Soil conditioner based on fish manure and preparation method thereof

Abstract

The invention discloses a soil conditioner based on fish manure and a preparation method thereof, and belongs to the technical field of soil conditioners. Comprising the following steps: mixing and stirring fish manure and humus soil, adding zymophyte and water, and continuously stirring and fermenting to obtain an organic fertilizer; the obtained organic fertilizer, the modified biomass charcoal, gamma polyglutamic acid, vermiculite and a microbial agent are mixed and granulated, and the soil conditioner containing the fish manure is obtained. The modified biomass charcoal and the modified chitosan are combined together for use, the porous water absorption characteristic of the biomass charcoal and the efficient water holding capacity of the chitosan are utilized, the synergistic use of the biomass charcoal and the chitosan not only can improve the water retention capacity of soil, but also can effectively passivate the heavy metal effect, and the fixing effect of the heavy metal is remarkably improved; therefore, heavy metal entering a food chain through plants is reduced, and harm to a human body is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of soil conditioners, and in particular to a soil conditioner based on fish excrement and a preparation method thereof. Background Art

[0002] Soil conditioners are a general term for single or complex matrices that can improve soil properties and have a positive impact on plant yields. Natural soil conditioners can be roughly divided into two categories: organic conditioners and mineral conditioners. Organic conditioners include compost, livestock and poultry manure, plant residues, biochar, slaughterhouse waste, sewage sludge, etc.; mineral conditioners include volcanic rocks, clay minerals, lime, eggshells, and gypsum. The application of alkaline conditioners can effectively improve soil acidification. The compounds in organic fertilizers can also chelate with soil aluminum ions, thereby improving the acidity and alkalinity of the soil. At present, soil conditioners have been widely used in the remediation of degraded soils in abandoned mines. Soil conditioners can improve soil fertility by maintaining high microbial activity in the soil and increasing nutrient absorption by plants. In addition, soil conditioners can also improve soil structure by increasing the stability of soil aggregates, affecting soil bulk density and soil water-gas relationship.

[0003] In traditional soil conditioners, there are usually problems of destruction of soil microbial activity and chemical residues, which have an adverse effect on the soil ecological environment and crop growth. In order to increase crop yields, local people burn organic matter and return it to the fields. Organic solid wastes such as biochar and compost can be converted into soil conditioners in different forms, bringing a win-win situation for improving soil productivity and environmentally friendly agriculture. Biochar is a carbon-rich and stable product formed by pyrolysis and carbonization of biomass under low temperature and anaerobic conditions. It has hydrophilic groups such as hydroxyl, carboxyl, aliphatic double bonds and aromatic structures, and has a unique physical structure of loose porosity and a large specific surface area. The unique structure of biochar determines that it has special properties and is a natural soil conditioner. The application of biochar can increase soil microbial activity, increase crop yields, and improve the permeability of water, fertilizer, and gas; adsorb heavy metals and organic pollutants, and have a fixation and passivation effect on toxic substances; the adsorption capacity of biochar can also act on reducing the emission of greenhouse gases such as methane. Biomass materials that can be used to prepare biochar include various natural organic matter and their derivatives, such as herbs, wood waste, agricultural waste, municipal solid waste, livestock manure, aquatic plants and algae. Converting agricultural waste into biochar can reduce the pollution of agricultural waste to the environment and can also replace non-renewable energy with renewable energy.

[0004] A Chinese invention patent (application number: 202211015588.9) discloses a biochar-based soil conditioner and a preparation method thereof. The conditioner of the present invention is prepared from the following raw materials in parts by weight: 30-60 parts of organic fertilizer components, 5-10 parts of urea, 5-10 parts of potassium dihydrogen phosphate, 4-80 parts of modified biochar, and 4-12 parts of composite microbial agents. The patent mainly has the following problems: weak ability to repair contaminated soil and low bioavailability. Therefore, the present invention provides a soil conditioner for fish feces and a preparation method thereof. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a soil conditioner based on fish feces and a preparation method thereof.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for preparing a soil conditioner based on fish feces comprises the following steps:

[0008] S1: Mixing fish excrement and humus soil, adding fermentation bacteria and water, and continuing to stir and ferment to obtain organic fertilizer;

[0009] S2: the organic fertilizer, modified biochar, gamma-polyglutamic acid, vermiculite and microbial agent obtained in step S1 are mixed and granulated to obtain a soil conditioner for fish feces.

[0010] Restorative soil conditioners containing biomass carbon can effectively repair damaged soil, improve soil quality, enhance soil biological activity and promote healthy agricultural development by combining animal and plant waste, biochar technology and soil remediation theory.

[0011] The present invention uses fish feces as animal feces, and uses it and humus soil as raw materials for preparing organic fertilizer. After fermentation, the looseness of the humus soil can be further improved, the water permeability and ventilation performance of the humus soil can be improved, and the water and fertilizer retention capacity is very good. Moreover, after the animal feces are fermented, the macromolecular substances in the feces are dissolved, and the small molecular water chemical substances can be directly used for crops, thereby increasing the nutrient content in the organic fertilizer and improving the fertility.

[0012] Using organic fertilizer, modified biochar, γ-polyglutamic acid, vermiculite and microbial agents as soil conditioners in a certain proportion can effectively improve soil compaction, reduce salinization and heavy metal pollution. Polyglutamic acid has multiple functions such as slow release and moisturizing. Polyglutamic acid itself is not a fertilizer, but it can be used as a fertilizer synergist. The addition of polyglutamic acid can increase crop yields and improve soil quality. Polyglutamic acid has a chelating effect on metal ions. Polyglutamic acid can enrich trace elements for plants, allowing plants to use fertilizers more effectively and improve crop yields and quality. Vermiculite can be used to improve the structure of sediment, improve the water storage and retention performance of the formed repair matrix, and improve the air permeability and water content of the repair base. Since vermiculite itself contains a large amount of potassium, magnesium, calcium, manganese, zinc and other trace elements, as the plant grows, the trace elements in it are slowly released, which can provide certain nutrients for plant growth and improve plant growth effects. The pores of modified biochar can reach the nanometer level, which is very conducive to the attachment and growth of microorganisms inside it. It also has a good protective effect on the loaded microorganisms, which is conducive to the cultivation of beneficial functional bacteria in the soil. It can be used to prepare carbon-based soil remediation materials and repair soil heavy metal pollution. Each substance has the same function and plays a different role, which can effectively improve soil compaction, reduce salinization and heavy metal pollution.

[0013] Preferably, the method for preparing the soil conditioner based on fish feces comprises the following steps:

[0014] S1 8-20 parts by weight of fish excrement and 3-6 parts by weight of humus soil are mixed and stirred at 400-800 rpm for 30-70 min, fermentation bacteria with a mass of 0.5-4 wt% of fish excrement and 15-30 parts by weight of water are added, stirring is continued for 20-50 min, and fermentation is carried out at 32-38° C. and 100-300 rpm for 10-30 d. During the fermentation process, the material is turned over every 18-28 h; after fermentation, it is air-dried to a moisture content of 8-15% to obtain organic fertilizer;

[0015] S2: The organic fertilizer, modified biochar, gamma-polyglutamic acid, vermiculite and microbial agent obtained in step S1 are mixed in a mass ratio of (15-30):(20-40):(0.8-2):(3-8):(0.8-2), stirred at 34-45°C and 400-700rpm for 0.5-3h, granulated, and then dried at 35-45°C for 0.5-2h to obtain a soil conditioner for fish feces.

[0016] The fermentation bacteria is at least one of Candida parapsilosis, Bacillus colloids, and Bacillus subtilis; preferably, the fermentation bacteria is composed of Candida parapsilosis, Bacillus colloids, and Bacillus subtilis in a mass ratio of (1-3):(0.5-2):(2-4).

[0017] The microbial agent is at least one of aquatic Rahnella and rosea Coxsackie 1-7R; preferably, the microbial agent is composed of aquatic Rahnella and rosea Coxsackie 1-7R in a mass ratio of 1:(1-2).

[0018] The method for preparing the modified biochar comprises the following steps:

[0019] N1: drying, crushing and carbonizing apple peel to obtain biochar; adding the biochar to N-methylpyrrolidone and ultrasonicating it; then adding it to acetic acid solution of humic acid and ultrasonicating it to obtain preliminary modified biochar;

[0020] N2: mixing chitosan and acetic acid aqueous solution, adding nicotinic acid acyl-β-D-glucuronic acid and an activator, and continuing to stir the reaction to obtain modified chitosan;

[0021] N3: Mix the above preliminary modified biochar and the above modified chitosan, heat and stir, then add glutaraldehyde and continue stirring to obtain modified biochar.

[0022] Chitosan has multiple biological activities and biodegradability, and the surface of chitosan has abundant amino and hydroxyl functional groups, which are good adsorption sites to bind heavy metals and can passivate heavy metals more efficiently. However, when used alone, it is easy to stick together, and the tight spatial form will reduce the adsorption efficiency and is very unstable. When biochar is used alone, it has a good pollutant adsorption capacity, but its passivation effect on heavy metals is poor. Therefore, the present invention effectively combines the two for use, which improves the ease of chitosan to stick together, and at the same time can further improve the adsorption effect of biochar on heavy metals, playing a synergistic role.

[0023] Modified chitosan can increase the water absorption and water holding capacity of soil because its molecular structure contains many hydroxyl and amino hydrophilic groups, which can effectively absorb and retain water, thereby improving the water retention of soil. Modified chitosan forms a water-retaining layer in the soil, reducing water evaporation and leakage, which helps to maintain soil moisture, especially under drought conditions, and can significantly improve the drought resistance of crops. Improve soil structure: Modified chitosan is relatively loose, making the soil more loose, which is conducive to the penetration and storage of water. At the same time, good soil structure also promotes the growth of plant roots and improves water use efficiency. Modified chitosan can also chelate with heavy metal ions (such as lead, cadmium, zinc, etc.) to form stable complexes, thereby fixing heavy metals in the soil and reducing their mobility and bioavailability; by combining with heavy metal ions, modified chitosan can significantly reduce the absorption and accumulation of heavy metals by plants, reduce the risk of heavy metals entering the food chain, reduce the plant absorption of heavy metals, and protect crops and the ecological environment.

[0024] The modified biochar prepared by the method is rich in a large number of micropores, has a large specific surface area and adsorption performance, and when added to the soil, it can not only replenish the organic matter content, water and nutrients of the soil, and improve soil fertility; by adsorbing and slowly releasing nutrients, it increases nutrient utilization efficiency and reduces nutrient loss and waste; it has good water retention performance, can prevent excessive evaporation and loss of water, help plants better absorb water, and promote healthy growth of plants; in addition, the addition of humic acid can improve the soil to a certain extent, stimulate crop growth and other functions; in addition, the basic structure of humic acid macromolecules is an aromatic ring and an alicyclic ring, and the ring is connected with functional groups such as carboxyl, hydroxyl, and carbonyl, which have exchange and adsorption effects with metal ions and can also reduce heavy metals in the soil to a certain extent, and promote the growth of crops.

[0025] In summary, the present invention combines modified biochar and modified chitosan for use, and utilizes the porous water absorption characteristics of biochar and the efficient water holding capacity of chitosan to form a complementary water retention system in the soil; the water adsorbed and stored by biochar is gradually released through the colloid layer of chitosan to provide a continuous water supply. Through the combined action of different adsorption and chelation mechanisms, the fixation effect of heavy metals is significantly improved, the heavy metals in the soil are fixed, and the absorption by the roots of crops is reduced, thereby reducing the entry of heavy metals into the food chain through plants and reducing the harm to the human body.

[0026] The synergistic use of the two can more effectively reduce the mobility and bioavailability of heavy metals, which can not only improve the water retention capacity of the soil, but also effectively passivate the effects of heavy metals, improve the soil ecological environment, improve soil permeability and organic matter content, and improve soil fertility.

[0027] Preferably, the method for preparing the modified biochar comprises the following steps:

[0028] N1 Dry and crush the apple peel, pass it through a 20-60 mesh sieve, and then place it in a 650-900℃ tubular furnace for carbonization for 1-5h to obtain biochar; take 8-15 parts by weight of biochar and add it to 400-600 parts by weight of N-methylpyrrolidone, and ultrasonicate it for 0.3-1h at an ultrasonic frequency of 40-80kHz, an ultrasonic power of 150-260W, and 35-45℃; then add 10-20 parts by weight of 20-40wt% humic acid acetic acid solution, continue ultrasonic treatment for 2-5h, centrifuge, vacuum dry, grind and pass through a 80-200 mesh sieve to obtain preliminary modified biochar;

[0029] N2: 2-5 parts by weight of chitosan and 80-200 parts by weight of 1-3wt% acetic acid aqueous solution are mixed, stirred at 50-70°C and 400-800rpm for 20-50min, 1-3 parts by weight of nicotinic acid acyl-β-D-glucuronic acid and 0.1-0.5 parts by weight of an activator are added, wherein the activator is composed of 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide in a ratio of 5-8:1, and the reaction is continued by stirring for 3-6h; dialyzed, and freeze-dried to obtain modified chitosan;

[0030] N3: Mix 3-8 parts by weight of the above-mentioned preliminary modified biochar and 2-5 parts by weight of the above-mentioned modified chitosan, stir at 30-50°C and 100-300rpm for 20-50min, add 0.5-2 parts by weight of glutaraldehyde and continue stirring for 10-30min, adjust the pH to 8.5-9.5, let stand for 0.5-2h, filter and dry to obtain modified biochar.

[0031] A soil conditioner based on fish excrement is prepared by the method.

[0032] Beneficial effects of the present invention: The present invention provides a soil conditioner based on fish feces and a preparation method thereof. The present invention combines modified biochar and modified chitosan for use, and utilizes the porous water absorption characteristics of biochar and the efficient water holding capacity of chitosan to form a complementary water retention system in the soil; the water adsorbed and stored by the biochar is gradually released through the colloid layer of chitosan to provide a continuous water supply. The coordinated use of the two can more effectively reduce the mobility and bioavailability of heavy metals, which can not only improve the water retention performance of the soil, but also effectively passivate the effects of heavy metals, improve the soil ecological environment, improve soil permeability and organic matter content, and improve soil fertility. Through the combined action of different adsorption and chelation mechanisms, the fixation effect of heavy metals is significantly improved, the heavy metals in the soil are fixed, and the absorption of crop roots is reduced, thereby reducing the entry of heavy metals into the food chain through plants and reducing harm to the human body. DETAILED DESCRIPTION

[0033] The above content of the present invention is further described in detail below in conjunction with specific implementation modes, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments.

[0034] Introduction of some raw materials in this application:

[0035] Poly-γ-glutamic acid was purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd. with a molecular weight of 1.1 million g / mol.

[0036] Chitosan was purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd., product number: 680064, molecular weight: 3000 g / mol.

[0037] Candida parapsilosis was purchased from the China Industrial Microbiological Culture Collection Center, with the strain number CICC1257. Its main uses are: organic acids produced by growth metabolism, hormones, amino acids, polysaccharides and other substances produced to promote the growth of crops.

[0038] Bacillus subtilis was purchased from the China Agricultural Microbial Culture Collection Center, with the strain number: ACCC 19749. Its main use is to promote the release of phosphorus and potassium in the soil and can be used to produce microbial fertilizers.

[0039] Bacillus subtilis was purchased from the China Agricultural Microbial Culture Collection Center, with the strain number: ACCC 60364. Its main uses are: it can inhibit the growth of miscellaneous bacteria during the fermentation process, form beneficial fermentation flora, accelerate the fermentation speed, and can be used for the production of microbial fertilizers.

[0040] Aquatic Rahnella was purchased from the China General Microbial Culture Collection Center, with the collection number: CGMCC 1.6278. Its main uses are: it has strong resistance and adsorption capacity, can release phosphate by degrading phytic acid, and further induce the formation of basic zinc phosphate mineral crystals, thereby reducing heavy metals in the soil, and can be used for green and sustainable remediation of heavy metal-contaminated soil.

[0041] Coxsackie rosea I-7R was purchased from the China Agricultural Microbial Culture Collection Center, with the strain number ACCC04460. Its main uses include adapting to special environments such as saline-alkali land, effectively secreting active substances such as auxins to promote plant growth and develop plant root systems; it has the function of heavy metal sedimentation and can effectively reduce the content of heavy metal elements in the soil.

[0042] Example 1

[0043] The method for preparing a soil conditioner based on fish feces comprises the following steps:

[0044] S1: 10 parts by weight of fish excrement and 4 parts by weight of humus soil are mixed and stirred at 600 rpm for 45 minutes, fermentation bacteria with a mass of 1 wt% of fish excrement and 18 parts by weight of water are added, and stirring is continued for 30 minutes. The mixture is fermented at 34°C and 200 rpm for 15 days. During the fermentation process, the material is turned over every 24 hours. After fermentation, the mixture is air-dried to a moisture content of 10% to obtain an organic fertilizer. The fermentation bacteria are composed of Candida parapsilosis, Bacillus subtilis, and Bacillus subtilis in a mass ratio of 2:1:3.

[0045] S2: the organic fertilizer, modified biochar, gamma-polyglutamic acid, vermiculite and microbial agent obtained in step S1 are mixed in a mass ratio of 20:30:1:5:1, stirred at 38°C and 600rpm for 1h, granulated, and then dried at 40°C for 1h to obtain a soil conditioner for fish feces.

[0046] The microbial agent is composed of aquatic Rahnella and rosea I-7R in a mass ratio of 1:1.2.

[0047] The method for preparing the modified biochar comprises the following steps:

[0048] N1 Dry and crush the apple peel, pass it through a 40-mesh sieve, and then place it in a 700°C tubular furnace for carbonization for 1.5 hours to obtain biochar; take 10 parts by weight of biochar and add it to 500 parts by weight of N-methylpyrrolidone, and ultrasonicate it at an ultrasonic frequency of 60kHz, an ultrasonic power of 200W, and 40°C for 0.5 hours; then add 15 parts by weight of 30wt% humic acid acetic acid solution, continue ultrasonic treatment for 3 hours, centrifuge, vacuum dry, and grind it through a 100-mesh sieve to obtain preliminary modified biochar;

[0049] N2: 3 parts by weight of chitosan and 120 parts by weight of 2 wt% acetic acid aqueous solution were mixed, stirred at 60°C and 600 rpm for 30 min, 1.5 parts by weight of nicotinic acid acyl-β-D-glucuronic acid and 0.3 parts by weight of an activator were added, wherein the activator was composed of 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide in a ratio of 6:1, and the reaction was continued by stirring for 4 h; dialyzed, and freeze-dried to obtain modified chitosan;

[0050] N3: Mix 5 parts by weight of the preliminary modified biochar and 3 parts by weight of the modified chitosan, stir at 40°C and 200 rpm for 30 min, add 1 part by weight of glutaraldehyde and continue stirring for 20 min, adjust the pH to 9, let stand for 1 h, filter, and dry to obtain modified biochar.

[0051] Comparative Example 1

[0052] The method for preparing a soil conditioner based on fish feces comprises the following steps:

[0053] S1: 10 parts by weight of fish excrement and 4 parts by weight of humus soil are mixed and stirred at 600 rpm for 45 minutes, fermentation bacteria with a mass of 1 wt% of fish excrement and 18 parts by weight of water are added, and stirring is continued for 30 minutes. The mixture is fermented at 34°C and 200 rpm for 15 days. During the fermentation process, the material is turned over every 24 hours. After fermentation, the mixture is air-dried to a moisture content of 10% to obtain an organic fertilizer. The fermentation bacteria are composed of Candida parapsilosis, Bacillus subtilis, and Bacillus subtilis in a mass ratio of 2:1:3.

[0054] S2: The organic fertilizer, biochar, gamma-polyglutamic acid, vermiculite and microbial agent obtained in step S1 are mixed in a mass ratio of 20:30:1:5:1, stirred at 38°C and 600rpm for 1h, granulated, and then dried at 40°C for 1h to obtain a soil conditioner for fish feces.

[0055] The microbial agent is composed of aquatic Rahnella and rosea I-7R in a mass ratio of 1:1.2.

[0056] The method for preparing biomass charcoal comprises the following steps: N1 drying and crushing apple peel, passing through a 40-mesh sieve, and then placing the peel in a 700° C. tubular furnace for carbonization for 1.5 hours to obtain biomass charcoal.

[0057] Comparative Example 2

[0058] The method for preparing a soil conditioner based on fish feces comprises the following steps:

[0059] S1: 10 parts by weight of fish excrement and 4 parts by weight of humus soil are mixed and stirred at 600 rpm for 45 minutes, fermentation bacteria with a mass of 1 wt% of fish excrement and 18 parts by weight of water are added, and stirring is continued for 30 minutes. The mixture is fermented at 34°C and 200 rpm for 15 days. During the fermentation process, the material is turned over every 24 hours. After fermentation, the mixture is air-dried to a moisture content of 10% to obtain an organic fertilizer. The fermentation bacteria are composed of Candida parapsilosis, Bacillus subtilis, and Bacillus subtilis in a mass ratio of 2:1:3.

[0060] S2: the organic fertilizer, modified biochar, gamma-polyglutamic acid, vermiculite and microbial agent obtained in step S1 are mixed in a mass ratio of 20:30:1:5:1, stirred at 38°C and 600rpm for 1h, granulated, and then dried at 40°C for 1h to obtain a soil conditioner for fish feces.

[0061] The microbial agent is composed of aquatic Rahnella and rosea I-7R in a mass ratio of 1:1.2.

[0062] The modified biochar preparation method comprises the following steps: drying and crushing apple peel, passing through a 40-mesh sieve, and then placing the apple peel in a 700°C tubular furnace for carbonization for 1.5 hours to obtain biochar; taking 10 parts by weight of the biochar and adding it to 500 parts by weight of N-methylpyrrolidone, ultrasonically treating it for 0.5 hours at an ultrasonic frequency of 60kHz, an ultrasonic power of 200W, and a temperature of 40°C; then adding 15 parts by weight of an acetic acid solution containing 30wt% humic acid, continuing ultrasonic treatment for 3 hours, centrifuging, vacuum drying, and grinding and passing through a 100-mesh sieve to obtain the modified biochar.

[0063] Comparative Example 3

[0064] The method for preparing a soil conditioner based on fish feces comprises the following steps:

[0065] S1: 10 parts by weight of fish excrement and 4 parts by weight of humus soil are mixed and stirred at 600 rpm for 45 minutes, fermentation bacteria with a mass of 1 wt% of fish excrement and 18 parts by weight of water are added, and stirring is continued for 30 minutes. The mixture is fermented at 34°C and 200 rpm for 15 days. During the fermentation process, the material is turned over every 24 hours. After fermentation, the mixture is air-dried to a moisture content of 10% to obtain an organic fertilizer. The fermentation bacteria are composed of Candida parapsilosis, Bacillus subtilis, and Bacillus subtilis in a mass ratio of 2:1:3.

[0066] S2: the organic fertilizer, modified biochar, gamma-polyglutamic acid, vermiculite and microbial agent obtained in step S1 are mixed in a mass ratio of 20:30:1:5:1, stirred at 38°C and 600rpm for 1h, granulated, and then dried at 40°C for 1h to obtain a soil conditioner for fish feces.

[0067] The microbial agent is composed of aquatic Rahnella and rosea I-7R in a mass ratio of 1:1.2.

[0068] The method for preparing the modified biochar comprises the following steps:

[0069] N1 Dry and crush the apple peel, pass it through a 40-mesh sieve, and then place it in a 700°C tubular furnace for carbonization for 1.5 hours to obtain biochar; take 10 parts by weight of biochar and add it to 500 parts by weight of N-methylpyrrolidone, and ultrasonicate it at an ultrasonic frequency of 60kHz, an ultrasonic power of 200W, and 40°C for 0.5 hours; then add 15 parts by weight of 30wt% humic acid acetic acid solution, continue ultrasonic treatment for 3 hours, centrifuge, vacuum dry, and grind it through a 100-mesh sieve to obtain preliminary modified biochar;

[0070] N2 Mix 5 parts by weight of the above-mentioned preliminary modified biochar and 3 parts by weight of chitosan, stir at 40°C and 200 rpm for 30 minutes, then add 1 part by weight of glutaraldehyde and continue stirring for 20 minutes, then adjust the pH to 9, let it stand for 1 hour, filter and dry to obtain modified biochar.

[0071] Comparative Example 4

[0072] The method for preparing a soil conditioner based on fish feces comprises the following steps:

[0073] S1: 10 parts by weight of fish excrement and 4 parts by weight of humus soil are mixed and stirred at 600 rpm for 45 minutes, fermentation bacteria with a mass of 1 wt% of fish excrement and 18 parts by weight of water are added, and stirring is continued for 30 minutes. The mixture is fermented at 34°C and 200 rpm for 15 days. During the fermentation process, the material is turned over every 24 hours. After fermentation, the mixture is air-dried to a moisture content of 10% to obtain an organic fertilizer. The fermentation bacteria are composed of Candida parapsilosis, Bacillus subtilis, and Bacillus subtilis in a mass ratio of 2:1:3.

[0074] S2: the organic fertilizer, modified biochar, gamma-polyglutamic acid, vermiculite and microbial agent obtained in step S1 are mixed in a mass ratio of 20:30:1:5:1, stirred at 38°C and 600rpm for 1h, granulated, and then dried at 40°C for 1h to obtain a soil conditioner for fish feces.

[0075] The microbial agent is composed of aquatic Rahnella and rosea I-7R in a mass ratio of 1:1.2.

[0076] The method for preparing the modified biochar comprises the following steps:

[0077] N1 dried and crushed the apple peel, passed it through a 40-mesh sieve, and then carbonized it in a 700℃ tube furnace for 1.5h to obtain biochar;

[0078] N2: 3 parts by weight of chitosan and 120 parts by weight of 2 wt% acetic acid aqueous solution were mixed, stirred at 60°C and 600 rpm for 30 min, 1.5 parts by weight of nicotinic acid acyl-β-D-glucuronic acid and 0.3 parts by weight of an activator were added, wherein the activator was composed of 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide in a ratio of 6:1, and the reaction was continued by stirring for 4 h; dialyzed, and freeze-dried to obtain modified chitosan;

[0079] N3: Mix 5 parts by weight of the above biochar and 3 parts by weight of the above modified chitosan, stir at 40°C and 200 rpm for 30 min, add 1 part by weight of glutaraldehyde and continue stirring for 20 min, adjust the pH to 9, let stand for 1 h, filter and dry to obtain modified biochar.

[0080] Test Example 1

[0081] Water retention performance test: Take 0-25cm soil in the field, the soil bulk density is 1.35g / cm 3, measure its water content, air-dry and pass through a 1mm sieve, add appropriate amount of water and stir evenly to make the water content reach 15%, and put them into plastic pots of equal size, with 1kg of soil in each pot. Weigh the fish feces soil conditioner prepared in Example 1 and Comparative Examples 1-4 respectively, the amount of fish feces soil conditioner added is 0.25 times the mass of the soil, and evenly sprinkle it into the plastic pot and stir evenly, while taking the soil conditioner without adding fish feces as the control (CK). After placing the plastic basin containing the soil conditioner containing fish feces for 12 hours, water was added to the saturated moisture content of the soil. The soil was weighed once every 24 hours using an electronic balance, and the soil water retention rate was calculated according to the following formula. The entire experiment was carried out under light-proof conditions. After fully absorbing water and saturating, it was placed in a ventilated and dry place at 25°C and a relative humidity of 35%. Soil water retention rate = (M1-M) / (M0-M)×100%, where M1 is the mass of soil in the plastic basin after being placed for a period of time (kg), M is the mass of dry soil in the plastic basin (kg), and M0 is the mass of soil in the initial plastic basin after the soil reaches the saturated moisture content (kg). Three parallel samples were taken for each test case. The results are shown in Table 1.

[0082] Table 1 Water retention performance test

[0083] Soil water retention rate after 5 days (%) Example 1 61.4 Comparative Example 1 44.7 Comparative Example 2 51.9 Comparative Example 3 53.1 Comparative Example 4 56.2

[0084] Test Example 2

[0085] Determination of heavy metal content: (1) The soil was subjected to heavy metal pollution. The soil contained 1.31 mg / kg cadmium, 134.6 mg / kg lead and 167.5 mg / kg zinc. The soil was divided into 5 equal areas. According to the soil pH range, the soil was filled with water once to make the soil pH value neutral. The water layer was allowed to dry naturally. The soil conditioner of fish feces of Example 1, Comparative Example 1 and Comparative Example 3-4 of the present invention was added at an amount of 60 kg / mu. Wheat was cultivated. The control group used commercially available biochar-based fertilizer raw materials purchased from Jiangsu Huafeng Agricultural Bioengineering Co., Ltd. Its main purpose was to adsorb heavy metals and adjust pH to improve the soil. The mesh size was 50-60 mesh. The type was biochar.

[0086] (2) Regular irrigation and fertilization: After wheat is planted, irrigate the soil once every month for a total of three times. Control the soil pH to 7 and apply 60 kg / mu of fertilizer.

[0087] (3) Management: Manage and harvest according to conventional management methods.

[0088] Mature wheat was taken and the heavy metal content in the wheat was tested. The results are shown in the following table: The test was performed 4 times and the average value was taken. The test results are shown in Table 2.

[0089] Table 2 Heavy metal content test results

[0090] Cadmium (mg / kg) Lead (mg / kg) Zinc (mg / kg) Example 1 0.01 0 0.14 Comparative Example 1 0.51 0.62 0.83 Comparative Example 3 0.29 0.29 0.54 Comparative Example 4 0.23 0.21 0.31 Control group 0.82 3.38 2.17

[0091] From the above results, it can be seen that the soil conditioner of fish feces prepared by the present invention has good water retention effect and heavy metal passivation effect. Modified chitosan can increase the water absorption and water holding capacity of the soil because its molecular structure contains many hydroxyl and amino hydrophilic groups, which can effectively adsorb and retain water, thereby improving the water retention performance of the soil. Modified chitosan forms a water retention layer in the soil, reducing water evaporation and leakage, which helps to maintain the humidity of the soil, especially under drought conditions, and can significantly improve the drought resistance of crops. Improve soil structure: Modified chitosan is relatively loose, making the soil more loose, which is conducive to the penetration and storage of water. At the same time, a good soil structure also promotes the growth of plant roots and improves water use efficiency. Modified chitosan can also undergo chelation reactions with heavy metal ions (such as lead, cadmium, zinc, etc.) to form stable complexes, thereby fixing heavy metals in the soil and reducing their mobility and bioavailability; by combining with heavy metal ions, modified chitosan can significantly reduce the absorption and accumulation of heavy metals by plants, reduce the risk of heavy metals entering the food chain, reduce plant absorption of heavy metals, and protect crops and the ecological environment.

[0092] Modified biochar is rich in micropores, has a large specific surface area and adsorption performance. When added to the soil, it can not only replenish the organic matter content, water and nutrients in the soil, and improve soil fertility; by adsorbing and slowly releasing nutrients, it increases nutrient utilization efficiency and reduces nutrient loss and waste; it has good water retention properties, can prevent excessive evaporation and loss of water, help plants better absorb water, and promote healthy plant growth; in addition, the addition of humic acid can improve the soil and stimulate crop growth to a certain extent; in addition, the basic structure of humic acid macromolecules is aromatic rings and alicyclic rings, with carboxyl, hydroxyl, carbonyl and other functional groups connected to the rings, which have exchange and adsorption effects with metal ions and can also reduce heavy metals in the soil to a certain extent and promote the growth of crops.

[0093] In summary, the present invention combines modified biochar and modified chitosan for use, and utilizes the porous water absorption characteristics of biochar and the efficient water holding capacity of chitosan to form a complementary water retention system in the soil; the water adsorbed and stored by the biochar is gradually released through the colloid layer of chitosan to provide a continuous water supply. Through the combined action of different adsorption and chelation mechanisms, the coordinated use of the two can more effectively reduce the mobility and bioavailability of heavy metals, which can not only improve the water retention performance of the soil, but also effectively passivate the effects of heavy metals, significantly improve the fixation effect of heavy metals, fix the heavy metals in the soil, and reduce the absorption of crop roots, thereby reducing the entry of heavy metals into the food chain through plants and reducing harm to the human body.

Claims

1. A method for preparing a soil conditioner based on fish feces, characterized in that: The method comprises the following steps: S1 mixing fish excrement and humus soil, adding fermentation bacteria and water, and continuing to stir and ferment to obtain organic fertilizer; S2: the organic fertilizer, modified biochar, gamma-polyglutamic acid, vermiculite and microbial agent obtained in step S1 are mixed and granulated to obtain a soil conditioner for fish feces.

2. The method for preparing a soil conditioner based on fish feces according to claim 1, characterized in that: The fermentation bacteria is at least one of Candida parapsilosis, Bacillus subtilis and Bacillus subtilis.

3. The method for preparing a soil conditioner based on fish feces according to claim 1, characterized in that: The microbial agent is at least one of aquatic Rahnella and rosea I-7R.

4. The method for preparing a soil conditioner based on fish feces according to claim 1, characterized in that: The added amount of the fermentation bacteria is 0.5-4wt% of the mass of fish feces.

5. The method for preparing a soil conditioner based on fish feces according to claim 1, characterized in that: In step S1, the fermentation temperature is 32-38° C. and the fermentation time is 10-30 days.

6. The method for preparing a soil conditioner based on fish feces according to claim 1, characterized in that: The mass ratio of the organic fertilizer, modified biochar, gamma-polyglutamic acid, vermiculite and microbial agent in step S2 is (15-30):(20-40):(0.8-2):(3-8):(0.8-2).

7. The method for preparing a soil conditioner based on fish feces according to claim 1, characterized in that: The method for preparing the modified biochar comprises the following steps: N1: drying, crushing and carbonizing apple peel to obtain biochar; adding the biochar to N-methylpyrrolidone and ultrasonicating it; then adding it to acetic acid solution of humic acid and ultrasonicating it to obtain preliminary modified biochar; N2: chitosan and acetic acid aqueous solution are mixed and stirred, nicotinic acid acyl-β-D-glucuronic acid and an activator are added, and the stirring reaction is continued to obtain modified chitosan; N3: Mix the above-mentioned preliminary modified biochar and the above-mentioned modified chitosan, heat and stir, then add glutaraldehyde and continue stirring to obtain modified biochar.

8. The method for preparing a soil conditioner based on fish feces according to claim 7, characterized in that: The carbonization temperature is 650-900° C., and the carbonization time is 1-5 hours.

9. The method for preparing a soil conditioner based on fish feces according to claim 7, characterized in that: The activator is composed of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in a ratio of 5-8:

1.

10. A soil conditioner based on fish feces, obtained by the preparation method according to any one of claims 1 to 9.