A composite conditioner for repairing acidified soil and preparation method thereof

Abstract

The present invention discloses a composite conditioner for repairing acidified soil and a preparation method thereof, and belongs to the technical field of acidified soil repair. The present invention prepares a carrier for loading bacterial strains by mixing and calcining steel slag, straw and kaolin, and then loads the embedded bacterial strains in the carrier to prepare a soil conditioner, which can efficiently repair acidic soil and provide sufficient nutrients for the soil; the soil conditioner provided by the present invention can adjust the release rate according to the pH value of the acidic soil to be repaired, and can reduce the amount of the soil conditioner on the basis of improving the repair effect; the soil conditioner provided by the present invention has high stability and obvious slow-release effect; the raw materials used in the present invention are simple and easy to obtain, the preparation process is simple, and it is suitable for large-scale promotion and application.

Description

Technical Field

[0001] The invention belongs to the technical field of acidified soil remediation, and more specifically relates to a composite conditioner for remediating acidified soil and a preparation method thereof. Background Art

[0002] At present, the problem of soil acidification is more prominent around the world. Soil acidification will inhibit the activity of organisms in the soil, change the form of nutrients, and reduce their effectiveness. For example, a large amount of manganese and aluminum ions will dissolve into the soil solution, which will be toxic to crops, thus affecting the growth and development of crops, resulting in reduced crop yields and poor quality.

[0003] Traditional methods of acidic soil remediation mainly include applying lime, burning manure, and applying organic fertilizer, but these methods have certain limitations. For example, although lime can adjust soil pH, it will generate a lot of heat after absorbing water, which can easily cause seedling burns, and it is easy to lose its effectiveness and rebound quickly after a period of use. It will also inhibit the absorption of phosphorus and affect the growth and development of vegetable seedling roots. Although methods such as burning manure can adjust soil pH to a certain extent, with the expansion of agricultural production scale and the improvement of modernization, its implementation difficulty and operability are gradually reduced. Increasing the application of organic fertilizer can adjust soil acidity and fertilize the soil in both directions, but when used alone, it can only control soil acidification during the vegetable growing season, and cannot fundamentally improve the soil, resulting in the need to add it every time vegetables are planted, which increases costs and is difficult to cure the problem of soil acidification.

[0004] As people pay more attention to soil quality and soil acidification becomes more serious, soil conditioners have emerged. They can improve soil through physical, chemical or microbial means. Compared with traditional methods, they have the advantages of strong targeting, significant effects and easy use, and have become one of the important means of acid soil remediation.

[0005] However, the commonly used soil conditioners currently have the following problems: 1. Insufficient stability of effect: Some soil conditioners have a good effect on improving acidic soil in the short term, but with the passage of time and the influence of environmental factors, the effect is difficult to maintain for a long time. For example, some conditioners with lime as the main ingredient can quickly increase the pH value of the soil, but they are easily leached by rainwater or react with acidic substances in the soil and gradually become ineffective, resulting in the phenomenon of "re-acidification" of the soil; 2. Unbalanced nutrient supply: Some soil conditioners cannot take into account the supplementation and balance of soil nutrients while adjusting the pH of the soil. For example, some simple acidifiers only focus on reducing soil acidity, but ignore the needs of other nutrients in the soil, which may lead to the lack or imbalance of certain trace elements in the soil, affecting the normal growth of crops; 3. Complex effects on soil microorganisms: Different soil conditioners have different effects on soil microorganisms. Some conditioners may inhibit or change the community structure and activity of soil microorganisms, thereby affecting the ecological function of the soil. For example, some chemical conditioners may be toxic to beneficial microorganisms in the soil, disrupt the balance of soil microorganisms, and be detrimental to the long-term healthy development of the soil.

[0006] Based on the above, it is of great significance to develop a soil conditioner for acidified soil remediation that does not affect the original microbial activity in the soil, has a balanced nutrient supply, and has high remediation stability. Summary of the invention

[0007] The purpose of the present invention is to provide a composite soil conditioner for repairing acidified soil and a preparation method thereof, so as to solve the problems existing in the above-mentioned prior art, realize the preparation of a soil conditioner for repairing acidified soil which does not affect the original microbial activity in the soil, has a balanced nutrient supply and high repair stability, and achieves the purpose of efficiently repairing acidified soil.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] One of the technical solutions of the present invention is to provide a method for preparing a composite conditioner for repairing acidified soil, comprising the following steps:

[0010] The steel slag, straw and kaolin are mixed and calcined to obtain a carrier;

[0011] The composite bacterial suspension and the sodium alginate aqueous solution are mixed to obtain a mixed solution; the mixed solution is added dropwise to the calcium chloride aqueous solution, and after the addition is completed, cross-linking is performed to obtain bacterial microspheres embedded therein;

[0012] The carrier, the embedded bacterial microspheres and the phosphate buffer are mixed to obtain the soil conditioner;

[0013] The composite bacterial species in the composite bacterial species suspension include Bacillus subtilis, Bacillus laterosporus, Bacillus licheniformis and Bacillus megaterium, the mass ratio of Bacillus subtilis, Bacillus laterosporus, Bacillus licheniformis and Bacillus megaterium is 1-2:1:2-3:3-4, and the live bacteria content in the composite bacterial species suspension is 3×10 7 ~4×10 8 CFU / mL.

[0014] Firstly, the present invention prepares a carrier loaded with bacterial strains by calcining steel slag, straw and kaolin, wherein steel slag is a waste material generated in the steelmaking process, and recycling the steel slag can avoid its pollution to the environment. In addition, the steel slag has a high pH value and contains rich elements such as calcium, magnesium, iron, silicon, phosphorus and the like that are beneficial to plant growth. The steel slag can also effectively improve the pH value of the soil, and has a significant effect on repairing acidic soil, and can also reduce the toxic effect of heavy metals in the soil on the soil. The straw contains rich organic matter and nutrient elements, which can increase the organic matter content of the soil, improve the soil structure, and improve the water and fertilizer retention capacity of the soil. At the same time, the soil pH can be adjusted to achieve the purpose of treating acidic soil. Kaolin, as a binder, can improve the formability and stability of the composite material during the calcination process, so that the composite calcined material has a better physical structure and mechanical strength, which is conducive to maintaining the pore structure and surface characteristics of the material, and provides a stable environment for the growth of the bacterial strains loaded in the later stage. At the same time, the kaolin itself also has certain adsorption properties and ion exchange capacity, which can adjust the chemical environment around the calcined soil and promote the absorption and utilization of nutrients by microorganisms.

[0015] Secondly, the present invention embeds the strain before the strain is loaded on the carrier. During the embedding process, the gel network structure formed by cross-linking sodium alginate and calcium chloride has certain pores and spaces, which can accommodate and fix the strain, and also provide channels and resistance for the diffusion and release of substances, thereby achieving a slow-release effect. In addition, after embedding, the bonding strength between the embedded microspheres and the carrier and the uniformity of the load can be significantly improved due to the presence of surface active functional groups. In addition, after embedding, the restoration effect of the obtained soil conditioner on acidic soil can be significantly improved. In the process of repairing soil, the swelling or shrinkage degree of the gel network is different with the change of the environmental pH value, which will change the pore structure and diffusion path inside the gel ball, so that the release rate of the strain is regulated; when encountering a more acidic environment, the swelling or shrinkage degree of the gel network increases, the release rate of the strain is accelerated, and the treatment effect on the acidic soil is improved. When the acidic soil is repaired, the environmental pH value increases, the swelling or shrinkage degree of the gel network decreases, and the strain release rate slows down; by adjusting the release rate, the amount of the soil conditioner can be reduced on the basis of improving the repair effect.

[0016] In addition, the bacteria can passivate the heavy metals in the steel slag, thus avoiding the adverse effects of the heavy metals in the steel slag on the acidic soil to be repaired.

[0017] Furthermore, the present invention can effectively repair acidic soil through the synergistic effect of Bacillus subtilis, Brevibacillus laterosporus, Bacillus licheniformis and Bacillus megaterium, and provide sufficient nutrients to the soil to promote the growth of crops. Among them, the organic acid produced by Bacillus subtilis can react with the acidic substances in the soil to increase the pH value of the soil, increase the soil fertility, improve the soil structure, and create good conditions for plant growth; the organic acid produced by Brevibacillus laterosporus can neutralize the soil acidity and increase the pH value, and the antimicrobial peptides produced can inhibit the growth of harmful microorganisms in the soil, reduce the occurrence of soil-borne diseases, and indirectly promote plant growth. The fungus-inhibiting peptides and chitinase produced by Bacillus licheniformis can prevent and control soil-borne plant diseases, especially fungal diseases, maintain the balance of soil microbial communities, make the soil ecosystem more stable, and are beneficial to the improvement and restoration of acidic soils. Its metabolites can also improve soil structure and promote plant growth. The extracellular polysaccharides produced by Bacillus megaterium can increase the formation of water-stable granular structure of soil, increase soil porosity, reduce soil bulk density, improve soil aeration and water permeability, and are beneficial to the growth and development of plant roots, thereby improving the quality and fertility of acidic soils.

[0018] Preferably, the particle size of the steel slag is 200-300 μm; the straw includes corn straw and / or wheat straw, and the length of the straw is 1-3 mm; and the particle size of the kaolin is 150-200 μm.

[0019] Preferably, the mass ratio of the steel slag, straw and kaolin is 10-15:5-8:4-7.

[0020] Preferably, the calcination temperature is 600-900° C., the calcination heating rate is 10-20° C. / min, and the calcination holding time is 2-3 h.

[0021] Preferably, the mass fraction of the sodium alginate aqueous solution is 1-5%; the volume proportion of the composite bacterial suspension in the mixed solution is 20-40%; and the mass fraction of the calcium chloride aqueous solution is 2-5%.

[0022] Preferably, the dripping speed is 0.05 to 0.08 mL / s; and the cross-linking time is 0.5 to 1 h.

[0023] Preferably, the pH value of the phosphate buffer is 6.5-7.5; the mass volume ratio of the carrier, the bacterial strain-embedded microspheres and the phosphate buffer is 10 g: 12-15 g: 40-50 mL.

[0024] Preferably, the carrier, the bacterial strain-embedded microspheres and the phosphate buffer are mixed by stirring, the stirring speed is 100 to 150 r / min, and the stirring time is 2 to 3 h.

[0025] Preferably, the carrier, the bacterial strain-embedded microspheres and the phosphate buffer are mixed and further include the steps of centrifugation and drying.

[0026] The second technical solution of the present invention is to provide a soil conditioner prepared by the preparation method.

[0027] The present invention discloses the following technical effects:

[0028] 1. The present invention prepares a carrier loaded with bacteria by mixing and calcining steel slag, straw and kaolin, and then loads the embedded bacteria in the carrier to prepare a soil conditioner. The soil conditioner can efficiently repair acidic soil and provide sufficient nutrients for the soil;

[0029] 2. The soil conditioner provided by the present invention can adjust the release rate according to the pH value of the acidic soil to be repaired, and can reduce the amount of the soil conditioner on the basis of improving the repair effect;

[0030] 3. The soil conditioner provided by the present invention has high stability and obvious slow-release effect;

[0031] 4. The raw materials used in the present invention are simple and easy to obtain, the preparation process is simple, and it is suitable for large-scale promotion and application. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] The strains involved in the present invention were purchased from the following manufacturers: Bacillus subtilis was purchased from Shanxi Lvhai Pesticide Technology Co., Ltd., Bacillus Brevisporus was purchased from Hubei Qiming Bioengineering Co., Ltd., Bacillus licheniformis was purchased from Hubei Zhongxiang Bioengineering Co., Ltd., and Bacillus megaterium was purchased from Hubei Zhongxiang Bioengineering Co., Ltd.

[0038] Preparation of Bacillus subtilis suspension:

[0039] 1. Strain processing and cultivation: Primary culture: open the freeze-dried strain tube under sterile conditions, add an appropriate amount of nutrient broth medium to melt and disperse the strain. Take a small amount of strain suspension and inoculate it into a nutrient broth medium test tube, and culture it at 37°C for 24 hours; Subculture: use an inoculation loop to take the primary culture suspension and streak it on a nutrient agar medium plate, and continue to culture to obtain the second generation. Then pick a typical colony and inoculate it into the nutrient broth medium to obtain the third generation culture;

[0040] 2. Spore formation and inspection: Inoculate the third generation culture on the surface of the nutrient agar medium in the Roche flask and culture for 7 days; use an inoculation loop to take a bacterial sample and stain it with the improved spore staining method. The spore formation rate under microscopic examination must reach more than 95%;

[0041] 3. Prepare spore suspension: add sterile distilled water to the Roche flask, gently scrape off the bacterial moss, and wash repeatedly; concentrate the washed bacterial suspension in a sterile conical flask containing glass beads and shake to obtain a uniform spore suspension.

[0042] Preparation of Bacillus laterosporus suspension:

[0043] 1. Strain activation: Inoculate the freeze-dried bacterial tube on the slant culture medium under sterile conditions for activation culture;

[0044] 2. Preparation of bacterial suspension: Wash the slope with sterile water to obtain seed solution, i.e., preliminary bacterial suspension; the concentration of bacterial solution can be adjusted, such as by using a turbidimeter or turbidometer, to ensure that the bacterial suspension reaches the required turbidity;

[0045] 3. Spore formation and inspection: Cultivate the bacterial suspension under appropriate conditions, such as on a nutrient agar plate at 35-37°C; smear, stain, and examine the spore rate under a microscope to ensure that the required ratio is reached;

[0046] 4. Preparation of spore suspension: Use sterile water to wash off the mixture of spores and bacteria to make a suspension.

[0047] Preparation of Bacillus licheniformis suspension:

[0048] 1. Prepare culture medium: prepare glucose-peptone culture medium as needed;

[0049] 2. Inoculation: Inoculate the freeze-dried bacterial tube into the culture medium under sterile conditions;

[0050] 3. Cultivation: Cultivate the inoculated culture medium at appropriate temperature and conditions, generally at 28°C for 20 hours;

[0051] 4. Expand the culture: inoculate the cultured bacterial liquid into the fermentation medium at a 3% inoculation rate and culture at 30°C for 48 hours;

[0052] 5. Collect bacterial suspension: After the culture is completed, collect the Bacillus licheniformis suspension.

[0053] Preparation of Bacillus megaterium suspension:

[0054] 1. Activation of bacterial strains: Take the freeze-dried bacterial strain tube, open it under sterile operation, add appropriate amount of nutrient broth medium to melt and disperse the bacterial strain; inoculate it into the nutrient broth medium test tube, and culture it at 37℃ for 24h;

[0055] 2. Transfer and cultivation: streak the culture onto a nutrient agar plate and culture at 37°C; pick a typical bacterial colony and inoculate it into a nutrient broth medium and continue culturing;

[0056] 3. Spore formation and inspection: Inoculate the culture on the surface of nutrient agar medium in a Roche flask and culture for 7 days; stain with the improved spore staining method, and the spore formation rate under microscopic examination must reach more than 95%;

[0057] 4. Prepare spore suspension: add sterile distilled water to the Roche flask, gently scrape off the bacterial moss, and wash repeatedly; concentrate the washed bacterial suspension in a sterile conical flask containing glass beads and shake to obtain a uniform spore suspension.

[0058] The formula of nutrient broth medium is: 1000 mL of distilled water, 20 g of glucose, 15 g of peptone, 5 g of sodium chloride, 0.5 g of beef extract and 20 g of agar.

[0059] The slant culture medium formula is: peptone 10g, beef extract 15g, sodium chloride 15g, agar 18g and distilled water 1000mL, and the pH value is adjusted to 7.2.

[0060] The formula of glucose-peptone medium is: 0.5 g glucose, 0.5 g peptone, 0.5 g potassium hydrogen phosphate, 100 mL water, and the pH value is adjusted to 7.2.

[0061] The formula of nutrient agar medium is: 10 g of peptone, 3 g of beef extract, 5 g of sodium chloride, 15 g of agar and 1000 mL of distilled water, and the pH value is adjusted to 7.2.

[0062] The steel slag involved in the following embodiments and comparative examples was taken from a steel plant, and the straw was taken from a crop wholesale base.

[0063] Unless otherwise specified, other raw materials involved in the following examples and comparative examples are commercially available products.

[0064] The room temperature involved in the present invention is 25±5°C unless otherwise specified.

[0065] Example 1

[0066] This embodiment provides a preparation of a composite conditioner for repairing acidified soil, and the specific steps are as follows:

[0067] (1) Preparation of composite bacterial suspension: The bacterial suspensions of the above-mentioned bacterial species were mixed in a mass ratio of 1:1:2:3 for Bacillus subtilis, Bacillus laterosporus, Bacillus licheniformis and Bacillus megaterium, and the content of live bacteria in the suspension obtained after mixing was ensured to be 4×10 8 CFU / mL, reserve;

[0068] (2) Preparation of carrier: Steel slag with a particle size of 250 μm, wheat straw with a size of 2 mm, and kaolin with a particle size of 150 μm were mixed in a mass ratio of 15:5:4 and placed in a calcining furnace. The temperature was raised to 700°C at a heating rate of 10°C / min and kept at this temperature for 2 h to obtain a carrier for later use.

[0069] (3) Embedding of composite bacterial strains: The composite bacterial strain suspension obtained in step (1) is mixed with a sodium alginate aqueous solution having a mass fraction of 2.5% to obtain a mixed solution, wherein the volume of the composite bacterial strain suspension accounts for 30% of the mixed solution; the mixed solution is added dropwise to a calcium chloride aqueous solution having a mass fraction of 3% at a rate of 0.05 mL / s, and after the addition is completed, the mixture is cross-linked at room temperature for 0.5 h to obtain embedded bacterial strain microspheres for standby use;

[0070] (4) Preparation of soil conditioner: The carrier, the embedded bacterial microspheres and the phosphate buffer solution with a pH value of 6.5 were stirred and mixed at a ratio of 10 g:14 g:50 mL for 2.5 h at a stirring speed of 150 r / min to obtain a soil conditioner.

[0071] Example 2

[0072] This embodiment provides a preparation of a composite conditioner for repairing acidified soil, and the specific steps are as follows:

[0073] (1) Preparation of composite bacterial suspension: The bacterial suspensions of the above-obtained bacterial species were mixed in a mass ratio of 2:1:2.5:3 for Bacillus subtilis, Bacillus laterosporus, Bacillus licheniformis and Bacillus megaterium, and the content of live bacteria in the suspension obtained after mixing was ensured to be 5×10 7 CFU / mL, reserve;

[0074] (2) Preparation of carrier: Steel slag with a particle size of 300 μm, wheat straw with a size of 3 mm, and kaolin with a particle size of 150 μm were mixed in a mass ratio of 15:5:4 and placed in a calcining furnace. The temperature was increased to 650°C at a heating rate of 15°C / min and kept at this temperature for 2.5 h to obtain a carrier for later use.

[0075] (3) Embedding of composite bacterial strains: The composite bacterial strain suspension obtained in step (1) is mixed with a 3% sodium alginate aqueous solution to obtain a mixed solution, wherein the volume proportion of the composite bacterial strain suspension in the mixed solution is 35%; the mixed solution is added dropwise to a 5% calcium chloride aqueous solution at a rate of 0.05 mL / s, and after the addition is completed, the mixture is cross-linked at room temperature for 1 hour to obtain embedded bacterial strain microspheres for standby use;

[0076] (4) Preparation of soil conditioner: The carrier, the embedded bacterial microspheres and the phosphate buffer solution with a pH value of 7.5 were stirred and mixed at a ratio of 10 g:12 g:45 mL for 3 h at a stirring speed of 150 r / min to obtain a soil conditioner.

[0077] Example 3

[0078] This embodiment provides a preparation of a composite conditioner for repairing acidified soil, and the specific steps are as follows:

[0079] (1) Preparation of composite bacterial suspension: The bacterial suspensions of the above-obtained bacterial species were mixed in a mass ratio of 2:1:2:4 for Bacillus subtilis, Bacillus laterosporus, Bacillus licheniformis and Bacillus megaterium, and the content of live bacteria in the suspension obtained after mixing was ensured to be 2×10 8 CFU / mL, reserve;

[0080] (2) Preparation of carrier: Steel slag with a particle size of 200 μm, wheat straw with a size of 2 mm, and kaolin with a particle size of 150 μm were mixed in a mass ratio of 12:8:7 and placed in a calcining furnace. The mixture was heated to 800°C at a heating rate of 10°C / min and kept at this temperature for 2 h to obtain a carrier for later use.

[0081] (3) Embedding of composite bacterial strains: The composite bacterial strain suspension obtained in step (1) is mixed with a 5% sodium alginate aqueous solution to obtain a mixed solution, wherein the volume of the composite bacterial strain suspension accounts for 30% of the mixed solution; the mixed solution is added dropwise to a 2% calcium chloride aqueous solution at a rate of 0.05 mL / s, and after the addition is completed, the mixture is cross-linked at room temperature for 0.5 h to obtain embedded bacterial strain microspheres for standby use;

[0082] (4) Preparation of soil conditioner: The carrier, the embedded bacterial microspheres and the phosphate buffer solution with a pH value of 6.5 were stirred and mixed at a ratio of 10 g:12 g:40 mL for 3 h at a stirring speed of 150 r / min to obtain a soil conditioner.

[0083] Comparative Example 1

[0084] The difference from Example 1 is that the addition of kaolin is omitted, and the rest is the same as Example 1.

[0085] Comparative Example 2

[0086] The difference from Example 1 is that the addition of steel slag is omitted, and the rest is the same as Example 1.

[0087] Comparative Example 3

[0088] The difference from Example 1 is that the step of embedding the composite bacteria is omitted, and the composite bacteria suspension obtained in step (1) is directly mixed with the carrier and the phosphate buffer. The rest is the same as Example 1.

[0089] Comparative Example 4

[0090] The difference from Example 1 is that the addition of Bacillus subtilis is omitted, and the rest is the same as Example 1.

[0091] Comparative Example 5

[0092] The difference from Example 1 is that the addition of Bacillus licheniformis is omitted, and the rest is the same as Example 1.

[0093] Test example

[0094] The experiment was carried out in a plastic greenhouse (6m wide and 80m long), and a control group (no soil conditioner was applied, denoted as CK) and a treatment group (the soil conditioner prepared in Examples 1 to 3 and Comparative Examples 1 to 5 was applied, with an application rate of 200 catties / mu) were set up.

[0095] 1. Test the soil pH value of the target restoration site:

[0096] The plastic greenhouse was divided into 10 parts, 2 of which were for the control group and the others were treated by the treatment groups respectively; the original pH value of the soil in the target restoration site was recorded as the initial pH value; after treatment by the control group and the treatment group, the pH value of the soil was tested at 48h, recorded as the first pH value; the pH value of the soil was tested at 96h, recorded as the second pH value; the pH value of the soil was tested at 144h, recorded as the third pH value; the pH value of the soil was tested at 192h, recorded as the fourth pH value; the pH value of the soil was tested at 240h, recorded as the fifth pH value; the soil pH value was measured at the same time points as mentioned above, and the results are shown in Table 1.

[0097] Table 1 Soil pH values ​​of target restoration sites at different times

[0098]

[0099]

[0100] It can be seen from Table 1 that the soil conditioner obtained by the present invention can efficiently repair acidic soil in a short time.

[0101] 2. Test the impact on crop growth:

[0102] The plastic greenhouse was divided into 10 parts, 2 of which were control groups, and the others were treated by the treatment groups. Amaranth seeds were then sown and harvested 30 days after germination. The amaranth yield was measured. The results are shown in Table 2.

[0103] Table 2 Yield of Amaranth

[0104]

[0105] It can be seen from Table 2 that planting crops in the soil repaired by the soil conditioner of the present invention can significantly increase the yield of the crops, indicating that the soil conditioner of the present invention can provide sufficient nutrients to the soil while repairing the soil, thereby promoting the growth of crops.

[0106] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0107] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a composite conditioner for repairing acidified soil, characterized in that: The steps include: The steel slag, straw and kaolin are mixed and calcined to obtain a carrier; The composite bacterial suspension and the sodium alginate aqueous solution are mixed to obtain a mixed solution; the mixed solution is added dropwise to the calcium chloride aqueous solution, and after the addition is completed, cross-linking is performed to obtain bacterial microspheres embedded therein; The carrier, the embedded bacterial microspheres and the phosphate buffer are mixed to obtain the soil conditioner; The composite bacterial species in the composite bacterial species suspension include Bacillus subtilis, Bacillus laterosporus, Bacillus licheniformis and Bacillus megaterium, the mass ratio of Bacillus subtilis, Bacillus laterosporus, Bacillus licheniformis and Bacillus megaterium is 1-2:1:2-3:3-4, and the live bacteria content in the composite bacterial species suspension is 3×10 7 ~4×10 8 CFU / mL.

2. The preparation method according to claim 1, characterized in that: The particle size of the steel slag is 200-300 μm; the straw includes corn straw and / or wheat straw, and the length of the straw is 1-3 mm; the particle size of the kaolin is 150-200 μm.

3. The preparation method according to claim 1, characterized in that: The mass ratio of the steel slag, straw and kaolin is 10-15:5-8:4-7.

4. The preparation method according to claim 1, characterized in that: The calcination temperature is 600-900° C., the calcination heating rate is 10-20° C. / min, and the calcination heat preservation time is 2-3 hours.

5. The preparation method according to claim 1, characterized in that: The mass fraction of the sodium alginate aqueous solution is 1-5%; the volume proportion of the composite bacterial suspension in the mixed solution is 20-40%; and the mass fraction of the calcium chloride aqueous solution is 2-5%.

6. The preparation method according to claim 1, characterized in that: The dropping speed is 0.05-0.08 mL / s; the cross-linking time is 0.5-1 h.

7. The preparation method according to claim 1, characterized in that: The pH value of the phosphate buffer is 6.5-7.5; the mass volume ratio of the carrier, the bacterial strain-embedded microspheres and the phosphate buffer is 10g:12-15g:40-50mL.

8. The preparation method according to claim 1, characterized in that: The carrier, the bacterial strain-embedded microspheres and the phosphate buffer solution are mixed by stirring at a speed of 100 to 150 r / min for a time of 2 to 3 hours.

9. The preparation method according to claim 1, characterized in that: After the carrier, the bacterial strain-embedded microspheres and the phosphate buffer are mixed, the method further comprises the steps of centrifugation and drying.

10. A soil conditioner prepared by the preparation method according to any one of claims 1 to 9.

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