A composite organic fertilizer for improving saline-alkali soil and a preparation method thereof

Abstract

This invention belongs to the field of compound organic fertilizer technology, specifically relating to a compound organic fertilizer for improving saline-alkali soil and its preparation method. The compound organic fertilizer for improving saline-alkali soil of this invention comprises the following raw materials by weight: 40-50 parts plant straw, 10-15 parts urea, 5-10 parts humic acid, 3-8 parts modified bentonite, 5-10 parts compound microbial agent, and 2-5 parts regulator. This invention features strong component synergy and long-lasting stable effects. The regulator and modified bentonite not only reduce soil salt concentration and pH value, but also provide an organic carbon source, improving the improvement effect on saline-alkali soil. Furthermore, the modified bentonite can significantly enhance soil water retention capacity, improve soil structure, slow nutrient loss, and improve the soil environment; it has good prospects for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of compound organic fertilizer technology, specifically relating to a compound organic fertilizer for improving saline-alkali soil and its preparation method. Background Technology

[0002] Saline-alkali land is an important reserve of arable land globally and in my country. Its high pH value, high exchangeable sodium content, and poor physical structure severely inhibit vegetation growth, leading to declining land productivity, ecological degradation, and hindering sustainable agricultural development and food security. Soil salinization increases osmotic pressure, hindering crop roots from absorbing water. Simultaneously, sodium ion toxicity damages soil aggregate structure, causing compaction and poor aeration. Furthermore, severe nutrient fixation and low microbial activity further exacerbate the problem. Therefore, developing efficient, long-lasting, and environmentally friendly saline-alkali land conditioners has become an urgent need in modern agriculture.

[0003] Current technologies for improving saline-alkali land mainly employ methods such as water flushing, chemical amendments (e.g., gypsum, phosphogypsum, ferrous sulfate), and the application of organic fertilizers. However, water flushing consumes a large amount of water, easily leading to rising groundwater levels and secondary salinization. While chemical amendments can neutralize alkalinity in the short term, their effects are limited, they are easily leached away by rainwater, and excessive use may result in the accumulation of heavy metals in the soil or structural damage. Furthermore, although traditional organic fertilizers can replenish organic matter, their mineralization rate is slow, limiting their effectiveness in rapidly lowering soil pH and replacing sodium ions, making them unsuitable for addressing severe saline-alkali stress.

[0004] In recent years, composite soil amendment technologies based on microbial agents and mineral carriers have gradually emerged. For example, humic acid is used in conjunction with microbial agents to improve soil microecology, or bentonite is used to adsorb soil salinity. However, existing technologies still have significant drawbacks: First, most amendments have limited functionality; simple physical adsorption cannot solve the problem of nutrient availability, and simple chemical neutralization cannot improve soil structure. They struggle to simultaneously address multiple issues such as pH regulation, structural improvement, and nutrient supply, often increasing application costs and operational complexity. Second, acid-regulating substances are easily neutralized or lost by the soil buffer system when applied directly, lacking slow-release carriers and making it difficult to maintain a long-term acidic environment in the rhizosphere.

[0005] How to construct a compound organic fertilizer system that can both slowly release acidic substances to lower the pH value and have excellent water retention properties, and simultaneously improve the soil fertility of saline-alkali land, is a difficult problem that urgently needs to be overcome in current technology. Summary of the Invention

[0006] The primary objective of this invention is to provide a compound organic fertilizer for improving saline-alkali soil. This invention aims to provide a long-lasting and stable solution for improving saline-alkali soil by combining modified bentonite with porous silica-based regulators and specific compound microbial agents, thereby overcoming the shortcomings of existing technologies.

[0007] The second objective of this invention is to provide a method for preparing a compound organic fertilizer for improving saline-alkali soil.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A compound organic fertilizer for improving saline-alkali soil comprises the following raw materials by weight: 40-50 parts of plant straw, 10-15 parts of urea, 5-10 parts of humic acid, 3-8 parts of modified bentonite, 5-10 parts of compound microbial agent, and 2-5 parts of regulator. The preparation process of the regulator is as follows: (1) Add tetraethyl orthosilicate, phytic acid, calcium acetate and hexadecyltrimethylammonium bromide to an aqueous solution of ethanol, stir at room temperature for 1-3 h, let stand for aging for 20-24 h, centrifuge, collect the precipitate, and obtain porous silica-based microspheres after drying and calcination. (2) Add the porous silica microspheres, citric acid, and β-alanyl-L-histidine from step (1) to water, stir ultrasonically for 3-5 hours, centrifuge, collect the precipitate, add Tris-dopamine hydrochloride solution, stir at room temperature for 10-15 hours to obtain the regulator.

[0009] Further, in step (1), the ratio of the aqueous solution of tetraethyl orthosilicate, phytic acid, calcium acetate, hexadecyltrimethylammonium bromide, and ethanol is 10mL:1-1.5g:3-4g:2-3g:80mL; and the volume ratio of anhydrous ethanol to water in the aqueous solution of ethanol is 3:1.

[0010] Furthermore, the calcination temperature in step (1) is 550-600℃ and the time is 1-3h.

[0011] Further, in step (2), the mass ratio of porous silica microspheres, citric acid, and β-alanyl-L-histidine is 1:(0.3-0.5):(0.08-0.15); the solid-liquid ratio of the porous silica microspheres to water is 1g:10mL; the solid-liquid ratio of the precipitate to the Tris-dopamine hydrochloride solution is 1g:2mL, and the concentration of dopamine hydrochloride in the Tris-dopamine hydrochloride solution is 2-3g / L.

[0012] Further, the preparation process of the modified bentonite is as follows: Bentonite and 5-carboxypentyltriphenylphosphine bromide are added to water and reacted at 60-70℃ for 3-5 hours to obtain pretreated bentonite; the pretreated bentonite and konjac glucomannan are added to water and ball-milled to obtain modified bentonite.

[0013] Furthermore, the mass ratio of bentonite to 5-carboxypentyltriphenylphosphine bromide is 30:(23-36); when bentonite and 5-carboxypentyltriphenylphosphine bromide are added to water, the mass of water is 30 times that of bentonite.

[0014] Furthermore, the mass ratio of the pretreated bentonite to konjac glucomannan is (1-2):1; when the pretreated bentonite and konjac glucomannan are added to water, the amount of water added is 100 times the mass of the pretreated bentonite.

[0015] Furthermore, the number of effective viable bacteria in the compound microbial agent is not less than 8 × 10⁻⁶. 8 CFU / g.

[0016] Furthermore, the effective live bacteria ratio of Bacillus megaterium and Bacillus lateralis in the compound microbial agent is 1:(1.5-2.2).

[0017] A method for preparing a compound organic fertilizer for improving saline-alkali soil includes the following steps: According to the formula, mix the compound microbial agent and modified bentonite evenly and let it stand for 5-7 hours; then add plant straw, urea, humic acid and regulator and mix evenly to obtain the final product.

[0018] Compared with the prior art, the main advantages of the present invention are as follows: 1. The regulator of this invention uses porous silica-based microspheres as a carrier, which are prepared by calcination to create pores, loading citric acid and β-alanyl-L-histidine, and finally modifying the surface with dopamine. The porous silica-based microspheres not only provide trace elements such as calcium, phosphorus, and silicon, but the calcium ions can also be released into the soil, replacing sodium ions, reducing soil salinity, and improving the soil environment. Simultaneously, the porous structure improves the stability of citric acid and β-alanyl-L-histidine. Citric acid can activate insoluble phosphorus, promote calcium ion migration, neutralize alkalinity, and lower soil pH. β-alanyl-L-histidine has dual functions of metal chelation and osmotic regulation, improving the rhizosphere environment of plants. The dopamine modification layer further enhances the dispersion stability and interfacial affinity of the porous silica-based microspheres in saline-alkali soils, further improving the improvement effect on saline-alkali soils.

[0019] 2. The modified bentonite of this invention uses 5-carboxypentyltriphenylphosphine bromide to organically intercalate and modify bentonite. Organic cations and carboxyl groups are stably inserted into the bentonite interlayer, expanding the interlayer spacing and improving ion exchange and adsorption capacity. Sodium ions from the soil are adsorbed and fixed through ion exchange, while the carboxyl groups neutralize soil alkalinity, lower the pH value, and provide an organic carbon source. Furthermore, it is compounded with konjac glucomannan through ball milling. The konjac glucomannan coats or intercalates on the surface and between layers of the bentonite particles, significantly improving soil water retention capacity, improving soil structure, and slowing nutrient loss. Attached Figure Description

[0020] Figure 1 This is an electron microscope image of the regulator obtained in Example 1 of the present invention; Figure 2 This is an electron microscope image of the modified bentonite obtained in Example 1 of the present invention. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products obtained through commercial channels.

[0022] Example 1 A compound organic fertilizer for improving saline-alkali soil comprises the following raw materials by weight: 45 parts plant straw, 13 parts urea, 8 parts humic acid, 5 parts modified bentonite, 8 parts compound microbial agent, and 4 parts regulator. Among them, the number of effective live bacteria in the compound microbial agent is not less than 8×10. 8 CFU / g; Bacillus megater in compound bacterial agent Bacillus megaterium (Strain number: CICC 10044) and Bacillus laterosporus Brevibacillus laterosporus The effective live bacteria ratio of (strain number: CICC 21185) is 1:2.

[0023] The preparation process of the regulator is as follows: (1) Tetraethyl orthosilicate, phytic acid, calcium acetate, and hexadecyltrimethylammonium bromide were added to an aqueous solution of ethanol (the volume ratio of anhydrous ethanol to water was 3:1). The volume ratio of tetraethyl orthosilicate, phytic acid, calcium acetate, hexadecyltrimethylammonium bromide, and the aqueous solution of ethanol was 10mL:1.2g:3.5g:2.5g:80mL. The mixture was stirred at room temperature for 2 hours, allowed to stand for 22 hours, centrifuged, and the precipitate was collected. After drying and calcination at 580℃ for 2 hours, porous silica-based microspheres were obtained. (2) The porous silica microspheres, citric acid, and β-alanyl-L-histidine from step (1) were added to water, with a mass ratio of 1:0.4:0.12; the solid-liquid ratio of the porous silica microspheres to water was 1 g:10 mL; after ultrasonic stirring for 4 h, the mixture was centrifuged and the precipitate was collected; dopamine hydrochloride was added to 10 mM Tris buffer solution with a pH of 8.5 to obtain a Tris-dopamine hydrochloride solution with a concentration of 2.5 g / L; the precipitate was added to the Tris-dopamine hydrochloride solution, with a solid-liquid ratio of 1 g:2 mL; the mixture was stirred at room temperature for 12 h; after centrifugation, washing, and drying, the regulator was obtained. The electron micrograph of the regulator is shown below. Figure 1 As shown.

[0024] The preparation process of modified bentonite is as follows: Bentonite and 5-carboxypentyltriphenylphosphine bromide are added to water in a mass ratio of 30:30:900. The mixture is then reacted at 65°C for 4 hours. After the reaction is complete, the mixture is filtered, washed with deionized water until no bromide ions are present, and dried to obtain pretreated bentonite. The pretreated bentonite and konjac glucomannan are added to water in a mass ratio of 1.5:1:150. The mixture is ball-milled at 400 rpm at room temperature for 13 hours and then dried to obtain modified bentonite. The electron micrograph of the modified bentonite is shown below. Figure 2 As shown.

[0025] A method for preparing a compound organic fertilizer for improving saline-alkali soil includes the following steps: According to the formula, mix the compound microbial agent and modified bentonite evenly and let it stand for 6 hours; then add plant straw, urea, humic acid and regulator and mix evenly to obtain the final product.

[0026] Example 2 A compound organic fertilizer for improving saline-alkali soil comprises the following raw materials by weight: 40 parts plant straw, 10 parts urea, 5 parts humic acid, 3 parts modified bentonite, 5 parts compound microbial agent, and 2 parts regulator. Among them, the number of effective live bacteria in the compound microbial agent is not less than 8×10. 8 CFU / g; The effective live bacteria ratio of Bacillus megaterium and Bacillus lateralis in the compound bacterial agent is 1:1.5.

[0027] The preparation process of the regulator is as follows: (1) Tetraethyl orthosilicate, phytic acid, calcium acetate, and hexadecyltrimethylammonium bromide were added to an aqueous solution of ethanol (the volume ratio of anhydrous ethanol to water was 3:1). The volume ratio of tetraethyl orthosilicate, phytic acid, calcium acetate, hexadecyltrimethylammonium bromide, and the aqueous solution of ethanol was 10mL:1g:3g:2g:80mL. The mixture was stirred at room temperature for 1 hour, allowed to stand for 20 hours, centrifuged, and the precipitate was collected. After drying and calcination at 550℃ for 3 hours, porous silica-based microspheres were obtained. (2) Add the porous silica microspheres, citric acid, and β-alanyl-L-histidine from step (1) to water. The mass ratio of the porous silica microspheres, citric acid, and β-alanyl-L-histidine is 1:0.3:0.08. The solid-liquid ratio of the porous silica microspheres to water is 1g:10mL. After ultrasonic stirring for 3h, centrifuge and collect the precipitate. Add dopamine hydrochloride to 10mM Tris buffer solution with pH 8.5 to obtain a Tris-dopamine hydrochloride solution with a concentration of 2g / L. Add the precipitate to the Tris-dopamine hydrochloride solution. The solid-liquid ratio of the precipitate to the Tris-dopamine hydrochloride solution is 1g:2mL. Stir at room temperature for 10h. After centrifugation, washing, and drying, obtain the regulator.

[0028] The preparation process of modified bentonite is as follows: Bentonite and 5-carboxypentyltriphenylphosphine bromide are added to water in a mass ratio of 30:23:900. The mixture is then reacted at 60°C for 5 hours. After the reaction is complete, the mixture is filtered, washed with deionized water until no bromide ions are present, and dried to obtain pretreated bentonite. The pretreated bentonite and konjac glucomannan are added to water in a mass ratio of 1:1:100. The mixture is ball-milled at 380 rpm at room temperature for 14 hours and then dried to obtain modified bentonite.

[0029] A method for preparing a compound organic fertilizer for improving saline-alkali soil includes the following steps: According to the formula, mix the compound microbial agent and modified bentonite evenly and let it stand for 5 hours; then add plant straw, urea, humic acid and regulator and mix evenly to obtain the final product.

[0030] Example 3 A compound organic fertilizer for improving saline-alkali soil comprises the following raw materials by weight: 50 parts plant straw, 15 parts urea, 10 parts humic acid, 8 parts modified bentonite, 10 parts compound microbial agent, and 5 parts regulator. Among them, the number of effective live bacteria in the compound microbial agent is not less than 8×10. 8 CFU / g; The effective live bacteria ratio of Bacillus megaterium and Bacillus lateralis in the compound bacterial agent is 1:2.2.

[0031] The preparation process of the regulator is as follows: (1) Tetraethyl orthosilicate, phytic acid, calcium acetate, and hexadecyltrimethylammonium bromide were added to an aqueous solution of ethanol (the volume ratio of anhydrous ethanol to water was 3:1). The volume ratio of tetraethyl orthosilicate, phytic acid, calcium acetate, hexadecyltrimethylammonium bromide, and the aqueous solution of ethanol was 10mL:1.5g:4g:3g:80mL. The mixture was stirred at room temperature for 3 hours, allowed to stand for 24 hours, centrifuged, and the precipitate was collected. After drying and calcination at 600℃ for 1 hour, porous silica-based microspheres were obtained. (2) Add the porous silica microspheres, citric acid, and β-alanyl-L-histidine from step (1) to water. The mass ratio of the porous silica microspheres, citric acid, and β-alanyl-L-histidine is 1:0.5:0.15. The solid-liquid ratio of the porous silica microspheres to water is 1g:10mL. After ultrasonic stirring for 5h, centrifuge and collect the precipitate. Add dopamine hydrochloride to 10mM Tris buffer solution with pH 8.5 to obtain a Tris-dopamine hydrochloride solution with a concentration of 3g / L. Add the precipitate to the Tris-dopamine hydrochloride solution. The solid-liquid ratio of the precipitate to the Tris-dopamine hydrochloride solution is 1g:2mL. Stir at room temperature for 15h. After centrifugation, washing, and drying, obtain the regulator.

[0032] The preparation process of modified bentonite is as follows: Bentonite and 5-carboxypentyltriphenylphosphine bromide are added to water in a mass ratio of 30:36:900. The mixture is then reacted at 70°C for 3 hours. After the reaction is complete, the mixture is filtered, washed with deionized water until no bromide ions are present, and dried to obtain pretreated bentonite. The pretreated bentonite and konjac glucomannan are added to water in a mass ratio of 2:1:200. The mixture is ball-milled at 420 rpm at room temperature for 12 hours and then dried to obtain modified bentonite.

[0033] A method for preparing a compound organic fertilizer for improving saline-alkali soil includes the following steps: According to the formula, mix the compound microbial agent and modified bentonite evenly and let it stand for 7 hours; then add plant straw, urea, humic acid and regulator and mix evenly to obtain the final product.

[0034] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the regulator is replaced with citric acid, while everything else remains the same as in Example 1.

[0035] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the modified bentonite is replaced with bentonite and konjac glucomannan, while the rest is the same as Example 1.

[0036] Test case To investigate the effects of the compound organic fertilizer obtained in this invention on the improvement of saline-alkali soil and the impact on crop yield, a field plot experiment was set up to test and analyze the effects of Examples 1-3 and Comparative Examples 1-2.

[0037] 1. Experimental area: Saline-alkali land experimental field was selected. The basic physical and chemical properties of the soil were: pH=8.71, soil organic matter 8.65g / kg, field water holding capacity 15.8%; and total water-soluble salts 3.36g / kg.

[0038] 2. Test crop: The maize variety was Jidan 27.

[0039] 3. Experimental design: The above experimental area was set up into 6 treatment groups: Example 1-3 groups, Comparative Example 1-2 groups, and blank control group.

[0040] Before planting corn, the compound organic fertilizer obtained in Examples 1-3 and Comparative Examples 1-2 of this invention was spread on the surface of saline-alkali land, and then rotary tilled to a depth of 20 cm to mix it with the soil. The application rate was 40 kg / mu, and conventional fertilizer (N, P, K ratio of 36:13:6; application rate of 50 kg / mu) was applied. The blank control group was only given the same amount of conventional fertilizer. During the experiment, the field management measures (irrigation, weeding, pest and disease control, etc.) of each plot were kept consistent.

[0041] (1) During the silking stage of corn, select plants with uniform growth, wash the roots clean, measure the total root volume of the plants, and then dry the roots in a 65℃ oven until constant weight, and weigh the dry weight of the roots; the results are shown in Table 1.

[0042] (2) After the corn matured, the thousand-grain weight and yield of the corn were measured; the results are shown in Table 2.

[0043] (3) After the corn harvest, various indicators were measured: Soil physicochemical indicators: Soil pH was measured according to the method of NY / T1377-2007; Soil organic matter content was detected according to NY / T1121.6-2006; Field water holding capacity was measured according to NY / T3678-2020; Total water-soluble salts were measured according to NY / T1121.16-2006. The above results are recorded in Table 3.

[0044] Table 1 Table 1 shows that the dry weight and volume of maize roots in Examples 1-3 were higher than those in Comparative Examples 1-2 and the blank control group. Comparative Example 1, which replaced the growth regulator, had the worst root dry weight and volume. This indicates that the compound organic fertilizer of the present invention can improve the rhizosphere environment of plants, creating favorable conditions for maize root growth and nutrient absorption. In contrast, Comparative Examples 1 and 2, due to limited soil improvement effects, still showed significant salt-alkali stress, and their root growth was still significantly inhibited.

[0045] Table 2 As shown in Table 2, the thousand-grain weight and corn yield per mu (a Chinese unit of area, approximately 0.067 hectares) of Examples 1-3 were significantly higher than those of the blank control group. Although the yields of Comparative Examples 1 and 2 were higher than those of the blank control group, they were still lower than those of Examples 1-3. This indicates that the compound organic fertilizer of the present invention simultaneously improves the salinization degree of saline-alkali soil, increases organic matter content, and enhances water retention capacity. The improved soil environment is more suitable for corn growth, thereby increasing corn yield.

[0046] Table 3 As shown in Table 3, the soil pH and total water-soluble salt content of Examples 1-3 were significantly lower than those of Comparative Examples 1-2 and the blank control group, while the soil organic matter content and field water holding capacity were significantly increased; among them, Example 1 showed the best soil improvement effect. Comparative Example 1 used only citric acid to replace the regulator of the present invention, and the soil pH and total water-soluble salt content were higher than those of Example 1. The main reason is that citric acid has no slow-release carrier and is easily neutralized by the soil buffer system and lost with water, so it cannot maintain a long-term alkalinity reduction effect. Comparative Example 2 used a physical mixture of bentonite and konjac glucomannan to replace modified bentonite. Its ion exchange and salt ion adsorption capacity is weak, the salt and alkali reduction effect is limited, and its water retention capacity and soil structure improvement effect are far lower than those of the modified bentonite of the present invention.

[0047] In summary, the compound organic fertilizer of this invention can effectively reduce the pH value and total water-soluble salt content of saline-alkali soils, significantly increase soil organic matter content and field water holding capacity, and simultaneously achieve soil salinity and alkali reduction, structural improvement, and fertilization and water retention. The improved soil environment can effectively relieve the growth inhibition of crops caused by salinization, significantly improve crop agronomic traits, and greatly increase crop yield. The organic fertilizer of this invention is of great significance for improving the quality and increasing the yield of agricultural production in saline-alkali lands, and has good prospects for industrial production and field application.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A compound organic fertilizer for improving saline-alkali soil, characterized in that, The ingredients include the following raw materials by weight: 40-50 parts of plant straw, 10-15 parts of urea, 5-10 parts of humic acid, 3-8 parts of modified bentonite, 5-10 parts of compound microbial agent, and 2-5 parts of regulator. The preparation process of the regulator is as follows: (1) Add tetraethyl orthosilicate, phytic acid, calcium acetate and hexadecyltrimethylammonium bromide to an aqueous solution of ethanol, stir at room temperature for 1-3 h, let stand for aging for 20-24 h, centrifuge, collect the precipitate, and obtain porous silica-based microspheres after drying and calcination. (2) Add the porous silica microspheres, citric acid, and β-alanyl-L-histidine from step (1) to water, stir ultrasonically for 3-5 hours, centrifuge, collect the precipitate, add Tris-dopamine hydrochloride solution, stir at room temperature for 10-15 hours to obtain the regulator.

2. The compound organic fertilizer for improving saline-alkali soil according to claim 1, characterized in that, In step (1), the ratio of the aqueous solution of tetraethyl orthosilicate, phytic acid, calcium acetate, hexadecyltrimethylammonium bromide, and ethanol is 10mL:1-1.5g:3-4g:2-3g:80mL; the volume ratio of anhydrous ethanol to water in the aqueous solution of ethanol is 3:

1.

3. The compound organic fertilizer for improving saline-alkali soil according to claim 1, characterized in that, The calcination temperature in step (1) is 550-600℃ and the time is 1-3h.

4. The compound organic fertilizer for improving saline-alkali soil according to claim 1, characterized in that, In step (2), the mass ratio of the porous silica microspheres, citric acid, and β-alanyl-L-histidine is 1:(0.3-0.5):(0.08-0.15); the solid-liquid ratio of the porous silica microspheres to water is 1g:10mL; the solid-liquid ratio of the precipitate to the Tris-dopamine hydrochloride solution is 1g:2mL, and the concentration of dopamine hydrochloride in the Tris-dopamine hydrochloride solution is 2-3g / L.

5. The compound organic fertilizer for improving saline-alkali soil according to claim 1, characterized in that, The preparation process of the modified bentonite is as follows: Bentonite and 5-carboxypentyltriphenylphosphine bromide are added to water and reacted at 60-70℃ for 3-5 hours to obtain pretreated bentonite; the pretreated bentonite and konjac glucomannan are added to water and ball-milled to obtain modified bentonite.

6. The compound organic fertilizer for improving saline-alkali soil according to claim 5, characterized in that, The mass ratio of bentonite to 5-carboxypentyltriphenylphosphine bromide is 30:(23-36); when bentonite and 5-carboxypentyltriphenylphosphine bromide are added to water, the mass of water is 30 times that of bentonite.

7. The compound organic fertilizer for improving saline-alkali soil according to claim 5, characterized in that, The mass ratio of the pretreated bentonite to konjac glucomannan is (1-2):1; when the pretreated bentonite and konjac glucomannan are added to water, the amount of water added is 100 times the mass of the pretreated bentonite.

8. The compound organic fertilizer for improving saline-alkali soil according to claim 1, characterized in that, The number of viable bacteria in the compound microbial agent is not less than 8 × 10⁻⁶. 8 CFU / g.

9. The compound organic fertilizer for improving saline-alkali soil according to claim 8, characterized in that, The effective live bacteria ratio of Bacillus megaterium and Bacillus brevis in the compound microbial agent is 1:(1.5-2.2).

10. A method for preparing a compound organic fertilizer for improving saline-alkali soil according to any one of claims 1-9, characterized in that, Includes the following steps: According to the formula, mix the compound microbial agent and modified bentonite evenly and let it stand for 5-7 hours; then add plant straw, urea, humic acid and regulator and mix evenly to obtain the final product.

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