Acid-resistant quality-improving composite soil conditioner as well as preparation method and application thereof

Abstract

The invention provides an acid-resistant quality-improving composite soil conditioner as well as a preparation method and application thereof, and relates to the technical field of soil improvement. The composite soil conditioner comprises the following components in percentage by mass: 40-50% of phosphorus-rich biochar, 40-50% of a mixed inorganic mineral material, 1-2% of a composite microbial agent and 8-18% of an organic binder. According to the invention, CaCl2 and KH2PO4 are utilized to modify the biochar, so that functional groups on the surface of the biochar can be improved, and the biochar has good fertilizer release potential. The mixed inorganic mineral material can quickly supplement calcium, magnesium and silicon elements in the soil, and surface active sites of the mixed inorganic mineral material can promote formation of aggregates and improve the physical structure of the soil. The compound microbial agent can simultaneously meet various functions of dissolving phosphorus, dissolving potassium, promoting growth, antagonizing and the like. Through the organic-inorganic-microorganism synergistic effect, the multiple effects of reducing the soil acidity, increasing the soil fertility, improving the soil structure and increasing the crop yield are achieved.

Description

Technical Field

[0001] This invention relates to the field of soil improvement technology, and in particular to an acid-resistant and soil-improving composite soil conditioner, its preparation method, and its application. Background Technology

[0002] Acidic soils have become a significant limiting factor for sustainable agricultural development. Soil acidification leads to the large-scale dissolution of aluminum ions, a sharp decline in soil nutrient availability, especially deficiencies in phosphorus, calcium, magnesium, and molybdenum, and damage to the structure and function of the microbial community, which in turn inhibits plant root development and ultimately affects crop yield and agricultural product safety.

[0003] Adding soil conditioners is a core technology for improving acidic soils. Common types of conditioners include inorganic, organic, and composite types. Inorganic materials, such as lime, can rapidly increase soil pH, but excessive application can lead to compaction, calcium and magnesium ion imbalance, and lacks nutrient activation function. Organic conditioners, such as biochar, can effectively increase organic matter and improve soil structure, but are easily affected by raw materials and pyrolysis temperature, and have limited effectiveness in improving acidic soils with pH < 5.5. Due to the limitations of single-material improvement, organic-inorganic composite conditioners have become a current research hotspot. However, the synergistic effect between components in traditional composite conditioners is not high, and their effects on reducing soil acidity and improving soil quality still need improvement. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide an acid-resistant and soil-improving composite soil conditioner, its preparation method, and its application. The acid-resistant and soil-improving composite soil conditioner provided by this invention is used for the improvement of acidic soils, and has excellent effects in reducing acidity, improving soil quality, and promoting growth and increasing yield.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides an acid-resistant and soil-improving composite soil conditioner, comprising the following components by weight percentage: Phosphorus-rich biochar 40-50%, mixed inorganic mineral materials 40-50%, composite microbial agent 1-2%, organic binder 8-18%; The mixed inorganic mineral material includes kaolin, zeolite and fly ash, and the mass ratio of kaolin, zeolite and fly ash is 1:1:3. The composite microbial agent includes Bacillus subtilis, Bacillus licheniformis, and Bacillus subtilis, with the ratio of effective viable counts of the Bacillus subtilis, Bacillus licheniformis, and Bacillus subtilis being (1.5~2):(0.8~1):(0.8~1); the effective viable count of the composite microbial agent is ≥50×10⁻⁶. 8 CFU / g; The preparation method of the phosphorus-rich biochar includes the following steps: The aqueous suspension of biochar was mixed with CaCl2 and KH2PO4 and stirred for the first time. The pH of the resulting mixture was adjusted to 10 and stirred for the second time. The mixture was then subjected to aging, solid-liquid separation and solid-phase drying to obtain the phosphorus-rich biochar. The mass ratio of biochar, CaCl2 and KH2PO4 was 2:1:1.

[0006] Preferably, the first stirring time is 30 minutes, the second stirring time is 2 hours, and the aging time is 24 hours; the pH value is adjusted using KOH solution.

[0007] Preferably, the mixed inorganic mineral material contains ≥20% CaO and ≥6% MgO by mass, and the particle size of the mixed inorganic mineral material is ≤0.25mm.

[0008] Preferably, the Bacillus subtilis has the accession number CGMCC No. 33913, the Bacillus licheniformis has the accession number CGMCC No. 33912, and the Bacillus subtilis has the accession number CGMCC No. 33911.

[0009] Preferably, the preparation method of the compound microbial agent includes the following steps: Bacillus subtilis, Bacillus licheniformis, and Bacillus subtilis were inoculated into liquid culture medium and fermented to obtain fermentation broth. The three fermentation broths were centrifuged to obtain concentrated bacterial solutions. The three concentrated bacterial solutions were mixed and freeze-dried to obtain the composite microbial agent.

[0010] Preferably, the organic binder comprises bentonite, sodium humate, and potassium humate, wherein the mass ratio of bentonite, sodium humate, and potassium humate is 3:1:1.

[0011] Preferably, the acid-resistant and soil-improving composite soil conditioner has the following characteristics: pH value 8.5-10; organic matter content ≥20wt%; total nutrients ≥2wt%, calculated as N+P2O5+K2O; calcium content ≥10wt%, calculated as CaO; magnesium content ≥3wt%, calculated as MgO; and effective viable bacteria count ≥0.5×10⁻⁶. 8 CFU / g.

[0012] This invention provides a method for preparing the acid-resistant and soil-improving composite soil conditioner described in the above technical solution, comprising the following steps: The phosphorus-rich biochar, mixed inorganic mineral materials, composite microbial agents, and organic binders are mixed to obtain the acid-resistant and soil-improving composite soil conditioner.

[0013] Preferably, after mixing, the resulting composite material is further granulated, and the granulated particle size is 2~4mm.

[0014] This invention provides the application of the acid-resistant and soil-improving composite soil conditioner described in the above technical solutions or the acid-resistant and soil-improving composite soil conditioner prepared by the above technical solutions in the improvement of acidified soil.

[0015] This invention provides an acid-resistant and soil-improving composite soil conditioner, comprising the following components by weight percentage: 40-50% phosphorus-rich biochar, 40-50% mixed inorganic mineral materials, 1-2% composite microbial inoculant, and 8-18% organic binder. This invention utilizes CaCl2 and KH2PO4 to modify the biochar, improving its surface functional groups and increasing its ash content, alkalinity, and pH value. Compared to untreated biochar, it is more effective at buffering soil acidity. Furthermore, the combination of phosphate and biochar allows for the continuous delivery of phosphate to the soil, exhibiting excellent fertilizer release potential and a stronger heavy metal fixation capacity than pure biochar. The mixed inorganic mineral material, composed of kaolin, zeolite, and fly ash, can rapidly replenish calcium, magnesium, and silicon elements in the soil. The abundant surface active sites of the inorganic minerals can also promote the formation of aggregates, improve soil physical structure, and the mixed inorganic mineral material can also absorb a large amount of industrial by-products. The compound microbial agent composed of Bacillus subtilis, Bacillus licheniformis, and Bacillus subtilis can simultaneously fulfill multiple functions such as phosphorus solubilization, potassium solubilization, growth promotion, and antagonism. The soil conditioner provided by this invention achieves synergistic effects of multiple components, effectively reducing soil acidity, increasing soil fertility, improving soil structure, and increasing crop yield.

[0016] Biological Preservation Instructions gelatinous spore-forming bacteria ( Mucilaginous Paenibacillus The strain number NAAS-ECO-Bm-003 was deposited on March 20, 2025, at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 33913.

[0017] Bacillus licheniformis ( Bacillus licheniformis The strain number NAAS-ECO-Bl-002 was deposited on March 20, 2025, at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 33912.

[0018] Bacillus subtilis ( Bacillus subtilisThe strain number NAAS-ECO-Bs-001 was deposited on March 20, 2025, at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 33911. Detailed Implementation

[0019] This invention provides an acid-resistant and soil-improving composite soil conditioner, comprising the following components by weight percentage: Phosphorus-rich biochar 40-50%, mixed inorganic mineral materials 40-50%, composite microbial agent 1-2%, organic binder 8-18%; The mixed inorganic mineral material includes kaolin, zeolite and fly ash, and the mass ratio of kaolin, zeolite and fly ash is 1:1:3. The composite microbial agent includes Bacillus subtilis, Bacillus licheniformis, and Bacillus subtilis, with the ratio of effective viable counts of the Bacillus subtilis, Bacillus licheniformis, and Bacillus subtilis being (1.5~2):(0.8~1):(0.8~1); the effective viable count of the composite microbial agent is ≥50×10⁻⁶. 8 CFU / g; The preparation method of the phosphorus-rich biochar includes the following steps: The aqueous suspension of biochar was mixed with CaCl2 and KH2PO4 and stirred for the first time. The pH of the resulting mixture was adjusted to 10 and stirred for the second time. The mixture was then subjected to aging, solid-liquid separation and solid-phase drying to obtain the phosphorus-rich biochar. The mass ratio of biochar, CaCl2 and KH2PO4 was 2:1:1.

[0020] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known in the art.

[0021] The acid-resistant and soil-improving composite soil conditioner provided by the present invention comprises 40-50% phosphorus-rich biochar, which can be 40%, 45% or 50%.

[0022] In this invention, the preparation method of the phosphorus-rich biochar includes the following steps: mixing the aqueous suspension of biochar with CaCl2 and KH2PO4 for a first stirring, adjusting the pH value of the resulting mixture to 10 for a second stirring, and then sequentially undergoing aging, solid-liquid separation and solid-phase drying to obtain the phosphorus-rich biochar.

[0023] In this invention, the biochar is preferably obtained from agricultural waste through anaerobic pyrolysis. The agricultural waste preferably includes one or more of rice straw, rice husks, corn stalks, and corn cobs; the volume fraction of oxygen in the anaerobic pyrolysis atmosphere is preferably below 2%; the anaerobic pyrolysis temperature is preferably 500-600℃, but can be 500, 550, or 600℃; and the time is preferably 2-3 hours, but can be 2, 2.5, or 3 hours. Preferably, the agricultural waste is sequentially washed, dried, and pulverized, then placed in a quartz crucible and placed in a muffle furnace for anaerobic pyrolysis. In this invention, the aqueous suspension of biochar is specifically formed by mixing biochar and water, and the concentration of the aqueous suspension is preferably 100-125 g / L.

[0024] In this invention, CaCl2 and KH2PO4 are preferably added to the aqueous suspension of the biochar; the mass ratio of biochar, CaCl2, and KH2PO4 is 2:1:1; and the first stirring time is preferably 30 min. Single KH2PO4 modification mainly loads phosphorus onto the surface of biochar, forming soluble or adsorbed phosphates; while the present invention uses a composite modification of CaCl2 and KH2PO4 to synthesize alkaline hydroxyapatite in situ within the pores and on the surface of the biochar, providing a buffering effect against acidic environments. It also slowly dissolves in soil or water, gradually releasing plant-absorbable phosphorus and the secondary element calcium, further enhancing its value as an acidic soil conditioner and nutrient supplement. Compared with commonly used single phosphorus source modified biochar, the CaCl2 and KH2PO4 composite modification of this invention has superior comprehensive performance, higher stability, and broader application prospects.

[0025] In this invention, the pH value is preferably adjusted using KOH solution, and the second stirring time is preferably 2 hours. In this invention, the pH value of the obtained mixture is adjusted to 10 before the second stirring, allowing CaCl2 and KH2PO4 to be successfully loaded into the biochar, increasing the loading capacity, and simultaneously promoting the formation of hydroxyapatite. In this invention, the aging time is preferably 24 hours, and the aging is carried out at room temperature, which makes the product more stable; the solid-liquid separation method can be vacuum filtration.

[0026] In this invention, the phosphorus-rich biochar can also be called modified biochar. This invention utilizes CaCl2 and KH2PO4 to modify the biochar, which alters the biochar's surface structure, increases alkalinity, enhances its resistance to acidified soils, and strengthens the slow-release capacity of the nutrient phosphorus, thus acting as a slow-release fertilizer.

[0027] The acid-resistant and soil-improving composite soil conditioner provided by this invention comprises 40-50% mixed inorganic mineral materials, which can be 40%, 45%, or 50% by mass percentage. In this invention, the mixed inorganic mineral materials include kaolin, zeolite, and fly ash, with a mass ratio of kaolin, zeolite, and fly ash of 1:1:3; the zeolite is preferably green zeolite, and the fly ash is preferably secondary fly ash. In this invention, the kaolin has a certain binding effect, facilitating the molding (e.g., granulation) of the composite soil conditioner; the zeolite and fly ash provide medium-level elements such as calcium and magnesium, which can rapidly increase the pH value of acidic soils. In this invention, the mass content of CaO in the mixed inorganic mineral materials is preferably ≥20%, the mass content of MgO is preferably ≥6%, and the particle size of the mixed inorganic mineral materials is preferably ≤0.25mm.

[0028] In this invention, the preferred method for preparing the mixed inorganic mineral material is to mix kaolin, zeolite and fly ash, and then pulverize and pass them through a 60-100 mesh sieve to obtain the mixed inorganic mineral material.

[0029] In this invention, the mixed inorganic mineral material composed of kaolin, zeolite and fly ash can quickly replenish calcium, magnesium and silicon elements in the soil. The abundant surface active sites of inorganic minerals can also promote the formation of aggregates, improve the physical structure of the soil, and the mixed inorganic mineral material can also absorb a large amount of industrial by-products.

[0030] The acid-resistant and soil-improving compound soil conditioner provided by this invention, by weight percentage, comprises 1-2% compound microbial inoculant, which can be 1%, 1.5%, or 2%. In this invention, the compound microbial inoculant comprises *Bacillus licheniformis*, *Bacillus licheniformis*, and *Bacillus subtilis*, with the ratio of effective viable bacteria counts of these bacteria being (1.5-2):(0.8-1):(0.8-1), which can be 2:1:1. In embodiments of this invention, the *Bacillus licheniformis*, *Bacillus licheniformis*, and *Bacillus subtilis* are respectively selected from the following corresponding strains: the *Bacillus licheniformis* has the preservation number CGMCC No. 33913, the *Bacillus licheniformis* has the preservation number CGMCC No. 33912, and the *Bacillus subtilis* has the preservation number CGMCC No. 33911. In this invention, the effective viable bacteria count of the compound microbial inoculant is ≥50 × 10⁻⁶. 8CFU / g. In this invention, the gelatinous Bacillus, Bacillus licheniformis, and Bacillus subtilis have a complementary and synergistic relationship. Specifically, the gelatinous Bacillus has a better effect on nitrogen fixation and activation of soil nutrients (potassium, phosphorus, etc.) than Bacillus licheniformis and Bacillus subtilis, while Bacillus licheniformis and Bacillus subtilis are responsible for inhibiting pathogens. Together, they create a healthy and fertile growth environment for plant roots, thereby comprehensively achieving the goals of disease prevention, growth promotion, yield increase, quality improvement, and soil improvement.

[0031] In this invention, the composite microbial agent preferably includes a protectant and a carrier. The protectant is preferably trehalose, and the carrier is preferably biochar. The biochar is the same as that described in the above technical solution (i.e., obtained by anaerobic pyrolysis of agricultural waste), and will not be described again here. The mass of the protectant and the carrier is preferably 5-10% of the total mass of Bacillus subtilis, Bacillus licheniformis, and Bacillus subtilis.

[0032] In this invention, the preparation method of the composite microbial agent preferably includes the following steps: Bacillus subtilis, Bacillus licheniformis, and Bacillus subtilis were separately inoculated into liquid culture medium for fermentation to obtain fermentation broths. The three fermentation broths were then centrifuged to obtain concentrated bacterial cell solutions. These three concentrated bacterial cell solutions were mixed and freeze-dried to obtain the composite microbial agent. This invention does not have special requirements for the liquid culture medium; any liquid culture medium well-known to those skilled in the art can be used. In this invention, when the composite microbial agent further includes a protectant and a carrier, these are added to the mixture of the three concentrated bacterial cell solutions. The protectant and carrier provide a suitable environment for the microorganisms and mitigate the effects of the drying process.

[0033] In this invention, the compound microbial agent has functions of phosphorus solubilization, potassium solubilization, growth promotion, and antagonism.

[0034] The acid-resistant and soil-improving composite soil conditioner provided by this invention, by weight percentage, comprises 8-18% organic binder, which can be 9%, 10%, or 15%. In this invention, the organic binder preferably comprises bentonite, sodium humate, and potassium humate, and the preferred mass ratio of bentonite, sodium humate, and potassium humate is 3:1:1. In this invention, the organic binder can be obtained by mixing bentonite, sodium humate, and potassium humate.

[0035] In this invention, the pH value of the acid-resistant and soil-improving composite soil conditioner is preferably 8.5-10; the organic matter content is preferably ≥20wt%; the total nutrients are preferably ≥2wt%, calculated as N+P2O5+K2O; the calcium content is preferably ≥10wt%, calculated as CaO; the magnesium content is preferably ≥3wt%, calculated as MgO; and the effective viable bacteria count is preferably ≥0.5×10⁻⁶. 8 CFU / g.

[0036] The soil conditioner provided by this invention has multiple improvement effects through the synergistic action of organic-inorganic-microorganisms, effectively reducing soil acidity, increasing soil fertility, improving soil structure (significantly increasing the content of water-stable macroaggregates), and increasing crop yield.

[0037] This invention provides a method for preparing the acid-resistant and soil-improving composite soil conditioner described in the above technical solution, comprising the following steps: The phosphorus-rich biochar, mixed inorganic mineral materials, composite microbial agents, and organic binders are mixed to obtain the acid-resistant and soil-improving composite soil conditioner.

[0038] This invention does not have specific requirements for the mixing method, as long as the components are mixed evenly. In this invention, after mixing, it is preferable to further granulate the resulting composite material. In this invention, the moisture content of the composite material is preferably 12-15 wt%. When the moisture content of the composite material is higher than the above range, the composite material is dried. The granulation is specifically carried out in a granulator, and the particle size of the granulated material is preferably 2-4 mm.

[0039] This invention provides the application of the acid-resistant and soil-improving composite soil conditioner described in the above technical solutions or the acid-resistant and soil-improving composite soil conditioner prepared by the above technical solutions in the improvement of acidified soil.

[0040] In this invention, the pH value of the acidified soil is preferably 4.5 to 6.5, and the application rate of the acid-resistant and quality-improving composite soil conditioner in the acidified soil is preferably 50 to 500 kg / mu.

[0041] To further illustrate the present invention, the acid-resistant and soil-improving composite soil conditioner, its preparation method, and its application provided by the present invention are described in detail below with reference to examples, but these should not be construed as limiting the scope of protection of the present invention.

[0042] In the following examples, each component was prepared by the following methods: Biochar: Rice straw is collected, washed, dried, and crushed, then placed in a quartz crucible and placed in a muffle furnace. Under limited oxygen conditions (oxygen volume fraction below 2%), the temperature is raised to 500℃ and pyrolyzed at this temperature for 2 hours to obtain biochar.

[0043] Phosphorus-rich biochar: Biochar and water are mixed into a uniform suspension (concentration of 100 g / L), anhydrous CaCl2 and KH2PO4 are added and stirred for 30 min (biochar:CaCl2:KH2PO4=2:1:1 (mass ratio)), the pH value is adjusted to 10 with KOH solution, stirring is continued for 2 h, and then aged at room temperature for 24 h. After vacuum filtration and drying, phosphorus-rich biochar is obtained.

[0044] Mixed inorganic mineral materials: Kaolin, zeolite and secondary fly ash are mixed and crushed in a mass ratio of 1:1:3 and passed through a 60-100 mesh sieve to obtain mixed inorganic mineral materials. The elemental composition of the secondary fly ash is shown in Table 1.

[0045] Table 1. XRF elemental composition (wt%) of secondary fly ash

[0046] Compound microbial inoculant: *Bacillus jelly-like*, *Bacillus licheniformis*, and *Bacillus subtilis* were separately inoculated into liquid culture medium for fermentation to obtain fermentation broth. The three fermentation broths were centrifuged to obtain concentrated cell solutions, which were then mixed in a 2:1:1 ratio (ratio of effective viable cell counts of *Bacillus jelly-like*, *Bacillus licheniformis*, and *Bacillus subtilis*). 5 wt% trehalose and 5 wt% biochar (prepared using the same method as above) were added, and the mixture was freeze-dried to obtain the compound microbial inoculant. The preservation number of *Bacillus jelly-like* is CGMCC No. 33913, that of *Bacillus licheniformis* is CGMCC No. 33912, and that of *Bacillus subtilis* is CGMCC No. 33911.

[0047] Organic binder: Bentonite, sodium humate and potassium humate are mixed in a mass ratio of 3:1:1 to obtain an organic binder.

[0048] Example 1 40wt% phosphorus-rich biochar, 50wt% mixed inorganic mineral materials, 1wt% composite microbial agent and 9wt% organic binder are mixed, dried to a moisture content of ≤15wt%, and then placed in a granulator for granulation. The granulated particle size is 2~4mm to obtain composite soil conditioner 1.

[0049] Example 2 45wt% phosphorus-rich biochar, 45wt% mixed inorganic mineral materials, 1wt% composite microbial agent and 9wt% organic binder are mixed, dried to a moisture content of ≤15wt%, and then placed in a granulator for granulation. The granulated particle size is 2~4 mm to obtain composite soil conditioner 2.

[0050] Example 3 Mix 50wt% phosphorus-rich biochar, 40wt% mixed inorganic mineral materials, 1wt% composite microbial agent and 9wt% organic binder, dry to a moisture content of ≤15wt%, and place in a granulator for granulation. The granulated particle size is 2~4 mm to obtain composite soil conditioner 3.

[0051] Table 2 shows a comparison of the physicochemical properties of biochar before and after modification. The modified biochar is the phosphorus-rich biochar. Table 3 shows the physicochemical parameters of the composite soil conditioners prepared in Examples 1-3.

[0052] Table 2 Physicochemical properties of biochar before and after modification

[0053] Table 3. Physicochemical parameters of the composite soil conditioners prepared in Examples 1-3

[0054] Experimental Example 1 This experiment is a potted plant experiment.

[0055] The soil samples were collected from the 0-20cm topsoil layer of the farm, air-dried naturally, and then sieved through a 2mm sieve. The basic physicochemical properties are as follows: pH 4.62, organic matter content 13.47g / kg, total nitrogen content 0.65g / kg, available nitrogen content 94.73mg / kg, available phosphorus content 2.16mg / kg, and available potassium content 114.85mg / kg.

[0056] The pot experiment used plastic gallon pots with a diameter of 19.5 cm, a height of 14 cm, and a bottom diameter of 12 cm. 1.5 kg of test soil was thoroughly mixed with a soil conditioner (2.0% of the soil mass) and then placed into the gallon pots. An equal amount of base fertilizer (15-15-15 compound fertilizer, 50 kg / mu) and water at 70% of the soil's field capacity were added. After 7 days of activation, 10 cabbage seeds were sown in each pot. After emergence, thinning was performed, and 5 plants per pot were transplanted. Watering was done every 2-3 days depending on soil moisture, and conventional cultivation management was followed. The experiment included four treatments: a control group (no conditioner applied), experimental group 1 (using the compound soil conditioner of Example 1), experimental group 2 (using the compound soil conditioner of Example 2), and experimental group 3 (using the compound soil conditioner of Example 3).

[0057] After the experiment, plant samples were harvested, washed, and their plant height, root length, and fresh weight were measured. The soil was broken up, mixed, air-dried, sieved, and then its pH, organic matter, total nitrogen, alkaline nitrogen, available phosphorus, and available potassium were measured. Soil pH was determined using the potentiometry method (water:soil = 2.5 mL: 1 g), organic matter content was determined using the potassium dichromate titration method with external heating, total nitrogen content was determined using a mixed catalyst-semi-automatic Kjeldahl nitrogen analyzer, alkaline nitrogen content was determined using the alkaline diffusion method, and available phosphorus content was determined using a 0.5 mg / L... -1 The NaHCO3 extraction-molybdenum antimony colorimetric method was used to determine the available potassium content, and the NH4OAc extraction-flame photometric method was used to determine the available potassium content. The results are shown in Tables 4 and 5.

[0058] Table 4 Soil physicochemical properties after the experiment

[0059] Table 5 Germination rate and growth of leafy greens

[0060] As shown in Tables 4-5, the application of the composite soil conditioner in this embodiment of the invention can raise the pH of acidic soil from 4.51 to 6.25-6.75. The increases in organic matter, total nitrogen, available nitrogen, available phosphorus, and available potassium are 53.65%-62.55%, 50.62%-56.79%, 154.18%-165.32%, 124.91%-171.50%, and 173.95%-191.17%, respectively. The content of water-stable macroaggregates is significantly increased, and the soil structure is improved. The application of the composite soil conditioner of this invention can promote the germination rate of leafy green vegetable seeds and improve the growth of leafy green vegetables. Plant height, root length, and fresh weight are 1.10-1.27 times, 1.09-1.18 times, and 2.10-2.28 times that of the control group, respectively.

[0061] Experimental Example 2 This experiment is a field experiment.

[0062] The basic physicochemical properties of the soil in the experimental site are as follows: pH 4.34, organic matter content 30.51 g / kg, total nitrogen content 3.53 g / kg, available nitrogen content 171.50 mg / kg, available phosphorus content 145.66 mg / kg, and available potassium content 418.63 mg / kg.

[0063] The strawberry variety used in the experiment was "Red Cheek". Four treatments were set up: a control group (no conditioner applied), experimental group 1 (using the compound soil conditioner of Example 1), experimental group 2 (using the compound soil conditioner of Example 2), and experimental group 3 (using the compound soil conditioner of Example 3). A completely randomized design was used, with each treatment replicated three times. The plot area was 1m × 20m = 20m². 2Except for the control treatment, all other treatments received the same amount of conditioner at a rate of 500 kg / mu, applied as a base fertilizer before sowing. Strawberry cultivation was managed according to conventional methods.

[0064] Strawberry plants and fruits were harvested after the experiment. They were washed, and plant height, single fruit weight, and sugar content were measured. Soil samples were collected, air-dried, sieved, and then their pH, organic matter, total nitrogen, available nitrogen, available phosphorus, and available potassium were measured. The test results are shown in Tables 6 and 7.

[0065] Table 6 Soil physicochemical properties after the experiment

[0066] Table 7 Strawberry Quality and Yield

[0067] As shown in Tables 6 and 7, the application of the compound soil conditioner in this embodiment of the invention can increase the pH value, organic matter, and nutrient content of strawberry soil. Specifically, the pH increases by 0.36–0.53 units, organic matter increases by 9.55%–12.31%, and available nutrients increase by 11.93%–36.63%. The application of this compound soil conditioner can also effectively increase strawberry plant height, single fruit weight, sugar content, and yield, with increases of 3.28%–35.96%, 11.68%–21.32%, 7.07%–15.52%, and 5.36%–15.62%, respectively.

[0068] In summary, the composite soil conditioner provided by this invention can achieve synergistic effects of multiple components, and has multiple improvement effects such as reducing soil acidity, increasing soil fertility, improving soil structure, and increasing crop yield. It can be used as a highly efficient conditioner for improving acidic soil.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An acid-resistant and soil-improving composite soil conditioner, characterized in that, The components include the following components by mass percentage: Phosphorus-rich biochar 40-50%, mixed inorganic mineral materials 40-50%, composite microbial agent 1-2%, organic binder 8-18%; The mixed inorganic mineral material includes kaolin, zeolite and fly ash, and the mass ratio of kaolin, zeolite and fly ash is 1:1:

3. The composite microbial agent includes Bacillus subtilis, Bacillus licheniformis, and Bacillus subtilis, with the ratio of effective viable counts of the Bacillus subtilis, Bacillus licheniformis, and Bacillus subtilis being (1.5~2):(0.8~1):(0.8~1); the effective viable count of the composite microbial agent is ≥50×10⁻⁶. 8 CFU / g; The method for preparing the phosphorus-rich biochar includes the following steps: The aqueous suspension of biochar was mixed with CaCl2 and KH2PO4 and stirred for the first time. The pH of the resulting mixture was adjusted to 10 and stirred for the second time. The mixture was then subjected to aging, solid-liquid separation and solid-phase drying to obtain the phosphorus-rich biochar. The mass ratio of biochar, CaCl2 and KH2PO4 was 2:1:

1.

2. The acid-resistant and soil-improving composite soil conditioner according to claim 1, characterized in that, The first stirring time is 30 minutes, the second stirring time is 2 hours, and the aging time is 24 hours; the pH value is adjusted using KOH solution.

3. The acid-resistant and soil-improving composite soil conditioner according to claim 1, characterized in that, The mixed inorganic mineral material contains ≥20% CaO and ≥6% MgO by mass, and the particle size of the mixed inorganic mineral material is ≤0.25mm.

4. The acid-resistant and soil-improving composite soil conditioner according to claim 1, characterized in that, The accession number of the gelatinous Bacillus is CGMCC No. 33913, the accession number of the Bacillus licheniformis is CGMCC No. 33912, and the accession number of the Bacillus subtilis is CGMCC No. 33911.

5. The acid-resistant and soil-improving composite soil conditioner according to claim 1 or 4, characterized in that, The preparation method of the compound microbial agent includes the following steps: Bacillus subtilis, Bacillus licheniformis, and Bacillus subtilis were inoculated into liquid culture medium and fermented to obtain fermentation broth. The three fermentation broths were centrifuged to obtain concentrated bacterial cell solutions. The three concentrated bacterial cell solutions were mixed and freeze-dried to obtain the composite microbial agent.

6. The acid-resistant and soil-improving composite soil conditioner according to claim 1, characterized in that, The organic binder comprises bentonite, sodium humate, and potassium humate, wherein the mass ratio of bentonite, sodium humate, and potassium humate is 3:1:

1.

7. The acid-resistant and soil-improving composite soil conditioner according to claim 1, characterized in that, The acid-resistant and soil-improving compound soil conditioner has the following characteristics: pH value 8.5-10; organic matter content ≥20wt%; total nutrients ≥2wt%, calculated as N+P2O5+K2O; calcium content ≥10wt%, calculated as CaO; magnesium content ≥3wt%, calculated as MgO; and effective viable bacteria count ≥0.5×10⁻⁶. 8 CFU / g.

8. The preparation method of the acid-resistant and soil-improving composite soil conditioner according to any one of claims 1 to 7, characterized in that, Includes the following steps: The phosphorus-rich biochar, mixed inorganic mineral materials, composite microbial agents, and organic binders are mixed to obtain the acid-resistant and soil-improving composite soil conditioner.

9. The preparation method according to claim 8, characterized in that, After mixing, the mixture is further granulated, and the granulated particle size is 2-4 mm.

10. The application of the acid-resistant and soil-improving composite soil conditioner according to any one of claims 1 to 7 or the acid-resistant and soil-improving composite soil conditioner prepared by the preparation method according to claim 8 or 9 in the improvement of acidified soil.

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