Saline alkali soil conditioner and preparation method thereof

Abstract

The invention discloses a saline alkali soil conditioner and a preparation method thereof, and belongs to the technical field of soil improvement. The soil conditioner is prepared from the following raw materials in parts by weight: 100-200 parts of modified phosphogypsum, 5-10 parts of a microbial agent and 10-20 parts of an activating agent, the modified ardealite is prepared by compounding ardealite and modified coal gangue and then modifying with rare earth; the microbial agent is prepared by mixing bacillus subtilis, streptomyces cellulosae and bacillus mucilaginosus. Chemical-physical-biological improvement technologies are combined, so that the physical and chemical properties of the saline-alkali soil are effectively improved, the biological activity of the soil is improved, the growth of crops is promoted, the yield and disease resistance of the crops are improved, and the resource utilization rate of the ardealite is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of soil improvement, and in particular relates to a saline-alkali soil conditioner and a preparation method thereof. Background Art

[0002] Studies have shown that for every ton of phosphoric acid produced by the sulfuric acid method, nearly 5 tons of phosphogypsum will be produced. According to statistics, the current global stockpile of phosphogypsum has reached 6 billion tons, and is still increasing at a rate of 150 million tons per year, but the global comprehensive utilization rate of phosphogypsum is only about 25%. my country is the world's largest producer of phosphate fertilizers and the largest by-producer of phosphogypsum. The stockpile of phosphogypsum has reached 400 million tons, and is still increasing at a rate of about 50 million tons per year. The main component of phosphogypsum is calcium sulfate dihydrate (CaSO 4 ·2H 2 O), and contains a small amount of free acid, phosphate, fluoride, organic matter and trace elements. my country's phosphogypsum production areas are mainly concentrated in Hubei, Yunnan, Guizhou, Shandong, Anhui and other places. The production of phosphogypsum in these areas accounts for about 85% of the total production of phosphogypsum in the country, but the comprehensive utilization rate of phosphogypsum is less than 50%. Compared with the comprehensive utilization of phosphogypsum in other countries, my country has shortcomings and still needs to continue to explore.

[0003] At present, scholars have conducted a lot of research on the comprehensive utilization of phosphogypsum, mainly focusing on the following three aspects: building materials, chemical products and its application as a soil conditioner in agriculture. In recent years, the comprehensive utilization rate of phosphogypsum has been gradually increasing, but there is still great pressure on storage and environmental risks. Although phosphogypsum has significant effects in some aspects of soil improvement, it also has some disadvantages that cannot be ignored, such as the introduction of harmful substances such as heavy metals (such as Cd, Pb, As) and environmental risks such as excessive fluorine (F), which damage the soil ecosystem. In particular, the fluoride contained in phosphogypsum has a direct toxic effect on plant growth. When the fluoride content in the soil is too high, it will inhibit plant growth and even cause plant death. If the fluoride in phosphogypsum is directly discharged or piled up without treatment, it will pollute the soil environment. The fluoride in the long-term accumulated phosphogypsum will penetrate into the soil under the erosion of rainwater, causing soil pollution. This pollution may last for years or even decades, causing long-term impacts on the soil ecosystem and agricultural production. After fluoride enters the soil, it may enter the human body through the food chain, causing harm to human health. Therefore, it is very important to seek comprehensive and safe utilization methods and technologies for phosphogypsum. Summary of the invention

[0004] The present invention aims to provide a saline-alkali soil conditioner, which is prepared by using modified phosphogypsum as the main raw material, mixing with microorganisms and then adding a suitable activator. The chemical-physical-biological improvement technology is combined to effectively improve the physical and chemical properties of saline-alkali soil, increase soil biological activity, promote crop growth, increase crop yield and disease resistance, and improve the resource utilization rate of phosphogypsum.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is: A saline-alkali soil conditioner is prepared from the following raw materials in parts by weight: 100-200 parts of modified phosphogypsum, 5-10 parts of microbial agent, and 10-20 parts of activator; the modified phosphogypsum is prepared by compounding phosphogypsum and modified coal gangue and then modifying them with rare earth; the microbial agent is prepared by mixing Bacillus subtilis, Streptomyces cellulosus, and Bacillus gelatinus.

[0006] Preferably, the activator is composed of bamboo shoot shells and sodium lignin sulfonate in a mass ratio of 2:1.

[0007] Preferably, the modified phosphogypsum is prepared by the following method: phosphogypsum and modified coal gangue are mixed and ball milled at a speed of 600 r / min for 1-2 h, and then the mixture is immersed in 0.1 mol / L NdCl 3 The solution is stirred magnetically for 4-6 hours at room temperature. After the reaction is completed, it is centrifuged, washed with anhydrous ethanol, dried, and ground into powder to obtain modified phosphogypsum.

[0008] Preferably, the mass ratio of the phosphogypsum to the modified coal gangue is 1:0.25-0.5; the ball-milled mixture is mixed with NdCl 3 The solid-liquid ratio of the solution is 1g:30ml.

[0009] Preferably, the modified coal gangue is prepared by the following method: (1) The raw material coal gangue is crushed, ground, passed through a 200-mesh sieve, and heat-treated at 500°C for 2 hours to obtain pretreated coal gangue powder; (2) Add silane coupling agent KH570 to the mixed solution, adjust the pH value to 6.0 with sodium hydroxide and hydrochloric acid, stir magnetically for 30-45 minutes at room temperature, add the pretreated coal gangue powder, heat to 40-45°C, react for 2-3 hours, filter and wash the product to neutrality, and dry to obtain modified coal gangue.

[0010] Preferably, in step (2), the mass ratio of silane coupling agent KH570 to pretreated coal gangue powder is 1:30; the mixed solution is composed of anhydrous ethanol and deionized water in a volume ratio of 3:1; the solid-liquid ratio of pretreated coal gangue powder to the mixed solution is 1g:20ml.

[0011] The present invention also provides a method for preparing the saline-alkali soil conditioner, which comprises the following steps: a. Inoculate Bacillus subtilis, Streptomyces cellulosus, and Bacillus jelly into LB liquid medium respectively, and culture at 28°C with shaking until the bacterial count reaches OD 600 ≈2.0, and then mixed in a volume ratio of 1:1:1 and dried to obtain a microbial agent; The LB liquid culture medium is composed of: 5 g yeast extract, 10 g tryptone, 10 g sodium chloride, 1000 mL distilled water, pH adjusted to 7.0; and sterilized at 121° C. for 20 min.

[0012] b. The bamboo shoot shells were crushed and passed through a 100 mesh sieve, and mixed with sodium lignin sulfonate in a mass ratio to obtain an activator; c. Preparation of modified phosphogypsum; d. Evenly mix the modified phosphogypsum, microbial agent and activator according to the weight ratio and package them to obtain the final product.

[0013] The dosage of the soil conditioner of the present invention is 20-30 kg / mu, and the dosage is adjusted according to the actual land conditions.

[0014] The Bacillus subtilis used in the present invention was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, with a deposit number of CGMCC No. 1.7740 and a deposit date of July 24, 2008; Streptomyces cellulosus was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, with a deposit number of CGMCC No. 4.6365 and a deposit date of September 3, 2008; Bacillus gelatinus was purchased from China Center for Type Culture Collection, with an address of Luojia Mountain, Bayi Road, Wuchang District, Wuhan City, Hubei Province, with a deposit number of CCTCC No. KB 20082790 and a deposit date of September 25, 2004. The above strains can be purchased through the strain catalog of the collection center without the need for additional preservation.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The use of two types of solid waste, phosphogypsum and coal gangue, to prepare saline-alkali soil conditioner improves the comprehensive utilization rate of solid waste and has significant environmental benefits.

[0016] (2) The modified phosphogypsum in the present invention is prepared by mixing phosphogypsum and coal gangue as two solid wastes and then modifying them with the rare earth element neodymium. The microstructure of the modified phosphogypsum is obviously rough and fluffy, and the pores are enlarged (see Figure 1), the specific surface area increases, the activity of surface functional groups is enhanced, and it has a good adsorption effect on harmful substances such as heavy metals (such as Cd, Pb, As, etc.) and fluoride (F) ions in the soil and original phosphogypsum. At the same time, it also promotes the formation of soil aggregate structure and increases the infiltration rate of salt, thereby achieving the purpose of reducing salinity, lowering pH and reducing soil compaction.

[0017] (3) Phosphogypsum modified with rare earth neodymium can more effectively exchange with sodium ions in saline-alkali soil and reduce the alkalinity of the soil. This is because the ion radius of the rare earth neodymium element is similar to that of calcium ions, which can replace some of the sodium ions in the soil to form more stable compounds, thereby reducing the sodium ion content in the soil.

[0018] (4) The bamboo shoot shells in the activator prepared by the present invention can produce soluble ions and small molecular organic acids after decomposition, which can reduce the pH value of the soil and promote the dissolution and release of heavy metal ions in the soil. Sodium lignin sulfonate can increase the activity of the functional groups on the surface of the modified phosphogypsum and improve the adsorption of harmful heavy metal ions in the soil. The combination of the two can significantly improve the improvement effect of the soil conditioner on saline-alkali soil.

[0019] (5) The modified phosphogypsum prepared by the present invention provides a suitable ecological environment for microorganisms, promotes the growth of beneficial microorganisms, improves soil enzyme activity, promotes crop growth, increases crop yield and disease resistance, and truly achieves the improvement of saline-alkali soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a SEM test picture of the microscopic morphology of the modified phosphogypsum prepared as shown in Example 3 of the present invention before and after modification, wherein a is unmodified phosphogypsum, b is unmodified coal gangue, and c is modified phosphogypsum. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described below in conjunction with specific embodiments, but is not limited thereto.

[0022] Example 1 A saline-alkali soil conditioner is prepared from the following raw materials in parts by weight: 100 parts of modified phosphogypsum, 5 parts of microbial agent, and 10 parts of activator; the modified phosphogypsum is prepared by compounding phosphogypsum and modified coal gangue and then modifying them with rare earth; the microbial agent is prepared by mixing Bacillus subtilis, Streptomyces cellulosus, and Bacillus gelatinus.

[0023] The activator is composed of bamboo shoot shells and sodium lignin sulfonate in a mass ratio of 2:1.

[0024] The modified phosphogypsum is prepared by the following method: phosphogypsum and modified coal gangue are mixed in a mass ratio of 1:0.25 and ball milled for 1-2 hours at a speed of 600 r / min using a ball mill, and then the mixture is immersed in 0.1 mol / L NdCl 3 The solution was stirred under magnetic stirring at room temperature for 4-6 hours. After the reaction, it was centrifuged and washed with anhydrous ethanol, dried and ground into powder to obtain modified phosphogypsum. The ball-milled mixture was mixed with NdCl 3 The solid-liquid ratio of the solution is 1g:30ml.

[0025] The modified coal gangue is prepared by the following method: (1) The raw material coal gangue is crushed, ground, passed through a 200-mesh sieve, and heat-treated at 500°C for 2 hours to obtain pretreated coal gangue powder; (2) Add silane coupling agent KH570 to the mixed solution, adjust the pH value to 6.0 with sodium hydroxide and hydrochloric acid, stir magnetically for 30-45 minutes at room temperature, add pretreated coal gangue powder, heat to 40-45°C, react for 2-3 hours, filter and wash the product to neutrality, and dry to obtain modified coal gangue; the mass ratio of the silane coupling agent KH570 to the pretreated coal gangue powder is 1:30; the mixed solution is composed of anhydrous ethanol and deionized water in a volume ratio of 3:1; the solid-liquid ratio of the pretreated coal gangue powder to the mixed solution is 1g:20ml.

[0026] A method for preparing the above-mentioned saline-alkali soil conditioner comprises the following steps: a. Inoculate Bacillus subtilis, Streptomyces cellulosus, and Bacillus jelly into LB liquid medium respectively, and culture at 28°C with shaking until the bacterial count reaches OD 600 ≈2.0, and then mixed in a volume ratio of 1:1:1 and dried to obtain a microbial agent; The LB liquid culture medium is composed of: 5 g yeast extract, 10 g tryptone, 10 g sodium chloride, 1000 mL distilled water, pH adjusted to 7.0; and sterilized at 121° C. for 20 min.

[0027] b. The bamboo shoot shells were crushed and passed through a 100 mesh sieve, and mixed with sodium lignin sulfonate in a mass ratio to obtain an activator; c. Preparation of modified phosphogypsum; d. Evenly mix the modified phosphogypsum, microbial agent and activator according to the weight ratio and package them to obtain the final product.

[0028] Example 2 A saline-alkali soil conditioner is prepared from the following raw materials in parts by weight: 200 parts of modified phosphogypsum, 10 parts of microbial agent, and 20 parts of activator; the modified phosphogypsum is prepared by compounding phosphogypsum and modified coal gangue and then modifying them with rare earth; the microbial agent is prepared by mixing Bacillus subtilis, Streptomyces cellulosus, and Bacillus gelatinus.

[0029] The activator is composed of bamboo shoot shells and sodium lignin sulfonate in a mass ratio of 2:1.

[0030] The modified phosphogypsum is prepared by the following method: phosphogypsum and modified coal gangue are mixed in a mass ratio of 1:0.4 and ball milled for 1-2 hours at a speed of 600 r / min using a ball mill, and then the mixture is immersed in 0.1 mol / L NdCl 3 The solution was stirred under magnetic stirring at room temperature for 4-6 hours. After the reaction, it was centrifuged and washed with anhydrous ethanol, dried and ground into powder to obtain modified phosphogypsum. The ball-milled mixture was mixed with NdCl 3 The solid-liquid ratio of the solution is 1g:30ml.

[0031] The modified coal gangue is prepared by the following method: (1) The raw material coal gangue is crushed, ground, passed through a 200-mesh sieve, and heat-treated at 500°C for 2 hours to obtain pretreated coal gangue powder; (2) Add silane coupling agent KH570 to the mixed solution, adjust the pH value to 6.0 with sodium hydroxide and hydrochloric acid, stir magnetically for 30-45 minutes at room temperature, add pretreated coal gangue powder, heat to 40-45°C, react for 2-3 hours, filter and wash the product to neutrality, and dry to obtain modified coal gangue; the mass ratio of the silane coupling agent KH570 to the pretreated coal gangue powder is 1:30; the mixed solution is composed of anhydrous ethanol and deionized water in a volume ratio of 3:1; the solid-liquid ratio of the pretreated coal gangue powder to the mixed solution is 1g:20ml.

[0032] A method for preparing the above-mentioned saline-alkali soil conditioner comprises the following steps: a. Inoculate Bacillus subtilis, Streptomyces cellulosus, and Bacillus jelly into LB liquid medium respectively, and culture at 28°C with shaking until the bacterial count reaches OD 600 ≈2.0, and then mixed in a volume ratio of 1:1:1 and dried to obtain a microbial agent; The LB liquid culture medium is composed of: 5 g yeast extract, 10 g tryptone, 10 g sodium chloride, 1000 mL distilled water, pH adjusted to 7.0; and sterilized at 121° C. for 20 min.

[0033] b. The bamboo shoot shells were crushed and passed through a 100 mesh sieve, and mixed with sodium lignin sulfonate in a mass ratio to obtain an activator; c. Preparation of modified phosphogypsum; d. Evenly mix the modified phosphogypsum, microbial agent and activator according to the weight ratio and package them to obtain the final product.

[0034] Example 3 A saline-alkali soil conditioner is prepared from the following raw materials in parts by weight: 150 parts of modified phosphogypsum, 8 parts of microbial agent, and 15 parts of activator; the modified phosphogypsum is prepared by compounding phosphogypsum and modified coal gangue and then modifying them with rare earth; the microbial agent is prepared by mixing Bacillus subtilis, Streptomyces cellulosus, and Bacillus gelatinus.

[0035] The activator is composed of bamboo shoot shells and sodium lignin sulfonate in a mass ratio of 2:1.

[0036] The modified phosphogypsum is prepared by the following method: phosphogypsum and modified coal gangue are mixed in a mass ratio of 1:0.5 and ball milled for 1-2 hours at a speed of 600 r / min using a ball mill, and then the mixture is immersed in 0.1 mol / L NdCl 3 The solution was stirred under magnetic stirring at room temperature for 4-6 hours. After the reaction, it was centrifuged and washed with anhydrous ethanol, dried and ground into powder to obtain modified phosphogypsum. The ball-milled mixture was mixed with NdCl 3 The solid-liquid ratio of the solution is 1g:30ml.

[0037] The modified coal gangue is prepared by the following method: (1) The raw material coal gangue is crushed, ground, passed through a 200-mesh sieve, and heat-treated at 500°C for 2 hours to obtain pretreated coal gangue powder; (2) Add silane coupling agent KH570 to the mixed solution, adjust the pH value to 6.0 with sodium hydroxide and hydrochloric acid, stir magnetically for 30-45 minutes at room temperature, add pretreated coal gangue powder, heat to 40-45°C, react for 2-3 hours, filter and wash the product to neutrality, and dry to obtain modified coal gangue; the mass ratio of the silane coupling agent KH570 to the pretreated coal gangue powder is 1:30; the mixed solution is composed of anhydrous ethanol and deionized water in a volume ratio of 3:1; the solid-liquid ratio of the pretreated coal gangue powder to the mixed solution is 1g:20ml.

[0038] A method for preparing the above-mentioned saline-alkali soil conditioner comprises the following steps: a. Inoculate Bacillus subtilis, Streptomyces cellulosus, and Bacillus jelly into LB liquid medium respectively, and culture at 28°C with shaking until the bacterial count reaches OD 600 ≈2.0, and then mixed in a volume ratio of 1:1:1 and dried to obtain a microbial agent; The LB liquid culture medium is composed of: 5 g yeast extract, 10 g tryptone, 10 g sodium chloride, 1000 mL distilled water, pH adjusted to 7.0; and sterilized at 121° C. for 20 min.

[0039] b. The bamboo shoot shells were crushed and passed through a 100 mesh sieve, and mixed with sodium lignin sulfonate in a mass ratio to obtain an activator; c. Preparation of modified phosphogypsum; d. Evenly mix the modified phosphogypsum, microbial agent and activator according to the weight ratio and package them to obtain the final product.

[0040] Comparative Example 1 A saline-alkali soil conditioner is made of the following raw materials in parts by weight: 150 parts of phosphogypsum, 8 parts of microbial agent, and 15 parts of activator. The microbial agent is made by mixing Bacillus subtilis, Streptomyces cellulosus, and Bacillus gelatinus. The activator is composed of bamboo shoot shells and sodium lignin sulfonate in a mass ratio of 2:1.

[0041] This comparative example is basically the same as Example 3, with the only difference being that the phosphogypsum is unmodified phosphogypsum, which is a common commercially available by-product of wet-process phosphoric acid production.

[0042] Comparative Example 2 A saline-alkali soil conditioner is prepared from the following raw materials in parts by weight: 150 parts of modified phosphogypsum, 8 parts of microbial agent, and 15 parts of activator; the modified phosphogypsum is prepared by compounding phosphogypsum with coal gangue and then modifying it with rare earth; the microbial agent is prepared by mixing Bacillus subtilis, Streptomyces cellulosus, and Bacillus gelatinus.

[0043] The activator is composed of bamboo shoot shells and sodium lignin sulfonate in a mass ratio of 2:1.

[0044] The modified phosphogypsum is prepared by the following method: phosphogypsum and coal gangue are mixed in a mass ratio of 1:0.5 and ball milled at a speed of 600 r / min for 1-2 hours using a ball mill, and then the mixture is immersed in 0.1 mol / L NdCl 3 The solution was stirred under magnetic stirring at room temperature for 4-6 hours. After the reaction, it was centrifuged and washed with anhydrous ethanol, dried and ground into powder to obtain modified phosphogypsum. The ball-milled mixture was mixed with NdCl 3 The solid-liquid ratio of the solution is 1g:30ml.

[0045] A method for preparing the above-mentioned saline-alkali soil conditioner comprises the following steps: a. Inoculate Bacillus subtilis, Streptomyces cellulosus, and Bacillus jelly into LB liquid medium respectively, and culture at 28°C with shaking until the bacterial count reaches OD 600≈2.0, and then mixed in a volume ratio of 1:1:1 and dried to obtain a microbial agent; The LB liquid culture medium is composed of: 5 g yeast extract, 10 g tryptone, 10 g sodium chloride, 1000 mL distilled water, pH adjusted to 7.0; and sterilized at 121° C. for 20 min.

[0046] b. The bamboo shoot shells were crushed and passed through a 100 mesh sieve, and mixed with sodium lignin sulfonate in a mass ratio to obtain an activator; c. Preparation of modified phosphogypsum; d. Evenly mix the modified phosphogypsum, microbial agent and activator according to the weight ratio and package them to obtain the final product.

[0047] This comparative example is basically the same as Example 3, except that the modified phosphogypsum is prepared by mixing phosphogypsum and coal gangue as raw materials and then modifying them with rare earth.

[0048] Comparative Example 3 A saline-alkali soil conditioner is prepared from the following raw materials in parts by weight: 150 parts of modified phosphogypsum and 8 parts of microbial agent; the modified phosphogypsum is prepared by compounding phosphogypsum and modified coal gangue and then modifying them with rare earth; the microbial agent is prepared by mixing Bacillus subtilis, Streptomyces cellulosus and Bacillus gelatinus.

[0049] The modified phosphogypsum is prepared by the following method: phosphogypsum and modified coal gangue are mixed in a mass ratio of 1:0.5 and ball milled for 1-2 hours at a speed of 600 r / min using a ball mill, and then the mixture is immersed in 0.1 mol / L NdCl 3 The solution was stirred under magnetic stirring at room temperature for 4-6 hours. After the reaction, it was centrifuged and washed with anhydrous ethanol, dried and ground into powder to obtain modified phosphogypsum. The ball-milled mixture was mixed with NdCl 3 The solid-liquid ratio of the solution is 1g:30ml.

[0050] The modified coal gangue is prepared by the following method: (1) The raw material coal gangue is crushed, ground, passed through a 200-mesh sieve, and heat-treated at 500°C for 2 hours to obtain pretreated coal gangue powder; (2) Add silane coupling agent KH570 to the mixed solution, adjust the pH value to 6.0 with sodium hydroxide and hydrochloric acid, stir magnetically for 30-45 minutes at room temperature, add pretreated coal gangue powder, heat to 40-45°C, react for 2-3 hours, filter and wash the product to neutrality, and dry to obtain modified coal gangue; the mass ratio of the silane coupling agent KH570 to the pretreated coal gangue powder is 1:30; the mixed solution is composed of anhydrous ethanol and deionized water in a volume ratio of 3:1; the solid-liquid ratio of the pretreated coal gangue powder to the mixed solution is 1g:20ml.

[0051] A method for preparing the above-mentioned saline-alkali soil conditioner comprises the following steps: a. Bacillus subtilis, Streptomyces cellulosus, and Bacillus jelly were inoculated into LB liquid medium, shaken and cultured at 28°C until the bacterial content was O.D600≈2.0, and then mixed in a volume ratio of 1:1:1 and dried to obtain a microbial agent; The LB liquid culture medium is composed of: 5 g yeast extract, 10 g tryptone, 10 g sodium chloride, 1000 mL distilled water, pH adjusted to 7.0; and sterilized at 121° C. for 20 min.

[0052] b. preparing modified phosphogypsum; c. Evenly mix the modified phosphogypsum and microbial agent according to the weight ratio and package them to obtain the final product.

[0053] This comparative example is basically the same as Example 3, except that it does not contain an activator.

[0054] Performance Testing The safety of the products prepared by Examples 1-3 and Comparative Examples 1-3 of the present invention was tested. 10 g of each test sample was taken, added to 100 ml of deionized water to prepare a mixed solution, sealed and light-proof, placed in a constant temperature shaking box at 120 r / min and 25°C for 8 hours, and then sampled and analyzed after standing for 16 hours. Before sampling, the mixed solution was first filtered through a 0.45 μm glass fiber filter membrane. The filtered water sample was tested for indicators according to the method of "Identification Standard for Dangerous Poisons - Identification of Leaching Toxicity" (GB 5085.3-2007). The specific test results are shown in Table 1.

[0055] Table 1 Test results It can be seen from the results in Table 1 above that the saline-alkali soil conditioner prepared by the present invention is safer than conventional phosphogypsum, and the content of heavy metal elements and fluoride ions contained in it is greatly reduced. This is because the modified phosphogypsum has a loose and porous structure, which has a good adsorption effect on harmful substances such as heavy metals (such as Cd, Pb, As, etc.) and fluoride (F) ions, thereby reducing the superimposed harm of fluoride ions and heavy metals brought to the soil by the application of the conditioner.

[0056] Field application test The test site was a farmland in Huaguan Village, Huaguan Town, Guangrao County, Shandong Province. Soil samples from the 0-30cm layer of the soil surface were collected and sent back to the laboratory immediately after sampling. They were frozen during transportation. After being transported back to the laboratory, the physical and chemical indicators, heavy metal content and fluoride ion situation of the collected soil samples were immediately tested. The results are shown in Table 2-3.

[0057] Table 2 Basic physical and chemical properties of the tested soils Table 3 Heavy metal and fluoride ion contents in original soil The crop planted was wheat, and the test variety was Jimai 60. The test field area was set up with Example 1-3 groups, Comparative Example 1-3 groups, and a total of 7 treatments in the blank control group. The area of ​​each treatment group was 2 mu, and the wheat planting density in each group was the same, all of which were 80 plants / square meter. Different soil conditioners were applied to each group, with an application amount of 30 kg / mu. The blank control group did not apply any soil conditioner, and the rest of the operation process was conventional field management. The number of withered and dead seedlings per mu, plant height (randomly selected 50 plants to take the average value), thousand-grain weight, and harvested per mu yield were counted at the harvest time. The specific experimental results are shown in Table 4.

[0058] Table 4 Results of wheat planting test in the experimental field From the data in Table 4 above, it can be seen that compared with the blank control group, the wheat yield was significantly increased after using the soil conditioner of the present invention, and the plant height, thousand-grain weight and per-acre yield index were better than those of comparative examples 1-3 and the blank control. This is because the saline-alkali soil conditioner prepared by the present invention can effectively improve the physical and chemical properties of saline-alkali soil through the synergistic effect of multiple components, thereby significantly improving the fertility and health level of the soil, which helps to promote the growth and development of plants and improve the yield and quality of crops.

[0059] In order to further test the improvement effect of the soil conditioner of the present invention on saline-alkali soil, the physical and chemical properties, heavy metal content and fluoride ion content of the soil after planting in each treatment group were measured. Soil sampling and soil testing were carried out within the range of 0-30cm from the surface depth of the test site. Soil samples were collected from each treatment group according to the S-shaped sampling method. When taking soil, the soil drill was drilled to a depth of 30cm at one time. Each treatment group collected 3 replicates, and the 3 replicate samples of the same treatment group were mixed into one sample. Visible debris such as gravel and plant roots were removed and divided into two parts, one part was used to determine the basic physical and chemical properties of the soil; the other part was used to determine the heavy metal content and fluoride ion content. The test results are shown in Tables 5-6.

[0060] Table 5 Test results Table 6 Test results From the results in Tables 5-6 above, it can be seen that after using the soil conditioner prepared by the present invention, the soil pH, bulk density, total salt content, various heavy metal contents, and fluoride ion content are significantly reduced, and the soil organic matter content is increased. The corresponding soil improvement effects of Comparative Examples 1, 2, and 3 are relatively poor. This is because the modified phosphogypsum obtained by treating phosphogypsum and modified coal gangue by a specific modification method has a significantly rough and fluffy microstructure, with more pores (see Figure 1 ), the specific surface area increases, the activity of the surface functional groups is enhanced, and it has a good adsorption effect on harmful substances such as heavy metals (such as Cd, Pb, As, etc.) and fluorine (F) ions in the soil. At the same time, it also promotes the formation of soil aggregate structure, increases the infiltration rate of salt and increases the exchange capacity of sodium ions, thereby achieving the purpose of reducing salinity, lowering pH, and reducing soil compaction. At the same time, the activator used can promote the dissolution and release of heavy metal ions in the soil on the one hand, and on the other hand, by increasing the activity of the surface functional groups of the modified phosphogypsum and improving the adsorption of harmful heavy metal ions in the soil, it can significantly improve the improvement effect of soil conditioners on saline-alkali soils.

[0061] It should be noted that the above embodiments are only partial embodiments of the preferred methods of implementing the present invention, rather than all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

Claims

1. A saline-alkali soil conditioner, characterized in that: The invention is prepared from the following raw materials in parts by weight: 100-200 parts of modified phosphogypsum, 5-10 parts of microbial agent and 10-20 parts of activator; the modified phosphogypsum is prepared by compounding phosphogypsum and modified coal gangue and then performing rare earth modification; the microbial agent is prepared by mixing Bacillus subtilis, Streptomyces cellulosus and Bacillus gelatinus.

2. The saline-alkali soil conditioner according to claim 1, characterized in that The activator is composed of bamboo shoot shells and sodium lignin sulfonate in a mass ratio of 2:

1.

3. The saline-alkali soil conditioner according to claim 1, characterized in that The modified phosphogypsum is prepared by the following method: phosphogypsum and modified coal gangue are mixed and ball-milled at a speed of 600 r / min for 1-2 hours with a ball mill, and then the mixture is immersed in a 0.1 mol / L NdCl3 solution, and reacted with magnetic stirring at room temperature for 4-6 hours. After the reaction is completed, the mixture is centrifuged, washed with anhydrous ethanol, dried, and then ground into powder to obtain the modified phosphogypsum.

4. The saline-alkali soil conditioner according to claim 3, characterized in that: The mass ratio of the phosphogypsum to the modified coal gangue is 1:0.25-0.5; the material-liquid ratio of the ball-milled mixture to the NdCl3 solution is 1g:30ml.

5. The saline-alkali soil conditioner according to claim 3 or 4, characterized in that: The modified coal gangue is prepared by the following method: (1) The raw material coal gangue is crushed, ground, passed through a 200-mesh sieve, and heat-treated at 500°C for 2 hours to obtain pretreated coal gangue powder; (2) Add silane coupling agent KH570 to the mixed solution, adjust the pH value to 6.0 with sodium hydroxide and hydrochloric acid, stir magnetically for 30-45 minutes at room temperature, add the pretreated coal gangue powder, heat to 40-45°C, react for 2-3 hours, filter and wash the product to neutrality, and dry to obtain modified coal gangue.

6. The saline-alkali soil conditioner according to claim 5, characterized in that In the step (2), the mass ratio of silane coupling agent KH570 to pretreated coal gangue powder is 1:30; the mixed solution is composed of anhydrous ethanol and deionized water in a volume ratio of 3:1; the material-liquid ratio of pretreated coal gangue powder to the mixed solution is 1g:20ml.

7. A method for preparing the saline-alkali soil conditioner according to any one of claims 1 to 6, characterized in that: It includes the following steps: a. Inoculate Bacillus subtilis, Streptomyces cellulosus, and Bacillus jelly into LB liquid medium respectively, and culture at 28°C with shaking until the bacterial content reaches OD 600 ≈2.0, and then mixed in a volume ratio of 1:1:1 and dried to obtain a microbial agent; b. The bamboo shoot shells were crushed and passed through a 100 mesh sieve, and mixed with sodium lignin sulfonate in a mass ratio to obtain an activator; c. Preparation of modified phosphogypsum; d. Evenly mix the modified phosphogypsum, microbial agent and activator according to the weight ratio and package them to obtain the final product.

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