Soil conditioner for improving saline-alkali soil and preparation method thereof

Abstract

The invention discloses a soil conditioner for improving saline-alkali soil and a preparation method of the soil conditioner, and belongs to the technical field of saline-alkali soil improvement. Firstly, natural bentonite is modified, and bentonite is subjected to calcification modification to obtain calcium bentonite; then dipping the calcium bentonite in a ferric salt solution for salt modification to obtain salt modified calcium bentonite; dispersing the salt modified calcium bentonite in deionized water to form a suspension, slowly adding a humic acid solution into the suspension, reacting under stirring and heating conditions, and standing and aging to obtain modified bentonite; wherein the concentration of iron ions in the ferric salt solution is 0.1 to 0.2 M, and the dipping time is 40 to 60 minutes; then the modified bentonite and the complex microbial inoculant are compounded and jointly used as the soil improvement agent, through the synergistic effect of the modified bentonite, the leguminous green manure and the complex microbial inoculant, a chemical modification and biological modification coupling mechanism is formed, and the improvement effect on moderate saline-alkali soil in arid regions is especially remarkable.

Description

Technical Field

[0001] This invention belongs to the field of saline-alkali land improvement technology, and particularly relates to a soil conditioner for improving saline-alkali land and its preparation method. Background Technology

[0002] Saline-alkali land, a global issue of land degradation, has long plagued numerous countries and regions. Its prominent characteristics—high salinity, high alkalinity, and low permeability—have severe negative impacts on soil. High salinity disrupts the soil's ion concentration, high alkalinity disrupts the soil's acid-base balance, and low permeability hinders the normal flow of water and air within the soil, leading to soil structure damage. Previously fertile soil becomes loose and compacted, resulting in significant nutrient loss. This situation severely restricts agricultural production and ecological restoration, making it difficult for crops to grow normally, significantly reducing yields, and posing a major challenge to the stability of the ecosystem.

[0003] Traditional improvement methods, such as physical flushing, chemical neutralization, and bioremediation, have provided feasible approaches for the improvement of saline-alkali land to some extent. Although effective to a certain degree, they have limitations such as high cost, long cycle, and easy to cause secondary pollution.

[0004] Specifically, traditional physical flushing methods rely on large amounts of freshwater rinsing. The principle is to use the flushing action of freshwater to dissolve salts from the soil and remove them with the water. In this process, a large amount of freshwater needs to be introduced into the saline-alkali land through an irrigation system, allowing the water to fully infiltrate the soil and dissolve the salts. The salt-containing water is then drained away through a drainage system. However, while this method is applicable in water-rich areas, it is difficult to implement in arid regions due to water scarcity. In arid areas, water resources are already extremely scarce, making it almost impossible to obtain large quantities of freshwater for flushing saline-alkali land. Moreover, this method easily leads to salt infiltration into groundwater aquifers. When salts infiltrate the groundwater with the water flow, the salinity of the groundwater increases, triggering secondary salinization and further deteriorating the soil and water environment.

[0005] Chemical neutralization involves using soil conditioners such as gypsum and ferrous sulfate, which react chemically with alkaline substances in the soil to rapidly reduce soil alkalinity. In practice, the conditioner is typically spread evenly on saline-alkali land and then thoroughly mixed with the soil through tilling. However, long-term use of this method can easily lead to soil compaction. Over time, the accumulation of chemicals in the soil reduces the gaps between soil particles, making the soil compacted and reducing its aeration and permeability. Furthermore, excessive chemical residues can disrupt the balance of the microbial community. Soil microorganisms play a crucial role in soil health and ecosystem stability; excessive chemical residues can inhibit or even kill beneficial microorganisms, altering the structure and function of the microbial community and affecting soil fertility and ecological function.

[0006] Bioremediation involves planting salt-tolerant plants or applying microbial inoculants. Salt-tolerant plants possess unique physiological mechanisms that enable them to grow in high-salt environments; they absorb salt from the soil, improving its salinity. Microbial inoculants, through interaction with plant roots, promote plant growth and enhance their salt tolerance. However, this method is time-consuming and limited by climate conditions. Planting salt-tolerant plants requires a long growth cycle to achieve significant improvement, and different salt-tolerant plants have different climatic requirements; unsuitable conditions can severely hinder plant growth. In moderately or severely saline-alkali lands, the high salinity and alkalinity significantly limit the growth and effectiveness of both salt-tolerant plants and microbial inoculants, resulting in limited benefits. Summary of the Invention

[0007] In view of the technical problems existing in the prior art, the present invention proposes a soil conditioner for improving saline-alkali land and its preparation method.

[0008] To achieve the above objectives, the present invention provides the following technical solution: This invention first provides a method for modifying bentonite, which involves first calcifying bentonite to obtain calcium-based bentonite; then impregnating the calcium-based bentonite in an iron salt solution for salt modification to obtain salt-modified calcium-based bentonite; then dispersing the salt-modified calcium-based bentonite in deionized water to form a suspension; then slowly adding a humic acid solution to the suspension; reacting under stirring and heating conditions; and finally allowing it to stand for aging to obtain modified bentonite; wherein the iron ion concentration in the iron salt solution is 0.1~0.2M, and the impregnation time is 40~60min.

[0009] As a further improvement of the present invention, the method of calcification modification is as follows: Bentonite is impregnated in a calcium salt solution at a solid-liquid ratio of 1:(8~10) for 120~150 min. After impregnation, it is washed with deionized water, dried, and then ground through a 100-mesh sieve. The calcium salt solution is selected from calcium chloride or calcium nitrate solutions. The concentration of the calcium salt solution is 0.3~0.5M.

[0010] As a further improvement of the present invention, the method for preparing the humic acid solution is as follows: dissolving humic acid in water, adjusting the pH to 8-9 with sodium hydroxide solution to obtain a humic acid solution with a concentration of 5-8 g / L; and / or, heating at a temperature of 60-70°C; and the reaction time being 1-1.5 h.

[0011] As a further improvement of the present invention, the static aging time is 12~24h.

[0012] A second aspect of the present invention also provides a modified bentonite, which is prepared by the above-described bentonite modification method.

[0013] A third aspect of the present invention also provides the application of modified bentonite in the preparation of soil conditioners for improving saline-alkali land.

[0014] The fourth aspect of the present invention provides a soil conditioner for improving saline-alkali land, comprising the above-mentioned modified bentonite and a compound microbial agent; the mass ratio of the modified bentonite to the compound microbial agent is 100:1 to 1.5.

[0015] Furthermore, the compound microbial agent includes Bacillus subtilis and Bacillus licheniformis in a mass ratio of 1:(1~2).

[0016] The fifth aspect of this invention provides the application of a soil conditioner for improving saline-alkali land.

[0017] The sixth aspect of the present invention also provides a method for improving saline-alkali land, which involves spreading crushed plant straw on the surface of the saline-alkali land, deep plowing, drying the land for one week, spreading a soil conditioner for improving saline-alkali land on the surface, plowing again, planting leguminous green manure, and returning the straw to the field after the green manure matures.

[0018] Specifically, there are no restrictions on the type of plant straw; for example, it can be corn straw, wheat straw, or legume green manure straw. The straw should be shredded using a straw crusher before being applied to the soil. Deep plowing refers to a tillage depth of ≥30cm, which ensures that the straw penetrates deep into the soil, forming a straw barrier layer. The purpose of allowing the land to dry for a week is to allow the straw to decompose in the soil.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects: (1) In this invention, bentonite is first modified by calcification to improve its cation exchange capacity and provide a basis for subsequent iron ion exchange; then salt modification is carried out to replace part of the sodium ions in bentonite with ferric ions. The ferric hydroxide colloid generated by the hydrolysis of iron ions can promote the formation of soil aggregates and solve the problem of soil compaction in saline-alkali land. At the same time, iron oxides combine with humic acid to enhance the adsorption capacity of salt ions through surface complexation. Meanwhile, the humic acid-iron oxide complex can also fix sodium ions through ion exchange and reduce the migration of salt to the surface.

[0020] (2) The present invention uses modified bentonite obtained by calcification-iron salt impregnation-humic acid composite modification process and compounded with acid-producing and salt-tolerant compound microbial agent. The compound microbial agent has a certain salt tolerance and can produce certain acidic substances through metabolism, thereby reducing the pH value of the soil. Furthermore, the modified bentonite, as the immobilization carrier of the compound microbial agent, can improve the attachment space of microorganisms, form a local microenvironment, and avoid the inhibitory effect of high external salt on bacterial metabolism.

[0021] (3) This invention forms a coupled ternary mechanism of physical adsorption + chemical modification + bioremediation through the synergistic effect of modified bentonite, leguminous green manure and compound microbial agent, which is particularly effective in improving moderately saline-alkali land in arid areas. Detailed Implementation

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0026] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] This invention provides a method for modifying bentonite, the specific steps of which include: S1. Calcification: Bentonite is impregnated in a 0.3-0.5M calcium chloride solution at a solid-liquid ratio of 1: (8-10) for 120-150 minutes. After impregnation, it is washed with deionized water until neutral, dried, and then ground through a 100-mesh sieve to obtain calcium-based bentonite. S2. Salt modification: The calcium-based bentonite is then impregnated in an iron salt solution with a concentration of 0.1~0.2M for 40~60 minutes to obtain salt-modified calcium-based bentonite. The salt-modified calcium-based bentonite is then dispersed in deionized water to form a suspension. S3. Humic acid modification: Humic acid is dissolved in water, and the pH is adjusted to 8-9 with sodium hydroxide solution to obtain a humic acid solution with a concentration of 5-8 g / L; the humic acid solution is then slowly added to the suspension, and the mixture is heated to 60-70°C for 1-1.5 h under stirring. S4. Aging: After standing for aging for 12-24 hours, filter, wash until neutral, and let the obtained solid dry naturally to obtain modified bentonite.

[0028] This invention first modifies bentonite by calcification to obtain calcium-based bentonite; then, the calcium-based bentonite is impregnated in an iron salt solution for salt modification to obtain salt-modified calcium-based bentonite; the salt-modified calcium-based bentonite is then dispersed in deionized water to form a suspension, and a humic acid solution is slowly added to the suspension. The reaction is carried out under stirring and heating conditions, and after static aging, modified bentonite is obtained; wherein, the iron ion concentration in the iron salt solution is 0.1~0.2M, and the impregnation time is 40~60min.

[0029] Natural bentonite has a layered structure and cation exchange capacity (CEC). In this embodiment of the invention, calcification modification can preferentially form Ca. 2+ Saturated structures help displace excess Na in the soil. +This process promotes the formation of aggregates. Then, immersion in iron salt solution can produce a flocculation effect through iron ion hydrolysis, enhancing bentonite's ability to fix salt ions. Simultaneously, iron, as a trace element, can provide plants with salt tolerance. Humic acid, containing active groups such as carboxyl and phenolic hydroxyl groups, can be modified onto the bentonite surface to complex salt ions, regulate soil pH, and serve as a carbon source to support microbial activity.

[0030] In this embodiment of the invention, the iron salt solution can be any soluble iron salt, including but not limited to ferric chloride solution, ferric sulfate solution, or ferric nitrate solution. In some optional embodiments of the invention, ferric chloride solution is selected as an example. The concentration of the iron salt solution should not be too high, and the soaking time should not be too long, otherwise all the calcium ions in step S1 will be displaced. Therefore, in this embodiment of the invention, the iron ion concentration in the iron salt solution is limited to 0.1~0.2M, and the soaking time is limited to 40~60min.

[0031] In some embodiments of the present invention, the method of calcification modification is as follows: Bentonite is impregnated in a calcium salt solution at a solid-liquid ratio of 1g:(8~10)mL for 120~150min. After impregnation, it is washed with deionized water, dried, and then ground through a 100-mesh sieve. The calcium salt solution is selected from calcium chloride or calcium nitrate solutions. The concentration of the calcium salt solution is 0.3~0.5M.

[0032] The solid-liquid ratio can be 1:8, 1:9, or 1:10, or any value within the range of 1:(8~10). As an example, this embodiment of the invention will only use 1:8 as an example for explanation.

[0033] The immersion time can be any value within 120 to 150 minutes. This embodiment of the invention uses 120 minutes as an example to describe the technical solution in detail.

[0034] The concentration of the calcium salt solution can be any concentration from 0.3 to 0.5 M. This embodiment of the invention uses 0.5 M as an example only.

[0035] In some embodiments of the present invention, the humic acid solution is prepared by: dissolving humic acid in water, adjusting the pH to 8-9 (e.g., 8 or 9, or any value within this range) with sodium hydroxide solution to obtain a humic acid solution with a concentration of 5-8 g / L (e.g., 6 g / L, or any concentration within this range); and / or, heating at a temperature of 60-70°C (e.g., 65°C or any temperature value within the range of 60-70°C); and the reaction time being 1-1.5 h (which can be 1.5 h, or any time value within the range of 1-1.5 h).

[0036] In some embodiments of the present invention, the static aging time is 12 to 24 hours, for example, it can be 24 hours, 12 hours or 36 hours, or any time value within this range.

[0037] A second aspect of the present invention also provides a modified bentonite, which is prepared by the above-described bentonite modification method.

[0038] A third aspect of the present invention also provides the application of modified bentonite in the preparation of soil conditioners for improving saline-alkali land.

[0039] The fourth aspect of the present invention provides a soil conditioner for improving saline-alkali land, comprising the above-mentioned modified bentonite and a compound microbial agent; the mass ratio of the modified bentonite to the compound microbial agent is 100:1 to 1.5.

[0040] The modified bentonite and the composite microbial agent can be mixed directly, or the modified bentonite can be impregnated in the bacterial solution of the composite microbial agent and then air-dried. After mixing, the microorganisms are immobilized in the pores of the modified bentonite, forming a local microenvironment. Humic acid provides nutrients for the microbial agent, promoting the reproduction and metabolism of the microorganisms.

[0041] In an optional embodiment, the composite microbial agent comprises Bacillus subtilis and Bacillus licheniformis in a mass ratio of 1:(1~2). Bacillus subtilis is highly salt-tolerant and can secrete organic acids to neutralize alkaline substances, lowering the soil pH. Simultaneously, it can activate the activity of protective enzymes such as SOD (superoxide dismutase) and POD (peroxidase) in plants, reduce the peroxidation product MDA (malondialdehyde), and enhance cellular stress resistance. Bacillus licheniformis can secrete extracellular polysaccharides and biofilms to encapsulate soil particles, forming aggregates, improving compacted structures, and enhancing soil permeability and aeration. It can also produce alkaline phosphatase and urease, decomposing organic matter to release nutrients such as phosphorus and nitrogen, alleviating fertility deficiency. Furthermore, osmotic regulators such as proline can assist plants in resisting salt stress and improve seed germination rates.

[0042] In an optional embodiment, the mass ratio of Bacillus subtilis and Bacillus licheniformis in the compound microbial agent is 1:1 or 1:2 (using purchased agents to ensure that the number of live bacteria also meets this ratio).

[0043] This invention provides a method for improving saline-alkali land. The method involves spreading crushed plant straw on the surface of the saline-alkali land, deep plowing, letting the land dry for one week, spreading a soil conditioner for improving saline-alkali land on the surface, plowing again, planting leguminous green manure, and returning the straw to the field after the green manure matures.

[0044] Specifically, there are no restrictions on the type of plant straw; for example, it can be corn straw, wheat straw, or legume green manure straw. The straw should be shredded using a straw crusher before being applied to the soil. Deep plowing refers to a tillage depth of ≥30cm. Deep plowing ensures that the straw penetrates deep into the soil, forming a straw barrier layer. The purpose of allowing the land to dry for a week is to allow the straw to decompose in the soil.

[0045] The raw materials used in the embodiments and comparative examples of this invention were all obtained through conventional commercial channels. Bacillus subtilis and Bacillus licheniformis were purchased inoculants, with Bacillus licheniformis being Genliduo purchased from JD.com and Bacillus subtilis being purchased from Jinan Shengyilong Chemical Technology Co., Ltd.

[0046] It should be noted that the technical means not described in detail in the embodiments of the present invention are all conventional technologies in the field and are not the key points of the invention, and will not be elaborated here.

[0047] Example 1 A modified bentonite, prepared by the following method: S1. Bentonite was impregnated in a 0.5M calcium chloride solution at a solid-liquid ratio of 1g:8mL for 120min. After impregnation, it was washed with deionized water until neutral, dried, and then ground through a 100-mesh sieve to obtain calcium-based bentonite. S2. Then, the calcium-based bentonite is immersed in a 0.1M ferric chloride solution for 50 minutes to obtain salt-modified calcium-based bentonite. The salt-modified calcium-based bentonite is then dispersed in deionized water to form a suspension. S3. Dissolve humic acid in water and adjust the pH to 8 with sodium hydroxide solution to obtain a humic acid solution with a concentration of 6 g / L; then slowly add the humic acid solution to the suspension (the volume ratio of humic acid solution to the suspension is 1:3), and heat to 65°C under stirring to carry out the reaction for 1.5 h. S4. After standing and aging for 24 hours, filter, wash with deionized water until neutral, and let the obtained solid dry naturally to obtain modified bentonite.

[0048] Example 2 A modified bentonite, differing from Example 1 only in that the concentration of the ferric chloride solution in S2 is 0.2M.

[0049] Example 3 A modified bentonite, differing from Example 1 only in that the concentration of the ferric chloride solution in S2 is 0.1M.

[0050] Example 3 A modified bentonite, differing from Example 1 only in that the reaction time in S2 is 40 min.

[0051] Example 4 A modified bentonite, differing from Example 1 only in that the reaction time in S2 is 60 min.

[0052] Comparative Example 1 A modified bentonite, differing from Example 1 only in that the concentration of the ferric chloride solution in S2 is 0.3M.

[0053] Comparative Example 2 A modified bentonite, prepared by the following method: S1. Bentonite was impregnated in a 0.5M calcium chloride solution at a solid-liquid ratio of 1:8 for 120 minutes. After impregnation, it was washed with deionized water until neutral, dried, and ground through a 100-mesh sieve to obtain calcium-based bentonite. The calcium-based bentonite was then dispersed in deionized water to form a suspension. S2. Dissolve humic acid in water, adjust the pH to 8 with sodium hydroxide solution to obtain a humic acid solution with a concentration of 6 g / L; then slowly add the humic acid solution to the suspension, heat to 65°C under stirring to carry out the reaction, and the reaction time is 1.5 h; S3. After standing and aging for 24 hours, filter, wash with deionized water until neutral, and let the obtained solid dry naturally to obtain modified bentonite.

[0054] Comparative Example 3 A modified bentonite, prepared by the following method: S1. Natural bentonite is impregnated in a 0.1M ferric chloride solution for 50 minutes to obtain salt-modified bentonite, which is then dispersed in deionized water to form a suspension. S2. Dissolve humic acid in water and adjust the pH to 8 with sodium hydroxide solution to obtain a humic acid solution with a concentration of 6 g / L; then slowly add the humic acid solution to the suspension and heat to 65°C under stirring to carry out the reaction for 1.5 h. S3. After standing and aging for 24 hours, filter, wash with deionized water until neutral, and let the obtained solid dry naturally to obtain modified bentonite.

[0055] Application examples A soil conditioner for improving saline-alkali land includes modified bentonite and a compound microbial agent; wherein the compound microbial agent is Bacillus subtilis and Bacillus licheniformis.

[0056] Different soil conditioners were used to improve saline-alkali land. The improvement method was as follows: a saline-alkali land plot was selected as the experimental area. Crushed plant straw was spread on the surface of the saline-alkali land (soil pH 9.3) at a rate of 500 kg / mu. The land was deep-plowed (plowing depth 40 cm), and after the land was left to dry for 1 week, soil conditioner was spread on the surface (100 kg / mu). The land was plowed again, and then alfalfa was planted in the conventional way. The sowing time was July 20. After the alfalfa matured, the straw was returned to the field. Different treatment groups used different soil conditioners, and the specific combinations are shown in Table 1. For ease of description, the modified bentonite prepared in Examples 1-4 and Comparative Examples 1-3 are designated as A1-A7; the compound microbial agent with a mass ratio of Bacillus subtilis and Bacillus licheniformis of 1:1 is designated as B1; the compound microbial agent with a mass ratio of Bacillus subtilis and Bacillus licheniformis of 1:2 is designated as B2; the microbial agent consisting solely of Bacillus subtilis is designated as B3; and the microbial agent consisting solely of Bacillus licheniformis is designated as B4. (e.g., A1B1) 1.5 The composite microbial agent prepared in Example 1 consists of 100 parts modified bentonite and 1.5 parts of Bacillus subtilis and Bacillus licheniformis in a 1:1 mass ratio, and so on.

[0057] The test area for each modifier was 66.7m. 2 Each plot had three replicates. The blank control group was only covered with crushed plant straw, and the rest was the same as the experimental area.

[0058] After the green manure was returned to the field, the soil was left to dry for one week. The soil physicochemical properties were then tested. In each experimental area, 7 points were sampled at the same location using a soil sampler. The sampling depth was 15cm from the top layer of the soil. The soil was allowed to air dry naturally. The statistical results of the average test values ​​are shown in Table 1.

[0059] The alfalfa coverage rate is calculated as (covered area / total area) × 100%. Soil pH and total salinity were measured in accordance with NY / T 1121.2-2006 "Soil Testing Part 2: Determination of Soil pH"; soil alkalinity was measured in accordance with LY / T 1249-1999 "Calculation of Soil Alkalinity".

[0060] Table 1

[0061] Table 2

[0062] Table 3

[0063] Table 4

[0064] As can be seen from Tables 1-4 above, the modified bentonite combined with the composite microbial agent in the embodiments of the present invention can significantly improve the improvement effect of moderate to severe saline-alkali land. However, the effect of bentonite combined with a single microbial species or bentonite obtained by omitting the salt modification or calcification steps and then combined with the composite microorganism is far inferior to the technical solution of the present invention.

[0065] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for modifying bentonite, characterized in that, First, bentonite is modified by calcification to obtain calcium-based bentonite; The calcium-based bentonite is then impregnated in an iron salt solution for salt modification to obtain salt-modified calcium-based bentonite. The salt-modified calcium-based bentonite is then dispersed in deionized water to form a suspension. Humic acid solution is then slowly added to the suspension, and the reaction is carried out under stirring and heating conditions. After standing and aging, modified bentonite is obtained. The iron ion concentration in the iron salt solution is 0.1~0.2M, and the impregnation time is 40~60min.

2. The modification method according to claim 1, characterized in that, The method of calcification modification is as follows: Bentonite is impregnated in a calcium salt solution at a solid-liquid ratio of 1g:(8~10)mL for 120~150min. After impregnation, it is washed with deionized water, dried, and then ground through a 100-mesh sieve. The calcium salt solution is selected from calcium chloride or calcium nitrate solutions. The concentration of the calcium salt solution is 0.3~0.5M.

3. The modification method according to claim 1, characterized in that, The humic acid solution is prepared by dissolving humic acid in water, adjusting the pH to 8-9 with sodium hydroxide solution to obtain a humic acid solution with a concentration of 5-8 g / L; and / or heating at a temperature of 60-70°C; and the reaction time is 1-1.5 h.

4. The modification method according to claim 1, characterized in that, The static aging time is 12~24h.

5. A modified bentonite, characterized in that, It is prepared by the bentonite modification method according to any one of claims 1 to 4.

6. The use of the modified bentonite as described in claim 5 in the preparation of a soil conditioner for improving saline-alkali land.

7. A soil conditioner for improving saline-alkali land, characterized in that, It includes the modified bentonite and composite microbial agent as described in claim 5; the mass ratio of the modified bentonite and the composite microbial agent is 100:1~1.

5.

8. The soil conditioner for improving saline-alkali land according to claim 7, characterized in that, The compound microbial agent includes Bacillus subtilis and Bacillus licheniformis in a mass ratio of 1:(1~2).

9. The application of the soil conditioner for improving saline-alkali land as described in claim 7 or 8.

10. A method for improving saline-alkali land, characterized in that, After spreading crushed plant straw on the surface of saline-alkali land, deep plowing, and drying the land for one week, apply the soil conditioner for improving saline-alkali land as described in claim 7 or 8 to the surface, plow again, and then plant leguminous green manure. After the green manure matures, return the straw to the field.

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