochar, wood vinegar, microorganisms and calcium salts, biochar-based organic fertilizer can improve the root structure of soybean under the comprehensive effect. The more developed the root system is, the more nutrients and water it absorbs, and the stronger the salt tolerance of the crop is.

[0061] Table 3 Effects of different treatments on soybean root morphology

[0062]

[0063] Root activity can measure the growth and resistance of plants. Figure 3 As shown, the soybean root activity treated with biochar-based organic fertilizer was significantly higher than that of the other three treatments, indicating that the biochar-based organic fertilizer can improve the stress resistance of soybean and promote the growth of soybean.

[0064] The average weight diameter of soil is an important indicator of soil structural stability. The larger the value, the more stable the soil structure and the stronger the aggregation. Figure 4 As shown in the data, the application of biochar-based organic fertilizer to the soil effectively improved the stability of the soil structure, and the average weight diameter of the soil was significantly higher than that of other treatments, while the application of microbial agents alone could not increase the average weight diameter.

[0065] The present invention provides a method for preparing biochar-based organic fertilizer for saline-alkali land and a method and idea for its application. There are many methods and approaches to realize the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be realized by existing technologies.

Claims

1. A biochar-based organic fertilizer for saline-alkali land, characterized in that: The steps include: (1) drying, crushing and sieving the biomass material for later use; mixing the desulfurized gypsum and the biomass powder in a mass ratio of 2 to 4:10, adding water and stirring immediately, drying and sieving through a 2 mm sieve to obtain a pretreated biomass material; (2) subjecting the pretreated biomass material obtained in step (1) to high-temperature carbonization under oxygen-limited conditions, cooling to room temperature after carbonization, drying, and passing through a 2 mm sieve to obtain desulfurized gypsum-modified biochar, and collecting the byproduct wood vinegar; (3) mixing the desulfurized gypsum-modified biochar obtained in step (2) and the decomposed organic fertilizer in a weight ratio to obtain a carbon-based organic fertilizer; adding calcium lactate and calcium malate to the wood vinegar obtained in step (2) to obtain a wood vinegar conditioner; (4) adding wood vinegar conditioner to the charcoal-based organic fertilizer obtained in step (3) to adjust the pH, piling at room temperature for 4 to 6 days, turning the pile once a day, inoculating 0.05 mL / g to 1 mL / g of microbial agent, turning the pile once a day, fermenting for 3 to 5 days, and finally evaporating the water content to less than 30% at a temperature below 60° C. to obtain a biochar-based organic fertilizer containing a single functional microorganism; if there are multiple microbial agents, the biochar-based organic fertilizer containing a single functional microorganism is prepared according to the above method and then mixed to obtain a composite biochar-based organic fertilizer.

2. The method according to claim 1, characterized in that In step (1), the biomass material is any one of corn straw, wheat straw, rice husk and sawdust; the particle size of the biomass powder is within 2 mm, and the desulfurized gypsum is dried desulfurized gypsum sieved through a 100-mesh sieve.

3. The method according to claim 1, characterized in that In step (1), the weight ratio of the added water to the biomass powder and desulfurized gypsum mixture is 1:0.5-1, preferably 1:

1.

4. The method according to claim 1, characterized in that: In step (2), the oxygen-limited condition is carried out in a nitrogen environment; in the high-temperature carbonization, the temperature of the carbonization furnace reactor is increased from room temperature to 450-500° C. at a heating rate of 5° C. / min and maintained for 2-3 hours.

5. The method according to claim 1, characterized in that In step (2), the wood vinegar is the upper clarified portion of the crude wood vinegar obtained by condensing part of the volatile components of the pretreated biomass material during the pyrolysis and carbonization process; 3 to 8 g of calcium lactate and 3 to 8 g of calcium malate are added to every 1 L of wood vinegar.

6. The method according to claim 1, characterized in that In step (3), the decomposed organic fertilizer is any one of decomposed pig manure organic fertilizer, decomposed chicken manure organic fertilizer and decomposed cow dung organic fertilizer.

7. The method according to claim 1, characterized in that In step (3), the weight ratio of the desulfurized gypsum modified biochar to the decomposed organic fertilizer is 1:2.5-4.

8. The method according to claim 1, characterized in that In step (4), the pH is adjusted to 6.5-7; the microbial agent is selected from Propionibacterium freudenreichii and Clostridium butyricum, and the cell concentration of the microbial agent reaches 1×10 9 CFU mL -1 The content of Propionibacterium freudenreichii or Clostridium butyricum in the biochar-based organic fertilizer soil conditioner can reach 1×10 8 CFU g -1 The above; the biochar-based organic fertilizer containing Propionibacterium freudenreichii and the biochar-based organic fertilizer containing Clostridium butyricum are mixed in a dry weight ratio of 1:1 to prepare a composite biochar-based organic fertilizer.

9. Biochar-based organic fertilizer for saline-alkali land prepared by the preparation method according to any one of claims 1 to 9.

10. Use of the biochar-based organic fertilizer for saline-alkali land as claimed in claim 10 in improving saline-alkali soil on coastal tidal flats.

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