Siliceous shale-based ternary composite soil conditioner and preparation method thereof

Abstract

The application discloses a diatom shale-based ternary composite soil modifier and a preparation method thereof, and relates to the technical field of soil modifiers. According to the dry base weight fraction, the diatom shale-based ternary composite soil modifier is composed of the following components: diatom shale 45-65 parts, biochar 12-20 parts, humic acid 8-15 parts, slow-release compound fertilizer 8-18 parts, compound microbial agent 1-3 parts, chelated trace elements 0.5-2 parts and binder 1-3 parts. The diatom shale is activated by water and heat to release the pore structure, and the microbial agent is directionally loaded to construct a stable microenvironment. The biochar and the humic acid are combined to improve the granule structure, passivate heavy metals and adjust the acid-base balance, so that the degraded soil is repaired from the physical and chemical aspects. The slow-release nutrients are precisely mixed in stages to match the crop fertilizer requirement law, and the components are combined to complete the soil structure remodeling, chemical optimization and microbial reconstruction. The low-temperature drying and extrusion molding are adopted, the product is stable and uniform, the application is convenient, the product is suitable for multiple types of farmland and the nutrient utilization efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of soil conditioner technology, specifically to a diatomaceous earth shale-based ternary composite soil conditioner and its preparation method. Background Technology

[0002] The long-term excessive use of chemical fertilizers in agricultural production has led to increasingly prominent problems such as soil compaction and acidification, a continuous decline in the organic matter content of arable land, and an imbalance in the soil microbial community structure. At the same time, the risk of heavy metal pollution in farmland is constantly increasing, seriously hindering the improvement of arable land quality and the safety of agricultural products. Soil conditioners are a core technical means to remediate degraded soil and improve arable land productivity. Diatomite shale, as a natural aluminosilicate mineral with abundant reserves in my country, possesses a naturally porous structure and good adsorption properties, showing broad application prospects in the field of soil improvement. However, its high-value utilization level is currently low, failing to fully realize its multi-effect improvement potential.

[0003] Existing diatomaceous earth shale-based soil conditioners generally suffer from simple activation processes and insufficient opening of mineral pores, resulting in limited adsorption, water retention, and fertilizer retention capacity, and poor passivation effects on heavy metals in the soil. Most products simply mix biochar and microbial agents without targeted loading technology. The microbial agents are easily deactivated by environmental stresses such as acidity, alkalinity, and temperature in the soil, resulting in short survival periods and hindering the sustained bioremediation effect. Furthermore, the nutrient release rate of existing conditioners does not match the crop's nutrient requirements, has a short slow-release period, and a single nutrient ratio. Micronutrients are mostly in inorganic forms, easily fixed by soil colloids, significantly reducing crop absorption and utilization. In addition, there is a lack of systematic synergistic design among the components; most products focus on single-function improvement and cannot simultaneously achieve the comprehensive goals of soil physical structure repair, chemical property regulation, and biological function reconstruction.

[0004] In summary, existing soil conditioners have significant shortcomings in terms of functional singularity, component synergy, and technological advancement, making it difficult to meet the urgent needs of comprehensive management of degraded soils. Therefore, there is an urgent need to develop a multi-functional soil conditioner that integrates biochar, humic acid, slow-release nutrients, and functional microorganisms, using activated diatomaceous earth as the core carrier. This conditioner should achieve highly efficient synergistic effects of its components through optimized preparation processes, simultaneously addressing multiple issues such as soil physical degradation, nutrient imbalance, and reduced microbial activity, thus providing reliable technical support for the continuous improvement of arable land quality and the sustainable development of green agriculture. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a diatomaceous earth shale-based ternary composite soil conditioner and its preparation method. The conditioner is composed of diatomaceous earth shale, biochar, humic acid, slow-release compound fertilizer, and compound microbial agents in proportion. It is prepared by pretreatment activation, agent loading, multi-component mixing, extrusion granulation, drying and grading. The hydrothermal activation enhances the pore adsorption capacity, the targeted loading of microorganisms constructs a stable microenvironment, and the combination of biochar and humic acid synergistically improves soil aggregate structure and passivates heavy metals. The slow-release nutrients are consistent with the crop's fertilizer requirements, and the components work together to achieve physical, chemical and biological triple remediation of the soil.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: On the one hand, the diatomaceous earth shale-based ternary composite soil conditioner, by weight on a dry basis, is composed of the following components: 45-65 parts diatomaceous earth shale, 12-20 parts biochar, 8-15 parts humic acid, 8-18 parts slow-release compound fertilizer, 1-3 parts compound microbial inoculant, 0.5-2 parts chelated trace elements, and 1-3 parts binder.

[0007] Furthermore, the diatomaceous earth shale has a silica content of not less than 60%, an alumina content of not less than 8%, an iron oxide content of not less than 3%, and a loss on ignition of 5%-12%; particles with a diameter ≤0.15mm account for more than 85% of the total mass, and particles with a diameter of 0.075mm-0.15mm account for more than 60% of the total mass; the porosity is not less than 40%, and the specific surface area is not less than 20m². 2 / g; the main mineral composition includes quartz, feldspar, montmorillonite and illite.

[0008] Furthermore, the biochar is corn stalk-based biochar, prepared by pyrolyzing corn stalks at 500℃-600℃ for 2-3 hours under limited oxygen conditions; the biochar has a pH of 8.0-9.5, a carbon content of 65%-75%, an ash content of 15%-25%, and a specific surface area of ​​150 m². 2 / g-250m 2 / g, total pore volume is 0.15cm³ 3 / g-0.25cm 3 / g; Particles with a diameter of 0.1mm-0.3mm account for more than 90% of the total mass.

[0009] Furthermore, the composite microbial agent is a solid composite microbial agent, composed of Bacillus subtilis, Bacillus mucilaginosa, and Bacillus licheniformis mixed in a mass ratio of 2:1:1; with an effective viable count ≥2.0 × 10⁻⁶. 9 cfu / g, moisture content ≤10%, contamination rate ≤5%, pH value 6.5-7.5.

[0010] Furthermore, the chelated trace elements are EDTA-chelated composite trace elements, composed of EDTA-chelated iron, EDTA-chelated zinc, EDTA-chelated manganese, and EDTA-chelated copper mixed in a mass ratio of 3:2:2:1; the slow-release compound fertilizer is a coated compound fertilizer, composed of coated nitrogen fertilizer, coated phosphate fertilizer, and coated potassium fertilizer, wherein the nitrogen content of the coated nitrogen fertilizer is 42%-46%, the phosphorus content of the coated phosphate fertilizer is 12%-16%, and the potassium content of the coated potassium fertilizer is 50%-55%, with a slow-release period of 60-90 days for each; the binder is sodium carboxymethyl cellulose with a degree of substitution of 0.6-0.8.

[0011] On the other hand, a method for preparing a diatomaceous earth shale-based ternary composite soil conditioner includes the following steps: S1. Diatomaceous shale pretreatment and activation: Diatomaceous shale is pretreated by crushing, grinding and sieving in sequence. After being mixed with an activator, it is subjected to hydrothermal activation reaction. After the reaction, it is washed and dried to obtain activated diatomaceous shale. S2. Targeted loading of microbial agents: The activated diatomaceous earth shale is mixed with a sterile aqueous suspension of composite microbial agents, and the agent is adsorbed and loaded under constant temperature oscillation conditions. After loading, the agent is dried to the preset moisture content. S3. Precise mixing of multiple components: The diatomaceous earth loaded with bacterial agent is mixed evenly with all other components in stages according to the proportion; S4. Material extrusion molding and granulation: The uniformly mixed material is fed into an extrusion granulator to produce granules with a particle size of 2mm-4mm. S5. Drying, cooling and grading finished product: The granulated particles are dried at low temperature, cooled to room temperature and then screened and graded. Particles with qualified particle size are collected to obtain the finished product.

[0012] Furthermore, before the pretreatment, the diatomaceous earth shale is dried at a constant temperature of 105℃ for 24 hours to remove surface adsorbed water. It is then crushed, ground, and sieved using a jaw crusher for coarse crushing, a ball mill for fine grinding, and a 100-mesh standard vibrating screen for grading. The undersize material is taken as the pretreated diatomaceous earth shale. The activator is a 10%-15% sodium hydroxide solution, and the solid-liquid ratio of diatomaceous earth shale to activator is 1g:3mL-1g:5mL. The hydrothermal activation reaction is carried out in a hydrothermal reactor at 120℃-150℃ for 2-4 hours. After the reaction, the product is cooled to room temperature and repeatedly washed with deionized water until the pH of the filtrate is 6.5-7.5. It is then dried at 105℃ for 12 hours to obtain activated diatomaceous earth shale. In step S2, the composite microbial agent is first dispersed in sterile water to prepare a concentration of 1.0×10⁻⁶. 8 cfu / mL -5.0×10 8The bacterial suspension with cfu / mL was mixed with activated diatomaceous earth shale at a solid-liquid ratio of 1g:2mL-1g:4mL. The mixture was then shaken and adsorbed in a constant temperature shaking chamber at 25℃-30℃ and 150r / min-200r / min for 4h-6h. After adsorption, the material was dried at 30℃ with ventilation until the moisture content was 20%-25%.

[0013] Furthermore, before mixing, the biochar is washed with deionized water until the pH of the filtrate is 6.5-7.5, and then dried at 105℃ for 12 hours. The components are mixed in a double-helix conical mixer at a speed of 30-50 r / min for a total mixing time of 15-25 min. The mixing process is divided into three stages: the first stage involves adding diatomaceous earth shale loaded with microbial agents and biochar, mixing for 5-10 min; the second stage involves adding humic acid, slow-release compound fertilizer, and chelated trace elements, mixing for 5-10 min; and the third stage involves adding a binder, mixing for 5 min. The extrusion granulator in S4 is a double-roller extrusion granulator with a die diameter of 2-4 mm and an extrusion pressure of 2-4 MPa.

[0014] Furthermore, the low-temperature drying is carried out in a low-temperature belt dryer at a temperature of 40℃-50℃ for 2-3 hours, resulting in a moisture content of 8%-12% for the dried material. Cooling to room temperature is achieved through natural ventilation for 30-60 minutes. Screening is performed using a double-layer vibrating screen with an upper screen mesh size of 4mm and a lower screen mesh size of 2mm. Particles with a qualified particle size between 2mm and 4mm are collected as the finished product. The material oversize is returned to the extrusion granulator for regranulation, while the material undersize is returned to the double-spiral conical mixer for remixing.

[0015] Furthermore, the diatomaceous earth shale-based ternary composite soil conditioner is characterized by the following specific steps in its preparation method: S1. Diatomaceous shale pretreatment and activation: Diatomaceous shale is pretreated by crushing, grinding and sieving in sequence. After being mixed with an activator, it is subjected to hydrothermal activation reaction. After the reaction, it is washed and dried to obtain activated diatomaceous shale. S2. Targeted loading of microbial agents: The activated diatomaceous earth shale is mixed with a sterile aqueous suspension of composite microbial agents, and the agent is adsorbed and loaded under constant temperature oscillation conditions. After loading, the agent is dried to the preset moisture content. S3. Precise mixing of multiple components: The diatomaceous earth loaded with bacterial agent is mixed evenly with all other components in stages according to the proportion; S4. Low-temperature pre-drying of materials: The uniformly mixed materials are fed into a low-temperature belt dryer for pre-drying at a temperature of 35℃-45℃ for 1.5h-2.5h. The moisture content of the dried materials is controlled at 6%-10%. S5. Ultrafine Grinding and Grading of Finished Products: The pre-dried material is fed into a low-temperature airflow mill for ultrafine grinding. The temperature of the grinding chamber is controlled below 30℃ throughout the process. After grinding, the material is fed into a double-layer vibrating screen for sieving and grading. The upper screen has a mesh size of 0.15mm, and the lower screen has a mesh size of 0.075mm. Powder between 0.075mm and 0.15mm is collected as the finished product. The coarse powder on the screen is returned to the low-temperature airflow mill for re-grinding, and the fine powder on the screen is returned to the double-spiral conical mixer for re-mixing, drying, and grinding again.

[0016] Compared with existing technologies, this diatomaceous earth shale-based ternary composite soil conditioner and its preparation method have the following beneficial effects: I. This invention utilizes a systematic pretreatment and hydrothermal activation process to fully release the internal pore structure of diatomaceous earth shale, significantly enhancing the adsorption capacity and ion exchange capacity of the carrier, thus providing a high-quality mineral matrix for soil improvement. By directionally loading composite microbial agents onto the pore surface of activated diatomaceous earth shale, a stable microenvironment is created for functional microorganisms, effectively resisting soil environmental stress and significantly extending the survival period and duration of action of microorganisms. Simultaneously, the synergistic effect of biochar and humic acid improves soil aggregate structure, regulates soil pH balance, passivates harmful heavy metal ions in the soil, and enhances soil water and fertilizer retention capacity, thus simultaneously restoring the basic properties of degraded soil from both physical and chemical perspectives.

[0017] II. This invention achieves a scientific combination of slow-release nutrients and chelated trace elements through precise, phased mixing of various functional components. This ensures that the nutrient release rhythm closely matches the crop's nutrient requirements throughout its entire growth cycle, effectively reducing nutrient loss and soil fixation, and significantly improving the crop's nutrient absorption and utilization efficiency. The functional components form a synergistic system that promotes mutual benefit, breaking through the limitations of traditional single-function soil conditioners. Simultaneously, it reshapes the soil's physical structure, optimizes its chemical properties, and rebuilds the microbial community. The invention employs low-temperature drying and extrusion molding processes to prepare granular products, ensuring product stability during storage and transportation. The finished product has a uniform particle size and is easy to apply, adapting to the improvement needs of different types of arable land and providing technical support for the long-term improvement of arable land quality.

[0018] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0020] Figure 1 A step-by-step diagram of a diatomaceous earth shale-based ternary composite soil conditioner and its preparation method; Figure 2 Flowchart of the microbial agent directional loading process for a diatomaceous shale-based ternary composite soil conditioner and its preparation method; Figure 3 A flowchart illustrating the entire process of granulation, drying, and grading of a diatomaceous earth shale-based ternary composite soil conditioner and its preparation method. Detailed Implementation

[0021] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0022] Example 1: The diatomaceous earth shale-based ternary composite soil conditioner, by dry basis weight, consists of the following components: 55 parts diatomaceous earth shale, 16 parts biochar, 12 parts humic acid, 13 parts slow-release compound fertilizer, 2 parts compound microbial inoculant, 1.2 parts chelated trace elements, and 2 parts binder.

[0023] The diatomaceous earth shale has a silica content of 65%, an alumina content of 10%, an iron oxide content of 4%, and a loss on ignition of 8%. Particles with a diameter ≤0.15mm account for 90% of the total mass, with particles between 0.075mm and 0.15mm accounting for 65% of the total mass. The porosity is 45%, and the specific surface area is 25m². 2 / g; the main mineral composition includes quartz, feldspar, montmorillonite and illite.

[0024] The biochar is corn stalk-based biochar, prepared by pyrolyzing corn stalks at 550℃ for 2.5 h under limited oxygen conditions; the biochar has a pH of 8.8, a carbon content of 70%, an ash content of 20%, and a specific surface area of ​​200 m². 2 / g, total pore volume is 0.20cm³ 3 / g; particles with a diameter of 0.1mm-0.3mm account for 95% of the total mass.

[0025] The composite microbial agent is a solid composite microbial agent, composed of Bacillus subtilis, Bacillus mucilaginosus, and Bacillus licheniformis mixed in a mass ratio of 2:1:1; the effective viable count is 2.5 × 10⁻⁶. 9 The sample size is cfu / g, moisture content is 8%, contamination rate is 3%, and pH value is 7.0.

[0026] The chelated trace elements are EDTA-chelated composite trace elements, composed of EDTA-chelated iron, EDTA-chelated zinc, EDTA-chelated manganese, and EDTA-chelated copper mixed in a mass ratio of 3:2:2:1; the slow-release compound fertilizer is a coated compound fertilizer, composed of coated nitrogen fertilizer, coated phosphate fertilizer, and coated potassium fertilizer; wherein the nitrogen content of the coated nitrogen fertilizer is 44%, the phosphorus content of the coated phosphate fertilizer is 14%, and the potassium content of the coated potassium fertilizer is 52%, and the slow-release period of all is 75 days; the binder is sodium carboxymethyl cellulose with a degree of substitution of 0.7.

[0027] The preparation method of the above-mentioned diatomaceous earth shale-based ternary composite soil conditioner, such as... Figure 1 As shown, the specific steps are as follows: S1. Diatomaceous Earth Shale Pretreatment and Activation: First, the diatomaceous earth shale was dried at a constant temperature of 105℃ for 24 hours to remove surface adsorbed water. Then, a jaw crusher was used to coarsely crush the dried diatomaceous earth shale, controlling the particle size to below 5mm. The coarsely crushed material was then fed into a ball mill for fine grinding for 30 minutes. After fine grinding, a 100-mesh standard vibrating screen was used for grading, and the undersize material was taken as the pretreated diatomaceous earth shale. The pretreated diatomaceous earth shale was mixed with an activator, which was a 12% sodium hydroxide solution. The solid-liquid ratio of diatomaceous earth shale to activator was 1g:4mL. The mixture was transferred to a hydrothermal reactor for hydrothermal activation at 135℃ for 3 hours. After the reaction, the product was naturally cooled to room temperature and repeatedly washed with deionized water until the pH of the filtrate was 7.0. The washed product was then dried at 105℃ for 12 hours to obtain activated diatomaceous earth shale.

[0028] S2. Targeted loading of microbial agents: The compound microbial agent is dispersed in sterile water to prepare a bacterial suspension with a concentration of 3.0 × 10⁻⁶. 8 The activated diatomaceous earth shale was mixed with the bacterial suspension at a solid-liquid ratio of 1 g:3 mL. The mixture was then transferred to a constant-temperature shaking chamber for adsorption loading at 28°C and a shaking speed of 180 r / min for 5 h. After adsorption, the material was dried at 30°C under low-temperature ventilation until the moisture content was 22%.

[0029] S3. Precise Mixing of Multiple Components: First, wash the biochar with deionized water until the pH of the filtrate is 7.0. Then, dry it at 105℃ for 12 hours. Add the dried biochar and diatomaceous earth loaded with bacterial agent to a double-helix conical mixer. The mixer speed is 40 r / min and the mixing time is 8 min. Then, add humic acid, slow-release compound fertilizer and chelated trace elements to the mixer and continue mixing for 8 min. Finally, add the binder to the mixer and mix for another 5 min to ensure that all components are mixed evenly.

[0030] S4. Material extrusion molding and granulation: The uniformly mixed material is fed into a double-roller extrusion granulator with a die diameter of 3mm and an extrusion pressure of 3MPa. Through the extrusion action of the double rollers, the material is made into granules with a particle size of 2mm-4mm.

[0031] S5. Drying, Cooling, and Grading of Finished Product: The granulated particles are sent to a low-temperature belt dryer for drying at 45℃ for 2.5 hours, resulting in a moisture content of 10%. The dried particles are then cooled to room temperature using natural ventilation for 45 minutes. After cooling, a double-layer vibrating screen is used for sieving and grading. The upper screen has a mesh size of 4mm, and the lower screen has a mesh size of 2mm. Particles between 2mm and 4mm are collected as the finished product. The material that passes through the screen is returned to the extrusion granulator for regranulation, while the material that passes through the screen is returned to the double-spiral conical mixer for remixing.

[0032] Example 2: The diatomaceous earth shale-based ternary composite soil conditioner, by dry basis weight, consists of the following components: 45 parts diatomaceous earth shale, 12 parts biochar, 8 parts humic acid, 8 parts slow-release compound fertilizer, 1 part compound microbial agent, 0.5 parts chelated trace elements, and 1 part binder.

[0033] The diatomaceous earth shale has a silica content of 60%, an alumina content of 8%, an iron oxide content of 3%, and a loss on ignition of 5%. Particles with a diameter ≤0.15mm account for 85% of the total mass, with particles between 0.075mm and 0.15mm accounting for 60% of the total mass. The porosity is 40%, and the specific surface area is 20m². 2 / g; the main mineral composition includes quartz, feldspar, montmorillonite and illite.

[0034] The biochar is corn stalk-based biochar, prepared by pyrolysis of corn stalks at 500℃ for 2 hours under limited oxygen conditions; the biochar has a pH of 8.0, a carbon content of 65%, an ash content of 15%, and a specific surface area of ​​150 m². 2 / g, total pore volume is 0.15cm³ 3 / g; particles with a diameter of 0.1mm-0.3mm account for 90% of the total mass.

[0035] The composite microbial agent is a solid composite microbial agent, composed of Bacillus subtilis, Bacillus mucilaginosus, and Bacillus licheniformis mixed in a mass ratio of 2:1:1; the effective viable count is 2.0 × 10⁻⁶. 9 The sample size is cfu / g, moisture content is 10%, contamination rate is 5%, and pH value is 6.5.

[0036] The chelated trace elements are EDTA-chelated composite trace elements, composed of EDTA-chelated iron, EDTA-chelated zinc, EDTA-chelated manganese, and EDTA-chelated copper mixed in a mass ratio of 3:2:2:1; the slow-release compound fertilizer is a coated compound fertilizer, composed of coated nitrogen fertilizer, coated phosphate fertilizer, and coated potassium fertilizer; wherein the nitrogen content of the coated nitrogen fertilizer is 42%, the phosphorus content of the coated phosphate fertilizer is 12%, and the potassium content of the coated potassium fertilizer is 50%, and the slow-release period of all is 60 days; the binder is sodium carboxymethyl cellulose with a degree of substitution of 0.6.

[0037] The preparation method of the above-mentioned diatomaceous earth shale-based ternary composite soil conditioner includes the following specific steps: S1. Diatomaceous Earth Shale Pretreatment and Activation: First, the diatomaceous earth shale was dried at a constant temperature of 105℃ for 24 hours to remove surface adsorbed water. Then, a jaw crusher was used to coarsely crush the dried diatomaceous earth shale, controlling the particle size to below 5mm. The coarsely crushed material was then fed into a ball mill for fine grinding for 25 minutes. After fine grinding, a 100-mesh standard vibrating screen was used for grading, and the undersize material was taken as the pretreated diatomaceous earth shale. The pretreated diatomaceous earth shale was mixed with an activator, which was a 10% sodium hydroxide solution. The solid-liquid ratio of diatomaceous earth shale to activator was 1g:3mL. The mixture was transferred to a hydrothermal reactor for hydrothermal activation at 120℃ for 2 hours. After the reaction, the product was naturally cooled to room temperature and repeatedly washed with deionized water until the pH of the filtrate was 6.5. The washed product was then dried at 105℃ for 12 hours to obtain activated diatomaceous earth shale.

[0038] S2. Targeted loading of microbial agents: The compound microbial agent is dispersed in sterile water to prepare a bacterial suspension with a concentration of 1.0 × 10⁻⁶. 8 CFU / mL; The activated diatomaceous earth shale was mixed with the bacterial suspension at a solid-liquid ratio of 1 g: 2 mL. The mixture was transferred to a constant-temperature shaking chamber for adsorption loading at 25°C and a shaking speed of 150 r / min for 4 h. After adsorption, the material was dried at 30°C under low-temperature ventilation until the moisture content was 20%. Figure 2 As shown.

[0039] S3. Precise Mixing of Multiple Components: First, wash the biochar with deionized water until the pH of the filtrate is 6.5, then dry it at 105℃ for 12 hours. Add the dried biochar and diatomaceous earth loaded with microbial agents to a double-helix conical mixer at a speed of 30 r / min for 5 minutes. Then, add humic acid, slow-release compound fertilizer and chelated trace elements to the mixer and continue mixing for 5 minutes. Finally, add the binder to the mixer and mix for another 5 minutes to ensure that all components are mixed evenly.

[0040] S4. Material extrusion molding and granulation: The uniformly mixed material is fed into a double-roller extrusion granulator with a die diameter of 2mm and an extrusion pressure of 2MPa. Through the extrusion action of the double rollers, the material is made into granules with a particle size of 2mm-4mm.

[0041] S5. Drying, Cooling, and Grading of Finished Product: The granulated particles are sent to a low-temperature belt dryer for drying at 40℃ for 2 hours, resulting in a moisture content of 8%. The dried particles are then cooled to room temperature using natural ventilation for 30 minutes. After cooling, a double-layer vibrating screen is used for sieving and grading. The upper screen has a mesh size of 4mm, and the lower screen has a mesh size of 2mm. Particles between 2mm and 4mm are collected as the finished product. The material that passes through the screen is returned to the extrusion granulator for regranulation, while the material that passes through the screen is returned to the double-spiral conical mixer for remixing.

[0042] Example 3: The diatomaceous earth shale-based ternary composite soil conditioner, by dry basis weight, consists of the following components: 65 parts diatomaceous earth shale, 20 parts biochar, 15 parts humic acid, 18 parts slow-release compound fertilizer, 3 parts compound microbial inoculant, 2 parts chelated trace elements, and 3 parts binder.

[0043] The diatomaceous earth shale has a silica content of 70%, an alumina content of 12%, an iron oxide content of 5%, and a loss on ignition of 12%. Particles with a diameter ≤0.15mm account for 95% of the total mass, with particles between 0.075mm and 0.15mm accounting for 70% of the total mass. The porosity is 50%, and the specific surface area is 30m². 2 / g; the main mineral composition includes quartz, feldspar, montmorillonite and illite.

[0044] The biochar is corn stalk-based biochar, prepared by pyrolysis of corn stalks at 600℃ for 3 hours under limited oxygen conditions; the biochar has a pH of 9.5, a carbon content of 75%, an ash content of 25%, and a specific surface area of ​​250 m². 2 / g, total pore volume is 0.25cm³ 3 / g; particles with a diameter of 0.1mm-0.3mm account for 98% of the total mass.

[0045] The composite microbial agent is a solid composite microbial agent, composed of Bacillus subtilis, Bacillus mucilaginosus, and Bacillus licheniformis mixed in a mass ratio of 2:1:1; the effective viable count is 3.0 × 10⁻⁶. 9 The sample size is cfu / g, moisture content is 6%, contamination rate is 2%, and pH value is 7.5.

[0046] The chelated trace elements are EDTA-chelated composite trace elements, composed of EDTA-chelated iron, EDTA-chelated zinc, EDTA-chelated manganese, and EDTA-chelated copper mixed in a mass ratio of 3:2:2:1; the slow-release compound fertilizer is a coated compound fertilizer, composed of coated nitrogen fertilizer, coated phosphate fertilizer, and coated potassium fertilizer; wherein the nitrogen content of the coated nitrogen fertilizer is 46%, the phosphorus content of the coated phosphate fertilizer is 16%, and the potassium content of the coated potassium fertilizer is 55%, and the slow-release period of all is 90 days; the binder is sodium carboxymethyl cellulose with a degree of substitution of 0.8.

[0047] The preparation method of the above-mentioned diatomaceous earth shale-based ternary composite soil conditioner includes the following specific steps: S1. Diatomaceous Earth Shale Pretreatment and Activation: First, the diatomaceous earth shale was dried at a constant temperature of 105℃ for 24 hours to remove surface adsorbed water. Then, a jaw crusher was used to coarsely crush the dried diatomaceous earth shale, controlling the particle size to below 5mm. The coarsely crushed material was then fed into a ball mill for fine grinding for 35 minutes. After fine grinding, a 100-mesh standard vibrating screen was used for grading, and the undersize material was taken as the pretreated diatomaceous earth shale. The pretreated diatomaceous earth shale was mixed with an activator, which was a 15% sodium hydroxide solution. The solid-liquid ratio of diatomaceous earth shale to activator was 1g:5mL. The mixture was transferred to a hydrothermal reactor for hydrothermal activation at 150℃ for 4 hours. After the reaction, the product was naturally cooled to room temperature and repeatedly washed with deionized water until the pH of the filtrate was 7.5. The washed product was then dried at 105℃ for 12 hours to obtain activated diatomaceous earth shale.

[0048] S2. Targeted loading of microbial agents: The compound microbial agent is dispersed in sterile water to prepare a bacterial suspension with a concentration of 5.0 × 10⁻⁶. 8 The activated diatomaceous earth shale was mixed with the bacterial suspension at a solid-liquid ratio of 1 g:4 mL. The mixture was then transferred to a constant-temperature shaking chamber for adsorption loading at 30°C and a shaking speed of 200 r / min for 6 h. After adsorption, the material was dried at 30°C under low-temperature ventilation until the moisture content was 25%.

[0049] S3. Precise Mixing of Multiple Components: First, wash the biochar with deionized water until the pH of the filtrate is 7.5. Then, dry it at 105℃ for 12 hours. Add the dried biochar and diatomaceous earth loaded with microbial agents to a double-helix conical mixer. The mixer speed is 50 r / min and the mixing time is 10 min. Then, add humic acid, slow-release compound fertilizer and chelated trace elements to the mixer and continue mixing for 10 min. Finally, add the binder to the mixer and mix for another 5 min to ensure that all components are mixed evenly.

[0050] S4. Material extrusion molding and granulation: The uniformly mixed material is fed into a double-roller extrusion granulator with a die diameter of 4mm and an extrusion pressure of 4MPa. Through the extrusion action of the double rollers, the material is made into granules with a particle size of 2mm-4mm.

[0051] S5. Drying, Cooling, and Grading of Finished Product: The granulated particles are fed into a low-temperature belt dryer for drying at 50℃ for 3 hours, resulting in a moisture content of 12%. The dried particles are then cooled to room temperature via natural ventilation for 60 minutes. After cooling, a double-layer vibrating screen is used for grading, with the upper screen having a 4mm mesh size and the lower screen having a 2mm mesh size. Particles between 2mm and 4mm are collected as the finished product; the oversize material is returned to the extrusion granulator for regranulation, and the undersize material is returned to the double-spiral conical mixer for remixing. Figure 3 As shown.

[0052] Comparative example: A soil conditioner, by dry basis weight, is composed of the following components: 55 parts ordinary diatomaceous earth, 16 parts biochar, 12 parts humic acid, 13 parts slow-release compound fertilizer, 2 parts compound microbial inoculant, 1.2 parts chelated trace elements, and 2 parts binder.

[0053] The ordinary diatomaceous earth has a silica content of 85%, an alumina content of 3%, an iron oxide content of 1%, and a loss on ignition of 3%; particles with a diameter ≤0.15mm account for 90% of the total mass; the porosity is 35%, and the specific surface area is 18m². 2 / g; the main mineral composition is quartz.

[0054] The biochar is corn stalk-based biochar, prepared by pyrolyzing corn stalks at 550℃ for 2.5 h under limited oxygen conditions; the biochar has a pH of 8.8, a carbon content of 70%, an ash content of 20%, and a specific surface area of ​​200 m². 2 / g, total pore volume is 0.20cm³ 3 / g; particles with a diameter of 0.1mm-0.3mm account for 95% of the total mass.

[0055] The composite microbial agent is a solid composite microbial agent, composed of Bacillus subtilis, Bacillus mucilaginosus, and Bacillus licheniformis mixed in a mass ratio of 2:1:1; the effective viable count is 2.5 × 10⁻⁶. 9 The sample size is cfu / g, moisture content is 8%, contamination rate is 3%, and pH value is 7.0.

[0056] The chelated trace elements are EDTA-chelated composite trace elements, composed of EDTA-chelated iron, EDTA-chelated zinc, EDTA-chelated manganese, and EDTA-chelated copper mixed in a mass ratio of 3:2:2:1; the slow-release compound fertilizer is a coated compound fertilizer, composed of coated nitrogen fertilizer, coated phosphate fertilizer, and coated potassium fertilizer; wherein the nitrogen content of the coated nitrogen fertilizer is 44%, the phosphorus content of the coated phosphate fertilizer is 14%, and the potassium content of the coated potassium fertilizer is 52%, and the slow-release period of all is 75 days; the binder is sodium carboxymethyl cellulose with a degree of substitution of 0.7.

[0057] The specific steps for preparing the above-mentioned soil conditioner are as follows: S1. Pretreatment of Ordinary Diatomaceous Earth: Ordinary diatomaceous earth is first dried at a constant temperature of 105℃ for 24 hours to remove surface adsorbed water. Then, a jaw crusher is used to coarsely crush the dried diatomaceous earth, controlling the particle size to below 5mm. The coarsely crushed material is then fed into a ball mill for fine grinding for 30 minutes. After fine grinding, a 100-mesh standard vibrating screen is used for grading, and the material passing through the screen is taken as the pretreated ordinary diatomaceous earth. No hydrothermal activation reaction is performed in this step; the pretreated ordinary diatomaceous earth is directly used in subsequent steps.

[0058] S2. Targeted loading of microbial agents: The compound microbial agent is dispersed in sterile water to prepare a bacterial suspension with a concentration of 3.0 × 10⁻⁶. 8 cfu / mL; mix the pretreated ordinary diatomaceous earth with the bacterial suspension, with a solid-liquid ratio of 1g:3mL; transfer the mixture to a constant temperature shaking chamber for adsorption loading at a temperature of 28℃, a shaking speed of 180r / min, and an adsorption time of 5h. After adsorption, dry the material at a low temperature and ventilation at 30℃ until the moisture content of the material is 22%.

[0059] S3. Precise Mixing of Multiple Components: First, wash the biochar with deionized water until the pH of the filtrate is 7.0. Then, dry it at 105℃ for 12 hours. Add the dried biochar and ordinary diatomaceous earth loaded with bacterial agent into a double helix conical mixer. The mixer speed is 40 r / min and the mixing time is 8 min. Then, add humic acid, slow-release compound fertilizer and chelated trace elements to the mixer and continue mixing for 8 min. Finally, add the binder to the mixer and mix for another 5 min to ensure that all components are mixed evenly.

[0060] S4. Material extrusion molding and granulation: The uniformly mixed material is fed into a double-roller extrusion granulator with a die diameter of 3mm and an extrusion pressure of 3MPa. Through the extrusion action of the double rollers, the material is made into granules with a particle size of 2mm-4mm.

[0061] S5. Drying, Cooling, and Grading of Finished Product: The granulated particles are sent to a low-temperature belt dryer for drying at 45℃ for 2.5 hours, resulting in a moisture content of 10%. The dried particles are then cooled to room temperature using natural ventilation for 45 minutes. After cooling, the particles are sieved and graded using a double-layer vibrating screen with a 4mm mesh size on the upper screen and a 2mm mesh size on the lower screen. Particles between 2mm and 4mm in size are collected as the finished product. The material that passes through the screen is returned to the extrusion granulator for regranulation, while the material that passes through the screen is returned to the double-spiral conical mixer for remixing.

[0062] To more clearly compare the core differences and corresponding performance of each embodiment with the comparative example, the main parameters and performance test results are summarized in the table below:

[0063] As can be seen from the above embodiments and comparative examples, the diatomaceous earth shale-based ternary composite soil conditioner provided by the present invention can effectively improve soil physical structure, increase soil porosity, reduce soil bulk density, and increase soil organic matter content, while ensuring the survival and activity of microbial agents, ultimately leading to increased crop yield. Examples one to three all achieved stable improvement effects, proving the feasibility and universality of the technical solution of the present invention. Compared with the comparative examples, the soil conditioner of the present invention has significant advantages in all performance indicators, indicating that the activation treatment of diatomaceous earth shale and the component ratio have a key impact on the soil improvement effect.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A diatomaceous earth shale-based ternary composite soil conditioner, characterized in that, Based on dry basis weight, it consists of the following components: 45-65 parts diatomaceous earth shale, 12-20 parts biochar, 8-15 parts humic acid, 8-18 parts slow-release compound fertilizer, 1-3 parts compound microbial inoculant, 0.5-2 parts chelated trace elements, and 1-3 parts binder.

2. The diatomaceous earth shale-based ternary composite soil conditioner according to claim 1, characterized in that, The diatomaceous earth shale has a silica content of not less than 60%, an alumina content of not less than 8%, an iron oxide content of not less than 3%, and a loss on ignition of 5%-12%; particles with a diameter ≤0.15mm account for more than 85% of the total mass, and particles with a diameter of 0.075mm-0.15mm account for more than 60% of the total mass; the porosity is not less than 40%, and the specific surface area is not less than 20m². 2 / g; the main mineral composition includes quartz, feldspar, montmorillonite and illite.

3. The diatomaceous earth shale-based ternary composite soil conditioner according to claim 1, characterized in that, The biochar is corn stalk-based biochar, prepared by pyrolyzing corn stalks at 500℃-600℃ for 2-3 hours under limited oxygen conditions; the biochar has a pH of 8.0-9.5, a carbon content of 65%-75%, an ash content of 15%-25%, and a specific surface area of ​​150 m². 2 / g-250m 2 / g, total pore volume is 0.15cm³ 3 / g-0.25cm 3 / g; Particles with a diameter of 0.1mm-0.3mm account for more than 90% of the total mass.

4. The diatomaceous earth shale-based ternary composite soil conditioner according to claim 1, characterized in that, The composite microbial agent is a solid composite microbial agent, composed of Bacillus subtilis, Bacillus mucilaginosus, and Bacillus licheniformis mixed in a mass ratio of 2:1:1; the effective viable count is ≥2.0×10⁻⁶. 9 cfu / g, moisture content ≤10%, contamination rate ≤5%, pH value 6.5-7.

5.

5. The diatomaceous earth shale-based ternary composite soil conditioner according to claim 1, characterized in that, The chelated trace elements are EDTA-chelated composite trace elements, composed of EDTA-chelated iron, EDTA-chelated zinc, EDTA-chelated manganese, and EDTA-chelated copper mixed in a mass ratio of 3:2:2:1; the slow-release compound fertilizer is a coated compound fertilizer, composed of coated nitrogen fertilizer, coated phosphate fertilizer, and coated potassium fertilizer, wherein the nitrogen content of the coated nitrogen fertilizer is 42%-46%, the phosphorus content of the coated phosphate fertilizer is 12%-16%, and the potassium content of the coated potassium fertilizer is 50%-55%, and the slow-release period is 60-90 days for all of them; the binder is sodium carboxymethyl cellulose with a degree of substitution of 0.6-0.

8.

6. A method for preparing a diatomaceous earth shale-based ternary composite soil conditioner, wherein the method is used to prepare the diatomaceous earth shale-based ternary composite soil conditioner according to any one of claims 1-5, and the method is used to prepare a granular soil conditioner, characterized in that... The specific steps of this preparation method are as follows: S1. Diatomaceous shale pretreatment and activation: Diatomaceous shale is pretreated by crushing, grinding and sieving in sequence. After being mixed with an activator, it is subjected to hydrothermal activation reaction. After the reaction, it is washed and dried to obtain activated diatomaceous shale. S2. Targeted loading of microbial agents: The activated diatomaceous earth shale is mixed with a sterile aqueous suspension of composite microbial agents, and the agent is adsorbed and loaded under constant temperature oscillation conditions. After loading, the agent is dried to the preset moisture content. S3. Precise mixing of multiple components: The diatomaceous earth loaded with bacterial agent is mixed evenly with all other components in stages according to the proportion; S4. Material extrusion molding and granulation: The uniformly mixed material is fed into an extrusion granulator to produce granules with a particle size of 2mm-4mm. S5. Drying, cooling and grading finished product: The granulated particles are dried at low temperature, cooled to room temperature and then screened and graded. Particles with qualified particle size are collected to obtain the finished product.

7. The preparation method of the diatomaceous earth shale-based ternary composite soil conditioner according to claim 6, characterized in that, In step S1, before pretreatment, the diatomaceous earth shale is dried at 105℃ for 24 hours to remove surface adsorbed water. It is then crushed, ground, and sieved using a jaw crusher for coarse crushing, a ball mill for fine grinding, and a 100-mesh standard vibrating screen for grading. The undersize material is taken as the pretreated diatomaceous earth shale. The activator is a 10%-15% sodium hydroxide solution. The solid-liquid ratio of diatomaceous earth shale to activator is 1g:3mL-1g:5mL. The hydrothermal activation reaction is carried out in a hydrothermal reactor at 120℃-150℃ for 2-4 hours. After the reaction, the product is cooled to room temperature and repeatedly washed with deionized water until the pH of the filtrate is 6.5-7.

5. It is then dried at 105℃ for 12 hours to obtain activated diatomaceous earth shale. In step S2, the composite microbial agent is first dispersed in sterile water to prepare a concentration of 1.0×10⁻⁶. 8 cfu / mL -5.0×10 8 The bacterial suspension with cfu / mL was mixed with activated diatomaceous earth shale at a solid-liquid ratio of 1g:2mL-1g:4mL. The mixture was then shaken and adsorbed in a constant temperature shaking chamber at 25℃-30℃ and 150r / min-200r / min for 4h-6h. After adsorption, the material was dried at 30℃ with ventilation until the moisture content was 20%-25%.

8. The preparation method of the diatomaceous earth shale-based ternary composite soil conditioner according to claim 6, characterized in that, In step S3, the biochar is washed with deionized water until the pH of the filtrate is 6.5-7.5 before mixing, and then dried at 105℃ for 12 hours. The components are mixed in a double-helix conical mixer at a speed of 30-50 r / min for a total mixing time of 15-25 min. The mixing process is divided into three stages: the first stage involves adding diatomaceous earth shale loaded with microbial agents and biochar, mixing for 5-10 min; the second stage involves adding humic acid, slow-release compound fertilizer, and chelated trace elements, mixing for 5-10 min; and the third stage involves adding a binder and mixing for 5 min. In step S4, the extrusion granulator is a double-roller extrusion granulator with a die diameter of 2-4 mm and an extrusion pressure of 2-4 MPa.

9. The preparation method of the diatomaceous earth shale-based ternary composite soil conditioner according to claim 6, characterized in that, In step S5, the low-temperature drying is carried out in a low-temperature belt dryer at a temperature of 40℃-50℃ for 2-3 hours, resulting in a moisture content of 8%-12% in the dried material. Cooling to room temperature is achieved using natural ventilation for 30-60 minutes. Screening is performed using a double-layer vibrating screen with an upper screen mesh size of 4mm and a lower screen mesh size of 2mm. Particles with a qualified particle size between 2mm and 4mm are collected as the finished product. The material oversizes is returned to the extrusion granulator for regranulation, while the material undersizes is returned to the double-spiral conical mixer for remixing.

10. A method for preparing a diatomaceous earth shale-based ternary composite soil conditioner, wherein the method is used to prepare the diatomaceous earth shale-based ternary composite soil conditioner according to any one of claims 1-5, characterized in that, This preparation method is used to prepare powder-type soil conditioners. The specific steps are as follows: S1. Diatomaceous shale pretreatment and activation: Diatomaceous shale is pretreated by crushing, grinding and sieving in sequence. After being mixed with an activator, it is subjected to hydrothermal activation reaction. After the reaction, it is washed and dried to obtain activated diatomaceous shale. S2. Targeted loading of microbial agents: The activated diatomaceous earth shale is mixed with a sterile aqueous suspension of composite microbial agents, and the agent is adsorbed and loaded under constant temperature oscillation conditions. After loading, the agent is dried to the preset moisture content. S3. Precise mixing of multiple components: The diatomaceous earth loaded with bacterial agent is mixed evenly with all other components in stages according to the proportion; S4. Low-temperature pre-drying of materials: The uniformly mixed materials are fed into a low-temperature belt dryer for pre-drying. The drying temperature is 35℃-45℃, the drying time is 1.5h-2.5h, and the moisture content of the dried materials is controlled at 6%-10%. S5. Ultrafine Grinding and Grading of Finished Products: The pre-dried material is fed into a low-temperature airflow mill for ultrafine grinding. The temperature of the grinding chamber is controlled below 30℃ throughout the process. After grinding, the material is fed into a double-layer vibrating screen for sieving and grading. The upper screen has a mesh size of 0.15mm, and the lower screen has a mesh size of 0.075mm. Powder between 0.075mm and 0.15mm is collected as the finished product. The coarse powder on the screen is returned to the low-temperature airflow mill for re-grinding, and the fine powder on the screen is returned to the double-spiral conical mixer for re-mixing, drying, and grinding again.

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