A biochar composite amendment for soil structure improvement and a preparation method thereof

Abstract

The application relates to the technical field of soil improvement, in particular to a biochar composite improver for soil structure improvement and a preparation method thereof. The biochar composite improver for soil structure improvement is obtained by sequentially wrapping monomer A solution, monomer B solution and monomer C solution on the surface of biochar powder and then polymerizing; the monomer A solution is prepared from acrylamide, triallyl isocyanurate, acrylic acid, sodium hydroxide and deionized water; the monomer B solution is prepared from acrylamide, N,N'-methylene bisacrylamide, acrylic acid, sodium hydroxide and deionized water; and the monomer C solution is prepared from acrylamide, methacryloyloxyethyl trimethyl ammonium chloride and deionized water; the biochar composite improver for soil structure improvement provided by the application solves the problems of loose sandy soil and poor water retention capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of soil improvement, and in particular to a biochar composite improver for improving soil structure and a preparation method thereof. Background Art

[0002] Aeolian sandy soil is a typical loose, easily flowing soil type found in arid and semi-arid regions. This soil is typically composed of fine sand particles and lacks organic matter and clay, resulting in an extremely loose structure and poor stability, making it susceptible to wind and water erosion. Due to the weak bonding between its particles, aeolian sandy soil is easily dispersed by strong winds, causing natural disasters such as sandstorms, posing a serious threat to the ecological environment and human activities.

[0003] Furthermore, the infertile nature of aeolian sandy soils also limits their agricultural value. Due to their low organic matter content, aeolian sandy soils often lack the necessary nutrients to support normal crop growth. Furthermore, their poor water-holding capacity means they are prone to water loss, leading to severe soil aridification. After rainfall, water from such soils quickly permeates or evaporates, preventing them from providing a continuous water supply to plants, further exacerbating the challenges of crop growth. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to propose a biochar composite improver for soil structure improvement and a preparation method thereof, so as to solve the problem that sandy soil has poor water holding capacity, loose structure and easy flow.

[0005] Based on the above purpose, the present invention provides a biochar composite improver for improving soil structure, which is obtained by sequentially coating and polymerizing monomer A solution, monomer B solution and monomer C solution on the surface of biochar powder.

[0006] Furthermore, the weight ratio of the monomer A solution, monomer B solution, monomer C solution and biochar powder is 62-88:18-32:12-26:3-8.

[0007] Furthermore, the preparation method of the monomer A solution is as follows: by weight, 4-6 parts of acrylamide, 0.1-0.2 parts of triallyl isocyanurate, and 8-12 parts of acrylic acid are added to 50-70 parts of deionized water, stirred for 20-40 minutes, and adjusted to pH 8-9 with sodium hydroxide to obtain a monomer A solution.

[0008] Furthermore, the preparation method of the monomer B solution is as follows: 2-4 parts of acrylamide, 0.03-0.07 parts of N,N′-methylenebisacrylamide, and 1-3 parts of acrylic acid are dissolved in 15-25 parts of deionized water by weight, stirred for 10-30 minutes, and adjusted to pH 8-9 with sodium hydroxide to obtain a monomer B solution.

[0009] Furthermore, the preparation method of the monomer C solution is as follows: 0.5-2 parts of acrylamide and 2-4 parts of methacryloyloxyethyltrimethylammonium chloride are added to 10-20 parts of deionized water by weight, and stirred for 5-20 minutes to obtain the monomer C solution.

[0010] Preferably, the biochar powder is prepared as follows: drying corn stalks, grinding them through a 60-mesh sieve, pyrolyzing them, crushing and grinding them through a 200-mesh sieve, washing them with water, and drying them to obtain biochar powder.

[0011] Preferably, the pyrolysis temperature is 450-550° C. and the time is 1.5-2.5 h.

[0012] Furthermore, the present invention also provides a method for preparing a biochar composite improver for soil structure improvement, comprising the following steps: adding biochar powder to deionized water, ultrasonicating for 10-30 minutes, then passing nitrogen for 20-40 minutes, heating to 65-75°C, adding ammonium persulfate, stirring for 20-40 minutes, then dropping monomer A solution, continuing to stir for 1.5-2.5 hours after the addition is complete, then adding ammonium persulfate, stirring for 5-15 minutes, then dropping monomer B solution, continuing to stir for 2-4 hours after the addition is complete, then adding ammonium persulfate, stirring for 5-15 minutes, then dropping monomer C solution, continuing to stir for 4-6 hours after the addition is complete, washing with water, standing for 20-30 hours, vacuum drying for 5-7 hours, and grinding through an 80-120 mesh sieve to obtain a biochar composite improver for soil structure improvement.

[0013] Preferably, the amount of deionized water added is 8-12 times the weight of the biochar powder.

[0014] Preferably, the amount of ammonium persulfate added is 0.5%-2% of the total weight of the monomers in the monomer A solution, the monomer B solution, and the monomer C solution.

[0015] Beneficial effects of the present invention:

[0016] The present invention provides a biochar composite improver for soil structure improvement. By combining monomers with different functions and biochar, it significantly improves the physical properties of sandy soil. In the improver, the high-crosslinked density coating composed of monomer A significantly increases the saturated moisture content of the soil due to its abundant hydrophilic groups and fine pores. The low-crosslinked density coating composed of monomer B optimizes the dynamic transfer of water in the soil through the gradient suction formed with monomer A, enhancing soil water retention and providing crops with the most readily available water. Furthermore, the hydrophilic molecular chain structure of monomer C effectively improves crop water utilization efficiency by regulating water absorption.

[0017] The hierarchical structure of the amendments also proved crucial. The sequential addition of monomers A, B, and C formed a coating that effectively improved the structure of the aeolian sandy soil, significantly increasing the number of aggregates larger than 0.25 nm and forming water-stable macroaggregates. These aggregates not only stabilized the soil structure and improved soil permeability, but also prevented the formation of topsoil crusts.

[0018] Therefore, this biochar composite amendment not only solves the problems of loose texture and poor water holding capacity of sandy soil, but also provides more optimized moisture and environmental conditions for crop growth, thereby supporting higher crop yields and healthy growth. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0020] Example 1:

[0021] (1) 20 g of corn straw was dried, ground through a 60-mesh sieve, pyrolyzed at 450 °C for 2.5 h, crushed and ground through a 200-mesh sieve, washed with deionized water to remove ash and other impurities, and finally dried at 80 °C for 12 h to obtain biochar powder;

[0022] (2) 4 g of acrylamide, 0.1 g of triallyl isocyanurate, and 8 g of acrylic acid were added to 50 g of deionized water, stirred for 20 min, and the pH was adjusted to 8.1 with sodium hydroxide to obtain a monomer A solution;

[0023] (3) Dissolve 2 g of acrylamide, 0.03 N,N′-methylenebisacrylamide, and 1 g of acrylic acid in 15 g of deionized water, stir for 10 min, and adjust the pH to 8.2 with sodium hydroxide to obtain a monomer B solution;

[0024] (4) Add 0.5 g of acrylamide and 2 g of methacryloyloxyethyltrimethylammonium chloride to 10 g of deionized water and stir for 5 min to obtain a monomer C solution;

[0025] (5) 3 g of biochar powder was added to 24 g of deionized water, ultrasonicated for 10 min, and then nitrogen was passed through for 20 min. The temperature was raised to 65 ° C, 0.12 g of ammonium persulfate was added, and the mixture was stirred for 20 min. Then 62 g of monomer A solution was added dropwise. After the addition was completed, stirring was continued for 1.5 h. Then 0.03 g of ammonium persulfate was added, and the mixture was stirred for 5 min. Then 18 g of monomer B solution was added dropwise. After the addition was completed, stirring was continued for 2 h. Then 0.02 g of ammonium persulfate was added, and the mixture was stirred for 5 min. Then 12 g of monomer C solution was added dropwise. After the addition was completed, stirring was continued for 4 h. Finally, the unreacted monomer was washed away with deionized water, allowed to stand for 20 h, vacuum dried for 5 h, and ground through a 100 mesh sieve to obtain a biochar composite improver for soil structure improvement.

[0026] Example 2:

[0027] (1) 20 g of corn straw was dried, ground through a 60-mesh sieve, pyrolyzed at 500 °C for 2 h, crushed and ground through a 200-mesh sieve, washed with deionized water to remove ash and other impurities, and finally dried at 80 °C for 12 h to obtain biochar powder;

[0028] (2) 5 g of acrylamide, 0.15 g of triallyl isocyanurate, and 10 g of acrylic acid were added to 60 g of deionized water, stirred for 30 min, and the pH was adjusted to 8.5 with sodium hydroxide to obtain a monomer A solution;

[0029] (3) 3 g of acrylamide, 0.05 N,N′-methylenebisacrylamide, and 2 g of acrylic acid were dissolved in 20 g of deionized water, stirred for 20 min, and the pH was adjusted to 8.5 with sodium hydroxide to obtain a monomer B solution;

[0030] (4) 1 g of acrylamide and 3 g of methacryloyloxyethyl trimethylammonium chloride were added to 16 g of deionized water and stirred for 10 min to obtain a monomer C solution;

[0031] (5) 5 g of biochar powder was added to 50 g of deionized water, ultrasonicated for 20 min, and then nitrogen was introduced for 30 min. The temperature was raised to 70 °C, 0.15 g of ammonium persulfate was added, and the mixture was stirred for 30 min. Then 75 g of monomer A solution was added dropwise. After the addition was completed, the stirring was continued for 2 h. Then 0.05 g of ammonium persulfate was added, and the stirring was continued for 10 min. Then 25 g of monomer B solution was added dropwise. After the addition was completed, the stirring was continued for 3 h. Then 0.04 g of ammonium persulfate was added, and the stirring was continued for 10 min. Then 20 g of monomer C solution was added dropwise. After the addition was completed, the unreacted monomer was washed away with deionized water, allowed to stand for 24 h, vacuum dried for 6 h, and ground through a 100 mesh sieve to obtain a biochar composite improver for soil structure improvement.

[0032] Example 3:

[0033] (1) 20 g of corn straw was dried, ground through a 60-mesh sieve, pyrolyzed at 550 °C for 1.5 h, crushed and ground through a 200-mesh sieve, washed with deionized water to remove ash and other impurities, and finally dried at 80 °C for 12 h to obtain biochar powder;

[0034] (2) 6 g of acrylamide, 0.2 g of triallyl isocyanurate, and 12 g of acrylic acid were added to 70 g of deionized water, stirred for 40 min, and the pH was adjusted to 8.58 with sodium hydroxide to obtain a monomer A solution;

[0035] (3) 4 g of acrylamide, 0.07 N,N′-methylenebisacrylamide, and 3 g of acrylic acid were dissolved in 25 g of deionized water, stirred for 30 min, and the pH was adjusted to 8.7 with sodium hydroxide to obtain a monomer B solution;

[0036] (4) Add 2 g of acrylamide and 4 g of methacryloyloxyethyltrimethylammonium chloride to 20 g of deionized water and stir for 20 min to obtain a monomer C solution;

[0037] (5) 8 g of biochar powder was added to 96 g of deionized water, ultrasonicated for 30 min, and then nitrogen was introduced for 40 min. The temperature was raised to 75 °C, 0.18 g of ammonium persulfate was added, and the mixture was stirred for 40 min. Then 88 g of monomer A solution was added dropwise. After the addition was completed, the stirring was continued for 2.5 h. Then 0.07 g of ammonium persulfate was added, and the stirring was continued for 15 min. Then 32 g of monomer B solution was added dropwise. After the addition was completed, the stirring was continued for 4 h. Then 0.06 g of ammonium persulfate was added, and the stirring was continued for 15 min. Then 26 g of monomer C solution was added dropwise. After the addition was completed, the unreacted monomer was washed away with deionized water, allowed to stand for 30 h, vacuum dried for 7 h, and ground through a 100 mesh sieve to obtain a biochar composite improver for soil structure improvement.

[0038] Comparative Example 1:

[0039] The difference between Comparative Example 1 and Example 2 is that: Monomer A solution was not added dropwise;

[0040] The specific steps are as follows:

[0041] (1) 20 g of corn straw was dried, ground through a 60-mesh sieve, pyrolyzed at 500 °C for 2 h, crushed and ground through a 200-mesh sieve, washed with deionized water to remove ash and other impurities, and finally dried at 80 °C for 12 h to obtain biochar powder;

[0042] (2) 3 g of acrylamide, 0.05 N,N′-methylenebisacrylamide, and 2 g of acrylic acid were dissolved in 20 g of deionized water, stirred for 20 min, and the pH was adjusted to 8.5 with sodium hydroxide to obtain a monomer B solution;

[0043] (3) 1 g of acrylamide and 3 g of methacryloyloxyethyltrimethylammonium chloride were added to 16 g of deionized water and stirred for 10 min to obtain a monomer C solution;

[0044] (4) Add 5 g of biochar powder to 50 g of deionized water, ultrasonicate for 20 min, and then flow nitrogen for 30 min. Then heat to 70 °C, add 0.05 g of ammonium persulfate, stir for 10 min, and then drop 25 g of monomer B solution. After the addition is complete, continue stirring for 3 h. Then add 0.04 g of ammonium persulfate, stir for 10 min, and then drop 20 g of monomer C solution. After the addition is complete, continue stirring for 5 h. Finally, wash away the unreacted monomer with deionized water, let it stand for 24 h, vacuum dry for 6 h, and grind through a 100 mesh sieve to obtain an improver.

[0045] Comparative Example 2:

[0046] The difference between Comparative Example 2 and Example 2 is that: the monomer B solution is not added dropwise;

[0047] The specific steps are as follows:

[0048] (1) 20 g of corn straw was dried, ground through a 60-mesh sieve, pyrolyzed at 500 °C for 2 h, crushed and ground through a 200-mesh sieve, washed with deionized water to remove ash and other impurities, and finally dried at 80 °C for 12 h to obtain biochar powder;

[0049] (2) 5 g of acrylamide, 0.15 g of triallyl isocyanurate, and 10 g of acrylic acid were added to 60 g of deionized water, stirred for 30 min, and the pH was adjusted to 8.5 with sodium hydroxide to obtain a monomer A solution;

[0050] (3) 1 g of acrylamide and 3 g of methacryloyloxyethyltrimethylammonium chloride were added to 16 g of deionized water and stirred for 10 min to obtain a monomer C solution;

[0051] (4) Add 5 g of biochar powder to 50 g of deionized water, ultrasonicate for 20 min, and then pass nitrogen for 30 min. Then heat to 70 °C, add 0.15 g of ammonium persulfate, stir for 30 min, then add 75 g of monomer A solution dropwise, continue stirring for 2 h after the addition is complete, then add 0.04 g of ammonium persulfate, stir for 10 min, then add 20 g of monomer C solution dropwise, continue stirring for 5 h after the addition is complete, finally wash away the unreacted monomer with deionized water, let stand for 24 h, vacuum dry for 6 h, grind through a 100 mesh sieve to obtain an improver.

[0052] Comparative Example 3:

[0053] The difference between Comparative Example 3 and Example 2 is that: the monomer C solution is not added dropwise;

[0054] The specific steps are as follows:

[0055] (1) 20 g of corn straw was dried, ground through a 60-mesh sieve, pyrolyzed at 500 °C for 2 h, crushed and ground through a 200-mesh sieve, washed with deionized water to remove ash and other impurities, and finally dried at 80 °C for 12 h to obtain biochar powder;

[0056] (2) 5 g of acrylamide, 0.15 g of triallyl isocyanurate, and 10 g of acrylic acid were added to 60 g of deionized water, stirred for 30 min, and the pH was adjusted to 8.5 with sodium hydroxide to obtain a monomer A solution;

[0057] (3) 3 g of acrylamide, 0.05 N,N′-methylenebisacrylamide, and 2 g of acrylic acid were dissolved in 20 g of deionized water, stirred for 20 min, and the pH was adjusted to 8.5 with sodium hydroxide to obtain a monomer B solution;

[0058] (4) Add 5 g of biochar powder to 50 g of deionized water, ultrasonicate for 20 min, and then pass nitrogen for 30 min. Then heat to 70 °C, add 0.15 g of ammonium persulfate, stir for 30 min, then add 75 g of monomer A solution dropwise, continue stirring for 2 h after the addition is complete, then add 0.05 g of ammonium persulfate, stir for 10 min, then add 25 g of monomer B solution dropwise, continue stirring for 3 h after the addition is complete, finally wash away the unreacted monomer with deionized water, let stand for 24 h, vacuum dry for 6 h, grind through a 100 mesh sieve to obtain an improver.

[0059] Comparative Example 4:

[0060] The difference between Comparative Example 4 and Example 2 is that the monomer C solution is added dropwise first, then the monomer B solution is added dropwise, and finally the monomer A solution is added dropwise.

[0061] The specific steps are as follows:

[0062] (1) 20 g of corn straw was dried, ground through a 60-mesh sieve, pyrolyzed at 500 °C for 2 h, crushed and ground through a 200-mesh sieve, washed with deionized water to remove ash and other impurities, and finally dried at 80 °C for 12 h to obtain biochar powder;

[0063] (2) 5 g of acrylamide, 0.15 g of triallyl isocyanurate, and 10 g of acrylic acid were added to 60 g of deionized water, stirred for 30 min, and the pH was adjusted to 8.5 with sodium hydroxide to obtain a monomer A solution;

[0064] (3) 3 g of acrylamide, 0.05 N,N′-methylenebisacrylamide, and 2 g of acrylic acid were dissolved in 20 g of deionized water, stirred for 20 min, and the pH was adjusted to 8.5 with sodium hydroxide to obtain a monomer B solution;

[0065] (4) 1 g of acrylamide and 3 g of methacryloyloxyethyl trimethylammonium chloride were added to 16 g of deionized water and stirred for 10 min to obtain a monomer C solution;

[0066] (5) Add 5 g of biochar powder to 50 g of deionized water, ultrasonicate for 20 min, and then pass nitrogen for 30 min. Then heat to 70 °C, add 0.04 g of ammonium persulfate, stir for 10 min, then add 20 g of monomer C solution dropwise, continue stirring for 5 h after the addition is complete, then add 0.05 g of ammonium persulfate, stir for 10 min, then add 25 g of monomer B solution dropwise, continue stirring for 3 h after the addition is complete, then add 0.15 g of ammonium persulfate, stir for 30 min, then add 75 g of monomer A solution dropwise, continue stirring for 2 h after the addition is complete, finally wash away the unreacted monomer with deionized water, let stand for 24 h, vacuum dry for 6 h, grind through a 100 mesh sieve to obtain an improver.

[0067] Performance testing:

[0068] Water holding performance test: 2 kg of dried sandy soil was mixed with 2 g of the improver prepared in the examples and comparative examples at a pressure of 1.1 g / cm 3 The bulk density was placed in pots, and each treatment was repeated 3 times. After applying the water retaining agent, the mixture was mixed and inserted into the water tensiometer. Water was added to reach the saturated moisture content. The soil was placed outdoors to dry naturally. The soil water potential measured by the tensiometer was recorded at 8:00 every day, and the corresponding soil moisture content was measured by weighing method. Sufficient water was added to the soil to reach saturation, and the soil saturated moisture content was measured. Under natural conditions, soil moisture continued to evaporate. When the soil water suction reached 80kPa, the soil moisture content was measured, and the difference in soil moisture between the two was calculated. This value is the moisture content in the soil that is most easily utilized by crops. The results are shown in Table 1.

[0069] Water-stable aggregate property test: The samples that had undergone the water-holding performance test were placed outdoors for 1 month, and the particle size distribution of soil-stable aggregates was determined by mechanical screening. The results are shown in Table 2.

[0070] Table 1 Water holding performance test results

[0071]

[0072] Note: The blank group was without adding modifier.

[0073] Data Analysis:

[0074] From the data of Examples 1-3 and the blank group in Table 1, it can be seen that the biochar composite amendment for soil structure improvement prepared by the present invention can significantly increase the saturated moisture content of sandy soil and the water most easily utilized by crops, which shows that the amendment has great potential in improving soil physical properties, especially for sandy soil with loose texture and poor water holding capacity.

[0075] It can be seen from the data of Example 2 and Comparative Example 1 in Table 1 that the high cross-linking density coating layer composed of monomer A can significantly increase the saturated moisture content of aeolian sandy soil. This is mainly because the high cross-linking density coating layer composed of monomer A contains a large number of hydrophilic groups and abundant fine pores.

[0076] It can be seen from the data of Example 2 and Comparative Example 2 in Table 1 that the low cross-linking density wrapping layer composed of monomer B can effectively increase the saturated moisture content of sandy soil and the moisture most easily utilized by crops. This is mainly because the low cross-linking density wrapping layer composed of monomer B can form a gradient suction with the high cross-linking density wrapping layer composed of monomer A, which is beneficial to transfer moisture to the internal pores. In addition, the low cross-linking density wrapping layer composed of monomer B with appropriate moisture absorption is beneficial to provide moisture that is most easily utilized by crops.

[0077] From the data of Example 2 and Comparative Example 3 in Table 1, it can be seen that the molecular chain composed of monomer C significantly increases the water most easily utilized by crops, which is mainly because the hydrophilic molecular chain helps to regulate water absorption.

[0078] From the data of Example 2 and Comparative Example 4 in Table 1, it can be seen that the order of adding monomers A, B, and C, that is, the structure of the coating layer, has a significant impact on the saturated moisture content of sandy soil and the water most easily utilized by crops.

[0079] Table 2 Properties of water-stable aggregates

[0080]

[0081] Data Analysis:

[0082] From the data of Examples 1-3 and the blank group in Table 2, it can be seen that the biochar composite amendment for soil structure improvement prepared by the present invention can effectively improve the soil structure of sandy soil and significantly increase the number of aggregates >0.25 nm. The formation of large aggregates in the soil helps to stabilize the soil structure, improve soil permeability, and prevent the formation of topsoil crust.

[0083] From the data of Example 1 and Comparative Examples 3 and 4 in Table 2, it can be seen that the molecular chain structure constructed by monomer C in the outer layer of the modifier helps to increase the number of water-stable large aggregates, which is mainly due to the adsorption and entanglement effect of the molecular chain.

[0084] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A biochar composite improver for soil structure improvement, characterized in that: The monomer A solution, monomer B solution and monomer C solution are sequentially coated and polymerized on the surface of biochar powder; The weight ratio of the monomer A solution, monomer B solution, monomer C solution and biochar powder is 62-88:18-32:12-26:3-8; The monomer A solution is prepared as follows: by weight, 4-6 parts of acrylamide, 0.1-0.2 parts of triallyl isocyanurate, and 8-12 parts of acrylic acid are added to 50-70 parts of deionized water, stirred for 20-40 minutes, and the pH is adjusted to 8-9 with sodium hydroxide to obtain a monomer A solution; The monomer B solution is prepared as follows: by weight, 2-4 parts of acrylamide, 0.03-0.07 parts of N,N′-methylenebisacrylamide, and 1-3 parts of acrylic acid are dissolved in 15-25 parts of deionized water, stirred for 10-30 minutes, and the pH is adjusted to 8-9 with sodium hydroxide to obtain a monomer B solution; The preparation method of the monomer C solution is as follows: 0.5-2 parts of acrylamide and 2-4 parts of methacryloyloxyethyltrimethylammonium chloride are added to 10-20 parts of deionized water by weight, and stirred for 5-20 minutes to obtain the monomer C solution.

2. The biochar composite improver for soil structure improvement according to claim 1, characterized in that: The preparation method of the biochar powder is as follows: drying corn stalks, grinding them through a 60-mesh sieve, pyrolyzing them, crushing and grinding them through a 200-mesh sieve, washing them with water, and drying them to obtain the biochar powder.

3. The biochar composite improver for soil structure improvement according to claim 2, characterized in that: The pyrolysis temperature is 450-550° C., and the pyrolysis time is 1.5-2.5 hours.

4. A method for preparing a biochar composite improver for soil structure improvement according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: adding biochar powder into deionized water, ultrasonicating for 10-30 minutes, passing nitrogen for 20-40 minutes, heating to 65-75°C, adding ammonium persulfate, stirring for 20-40 minutes, dripping a monomer A solution, continuing to stir for 1.5-2.5 hours after the dripping is completed, adding ammonium persulfate, stirring for 5-15 minutes, dripping a monomer B solution, continuing to stir for 2-4 hours after the dripping is completed, adding ammonium persulfate, stirring for 5-15 minutes, dripping a monomer C solution, continuing to stir for 4-6 hours after the dripping is completed, washing with water, standing for 20-30 hours, vacuum drying for 5-7 hours, grinding and passing through an 80-120 mesh sieve to obtain a biochar composite improver for soil structure improvement.

5. The method for preparing the biochar composite improver for soil structure improvement according to claim 4, characterized in that: The amount of deionized water added is 8-12 times the weight of the biochar powder.

6. The method for preparing the biochar composite improver for soil structure improvement according to claim 4, characterized in that: The amount of ammonium persulfate added is 0.5%-2% of the total weight of the monomers in the monomer A solution, the monomer B solution, and the monomer C solution.

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