Preparation and application of titanium gypsum-sheep manure composite soil conditioner

Abstract

The invention discloses a titanium gypsum-sheep manure composite soil conditioner preparation method, which comprises: crushing titanium gypsum and a sheep manure organic fertilizer, and uniformly mixing to obtain the titanium gypsum-sheep manure composite soil conditioner. The titanium gypsum and the sheep manure organic fertilizer are used as raw materials, the titanium gypsum-sheep manure composite soil conditioner is prepared according to different proportions, the pH value of soil with different acidification degrees can be slowly increased to 6.8-7.5 suitable crop growth intervals, the soil conditioner has a particularly remarkable improvement effect on relatively strong acid soil with the pH value of 4.5, and the pH value of the soil improved under the optimal condition can be restored to 6.92 + / -0.07. The prepared titanium gypsum-sheep manure composite soil conditioner can efficiently improve acid soil with different acidification degrees, considerable yield and quality can be obtained in crop planting after improvement, and theoretical guidance and technical support are provided for acid soil improvement practice and resource utilization of industrial solid waste titanium gypsum.

Description

Technical Field

[0001] This invention belongs to the field of soil remediation technology, and more specifically, this invention relates to the preparation and application of a titanium gypsum-sheep manure composite soil conditioner. Background Technology

[0002] Soil is the core medium for crop growth, and its quality directly affects the stability and sustainability of agricultural production, as well as food security and ecological balance. In the process of large-scale agricultural development in China, soil quality has long been constrained by soil acidification, characterized by its wide impact, deep acidification levels, and significant regional differences. Coupled with long-term continuous cropping, this has further exacerbated soil acidification, causing serious harm to the agricultural ecosystem. The causes of acidic soils are complex. Inappropriate fertilization patterns (such as excessive nitrogen fertilization) lead to the accumulation of hydrogen ions in the soil, disrupting the soil's acid-base balance. Local climate characteristics and atmospheric conditions may also exacerbate the soil acidification process. Soil acidification not only damages soil aggregate structure, reducing soil aeration and permeability, but also reduces the availability of mineral elements such as calcium, magnesium, and phosphorus, making them difficult for crops to absorb. This inhibits root development, disrupts normal crop growth and metabolism, severely impacting crop yield and quality, and seriously hindering the rapid development of agricultural production. Therefore, developing and formulating efficient, feasible, and environmentally friendly acidic soil improvement strategies has become an urgent need for the sustainable and stable development of agricultural production.

[0003] The vanadium-titanium industry is an important component of my country's strategic emerging industries. The production of its core products, titanium dioxide and vanadium products, generates a large amount of titanium gypsum, a byproduct of ilmenite acid hydrolysis. This industrial solid waste is produced in large quantities and has a complex composition. Large-scale open-air dumping of this waste not only occupies significant land resources but also exacerbates air pollution due to the resulting dust. Furthermore, the salts in titanium gypsum can be leached into the soil or groundwater by rainwater, severely disrupting the balance of surrounding soil and aquatic ecosystems and posing a potential threat to local water resource security and agricultural and fishery production. This has become a key challenge in the sustainable development of the vanadium-titanium industry. It is worth noting that titanium gypsum itself is alkaline, which can neutralize hydrogen ions in acidic soils. It is also rich in mineral elements such as calcium and sulfur, which are essential for plants. Therefore, it can both improve soil acidification and fertility, demonstrating significant potential for resource utilization. However, due to differences in pretreatment processes, the quality of titanium gypsum varies significantly between batches, making stable large-scale utilization difficult. Furthermore, related research often focuses on the soil conditioning effects of titanium gypsum alone, with limited scope and depth. Compatibility studies with other soil conditioners are also lacking. Consequently, the application potential of titanium gypsum in acidic soil improvement has not been fully explored, and its resource utilization value has long been underestimated. Therefore, it is necessary to further explore the application prospects of titanium gypsum in acidic soil improvement, which will help overcome the technological bottlenecks in the resource utilization of titanium gypsum and further ensure the sustainable development of the vanadium-titanium industry and the safety of the agricultural ecological environment.

[0004] Sheep manure, a typical livestock waste, is widely available and produced in large quantities. If not properly disposed of, it easily decomposes under anaerobic conditions, producing gases that pollute the atmosphere. Furthermore, pathogens and parasites within it may leach into groundwater through rainwater, polluting surrounding water resources. However, from a resource utilization perspective, sheep manure is rich in organic matter, which promotes soil aggregate formation, improves soil compaction and water and fertilizer retention, and promotes the growth and metabolism of soil microorganisms. Its abundant mineral elements provide nutrients for crops, partially replacing chemical fertilizers and increasing crop yield and quality. Therefore, it has significant resource utilization value in soil conditioning. However, sheep manure alone has limitations in soil conditioning applications, including weak acid-base buffering capacity and insufficient effectiveness in treating complex soil problems. Combining it with titanium gypsum, which has alkaline-regulating capabilities, for acidic soil improvement not only opens up a practical path for the resource utilization of titanium gypsum and sheep manure but also represents a strategy with great application potential in acidic soil improvement. Summary of the Invention

[0005] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0006] To achieve these objectives and other advantages of the present invention, a method for preparing a titanium gypsum-sheep manure composite soil conditioner is provided, comprising: crushing titanium gypsum and sheep manure organic fertilizer and mixing them evenly to obtain the titanium gypsum-sheep manure composite soil conditioner.

[0007] Preferably, the mass ratio of the titanium gypsum to sheep manure organic fertilizer is 1~2:1~2.

[0008] Preferably, modified titanium plaster is used to replace the titanium plaster; the method for preparing the modified titanium plaster includes the following steps: S11. After crushing the titanium gypsum, mix it with rice husk powder and straw powder, add water and stir evenly, let it stand, dry and crush it to obtain mixture A. S12. Calcine mixture A and grind it to obtain mixture B; S13. Dry and grind the bentonite to obtain bentonite powder; add the bentonite powder to a citric acid aqueous solution, stir evenly, let stand, dry and grind to obtain activated bentonite; S14. Add activated bentonite to mixture B obtained in S12 and mix evenly to obtain modified titanium gypsum.

[0009] Preferably, in step S11, the mass ratio of titanium gypsum, rice husk powder, straw powder, and water is 100:1~10:5~15:120~200; and the mixture is left to stand for 2~5 hours.

[0010] Preferably, in step S12, the specific conditions for calcination treatment are: heating to 500-700℃ at a rate of 10-30℃ / min and holding for 20-60min, then heating to 850-950℃ at a rate of 5-15℃ / min and holding for 40-90min.

[0011] Preferably, in S13, the concentration of the citric acid aqueous solution is 1~3wt%.

[0012] Preferably, in step S13, the mass ratio of bentonite powder to citric acid aqueous solution is 1:1.5~3; and the mixture is allowed to stand for 4~8 hours.

[0013] Preferably, in step S14, the mass ratio of activated bentonite to titanium gypsum in step S11 is 1~3:20.

[0014] Application of a titanium gypsum-sheep manure composite soil conditioner prepared by the method described above in the remediation of acidic soil.

[0015] Application of a titanium gypsum-sheep manure composite soil conditioner prepared by the method described above in promoting plant growth.

[0016] This invention provides at least the following beneficial effects: Using titanium gypsum and sheep manure organic fertilizer as raw materials, this invention prepares a titanium gypsum-sheep manure composite soil conditioner in different ratios (2:1 / 1:1 / 1:2). This conditioner can moderately raise the pH value of soils with different acidification levels to the suitable growth range of crops (6.8-7.5), with particularly significant improvement effects on strongly acidic soils with a pH of 4.5. Under optimal conditions, the soil pH can be restored to 6.92±0.07 after improvement. In strongly acidic soils with a pH of 4.5, a 5% addition and a 1:1 ratio of the composite conditioner resulted in the highest fresh weight of pakchoi (0.66±0.26 g). In weakly acidic soils with a pH of 5.5, a 7% addition, a 1:1 ratio, and a 2:1 ratio were more conducive to the accumulation of soluble sugars (32.88±0.61 mg / g) and vitamin C (25.00±0.73 mg / 100g) in pakchoi, respectively. The addition of 7% at a 1:1 ratio is more conducive to lettuce growth (fresh weight 0.92±0.27 g, root length 13.41±3.15 cm, stem length 6.02±1.06 cm) and vitamin C accumulation (232.26±3.95 mg / 100 g), while the addition of 5% at a 1:2 ratio is more conducive to the accumulation of soluble sugars in lettuce (21.64±0.07 mg / g). The titanium gypsum-sheep manure composite soil conditioner prepared in this invention can effectively improve acidic soils with different degrees of acidification, and can achieve considerable yield and quality in the cultivation of crops after improvement. It provides theoretical guidance and technical support for the practice of acidic soil improvement and the resource utilization of industrial solid waste titanium gypsum.

[0017] Furthermore, this invention modifies titanium gypsum, which can further enhance the soil conditioner's effect on acidic soils, effectively improving soil permeability, water retention, and fertilizer retention, improving soil structure, passivating heavy metal elements in the soil, providing suitable micronutrients, and further promoting crop growth. First, straw powder and rice husk powder are added to reduce titanium gypsum compaction. Then, high-temperature calcination improves the internal pore structure of titanium gypsum, increasing porosity, which is beneficial for enhancing the soil's water and fertilizer retention capacity and passivating heavy metal elements in the soil. Then, activated bentonite is added to utilize its adsorption properties to fix nutrients, delay nutrient loss, and improve soil aggregate structure. The dried and ground bentonite is activated with citric acid aqueous solution to remove surface impurities, expose more active sites, and increase the surface roughness and surface reactivity of bentonite. This is beneficial for subsequent blending and modification with titanium gypsum, and also activates the adsorption properties of bentonite, enhances the synergistic effect with titanium gypsum, and makes it more suitable for acidic soil remediation and plant growth needs.

[0018] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0019] Figure 1 The effects of the titanium gypsum-sheep manure composite soil conditioner prepared in Examples 1-3 of this invention on soil pH are shown; wherein, A is soil with pH 4.5, planted with pak choi; B is soil with pH 5.5, planted with pak choi; C is soil with pH 6.5, planted with pak choi; and D is soil with pH 5.5, planted with lettuce. Figure 2 The effects of the titanium gypsum-sheep manure composite soil conditioner prepared in Examples 1-3 of this invention on the fresh weight of plants are shown. Among them, A is soil with pH 4.5, planted with Chinese cabbage; B is soil with pH 5.5, planted with Chinese cabbage; C is soil with pH 6.5, planted with Chinese cabbage; and D is soil with pH 5.5, planted with lettuce. Figure 3 The effects of the titanium gypsum-sheep manure composite soil conditioner prepared in Examples 1-3 of this invention on the root length and stem length of plants; wherein, A is the root length and B is the stem length; Figure 4 The effects of the titanium gypsum-sheep manure composite soil conditioner prepared in Examples 1-3 of this invention on the soluble sugar content of plants; wherein, A is soil with pH 5.5, planted with Chinese cabbage; B is soil with pH 5.5, planted with lettuce; Figure 5 The effects of the titanium gypsum-sheep manure composite soil conditioner prepared in Examples 1-3 of this invention on the vitamin C content of plants; wherein, A is soil with pH 5.5, planted with Chinese cabbage; B is soil with pH 5.5, planted with lettuce. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0021] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0022] Experimental materials: (1) Test soil: Soil was taken from the experimental field behind Southwest University of Science and Technology in Mianyang City, Sichuan Province (104°31′E, 31°32′N). After being air-dried naturally, it was ground through a 20-mesh sieve for later use. The original pH value of the soil was 7.68±0.02.

[0023] (2) Titanium gypsum: It is taken from vanadium-titanium tailings in Panzhihua City, Sichuan Province, and aged before use. The pH value of titanium gypsum is 8.14±0.21.

[0024] (3) Sheep manure organic fertilizer: purchased from Stanley Agriculture Group Co., Ltd., with total nutrients (N+P2O5+K2O) ≥4% and organic matter ≥45%.

[0025] (4) Lettuce seeds: purchased from Hebei Manchou Agricultural Technology Co., Ltd.

[0026] (5) Chinese cabbage seeds: purchased from Anhui Jiuqi Seedling Technology Co., Ltd.

[0027] Reagent preparation: (1) 25% (w / w) hydrochloric acid solution: Prepared at a mass ratio of 37% (w / w) hydrochloric acid solution: ultrapure water = 25:12.

[0028] (2) 100 μg / mL glucose solution: Prepared by dissolving 0.0550 g glucose monohydrate in 500 mL of ultrapure water.

[0029] (3) 80% H2SO4: Dilute 28.57 mL of 98% H2SO4 with 6.43 mL of ultrapure water to prepare 35 mL of 80% H2SO4.

[0030] (4) 1.5 g / L anthrone / 80% H2SO4 solution: Prepare according to the ratio of 0.0525 g anthrone dissolved in 35 mL 80% H2SO4. Prepare and use immediately. Store in a brown bottle at 4°C protected from light.

[0031] (5) 1 g / L Vitamin C solution: Prepared at a ratio of 1 g Vitamin C to 1 L of ultrapure water. Before preparing the solution, the ultrapure water must be boiled to remove dissolved oxygen.

[0032] (6) Vitamin C standard solution: Prepared by dissolving 1 mL of 1 g / L vitamin C solution in 10 mL of 2% oxalic acid.

[0033] (7) 0.2 g / L sodium 2,6-dichlorophenolindophenol (DCIP) solution: Prepared at a ratio of 0.05 g DCIP to 250 mL of ultrapure water and stored at 4°C. The ultrapure water used to prepare the solution must be boiled and then cooled to 70°C before use.

[0034] Preparation of acidic soil: Before measuring the soil pH, the pH meter was calibrated using a standard buffer solution. 20 g of soil was taken, and 50 mL of ultrapure water was added to the soil at a ratio of soil:ultrapure water = 2:5. The mixture was magnetically stirred for 2 hours to ensure thorough mixing. After standing for 30 minutes, the supernatant was collected and the pH value was measured using a pH meter. The measured result was the initial pH value of the soil. Subsequently, a certain amount of 25% hydrochloric acid solution was added to the soil-water mixture. Using the pH measurement method described above, the required amount of 25% hydrochloric acid solution to be added when the pH of 20 g of soil was 4.5, 5.5, and 6.5 was determined. Based on the ratio of soil mass to the amount of 25% hydrochloric acid solution added, different volumes of 25% hydrochloric acid solution were added to the test soil to prepare soils with initial pH values ​​of 4.5, 5.5, and 6.5, simulating acidic soils with different degrees of acidification.

[0035] Example 1 A method for preparing a titanium gypsum-sheep manure composite soil conditioner includes: crushing titanium gypsum and sheep manure organic fertilizer separately using a grinder, and mixing the titanium gypsum and sheep manure organic fertilizer thoroughly and evenly at a mass ratio of 2:1 to obtain the titanium gypsum-sheep manure composite soil conditioner.

[0036] Example 2 A method for preparing a titanium gypsum-sheep manure composite soil conditioner includes: crushing titanium gypsum and sheep manure organic fertilizer separately using a grinder, and mixing the titanium gypsum and sheep manure organic fertilizer thoroughly and evenly at a mass ratio of 1:1 to obtain the titanium gypsum-sheep manure composite soil conditioner.

[0037] Example 3 A method for preparing a titanium gypsum-sheep manure composite soil conditioner includes: crushing titanium gypsum and sheep manure organic fertilizer separately using a grinder, and mixing the titanium gypsum and sheep manure organic fertilizer thoroughly and evenly at a mass ratio of 1:2 to obtain the titanium gypsum-sheep manure composite soil conditioner.

[0038] Example 4 A method for preparing a titanium gypsum-sheep manure composite soil conditioner includes the following steps: Step 1: Preparation of modified titanium plaster, including: S11. According to the weight, take 100 parts of titanium gypsum, crush it with a grinder, mix it with 5 parts of rice husk powder and 10 parts of straw powder, add 150 parts of water and stir evenly, let stand for 3 hours, dry and pulverize to obtain mixture A. S12. Heat mixture A to 600℃ at 20℃ / min and hold for 30 min, then heat to 900℃ at 10℃ / min and hold for 1 h, then grind and pulverize to obtain mixture B; S13. Dry and grind the bentonite to obtain bentonite powder; take 10 parts of bentonite powder and add it to 20 parts of 2wt% citric acid aqueous solution, stir evenly, let stand for 6 hours, dry and grind to obtain activated bentonite. S14. Add 10 parts of activated bentonite to mixture B obtained in S12, mix thoroughly and evenly to obtain modified titanium gypsum. Step 2: Crush the sheep manure organic fertilizer with a grinder, and mix the modified titanium gypsum and sheep manure organic fertilizer thoroughly at a mass ratio of 2:1 to obtain titanium gypsum-sheep manure composite soil conditioner.

[0039] Example 5 In this embodiment, the mass ratio of modified titanium gypsum to sheep manure organic fertilizer is 1:1, and the remaining steps are the same as in embodiment 4.

[0040] Example 6 In this embodiment, the mass ratio of modified titanium gypsum to sheep manure organic fertilizer is 1:2, and the remaining steps are the same as in embodiment 4.

[0041] Example 7 A method for preparing a titanium gypsum-sheep manure composite soil conditioner includes the following steps: Step 1: Preparation of modified titanium plaster, including: S11. According to the weight, take 100 parts of titanium gypsum, crush it with a grinder, mix it with 15 parts of straw powder, add 150 parts of water, stir evenly, let stand for 3 hours, dry and pulverize to obtain mixture A. S12. Heat mixture A to 600℃ at 20℃ / min and hold for 30 min, then heat to 900℃ at 10℃ / min and hold for 1 h, then grind and pulverize to obtain mixture B; S13. Dry and grind the bentonite to obtain bentonite powder; take 10 parts of bentonite powder and add it to 20 parts of 2wt% citric acid aqueous solution, stir evenly, let stand for 6 hours, dry and grind to obtain activated bentonite. S14. Add 10 parts of activated bentonite to mixture B obtained in S12, mix thoroughly and evenly to obtain modified titanium gypsum. Step 2: Crush the sheep manure organic fertilizer with a grinder, and mix the modified titanium gypsum and sheep manure organic fertilizer thoroughly at a mass ratio of 2:1 to obtain titanium gypsum-sheep manure composite soil conditioner. Compared to Example 4, the modified titanium gypsum prepared in Example 7 did not contain rice husk powder.

[0042] Example 8 In this embodiment, the mass ratio of modified titanium gypsum to sheep manure organic fertilizer is 1:1, and the remaining steps are the same as in embodiment 7.

[0043] Example 9 In this embodiment, the mass ratio of modified titanium gypsum to sheep manure organic fertilizer is 1:2, and the remaining steps are the same as in embodiment 7.

[0044] Example 10 A method for preparing a titanium gypsum-sheep manure composite soil conditioner includes the following steps: Step 1: Preparation of modified titanium plaster, including: S11. According to the weight, take 100 parts of titanium gypsum, crush it with a grinder, mix it with 15 parts of rice husk powder, add 150 parts of water, stir evenly, let stand for 3 hours, dry and pulverize to obtain mixture A. S12. Heat mixture A to 600℃ at 20℃ / min and hold for 30 min, then heat to 900℃ at 10℃ / min and hold for 1 h, then grind and pulverize to obtain mixture B; S13. Dry and grind the bentonite to obtain bentonite powder; take 10 parts of bentonite powder and add it to 20 parts of 2wt% citric acid aqueous solution, stir evenly, let stand for 6 hours, dry and grind to obtain activated bentonite. S14. Add 10 parts of activated bentonite to mixture B obtained in S12, mix thoroughly and evenly to obtain modified titanium gypsum. Step 2: Crush the sheep manure organic fertilizer with a grinder, and mix the modified titanium gypsum and sheep manure organic fertilizer thoroughly at a mass ratio of 2:1 to obtain titanium gypsum-sheep manure composite soil conditioner. Compared to Example 4, the modified titanium gypsum prepared in Example 10 did not contain straw powder.

[0045] Example 11 In this embodiment, the mass ratio of modified titanium gypsum to sheep manure organic fertilizer is 1:1, and the remaining steps are the same as in embodiment 10.

[0046] Example 12 In this embodiment, the mass ratio of modified titanium gypsum to sheep manure organic fertilizer is 1:2, and the remaining steps are the same as in embodiment 10.

[0047] Example 13 A method for preparing a titanium gypsum-sheep manure composite soil conditioner includes the following steps: Step 1: Preparation of modified titanium plaster, including: S11. According to the weight, take 100 parts of titanium gypsum, crush it with a grinder, mix it with 5 parts of rice husk powder and 10 parts of straw powder, add 150 parts of water and stir evenly, let stand for 3 hours, dry and pulverize to obtain mixture A. S12. Heat mixture A to 600℃ at 20℃ / min and hold for 30 min, then heat to 900℃ at 10℃ / min and hold for 1 h, then grind and pulverize to obtain mixture B; S13. Dry and grind the bentonite to obtain bentonite powder; S14. Add 10 parts of bentonite powder to mixture B obtained in S12, mix thoroughly and evenly to obtain modified titanium gypsum. Step 2: Crush the sheep manure organic fertilizer with a grinder, and mix the modified titanium gypsum and sheep manure organic fertilizer thoroughly at a mass ratio of 2:1 to obtain titanium gypsum-sheep manure composite soil conditioner. Compared to Example 4, the modified titanium gypsum prepared in Example 13 did not undergo citric acid activation treatment of the bentonite.

[0048] Example 14 In this embodiment, the mass ratio of modified titanium gypsum to sheep manure organic fertilizer is 1:1, and the remaining steps are the same as in embodiment 13.

[0049] Example 15 In this embodiment, the mass ratio of modified titanium gypsum to sheep manure organic fertilizer is 1:2, and the remaining steps are the same as in embodiment 13.

[0050] Example 16 A method for preparing a titanium gypsum-sheep manure composite soil conditioner includes the following steps: Step 1: Preparation of modified titanium plaster, including: S11. According to the weight, take 100 parts of titanium gypsum, crush it with a grinder, mix it with 5 parts of rice husk powder and 10 parts of straw powder, add 150 parts of water and stir evenly, let stand for 3 hours, dry and pulverize to obtain mixture A. S12. Heat mixture A to 600℃ at 20℃ / min and hold for 30 min, then heat to 900℃ at 10℃ / min and hold for 1 h, then grind and pulverize to obtain modified titanium gypsum. Step 2: Crush the sheep manure organic fertilizer with a grinder, and mix the modified titanium gypsum and sheep manure organic fertilizer thoroughly at a mass ratio of 2:1 to obtain titanium gypsum-sheep manure composite soil conditioner. Compared to Example 4, the modified titanium gypsum prepared in Example 16 did not contain bentonite.

[0051] Example 17 In this embodiment, the mass ratio of modified titanium gypsum to sheep manure organic fertilizer is 1:1, and the remaining steps are the same as in embodiment 16.

[0052] Example 18 In this embodiment, the mass ratio of modified titanium gypsum to sheep manure organic fertilizer is 1:2, and the remaining steps are the same as in embodiment 16.

[0053] Application Example 1 Application of titanium gypsum-sheep manure composite soil conditioners prepared in Examples 1-3 in improving acidic soils and crop cultivation 1. Pot experiment Take 100 g of acidic soil with an initial pH of 4.5, 5.5, or 6.5, respectively, and add it to pots at a concentration of 3%, 5%, or 7% (i.e., 3 g, 5 g, or 7 g of titanium gypsum-sheep manure composite soil conditioner per 100 g of soil). Mix thoroughly and add to the pots. Sow 10 lettuce or bok choy seeds in each pot on March 12, 2025, and cultivate in a constant temperature greenhouse. Water regularly and uniformly. Harvest after 50 days of cultivation. Three biological replicates are set up for each group.

[0054] 2. Soil pH measurement Before measuring the soil pH, calibrate the pH meter using a standard buffer solution. Take 0.72 g of soil after vegetable planting, add 1.8 mL of ultrapure water to the soil to be tested at a soil:ultrapure water ratio of 2:5, stir magnetically for 2 h to mix thoroughly, let stand for 30 min, and then take the supernatant to measure the pH value through a pH meter. The measured result is the soil pH value.

[0055] 3. Measurement of plant growth indicators Three plants with similar growth were selected from three biological replicates in the same group (one plant from each pot). After gently washing away the soil from the roots with running water, the remaining moisture was absorbed with absorbent paper. Then, the fresh weight, plant height, and taproot length of the samples were measured. The mass of the sample after the above treatment, measured directly using an electronic balance, is the plant fresh weight (g). The straight-line distance from the root collar to the terminal bud of the main stem is the plant stem length (cm), and the straight-line distance from the root collar to the farthest root tip of the taproot is the plant taproot length (cm).

[0056] 4. Determination of soluble sugar content (1) Determination of standard curve Prepare the standard curve reaction system according to Table 1.

[0057] Table 1 Before the reaction, the prepared glucose standard solution was slowly added to 5 mL of 1.5 g / L anthrone / 80% H2SO4. Simultaneously, the reaction system was placed in cold water and shaken to mix. Then, it was boiled in a water bath for 10 min. After cooling to room temperature, the absorbance of the reaction system at 620 nm was measured using a UV spectrophotometer. The standard curve obtained by linear fitting (r=0.9929) is shown below: In the formula, C represents the soluble sugar content (μg / mL); A 620 This represents the absorbance value at 620 nm.

[0058] (2) Sample determination Three plants with similar growth were selected from three biological replicates in the same group (one plant from each pot). After gently washing away the soil from the roots with running water, the residual moisture from the roots was absorbed with absorbent paper. The samples were then placed in an aluminum box and dried in an oven at 80°C until constant weight. The samples were then thoroughly ground with a mortar and pestle, and the dry weight of the samples was determined using an electronic balance. Subsequently, the sample was transferred to 4 mL of 80% ethanol, incubated in an 80°C water bath for 20 min, cooled to room temperature, centrifuged at 8000 rpm for 10 min, and the supernatant was collected. 0.03 g of activated carbon powder was added, and the mixture was shaken on a shaker at room temperature for 15 min, then centrifuged at 1000 rpm for 10 min. The supernatant was collected, and the volume was adjusted to 6 mL with ultrapure water. After thorough mixing, 0.5 mL of the sample solution was slowly added to 2.5 mL of 1.5 g / L anthrone / 80% H2SO4. At the same time, the reaction system was placed in cold water and shaken to mix. Then, the mixture was in a boiling water bath for 10 min, cooled to room temperature, and the absorbance of the reaction system at 620 nm was measured using a UV spectrophotometer. The soluble sugar content of the sample solution (μg / mL) was calculated from this, and the soluble sugar content of the plant (mg / g) was calculated based on the dry weight of the sample.

[0059] 5. Vitamin C content determination (1) Preparation of sample solution Three plants with similar growth were selected from three biological replicates within the same group (one plant from each pot). The roots were gently washed with running water to remove soil, and residual moisture was absorbed with absorbent paper. The samples were then cut into small pieces, and their mass (M) was determined using an electronic balance. The samples were then thoroughly ground into a homogenate in 15 mL of 2% oxalic acid using a mortar. The mortar was pre-cooled at -20°C to minimize vitamin C loss. The extract was collected, and the sample was extracted three times. The extracts from the three extractions were combined, centrifuged at 6000 rpm for 5 min, and the supernatant was filtered. The filtrate was then diluted to 35 mL with 2% oxalic acid. The resulting system is the sample solution.

[0060] (2) DCIP calibration When determining the vitamin C concentration of a sample solution using 0.2 g / L DCIP solution, the DCIP solution must first be standardized. First, titrate 11 mL of vitamin C standard solution with 0.2 g / L DCIP solution until the reaction system changes from colorless to pale pink and does not fade within 15 seconds. Record the volume of DCIP solution used at this point, V1. Then, add 1 mL of ultrapure water to 10 mL of 2% oxalic acid solution, mix thoroughly, and titrate with 0.2 g / L DCIP solution until the reaction system changes from colorless to pale pink and does not fade within 15 seconds. Record the volume of DCIP solution used at this point, V0. The formula for calculating the titer of 0.2 g / L DCIP solution is shown below: In the formula, T represents the titer of the 0.2 g / L DCIP solution (mg / mL); V1 represents the volume of DCIP solution used in the titration of the vitamin C standard solution (mL); and V0 represents the volume of DCIP solution used in the blank titration (mL).

[0061] (3) Sample determination Take 10 mL of sample solution, add 1 mL of ultrapure water, and titrate with a standardized 0.2 g / L DCIP solution until the reaction system changes from colorless to pale pink and does not fade within 15 seconds. Record the volume of DCIP solution used, V2. The formula for calculating the vitamin C content of the sample is as follows: In the formula V c V1 represents the vitamin C content of the sample (g / 100 g); V2 represents the volume of DCIP solution used in the sample titration (mL); V0 represents the volume of DCIP solution used in the blank titration (mL); M represents the mass of the test sample (g).

[0062] 6. Results (1) Effects of different addition methods on soil pH To investigate the differences in the soil conditioning effects of titanium gypsum-sheep manure composite soil conditioner on soils with different acidification levels under different addition amounts and ratios, this invention added 3%, 5%, and 7% of the titanium gypsum-sheep manure composite soil conditioner to soils with pH values ​​of 4.5, 5.5, and 6.5 for planting Chinese cabbage or lettuce, respectively. Soil pH was measured after 50 days, and the results are as follows: Figure 1 As shown.

[0063] Specifically, for the strongly acidic soil with pH 4.5 planted with bok choy, the soil acidification improvement effects were not significantly different at lower addition levels (3% and 5%), with a significant difference only at 7%. At 5% addition level and a 2:1 ratio, the improved soil pH (6.92±0.07) was closer to 7, indicating a better improvement effect. For the weakly acidic soil with pH 5.5 planted with bok choy, the soil acidification improvement effects were not significantly different at higher addition levels (5% and 7%), with a significant difference only at 3%. At 3% addition level and a 1:1 ratio, the soil acidification improvement effect was better (pH=7.05±0.35). For the near-neutral soil with pH 6.5 planted with bok choy, significant differences were observed at all addition levels, with 5% addition level and a 2:1 ratio showing the best soil acidification improvement effect (pH=7.32±0.11).

[0064] Overall, the optimal addition method of the composite soil conditioner can raise the pH of soils with different acidification levels to the optimal pH range of 6.8-7.5, suitable for the growth of most crops, indicating that the titanium gypsum-sheep manure composite soil conditioner has good soil improvement performance for soils with different acidification levels. As the initial pH of acidic soil increases, the pH range of the improved soil also increases. However, even in near-neutral soils with a relatively high initial pH (6.5), the pH of the soil improved by the optimal addition method is still within the optimal pH range, indicating that the alkaline composite soil conditioner mainly improves soil acidification by increasing soil pH, and this pH increase is relatively mild and has good application value. In soils with different acidification levels where Chinese cabbage is planted, the pH of the strongly acidic soil with a pH of 4.5 after improvement by the optimal addition method is closer to 7 (6.92±0.07), indicating that the composite soil conditioner has a particularly significant improvement effect on strongly acidic soils.

[0065] To further expand the application scenarios of compound soil conditioners, pH=5.5, a key critical point for acidic soil improvement with greater practical value, was selected. Compound soil conditioners with different addition methods were used to improve acidic soil used for lettuce cultivation. The results showed that the soil acidification improvement effect was not significantly different at a 5% addition level, but significant differences were observed at 3% and 7% addition levels. The soil acidification improvement performance was better at a 3% addition level and a 2:1 ratio (pH=7.09±0.05), and the soil pH was also within the optimal pH range. This further validated the good acidic soil improvement performance of the compound soil conditioner from the perspective of different crops.

[0066] In summary, the titanium gypsum-sheep manure composite soil conditioner prepared in Examples 1-3 of this invention has excellent and mild soil improvement performance for soils with different degrees of acidification, and has a particularly significant improvement effect on strongly acidic soils with pH=4.5. However, specific addition amounts and ratios must be selected according to different degrees of acidification of the soil to achieve better soil acidification improvement effect. The optimal addition amounts and ratios for improving the pH of acidic soils are shown in Table 2.

[0067] Table 2 (2) Effects of different addition methods on plant fresh weight To investigate the effect of compound soil conditioners on the core basic indicator of crop fresh weight in soils with different acidification levels, soils with pH values ​​of 4.5, 5.5, and 6.5 planted with pakchoi or lettuce were treated with compound soil conditioners added in different ways. The fresh weight of the plants was measured after 50 days. The results are as follows: Figure 2 As shown.

[0068] Specifically, for the relatively acidic soil with pH 4.5 where bok choy is grown, there was no significant difference in the fresh weight of bok choy at 3% and 7% addition levels, with a significant difference only at 5% addition level. The fresh weight of bok choy was greater at 5% addition level and a 1:1 ratio (0.66±0.26 g). For the relatively acidic soil with pH 5.5 where bok choy is grown, the difference in soil acidification improvement effect between 3% and 7% addition levels was still not significant, again with a significant difference only at 5% addition level. The fresh weight of bok choy was greater at 7% addition level and a 1:2 ratio (0.44±0.07 g). For the near-neutral soil with pH 6.5 where bok choy is grown, there was no significant difference in the fresh weight of bok choy at 5% and 7% addition levels, with a significant difference only at 3% addition level. The fresh weight of bok choy was greater at 3% addition level and a 1:2 ratio (0.57±0.22 g).

[0069] Overall, among soils with different levels of acidity for planting Chinese cabbage, the optimal addition method resulted in greater fresh weight of plants in strongly acidic soils with a pH of 4.5. This may be because the pH of the soil after improvement is closer to neutral, which is more suitable for the growth of Chinese cabbage. This confirms the conclusion that compound soil conditioners have a particularly significant effect on improving strongly acidic soils.

[0070] Furthermore, this invention improved the slightly acidic soil (pH=5.5) for lettuce cultivation using compound soil conditioners with different addition methods. The results showed that there was no significant difference in fresh weight of lettuce at a 3% addition level, but significant differences were observed at 5% and 7% addition levels. The fresh weight of lettuce was greater (0.92±0.27 g) at a 7% addition level and a 1:1 ratio, indicating a different response in fresh weight between lettuce and bok choy to the compound soil conditioner with different addition methods.

[0071] In summary, the titanium gypsum-sheep manure composite soil conditioner prepared in Examples 1-3 of this invention has significant potential for crop cultivation after acid soil improvement. The optimal addition amount and ratio for increasing the fresh weight of Chinese cabbage and lettuce in acid soil are shown in Table 3.

[0072] Table 3 (3) Effects of different addition methods on root and stem length of plants To further investigate the effects of compound soil conditioners on crop growth in acidic soil, soil with a pH of 5.5 was treated with compound soil conditioners added in different ways. Root and stem lengths of the plants were measured after 50 days. The results are as follows: Figure 3 As shown.

[0073] The results showed that for slightly acidic soil with a pH of 5.5 where lettuce was grown, there was no significant difference in lettuce root length at 5% addition, but significant differences at 3% and 7% addition. Similarly, there was no significant difference in lettuce stem length at 3% and 7% addition, but significant differences at 5% addition. At a 7% addition and a 1:1 ratio, the lettuce root length was longer (13.41±3.15 cm). At this point, the lettuce stem length (6.02±1.06 cm) was not significantly different from the group with the longest stem length (3% addition, 1:1 ratio, 6.54±0.50 cm) (P=0.246). Furthermore, as mentioned earlier, the lettuce fresh weight was also greater at this point. This indicates that soil improvement with a 7% titanium gypsum-sheep manure composite soil conditioner at a 1:1 ratio is more beneficial for lettuce growth in slightly acidic soil. For slightly acidic soils, the fresh weight of pakchoi (0.32±0.11 g) when the addition amount was 7% and the ratio was 1:1 was not significantly different from that of the group with the highest fresh weight (7% addition amount, 1:2 ratio, 0.44±0.07 g) (P=0.130). This indicates that the soil improvement of the compound soil conditioner with 7% addition amount and 1:1 ratio is also more beneficial to the growth of pakchoi in slightly acidic soils.

[0074] In conclusion, in the cultivation of crops in slightly acidic (pH=5.5) soil, soil improvement with 7% titanium gypsum-sheep manure composite soil conditioner at a 1:1 ratio (Example 2) was generally most beneficial to the growth of bok choy and lettuce.

[0075] (4) Effects of different addition methods on the soluble sugar content of plants To investigate the effect of compound soil conditioners on the soluble sugar content of vegetables in acidic soil, a quality indicator, soil with a pH of 5.5 was treated with compound soil conditioners added in different ways. The soluble sugar content of the plants was measured after 50 days. The results are as follows: Figure 4 As shown.

[0076] The results showed that for slightly acidic soil with a pH of 5.5 where bok choy was grown, there were significant differences in the soluble sugar content of bok choy under different additive amounts. The soluble sugar content of bok choy was higher (32.88±0.61) when the additive amount was 7% and the ratio was 1:1. The results indicate that this addition method of the compound soil conditioner is more beneficial to the accumulation of soluble sugars in pakchoi in slightly acidic soils, which is consistent with the previous conclusion that the 7% addition and 1:1 ratio of the compound soil conditioner is more beneficial to the growth of pakchoi in slightly acidic soils. For slightly acidic soils with a pH of 5.5 where lettuce is grown, there were also significant differences in the soluble sugar content of lettuce at different addition levels. However, the soluble sugar content of lettuce was higher at an addition level of 5% and a ratio of 1:2 (21.64±0.07 mg / g), indicating that this addition method of the compound soil conditioner is more beneficial to the accumulation of soluble sugars in lettuce in slightly acidic soils. The above results show the different responses of lettuce and pakchoi to compound soil conditioners with different addition methods in terms of soluble sugar accumulation.

[0077] In summary, as shown in Table 4, regarding the accumulation of soluble sugars in vegetables in slightly acidic soil with a pH of 5.5, the titanium gypsum-sheep manure composite soil conditioner with an addition amount of 7% and a ratio of 1:1 (Example 2) had a better effect on bok choy, while the titanium gypsum-sheep manure composite soil conditioner with an addition amount of 5% and a ratio of 1:2 (Example 3) had a better effect on lettuce. It is necessary to further explore the effects of composite soil conditioners on other quality indicators of vegetables in acidic soil.

[0078] Table 4 (5) Effects of different addition methods on the vitamin C content of plants To further investigate the effects of compound soil conditioners on the quality indicators of vegetables in acidic soil, soil with a pH of 5.5 planted with pak choi or lettuce was treated with compound soil conditioners added in different ways. The vitamin C content of the plants was measured after 50 days. The results are as follows: Figure 5 As shown.

[0079] The results showed that for slightly acidic soil with a pH of 5.5 where bok choy was grown, there were significant differences in the soluble sugar content of bok choy at different addition levels. The vitamin C content was higher (25.00±0.73 mg / 100 g) when the addition level was 7% and the ratio was 2:1. This indicates that the soil improvement effect of the compound soil conditioner at this addition level was more beneficial to the accumulation of vitamin C in bok choy in slightly acidic soil. This is consistent with the previous conclusion that the soil improvement effect of the 7% addition level of the compound soil conditioner was more beneficial to the growth and soluble sugar accumulation of bok choy in slightly acidic soil. Similarly, for slightly acidic soil with a pH of 5.5 where lettuce was grown, there were also significant differences in the soluble sugar content of lettuce at different addition levels. However, the vitamin C content was higher (232.26±3.95 mg / 100 g) when the addition level was 7% and the ratio was 1:1. (g) indicates that the soil improvement effect of this compound soil conditioner is more favorable for vitamin C accumulation in lettuce in weakly acidic soils, which is consistent with the previous conclusion that the soil improvement effect of the titanium gypsum-sheep manure compound soil conditioner with an addition of 7% and a ratio of 1:1 is more favorable for lettuce growth in weakly acidic soils.

[0080] In summary, as shown in Table 5, in terms of vitamin C accumulation in vegetables in slightly acidic soil with a pH of 5.5, the titanium gypsum-sheep manure composite soil conditioner with an addition amount of 7% and a ratio of 2:1 (Example 1) had a better effect on pak choi, while the titanium gypsum-sheep manure composite soil conditioner with an addition amount of 7% and a ratio of 1:1 (Example 2) had a better effect on lettuce.

[0081] Table 5 This invention uses soils with different acidification levels (pH=4.5, 5.5, 6.5) planted with bok choy or lettuce as the research object. Different amounts (3%, 5%, 7%) and ratios (titanium gypsum: sheep manure = 2:1, 1:1, 1:2) of titanium gypsum-sheep manure composite soil conditioner were applied. Soil pH changes, crop growth indicators such as fresh weight, root length, and stem length, and crop quality indicators such as soluble sugar content and vitamin C content were measured 50 days after sowing. The aim is to explore the soil acidification improvement performance of titanium gypsum-sheep manure composite soil conditioners with different addition methods and the crop planting potential after acid soil improvement, providing theoretical guidance and practical basis for the application of acid soil improvement and the reuse of industrial solid waste titanium gypsum. Details are as follows: (1) Regarding soil acidification improvement, by selecting specific amounts and ratios of titanium gypsum-sheep manure composite soil conditioner to improve acidic soils, the pH values ​​of strongly acidic soils (pH=4.5), weakly acidic soils (pH=5.5), and near-neutral soils (pH=6.5) planted with bok choy or lettuce can be gradually raised to the optimal pH range of 6.8-7.5, suitable for the growth of most crops. Therefore, specific amounts and ratios of composite soil conditioners can be selected according to the different degrees of acidification in acidic soils, thereby effectively improving soil acidification. This improvement effect is particularly significant in strongly acidic soils, where the pH of the improved soil can be restored to 6.92±0.07.

[0082] (2) In terms of crop planting after acid soil improvement, for acid soils with different degrees of acidification, the pH of the improved soil with stronger acidity is closer to neutral, which is more beneficial to the fresh weight index of vegetables. In particular, the 5% addition amount and 1:1 ratio of titanium gypsum-sheep manure composite soil conditioner (Example 2) can make the fresh weight of Chinese cabbage reach 0.66±0.26 g. For improving slightly acidic soils, which has greater practical value, a 7% addition of titanium gypsum-sheep manure composite soil conditioner is more beneficial to the fresh weight of pak choy and its quality indicators such as soluble sugar content and vitamin C content. Specifically, a 1:1 ratio can achieve a fresh weight of 0.32±0.11 g and a soluble sugar content of 32.88±0.61 mg / g for pak choy, while a 2:1 ratio can achieve a vitamin C content of 25.00±0.73 mg / 100 g. Similarly, in improving slightly acidic soils, a 7% addition of a 1:1 ratio of the composite soil conditioner is more beneficial to the fresh weight, root length, and stem length of lettuce, as well as its vitamin C content. In this case, the fresh weight of lettuce can reach 0.92±0.27 g, the root length can reach 13.41±3.15 cm, and the stem length can reach 6.02±1.06 cm. The vitamin C content can reach 232.26±3.95 mg / 100 g, and the 5% addition and 1:2 ratio are more beneficial to the quality indicator of soluble sugar content in lettuce, which can increase the soluble sugar content of lettuce to 21.64±0.07 mg / g. In summary, the titanium gypsum-sheep manure composite soil conditioner prepared in this invention has significant potential for crop cultivation after acid soil improvement.

[0083] Application Example 2 Pot experiments were conducted on the titanium gypsum-sheep manure composite soil conditioners prepared in Examples 4-18, and the results are shown in Tables 6-9. Table 6 shows the improvement effects of Examples 4-5 on acidic soil with pH=5.5. It can be seen that, under the same ratio and dosage, the titanium gypsum-sheep manure composite soil conditioners prepared in Examples 4 and 5 improved the pH of the acidic soil with pH=5.5 to a level closer to 7, showing better improvement effects compared to Examples 1-2. The remaining examples showed similar improvement effects on acidic soil, all able to moderately raise the pH value of the acidic soil to the suitable growth range of 6.8-7.5 for crops.

[0084] The fresh weight, soluble sugar content, and vitamin C content of pakchoi in acidic soil with pH=5.5 are shown in Tables 7-9. It can be seen that, under the same ratio and amount of additives, the fresh weight and quality of pakchoi in Examples 4-18 are improved compared with Examples 1-3, with Examples 4-6 being the best.

[0085] Table 6 Table 7 Table 8 Table 9 Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a titanium gypsum-sheep manure composite soil conditioner, characterized in that, include: Titanium gypsum and sheep manure organic fertilizer are crushed and mixed evenly to obtain titanium gypsum-sheep manure composite soil conditioner.

2. The preparation method of the titanium gypsum-sheep manure composite soil conditioner as described in claim 1, characterized in that, The mass ratio of titanium gypsum to sheep manure organic fertilizer is 1~2:1~2.

3. The preparation method of the titanium gypsum-sheep manure composite soil conditioner as described in claim 1, characterized in that, The titanium plaster is replaced with a modified titanium plaster; the method for preparing the modified titanium plaster includes the following steps: S11. After crushing the titanium gypsum, mix it with rice husk powder and straw powder, add water and stir evenly, let it stand, dry and crush it to obtain mixture A. S12. Calcine mixture A and grind it to obtain mixture B; S13. Dry and grind the bentonite to obtain bentonite powder; add the bentonite powder to a citric acid aqueous solution, stir evenly, let stand, dry and grind to obtain activated bentonite; S14. Add activated bentonite to mixture B obtained in S12 and mix evenly to obtain modified titanium gypsum.

4. The preparation method of the titanium gypsum-sheep manure composite soil conditioner as described in claim 3, characterized in that, In step S11, the mass ratio of titanium gypsum, rice husk powder, straw powder and water is 100:1~10:5~15:120~200; let stand for 2~5 hours.

5. The preparation method of the titanium gypsum-sheep manure composite soil conditioner as described in claim 3, characterized in that, In S12, the specific conditions for calcination treatment are as follows: heat up to 500-700℃ at a rate of 10-30℃ / min and hold for 20-60min, then heat up to 850-950℃ at a rate of 5-15℃ / min and hold for 40-90min.

6. The preparation method of the titanium gypsum-sheep manure composite soil conditioner as described in claim 3, characterized in that, In S13, the concentration of the citric acid aqueous solution is 1~3wt%.

7. The preparation method of the titanium gypsum-sheep manure composite soil conditioner as described in claim 3, characterized in that, In step S13, the mass ratio of bentonite powder to citric acid aqueous solution is 1:1.5~3; and the mixture is allowed to stand for 4~8 hours.

8. The preparation method of the titanium gypsum-sheep manure composite soil conditioner as described in claim 3, characterized in that, In S14, the mass ratio of activated bentonite to titanium gypsum in S11 is 1~3:

20.

9. The application of a titanium gypsum-sheep manure composite soil conditioner prepared by any one of claims 1-8 in the remediation of acidic soil.

10. The application of a titanium gypsum-sheep manure composite soil conditioner prepared by the preparation method according to any one of claims 1-8 in promoting plant growth.

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