Oyster shell-derived soil remediation agent and preparation method thereof

Abstract

The present invention discloses an oyster shell-derived soil remediation agent and a preparation method thereof, relating to the technical field of soil remediation agent preparation. The oyster shell-derived soil remediation agent of the present invention comprises an inner layer of oyster shell powder, an organic fertilizer layer, a beneficial bacteria layer, and an outer layer of oyster shell powder. The weight ratio of the inner layer of oyster shell powder, the organic fertilizer layer, the beneficial bacteria layer, and the outer layer of oyster shell powder is (20-35):(20-30):(3-8):(40-60). A first inner membrane is provided between the inner layer of oyster shell powder and the organic fertilizer layer, a second inner membrane is provided between the organic fertilizer layer and the beneficial bacteria layer, a third inner membrane is provided between the beneficial bacteria layer and the outer layer of oyster shell powder, and the outer layer of oyster shell powder is coated with an outer membrane. The oyster shell-derived soil remediation agent of the present invention has a long-lasting effect, can improve soil pH, adsorb heavy metals, and increase soil organic matter content, and is of great significance for repairing soil in karst areas.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation agent preparation, and in particular to an oyster shell-derived soil remediation agent and a preparation method thereof. Background Art

[0002] Oyster shells are the outer shells of oysters of the genus Crassostreae, family Ostreae. The primary inorganic component of oyster shells is calcium carbonate (CaCO3), which accounts for over 90% of the shell's mass. Besides being rich in calcium, oyster shells are also rich in over 20 trace elements, including Cu, Fe, Zn, Mn, and Sr, present in the form of oxides. Oyster shell powder is made by calcining oyster shells at temperatures exceeding 800°C. The decomposition of CaCO3 into CaO releases CO2, creating a complex porous structure. The resulting CaO, when dissolved in water, exhibits antibacterial properties and neutralizes acidic soils. Its porous structure provides strong adsorption and ion exchange capabilities. Therefore, oyster shell powder can be used to adsorb heavy metals, reduce soil acidity, and sterilize soils.

[0003] At present, there are reports on the use of oyster shell powder as a soil conditioner to adjust the soil pH value and change the physical and chemical properties of the soil. For example, patent application No. 202210423190.2 discloses an acidic soil conditioner and its preparation method. The soil conditioner is made of modified activated plant carbon, shell powder, seaweed fertilizer and lime, which can effectively increase the pH value of acidic soil and has the effect of improving the properties of acidic soil. For example, non-patent literature: Effects of Tebei calcium soil conditioner on peanut yield and soil acidification in red soil dryland (Liu Kailou, Xiong Huarong, Hu Huiwen, et al. Guangdong Agricultural Science, 2017, 44 (5): 93-98), Effects of oyster shell powder on rice yield and soil heavy metal passivation (Luo Huahan, Liu Kailou, Yu Paolan, et al. China Rice, 2016, 22 (3): 30-33), etc., all disclose the role of soil conditioners with oyster shell as raw material in the cultivation of crops such as rice and peanuts. The application of oyster shell powder can effectively inhibit the exchangeable H in the soil. + and Al 3+ The increase in content slows down soil acidification.

[0004] Guangxi's karst topography is predominantly poor, and coupled with long-term continuous cropping, excessive fertilizer application, repeated shallow tillage, and seasonal rainstorms in the south, have led to severe acidification of arable land. Acidic soils are prone to compaction, seepage, and poor water retention. Through years of production practice, the applicant has discovered that applying oyster shell powder directly to karst soils according to existing methods results in rapid leaching and loss, resulting in a short-lasting effect. Furthermore, oyster shell powder can only improve soil pH but not increase soil organic matter content. Combining it with organic fertilizers can lead to unstable fertilizer effects. If the organic fertilizer used is acidic, it will chemically react with the alkaline oyster shell powder, reducing its effectiveness.

[0005] In summary, the development of an oyster shell-derived soil remediation agent with long-lasting effects that can improve soil pH, adsorb heavy metals, and increase soil organic matter content is of great significance for repairing soil in karst areas. Summary of the Invention

[0006] In view of the above shortcomings, the present invention provides an oyster shell-derived soil remediation agent and a preparation method thereof, which solves the problem that the existing oyster shell-derived soil remediation agent has a short-lasting effect and cannot improve soil fertility well. The specific technical solution is as follows:

[0007] An oyster shell-derived soil remediation agent comprises, from the inside out, an oyster shell powder inner layer, an organic fertilizer layer, a beneficial bacteria layer, and an oyster shell powder outer layer, wherein the weight ratio of the oyster shell powder inner layer, the organic fertilizer layer, the beneficial bacteria layer, and the oyster shell powder outer layer is (20-35):(20-30):(3-8):(40-60);

[0008] A first inner membrane is provided between the inner layer of the oyster shell powder and the organic fertilizer layer, a second inner membrane is provided between the organic fertilizer layer and the beneficial bacteria layer, a third inner membrane is provided between the beneficial bacteria layer and the outer layer of the oyster shell powder, and the outer layer of the oyster shell powder is coated with an outer membrane.

[0009] Furthermore, the beneficial bacteria layer includes one or more of Bacillus licheniformis, Bacillus megaterium, Bacillus laterosporus, Bacillus subtilis, Bacillus gelatinosa, Paecilomyces lilacinus, and Trichoderma harzianum.

[0010] Furthermore, the first inner membrane is mainly composed of chitosan, aqueous acrylic emulsion, carboxymethyl cellulose and deionized water, and the weight ratio of the chitosan, aqueous acrylic emulsion, carboxymethyl cellulose and deionized water is 40:4-7:1-5:100-300; the coating amount of the first inner membrane is 20-25% of the weight of the inner layer of the oyster shell powder.

[0011] Chitosan and carboxymethyl cellulose are natural polymer materials that are film-forming, biodegradable, and environmentally friendly. The aqueous acrylic emulsion has excellent water resistance. Chitosan, aqueous acrylic emulsion, and carboxymethyl cellulose serve as the first inner coating, which has strong toughness and water resistance and a thick coating volume (20-25%), and can slowly release the inner layer of oyster shell powder after the organic fertilizer is released.

[0012] Furthermore, the second inner film is mainly composed of polyvinyl alcohol, carboxymethyl cellulose and deionized water, and the weight ratio of polyvinyl alcohol, carboxymethyl cellulose and deionized water is 100:10-18:300-400; the coating amount of the second inner film is 10-15% of the total weight of the coated material.

[0013] Polyvinyl alcohol is a high molecular polymer coating material that is non-toxic and harmless and can be degraded by environmental microorganisms. It is made into a second inner coating with carboxymethyl cellulose. The film has strong toughness but a thin coating volume (10-15%), which can be released faster after the beneficial bacteria are released.

[0014] Furthermore, the third inner film is mainly composed of polyvinyl alcohol, carboxymethyl cellulose and deionized water, and the weight ratio of polyvinyl alcohol, carboxymethyl cellulose and deionized water is 100:10-18:300-400; the coating amount of the third inner film is 16-20% of the total weight of the coated material.

[0015] The third inner envelope has stronger toughness and a thicker envelope (16-20%), which can slow down the release rate of beneficial bacteria.

[0016] Furthermore, the outer film is mainly composed of carboxymethyl cellulose, sodium alginate and deionized water, and the weight ratio of the carboxymethyl cellulose, sodium alginate and deionized water is 1:1-2:50-100; the coating amount of the outer film is 6-10% of the total weight of the coated material.

[0017] The coating volume of the outer coating is relatively thin, at 6-10%, and can quickly absorb water, swell, and dissolve when in contact with water, thereby promoting the rapid release of the oyster shell powder in the outer layer of the oyster shell powder.

[0018] Furthermore, the preparation method of the repair agent comprises the following steps:

[0019] (1) preparing the inner layer of oyster shell powder into particles having a water content of less than 10% to obtain oyster shell powder inner layer particles;

[0020] (2) mixing chitosan, aqueous acrylic emulsion, and deionized water, heating to 50-70° C., stirring for 20-30 minutes, adding carboxymethyl cellulose, and continuing to stir for 40-60 minutes to obtain a first inner envelope solution;

[0021] (3) atomizing the first inner coating liquid by high-speed hot air flow and uniformly spraying it onto the surface of the inner layer particles of the oyster shell powder, and drying the liquid to obtain coated inner layer particles of the oyster shell powder;

[0022] (4) crushing the organic fertilizer, mixing it with a binder and water to form a slurry, placing it in a coating spraying system and evenly spraying it on the inner layer particles of the coated oyster shell powder, and drying it to obtain particles containing an organic fertilizer layer;

[0023] (5) Heat and stir polyvinyl alcohol and deionized water until dissolved, cool to 30-50°C, add carboxymethyl cellulose and continue stirring for 30-50 minutes to obtain the second inner envelope solution;

[0024] (6) atomizing the second inner coating liquid by high-speed hot air flow and uniformly spraying it onto the surface of the particles containing the organic fertilizer layer, and drying it to obtain coated particles containing the organic fertilizer layer;

[0025] (7) After the beneficial bacteria are mixed with fillers and water to form a slurry, the slurry is placed in a coating spraying system and evenly sprayed on the coated organic fertilizer layer particles, and dried to obtain the beneficial bacteria layer particles;

[0026] (8) First, prepare a third inner coating liquid according to the method of step (5), spray the third inner coating liquid evenly on the surface of the granules containing the beneficial bacteria layer, and dry it to obtain coated granules containing the beneficial bacteria layer;

[0027] (9) mixing the outer layer of oyster shell powder with a binder and water to form a slurry, placing the slurry in a coating spraying system and spraying the slurry evenly on the coated particles containing the beneficial bacteria layer, and drying the slurry to obtain particles containing the outer layer of oyster shell powder;

[0028] (10) Sodium carboxymethyl cellulose, sodium alginate and deionized water are stirred at 60-70° C. for 20-30 min to obtain an outer coating liquid, and the outer coating liquid is evenly sprayed on the surface of the outer layer particles containing oyster shell powder, and dried to obtain the oyster shell source soil remediation agent.

[0029] Furthermore, the adhesive in step (4) and step (9) is dextrin.

[0030] Furthermore, the filler in step (7) is starch.

[0031] Furthermore, the particle size of the soil remediation agent is 5-8 mm.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The soil remediation agent of the present invention has a multi-layer coating design, which includes an outer coating, an outer layer of oyster shell powder, a third inner coating, a beneficial bacteria layer, a second inner coating, an organic fertilizer layer, a first inner coating, and an inner layer of oyster shell powder. It can not only sterilize, increase pH, and increase soil nutrients and beneficial bacteria content, but also alleviate the loss of a large amount of oyster shell powder by rainwater leaching, maintaining a more lasting effect. Among them,

[0034] The outer coating is coated on the outer layer of oyster shell powder. It is mainly composed of carboxymethyl cellulose and sodium alginate. The coating is relatively thin (6-10%) and can quickly absorb water, swell and dissolve when it comes into contact with water. The oyster shell powder in the outer layer can be quickly released, playing a role in rapid sterilization and raising the soil pH, so that the soil can be initially repaired.

[0035] The third inner membrane separates the outer layer of oyster shell powder from the beneficial bacteria layer. It is mainly composed of polyvinyl alcohol and carboxymethyl cellulose. The membrane is strong and has a thick coating (16-20%), which can slow down the release rate of beneficial bacteria. After the outer layer of oyster shell powder improves soil acidity and kills harmful bacteria, the beneficial bacteria are released in large quantities, allowing the beneficial bacteria to quickly become the dominant species and the soil begins to enter a healthy state. At the same time, the third inner membrane slows down the release rate of beneficial bacteria, preventing the outer layer of oyster shell powder from not fully reacting and affecting the activity of the beneficial bacteria.

[0036] The second inner membrane separates the beneficial bacteria layer from the organic fertilizer layer. It is mainly composed of polyvinyl alcohol and carboxymethyl cellulose. The membrane is tough but thin (10-15%), allowing for quick release after the beneficial bacteria are released. Organic fertilizer not only improves the physical and chemical properties of the soil and increases soil fertility, but also provides a good growth environment for the beneficial bacteria, promoting their long-term growth.

[0037] The first inner membrane can separate the organic fertilizer layer from the inner layer of oyster shell powder. It is mainly composed of chitosan, water-based acrylic emulsion and carboxymethyl cellulose. The membrane has strong toughness and water resistance, and the coating volume is relatively thick (20-25%). It can slowly release the inner layer of oyster shell powder after the release of organic fertilizer, preventing the oyster shell powder from being leached and lost in large quantities with rainwater at one time, maintaining a more lasting effect. At the same time, the first inner membrane separates the inner layer of oyster shell powder and the organic fertilizer layer to prevent the two from mixing and reacting chemically, which would result in a lower fertilizer efficiency of the organic fertilizer. DETAILED DESCRIPTION

[0038] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0039] The oyster shell powder used in the examples and comparative examples was obtained by grinding oyster shells and then calcining them at a high temperature of 800°C.

[0040] Example 1

[0041] The oyster shell-derived soil remediation agent of this embodiment comprises, from the inside out, an inner layer of oyster shell powder, an organic fertilizer layer, a beneficial bacteria layer, and an outer layer of oyster shell powder, wherein the weight ratio of the inner layer of oyster shell powder, the organic fertilizer layer, the beneficial bacteria layer, and the outer layer of oyster shell powder is 20:20:3:40; a first inner membrane is provided between the inner layer of oyster shell powder and the organic fertilizer layer, a second inner membrane is provided between the organic fertilizer layer and the beneficial bacteria layer, a third inner membrane is provided between the beneficial bacteria layer and the outer layer of oyster shell powder, and the outer layer of oyster shell powder is covered with an outer membrane.

[0042] The beneficial bacteria layer includes Bacillus licheniformis, Bacillus megaterium, Bacillus laterosporus and Trichoderma harzianum, and the ratio of each bacteria is 1:1:1:1.

[0043] The first inner membrane is mainly composed of chitosan, aqueous acrylic emulsion, carboxymethyl cellulose and deionized water, and the weight ratio of chitosan, aqueous acrylic emulsion, carboxymethyl cellulose and deionized water is 40:4:1:100; the coating amount of the first inner membrane is 20% of the weight of the inner layer of oyster shell powder.

[0044] The second inner film mainly consists of polyvinyl alcohol, carboxymethyl cellulose and deionized water, and the weight ratio of polyvinyl alcohol, carboxymethyl cellulose and deionized water is 100:10:300. The coating amount of the second inner film is 10% of the total weight of the coated materials.

[0045] The third inner film mainly consists of polyvinyl alcohol, carboxymethyl cellulose and deionized water, and the weight ratio of polyvinyl alcohol, carboxymethyl cellulose and deionized water is 100:10:300. The coating amount of the third inner film is 16% of the total weight of the coated materials.

[0046] The outer film mainly consists of carboxymethyl cellulose, sodium alginate and deionized water, and the weight ratio of carboxymethyl cellulose, sodium alginate and deionized water is 1:1:50. The coating amount of the outer film is 6% of the total weight of the coated materials.

[0047] The preparation method of the above-mentioned repair agent comprises the following steps:

[0048] (1) forming the inner layer oyster shell powder into particles having a water content of less than 10% to obtain oyster shell powder inner layer particles;

[0049] (2) Chitosan, aqueous acrylic emulsion, and deionized water were mixed, heated to 50° C., stirred for 30 minutes, and then carboxymethyl cellulose was added and stirred for 40 minutes to obtain the first inner envelope solution;

[0050] (3) atomizing the first inner coating liquid by high-speed hot air flow and uniformly spraying it onto the surface of the inner layer particles of the oyster shell powder, and drying the liquid to obtain coated inner layer particles of the oyster shell powder;

[0051] (4) crushing the organic fertilizer, mixing it with dextrin and water to form a slurry, placing it in a coating spraying system and evenly spraying it on the inner layer particles of the coated oyster shell powder, and drying it to obtain particles containing the organic fertilizer layer;

[0052] (5) Heat and stir polyvinyl alcohol and deionized water until dissolved, cool to 30°C, add carboxymethyl cellulose and continue stirring for 50 minutes to obtain the second inner envelope solution;

[0053] (6) atomizing the second inner coating liquid by high-speed hot air flow and uniformly spraying it on the surface of the particles containing the organic fertilizer layer, and drying it to obtain coated particles containing the organic fertilizer layer;

[0054] (7) After the beneficial bacteria are mixed with starch and water to form a slurry, the slurry is placed in a coating spraying system and evenly sprayed on the coated organic fertilizer layer particles, and dried to obtain the beneficial bacteria layer particles;

[0055] (8) First, prepare a third inner coating liquid according to the method of step (5), spray the third inner coating liquid evenly on the surface of the granules containing the beneficial bacteria layer, and dry it to obtain the coated granules containing the beneficial bacteria layer;

[0056] (9) After mixing the outer layer of oyster shell powder with dextrin and water to form a slurry, the slurry is placed in a coating spraying system and evenly sprayed on the coated particles containing the beneficial bacteria layer, and dried to obtain particles containing the outer layer of oyster shell powder;

[0057] (10) Sodium carboxymethyl cellulose, sodium alginate, and deionized water were stirred at 60°C for 30 min to obtain an outer coating liquid, which was evenly sprayed on the surface of the outer layer particles containing oyster shell powder and dried to obtain an oyster shell-derived soil remediation agent with a particle size of 5 mm.

[0058] Example 2

[0059] The oyster shell-derived soil remediation agent of this embodiment comprises, from the inside out, an inner layer of oyster shell powder, an organic fertilizer layer, a beneficial bacteria layer, and an outer layer of oyster shell powder, wherein the weight ratio of the inner layer of oyster shell powder, the organic fertilizer layer, the beneficial bacteria layer, and the outer layer of oyster shell powder is 35:30:8:60; a first inner membrane is provided between the inner layer of oyster shell powder and the organic fertilizer layer, a second inner membrane is provided between the organic fertilizer layer and the beneficial bacteria layer, a third inner membrane is provided between the beneficial bacteria layer and the outer layer of oyster shell powder, and the outer layer of oyster shell powder is covered with an outer membrane.

[0060] The beneficial bacteria layer includes Bacillus subtilis, Bacillus gelatinosa, Paecilomyces lilacinus and Trichoderma harzianum, and the ratio of each bacteria is 1:1:1:1.

[0061] The first inner membrane is mainly composed of chitosan, aqueous acrylic emulsion, carboxymethyl cellulose and deionized water, and the weight ratio of chitosan, aqueous acrylic emulsion, carboxymethyl cellulose and deionized water is 40:7:5:300; the coating amount of the first inner membrane is 25% of the weight of the inner layer of oyster shell powder.

[0062] The second inner film mainly consists of polyvinyl alcohol, carboxymethyl cellulose and deionized water, and the weight ratio of polyvinyl alcohol, carboxymethyl cellulose and deionized water is 100:18:400. The coating amount of the second inner film is 15% of the total weight of the coated materials.

[0063] The third inner film mainly consists of polyvinyl alcohol, carboxymethyl cellulose and deionized water, and the weight ratio of polyvinyl alcohol, carboxymethyl cellulose and deionized water is 100:18:400. The coating amount of the third inner film is 20% of the total weight of the coated materials.

[0064] The outer film mainly consists of carboxymethyl cellulose, sodium alginate and deionized water, and the weight ratio of carboxymethyl cellulose, sodium alginate and deionized water is 1:2:100; the coating amount of the outer film is 10% of the total weight of the coated materials.

[0065] The preparation method of the above-mentioned repair agent comprises the following steps:

[0066] (1) forming the inner layer oyster shell powder into particles having a water content of less than 10% to obtain oyster shell powder inner layer particles;

[0067] (2) Chitosan, aqueous acrylic emulsion, and deionized water were mixed, heated to 70°C, stirred for 20 minutes, and then carboxymethyl cellulose was added and stirred for 60 minutes to obtain the first inner envelope solution;

[0068] (3) atomizing the first inner coating liquid by high-speed hot air flow and uniformly spraying it onto the surface of the inner layer particles of the oyster shell powder, and drying the liquid to obtain coated inner layer particles of the oyster shell powder;

[0069] (4) crushing the organic fertilizer, mixing it with dextrin and water to form a slurry, placing it in a coating spraying system and evenly spraying it on the inner layer particles of the coated oyster shell powder, and drying it to obtain particles containing the organic fertilizer layer;

[0070] (5) Heat and stir polyvinyl alcohol and deionized water until dissolved, then cool to 50°C, add carboxymethyl cellulose and continue stirring for 30 minutes to obtain the second inner envelope solution;

[0071] (6) atomizing the second inner coating liquid by high-speed hot air flow and uniformly spraying it on the surface of the particles containing the organic fertilizer layer, and drying it to obtain coated particles containing the organic fertilizer layer;

[0072] (7) After the beneficial bacteria are mixed with starch and water to form a slurry, the slurry is placed in a coating spraying system and evenly sprayed on the coated organic fertilizer layer particles, and dried to obtain the beneficial bacteria layer particles;

[0073] (8) First, prepare a third inner coating liquid according to the method of step (5), spray the third inner coating liquid evenly on the surface of the granules containing the beneficial bacteria layer, and dry it to obtain the coated granules containing the beneficial bacteria layer;

[0074] (9) After mixing the outer layer of oyster shell powder with dextrin and water to form a slurry, the slurry is placed in a coating spraying system and evenly sprayed on the coated particles containing the beneficial bacteria layer, and dried to obtain particles containing the outer layer of oyster shell powder;

[0075] (10) Sodium carboxymethyl cellulose, sodium alginate, and deionized water were stirred at 70°C for 20 min to obtain an outer coating liquid, which was evenly sprayed on the surface of the outer layer particles containing oyster shell powder and dried to obtain an oyster shell-derived soil remediation agent with a particle size of 7 mm.

[0076] Example 3

[0077] The oyster shell-derived soil remediation agent of this embodiment includes, from the inside out, an inner layer of oyster shell powder, an organic fertilizer layer, a beneficial bacteria layer, and an outer layer of oyster shell powder. The weight ratio of the inner layer of oyster shell powder, the organic fertilizer layer, the beneficial bacteria layer, and the outer layer of oyster shell powder is (28:25:6:50); a first inner membrane is provided between the inner layer of oyster shell powder and the organic fertilizer layer, a second inner membrane is provided between the organic fertilizer layer and the beneficial bacteria layer, a third inner membrane is provided between the beneficial bacteria layer and the outer layer of oyster shell powder, and the outer layer of oyster shell powder is coated with an outer membrane.

[0078] The beneficial bacteria layer includes Bacillus licheniformis, Bacillus laterosporus, Bacillus gelatinosa and Paecilomyces lilacinus, and the ratio of each bacteria is 1:1:1:1.

[0079] The first inner membrane is mainly composed of chitosan, aqueous acrylic emulsion, carboxymethyl cellulose and deionized water, and the weight ratio of chitosan, aqueous acrylic emulsion, carboxymethyl cellulose and deionized water is 40:5:3:200; the coating amount of the first inner membrane is 22% of the weight of the inner layer of oyster shell powder.

[0080] The second inner film mainly consists of polyvinyl alcohol, carboxymethyl cellulose and deionized water, and the weight ratio of polyvinyl alcohol, carboxymethyl cellulose and deionized water is 100:14:350. The coating amount of the second inner film is 12% of the total weight of the coated materials.

[0081] The third inner film mainly consists of polyvinyl alcohol, carboxymethyl cellulose and deionized water, and the weight ratio of polyvinyl alcohol, carboxymethyl cellulose and deionized water is 100:14:350. The coating amount of the third inner film is 18% of the total weight of the coated materials.

[0082] The outer film mainly consists of carboxymethyl cellulose, sodium alginate and deionized water, and the weight ratio of carboxymethyl cellulose, sodium alginate and deionized water is 1:1.5:80. The coating amount of the outer film is 8% of the total weight of the coated materials.

[0083] The preparation method of the above-mentioned repair agent comprises the following steps:

[0084] (1) forming the inner layer oyster shell powder into particles having a water content of less than 10% to obtain oyster shell powder inner layer particles;

[0085] (2) Chitosan, aqueous acrylic emulsion, and deionized water were mixed, heated to 60°C, stirred for 25 minutes, and then carboxymethyl cellulose was added and stirred for 50 minutes to obtain the first inner envelope solution;

[0086] (3) atomizing the first inner coating liquid by high-speed hot air flow and uniformly spraying it onto the surface of the inner layer particles of the oyster shell powder, and drying the liquid to obtain coated inner layer particles of the oyster shell powder;

[0087] (4) crushing the organic fertilizer, mixing it with dextrin and water to form a slurry, placing it in a coating spraying system and evenly spraying it on the inner layer particles of the coated oyster shell powder, and drying it to obtain particles containing the organic fertilizer layer;

[0088] (5) Heat and stir polyvinyl alcohol and deionized water until dissolved, cool to 40°C, add carboxymethyl cellulose and continue stirring for 40 minutes to obtain the second inner envelope solution;

[0089] (6) atomizing the second inner coating liquid by high-speed hot air flow and uniformly spraying it on the surface of the particles containing the organic fertilizer layer, and drying it to obtain coated particles containing the organic fertilizer layer;

[0090] (7) After the beneficial bacteria are mixed with starch and water to form a slurry, the slurry is placed in a coating spraying system and evenly sprayed on the coated organic fertilizer layer particles, and dried to obtain the beneficial bacteria layer particles;

[0091] (8) First, prepare a third inner coating liquid according to the method of step (5), spray the third inner coating liquid evenly on the surface of the granules containing the beneficial bacteria layer, and dry it to obtain the coated granules containing the beneficial bacteria layer;

[0092] (9) After mixing the outer layer of oyster shell powder with dextrin and water to form a slurry, the slurry is placed in a coating spraying system and evenly sprayed on the coated particles containing the beneficial bacteria layer, and dried to obtain particles containing the outer layer of oyster shell powder;

[0093] (10) Sodium carboxymethyl cellulose, sodium alginate, and deionized water were stirred at 60°C for 25 min to obtain an outer coating liquid, which was evenly sprayed on the surface of the outer layer particles containing oyster shell powder and dried to obtain an oyster shell-derived soil remediation agent with a particle size of 6 mm.

[0094] Comparative Example 1: The soil remediation agent of this comparative example is coated oyster shell powder particles, and the coating method is the same as the coating method of the inner layer of oyster shell powder in Example 1.

[0095] Comparative Example 2: The soil remediation agent of this comparative example is a mixture of coated oyster shell powder particles and organic fertilizer. The coating method of the oyster shell powder is the same as the coating method of the inner layer of the oyster shell powder in Example 1, and the organic fertilizer is the same as the organic fertilizer in Example 1.

[0096] Comparative Example 3: The soil remediation agent of this comparative example is a mixture of coated oyster shell powder particles, organic fertilizer and microbial fertilizer. The coating method of the oyster shell powder is the same as the coating method of the inner layer of the oyster shell powder in Example 1, the organic fertilizer is the same as the organic fertilizer in Example 1, and the microbial fertilizer contains the beneficial bacteria in Example 1.

[0097] The applicant used the soil remediation agents of the above-mentioned embodiments and comparative examples to conduct soil remediation tests in sugarcane fields in Longan County, Guangxi (Longan County is located in the Dashi Mountain area with karst landforms). The test plots were tested in 2021. The basic chemical properties of the soil were: pH 3.75, soil organic matter content was 12-16 g / kg, soil total nitrogen content was 0.4-0.6 g / kg, soil available phosphorus content was 110-130 mg / kg, soil available potassium content was 100-110 mg / kg, soil acidification was serious, and soil fertility was poor. Basic physical properties of the soil: the soil was compacted, and the total porosity was less than 28%. Each embodiment and comparative example was repeated 3 times, and each repeated area was 20 m 2 The method of applying the soil remediation agent is: after the planting trenches for the newly planted sugarcane in 2021 are opened, each group will sprinkle an equal amount of soil remediation agent into the bottom of the planting trenches.

[0098] After the sugarcane was harvested in 2022, soil profiles were dug from the three sampling points of each embodiment and comparative example, and the soil physical properties, field water holding capacity, soil specific gravity and moisture content were measured. The total porosity was calculated based on the bulk density, field water holding capacity, soil specific gravity and moisture content, and the average value was calculated. A 1 kg sample of soil from the 0-40 cm tillage layer was dug from the profile, air-dried, and the soil pH, organic matter, total nitrogen, available phosphorus and available potassium were measured, and the average value was calculated. The results are shown in Table 1.

[0099] The Shannon index and Chao1 index of community diversity of each embodiment and comparative example were detected. The Shannon index is an indicator of microbial diversity. The larger the value, the greater the species diversity. The Chao1 index is an indicator of microbial species richness. The larger the value, the richer the species. The results are shown in Table 2.

[0100] Table 1 Physical and chemical properties of soil

[0101]

[0102] It can be seen from the examples that the soil remediation agent of the present invention can increase the total porosity of the soil, reduce soil acidity, and improve soil fertility. From the data of Example 1 and Comparative Example 1, it can be seen that when oyster shell powder is used alone as a remediation agent, the soil has a better improvement in acidity, but the soil fertility and porosity are not improved, and the remediation effect is not ideal. From the data of Example 1 and Comparative Example 2, it can be seen that without designing a multi-layer coating structure, oyster shell powder and organic fertilizer are directly compounded and used, which is difficult to effectively improve soil fertility. It is possible that direct mixing of oyster shell powder and organic fertilizer will reduce the fertilizer effect of organic fertilizer. From the data of Example 1 and Comparative Example 3, it can be seen that without designing a multi-layer coating structure, oyster shell powder and organic fertilizer and microbial fertilizer are directly compounded and used, which is difficult to effectively improve soil fertility. It is possible that direct mixing of oyster shell powder and organic fertilizer and beneficial bacteria will reduce the fertilizer effect of organic fertilizer and inhibit the growth of soil microorganisms.

[0103] Table 2 Diversity of soil microbial community structure

[0104]

[0105] Table 2 shows that the soil remediation agent of the present invention can increase the abundance of soil microorganisms. Without designing a multi-layer coating structure, the oyster shell powder was directly compounded with organic fertilizer, microbial fertilizer, and beneficial bacteria, but the soil microbial community was not significantly restored.

[0106] In order to prove the long-term effect of the soil remediation agent of the present invention, the applicant conducted the following test on the above-mentioned test plot (the basic physical and chemical properties of the soil are the same as above): the test was divided into an experimental group and a control group 1 and a control group 2, each group was set up with 3 repetitions, and each repetition area was 20m 2 .in,

[0107] The experimental group used the soil remediation agent of Example 1, and the method of use was: after the planting trenches for newly planted sugarcane were dug in 2021, the soil remediation agent was sprinkled into the bottom of the planting trenches, that is, it was used once a year.

[0108] Control group 1 uses the soil remediation agent of comparative example 3. The usage method is: after the planting trenches for newly planted sugarcane are opened in 2021, the soil remediation agent is sprinkled into the bottom of the planting trenches, that is, it is used once a year.

[0109] Control group 2 uses the soil remediation agent of comparative example 3. The usage method is: after the planting furrows for newly planted sugarcane are opened in April 2021, the soil remediation agent is sprinkled into the bottom of the planting furrow. When the sugarcane is mid-term soiling, a layer of soil remediation agent is applied between the sugarcane rows, that is, it is used twice a year.

[0110] The above soil remediation agents were used in the same amount each time, and no other soil conditioners were used during the period. Soil was collected in March 2022, and the physical and chemical properties and pH changes of each group of soil were tested and statistically analyzed. The results are shown in Table 3:

[0111] Table 3 Physical and chemical properties of soil in each group

[0112]

[0113] Table 3 shows that the soil remediation agent of Comparative Example 3 needs to be used twice a year to approach or achieve the effect of the soil remediation agent of the present invention when used once a year. It can be seen that the soil remediation agent of the present invention can maintain a more lasting effect.

[0114] In summary, the soil remediation agent of the present invention adopts a multi-layer coating design, which includes, from the outside to the inside, an outer coating, an oyster shell powder outer layer, a third inner coating, a beneficial bacteria layer, a second inner coating, an organic fertilizer layer, a first inner coating, and an oyster shell powder inner layer. It can not only kill bacteria, increase pH, and increase soil nutrients and beneficial bacteria content, but also alleviate the one-time large-scale leaching loss of oyster shell powder with rainwater, maintaining a more lasting effect.

[0115] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. An oyster shell-derived soil remediation agent, characterized in that: It comprises an oyster shell powder inner layer, an organic fertilizer layer, a beneficial bacteria layer and an oyster shell powder outer layer, wherein the weight ratio of the oyster shell powder inner layer, the organic fertilizer layer, the beneficial bacteria layer and the oyster shell powder outer layer is (20-35): (20-30): (3-8): (40-60); A first inner envelope is provided between the inner layer of oyster shell powder and the organic fertilizer layer, a second inner envelope is provided between the organic fertilizer layer and the beneficial bacteria layer, a third inner envelope is provided between the beneficial bacteria layer and the outer layer of oyster shell powder, and the outer layer of oyster shell powder is coated with an outer envelope; The first inner envelope is mainly composed of chitosan, aqueous acrylic emulsion, carboxymethyl cellulose and deionized water, wherein the weight ratio of chitosan, aqueous acrylic emulsion, carboxymethyl cellulose and deionized water is 40:4-7:1-5:100-300; the coating amount of the first inner envelope is 20-25% of the weight of the inner layer of the oyster shell powder; The second inner film is mainly composed of polyvinyl alcohol, carboxymethyl cellulose and deionized water, and the weight ratio of polyvinyl alcohol, carboxymethyl cellulose and deionized water is 100:10-18:300-400; the coating amount of the second inner film is 10-15% of the total weight of the coated material; The third inner film is mainly composed of polyvinyl alcohol, carboxymethyl cellulose and deionized water, and the weight ratio of polyvinyl alcohol, carboxymethyl cellulose and deionized water is 100:10-18:300-400; the coating amount of the third inner film is 16-20% of the total weight of the coated material; The outer film mainly consists of carboxymethyl cellulose, sodium alginate and deionized water, and the weight ratio of the carboxymethyl cellulose, sodium alginate and deionized water is 1:1-2:50-100; the coating amount of the outer film is 6-10% of the total weight of the coated material.

2. The oyster shell-derived soil remediation agent according to claim 1, characterized in that: The beneficial bacteria layer comprises one or more of Bacillus licheniformis, Bacillus megaterium, Bacillus laterosporus, Bacillus subtilis, Bacillus gelatinosa, Paecilomyces lilacinus and Trichoderma harzianum.

3. The oyster shell-derived soil remediation agent according to any one of claims 1 to 2, characterized in that: The preparation method of the repair agent comprises the following steps: (1) preparing the inner layer oyster shell powder into particles having a water content of less than 10% to obtain oyster shell powder inner layer particles; (2) Chitosan, aqueous acrylic emulsion and deionized water are mixed, heated to 50-70°C, stirred for 20-30 minutes, and then carboxymethyl cellulose is added and stirred for 40-60 minutes to obtain the first inner envelope solution; (3) spraying the first inner coating liquid uniformly onto the surface of the inner layer particles of the oyster shell powder by atomizing with a high-speed hot air flow, and drying to obtain coated inner layer particles of the oyster shell powder; (4) crushing the organic fertilizer, mixing it with a binder and water to form a slurry, placing it in a coating spraying system, and evenly spraying it on the inner layer particles of the coated oyster shell powder, and drying it to obtain particles containing an organic fertilizer layer; (5) Heat and stir polyvinyl alcohol and deionized water until dissolved, cool to 30-50°C, add carboxymethyl cellulose and continue stirring for 30-50 minutes to obtain the second inner envelope solution; (6) atomizing the second inner coating liquid by high-speed hot air flow and uniformly spraying it onto the surface of the particles containing the organic fertilizer layer, and drying it to obtain coated particles containing the organic fertilizer layer; (7) After the beneficial bacteria are mixed with fillers and water to form a slurry, the slurry is placed in a coating spraying system and evenly sprayed on the coated organic fertilizer layer particles, and dried to obtain the beneficial bacteria layer particles; (8) First, prepare a third inner coating liquid according to the method of step (5), spray the third inner coating liquid evenly on the surface of the granules containing the beneficial bacteria layer, and dry it to obtain coated granules containing the beneficial bacteria layer; (9) After mixing the outer layer of oyster shell powder with a binder and water to form a slurry, the slurry is placed in a coating spraying system and evenly sprayed on the coated particles containing the beneficial bacteria layer, and dried to obtain particles containing the outer layer of oyster shell powder; (10) Sodium carboxymethyl cellulose, sodium alginate and deionized water are stirred at 60-70° C. for 20-30 minutes to obtain an outer coating liquid, and the outer coating liquid is evenly sprayed on the surface of the outer layer particles containing oyster shell powder, and dried to obtain the oyster shell-derived soil remediation agent.

4. The oyster shell-derived soil remediation agent according to claim 3, characterized in that: The adhesive in step (4) and step (9) is dextrin.

5. The oyster shell-derived soil remediation agent according to claim 3, characterized in that: The filler in step (7) is starch.

6. The oyster shell-derived soil remediation agent according to claim 1, characterized in that: The particle size of the soil remediation agent is 5-8 mm.

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