Biochar composite modifier for soil structure improvement and preparation method thereof

Abstract

The invention relates to the technical field of soil improvement, in particular to a biochar composite modifier for improving a soil structure and a preparation method of the biochar composite modifier. The biochar composite modifier for improving the soil structure is obtained by sequentially wrapping and polymerizing a monomer A solution, a monomer B solution and a monomer C solution on the surface of biochar powder, 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; the monomer C solution is prepared from acrylamide, methacryloyloxyethyl trimethyl ammonium chloride and deionized water; the biochar composite modifier for improving the soil structure solves the problems that sandy soil is loose and poor in water holding 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 and easy-flowing soil type widely distributed in arid and semi-arid areas. This soil is usually composed of fine sand particles and lacks organic matter and clay components, resulting in an extremely loose structure, poor stability, and easy to be affected by wind and water erosion. Due to the weak binding force between its particles, aeolian sandy soil is easily blown away by strong winds, forming natural disasters such as sandstorms, posing a serious threat to the ecological environment and human activities.

[0003] In addition, the barren nature of sandy soil also limits its agricultural value. Due to its low organic matter content, sandy soil usually lacks the necessary nutrient supply and is difficult to support the normal growth of crops. At the same time, its water holding capacity is poor and water is easily lost, leading to serious soil aridification problems. After rainfall, water in this soil quickly infiltrates or evaporates, making it impossible to provide plants with a continuous water supply, further exacerbating the difficulty of crop growth. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide 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 and loose and easy flow structure.

[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 a monomer A solution, a monomer B solution and a monomer C solution on the surface of a biochar powder.

[0006] Furthermore, the weight ratio of the monomer A solution, the monomer B solution, the monomer C solution and the 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 the pH is adjusted to 8-9 with sodium hydroxide to obtain a monomer A solution.

[0008] Furthermore, the preparation method of the monomer B solution is 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.

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

[0010] Preferably, the preparation method of the biochar powder is as follows: drying corn stalks, grinding through a 60-mesh sieve, pyrolyzing, crushing and grinding through a 200-mesh sieve, washing with water, and drying 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 improving soil structure, comprising the following steps: adding biochar powder to 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, then dripping monomer A solution, continuing to stir for 1.5-2.5 hours after the dripping is complete, then adding ammonium persulfate, stirring for 5-15 minutes, then dripping monomer B solution, continuing to stir for 2-4 hours after the dripping is complete, then adding ammonium persulfate, stirring for 5-15 minutes, then dripping monomer C solution, continuing to stir for 4-6 hours after the dripping is complete, washing with water, standing for 20-30 hours, vacuum drying for 5-7 hours, grinding through an 80-120 mesh sieve to obtain a biochar composite improver for improving soil structure.

[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, which significantly improves the physical properties of sandy soil by combining monomers with different functions and biochar. In the improver, the high cross-linking density coating layer composed of monomer A greatly improves the saturated moisture content of the soil due to its rich hydrophilic groups and fine pores; the low cross-linking density coating layer composed of monomer B optimizes the dynamic transfer of water in the soil through the gradient suction formed with monomer A, enhances the water holding capacity of the soil, and provides the most easily usable water for crops; in addition, the hydrophilic molecular chain structure of monomer C effectively improves the efficiency of crop water utilization by adjusting the water suction.

[0017] The hierarchical structure of the modifier also shows an extremely important role. The coating formed by the sequential addition of monomers A, B, and C effectively improves the structure of the aeolian sandy soil and significantly increases the number of aggregates >0.25nm, thus forming water-stable macroaggregates. These aggregates not only stabilize the soil structure and improve soil permeability, but also prevent the occurrence of topsoil crusting.

[0018] Therefore, the biochar composite amendment not only solves the problem 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 in conjunction with specific embodiments.

[0020] Embodiment 1:

[0021] (1) 20 g corn stalks were 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) dissolving 2 g of acrylamide, 0.03 N,N′-methylenebisacrylamide, and 1 g of acrylic acid in 15 g of deionized water, stirring for 10 min, and adjusting the pH to 8.2 with sodium hydroxide to obtain a monomer B solution;

[0024] (4) adding 0.5 g acrylamide and 2 g methacryloyloxyethyl trimethyl ammonium chloride to 10 g deionized water and stirring 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 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 stirring was continued 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 stirring was continued 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 monomers were 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] Embodiment 2:

[0027] (1) 20 g corn stalks were 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 impurities such as ash, 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) dissolving 3 g of acrylamide, 0.05 N,N′-methylenebisacrylamide, and 2 g of acrylic acid in 20 g of deionized water, stirring for 20 min, and adjusting the pH to 8.5 with sodium hydroxide to obtain a monomer B solution;

[0030] (4) adding 1 g of acrylamide and 3 g of methacryloyloxyethyl trimethyl ammonium chloride to 16 g of deionized water and stirring for 10 min to obtain a monomer C solution;

[0031] (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 0.15 g of ammonium persulfate, stir for 30 min, then drop 75 g of monomer A solution, continue stirring for 2 h after the addition is complete, then add 0.05 g of ammonium persulfate, stir for 10 min, then drop 25 g of monomer B solution, continue stirring for 3 h after the addition is complete, then add 0.04 g of ammonium persulfate, stir for 10 min, then drop 20 g of monomer C solution, continue stirring for 5 h after the addition is complete, finally wash and remove the unreacted monomer with deionized water, let stand for 24 h, vacuum dry for 6 h, and grind through a 100-mesh sieve to obtain a biochar composite improver for soil structure improvement.

[0032] Embodiment 3:

[0033] (1) 20 g corn stalks were 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 impurities such as ash, 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) adding 2 g of acrylamide and 4 g of methacryloyloxyethyl trimethyl ammonium chloride to 20 g of deionized water and stirring 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 passed 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, stirring was continued for 2.5 h. Then 0.07 g of ammonium persulfate was added, and stirring was continued for 15 min. Then 32 g of monomer B solution was added dropwise. After the addition was completed, stirring was continued for 4 h. Then 0.06 g of ammonium persulfate was added, and stirring was continued for 15 min. Then 26 g of monomer C solution was added dropwise. After the addition was completed, stirring was continued for 6 h. Finally, the unreacted monomers were 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: no monomer A solution is added dropwise;

[0040] The specific steps are as follows:

[0041] (1) 20 g corn stalks were 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 impurities such as ash, 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) adding 1 g of acrylamide and 3 g of methacryloyloxyethyl trimethyl ammonium chloride to 16 g of deionized water and stirring 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 pass nitrogen for 30 min. Then heat to 70 °C, add 0.05 g of ammonium persulfate, stir for 10 min, then drop 25 g of monomer B solution, continue stirring for 3 h after the addition is complete, then add 0.04 g of ammonium persulfate, stir for 10 min, then drop 20 g of monomer C solution, 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, 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: no monomer B solution is added dropwise;

[0047] The specific steps are as follows:

[0048] (1) 20 g corn stalks were 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 impurities such as ash, 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) adding 1 g of acrylamide and 3 g of methacryloyloxyethyl trimethyl ammonium chloride to 16 g of deionized water and stirring 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 drop 75 g of monomer A solution, continue stirring for 2 h after the addition is complete, then add 0.04 g of ammonium persulfate, stir for 10 min, then drop 20 g of monomer C solution, 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, and 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: no monomer C solution is added dropwise;

[0054] The specific steps are as follows:

[0055] (1) 20 g corn stalks were 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 impurities such as ash, 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) dissolving 3 g of acrylamide, 0.05 N,N′-methylenebisacrylamide, and 2 g of acrylic acid in 20 g of deionized water, stirring for 20 min, and adjusting the pH 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 drop 75 g of monomer A solution, continue stirring for 2 h after the addition is complete, then add 0.05 g of ammonium persulfate, stir for 10 min, then drop 25 g of monomer B solution, 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, and 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 corn stalks were 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 impurities such as ash, 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) dissolving 3 g of acrylamide, 0.05 N,N′-methylenebisacrylamide, and 2 g of acrylic acid in 20 g of deionized water, stirring for 20 min, and adjusting the pH to 8.5 with sodium hydroxide to obtain a monomer B solution;

[0065] (4) adding 1 g of acrylamide and 3 g of methacryloyloxyethyl trimethyl ammonium chloride to 16 g of deionized water and stirring 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 and remove 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 put into pots, and each treatment was repeated 3 times. After applying the water retaining agent, mix well, insert the water tensiometer, add water to reach the saturated moisture content, and place it 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 saturated moisture content of the soil 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] Test of water-stable aggregate properties: The samples that have passed the water holding performance test were placed outdoors for 1 month, and the particle size distribution of soil stability aggregates was determined by mechanical screening method. 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 improver 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 improver 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 formed by monomer A can significantly increase the saturated moisture content of sandy soil. This is mainly because the high cross-linking density coating layer formed by 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 coating 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 coating layer composed of monomer B can form a gradient suction with the high cross-linking density coating layer composed of monomer A, which is beneficial to transfer moisture to the internal pores, and the low cross-linking density coating layer composed of monomer B with appropriate moisture absorption is beneficial to provide moisture that is most easily utilized by crops.

[0077] It can be seen from the data of Example 2 and Comparative Example 3 in Table 1 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] It can be seen from the data of Example 2 and Comparative Example 4 in Table 1 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 the sandy soil and the moisture most easily utilized by crops.

[0079] Table 2 Properties of water-stable aggregates

[0080]

[0081] Data Analysis:

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

[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 macroaggregates, 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. Under the concept 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, the monomer B solution and the monomer C solution are sequentially coated and polymerized on the surface of the biochar powder; The weight ratio of the monomer A solution, the monomer B solution, the monomer C solution and the biochar powder is 62-88:18-32:12-26:3-8; 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 the pH is adjusted to 8-9 with sodium hydroxide to obtain a monomer A solution; The preparation method of the monomer B solution is 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: by weight, 0.5-2 parts of acrylamide and 2-4 parts of methacryloyloxyethyl trimethyl ammonium chloride are added to 10-20 parts of deionized water, 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 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 monomer A solution, continuing stirring for 1.5-2.5 hours after the dripping is completed, adding ammonium persulfate, stirring for 5-15 minutes, dripping monomer B solution, continuing stirring for 2-4 hours after the dripping is completed, adding ammonium persulfate, stirring for 5-15 minutes, dripping monomer C solution, continuing stirring 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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