Special charcoal-based slow-release fertilizer for sandy soil as well as preparation method and application of special charcoal-based slow-release fertilizer

Abstract

The invention provides a special charcoal-based slow-release fertilizer for sandy soil as well as a preparation method and application thereof, and belongs to the technical field of fertilizers. The special charcoal-based slow-release fertilizer for the sandy soil is prepared from amino modified biomass charcoal, urea, urea formaldehyde, monoammonium phosphate, potassium sulfate, polyglutamic acid, fulvic acid, clay, attapulgite, a compound microbial agent and sodium alginate. The compound microbial agent is prepared from halomonas (ACCC 11681), bacillus subtilis (ACCC 60429) and bacillus mucilaginosus (ACCC 10094), and the compound microbial agent is prepared from bacillus subtilis (ACCC 60429) and bacillus mucilaginosus (ACCC 10094). The invention further provides a preparation method and application of the special charcoal-based slow-release fertilizer for the sandy soil. The special charcoal-based slow-release fertilizer for the sandy soil can remarkably improve the water and fertilizer retention capacity of the sandy soil, improve the farmland productivity of the sandy soil, save fertilizer and water input and improve the yield and quality of crops.

Description

Technical Field

[0001] This invention relates to the field of fertilizer technology, specifically to a biochar-based slow-release fertilizer for sandy soil, its preparation method, and its application. Background Technology

[0002] Sandy soils, as one of the most widely distributed soil types globally, face numerous pressing challenges in agricultural production due to their coarse grains, high porosity, and low clay content. Poor water and fertilizer retention capacity is the most prominent weakness of sandy soils. Water easily seeps away through large pores, leading to low root absorption efficiency, especially in arid or semi-arid regions. Frequent irrigation not only increases production costs but may also waste groundwater resources. Simultaneously, sandy soils have weak nutrient adsorption capacity. After the application of traditional chemical fertilizers, nitrogen easily leaches into groundwater, causing pollution, while phosphorus and potassium are easily washed away by rainwater. Fertilizer utilization rates are typically less than 30%, reducing crop yield and quality and exacerbating ecological and environmental pressures.

[0003] With the deepening of the concept of sustainable agricultural development, improving the fertility and physicochemical properties of sandy soils has become a research hotspot. Currently, measures to improve sandy soils mainly include adding organic amendments (such as straw and compost) and applying water-retaining agents. However, these methods have significant limitations: organic amendments decompose quickly, have a short effective period, and require large-scale application; traditional water-retaining agents are mostly chemically synthesized materials, which are costly and may cause secondary pollution. Regarding fertilizer application, while ordinary slow-release fertilizers can reduce nutrient loss to some extent, their slow-release effect is often unsatisfactory, and they lack long-term effects on soil structure improvement. Therefore, developing a specialized fertilizer that can efficiently improve the structure of sandy soils, enhance water and fertilizer retention, and achieve precise slow-release of nutrients and improved fertilizer utilization is of great significance for promoting sustainable agricultural development in sandy soil regions. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the purpose of this invention is to provide a biochar-based slow-release fertilizer specifically for sandy soil.

[0005] The present invention also aims to provide a method for preparing and applying the biochar-based slow-release fertilizer specifically for sandy soil.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a biochar-based slow-release fertilizer specifically for sandy soil, comprising, by weight: 22-30 parts of amino-modified biochar, 5-10 parts of urea, 20-28 parts of urea-formaldehyde, 8-15 parts of monoammonium phosphate, 12-20 parts of potassium sulfate, 0.2-0.3 parts of polyglutamic acid, 5-10 parts of humic acid, 15-20 parts of clay, 12-15 parts of attapulgite, 15-20 parts of compound microbial agent, and 0.5-1.5 parts of sodium alginate; wherein the compound microbial agent is composed of Halomonas ACCC 11681, Bacillus subtilis ACCC60429, and Bacillus mucilaginosus ACCC 10094 in a viable ratio of 1:1:(1-3).

[0007] Preferably, the effective viable count of the compound microbial agent is ≥2.0 × 10⁻⁶. 9 CFU / g.

[0008] Preferably, the preparation method of the amino-modified biochar includes: impregnating crop straw biochar with a 0.5% polyacrylamide solution and then grinding it through a 20-mesh sieve; the impregnation temperature is 25~35℃ and the time is 2~4h.

[0009] Preferably, the crop straw biochar includes any one or more of wheat straw biochar and corn straw biochar.

[0010] Preferably, the method for preparing crop straw biochar includes: drying the crop straw and then crushing it to a particle size of 2-3 cm for high-temperature pyrolysis carbonization, wherein the carbonization temperature is 400-600℃ and the time is 3-4 h.

[0011] This invention also provides a method for preparing the above-mentioned biochar-based slow-release fertilizer specifically for sandy soil, comprising the following steps: Urea and urea-formaldehyde are melted and mixed, then injected under pressure into the pores of amino-modified biochar and kept warm to complete the loading. Then, it is mixed evenly with monoammonium phosphate, potassium sulfate, polyglutamic acid, humic acid, clay, and attapulgite, and granulated. A mixed solution of composite microbial agent and sodium alginate is sprayed onto the surface of the granules, and then dried to obtain a biochar-based slow-release fertilizer for sandy soil.

[0012] Preferably, the pressurization pressure is 0.8~1.0 MPa, the heat preservation temperature is 135~145℃, and the time is 20~30 min.

[0013] Preferably, the method for preparing the mixed solution includes: dissolving sodium alginate in water to obtain a 5% sodium alginate solution; and mixing the compound microbial agent with the 5% sodium alginate solution to obtain the mixed solution.

[0014] Preferably, the drying temperature is 30~40℃ and the time is 1~2h.

[0015] This invention also provides the application of the above-mentioned biochar-based slow-release fertilizer for sandy soil in the cultivation of corn and wheat in sandy soil.

[0016] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows: (1) Nanoporous structure, slow-release and long-lasting fertilizer retention. The biochar of this invention has a rich nanoporous structure, strong ability to adsorb and retain nutrients, and can increase the soil's ability to retain potassium. + Na + Ca 2+ Mg 2+ and NH4 + Its adsorption capacity allows for the slow release of nutrients, effectively preventing nitrogen loss, prolonging fertilizer effectiveness, improving nutrient utilization, and meeting the nutritional needs of crops at all growth stages.

[0017] (2) Continuously improve soil fertility, conserve soil moisture, and enhance crop resistance. The amino-modified biochar slow-release fertilizer of this invention can optimize soil structure and effectively improve soil. At the same time, the compound microbial agent increases the abundance of rhizosphere microorganisms by 2 to 3 times, promotes a healthy soil microbial environment, changes the soil microecological environment, and enhances crop resistance and nitrogen fixation capacity.

[0018] (3) Adapt to local conditions, increase yield and improve quality. This invention is rich in organic matter and nitrogen, phosphorus and potassium nutrients required by plants, and contains a variety of trace elements such as calcium, magnesium, iron, silicon, zinc and copper. It provides balanced nutrition and provides all the nutrients required for crop growth, ensuring the quality and yield of crop products, improving fertilizer utilization, saving resources and improving the environment.

[0019] (4) The raw materials are readily available and conducive to the comprehensive utilization of resources. The straw in the fertilizer formula of this invention is agricultural and forestry waste, which can significantly improve the structure of sandy soil and is easy to promote and apply on a large scale. Detailed Implementation

[0020] This invention provides a biochar-based slow-release fertilizer specifically for sandy soils, comprising, by weight: 22-30 parts amino-modified biochar, 5-10 parts urea, 20-28 parts urea-formaldehyde, 8-15 parts monoammonium phosphate, 12-20 parts potassium sulfate, 0.2-0.3 parts polyglutamic acid, 5-10 parts humic acid, 15-20 parts clay, 12-15 parts attapulgite, 15-20 parts compound microbial inoculant, and 0.5-1.5 parts sodium alginate; the compound microbial inoculant is composed of Haloxylon ammodendron (…). Halomonas sp. ACCC 11681, Bacillus subtilis ( Bacillus subtilis ACCC 60429 and Bacillus mucilaginosus ( ) Paenibacillus mucilaginousThe ACCC 10094 is composed of live bacteria in a ratio of 1:1:(1~3). Preferably, it comprises: 24~26 parts amino-modified biochar, 6~8 parts urea, 22~26 parts urea-formaldehyde, 10~12 parts monoammonium phosphate, 14~16 parts potassium sulfate, 0.25 parts polyglutamic acid, 6~8 parts humic acid, 16~18 parts clay, 13~14 parts attapulgite, 16~18 parts compound microbial agent, and 0.8~1.2 parts sodium alginate; the compound microbial agent is composed of Halomonas ACCC 11681, Bacillus subtilis ACCC 60429, and Bacillus mucilaginosus ACCC 10094 in a live bacteria ratio of 1:1:2.

[0021] The effective viable count of the compound microbial agent described in this invention is ≥2.0 × 10⁻⁶. 9 CFU / g.

[0022] The preparation method of amino-modified biochar according to the present invention includes: impregnating crop straw biochar with a 0.5% polyacrylamide solution and then grinding it through a 20-mesh sieve; the impregnation temperature is 25~35℃, preferably 28~32℃, more preferably 30℃, and the time is 2~4h, preferably 3h. The solvent of the 0.5% polyacrylamide solution in the present invention is water, and the 5% is a mass fraction. The amino-modified biochar prepared by the present invention has a specific surface area ≥250m². 2 / g, micropore ratio >40%.

[0023] The crop straw biochar of this invention includes any one or more of wheat straw biochar and corn straw biochar. Preferably, the preparation method of the crop straw biochar includes: drying the crop straw and then pulverizing it to a particle size of 2-3 cm, followed by high-temperature pyrolysis carbonization. The carbonization temperature is 400-600℃, preferably 450-550℃, more preferably 500℃, and the time is 3-4 hours. The carbonization is preferably carried out at high temperature under nitrogen protection. Preferably, the carbonized material is passed through a 20-mesh sieve. The drying process is preferably carried out to a moisture content of 8%-15%.

[0024] This invention uses amino-modified biochar as the core carrier, loading chemical fertilizers and compound microbial agents. It consists of a microbial protective layer and an amino-modified biochar slow-release fertilizer core layer, which has a rich porous structure that can significantly improve the water and fertilizer retention capacity of sandy soils. The abundant oxygen-containing functional groups (-COOH, -OH) on the surface can also adsorb nitrogen and phosphorus nutrients to form a slow-release carrier. This resource recycling governance model that "originates from agriculture, gives back to farmland, and protects the environment" is of great significance for the ecological protection of sandy soil areas and for ensuring food security.

[0025] The humic acid and amino-modified biochar in the sandy soil-specific slow-release fertilizer of this invention are used as nutrient retention agents, and attapulgite is used as a water-retaining agent. It has good adsorption properties and can adsorb and retain nutrients and water in the soil, further reducing water and nutrient loss and improving soil fertility. The compound microbial agent promotes a healthy soil microbial environment, improves crop stress resistance, increases crop yield, and improves crop quality.

[0026] The sandy soil described in this invention is preferably from the sandy soil region of the Yellow River Basin (organic matter content <1%). This invention is specifically designed for improving sandy soils along the Yellow River, offering strong water and fertilizer retention, slowing fertilizer release, improving fertilizer utilization, and meeting the drought and salt tolerance requirements of crops in the Yellow River region. Simultaneously, it provides the microenvironment necessary for the reproduction of beneficial soil microorganisms, enhancing microbial activity and abundance, strengthening crop resistance, and simultaneously improving crop yield and quality. This solves the problem of low production efficiency caused by the lack of soil aggregates and poor water and fertilizer retention in sandy soils along the Yellow River, achieving the cultivation of soil aggregates and the retention of nutrients and water, greatly improving the productivity of arable land in sandy soils along the Yellow River, saving fertilizer and water inputs, and increasing crop yield and quality.

[0027] This invention also provides a method for preparing the above-mentioned biochar-based slow-release fertilizer specifically for sandy soil, comprising the following steps: Urea and urea-formaldehyde are melted and mixed, then injected under pressure into the pores of amino-modified biochar and kept warm to complete the loading. Then, it is mixed evenly with monoammonium phosphate, potassium sulfate, polyglutamic acid, humic acid, clay, and attapulgite, and granulated. A mixed solution of composite microbial agent and sodium alginate is sprayed onto the surface of the granules, and then dried to obtain a biochar-based slow-release fertilizer for sandy soil.

[0028] In this invention, urea and urea-formaldehyde are preferably melt-mixed at 135-145°C, and the pressurization pressure is 0.8-1.0 MPa, preferably 0.9 MPa. Preferably, the molten mixture is injected into the pores of amino-modified biochar using a high-pressure melt injection device, followed by heat preservation to complete the loading. The heat preservation temperature is 135-145°C, preferably 140°C, and the time is 20-30 minutes, preferably 25 minutes.

[0029] The granulation process described in this invention involves forming particles with a diameter of 2-4 mm using a disc granulator.

[0030] The method for preparing the mixed solution of the present invention includes: preparing a sodium alginate solution with a mass concentration of 5% (5g sodium alginate dissolved in 100g water); mixing the compound microbial agent with the 5% sodium alginate solution to obtain a mixed solution, wherein the preferred mixing ratio is 1g:(4~10)mL; and the survival rate of the microbial agent in the mixed solution is ≥95%.

[0031] The present invention preferably uses spray coating technology to uniformly cover the surface of the particles at an amount of 50-80L / ton of particles, forming a microbial protective layer of 50-150μm thickness.

[0032] The drying temperature described in this invention is 30~40℃, preferably 32~38℃, more preferably 35℃, and the drying time is 1~2 hours. The drying method described in this invention is preferably airflow drying to solidify the coating, and preferably, the survival rate of the microbial agent is ≥95%.

[0033] This invention also provides the application of the above-mentioned biochar-based slow-release fertilizer for sandy soil in the planting of corn and wheat in sandy soil. The application rate is 40-60 kg / mu, which can significantly improve the yield and quality of corn and wheat.

[0034] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0035] Halomonas ACCC 11681, Bacillus subtilis ACCC 60429, and Bacillus mucilaginosus ACCC 10094 are all publicly available strains, purchased from the China Agricultural Microbial Culture Collection Center.

[0036] Unless otherwise specified, the following embodiments are all conventional methods.

[0037] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0038] Example 1 A biochar-based slow-release fertilizer specifically for sandy soils: The mixture comprises 25 parts amino-modified biochar (amino-modified wheat biochar), 8 parts urea, 25 parts urea-formaldehyde, 11 parts monoammonium phosphate, 15 parts potassium sulfate, 0.3 parts polyglutamic acid, 8 parts humic acid, 18 parts clay, 15 parts attapulgite, 15 parts compound microbial inoculant, and 0.5 parts sodium alginate. The compound microbial inoculant is composed of *Haloxylon ammodendron* ACCC 11681, *Bacillus subtilis* ACCC60429, and *Bacillus mucilaginosus* ACCC 10094 in a viable count ratio of 1:1:1, with a total effective viable count of 3.0 × 10⁻⁶. 9 CFU / g.

[0039] Preparation method: Step 1: Crush wheat straw to a particle size of 3 cm and dry it to a moisture content of 10%; carry out high-temperature pyrolysis under nitrogen protection, carbonize at 500℃ for 3.5 h to generate biochar; impregnate the biochar with 0.5% polyacrylamide solution for modification, the impregnation temperature is 25℃ for 4 h, and after drying, pass it through a 20-mesh sieve to obtain amino-modified wheat biochar.

[0040] Step 2: Melt urea and urea-formaldehyde at 140℃, pressurize to 1.0MPa using a high-pressure melt injection device, and inject into the pores of amino-modified wheat biochar. Keep warm at 135℃ for 20 minutes to form a slow-release nitrogen source biochar carrier.

[0041] Step 3: Accurately weigh the raw materials according to the mass proportions, mix the slow-release nitrogen source biochar carrier, monoammonium phosphate, potassium sulfate, polyglutamic acid, humic acid, clay, and attapulgite evenly, and then form them into granules with a particle size of 3 mm through a disc granulator to obtain the core granules of biochar-based slow-release fertilizer.

[0042] Step 4: Obtain a 5% sodium alginate solution (5g sodium alginate dissolved in 100g water); mix the compound microbial agent with the 5% sodium alginate solution, and uniformly cover the granule surface using spray coating technology to form a microbial protective layer, thus obtaining amino-modified biochar-based slow-release fertilizer granules.

[0043] Step 5: The obtained amino-modified biochar-based slow-release fertilizer is dried at 30°C for 2 hours to solidify the coating, thus obtaining a biochar-based slow-release fertilizer specifically for sandy soil.

[0044] Example 2 A biochar-based slow-release fertilizer specifically for sandy soils: The mixture contains 27 parts amino-modified biochar (amino-modified corn biochar), 6 parts urea, 27 parts urea-formaldehyde, 8 parts monoammonium phosphate, 13 parts potassium sulfate, 0.3 parts polyglutamic acid, 6 parts fulvic acid, 16 parts clay, 14 parts attapulgite, 15 parts compound microbial inoculant, and 1.0 part sodium alginate. The compound microbial inoculant is composed of *Haloxylon ammodendron* ACCC 11681, *Bacillus subtilis* ACCC 60429, and *Bacillus mucilaginosus* ACCC 10094 in a viable count ratio of 1:1:2, with a total effective viable count of 4.0 × 10⁻⁶. 9 CFU / g.

[0045] Preparation method: Step 1: Crush corn stalks to a particle size of 2 cm and dry them to a moisture content of 10%; carry out high-temperature pyrolysis under nitrogen protection, carbonize at 450℃ for 4 h to generate biochar; modify the biochar by impregnating it with 0.8% polyacrylamide solution at 35℃ for 2 h, dry it and pass it through a 20-mesh sieve to obtain amino-modified corn biochar.

[0046] Step 2: Melt urea and urea-formaldehyde at 140℃, pressurize to 0.9MPa using a high-pressure melt injection device, and inject into the pores of amino-modified corn biochar. Keep at 140℃ for 25 minutes to form a slow-release nitrogen source biochar carrier.

[0047] Step 3: Accurately weigh the raw materials according to the mass proportions, mix the slow-release nitrogen source biochar carrier, monoammonium phosphate, potassium sulfate, polyglutamic acid, humic acid, clay, and attapulgite evenly, and then form them into granules with a particle size of 3 mm through a disc granulator to obtain the core granules of biochar-based slow-release fertilizer.

[0048] Step 4: Obtain a 5% sodium alginate solution (5g sodium alginate dissolved in 100g water); mix the compound microbial agent with the 5% sodium alginate solution, and uniformly cover the granule surface using spray coating technology to form a microbial protective layer, thus obtaining amino-modified biochar-based slow-release fertilizer granules.

[0049] Step 5: The obtained amino-modified biochar-based slow-release fertilizer is dried at 40℃ for 2 hours to solidify the coating, thus obtaining a biochar-based slow-release fertilizer for sandy soil.

[0050] Example 3 A biochar-based slow-release fertilizer specifically for sandy soils: The composition includes 24 parts amino-modified biochar (amino-modified wheat biochar), 9 parts urea, 24 parts urea-formaldehyde, 13 parts monoammonium phosphate, 14 parts potassium sulfate, 0.2 parts polyglutamic acid, 7 parts humic acid, 17 parts clay, 13 parts attapulgite, 18 parts compound microbial inoculant, and 1.8 parts sodium alginate. The compound microbial inoculant is composed of *Haloxylon ammodendron* ACCC 11681, *Bacillus subtilis* ACCC 60429, and *Bacillus mucilaginosus* ACCC 10094 in a viable count ratio of 1:1:2, with a total effective viable count of 3.0 × 10⁻⁶. 9 CFU / g.

[0051] Preparation method: Step 1: Crush wheat straw to a particle size of 3 cm and dry it to a moisture content of 10%; carry out high-temperature pyrolysis under nitrogen protection, carbonize at 500℃ for 3.5 h to generate biochar; impregnate the biochar with 0.5% polyacrylamide solution for modification at 30℃ for 3 h, dry it and pass it through a 20-mesh sieve to obtain amino-modified wheat biochar.

[0052] Step 2: Melt urea and urea-formaldehyde at 140℃, pressurize to 1.0MPa using a high-pressure melt injection device, and inject into the pores of amino-modified wheat biochar. Keep at 140℃ for 30 minutes to form a slow-release nitrogen source biochar carrier.

[0053] Step 3: Accurately weigh the raw materials according to the mass proportions, mix the slow-release nitrogen source biochar carrier, monoammonium phosphate, potassium sulfate, polyglutamic acid, humic acid, clay, and attapulgite evenly, and then form them into granules with a particle size of 3 mm through a disc granulator to obtain the core granules of biochar-based slow-release fertilizer.

[0054] Step 4: Obtain a 5% sodium alginate solution (5g sodium alginate dissolved in 100g water); mix the compound microbial agent with the 5% sodium alginate solution, and uniformly cover the granule surface using spray coating technology to form a microbial protective layer, thus obtaining amino-modified biochar-based slow-release fertilizer granules.

[0055] Step 5: The obtained amino-modified biochar-based slow-release fertilizer is dried at 35°C for 2 hours to solidify the coating, thus obtaining a biochar-based slow-release fertilizer specifically for sandy soil.

[0056] Example 4 A biochar-based slow-release fertilizer specifically for sandy soils: The mixture contains 28 parts amino-modified biochar (amino-modified wheat biochar), 10 parts urea, 23 parts urea-formaldehyde, 14 parts monoammonium phosphate, 18 parts potassium sulfate, 0.2 parts polyglutamic acid, 9 parts humic acid, 19 parts clay, 15 parts attapulgite, 20 parts compound microbial inoculant, and 1.5 parts sodium alginate. The compound microbial inoculant is composed of *Haloxylon ammodendron* ACCC 11681, *Bacillus subtilis* ACCC 60429, and *Bacillus mucilaginosus* ACCC 10094 in a viable count ratio of 1:1:1, with a total effective viable count of 3.0 × 10⁻⁶. 9 CFU / g.

[0057] Preparation method: Step 1: Crush wheat straw to a particle size of 2 cm and dry it to a moisture content of 10%; carry out high-temperature pyrolysis under nitrogen protection, carbonize at 600℃ for 3.5 h to generate biochar; impregnate the biochar with 0.5% polyacrylamide solution for modification, the impregnation temperature is 30℃ for 3 h, and after drying, pass it through a 20-mesh sieve to obtain amino-modified wheat biochar.

[0058] Step 2: Melt urea and urea-formaldehyde at 140℃, pressurize to 1.0MPa using a high-pressure melt injection device, and inject into the pores of amino-modified wheat biochar. Keep at 140℃ for 30 minutes to form a slow-release nitrogen source biochar carrier.

[0059] Step 3: Accurately weigh the raw materials according to the mass proportions, mix the slow-release nitrogen source biochar carrier, monoammonium phosphate, potassium sulfate, polyglutamic acid, humic acid, clay, and attapulgite evenly, and then form them into granules with a particle size of 3 mm through a disc granulator to obtain the core granules of biochar-based slow-release fertilizer.

[0060] Step 4: Obtain a 5% sodium alginate solution (5g sodium alginate dissolved in 100g water); mix the compound microbial agent with the 5% sodium alginate solution, and uniformly cover the granule surface using spray coating technology to form a microbial protective layer, thus obtaining amino-modified biochar-based slow-release fertilizer granules.

[0061] Step 5: The obtained amino-modified biochar-based slow-release fertilizer is dried at 35°C for 2 hours to solidify the coating, thus obtaining a biochar-based slow-release fertilizer specifically for sandy soil.

[0062] Comparative Example 1 A compound fertilizer differs from Example 2 only in that the biochar is not modified, and the amino-modified biochar in step two is replaced with biochar.

[0063] The raw materials are: 27 parts biochar (corn biochar), 6 parts urea, 27 parts urea-formaldehyde, 8 parts monoammonium phosphate, 13 parts potassium sulfate, 0.3 parts polyglutamic acid, 6 parts fulvic acid, 16 parts clay, 14 parts attapulgite, 15 parts compound microbial agent, and 1.0 part sodium alginate; the compound microbial agent is composed of Halomonas ACCC 11681, Bacillus subtilis ACCC 60429, and Bacillus mucilaginosus ACCC 10094 in a viable count ratio of 1:1:2, with a total effective viable count of 4.0 × 10⁻⁶. 9 CFU / g.

[0064] The preparation method is as follows: Step 1: Crush the corn stalks to a particle size of 2cm and dry them to a moisture content of 10%; then carry out high-temperature pyrolysis under nitrogen protection, carbonizing at 450℃ for 4 hours to produce biochar.

[0065] Step 2: Melt urea and urea-formaldehyde at 140℃, pressurize to 0.9MPa using a high-pressure melt injection device, and inject into the pores of biochar. Hold at 140℃ for 25 minutes to form a slow-release nitrogen source biochar carrier.

[0066] Step 3: Same as Example 2.

[0067] Step 4: Same as Example 2.

[0068] Step 5: Same as Example 2.

[0069] Comparative Example 2 A compound fertilizer differs from Example 2 only in that the coating treatment in step four is omitted, i.e., the suspension composed of compound microbial agents and sodium alginate is not used for coating.

[0070] The raw materials are: 27 parts of amino-modified biochar (amino-modified corn biochar), 6 parts of urea, 27 parts of urea-formaldehyde, 8 parts of monoammonium phosphate, 13 parts of potassium sulfate, 0.3 parts of polyglutamic acid, 6 parts of humic acid, 16 parts of clay and 14 parts of attapulgite.

[0071] The preparation method is as follows: Step 1: Same as Example 2.

[0072] Step 2: Same as Example 2.

[0073] Step 3: Same as Example 2.

[0074] Comparative Example 3 A compound fertilizer differs from Example 2 only in that it does not contain amino-modified biochar, that is, it directly discards amino-modified biochar and only uses chemical fertilizers to mix and granulate, and then coats it with a suspension composed of compound microbial agents and sodium alginate.

[0075] The raw materials are: 6 parts urea, 27 parts urea-formaldehyde, 8 parts monoammonium phosphate, 13 parts potassium sulfate, 0.3 parts polyglutamic acid, 6 parts fulvic acid, 16 parts clay, 14 parts attapulgite, 15 parts compound microbial agent, and 1.0 part sodium alginate; the compound microbial agent is composed of Halomonas ACCC 11681, Bacillus subtilis ACCC 60429, and Bacillus mucilaginosus ACCC 10094 in a viable count ratio of 1:1:2, with a total effective viable count of 4.0 × 10⁻⁶. 9 CFU / g.

[0076] The preparation method is as follows: Step 1: Accurately weigh the raw materials according to the mass proportions, and mix urea, urea-formaldehyde, monoammonium phosphate, potassium sulfate, polyglutamic acid, humic acid, clay, and attapulgite evenly. Then, use a disc granulator to form granules with a particle size of 3 mm to obtain the core granules of compound fertilizer.

[0077] Step 2: Obtain a 5% sodium alginate solution (5g sodium alginate dissolved in 100g water); mix the compound microbial agent with the 5% sodium alginate solution, and evenly cover the surface of the core particles of the compound fertilizer using spray coating technology to form a microbial protective layer, thus obtaining a compound fertilizer coated with compound microbial agent and sodium alginate.

[0078] Step 3: Dry the obtained fertilizer at 40℃ for 2 hours to solidify the coating and obtain compound fertilizer.

[0079] Comparative Example 4 A compound fertilizer differs from Example 2 only in that it does not contain urea-formaldehyde, that is, it directly discards urea-formaldehyde and only uses urea to inject into the pores of amino-modified biochar.

[0080] The raw materials are: 27 parts amino-modified biochar (amino-modified corn biochar), 6 parts urea, 27 parts urea-formaldehyde, 8 parts monoammonium phosphate, 13 parts potassium sulfate, 0.3 parts polyglutamic acid, 6 parts humic acid, 16 parts clay, 14 parts attapulgite, 15 parts compound microbial agent, and 1.0 part sodium alginate; the compound microbial agent is composed of Halomonas ACCC 11681, Bacillus subtilis ACCC 60429, and Bacillus mucilaginosus ACCC 10094 in a viable count ratio of 1:1:2, with a total effective viable count of 4.0 × 10⁻⁶. 9 CFU / g.

[0081] The preparation method is as follows: Step 1: Same as Example 2.

[0082] Step 2: Melt urea at 140℃, pressurize it to 0.9MPa using a high-pressure melt injection device, and inject it into the pores of amino-modified corn biochar. Keep it at 140℃ for 25 minutes to form a slow-release nitrogen source biochar carrier.

[0083] Step 3: Accurately weigh the raw materials according to the mass proportions, and mix the slow-release nitrogen source biochar carrier, urea formaldehyde, monoammonium phosphate, potassium sulfate, polyglutamic acid, humic acid, clay, and attapulgite evenly. Then, use a disc granulator to form particles with a particle size of 3 mm to obtain the core particles of biochar-based slow-release fertilizer.

[0084] Step 4: Same as Example 2.

[0085] Step 5: Same as Example 2.

[0086] Comparative Example 5 A compound fertilizer differs from Example 2 only in that it does not contain urea; that is, it directly discards urea and only injects urea-formaldehyde into the pores of amino-modified biochar.

[0087] The raw materials are: 27 parts amino-modified biochar (amino-modified corn biochar), 6 parts urea, 27 parts urea-formaldehyde, 8 parts monoammonium phosphate, 13 parts potassium sulfate, 0.3 parts polyglutamic acid, 6 parts humic acid, 16 parts clay, 14 parts attapulgite, 15 parts compound microbial agent, and 1.0 part sodium alginate; the compound microbial agent is composed of Halomonas ACCC 11681, Bacillus subtilis ACCC 60429, and Bacillus mucilaginosus ACCC 10094 in a viable count ratio of 1:1:2, with a total effective viable count of 4.0 × 10⁻⁶. 9 CFU / g.

[0088] The preparation method is as follows: Step 1: Same as Example 2.

[0089] Step 2: Melt urea-formaldehyde at 140℃, pressurize it to 0.9MPa using a high-pressure melt injection device, and inject it into the pores of amino-modified corn biochar. Keep it at 140℃ for 25 minutes to form a slow-release nitrogen source biochar carrier.

[0090] Step 3: Accurately weigh the raw materials according to the mass proportions, and mix the slow-release nitrogen source biochar carrier, urea, monoammonium phosphate, potassium sulfate, polyglutamic acid, humic acid, clay, and attapulgite evenly. Then, use a disc granulator to form particles with a particle size of 3 mm to obtain the core particles of biochar-based slow-release fertilizer.

[0091] Step 4: Same as Example 2.

[0092] Step 5: Same as Example 2.

[0093] Comparative Example 6 A compound fertilizer differs from Example 2 only in that the Halomonas ACCC 116 in the compound microbial agent is replaced with Bacillus coagulans ACCC 00403 (a publicly disclosed strain purchased from the China Agricultural Microbial Culture Collection Center).

[0094] The raw materials are: 27 parts amino-modified biochar (amino-modified corn biochar), 6 parts urea, 27 parts urea-formaldehyde, 8 parts monoammonium phosphate, 13 parts potassium sulfate, 0.3 parts polyglutamic acid, 6 parts humic acid, 16 parts clay, 14 parts attapulgite, 15 parts compound microbial inoculant, and 1.0 part sodium alginate; the compound microbial inoculant is composed of Bacillus coagulans SICC 1.938, Bacillus subtilis ACCC 60429, and Bacillus mucilaginosus ACCC 10094 in a viable count ratio of 1:1:2, with a total effective viable count of 4.0 × 10⁻⁶. 9 CFU / g.

[0095] The preparation method is the same as in Example 2.

[0096] Comparative Example 7 A slow-release fertilizer polyolefin-coated urea produced by Maoshi Agricultural Technology Co., Ltd. was directly mixed with the same amount of monoammonium phosphate, potassium sulfate, polyglutamic acid, humic acid, clay, and attapulgite as in Example 2 to obtain a compound fertilizer.

[0097] The raw materials are: 25 parts of slow-release fertilizer polyolefin-coated urea, 8 parts of monoammonium phosphate, 13 parts of potassium sulfate, 0.3 parts of polyglutamic acid, 6 parts of humic acid, 16 parts of clay and 14 parts of attapulgite.

[0098] The preparation method is as follows: accurately weigh the raw materials according to the mass fraction, mix the slow-release fertilizer polyolefin-coated urea, monoammonium phosphate, potassium sulfate, polyglutamic acid, humic acid, clay, and attapulgite evenly, and then form them into particles with a particle size of 3 mm through a disc granulator to obtain the core particles of biochar-based slow-release fertilizer.

[0099] Test case Sandy soils from Dongying City, Shandong Province (soil physicochemical properties: pH 7.14, organic matter 10.24 g / kg, available nitrogen 33.5 mg / kg, available phosphorus 18.12 mg / kg, available potassium 105.85 mg / kg) were selected to test the effects of fertilizers prepared in Examples 1-4 and Comparative Examples 1-7 on the growth of wheat variety Lunxuan 145 throughout its entire growth period. The experimental area was divided into groups of 0.5 mu each, with each group receiving fertilizers corresponding to Examples 1-4 and Comparative Examples 1-7, respectively. The groups were labeled as Example 1, Example 2, Example 3, Example 4, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, Comparative Example 5, Comparative Example 6, and Comparative Example 7. The fertilizer application rate was 50 kg / mu. The experiment was conducted from September 2024 to May 2025, and the soil physicochemical properties and wheat yield indicators were measured.

[0100] The physicochemical properties of the amino-modified biochar in Example 2 and the biochar in Comparative Example 1 are compared, as shown in Table 1.

[0101] Table 1. Physicochemical properties of amino-modified biochar and biochar

[0102] The results showed that the amino-modified biochar prepared in the embodiments of the present invention had improved specific surface area, average pore size, CEC, total nitrogen content, and total biochar content.

[0103] The main indicators of soil, including soil aggregate index, soil bulk density, soil porosity, soil moisture content, and soil infiltration parameters, were tested using in-situ field observation, indoor sample testing, and mathematical statistical analysis. The improvement effects of different treatment measures on sandy soils along the Yellow River were compared and analyzed. The results are shown in Table 2.

[0104] Table 2 Effects of different treatments on soil physicochemical properties

[0105] The results showed that, compared with the comparative example, the biochar-based slow-release fertilizer for sandy soil prepared in the embodiments of the present invention significantly improved the surface aggregate PAD index, porosity and soil water storage capacity of sandy soil.

[0106] Table 3. Effects of different treatments on wheat yield indicators

[0107] The results showed that, compared with the comparative example, wheat yield was significantly increased after applying the biochar-based slow-release fertilizer for sandy soil prepared in the embodiments of the present invention.

[0108] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A biochar-based slow-release fertilizer specifically for sandy soils, characterized in that, By weight, it comprises: 22-30 parts of amino-modified biochar, 5-10 parts of urea, 20-28 parts of urea-formaldehyde, 8-15 parts of monoammonium phosphate, 12-20 parts of potassium sulfate, 0.2-0.3 parts of polyglutamic acid, 5-10 parts of humic acid, 15-20 parts of clay, 12-15 parts of attapulgite, 15-20 parts of compound microbial agent, and 0.5-1.5 parts of sodium alginate; the compound microbial agent is composed of Halomonas ACCC 11681, Bacillus subtilis ACCC 60429, and Bacillus mucilaginosus ACCC 10094 in a viable count ratio of 1:1:(1-3).

2. The biochar-based slow-release fertilizer for sandy soil according to claim 1, characterized in that, The effective viable count of the compound microbial agent is ≥2.0×10⁻⁶. 9 CFU / g.

3. The biochar-based slow-release fertilizer for sandy soil according to claim 1, characterized in that, The preparation method of the amino-modified biochar includes: impregnating crop straw biochar with 0.5% polyacrylamide solution and then grinding it through a 20-mesh sieve; the impregnation temperature is 25~35℃ and the time is 2~4h.

4. The biochar-based slow-release fertilizer for sandy soil according to claim 3, characterized in that, The crop straw biochar includes any one or more of wheat straw biochar and corn straw biochar.

5. The biochar-based slow-release fertilizer for sandy soil according to claim 4, characterized in that, The method for preparing crop straw biochar includes: drying crop straw and then crushing it to a particle size of 2-3 cm for high-temperature pyrolysis carbonization, wherein the carbonization temperature is 400-600℃ and the time is 3-4 h.

6. The method for preparing the biochar-based slow-release fertilizer for sandy soil according to any one of claims 1 to 5, characterized in that, Includes the following steps: Urea and urea-formaldehyde are melted and mixed, then injected under pressure into the pores of amino-modified biochar and kept warm to complete the loading. Then, it is mixed evenly with monoammonium phosphate, potassium sulfate, polyglutamic acid, humic acid, clay, and attapulgite, and granulated. A mixed solution of composite microbial agent and sodium alginate is sprayed onto the surface of the granules, and then dried to obtain a biochar-based slow-release fertilizer for sandy soil.

7. The preparation method according to claim 6, characterized in that, The pressurization pressure is 0.8~1.0 MPa, the heat preservation temperature is 135~145℃, and the time is 20~30 min.

8. The preparation method according to claim 6, characterized in that, The method for preparing the mixed solution includes: dissolving sodium alginate in water to obtain a 5% sodium alginate solution; and mixing the compound microbial agent with the 5% sodium alginate solution to obtain the mixed solution.

9. The preparation method according to claim 6, characterized in that, The drying temperature is 30~40℃ and the time is 1~2 hours.

10. The application of the biochar-based slow-release fertilizer for sandy soil as described in any one of claims 1 to 5 in the cultivation of corn and wheat in sandy soil.

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