A saline-alkali soil improvement agent and a preparation method thereof

Abstract

The application relates to the field of agricultural saline-alkali soil improver, in particular to a saline-alkali soil improver and a preparation method thereof. The saline-alkali soil improver is prepared from raw materials including inorganic metal salt 30-50 parts by mass, modified desulfurization gypsum 20-30 parts by mass, amino acid 1-10 parts by mass, polypeptide 1-5 parts by mass, microbial agent 1-5 parts by mass, modified chitosan 10-20 parts by mass and auxiliary agent 5-30 parts by mass. The saline-alkali soil improver prepared by the application not only has good saline-alkali soil improvement effect and crop yield increasing effect, effectively improves soil structure and increases soil nutrients, but also can greatly reduce water consumption, has strong self-stability, can avoid the strict storage and transportation requirements of the existing improver, increases the use cycle and service life, and has very excellent market prospect.

Description

Technical Field

[0001] This application relates to the field of agricultural saline-alkali soil conditioners, and more particularly to a saline-alkali soil conditioner and its preparation method. Background Technology

[0002] With the continuous growth of my country's total population, the per capita arable land area has been declining year by year. Moreover, improper measures such as excessive fertilization have led to increasingly serious soil salinization, and the area of ​​saline-alkali land has been increasing year by year. Soil salinization refers to the process by which salts in the bottom layer of soil or groundwater rise to the surface with capillary water, and after the water evaporates, the salts accumulate in the topsoil. It is the phenomenon or process of soluble salts accumulating in the soil surface.

[0003] For the improvement of saline-alkali soils, methods generally fall into three main categories: chemical, physical, and biological. Physical improvement mainly relies on processes such as irrigation to leach salt and underground drainage. While physical methods are effective at washing and controlling salt levels, they cannot effectively reduce soil alkalinity or improve soil compaction. Biological improvement mainly relies on planting salt-tolerant and salt-absorbing plants, but its effects are unstable and the overall improvement cycle is long, which is not conducive to efficient saline-alkali soil improvement programs. Chemical amendments, on the other hand, have advantages such as low cost, rapid effect, and flexible and adjustable formulations, and have become the main method for saline-alkali soil improvement in recent years.

[0004] Existing saline-alkali soil conditioners primarily rely on desulfurized gypsum and microbial agents / amino acids / peptides for their effectiveness. The calcium ions in the desulfurized gypsum react with carbonate and bicarbonate ions in the soil to exchange for sodium ions, thereby reducing soil pH and alkalinity. Meanwhile, the microbial agents / amino acids / peptides promote aggregate formation, enhancing soil physical structure, making the soil looser, and improving aeration and water retention, thus providing a better growth environment and necessary nutrients for plant roots. However, conditioners based on these components require significant water usage, and in areas with high groundwater levels, they may further increase soil salinity. Furthermore, the presence of microbial agents / amino acids / peptides greatly affects the stability of the conditioner, making storage and transportation extremely demanding for some types, significantly impacting their application.

[0005] Therefore, to solve the above problems, this application provides a saline-alkali land conditioner and its preparation method. The saline-alkali land conditioner prepared by this application not only has a good effect on improving saline-alkali land and increasing crop yield, effectively improving soil structure and increasing soil nutrients, but also significantly reduces water consumption and has extremely strong self-stability. It can avoid the stringent storage and transportation requirements of existing conditioners, increase the service life and have excellent market prospects. Summary of the Invention

[0006] To address the aforementioned problems, the first aspect of this application provides a saline-alkali land conditioner, comprising, by weight, the following raw materials: 30-50 parts of inorganic metal salt, 20-30 parts of modified desulfurized gypsum, 1-10 parts of amino acids, 1-5 parts of polypeptides, 1-5 parts of microbial inoculant, 10-20 parts of modified chitosan, and 5-30 parts of additives.

[0007] As a preferred embodiment, the mass ratio of the inorganic metal salt, modified desulfurized gypsum, and modified chitosan is (35~45):(22~26):(15~18).

[0008] As a preferred embodiment, the mass ratio of the inorganic metal salt, modified desulfurized gypsum, and modified chitosan is (36~40):25:16.

[0009] As a preferred embodiment, the inorganic metal salt is at least one selected from superphosphate, aluminum sulfate, ferrous sulfate, calcium sulfate, calcium chloride, potassium aluminum sulfate, and potassium dihydrogen phosphate.

[0010] As a preferred embodiment, the inorganic metal salt is a combination of superphosphate, calcium chloride, and potassium aluminum sulfate.

[0011] As a preferred embodiment, the mass ratio of superphosphate, calcium chloride and potassium aluminum sulfate is (5~10):(20~25):(3~6).

[0012] As a preferred embodiment, the mass ratio of superphosphate, calcium chloride and potassium aluminum sulfate is (6~9):(22~25):(4~5).

[0013] As a preferred embodiment, the preparation method of the modified desulfurized gypsum includes the following steps: S1: Add the desulfurized gypsum to deionized water, then add silane coupling agent, polyethylene glycol and branched starch in sequence, and heat to 50~60℃ and stir continuously for 1~2h; S2: Then, while continuing to stir, add a mixed deionized aqueous solution of tetraethyl orthosilicate and ammonia, and then continue to stir for 60~80min; S3: After stirring, filter the product and place it in a ventilated oven to dry at 60~80℃ for 3~4h, and the product is obtained.

[0014] As a preferred embodiment, the mass ratio of the desulfurized gypsum, silane coupling agent, polyethylene glycol and amylopectin is (3~5):(0.1~0.2):(0.2~0.5):(1~2).

[0015] As a preferred embodiment, the mass ratio of the desulfurized gypsum, silane coupling agent, polyethylene glycol, and amylopectin is 4:0.2:0.4:1.2.

[0016] As a preferred embodiment, the mass ratio of the desulfurized gypsum to tetraethyl orthosilicate is (3~5):(0.1~0.5).

[0017] As a preferred embodiment, the mass ratio of the tetraethyl orthosilicate to ammonia is (1~5):(0.5~2).

[0018] This application uses modified desulfurized gypsum as one of the main raw materials of a saline-alkali land amendment. Besides effectively improving the saline-alkali improvement effect of the amendment, it also effectively enhances the overall water absorption and retention rate of the soil. The modified desulfurized gypsum can form a good modified composite layer on its surface. This composite layer creates a smooth surface with high surface energy and multiple surface groups, which can compensate for and repair the multi-peaked, valley-and-gully surface of the desulfurized gypsum, thereby promoting the formation of a surface hydration layer. This accelerates the free dispersion of gypsum in the water system after the addition of water, enhances the hydrolytic dispersion effect of gypsum, and significantly reduces water usage. Furthermore, in subsequent use, it can adsorb water in the soil through its multiple hydrophilic surface groups and retain water through strong hydrogen bonds with water, thus maintaining excellent water absorption and retention rates while achieving good saline-alkali land improvement.

[0019] As a preferred embodiment, the amino acid is a complex composition of arginine and glutamic acid.

[0020] As a preferred embodiment, the preparation method of the complex composition of arginine and glutamic acid includes the following steps: zinc acetate is mixed with arginine and glutamic acid and added to a reaction vessel and dissolved and mixed with sufficient deionized water. The pH is controlled at 5-6 and the temperature is raised to 60-65°C. The reaction is maintained at this temperature for 3-4 hours. After the reaction is completed, the product is passed through a 200-400 mesh sieve and filtered to remove impurities.

[0021] As a preferred embodiment, the mass ratio of zinc acetate, arginine and glutamic acid is (1.5~2):(1~2):(3~4).

[0022] As a preferred embodiment, the mass ratio of zinc acetate, arginine, and glutamic acid is 1.8:1.5:4.

[0023] As a preferred embodiment, the polypeptide is a fish protein peptide.

[0024] As a preferred embodiment, the mass ratio of the amino acid, polypeptide, and microbial agent is (3~6):(2~4):(1~3).

[0025] As a preferred embodiment, the mass ratio of the amino acid, polypeptide, and microbial agent is (4~4.5):(2~3):(1.5~2).

[0026] As a preferred embodiment, the microbial agent is EM bacteria.

[0027] As a preferred embodiment, the preparation method of the modified chitosan includes the following steps: S1: Chitosan, carboxylic acid, and silane coupling agent are mixed and added to deionized water, heated to 40-50℃, and reacted at this temperature for 0.5-1.5h. After the reaction is completed, sodium hydroxide is added to adjust the pH to 8-9 to obtain pretreated chitosan; S2: Pretreated chitosan and ammonia are mixed and added to deionized water to obtain a mixed solution for later use; S3: Aluminum hydroxide and terephthalic acid are added to deionized water, and the mixture is heated to 200-210℃ under a pressure of 2.2MPa for 16-24h. After the reaction is completed, the mixture is cooled, centrifuged, filtered, and washed with ethanol to obtain particle products; S4: The particle products and the mixed solution are ultrasonically mixed and reacted at 60-85℃ and 400-600W. After the reaction is completed, the product is obtained.

[0028] As a preferred embodiment, the mass ratio of chitosan, carboxylic acid, and silane coupling agent is (3~5):(0.5~1):(0.1~0.3).

[0029] As a preferred embodiment, the mass ratio of the pretreated chitosan, aluminum hydroxide and terephthalic acid is (2~3):(1.5~2):(0.5~1).

[0030] As a preferred embodiment, the mass ratio of the pretreated chitosan, aluminum hydroxide, and terephthalic acid is 2.5:1.8:0.6.

[0031] As a preferred embodiment, the ultrasonic oscillation mixing reaction time is 2~2.5h.

[0032] As a preferred embodiment, the product after the ultrasonic oscillation mixing reaction is passed through a 1500-2000 mesh sieve.

[0033] The modified chitosan material added in this application significantly enhances the system stability of the soil conditioner, thereby avoiding excessively high storage and transportation conditions. Furthermore, it helps to enhance the overall water absorption and retention capacity of the soil. The modified chitosan effectively forms multi-microporous composite particles with high adsorption capacity. These particles not only serve as reliable adsorption carriers for peptides, amino acid complexes, and microbial agents within the system, preventing excessive activity and contact reactions between these substances under high-activity conditions and enhancing steric hindrance, but also absorb large amounts of water during use through the microporous structure of the composite particles. This water remains stable in the soil at the critical temperature, thus significantly increasing the total surface area of ​​contact between the conditioner and the soil, thereby greatly enhancing the effect and improving overall performance.

[0034] As a preferred embodiment, the additives are polyoxyethylene ethers, synergists, and organic powders.

[0035] As a preferred embodiment, the mass ratio of the polyoxyethylene ether, synergist and organic powder is (5~8):(3~5):(10~15).

[0036] As a preferred embodiment, the mass ratio of the polyoxyethylene ether, synergist, and organic powder is 6:4:12.

[0037] As a preferred embodiment, the polyoxyethylene ether is lauryl alcohol polyoxyethylene ether or cetearyl alcohol polyoxyethylene ether.

[0038] As a preferred embodiment, the polyoxyethylene ether is lauryl alcohol polyoxyethylene ether.

[0039] As a preferred embodiment, the synergist is at least one of carrageenan, pectin, gelatin, and polyvinyl alcohol.

[0040] As a preferred embodiment, the synergist is polyvinyl alcohol with a degree of alcoholysis of 80-95%.

[0041] As a preferred embodiment, the organic powder is at least one of rice husk powder, jujube kernel powder, peanut shell powder, wheat bran powder, and straw powder.

[0042] As a preferred embodiment, the organic powder is rice husk powder or jujube kernel powder.

[0043] The second aspect of this application provides a method for preparing the above-mentioned saline-alkali land conditioner. The preparation method includes the following steps: heating inorganic metal salt, modified desulfurized gypsum, amino acids, polypeptides, microbial agents, modified chitosan, and additives in a high-speed mixer to 40~50℃ and stirring at 200~300r / min until uniformly mixed; adding the mixed material to a granulator and granulating it to the desired particle size to obtain the final product.

[0044] The beneficial effects of this application are:

[0045] 1. The saline-alkali soil conditioner provided in this application not only has a good effect on improving saline-alkali soil and increasing crop yield, but also effectively improves soil structure and increases soil nutrients. It can also significantly reduce water usage and has extremely strong self-stability. It can avoid the strict storage and transportation requirements required by existing conditioners, increase the service life and have excellent market prospects.

[0046] 2. The saline-alkali land conditioner provided in this application uses modified desulfurized gypsum as one of the main raw materials. In addition to effectively improving the saline-alkali improvement effect of the conditioner, it can also effectively improve the overall effect of the conditioner on soil water absorption and retention. The modified desulfurized gypsum can form a good modified composite layer on its surface. The presence of this composite layer can form a smooth surface with high surface energy and multiple surface groups, which can compensate for and repair the multi-peak and valley surface of the desulfurized gypsum. On the other hand, in subsequent use, it can adsorb water in the soil through its multiple surface hydrophilic groups and retain water through strong hydrogen bonding with water, thereby maintaining excellent water absorption and retention under good saline-alkali land improvement effect.

[0047] 3. The saline-alkali land conditioner provided in this application has a modified chitosan substance that can significantly enhance the system stability of the conditioner itself. The modified chitosan can actually form a composite particle with multiple micropores and high adsorption capacity. The presence of this particle can not only serve as a reliable adsorption carrier for peptides, amino acid complexes and microbial agents in the system, but also avoid the excessive activity of the above substances and their contact reactions in a high-activity environment, thereby enhancing steric hindrance.

[0048] 4. The saline-alkali soil conditioner provided in this application contains modified chitosan substances that help enhance the overall water absorption and retention effect of the soil. When used, it absorbs a large amount of water through the adsorption effect of the micropores of the composite particle skeleton, and the water can be kept in the soil at the limit temperature, thus fixing the water very stably. It can also increase the total surface area of ​​contact between the conditioner and the soil, thereby greatly enhancing the effect and improving the overall performance. Detailed Implementation

[0049] The following will further illustrate and demonstrate the technical solutions described above in this application through specific implementation schemes. Furthermore, the following embodiments are merely practical examples used to illustrate and explain the content of the technical solutions in the specification, and should not limit the scope of the claims to be protected by this application. All technical products based on the technical solutions described in this application should be covered within the scope of protection of this application.

[0050] In the following embodiments, unless otherwise specified, the raw materials are all commercially available products or can be prepared by methods known to those skilled in the art. Example

[0051] Example 1 provides a saline-alkali land conditioner, which, by mass, comprises the following raw materials: 38 parts of inorganic metal salt, 25 parts of modified desulfurized gypsum, 4 parts of amino acids, 2.5 parts of polypeptides, 1.5 parts of microbial inoculant, 16 parts of modified chitosan, and 22 parts of additives.

[0052] The inorganic metal salt is a composition of superphosphate, calcium chloride and potassium aluminum sulfate; the mass ratio of superphosphate, calcium chloride and potassium aluminum sulfate is 8:23:4.5.

[0053] The preparation method of modified desulfurized gypsum includes the following steps, in parts by weight: S1: Add 4 parts of desulfurized gypsum to 60 parts of deionized water, then add 0.2 parts of 3-aminopropyltriethoxysilane, 0.4 parts of polyethylene glycol 400 and 1.2 parts of amylopectin in sequence, heat to 55℃ and stir continuously for 1.5h; S2: Then, while stirring continuously, add 0.4 parts of tetraethyl orthosilicate and 0.1 parts of ammonia water mixed deionized water (10 parts in total), and then stir continuously for 60min; S3: After stirring, filter the product and place it in a ventilated oven to dry at 75℃ for 3h. The product is then obtained.

[0054] The desulfurized gypsum was purchased from Beijing Yiwei Company as a premium-grade desulfurized gypsum product.

[0055] The amylopectin was purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd., and the amylopectin content was ≥70%.

[0056] The amino acid is a complex composition of arginine and glutamic acid. The preparation method of the complex composition of arginine and glutamic acid includes the following steps, in parts by weight: 1.8 parts of zinc acetate, 1.5 parts of arginine and 4 parts of glutamic acid are mixed and added to a reaction vessel and dissolved and mixed with 60 parts of deionized water. The pH is controlled at 6 and the temperature is raised to 60°C. The reaction is kept at this temperature for 3 hours. After the reaction is completed, the product is passed through a 280-mesh sieve and filtered to remove impurities.

[0057] The polypeptide is a fish protein peptide, purchased from Jiangsu Caiwei Biotechnology Co., Ltd. as a food-grade fish protein peptide product.

[0058] The microbial agent is EM bacteria, purchased from Shandong Kunlanbinong Biotechnology Co., Ltd.

[0059] The preparation method of modified chitosan includes the following steps, in parts by weight: S1: Mix 4.5 parts chitosan, 0.8 parts carboxylic acid and 0.2 parts 3-aminopropyltriethoxysilane and add them to 60 parts deionized water. Heat to 45℃ and keep the temperature for 0.8h. After the reaction is complete, add sodium hydroxide to adjust the pH to 8.5 to obtain pretreated chitosan; S2: Mix 2.5 parts pretreated chitosan and 0.35 parts ammonia water and add them to 55 parts deionized water to obtain a mixed solution for later use; S3: Add 1.8 parts aluminum hydroxide and 0.6 parts terephthalic acid to 50 parts deionized water. Heat to 210℃ under 2.2MPa pressure and react for 22h. After the reaction is complete, cool, centrifuge, filter, and wash with ethanol to obtain particle product; S4: Mix the particle product and the mixed solution at 70℃ and 450W ultrasonic vibration for 2.2h. Pass the product through an 1800-mesh sieve.

[0060] Chitosan was purchased from Hubei Hongtao Bioengineering Co., Ltd. as a food-grade chitosan product.

[0061] The additives are polyoxyethylene ethers, synergists and organic powders; the mass ratio of polyoxyethylene ethers, synergists and organic powders is 6:4:12.

[0062] The polyoxyethylene ether is lauryl alcohol polyoxyethylene ether, which was purchased from Haian Guoyun Chemical Co., Ltd. as MOA-5 product.

[0063] The synergist is polyvinyl alcohol (PVA17-88) with a degree of alcoholysis of 88%.

[0064] The organic powder is rice husk powder, purchased from Mianyang Zaiweibao Technology Co., Ltd. as 80-mesh rice husk powder.

[0065] The second aspect of this embodiment provides a method for preparing the above-mentioned saline-alkali land conditioner. The preparation method includes the following steps: heating inorganic metal salt, modified desulfurized gypsum, amino acids, polypeptides, microbial agents, modified chitosan and additives to 45°C in a high-speed mixer and stirring at 250 r / min until uniformly mixed; adding the mixed material to a granulator and granulating it to 1200 mesh to obtain the final product. Example

[0066] Example 2 provides a saline-alkali land conditioner, which, by mass, comprises: 42 parts of inorganic metal salt, 22 parts of modified desulfurized gypsum, 4 parts of amino acids, 2.5 parts of polypeptides, 1.5 parts of microbial inoculant, 18 parts of modified chitosan, and 20 parts of additives.

[0067] The inorganic metal salt is a composition of superphosphate, calcium chloride and potassium aluminum sulfate; the mass ratio of superphosphate, calcium chloride and potassium aluminum sulfate is 10:20:3.5.

[0068] The preparation method of the modified desulfurized gypsum includes the following steps, in parts by weight: S1: Add 4 parts of desulfurized gypsum to 60 parts of deionized water, then add 0.2 parts of 3-aminopropyltriethoxysilane, 0.4 parts of polyethylene glycol 400 and 1.2 parts of amylopectin in sequence, and heat to 55°C and stir continuously for 1.5 h; S2: Then, while stirring continuously, add 0.4 parts of tetraethyl orthosilicate and 0.1 parts of ammonia water mixed deionized water (10 parts in total), and then stir continuously for 60 min; S3: After stirring, filter the product and place it in a ventilated oven to dry at 75°C for 3 h, and the product is obtained.

[0069] The desulfurized gypsum was purchased from Beijing Yiwei Company as a premium-grade desulfurized gypsum product.

[0070] The amylopectin was purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd., and the amylopectin content was ≥70%.

[0071] The amino acid is a complex composition of arginine and glutamic acid. The preparation method of the complex composition of arginine and glutamic acid includes the following steps, in parts by weight: 1.8 parts of zinc acetate, 1.5 parts of arginine and 4 parts of glutamic acid are mixed and added to a reaction vessel and dissolved and mixed with 60 parts of deionized water. The pH is controlled at 6 and the temperature is raised to 60°C. The reaction is kept at this temperature for 3 hours. After the reaction is completed, the product is passed through a 280-mesh sieve and filtered to remove impurities.

[0072] The polypeptide is a fish protein peptide, purchased from Jiangsu Caiwei Biotechnology Co., Ltd. as a food-grade fish protein peptide product.

[0073] The microbial agent is EM bacteria, purchased from Shandong Kunlanbinong Biotechnology Co., Ltd.

[0074] The modified chitosan preparation method includes the following steps, by mass: S1: 4.5 parts chitosan, 0.8 parts carboxylic acid, and 0.2 parts 3-aminopropyltriethoxysilane are mixed and added to 60 parts deionized water. The mixture is heated to 45°C and kept at this temperature for 0.8 hours. After the reaction is complete, sodium hydroxide is added to adjust the pH to 8.5 to obtain pretreated chitosan; S2: 2.5 parts pretreated chitosan and 0.35 parts ammonia are mixed and added to 55 parts deionized water to obtain a mixed solution for later use; S3: 1.8 parts aluminum hydroxide and 0.6 parts terephthalic acid are added to 50 parts deionized water. The mixture is heated to 210°C under a pressure of 2.2 MPa and reacted for 22 hours. After the reaction is complete, the mixture is cooled, centrifuged, filtered, and washed with ethanol to obtain particle products; S4: The particle products and the mixed solution are mixed and reacted by ultrasonic vibration at 70°C and 450 W for 2.2 hours. The product is then passed through an 1800-mesh sieve.

[0075] Chitosan was purchased from Hubei Hongtao Bioengineering Co., Ltd. as a food-grade chitosan product.

[0076] The additives are polyoxyethylene ethers, synergists and organic powders; the mass ratio of polyoxyethylene ethers, synergists and organic powders is 6:4:10.

[0077] The polyoxyethylene ether is lauryl alcohol polyoxyethylene ether, which was purchased from Haian Guoyun Chemical Co., Ltd. as MOA-5 product.

[0078] The synergist is polyvinyl alcohol (PVA) 17-92, with a degree of alcoholysis of 92%.

[0079] The organic powder is rice husk powder, purchased from Mianyang Zaiweibao Technology Co., Ltd. as 80-mesh rice husk powder.

[0080] The second aspect of this embodiment provides a method for preparing the above-mentioned saline-alkali land conditioner. The preparation method includes the following steps: heating inorganic metal salt, modified desulfurized gypsum, amino acids, polypeptides, microbial agents, modified chitosan and additives to 45°C in a high-speed mixer and stirring at 250 r / min until uniformly mixed; adding the mixed material to a granulator and granulating it to 1200 mesh to obtain the final product.

[0081] Comparative Example 1

[0082] The specific implementation method of this comparative example is basically the same as that of Example 1, except that: the saline-alkali soil conditioner, by mass, includes the following raw materials: 38 parts of inorganic metal salt, 25 parts of desulfurized gypsum, 4 parts of amino acids, 2.5 parts of polypeptides, 1.5 parts of microbial agent, 16 parts of modified chitosan, and 22 parts of additives.

[0083] The desulfurized gypsum was purchased from Beijing Yiwei Company as a premium-grade desulfurized gypsum product.

[0084] Comparative Example 2

[0085] The specific implementation method of this comparative example is basically the same as that of Example 1, except that: the saline-alkali land conditioner, by mass, includes the following raw materials: 60 parts of inorganic metal salt, 15 parts of modified desulfurized gypsum, 4 parts of amino acids, 2.5 parts of polypeptides, 1.5 parts of microbial agent, 16 parts of modified chitosan, and 22 parts of additives.

[0086] Comparative Example 3

[0087] The specific implementation method of this comparative example is basically the same as that of Example 1, except that the preparation method of modified desulfurized gypsum includes the following steps, in parts by mass: S1: Add 8 parts of desulfurized gypsum to 60 parts of deionized water, then add 0.1 parts of 3-aminopropyltriethoxysilane, 0.2 parts of polyethylene glycol 400 and 0.6 parts of amylopectin in sequence, heat to 55°C and stir continuously for 1.5 h; S2: Then, while stirring continuously, add 0.4 parts of tetraethyl orthosilicate and 0.1 parts of ammonia water mixed deionized water (10 parts in total), and then stir continuously for 60 min; S3: After stirring, filter the product and place it in a ventilated oven to dry at 75°C for 3 h, and the product is obtained.

[0088] Comparative Example 4

[0089] The specific implementation method of this comparative example is basically the same as that of Example 1, except that the preparation method of modified desulfurized gypsum includes the following steps, in parts by mass: S1: Add 2 parts of desulfurized gypsum to 40 parts of deionized water, then add 0.1 parts of 3-aminopropyltriethoxysilane, 0.2 parts of polyethylene glycol 400 and 0.6 parts of amylopectin in sequence, heat to 55°C and stir continuously for 1.5 h; S2: Then, while stirring continuously, add 2.5 parts of tetraethyl orthosilicate and 0.5 parts of ammonia water mixed deionized water (20 parts in total), and then stir continuously for 60 min; S3: After stirring, filter the product and place it in a ventilated oven to dry at 75°C for 4 h, and the product is obtained.

[0090] Comparative Example 5

[0091] The specific implementation method of this comparative example is basically the same as that of Example 1, except that: the saline-alkali land conditioner, by mass, includes the following raw materials: 38 parts of inorganic metal salt, 25 parts of modified desulfurized gypsum, 4 parts of amino acids, 2.5 parts of polypeptides, 1.5 parts of microbial agent, 16 parts of chitosan, and 22 parts of additives.

[0092] Chitosan was purchased from Hubei Hongtao Bioengineering Co., Ltd. as a food-grade chitosan product.

[0093] Comparative Example 6

[0094] The specific implementation method of this comparative example is basically the same as that of Example 1, except that the modified chitosan preparation method includes the following steps, in parts by mass: S1: 4.5 parts chitosan, 0.8 parts carboxylic acid and 0.2 parts 3-aminopropyltriethoxysilane are mixed and added to 60 parts deionized water, heated to 45°C, and kept at this temperature for 0.8 h. After the reaction is completed, sodium hydroxide is added to adjust the pH to 8.5 to obtain pretreated chitosan; S2: 5.5 parts pretreated chitosan and 1 part ammonia are mixed and added to 55 parts deionized water to obtain a mixed solution for later use; S3: 1 part aluminum hydroxide and 0.4 parts terephthalic acid are added to 30 parts deionized water, heated to 210°C under 2.2 MPa pressure and reacted for 22 h. After the reaction is completed, the mixture is cooled, centrifuged, filtered, and washed with ethanol to obtain particle product; S4: The particle product and the mixed solution are mixed and reacted by ultrasonic vibration at 70°C and 450 W for 2.2 h. The product is passed through an 1800-mesh sieve and the product is obtained.

[0095] Comparative Example 7

[0096] The specific implementation method of this comparative example is basically the same as that of Example 1, except that the modified chitosan preparation method includes the following steps, in parts by mass: S1: 4.5 parts chitosan, 0.8 parts carboxylic acid and 0.2 parts 3-aminopropyltriethoxysilane are mixed and added to 60 parts deionized water, heated to 45°C, and kept at this temperature for 0.8 h. After the reaction is completed, sodium hydroxide is added to adjust the pH to 8.5 to obtain pretreated chitosan; S2: 1 part aluminum hydroxide and 0.4 parts terephthalic acid are added to 30 parts deionized water, heated to 210°C under 2.2 MPa pressure and reacted for 22 h. After the reaction is completed, the mixture is cooled, centrifuged, filtered, and washed with ethanol to obtain particulate product; S4: The particulate product and pretreated chitosan are stirred and mixed at 70°C for 2.5 h. The product is passed through a 1500-mesh sieve and the product is obtained.

[0097] Performance Evaluation

[0098] 1. Saline-alkali soil improvement test: Watermelon planting plots in Changji City, Xinjiang were divided into 9 plots of 2 mu each. The soil salinity was 8.1 g / kg and the pH value was 9.7. During the test, the soil was plowed to a depth of 30 cm in each of the 9 plots, and the soil conditioner prepared in the above-mentioned example and comparative example was applied at a rate of 250 kg / mu. After that, the soil was plowed and mixed evenly. After 7 days, the soil salinity was tested, and the average value of 10 tests was recorded in Table 1.

[0099] 2. Moisture content: The soil moisture content was tested after 7 days using the test method in Example 1. The average value of 10 tests was recorded in Table 1.

[0100] 3. Stability test: The modifiers prepared in the sample examples and comparative examples were placed in a constant temperature and humidity chamber at 55°C and 75% humidity for 3 days. After 3 days, they were taken out and observed to see if there were obvious adhesion, caking, hydration and deterioration. If there were, they were recorded as unqualified, otherwise they were qualified. 50 samples were tested for each example and comparative example, and the pass rate was recorded in Table 1.

[0101] Table 1

[0102] Example Salt content (g / Kg) Moisture content (%) Stability pass rate (%) Example 1 0.81 32.4 88% Example 2 0.96 30.4 82% Comparative Example 1 1.77 27.7 72% Comparative Example 2 2.56 28.9 74% Comparative Example 3 1.28 26.9 78% Comparative Example 4 1.21 27.2 74% Comparative Example 5 2.33 19.1 68% Comparative Example 6 1.84 18.9 70% Comparative Example 7 1.56 19.8 72%

[0103] From the embodiments and comparative examples of this application, as well as the data results in Table 1, it can be seen that Embodiments 1 and 2, which adopt the technical solution defined in this application, have significant performance advantages over Comparative Examples 1-7 in terms of saline-alkali improvement efficacy, soil water retention rate, and self-stability. Embodiments 1 and 2, employing the technical solution defined in this application, can form a good modified composite layer on the surface of desulfurized gypsum. The presence of this composite layer can form a smooth surface with high surface energy and multiple surface groups, which can compensate for and repair the multi-peaked and valley-grooved surface of desulfurized gypsum. On the other hand, in subsequent use, it can adsorb water in the soil through its multiple surface hydrophilic groups and retain water through strong hydrogen bonding with water. Furthermore, the added modified chitosan material assists in enhancing the overall water absorption and retention effect of the soil. During use, a large amount of water is absorbed through the adsorption effect of the micropores in the composite particle framework, and this water can remain in the soil at the limit temperature, thus very stably fixing the water. It can also increase the total contact surface area between the amendment and the soil, thereby significantly enhancing the intensity of the effect and improving the overall performance.

Claims

1. A saline soil amendment, characterized in that: By weight, the raw materials include: 30-50 parts of inorganic metal salt, 20-30 parts of modified desulfurized gypsum, 1-10 parts of amino acids, 1-5 parts of polypeptides, 1-5 parts of microbial inoculant, 10-20 parts of modified chitosan, and 5-30 parts of additives. The inorganic metal salt is at least one of superphosphate, aluminum sulfate, ferrous sulfate, calcium sulfate, calcium chloride, potassium aluminum sulfate, and potassium dihydrogen phosphate. The preparation method of the modified desulfurized gypsum includes the following steps: S1: Add the desulfurized gypsum to deionized water, then add silane coupling agent, polyethylene glycol and amylopectin in sequence, and heat to 50~60℃ and stir continuously for 1~2h; S2: Then, while continuing to stir, add a mixed deionized aqueous solution of tetraethyl orthosilicate and ammonia, and then continue to stir for 60~80min; S3: After stirring, filter the product and place it in a ventilated oven to dry at 60~80℃ for 3~4h, and the product is obtained. The mass ratio of the desulfurized gypsum, silane coupling agent, polyethylene glycol and amylopectin is (3~5):(0.1~0.2):(0.2~0.5):(1~2). The amino acid is a complex composition of arginine and glutamic acid; The polypeptide is a fish protein peptide; The microbial agent is EM bacteria; The preparation method of the modified chitosan includes the following steps: S1: Chitosan, carboxylic acid and silane coupling agent are mixed and added to deionized water, heated to 40~50℃, and reacted for 0.5~1.5h. After the reaction is completed, sodium hydroxide is added to adjust the pH to 8~9 to obtain pretreated chitosan; S2: Pretreated chitosan and ammonia are mixed and added to deionized water to obtain a mixed solution for later use; S3: Aluminum hydroxide and terephthalic acid are added to deionized water, heated to 200~210℃ under 2.2MPa pressure and reacted for 16~24h. After the reaction is completed, the mixture is cooled, centrifuged and filtered, and washed with ethanol to obtain particle product; S4: The particle product and the mixed solution are ultrasonically mixed and reacted at 60~85℃ and 400~600W. After the reaction is completed, the product is obtained. The inorganic metal salt, modified desulfurized gypsum and modified chitosan are in a mass ratio of (35~45):(22~26):(15~18). The mass ratio of chitosan, carboxylic acid, and silane coupling agent is (3~5):(0.5~1):(0.1~0.3). The mass ratio of the pretreated chitosan, aluminum hydroxide, and terephthalic acid is (2~3):(1.5~2):(0.5~1). The preparation method of the complex composition of arginine and glutamic acid includes the following steps: zinc acetate is mixed with arginine and glutamic acid and added to a reaction vessel and dissolved and mixed with sufficient deionized water. The pH is controlled at 5-6 and the temperature is raised to 60-65℃. The reaction is kept at the temperature for 3-4 hours. After the reaction is completed, the product is passed through a 200-400 mesh sieve and filtered to remove impurities. The mass ratio of the amino acids, polypeptides and microbial agents is (3~6):(2~4):(1~3). The additives are polyoxyethylene ethers, synergists, and organic powders; the mass ratio of the polyoxyethylene ethers, synergists, and organic powders is (5~8):(3~5):(10~15). The polyoxyethylene ether is lauryl alcohol polyoxyethylene ether or cetearyl alcohol polyoxyethylene ether; The organic powder is at least one of rice husk powder, jujube kernel powder, peanut shell powder, wheat bran powder, and straw powder.

2. A method of preparing the saline soil improver according to claim 1, characterized by: The preparation method includes the following steps: Inorganic metal salts, modified desulfurized gypsum, amino acids, peptides, microbial agents, modified chitosan and additives are heated to 40~50℃ in a high-speed mixer and stirred evenly at a speed of 200~300r / min. The mixed material is then added to a granulator and granulated to the required particle size to obtain the final product.