Macroelement water-soluble fertilizer for improving soil and preparation method thereof

Abstract

The invention relates to the technical field of agricultural fertilizers, in particular to a macroelement water-soluble fertilizer for improving soil and a preparation method of the macroelement water-soluble fertilizer. Tripotassium phosphate, monopotassium phosphate, disodium octoborate tetrahydrate, zinc sulfate monohydrate, microelements and a soil conditioner are compounded to obtain the macroelement water-soluble fertilizer capable of promoting plant growth and improving soil quality. The macroelement water-soluble fertilizer also has a soil loosening function; in the soil conditioner A, the porous structure of the coal gangue can provide a relatively stable living environment for the microorganism sporosarcina pasteurii while increasing the total porosity of the soil and playing a synergistic effect with the sporosarcina pasteurii and the polyvinyl alcohol, and a plant growth regulator secreted by the sporosarcina pasteurii is adsorbed and slowly released; leaching of nutrients is avoided; the soil conditioner B effectively exerts the synergistic remediation effect of the calcium conditioner, the sodium alginate and the humic acid on the soil, the slow release time of the humic acid is prolonged, soil hardening is improved, and the soil conditioner has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of agricultural fertilizer technology, and in particular to a water-soluble fertilizer containing macro-elements for improving soil and its preparation method. Background Technology

[0002] Modern agriculture faces complex challenges. With the continuous growth of the global population and the ever-increasing demand for food, water-soluble fertilizers containing macronutrients are widely used to ensure crop yields, leading to a sustained rise in market demand. Water-soluble fertilizers, with their significant advantages such as rapid absorption and utilization by crops and flexible application methods, occupy an increasingly crucial position in the process of precision and intensive agricultural development, demonstrating broad application prospects.

[0003] On the one hand, facility agriculture is booming, and modern planting models such as greenhouses and hydroponics place higher demands on the water solubility and rapid effectiveness of fertilizers. Water-soluble fertilizers can be precisely applied through drip irrigation and sprinkler irrigation systems, meeting the needs of precision management in facility agriculture. They can supply nutrients in a timely manner at key stages of crop growth, greatly improving resource utilization efficiency, reducing fertilizer waste and soil pollution, and providing a solid guarantee for the year-round supply and quality optimization of agricultural products. Their market share is expected to continue to expand.

[0004] On the other hand, as consumers pay increasing attention to the quality and safety of agricultural products, green and organic agriculture is gradually becoming the mainstream trend. High-quality water-soluble fertilizers contain little or no heavy metals, hormones, or other harmful substances, which can help produce high-quality agricultural products that are nutritious, delicious, and meet pesticide residue standards. These products meet high-end market and export standards, making them highly competitive in domestic and international markets and possessing enormous development potential.

[0005] Water-soluble fertilizer containing macronutrients is a type of multi-element, fully water-soluble fertilizer that dissolves completely in water. It dissolves rapidly in water, making it easier for crops to absorb, and its absorption and utilization rate is relatively high. It is a fast-acting fertilizer that provides comprehensive nutrition, requires only a small amount, and has quick results. It is a liquid or solid fertilizer that can be dissolved or diluted in water for applications such as irrigation, foliar fertilization, hydroponics, seed soaking, and root dipping.

[0006] However, when water-soluble fertilizers containing macronutrients are used in crop cultivation, the different physiological acid-base reactions of various salts in the nutrient solution after the crop roots absorb the various ions in the solution will inevitably affect the pH changes of the nutrient solution. When the pH range of the water-soluble fertilizer containing macronutrients is not suitable for crop root growth, it will affect the crop's absorption of nutrients such as nitrogen, phosphorus, potassium, and micronutrients. Furthermore, the sulfate, phosphate, and carbonate ions remaining after the crops absorb the fertilizer will form insoluble compounds with metal cations in the soil, causing the soil to become compacted, reducing permeability, and hindering normal crop growth and development.

[0007] Therefore, based on the relevant technologies mentioned above, there is an urgent need to develop a water-soluble fertilizer containing macro-elements for improving soil and its preparation method. Summary of the Invention

[0008] In view of this, the purpose of this invention is to provide a water-soluble fertilizer containing macro-elements for improving soil and its preparation method, so as to solve the problem that the use of water-soluble fertilizers containing macro-elements in the prior art easily causes soil compaction.

[0009] To achieve the above objectives, the present invention provides a water-soluble fertilizer containing macro-elements for improving soil and a method for preparing the same.

[0010] A water-soluble fertilizer containing macro-elements for improving soil comprises the following raw materials in parts by weight: Tripotassium phosphate 800-1000 parts; potassium dihydrogen phosphate 68-82 parts; sodium octaborate tetrahydrate 8-10 parts; zinc sulfate monohydrate 1-2 parts; trace elements 1-2 parts; soil conditioner 43-55 parts; deionized water 500-580 parts; The soil conditioner is obtained by mixing soil conditioner A and soil conditioner B; The soil conditioner A is prepared from coal gangue, Bacillus pasteurellii, and polyvinyl alcohol. Soil conditioner B is prepared from humic acid, activated carbon, and sodium alginate.

[0011] Preferably, the mass ratio of soil conditioner A to soil conditioner B in the soil conditioner is 22-28:7-10; The trace element is at least one of manganese sulfate, ferrous sulfate, copper sulfate, and ammonium molybdate.

[0012] Preferably, the soil conditioner A is prepared by the following method: Step A1. Activate *Pasteurella spp.* in a culture medium at 25-30°C for 22-24 hours, then centrifuge at 4000-5000 rpm for 15-20 minutes, discard the supernatant, collect the bacterial cells, and prepare a bacterial suspension with sterile water to obtain *Pasteurella spp.* bacterial suspension. Step A2. Crush the coal gangue to 1-5μm and calcine it at 550-600°C for 2-2.5h. After calcination, allow it to cool naturally to room temperature to obtain pretreated coal gangue. Then, spray the suspension of Bacillus pasteurellus on the pretreated coal gangue, stir it evenly, turn it over every 2h, and control the temperature at 33-37°C. After 2-3 days of treatment, dry it to obtain the coal gangue composite. Step A3. Add polyvinyl alcohol to deionized water, mix well, add urea, heat to 82-88°C, stir for 30-50 minutes, and then cool to 45-50°C to obtain a polyvinyl alcohol solution. Step A4. Preheat the coal gangue composite to 38-43°C and add it to the fluidized bed coating machine. Then, atomize the polyvinyl alcohol solution through a spray gun and spray it onto the surface of the coal gangue composite. Place it in an oven at 37-42°C and dry for 6-8 hours to obtain soil conditioner A.

[0013] Preferably, the culture medium formula in step A1 is: 15g molasses, 5g soybean peptone, 60g urea, 0.5g potassium dihydrogen phosphate, 1000mL distilled water, pH 7-7.2; The viable count of *Pasteurella multocida* in the *Pasteurella multocida* suspension described in step A2 is 5 × 10⁻⁶. 8 -5×10 10 CFU / mL; The ratio of the Pasteurella multocida suspension to the pretreated coal gangue is 20-30 mL: 10-13 g.

[0014] Preferably, the ratio of polyvinyl alcohol, deionized water and urea used in step A3 is 3.5-5.5g:93-110mL:0.1-0.17g.

[0015] Preferably, the ratio of coal gangue composite to polyvinyl alcohol solution in step A4 is 20-30g:1-2.5mL; The spray rate of the spray gun during atomization is 3-4 mL / min, and the atomization pressure is 0.2-0.4 MPa.

[0016] Preferably, the soil conditioner B is prepared as follows: Step B1. Disperse charcoal powder and potassium hydroxide in deionized water and dry at 70-80°C. Then, heat to 750-800°C under a nitrogen atmosphere at a heating rate of 5°C / min and keep at a constant temperature for 2-3 hours for activation. Wash with 1 mol / L hydrochloric acid and deionized water until neutral, and then dry at 70-80°C to obtain activated carbon. Step B2. Activated carbon is ultrasonically dispersed in an aqueous solution of humic acid with a concentration of 1-1.2 mg / mL and stirred at room temperature in the dark for 22-24 hours. Then, sodium alginate is added and stirred for another 30-50 minutes to obtain a suspension. This suspension is then injected dropwise into a 5% calcium chloride aqueous solution using a syringe pump. After filtration, washing, and freeze-drying, soil conditioner B is obtained.

[0017] Preferably, the ratio of charcoal powder, potassium hydroxide and deionized water in step B1 is 1-1.5g:3-4.5g:18-25mL.

[0018] Preferably, the ratio of activated carbon, humic acid aqueous solution, sodium alginate and calcium chloride aqueous solution in step B2 is 0.92-1.1g:50-60mL:1.3-1.6g:100mL.

[0019] A method for preparing a water-soluble fertilizer containing macro-elements for improving soil includes the following steps: Step S1. Add tripotassium phosphate, potassium dihydrogen phosphate, sodium octaborate tetrahydrate, zinc sulfate monohydrate and trace elements to warm water at 48-52℃, and stir magnetically at 440-460 r / min for 18-22 min to obtain mixture 1; Step S2. Add the soil conditioner to the mixture 1 and stir at a speed of 180-220 r / min for 30-50 min to obtain a water-soluble fertilizer of macro-elements for improving soil.

[0020] The beneficial effects of this invention are: This invention provides a water-soluble fertilizer containing macronutrients for improving soil and its preparation method. The invention utilizes a compound of tripotassium phosphate, potassium dihydrogen phosphate, sodium octaborate tetrahydrate, zinc sulfate monohydrate, trace elements, and a soil conditioner to obtain a water-soluble fertilizer that promotes plant growth and loosens soil. The soil conditioner is obtained by mixing soil conditioner A and soil conditioner B. In soil conditioner A, pre-treated coal gangue is loaded with *Bacillus pasteurellii*, which improves soil aggregate structure and enhances soil water retention capacity. Then, polyvinyl alcohol is applied to improve the overall molecular stability and water solubility. The porous structure of the coal gangue increases the total porosity of the soil and works synergistically with *Bacillus pasteurellii* and polyvinyl alcohol, while also providing a suitable environment for the microorganism *Bacillus pasteurellii*. The presence of *Scutellaria baicalensis* provides a relatively stable living environment, allowing for the adsorption and slow release of its secreted plant growth regulators, thus preventing nutrient leaching. In soil conditioner B, humic acid is loaded onto activated carbon with a rich porous structure, mixed with sodium alginate, and then added dropwise to a calcium chloride solution, resulting in soil conditioner B with a spherical structure. Humic acid promotes the formation of soil aggregates, improves soil fertility, promotes nutrient absorption, and stabilizes the soil, but it is prone to dehydration and inactivation in a short period. Soil conditioner B effectively leverages the synergistic remediation effects of calcium conditioner, sodium alginate, and humic acid on the soil. While extending the slow-release time of humic acid, it also helps stabilize soil pH, increase soil nutrient content, and improve soil compaction. Compared with existing technologies, it has broad application prospects. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0022] The sources and properties of some of the raw materials used in this invention are as follows: The *Sporoscrcina pasteurii* strain used in this invention is *Sporoscrcina pasteurii* MK-1, which is disclosed in the invention patent with authorization announcement number "CN118355760A" entitled "A method for improving soil carbon sequestration capacity" and accession number CGMCCNo.27818.

[0023] Example 1: A method for preparing a water-soluble fertilizer containing macro-elements for improving soil, comprising the following steps: S1. Weigh 15g molasses, 5g soybean peptone, 60g urea, and 0.5g potassium dihydrogen phosphate, add them to 1000mL of distilled water and stir until completely dissolved. Adjust the pH to 7, filter, and sterilize at 121℃ for 15min to obtain the culture medium. S2. Place *Bacillus pasteurellii* in a culture medium at 25°C for 22 h to activate it, then centrifuge at 4000 rpm for 15 min, discard the supernatant, collect the bacterial cells, and prepare a bacterial suspension with sterile water to obtain *Bacillus pasteurellii* bacterial suspension. S3. The coal gangue was crushed to 1μm and calcined at 550°C for 2 hours. After calcination, it was naturally cooled to room temperature to obtain pretreated coal gangue. Then, 20mL of Bacillus pasteurellus suspension was sprayed onto 10g of pretreated coal gangue, stirred evenly, turned over every 2 hours, and the temperature was controlled at 33°C. After treatment for 2 days, it was dried to obtain the coal gangue composite. S4. Add 3.5g of polyvinyl alcohol to 93mL of deionized water, mix well, add 0.1g of urea, heat to 82°C, stir for 30min, and then cool to 45°C to obtain a polyvinyl alcohol solution. S5. 20g of coal gangue composite was preheated to 38°C and added to a fluidized bed coating machine. Then, 1mL of polyvinyl alcohol solution was atomized by a spray gun at a spray rate of 3mL / min and an atomization pressure of 0.2MPa and sprayed onto the surface of the coal gangue composite. The mixture was then placed in a 37°C oven and dried for 6h to obtain soil conditioner A. S6. Disperse 1g of charcoal powder and 3g of potassium hydroxide in 18mL of deionized water and dry at 70°C. Then, heat to 750°C at a heating rate of 5°C / min under a nitrogen atmosphere and keep at a constant temperature for 2h for activation. Wash with 1mol / L hydrochloric acid and deionized water until neutral, and then dry at 70°C to obtain activated carbon. S7. 0.92g of activated carbon was ultrasonically dispersed in 50mL of humic acid aqueous solution with a concentration of 1mg / mL. After stirring at room temperature in the dark for 22h, 1.3g of sodium alginate was added, and stirring was continued for 30min to obtain a suspension. The suspension was then injected dropwise into 100mL of calcium chloride aqueous solution with a mass fraction of 5% using a syringe pump. After filtration, washing, and freeze-drying, soil conditioner B was obtained. 22g of soil conditioner A and 7g of soil conditioner B were then mixed evenly to obtain the soil conditioner. S8. Add 800g of tripotassium phosphate, 68g of potassium dihydrogen phosphate, 8g of sodium octaborate tetrahydrate, 1g of zinc sulfate monohydrate and 1g of trace elements to 500g of warm water at 48℃, and stir magnetically at 440r / min for 18min to obtain mixture 1. S9. Add 43g of soil conditioner to mixture 1 and stir at 180r / min for 30min to obtain a water-soluble fertilizer of macro-elements for improving soil.

[0024] Example 2: A method for preparing a water-soluble fertilizer containing macro-elements for improving soil, comprising the following steps: S1. Weigh 15g molasses, 5g soybean peptone, 60g urea, and 0.5g potassium dihydrogen phosphate, add them to 1000mL of distilled water and stir until completely dissolved. Adjust the pH to 7.1, filter, and sterilize at 121℃ for 15min to obtain the culture medium. S2. Place *Bacillus pasteurellii* in a culture medium at 27°C for 23 h to activate it, then centrifuge at 4500 rpm for 17 min, discard the supernatant, collect the bacterial cells, and prepare a bacterial suspension with sterile water to obtain *Bacillus pasteurellii* bacterial suspension. S3. The coal gangue was crushed to 3μm and calcined at 570°C for 2 hours. After calcination, it was naturally cooled to room temperature to obtain pretreated coal gangue. Then, 24mL of Bacillus pasteurellus suspension was sprayed onto 11g of pretreated coal gangue, stirred evenly, turned over every 2 hours, and the temperature was controlled at 35°C. After treatment for 2 days, it was dried to obtain the coal gangue composite. S4. Add 4g of polyvinyl alcohol to 98mL of deionized water, mix well, add 0.12g of urea, heat to 84°C, stir for 35min, and then cool to 47°C to obtain a polyvinyl alcohol solution. S5. 24g of coal gangue composite was preheated to 40°C and added to a fluidized bed coating machine. Then, 1.5mL of polyvinyl alcohol solution was atomized by a spray gun at a spray rate of 3mL / min and an atomization pressure of 0.3MPa and sprayed onto the surface of the coal gangue composite. The mixture was then placed in a 40°C oven and dried for 6h to obtain soil conditioner A. S6. Disperse 1.2g of charcoal powder and 3.5g of potassium hydroxide in 20mL of deionized water and dry at 74°C. Then, heat to 770°C at a heating rate of 5°C / min under a nitrogen atmosphere and keep at a constant temperature for 2h for activation. Wash with 1mol / L hydrochloric acid and deionized water until neutral, and then dry at 74°C to obtain activated carbon. S7. 0.98g of activated carbon was ultrasonically dispersed in 54L of humic acid aqueous solution with a concentration of 1.1mg / mL. After stirring at room temperature in the dark for 23h, 1.4g of sodium alginate was added, and stirring was continued for 40min to obtain a suspension. The suspension was then injected dropwise into 100mL of calcium chloride aqueous solution with a mass fraction of 5% using a syringe pump. After filtration, washing, and freeze-drying, soil conditioner B was obtained. 24g of soil conditioner A and 8g of soil conditioner B were then mixed evenly to obtain the soil conditioner. S8. Add 850g of tripotassium phosphate, 74g of potassium dihydrogen phosphate, 9g of sodium octaborate tetrahydrate, 1.4g of zinc sulfate monohydrate and 1.4g of trace elements to 530g of warm water at 50℃, and stir magnetically at 450r / min for 20min to obtain mixture 1. S9. Add 46g of soil conditioner to mixture 1 and stir at 200r / min for 40min to obtain a water-soluble fertilizer of macro-elements for improving soil.

[0025] Example 3: A method for preparing a water-soluble fertilizer containing macro-elements for improving soil, comprising the following steps: S1. Weigh 15g molasses, 5g soybean peptone, 60g urea, and 0.5g potassium dihydrogen phosphate, add them to 1000mL of distilled water and stir until completely dissolved. Adjust the pH to 7.2, filter, and sterilize at 121℃ for 15min to obtain the culture medium. S2. Place *Bacillus pasteurellii* in a culture medium at 30°C for 24 hours to activate it, then centrifuge at 5000 rpm for 20 minutes, discard the supernatant, collect the bacterial cells, and prepare a bacterial suspension with sterile water to obtain *Bacillus pasteurellii* bacterial suspension. S3. The coal gangue was crushed to 5μm and calcined at 580°C for 2.5h. After calcination, it was naturally cooled to room temperature to obtain pretreated coal gangue. Then, 28mL of Bacillus pasteurellus suspension was sprayed onto 12g of pretreated coal gangue, stirred evenly, turned over every 2h, and the temperature was controlled at 35°C. After treatment for 3 days, it was dried to obtain the coal gangue composite. S4. Add 5g of polyvinyl alcohol to 104mL of deionized water, mix well, add 0.15g of urea, heat to 86°C, stir for 40min, and then cool to 50°C to obtain a polyvinyl alcohol solution. S5. 27g of coal gangue composite was preheated to 40°C and added to a fluidized bed coating machine. Then, 2mL of polyvinyl alcohol solution was atomized by a spray gun at a spray rate of 4mL / min and an atomization pressure of 0.3MPa and sprayed onto the surface of the coal gangue composite. The mixture was then placed in a 40°C oven and dried for 7h to obtain soil conditioner A. S6. Disperse 1.3g of charcoal powder and 4g of potassium hydroxide in 23mL of deionized water and dry at 77°C. Then, heat to 780°C at a heating rate of 5°C / min under a nitrogen atmosphere and keep at a constant temperature for 3h for activation. Wash with 1mol / L hydrochloric acid and deionized water until neutral, and then dry at 77°C to obtain activated carbon. S7. 1.05g of activated carbon was ultrasonically dispersed in 57mL of humic acid aqueous solution with a concentration of 1.1mg / mL. After stirring at room temperature in the dark for 23h, 1.5g of sodium alginate was added and stirring was continued for 45min to obtain a suspension. The suspension was then injected dropwise into 100mL of calcium chloride aqueous solution with a mass fraction of 5% using a syringe pump. The solution was filtered, washed, and freeze-dried to obtain soil conditioner B. 26g of soil conditioner A and 9g of soil conditioner B were then mixed evenly to obtain the soil conditioner. S8. Add 950g of tripotassium phosphate, 77g of potassium dihydrogen phosphate, 9g of sodium octaborate tetrahydrate, 1.7g of zinc sulfate monohydrate and 1.7g of trace elements to 550g of warm water at 52℃, and stir magnetically at 460r / min for 22min to obtain mixture 1. S9. Add 50g of soil conditioner to mixture 1 and stir at 220r / min for 45min to obtain a water-soluble fertilizer of macro-elements for improving soil.

[0026] Example 4: A method for preparing a water-soluble fertilizer containing macro-elements for improving soil, comprising the following steps: S1. Weigh 15g molasses, 5g soybean peptone, 60g urea, and 0.5g potassium dihydrogen phosphate, add them to 1000mL of distilled water and stir until completely dissolved. Adjust the pH to 7.2, filter, and sterilize at 121℃ for 15min to obtain the culture medium. S2. Place *Bacillus pasteurellii* in a culture medium at 30°C for 24 hours to activate it, then centrifuge at 5000 rpm for 20 minutes, discard the supernatant, collect the bacterial cells, and prepare a bacterial suspension with sterile water to obtain *Bacillus pasteurellii* bacterial suspension. S3. The coal gangue was crushed to 5μm and calcined at 600°C for 2.5h. After calcination, it was naturally cooled to room temperature to obtain pretreated coal gangue. Then, 30mL of Pasteurella multocida suspension was sprayed onto 13g of pretreated coal gangue, stirred evenly, turned over every 2h, and the temperature was controlled at 37°C. After treatment for 3 days, it was dried to obtain the coal gangue composite. S4. Add 5.5g of polyvinyl alcohol to 110mL of deionized water, mix well, add 0.17g of urea, heat to 88°C, stir for 50min, and then cool to 50°C to obtain a polyvinyl alcohol solution. S5. 20g of coal gangue composite was preheated to 43°C and added to a fluidized bed coating machine. Then, 2.5mL of polyvinyl alcohol solution was atomized by a spray gun at a spray rate of 4mL / min and an atomization pressure of 0.4MPa and sprayed onto the surface of the coal gangue composite. The mixture was then placed in a 42°C oven and dried for 8 hours to obtain soil conditioner A. S6. Disperse 1.5g of charcoal powder and 4.5g of potassium hydroxide in 25mL of deionized water and dry at 80°C. Then, heat to 800°C at a heating rate of 5°C / min under a nitrogen atmosphere and keep at a constant temperature for 3h for activation. Wash with 1mol / L hydrochloric acid and deionized water until neutral, and then dry at 80°C to obtain activated carbon. S7. 1.1g of activated carbon was ultrasonically dispersed in 60mL of humic acid aqueous solution with a concentration of 1.2mg / mL. After stirring at room temperature in the dark for 24h, 1.6g of sodium alginate was added and stirring was continued for 50min to obtain a suspension. The suspension was then injected dropwise into 100mL of calcium chloride aqueous solution with a mass fraction of 5% using a syringe pump. The solution was filtered, washed, and freeze-dried to obtain soil conditioner B. 28g of soil conditioner A and 10g of soil conditioner B were then mixed evenly to obtain the soil conditioner. S8. Add 1000g of tripotassium phosphate, 82g of potassium dihydrogen phosphate, 10g of sodium octaborate tetrahydrate, 2g of zinc sulfate monohydrate and 2g of trace elements to 580g of warm water at 52℃, and stir magnetically at 460r / min for 22min to obtain mixture 1. S9. Add 55g of soil conditioner to mixture 1 and stir at 220r / min for 50min to obtain a water-soluble fertilizer of macro-elements for improving soil.

[0027] Comparative Example 1: Compared with Example 1, this comparative example did not add soil conditioner during the preparation of water-soluble fertilizer containing macroelements. All other steps and parameters were the same, and will not be repeated here. The final product was water-soluble fertilizer containing macroelements.

[0028] Comparative Example 2: Compared with Example 1, this comparative example did not add soil conditioner A during the preparation of the soil conditioner. All other steps and parameters were the same, and will not be repeated here. The final product was a water-soluble fertilizer containing macro-elements.

[0029] Comparative Example 3: Compared with Example 1, this comparative example did not add soil conditioner B during the preparation of the soil conditioner. All other steps and parameters were the same, and will not be repeated here. The final product was a water-soluble fertilizer containing macro-elements.

[0030] Comparative Example 4: This comparative example differs from Example 1 only in that the "soil conditioner" is replaced with "an equal amount of humic acid". All other steps and parameters are the same, and will not be repeated here. The final product is a water-soluble fertilizer containing macro-elements.

[0031] Comparative Example 5: S1. Weigh 15g molasses, 5g soybean peptone, 60g urea, and 0.5g potassium dihydrogen phosphate, add them to 1000mL of distilled water and stir until completely dissolved. Adjust the pH to 7, filter, and sterilize at 121℃ for 15min to obtain the culture medium. S2. Place *Bacillus pasteurellii* in a culture medium at 25°C for 22 h to activate it, then centrifuge at 4000 rpm for 15 min, discard the supernatant, collect the bacterial cells, and prepare a bacterial suspension with sterile water to obtain *Bacillus pasteurellii* bacterial suspension. S3. Crush the coal gangue to 1μm and calcine it at 550°C for 2 hours. After calcination, allow it to cool naturally to room temperature to obtain pretreated coal gangue. Then, spray 20mL of Bacillus pasteurellus suspension onto 10g of pretreated coal gangue, stir evenly, turn it over every 2 hours, and control the temperature at 33°C. After 2 days of treatment, dry it to obtain soil conditioner A. S4. Disperse 1g of charcoal powder and 3g of potassium hydroxide in 18mL of deionized water and dry at 70°C. Then, heat to 750°C at a heating rate of 5°C / min under a nitrogen atmosphere and keep at a constant temperature for 2h for activation. Wash with 1mol / L hydrochloric acid and deionized water until neutral, and then dry at 70°C to obtain activated carbon. S5. 0.92g of activated carbon was ultrasonically dispersed in 50mL of humic acid aqueous solution with a concentration of 1mg / mL. After stirring at room temperature in the dark for 22h, 1.3g of sodium alginate was added and stirring was continued for 30min to obtain a suspension. The suspension was then injected dropwise into 100mL of calcium chloride aqueous solution with a mass fraction of 5% using a syringe pump. The solution was filtered, washed, and freeze-dried to obtain soil conditioner B. 22g of soil conditioner A and 7g of soil conditioner B were then mixed evenly to obtain the soil conditioner. S6. Add 800g of tripotassium phosphate, 68g of potassium dihydrogen phosphate, 8g of sodium octaborate tetrahydrate, 1g of zinc sulfate monohydrate and 1g of trace elements to 500g of warm water at 48℃, and stir magnetically at 440r / min for 18min to obtain mixture 1. S7. Add 43g of soil conditioner to mixture 1 and stir at 180r / min for 30min to obtain a water-soluble fertilizer of macro-elements for improving soil.

[0032] Comparative Example 6: Compared with Example 1, this comparative example only replaces "22g soil conditioner A and 7g soil conditioner B" with "15g soil conditioner A and 15g soil conditioner B". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, a water-soluble fertilizer containing macro-elements is obtained.

[0033] Performance testing: A plot of land with uniform soil fertility, flat terrain, and continuous cultivation was selected and divided into 11 sub-plots, each with an area of ​​20m². 2 Isolation zones were set up between the plots to prevent fertilizers from affecting each other. The macro-element water-soluble fertilizers prepared in Examples 1-4 and Comparative Examples 1-6 were applied to Chinese cabbage crops according to the fertilization plan. Finally, the chlorophyll, plant height, yield and yield increase rate of each group were measured, and the soil compaction was observed. A blank control group was also added, which refers to the performance of Chinese cabbage without water-soluble fertilizer.

[0034] Table 1. Summary of experimental data from Examples 1-4 and Comparative Examples 1-6 project chlorophyll Plant height / cm Yield / Kg / mu Production increase rate / % Soil compaction Blank group 32.4 23.8 1165 0 harden Example 1 42.4 29.8 1935 66.1 No hardening Example 2 44.1 29.2 1910 63.9 No hardening Example 3 41.5 28.6 1855 59.2 No hardening Example 4 43.6 29.2 1963 68.5 No hardening Comparative Example 1 35.4 24.7 1622 39.2 harden Comparative Example 2 38.1 26.2 1750 50.2 Partial hardening Comparative Example 3 38.6 26.5 1714 47.1 Partial hardening Comparative Example 4 36.3 25.2 1685 44.6 harden Comparative Example 5 38.4 27.1 1773 52.2 Partial hardening Comparative Example 6 40.1 27.8 1830 57.1 No hardening Data Analysis: As shown in Table 1, the water-soluble fertilizer containing macro-elements prepared in this invention has a better promoting effect on plant growth and a better soil loosening effect. This may be because continuously cultivated plots are extremely prone to soil compaction. In soil conditioner A, pre-treated coal gangue loaded with Bacillus pasteurellii can improve soil aggregate structure and enhance soil water retention capacity. Further coating with polyvinyl alcohol improves the overall molecular stability and water solubility. The porous structure of coal gangue increases the total porosity of the soil, works synergistically with Bacillus pasteurellii and polyvinyl alcohol, and provides a relatively stable living environment for the microorganism Bacillus pasteurellii. The secreted plant growth regulators are adsorbed and slowly released to avoid nutrient leaching. In soil conditioner B, humic acid is loaded onto activated carbon with a rich porous structure, mixed with sodium alginate, and then dripped into a calcium chloride solution to obtain soil conditioner B with a spherical structure. Humic acid can promote the formation of soil aggregates, improve soil fertility, promote nutrient absorption, and stabilize the soil, but it is prone to water loss and inactivation in a short period of time. Soil conditioner B effectively exerts the synergistic repair effect of calcium conditioner, sodium alginate, and humic acid on the soil, while prolonging the slow release time of humic acid, increasing soil nutrient content, thereby promoting plant growth and improving soil compaction.

[0035] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0036] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A water-soluble fertilizer for improving soil macroelements, characterized in that, The soil conditioner is prepared by mixing soil conditioner A and soil conditioner B. The soil conditioner A is prepared from coal gangue, Bacillus pasteurii and polyvinyl alcohol. The soil conditioner B is prepared from humic acid, activated carbon and sodium alginate. The mass ratio of the soil conditioner A to the soil conditioner B in the soil conditioner is 22-28:7-10. The trace element is at least one of manganese sulfate, ferrous sulfate, copper sulfate and ammonium molybdate.

2. The water-soluble fertilizer for improving soil macroelements according to claim 1, characterized in that, The preparation method of the soil conditioner A is as follows: Step A1. The Bacillus pasteurii is activated in a culture medium at 25-30°C for 22-24h, and then centrifuged at 4000-5000rpm for 15-20min, and the supernatant is discarded, and the bacterial body is collected and configured into a bacterial suspension with sterile water to obtain a Bacillus pasteurii bacterial suspension; 3. The water-soluble fertilizer for improving soil macroelements according to claim 1, characterized in that, Step A2. The coal gangue is crushed to 1-5μm, calcined at 550-600°C for 2-2.5h, and then naturally cooled to room temperature to obtain pretreated coal gangue, and the Bacillus pasteurii bacterial suspension is sprayed on the pretreated coal gangue, stirred uniformly, turned over every 2h, and the temperature is controlled at 33-37°C, and after treatment for 2-3d, drying is performed to obtain a coal gangue compound; Step A3. The polyvinyl alcohol is added to deionized water, mixed uniformly, then urea is added, heated to 82-88°C, stirred for 30-50min, and then cooled to 45-50°C to obtain a polyvinyl alcohol solution; Step A4. The coal gangue compound is preheated to 38-43°C and added to a fluidized bed coating machine, then the polyvinyl alcohol solution is atomized by a spray gun and sprayed onto the surface of the coal gangue compound, and dried in an oven at 37-42°C for 6-8h to obtain the soil conditioner A. The formula of the culture medium in step A1 is: 15g of molasses, 5g of soybean peptone, 60g of urea, 0.5g of potassium dihydrogen phosphate, 1000mL of distilled water, and pH is 7-7.2; The dosage ratio of the Bacillus pasteurii bacterial suspension to the pretreated coal gangue in step A2 is 20-30mL:10-13g.

4. The water-soluble fertilizer for improving soil macroelements according to claim 3, characterized in that, The dosage ratio of the polyvinyl alcohol, deionized water and urea in step A3 is 3.5-5.5g:93-110mL:0.1-0.17g. The viable cell count of P. acidipropionici in the bacterial suspension described in step A2 is 5 x 10 8 CFU / mL; and 10 CFU / mL. The dosage ratio of the coal gangue compound to the polyvinyl alcohol solution in step A4 is 20-30g:1-2.5mL; 5. The water-soluble fertilizer for improving soil macroelements according to claim 3, characterized in that, The spray rate of the spray gun atomization is 3-4mL / min, and the atomization pressure is 0.2-0.4MPa.

6. The water-soluble fertilizer for improving soil macroelements according to claim 3, characterized in that, The preparation method of the soil conditioner B is as follows: ​ 7. The water-soluble fertilizer for improving soil macroelements according to claim 1, characterized in that, ​ Step B1. Disperse charcoal powder and potassium hydroxide in deionized water, and dry at 70-80°C, then heat to 750-800°C at a heating rate of 5°C / min under nitrogen atmosphere, and keep constant temperature for 2-3h to activate, wash with 1mol / L hydrochloric acid and deionized water until neutral, and dry at 70-80°C to obtain activated carbon; Step B2. Disperse activated carbon in humic acid aqueous solution with a concentration of 1-1.2mg / mL under ultrasonic, and stir at room temperature for 22-24h in the dark, then add sodium alginate, continue to stir for 30-50min to obtain a suspension, and inject the suspension drop by drop into 5% calcium chloride aqueous solution by a syringe pump, filter, wash, and freeze-dry to obtain soil conditioner B.

8. The water-soluble fertilizer for improving soil macroelements according to claim 7, characterized in that, The amount ratio of charcoal powder, potassium hydroxide and deionized water in step B1 is 1-1.5g:3-4.5g:18-25mL.

9. The water-soluble fertilizer for improving soil macroelements according to claim 7, characterized in that, The amount ratio of activated carbon, humic acid aqueous solution, sodium alginate and calcium chloride aqueous solution in step B2 is 0.92-1.1g:50-60mL:1.3-1.6g:100mL.

10. The method for preparing the water-soluble fertilizer for improving soil macroelements according to any one of claims 1-9, characterized in that, The following steps are included: Step S1. Put tripotassium phosphate, potassium dihydrogen phosphate, sodium octaborate decahydrate, zinc sulfate monohydrate and trace elements into warm water at 48-52°C, and magnetically stir at a speed of 440-460r / min for 18-22min to obtain a mixed solution 1; Step S2. Add soil conditioner to the mixed solution 1, and stir at a speed of 180-220r / min for 30-50min to obtain a water-soluble fertilizer containing macroelements for improving soil.