Soil improvement fertilizer based on yellow sandy soil as well as preparation method and application of soil improvement fertilizer

Abstract

The invention discloses a soil improvement fertilizer based on Yangtze sandy soil and a preparation method and application thereof, and the preparation method comprises the following steps: spraying and inoculating a microbial agent of urea-decomposing bacteria on the surfaces of clay particles, mixing with calcium chloride powder, and then mixing with a sodium alginate solution on a wet granulator to obtain coated clay; mixing the coated clay with the cellulose gel, and drying by using a supercritical drying method to obtain the composite aerogel fertilizer. Mixing the composite aerogel fertilizer with barnyard manure particles to obtain a soil improvement fertilizer; according to the prepared soil improvement fertilizer, the sandy soil structure is improved by promoting formation of soil aggregates, the soil improvement fertilizer has slow release and water retention effects through sodium alginate and cellulose gel, the retention time of the soil improvement fertilizer after fertilization is prolonged, the fertilizer efficiency of the soil improvement fertilizer after fertilization is improved, and the soil improvement effect is improved through the cementation effect of cellulose aerogel on soil. The soil improvement fertilizer provided by the invention is easier to settle, and has good improvement on the deep structure of sandy soil.

Description

Technical Field

[0001] This invention belongs to the field of organic fertilizer technology, specifically relating to soil improvement fertilizers based on sandy soil along the Yellow River, their preparation methods, and applications. Background Technology

[0002] Sandy soils in the Yellow River floodplains are widely distributed in 63 counties and districts across five provinces: Shandong, Henan, Hebei, Anhui, and Jiangsu. They are also widely distributed in 19 counties and cities in northern Anhui, including Suzhou, Chuzhou, and Fuyang. The soils in the Yellow River floodplains develop on alluvial deposits from the Yellow River floods. They are highly sandy, and long-term wind and sand activity has led to loose soil texture, poor water and fertilizer retention capacity, and low efficiency in irrigation and fertilization. This has a significant impact on crop cultivation in the Yellow River basin. Improving the soils in the Yellow River floodplains is of great importance for increasing crop yields.

[0003] Patent CN111548796A discloses a soil conditioner and its application method for improving the water and fertilizer retention of sandy soil. By spreading biochar and bentonite in the topsoil of sandy soil, the soil structure is improved and the soil's water and fertilizer retention capacity is enhanced, thereby reducing the amount of fertilizer used. However, this method requires a large amount of water to disperse the biochar and bentonite in the soil, and the improvement effect of biochar and bentonite on sandy soil is relatively limited when the water loss rate is fast.

[0004] According to the research in the literature "Application Research of Bio-based Sulfonate in Soil Desertification Control", dissolving bio-based sulfonate fertilizer in water and spraying it onto the surface of sandy soil can not only form sand crust with good wind resistance, but also has multiple functions such as water saving and water retention, anti-ultraviolet aging and anti-freeze-thaw properties, which can effectively improve the physical and chemical properties and ecological environment of saline-alkali soil.

[0005] Patent CN113121288A discloses a fertilizer containing bio-based sulfonates and its application in sand fixation and soil improvement. By mixing bio-based sulfonates with inorganic fertilizers and applying them to sandy soil, it promotes the growth of plants in saline-alkali and sandy soils and can resist the adverse environment of saline-alkali and sandy soils, improving the plants' tolerance to the environment. However, the degree of mixing between bio-based sulfonates and inorganic fertilizers in this scheme is not high, the synergistic effect is low, and the effect on improving the properties of sandy soil is relatively small. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of loose soil texture, poor water and fertilizer retention capacity of sandy soil, short retention time and easy loss of ordinary organic fertilizers in sandy soil, and small effect on improving sandy soil. The invention provides a soil improvement fertilizer based on sandy soil along the Yellow River, its preparation method and application.

[0007] This invention improves the water retention capacity of soil by using cellulose-based aerogel and sodium alginate, and promotes the formation of calcium carbonate through the decomposition of urea by urea-decomposing bacteria and the reaction of calcium ions cross-linked with sodium alginate, thereby improving soil structural stability.

[0008] The objective of this invention can be achieved through the following technical solutions: The preparation method of soil amendment fertilizer based on sandy soil along the Yellow River includes the following steps: Step 1: After air-drying and pulverizing the clay, sieve it to obtain clay particles with a particle size of 0.5-1mm. Activate and expand the urea-decomposing bacteria in yeast culture medium to obtain a bacterial agent. Spray the bacterial agent onto the surface of the clay particles to obtain bacterial agent clay. Then, stir and mix the bacterial agent clay with calcium chloride powder to make the surface of the bacterial agent clay adhere to the calcium chloride powder. After sieving, obtain the clay to be coated. Mix the clay to be coated with 30-40wt% sodium alginate solution on a wet granulator and dry it to obtain coated clay.

[0009] Step 2: Mix the coated clay with the cellulose gel, stir to disperse the coated clay, then dry it using supercritical drying, pulverize and sieve to obtain the composite aerogel fertilizer.

[0010] Step 3: Mix the compound aerogel fertilizer with manure granules to obtain soil improvement fertilizer. The mixing ratio of compound aerogel fertilizer to manure granules is 100-150g: 10-20kg.

[0011] Furthermore, the urea-decomposing bacteria in step one include, but are not limited to, Bacillus subtilis, Micrococcus, Pseudomonas aeruginosa, Bacillus pasteurellii, and Bacillus-like bacteria, as long as they have the ability to decompose urea. Preferably, they are urea-decomposing bacteria found in the soil of the fertilized area.

[0012] The number of bacterial strains in the inoculant is 8 x 10. 8 -9x10 8 cfu / mL.

[0013] Further, in step one, the ratio of the amount of bacterial agent to clay particles is 1-2 mL: 100-150 g; the ratio of the amount of bacterial agent clay to calcium chloride powder is 100-150 g: 10-15 g; and the ratio of the amount of clay to be coated to sodium alginate solution is 100-150 g: 10-20 mL.

[0014] Furthermore, in step two, the ratio of coating clay to cellulose gel is 100-150g: 300-400g.

[0015] Furthermore, the cellulose gel is prepared by the following steps: Urea and sodium hydroxide were dissolved in deionized water in a reactor. Cellulose mixed powder was added to the reactor and stirred evenly. Then 3-aminopropyltriethoxysilane was added and stirred for 30-40 min. The temperature was raised to 40-45℃ and the crosslinking reaction was carried out for 4-5 h. The gel was then filtered and washed with deionized water to obtain cellulose gel.

[0016] Furthermore, the ratio of urea, sodium hydroxide, deionized water, cellulose powder mixture and 3-aminopropyltriethoxysilane is 40-50g: 40-50g: 1.5-2L: 50-100g: 10-20g.

[0017] Furthermore, the cellulose mixed powder is prepared by the following steps: Sodium sulfite waste liquid was mixed with non-ionic adsorption resin and then shaken at 150-200 rpm in a constant temperature bath shaker at 30-40℃ for 1-2 hours. After filtration, the resin was collected to obtain the adsorption resin. The adsorption resin was washed with deionized water, and then the adsorption resin was mixed with methanol and shaken at 150-200 rpm in a constant temperature bath shaker at 30-40℃ for 20-24 hours to desorb. The filtrate was collected and the methanol in the filtrate was evaporated by rotary evaporation to obtain insoluble matter. The insoluble matter was dispersed in deionized water and freeze-dried to obtain cellulose mixed powder.

[0018] Furthermore, the ratio of sodium sulfite waste liquid to nonionic adsorption resin is 2-3L:600-800g; the ratio of adsorption resin to methanol is 600-800g:3-4L.

[0019] The beneficial effects of this invention are: The soil amendment fertilizer prepared by this invention improves the structure of sandy soil by promoting the formation of soil aggregates. Sodium alginate and cellulose gel enable the soil amendment fertilizer to have slow-release and water-retaining effects, thereby increasing the retention time and fertilizer efficacy of the soil amendment fertilizer after fertilization. The cementing effect of cellulose aerogel on the soil further enhances the formation of soil aggregates. The soil amendment fertilizer of this invention is easier to settle and has a good effect on improving the deep structure of sandy soil.

[0020] The soil amendment fertilizer prepared by this invention utilizes the urea adsorption capacity of cellulose in cellulose gel and uses cellulose as a carrier to form nitrogen and carbon sources, promoting the reproduction of microorganisms and inoculants in the soil. The decomposition of cellulose also enhances soil fertility. Cellulose is extracted from sulfite waste liquid and is more easily decomposed by bacteria and microorganisms. By grafting urea-decomposing inoculants onto the surface of clay particles, the urea adsorbed by cellulose is more easily decomposed, improving the fertility of the soil amendment fertilizer prepared by this invention at the initial application. It also makes the ammonia gas produced after the decomposition of inoculants more easily adsorbed by the clay, reducing nitrogen loss while promoting the formation of calcium carbonate. Calcium carbonate precipitates in the soil to bind soil particles, thereby increasing shear strength and occupying the pores between particles to reduce soil permeability and improve the stability of soil structure.

[0021] The preparation method of this invention adsorbs cellulose from sulfite wastewater through the adsorption of cellulose by resin, making full use of the large amount of cellulose in straw treatment wastewater. This method is environmentally friendly and economical. Cellulose gel is prepared by using cellulose. The coated clay and cellulose gel are mixed through hydrogen bonding between cellulose and sodium alginate, resulting in good bonding. The clay particles inoculated with the bacterial agent are coated with microspheres formed by cross-linking sodium alginate and calcium chloride by wet granulation. This not only protects the bacterial agent but also provides a calcium source for calcium carbonate precipitation. The resulting coated clay particles are uniform in size, allowing for better dispersion and sedimentation. The clay can not only adsorb ammonia to promote calcium carbonate formation but also improve the structure of sandy soil. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example 1: A method for preparing a soil amendment fertilizer based on sandy soil along the Yellow River, comprising the following steps:

[0023] Step 1: Mix 2L of sodium sulfite waste liquid with 600g of non-ionic adsorption resin and shake at 150rpm in a constant temperature bath shaker at 30℃ for 1h. After filtration, collect the resin to obtain the adsorption resin. Wash the adsorption resin with deionized water to remove unadsorbed alkaline extract. Then, mix 600g of adsorption resin with 3L of methanol and shake at 150rpm in a constant temperature bath shaker at 30℃ for 20h to desorb. After filtration, collect the filtrate and rotary evaporate the methanol in the filtrate to obtain insoluble matter. Disperse the insoluble matter in deionized water and freeze-dry to obtain cellulose mixed powder.

[0024] Step 2: Dissolve 40g of urea and 40g of sodium hydroxide in 1.5L of deionized water in a reaction vessel. Add 50g of cellulose mixed powder to the reaction vessel and stir evenly. Then add 10g of 3-aminopropyltriethoxysilane and stir for 30min. Heat to 40℃ and crosslink for 4h. Filter the gel and wash the gel with deionized water to obtain cellulose gel.

[0025] Step 3: After air-drying and pulverizing the clay, sieve it to obtain clay particles with a diameter of 0.5 mm. Activate and expand the culture of *Bacillus subtilis* (accession number CCTCC AB 2013220) in yeast medium to obtain a bacterial inoculum, ensuring the inoculum contains 8 x 10^6 microorganisms. 8 The bacterial agent was sprayed onto the surface of clay particles at a ratio of 1 mL: 100 g to obtain bacterial agent clay. Then, 100 g of bacterial agent clay was mixed with 10 g of calcium chloride powder to coat the surface of the bacterial agent clay with calcium chloride powder. After sieving to remove the uncoated calcium chloride powder, the clay to be coated was obtained. 100 g of the clay to be coated was then passed through a wet granulator with 10 mL of 30 wt% sodium alginate solution to crosslink the surface of the clay into spheres. After being dried with cold air, the coated clay was obtained.

[0026] Step 4: Mix 100g of coated clay with 300g of cellulose gel, stir to disperse the coated clay, and then dry the cellulose gel using supercritical drying. The supercritical drying temperature is 45℃, the pressure is 11MPa, and the CO2 flow rate is 20g / min. After drying, pulverize and sieve to obtain composite aerogel fertilizer.

[0027] Step 5: Mix 100g of compound aerogel fertilizer with 10kg of manure granules to obtain soil amendment fertilizer. Example 2: 2.5L of sodium sulfite waste liquid was mixed with 700g of non-ionic adsorption resin and then shaken at 175rpm in a constant temperature bath shaker at 35°C for 1.5h. After filtration, the resin was collected to obtain the adsorption resin. The adsorption resin was washed with deionized water to remove unadsorbed alkaline extract. Then, 700g of adsorption resin was mixed with 3.5L of methanol and then shaken at 175rpm in a constant temperature bath shaker at 35°C for 22h to desorb. The filtrate was collected and the methanol in the filtrate was evaporated by rotary evaporation to obtain insoluble matter. The insoluble matter was dispersed in deionized water and freeze-dried to obtain cellulose mixed powder.

[0028] Step 2: Dissolve 45g of urea and 45g of sodium hydroxide in 1.75L of deionized water in a reaction vessel. Add 75g of cellulose mixed powder to the reaction vessel and stir evenly. Then add 15g of 3-aminopropyltriethoxysilane and stir for 35min. Heat to 42.5℃ and crosslink for 4.5h. Filter the gel and wash it with deionized water to obtain cellulose gel.

[0029] Step 3: After air-drying and pulverizing the clay, sieve it to obtain clay particles with a diameter of 0.75 mm. Activate and expand the *Bacillus pasteurellii* (accession number ATCC 11859) in yeast culture medium to obtain a bacterial inoculum, ensuring the bacterial count in the inoculum is 8.5 x 10⁻⁶. 8 The bacterial agent was sprayed onto the surface of clay particles at a ratio of 1.5 mL to 125 g to obtain bacterial agent clay. Then, 125 g of bacterial agent clay was mixed with 12.5 g of calcium chloride powder to coat the surface of the bacterial agent clay with calcium chloride powder. After sieving to remove the uncoated calcium chloride powder, the clay to be coated was obtained. The 125 g of clay to be coated was then passed through 15 mL of 35 wt% sodium alginate solution in a wet granulator to cross-link the surface of the clay into spheres. After being dried with cold air, the coated clay was obtained.

[0030] Step 4: Mix 125g of coated clay with 350g of cellulose gel, stir to disperse the coated clay, and then dry the cellulose gel using supercritical drying. The supercritical drying temperature is 47.5℃, the pressure is 11.5MPa, and the CO2 flow rate is 22g / min. After drying, pulverize and sieve to obtain composite aerogel fertilizer.

[0031] Step 5: Mix 125g of compound aerogel fertilizer with 15kg of manure granules to obtain soil amendment fertilizer. Example 3: A method for preparing a soil amendment fertilizer based on sandy soil along the Yellow River, comprising the following steps:

[0032] Step 1: Mix 3L of sodium sulfite waste liquid with 800g of non-ionic adsorption resin and shake at 200rpm in a constant temperature bath shaker at 40℃ for 2h. After filtration, collect the resin to obtain the adsorption resin. Wash the adsorption resin with deionized water to remove unadsorbed alkaline extract. Then, mix 800g of adsorption resin with 4L of methanol and shake at 200rpm in a constant temperature bath shaker at 40℃ for 24h to desorb. After filtration, collect the filtrate and rotary evaporate the methanol in the filtrate to obtain insoluble matter. Disperse the insoluble matter in deionized water and freeze-dry to obtain cellulose mixed powder.

[0033] Sodium sulfite waste liquid contains a large amount of organic matter such as lignin and hemicellulose, making it an excellent source of raw materials for organic fertilizers. Non-ionic adsorption resins utilize hydrophobic interactions to adsorb most of the hydrophobic lignin and hemicellulose in the waste liquid, and then desorb them in an organic solvent to obtain cellulose molecules from the waste liquid. At the same time, the insoluble matter also contains adsorbed silica particles that are insoluble in water and alcohol. The resulting cellulose mixed powder contains cellulose molecules and silica particles.

[0034] Step 2: Dissolve 50g of urea and 50g of sodium hydroxide in 2L of deionized water in a reaction vessel. Add 100g of cellulose mixed powder to the reaction vessel and stir evenly. Then add 20g of 3-aminopropyltriethoxysilane and stir for 40min. After the reaction is heated to 45℃ and crosslinked for 5h, filter the gel and wash the gel with deionized water to obtain cellulose gel.

[0035] A cellulose hydrogel is prepared by dissolving a cellulose mixture powder. Different adsorption sites derived from the hydroxyl groups on the cellulose molecules in the cellulose mixture powder, the amino groups of the grafted 3-aminopropyltriethoxysilane, and the hydroxyl groups on the surface of silica have an adsorption effect on urea, thus obtaining a cellulose hydrogel that adsorbs urea.

[0036] Step 3: After air-drying and pulverizing the clay, sieve it to obtain clay particles with a diameter of 1 mm. Activate and expand the *Bacillus subtilis* (accession number CPCC 101212) in yeast culture medium to obtain a bacterial inoculum, ensuring the inoculum contains 9 x 10^9 bacteria. 8 The bacterial agent was sprayed onto the surface of clay particles at a ratio of 2 mL: 150 g to obtain bacterial agent clay. Then, 150 g of bacterial agent clay was mixed with 15 g of calcium chloride powder to coat the surface of the bacterial agent clay with calcium chloride powder. After sieving to remove the uncoated calcium chloride powder, the clay to be coated was obtained. The 150 g of clay to be coated was then passed through 20 mL of 40 wt% sodium alginate solution in a wet granulator to cross-link the surface of the clay into spheres. After being dried with cold air, the coated clay was obtained.

[0037] Urea-decomposing bacteria are inoculated onto the surface of clay particles. Through the cross-linking effect of calcium chloride and sodium alginate, sodium alginate-coated clay particle microspheres are prepared in a wet granulation machine. This gives the bacterial agent a slow-release effect in the fertilizer, and the water-retaining effect of sodium alginate also provides a good reproductive environment for the bacterial agent. This allows the bacterial agent to better exert the decomposition effect of urea-decomposing bacteria when applied to the soil, and the applied nitrogen fertilizer is better decomposed into a nitrogen source that can be directly absorbed by plants, thereby improving soil fertility.

[0038] Step 4: Mix 150g of coated clay with 400g of cellulose gel, stir to disperse the coated clay, and then dry the cellulose gel using supercritical drying. The supercritical drying temperature is 50℃, the pressure is 12MPa, and the CO2 flow rate is 25g / min. After drying, pulverize and sieve to obtain composite aerogel fertilizer.

[0039] Coated clay is mixed with cellulose gel. Through hydrogen bonding between sodium alginate on the surfaces of the cellulose and clay, the coated clay is dispersed and bound to the cellulose gel. After drying using a supercritical drying method, a composite aerogel fertilizer with a porous volume is obtained. This composite aerogel fertilizer contains numerous pores. Upon application to the soil, as the composite aerogel fertilizer dissolves and decomposes, its volume decreases, making it easier to settle downwards in the soil. It also has a cementing effect on the soil, forming soil aggregates and improving soil structure. The microbial agent in the coated clay uses urea as a nitrogen source to decompose the cellulose... The urea adsorbed in the urea gel is converted into a nitrogen source that plants can directly utilize, promoting soil fertility. After reproduction, the microbial agent can use manure in the soil as a nitrogen source to continue decomposing the manure. During the decomposition of urea and manure, ammonia and carbon dioxide are produced. Clay particles have an adsorption effect on ammonia. Under the adsorption effect, not only is nitrogen loss reduced, but the pH value in the soil is also increased, which promotes the formation of carbonate ions from carbon dioxide and water. The carbonate ions combine with calcium ions on the surface of the clay to form calcium carbonate precipitate. Smaller calcium carbonate particles will further settle in the soil, forming soil aggregates, promoting the reproduction of microorganisms, and further improving the soil structure of sandy soil.

[0040] Step 5: Mix 150g of compound aerogel fertilizer with 20kg of manure granules to obtain soil amendment fertilizer.

[0041] The clay is yellowish-brown clay from the Anhui region. Comparative Example 1: The difference from Example 1 is that urea is not added in step two, and cellulose gel is obtained; soil-improving fertilizer is prepared using this cellulose gel. Comparative Example 2: The difference from Example 1 is that in step three, clay particles are used to replace the bacterial agent clay to obtain coated clay; the coated clay is used to make soil-improving fertilizer. Comparative Example 3: The difference from Example 1 is that in step three, the soil-improving fertilizer is prepared by replacing the coating clay with microbial clay.

[0042] Comparative Example 4: Manure granules were used to replace soil amendment fertilizer, serving as a blank control group.

[0043] Some of the reagents used in the examples and comparative examples came from the following sources: Sodium sulfite waste liquid is a by-product of rice, wheat and corn straw used in cellulose manufacturing. It has a pH of 8.5-9.5 and mainly contains lignin, hemicellulose, silica, pulping chemicals and polysaccharides.

[0044] The nonionic adsorption resin was a hydrophobic Amberlite XAD type resin, purchased from Sigma-Aldrich.

[0045] The manure granules are cow dung organic fertilizer, product number YJF389, purchased from Shijiazhuang Fuming Bio-organic Fertilizer Co., Ltd.

[0046] All other reagents used were commercially available standard reagents. Fertilizer efficacy tests were conducted on the soil amendment fertilizers prepared in Examples 1-3 and Comparative Examples 1-3. The test site was Shucheng County, Lu'an City. The test soil was sandy loam. The wheat variety used was Ningmai 24. Each treatment plot was 30 square meters, with 3 treatments and 3 replicates. The fertilizer application rate was 500 kg / hm². 2 Each treatment plot was treated with 1.5 kg of soil amendment fertilizer, and the remaining fertilizers were applied normally. 70% of all fertilizers were applied as basal fertilizer and 30% as top dressing. The experiment was conducted on October 15, 2023, with a seeding rate of 150 kg / hm². 2 The wheat was harvested on June 2, 2024. The yield and quality of the harvested wheat are shown in Table 1.

[0047] Table 1. Statistics on Wheat Yield and Quality As shown in Table 1, the soil-improving fertilizer prepared in this invention has a yield-increasing effect on wheat. Compared with the blank control group of Comparative Example 4, it significantly increased the yield and thousand-grain weight, indicating that the soil-improving fertilizer promotes the absorption of fertilizer by wheat, enhances the soil's ability to retain fertilizer efficiency, and has a certain soil-improving effect. In Comparative Example 1, since urea was not adsorbed onto cellulose, the resulting composite aerogel fertilizer did not contain urea, which reduced the nitrogen source of the microbial agent in the clay. Urea in the manure is easily soluble in water and is easily lost, resulting in less contact with the microbial agent. This reduces the rate of microbial agent reproduction and urea decomposition, thus reducing the yield-increasing effect on wheat, reducing the formation of calcium carbonate, and reducing the soil structure improvement effect.

[0048] In Comparative Example 2, due to the lack of inoculation with microbial agents, the decomposition of urea by soil microorganisms was limited, significantly reducing the fertilizer effect of urea adsorbed in cellulose and manure on wheat. Therefore, the increase in wheat yield was smaller compared to the blank control group in Comparative Example 4. In Comparative Example 3, due to the lack of coating of microbial agents with clay, some microbial agents detached from clay particles when the microbial agent clay was mixed with cellulose gel. The amount of ammonia gas produced by the decomposition of microbial agents by clay particles was reduced, the water retention and cementing effect of soil amendment fertilizer was reduced, the effect on rice yield increase was reduced, the calcium source in the soil was limited, the amount of calcium carbonate produced was greatly reduced, and the effect on soil structure improvement was small.

[0049] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing soil-improving fertilizer based on sandy soil along the Yellow River, characterized in that, Includes the following steps: Step 1: After air-drying and crushing the clay, sieve it to obtain clay particles with a particle size of 0.5-1mm. Activate and expand the urea-decomposing bacteria in yeast culture medium to obtain a bacterial agent. Spray the bacterial agent onto the surface of the clay particles to obtain bacterial agent clay. Then, stir and mix the bacterial agent clay with calcium chloride powder to make the surface of the bacterial agent clay adhere to the calcium chloride powder. After sieving, obtain the clay to be coated. Mix the clay to be coated with 30-40wt% sodium alginate solution on a wet granulator and dry it to obtain coated clay. Step 2: Mix the coated clay with the cellulose gel, stir to disperse the coated clay, then dry it using supercritical drying, pulverize and sieve to obtain the composite aerogel fertilizer. Step 3: Mix the compound aerogel fertilizer with manure granules to obtain soil improvement fertilizer. The mixing ratio of compound aerogel fertilizer to manure granules is 100-150g: 10-20kg.

2. The method for preparing soil-improving fertilizer based on sandy soil along the Yellow River according to claim 1, characterized in that, The urea-decomposing bacteria mentioned in step one is one of Bacillus sporeans, Bacillus pasteurellii, and Bacillus-like bacteria; The number of bacterial strains in the bacterial agent is 8 x 10. 8 -9x10 8 cfu / mL.

3. The method for preparing soil-improving fertilizer based on sandy soil along the Yellow River according to claim 1, characterized in that, In step one, the ratio of the amount of microbial agent to clay particles is 1-2 mL: 100-150 g; the ratio of the amount of microbial agent clay to calcium chloride powder is 100-150 g: 10-15 g. The ratio of the clay to be coated to the sodium alginate solution is 100-150g: 10-20mL.

4. The method for preparing soil-improving fertilizer based on sandy soil along the Yellow River according to claim 1, characterized in that, In step two, the ratio of coating clay to cellulose gel is 100-150g: 300-400g.

5. The method for preparing soil-improving fertilizer based on sandy soil along the Yellow River according to claim 4, characterized in that, The cellulose gel was prepared by the following steps: Urea and sodium hydroxide were dissolved in deionized water in a reactor. Cellulose mixed powder was added to the reactor and stirred evenly. Then 3-aminopropyltriethoxysilane was added and stirred for 30-40 min. The temperature was raised to 40-45℃ and the crosslinking reaction was carried out for 4-5 h. The gel was then filtered and washed with deionized water to obtain cellulose gel.

6. The method for preparing soil-improving fertilizer based on sandy soil along the Yellow River according to claim 5, characterized in that, The ratio of urea, sodium hydroxide, deionized water, cellulose powder mixture and 3-aminopropyltriethoxysilane is 40-50g:40-50g:1.5-2L:50-100g:10-20g.

7. The method for preparing soil-improving fertilizer based on sandy soil along the Yellow River according to claim 6, characterized in that, The cellulose mixed powder is prepared by the following steps: Sodium sulfite waste liquid was mixed with non-ionic adsorption resin and then shaken at 150-200 rpm in a constant temperature bath shaker at 30-40℃ for 1-2 hours. After filtration, the resin was collected to obtain the adsorption resin. The adsorption resin was washed with deionized water, and then the adsorption resin was mixed with methanol and shaken at 150-200 rpm in a constant temperature bath shaker at 30-40℃ for 20-24 hours to desorb. The filtrate was collected and the methanol in the filtrate was evaporated by rotary evaporation to obtain insoluble matter. The insoluble matter was dispersed in deionized water and freeze-dried to obtain cellulose mixed powder.

8. The method for preparing soil-improving fertilizer based on sandy soil along the Yellow River according to claim 7, characterized in that, The ratio of sodium-based sulfite waste liquid to nonionic adsorption resin is 2-3L:600-800g; the ratio of adsorption resin to methanol is 600-800g:3-4L.

9. A soil amendment fertilizer based on sandy soil along the Yellow River, characterized in that, It is prepared by the method of any one of claims 1-8 for preparing soil-improving fertilizer based on sandy soil along the Yellow River.

10. Application of soil amendment fertilizer based on sandy soil along the Yellow River in soil improvement along the Yellow River.

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