A method for reducing salt content of saline-alkali soil and improving soil

Abstract

The application belongs to the field of soil improvement, and particularly relates to a method for reducing salt content and improving soil of coastal saline-alkali soil, which comprises the following steps: uniformly mixing a soil conditioner into soil and deep ploughing; the preparation method of the soil conditioner comprises the following steps: uniformly mixing and crushing 30-40 parts of modified coal gangue, 10-15 parts of straw powder, 10-15 parts of animal manure and 0.5-1 part of microbial agent according to mass fraction, stirring in a capsule wall liquid, and obtaining a microencapsulated soil conditioner through freeze-drying. The coal gangue, straw powder, animal manure and microbial agent are prepared into a microcapsule structure, have a certain slow-release effect, can rapidly reduce the salt content of soil, increase the repelling ability of plants to sodium ions and the absorption ability of plants to calcium ions, improve the tolerance of plants to saline-alkali, effectively inhibit the toxicity of saline-alkali to plants, improve the enzyme activity of soil, and improve the yield and quality of crops.

Description

Technical Field

[0001] This invention relates to the field of soil improvement, specifically to a method for reducing salinity and improving saline-alkali soil. Background Technology

[0002] Saline-alkali soil areas have fragile ecosystems and low environmental carrying capacity, often referred to as "the skin disease of the earth," severely hindering local economic and social development. Improving saline-alkali soil can be achieved through methods such as irrigation, agriculture, physical methods, and chemical methods, gradually reducing the soil salinity in the crop root zone to meet desalination standards. Based on my research, the main desalination technologies used in coastal tidal flat areas include the following:

[0003] Rainwater / saline water leaching desalination technology utilizes rainfall or low-salinity water to irrigate saline-alkali soils, allowing soluble salts in the soil to infiltrate or be expelled with the water. This technology is simple, easy to implement, and low-cost, but its disadvantages include the need for large amounts of freshwater resources, limitations imposed by climate and water source conditions, and inconsistent effectiveness. Biological desalination technology utilizes salt-tolerant plants or microorganisms to absorb, transform, or degrade salts in the soil. This technology enables the ecological cycle of soil salinity, improving soil fertility and the ecological environment, but its disadvantages include a longer time frame, slower results, and dependence on the types and quantities of organisms involved. Therefore, there is an urgent need for a method to reduce salinity and improve saline-alkali soils to address the severe soil salinization and land scarcity problems in coastal areas. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for reducing salinity and improving soil in saline-alkali soil.

[0005] To achieve the objectives of this invention, the technical solution adopted is as follows:

[0006] A method for reducing salinity and improving soil in coastal saline-alkali soil includes the following steps: uniformly mixing a soil conditioner into the soil and then tilling it; the preparation method of the soil conditioner includes: mixing and crushing 30-40 parts modified coal gangue, 10-15 parts straw powder, 10-15 parts animal manure, and 0.5-1 parts microbial inoculant by mass fraction, then adding the mixture into a capsule wall liquid and stirring, followed by freeze-drying to obtain a microencapsulated soil conditioner.

[0007] Furthermore, the preparation method of the capsule wall fluid is as follows: 15-18g of gelatin is mixed evenly with 100mL of deionized water to obtain a gelatin solution; 6-8g of chitosan is mixed evenly with 100mL of deionized water and then added dropwise to acetic acid to obtain a chitosan solution; the gelatin solution and the chitosan solution are mixed at a volume ratio of 1:1 to obtain the capsule wall fluid.

[0008] Furthermore, the microbial agent includes Bacillus megaterium, Bacillus subtilis, and Bacillus colloidis.

[0009] Furthermore, the ratio of Bacillus megaterium, Bacillus subtilis, and Bacillus colloidis is 4–5:2–3:2–3.

[0010] Furthermore, the tillage depth is 30cm.

[0011] Furthermore, the application rate of the soil conditioner is 15 kg per acre.

[0012] Furthermore, the preparation method of the modified coal gangue includes: crushing the coal gangue and subjecting it to a hydrothermal reaction; mixing the hydrothermal reaction mixture evenly with acid solution and subjecting it to ultrasonic treatment; performing skeleton dealuminization; and drying the mixture to obtain the modified coal gangue.

[0013] Furthermore, the hydrothermal modification temperature is 120–150℃, and the reaction time is 10–12 h.

[0014] Furthermore, the acid solution is hydrochloric acid, the concentration of the hydrochloric acid is 0.2 mol / L, and the amount of acid solution used is enough to cover and soak the coal gangue.

[0015] Furthermore, the acid immersion and ultrasonic treatment time is 20-25 hours.

[0016] Furthermore, a method for reducing salinity and improving saline-alkali soil includes the following steps: uniformly mixing a soil conditioner into the soil, tilling the soil to a depth of 30cm, and applying 15kg of the soil conditioner per acre.

[0017] The preparation method of the soil conditioner includes: crushing coal gangue and subjecting it to a hydrothermal reaction; mixing the hydrothermal reaction mixture evenly with an acid solution and then subjecting it to ultrasonic treatment to remove aluminum from the skeleton; and drying the mixture to obtain modified coal gangue; the hydrothermal modification temperature is 120-150℃, and the reaction time is 10-12h; the acid solution is hydrochloric acid with a concentration of 0.2mol / L, and the amount of acid solution used is sufficient to cover and soak the coal gangue; the soaking time and ultrasonic treatment time are 20-25h.

[0018] The modified coal gangue (30-40 parts), straw powder (10-15 parts), animal manure (10-15 parts), and microbial agent (0.5-1 parts) are mixed evenly and pulverized. This mixture is then added to the capsule wall liquid and stirred. After freeze-drying, a microencapsulated soil conditioner is obtained. The capsule wall liquid is prepared as follows: 15-18g of gelatin is mixed evenly with 100mL of deionized water to obtain a gelatin solution; 6-8g of chitosan is mixed evenly with 100mL of deionized water and then added dropwise to acetic acid to obtain a chitosan solution; the gelatin solution and chitosan solution are mixed at a volume ratio of 1:1 to obtain the capsule wall liquid. The microbial agent includes Bacillus megaterium, Bacillus subtilis, and Bacillus colloidioides; the ratio of Bacillus megaterium, Bacillus subtilis, and Bacillus colloidioides is 4-5:2-3:2-3.

[0019] Beneficial effects

[0020] This invention addresses the problems of high salinity, rapid salt return, poor structure, and low organic matter content in coastal saline-alkali soils by providing a method for reducing salinity and improving soil in coastal saline-alkali soils. By using soil conditioners to improve soil structure, it can rapidly reduce soil salinity and accelerate the cultivation of soil organic matter and the formation of aggregates.

[0021] Soil enzymes are a collective term for various enzymes present in soil and are one of the components of soil. Soil enzymes are biological catalysts in soil, playing an important role in the material cycle of wetland ecosystems and reflecting the direction and intensity of soil biochemical processes. Phosphatases are important hydrolytic enzymes in soil, promoting the decomposition of organophosphorus compounds. The level of phosphatase affects the rate of soil material cycling and is an important indicator of soil health.

[0022] Coal gangue is a residue generated during coal mining and washing, accounting for 15% to 20% of raw coal production. It is one of the largest industrial solid wastes emitted in my country and is considered "industrial waste," "public nuisance," and "waste." Currently, the comprehensive utilization of coal gangue mainly focuses on power generation, building material production, underground backfilling, and goaf backfilling. The main component of coal gangue is SiO2, and it contains a large number of trace elements needed by crops, such as Zn, K, and Ca compounds; heavy metals harmful to crops, such as Cu, Hg, Cr, and Pb, are all below agricultural control standards.

[0023] Modified coal gangue is loose and porous with high porosity and high content of needle-like and flaky particles. It also has good adsorption properties and dispersibility, increased water permeability, and significantly improved efficiency of water leaching of salt and alkali ions. The ability of the topsoil to return salt is weakened. Using modified coal gangue as a component of soil conditioner can achieve good desalination effect, improve soil structure, and enhance soil enzyme activity.

[0024] Straw powder is a carbon-based soil conditioner made from agricultural waste. It can help the soil form a good granular structure, which can retain moisture and nutrients, reduce soil salinity, provide nutrients needed by plants, enhance the salt resistance of plants, realize the ecological cycle of soil salinity, utilize waste resources, and reduce costs.

[0025] By preparing coal gangue, straw powder, animal manure, and microbial agents into microcapsule structures, a certain slow-release effect can be achieved, which can rapidly reduce soil salinity, increase the plant's ability to repel sodium ions and absorb calcium ions, improve the plant's tolerance to salt and alkali, effectively inhibit the toxicity of salt and alkali to plants, increase soil enzyme activity, and improve crop yield and quality. Attached Figure Description

[0026] Figure 1 The images show a comparison of soil before and after improvement using the method described in this invention (the top image is before improvement, and the bottom image is after improvement). Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following description will be provided in conjunction with the embodiments of the present invention.

[0028] Example 1

[0029] A method for reducing salinity and improving saline-alkali soil includes the following steps: uniformly mixing a soil conditioner into the soil, tilling the soil to a depth of 30cm, and applying 15kg of the soil conditioner per acre.

[0030] The preparation method of the soil conditioner includes: crushing coal gangue and subjecting it to a hydrothermal reaction; mixing the hydrothermal reaction mixture with an acid solution and then subjecting it to ultrasonic treatment to remove aluminum from the skeleton; and drying the mixture to obtain modified coal gangue. The hydrothermal modification temperature is 120–150℃, and the reaction time is 10–12 h. The acid solution is hydrochloric acid with a concentration of 0.2 mol / L, and the amount of acid solution used is sufficient to cover and soak the coal gangue. The soaking and ultrasonic treatment time is 20–25 h.

[0031] The modified coal gangue (40 parts), straw powder (15 parts), animal manure (15 parts), and microbial agent (0.2 parts) were mixed evenly and pulverized. This mixture was then added to the capsule wall liquid and stirred. After freeze-drying, a microencapsulated soil conditioner was obtained. The capsule wall liquid was prepared as follows: 15g of gelatin was mixed evenly with 100mL of deionized water to obtain a gelatin solution; 6g of chitosan was mixed evenly with 100mL of deionized water and then added dropwise to acetic acid to obtain a chitosan solution; the gelatin solution and chitosan solution were mixed at a volume ratio of 1:1 to obtain the capsule wall liquid. The microbial agent included *Bacillus megaterium*, *Bacillus subtilis*, and *Bacillus colloidioides*; the ratio of *Bacillus megaterium*, *Bacillus subtilis*, and *Bacillus colloidioides* was 5:2:3.

[0032] Comparative Example 1

[0033] A method for reducing salinity and improving soil in saline-alkali soil. The difference between this embodiment and Embodiment 1 is that modified coal gangue was not added.

[0034] Comparative Example 2

[0035] A method for reducing salinity and improving soil in saline-alkali soil. The difference between this embodiment and Embodiment 1 is that straw powder is not added.

[0036] Comparative Example 3

[0037] A method for reducing salinity and improving soil in saline-alkali soil. The difference between this embodiment and Embodiment 1 is that animal manure was not added.

[0038] Comparative Example 4

[0039] A method for reducing salinity and improving soil in saline-alkali soil. The difference between this embodiment and Embodiment 1 is that no microbial inoculant was added.

[0040] Comparative Example 5

[0041] A method for reducing salinity and improving soil in saline-alkali soil. The difference between this embodiment and Embodiment 1 is that unmodified coal gangue is used.

[0042] Comparative Example 6

[0043] A method for reducing salinity and improving saline-alkali soil. The difference between this embodiment and Embodiment 1 is that the soil conditioner is not microencapsulated.

[0044] Comparative Example 7

[0045] A method for reducing salinity and improving saline-alkali soil. The difference between this embodiment and embodiment 1 is that no tillage is performed, and only a soil conditioner is sprinkled on the soil surface, with the same dosage as in embodiment 1.

[0046] Comparative Example 8

[0047] A method for reducing salinity and improving saline-alkali soil. The difference between this embodiment and Embodiment 1 is that ultrasonic treatment was not used when modifying coal gangue.

[0048] Example 2

[0049] The selected saline-alkali land is located in Jinhai Farm, Dafeng District, Yancheng City, Jiangsu Province. This area is a typical sandy coastal wetland with a subtropical humid monsoon climate, characterized by four distinct seasons and rainfall concentrated mainly from June to August. The soil pH is 8.2, organic matter content is 2.1 g / kg, and the soil salinity in the 0–20 cm topsoil layer is 1.22%. Soil phosphatase activity is 0.04 mg / g. -1 ·d -1 The lack of soil nutrients, high soil salinity, and low soil organic matter content are the main obstacles to crop production in this area.

[0050] Ten groups of plots with similar soil conditions were selected from the aforementioned tidal flat areas, with three replicates in each group. One group was selected as a control and received no treatment. The remaining nine groups underwent soil improvement using the methods described in Example 1 and Comparative Examples 1-8, respectively. After six months, the soil salt content was measured, and the soil phosphatase activity in the plots was detected. The results are as follows:

[0051]

[0052] The above results demonstrate that the desalination method described in this invention can achieve good desalination results. By incorporating the soil conditioner into the soil and then tilling it, the soil structure is improved, soil capillaries are broken, a salt-suppressing layer is constructed, the accumulation of soil salts on the surface is effectively inhibited, the salinity of the topsoil is effectively reduced, the soil physicochemical properties are improved, and the soil organic matter and nutrient content are increased. Modification treatment of coal gangue enhances its adsorption performance, giving it better adsorption capacity and dispersibility, increasing water permeability, and thus achieving a better desalination effect. It also effectively enhances the activity of soil enzymes.

[0053] Example 3

[0054] The same area described in Example 2 was selected, and plots with similar soil conditions were divided into 5 groups, with 3 replicates in each group. The soil in each group was improved using the method described in Example 1, with the same amount of soil conditioner as in Example 1. The only difference was the raw material used to prepare the microbial agent. After 6 months, the salt content in the soil was counted, and the soil phosphatase activity in the plots was tested. The results are as follows:

[0055]

[0056]

[0057] The above data shows that the microbial agent used in this invention can achieve good technical results.

[0058] Example 4

[0059] The same area described in Example 2 was selected, and plots with similar soil conditions were divided into 5 groups, with 3 replicates in each group. The soil in each group was improved using the method described in Example 1, with the only difference being the amount of soil conditioner applied. After 6 months, the salt content in the soil was counted, and the soil phosphatase activity in the plots was measured. The results are as follows:

[0060]

[0061] The above data shows that a soil conditioner application rate of 15 kg per acre can achieve a balance between cost and technical effectiveness.

Claims

1. A method for reducing salinity and improving soil in coastal saline-alkali soils, characterized in that, Includes the following steps: The soil conditioner is evenly mixed into the soil and then tilled. The preparation method of the soil conditioner includes: mixing 30-40 parts of modified coal gangue, 10-15 parts of straw powder, 10-15 parts of animal manure and 0.5-1 parts of microbial agent by mass fraction, crushing them, adding them into the capsule wall liquid and stirring, and freeze-drying to obtain the microencapsulated soil conditioner. The preparation method of the capsule wall fluid is as follows: 15-18g of gelatin is mixed evenly with 100mL of deionized water to obtain a gelatin solution; 6-8g of chitosan is mixed evenly with 100mL of deionized water and then added dropwise to acetic acid to obtain a chitosan solution; the gelatin solution and the chitosan solution are mixed at a volume ratio of 1:1 to obtain the capsule wall fluid. The method for preparing the modified coal gangue includes: crushing the coal gangue and subjecting it to a hydrothermal reaction; mixing the hydrothermal reaction mixture with acid solution and then subjecting it to ultrasonic treatment; performing skeleton dealuminization; and drying the mixture to obtain the modified coal gangue. The hydrothermal modification temperature is 120–150°C, and the reaction time is 10–12 h. The microbial agent includes Bacillus megaterium, Bacillus subtilis, and Bacillus colloidis; the ratio of Bacillus megaterium, Bacillus subtilis, and Bacillus colloidis is 4-5:2-3:2-3.

2. The method for desalination and soil improvement of coastal saline-alkali soil according to claim 1, characterized in that, The tillage depth is 30cm.

3. The method for desalination and soil improvement of coastal saline-alkali soil according to claim 1, characterized in that, The application rate of the soil conditioner is 15 kg per mu.

4. The method for desalination and soil improvement of coastal saline-alkali soil according to claim 1, characterized in that, The acid solution is hydrochloric acid, the concentration of the hydrochloric acid is 0.2 mol / L, and the amount of acid solution used is enough to cover and soak the coal gangue.

5. The method for reducing salinity and improving soil in coastal saline-alkali soil according to claim 1, characterized in that, The acid immersion and ultrasonic treatment time is 20-25 hours.

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