Conditioner for improving acid buffer capacity of soil and preparation method thereof

Abstract

The invention discloses a conditioner for improving the acid buffer capacity of soil and a preparation method of the conditioner. The preparation method comprises the following steps: sequentially adding dolomite powder, montmorillonite powder and charcoal powder into a gelatin solution, and uniformly dispersing to form mixed slurry; adding a cross-linking agent glutaraldehyde solution into the mixed slurry, uniformly stirring and mixing, then pouring into a silica gel mold, standing, solidifying and forming, and washing and drying a formed product to obtain the conditioner for improving the acid buffer capacity of the soil. The conditioner disclosed by the invention can improve the acid environment of soil for a long time, prevent re-acidification of the soil and increase nutrient elements such as Ca and Mg in the soil, and the preparation method is simple and mild in reaction.

Description

Technical Field

[0001] This invention belongs to the field of soil improvement technology, specifically relating to a conditioner for improving soil acid buffering capacity and its preparation method. Background Technology

[0002] As soil acidification intensifies, H + The increased content leads to the accumulation of Ca adsorbed on soil colloids. 2+ Mg 2+ K + Competitive exchange of isobasic cations accelerates their leaching, leading to soil nutrient depletion and decreased fertility. Furthermore, H+ in acidic soils... + Increased aluminum activity in soil, leading to Al 3+ Accumulation and toxicity can harm soil microorganisms and plant growth. Of particular concern is that the soil's own acid buffering capacity is a key factor in resisting acidification and maintaining soil pH stability. This capacity is closely related to components such as alkaline substances, clay minerals, and organic matter in the soil, and it helps neutralize H+. + Through adsorption and cation exchange, soil acid buffering agents can mitigate drastic fluctuations in soil pH. However, under the dual pressures of human and natural factors, the original acid buffering substances in the soil are continuously consumed, and the acid buffering capacity continues to decline, further weakening the soil's resistance to acidification. This creates a vicious cycle of "intensified acidification—decreased buffering capacity—more prone to acidification," making soil acidification an even more difficult problem to manage.

[0003] To date, besides preventing soil acidification through methods such as acid sedimentation and controlling fertilizer application, the main approach to improving already acidified soils is to apply soil conditioners, which offer advantages such as simple operation and significant effects. Currently, CN119351113A discloses a biochar-based soil conditioner and its preparation method. The main technical invention involves emulsifying gelatin and chitosan using a microemulsion method to obtain a gelatin-chitosan composite emulsion, which is then reacted with modified biochar to obtain the biochar-based soil conditioner. In addition, some studies have combined gelatin (GL), chitosan (CS), magnesium ammonium phosphate (MAP), and humic acid (FA) to prepare GL / CS / MAP-FA soil conditioner microspheres with a core-shell structure via an emulsion crosslinking method (Youzhi, W., Jincheng, W., Shiqiang, S., Pinhua, R., Runkai, W., Shihui, L., Liqi, X., &Feng, Z. Preparation and application properties of sustainable gelatin / chitosan soil conditioner microspheres. International Journal of Biological Macromolecules, 2020, 159, 685-695.). The above-mentioned soil conditioners are all prepared using the emulsion crosslinking method. Although the material is formed by crosslinking gelatin and glutaraldehyde, emulsifiers and liquid paraffin need to be introduced in the process, and multiple washings are required to remove impurities. The overall operation is quite complicated. In addition, it is difficult to accurately control the size of the product, which can easily lead to uneven particle size and affect the stability of the application effect. Furthermore, its slow-release function is not combined with the needs of improving acidic soil.

[0004] It is worth noting that CN119490373A discloses a soil conditioner suitable for acidic yellow soil, its preparation method, and its application. The main technical invention involves mixing straw biochar, organic fertilizer, dolomite, kaolinite, superphosphate, zeolite, humic acid, microbial fertilizer, and earthworm castings in a specific ratio to prepare a soil conditioner suitable for improving acidic yellow soil. CN118956409A discloses an acidic soil conditioner, its preparation method, and its application. The main technical invention involves calcining and grinding oyster shells and mixing them with modified biochar and quicklime to prepare a carbon-based acidifier; crushing and sieving at least one of attapulgite, montmorillonite, and dolomite to prepare a mineral-based conditioner; mixing three types of bacteria in a specific ratio to prepare a microbial preparation; and then mixing and coating the three components. These technologies can effectively neutralize soil acidity and increase soil pH, but their effects on improving soil acid buffering capacity and maintaining long-term soil pH stability are limited. Therefore, developing specialized conditioners that can improve soil pH and enhance soil acid buffering capacity is of great significance for improving acidic soils, enriching soils, and promoting high-quality and high-yield crops.

[0005] Gelatin is widely used as an encapsulation material due to its high safety, good water absorption, and recyclability. Adding gelatin significantly promotes soil microorganisms and increases soil mineral nitrogen content, improving soil health indicators and nutrient levels. It can also be used as a plant growth stimulant and biostimulant. Dolomite is an abundant carbonate mineral, mainly composed of calcium magnesium carbonate (CaMg(CO3)2), and it continuously releases CO3. 2- / HCO3 - This effectively increases soil pH. Furthermore, the calcium and magnesium cations in dolomite can dissolve and release into acidic soils, increasing soil nutrient content, improving soil productivity, and enhancing crop agronomic traits. Montmorillonite is a 2:1 type mineral; isomorphous substitution within its octahedral sheets imparts a negative charge, giving it strong ion exchange and adsorption capabilities, adsorbing large amounts of cations, including H+. + NH4 + Immobilized within montmorillonite, biochar enhances soil acid buffering capacity and reduces soil acidity. The porous structure and oxygen-containing functional groups on the surface of biochar increase cation adsorption, thereby improving soil cation exchange capacity and enhancing soil acid buffering capacity. Simultaneously, the release of strongly alkaline substances from biochar directly increases soil pH. By encapsulating dolomite, biochar, and montmorillonite in gelatin and cross-linking them, a three-dimensional network structure is obtained, enabling the controlled release of pH buffering components and maintaining long-term pH stability. Summary of the Invention

[0006] This invention discloses a conditioner for improving soil acid buffering capacity and its preparation method.

[0007] This invention innovatively introduces glutaraldehyde as a gelatin crosslinking agent, enabling gelatin to form a stable three-dimensional network structure through a crosslinking reaction. On one hand, this significantly improves the conditioner's resistance to degradation and structural stability in soil, avoiding the problems of easy decomposition and rapid functional failure of traditional organic matrices; on the other hand, the three-dimensional network allows for precise control of functional components (such as Ca). 2+ Mg 2+ The release rate of the substance is controlled to achieve "slow release and long-lasting effect," thus addressing the industry problem of soil "re-acidification" after short-term conditioning.

[0008] Meanwhile, the use of silicone mold forming technology allows for flexible adjustment of the shape and size of the conditioner according to the needs of different soil types and farming scenarios. This facilitates mechanized application, adapts to different soil pore structures, improves the contact efficiency between the conditioner and the soil, and further optimizes the acid buffering effect.

[0009] The conditioner of this invention can improve the soil acidity environment in the long term, prevent soil re-acidification, and increase soil nutrients such as Ca and Mg. Moreover, the preparation method is simple and the reaction is mild.

[0010] The technical solution of the present invention is as follows: A conditioner for improving soil acid buffering capacity is prepared by the following method: (1) Preparation of gelatin solution: Dissolve gelatin in deionized water to obtain gelatin solution; The specific steps are as follows: Mix gelatin with deionized water, place it in a water bath at 40-70°C, and stir continuously for 0.5-1 hour until the gelatin is completely dissolved to obtain a gelatin solution; The preferred mass fraction of the obtained gelatin solution is 1-10%; (2) Preparation of mixed slurry: Under stirring conditions, dolomite powder, montmorillonite powder and biochar powder are added to the gelatin solution obtained in step (1) in sequence and dispersed evenly (preferably stirred for 1 to 3 hours) to form a mixed slurry; Dolomite powder, montmorillonite powder, and biochar powder should be ground and sieved through a 60-200 mesh before use; The preferred mass ratio of dolomite powder, montmorillonite powder, biochar powder, and gelatin is (3-6):(0-4):1:3; (3) Crosslinking molding and post-treatment: Add crosslinking agent to the mixed slurry obtained in step (2), stir and mix evenly, then pour into a silicone mold, let stand to solidify and form, and wash and dry the molded product to obtain the conditioner that improves the acid buffering capacity of the soil. The crosslinking agent is a glutaraldehyde solution, preferably with a glutaraldehyde solution mass fraction of 25%; The preferred volume ratio of glutaraldehyde solution to gelatin solution in step (1) is (1-3): 1000; The preferred size of the silicone mold is (5-10) × (5-10) × (5-10) mm; The preferred temperature for static solidification is 10–30°C, and the preferred time is 3–5 hours.

[0011] The beneficial effects of this invention are as follows: This invention innovatively constructs a three-dimensional network structure through gelatin cross-linking technology, organically combining biochar, dolomite, and montmorillonite to form a synergistic and multi-pH buffer system. This system can not only effectively improve the acidic environment of the soil, but also alleviate the problem of soil re-acidification.

[0012] The core advantage of this conditioner lies in its multi-component synergistic mechanism: the porous structure of biochar and the high cation exchange capacity of montmorillonite form a dual adsorption barrier, which can efficiently capture excess H2 in the soil. + Dolomite, on the other hand, continuously releases CO3. 2- / HCO3 - It provides long-lasting neutralization capabilities, and the synergistic effect of the three significantly enhances the soil's resistance to exogenous acidification, greatly improves the soil's acid buffering capacity, and effectively slows down the rapid drop in pH value.

[0013] Meanwhile, the invention uses silicone mold forming technology, which can precisely control the product size and shape, making it easy to standardize production and flexibly adjust the application method according to different soil conditions.

[0014] In addition, this conditioner has the characteristics of strong compound stability and simple and easy preparation process. It is convenient to operate in practical applications and can continuously and efficiently improve the acid buffering capacity of soil, providing an ideal solution for the long-term management of acidic soil. Attached Figure Description

[0015] Figure 1 : Buffering capacity diagram of soil conditioner in Examples 1-4 of this invention with dolomite and biochar.

[0016] Figure 2 Acid buffering capacity diagram of soil conditioners in Examples 5-8 of this invention. Detailed Implementation

[0017] The present invention is further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0018] In the following embodiments, The natural dolomite and montmorillonite come from Qingyang County, Anhui Province; The biochar is made from corn stalks and originates from Zhengzhou, Henan Province.

[0019] Example 1

[0020] (1) Take dolomite and biochar, grind them through an 80-mesh sieve to obtain dolomite powder and biochar powder; (2) Weigh 3g of gelatin and mix it with 97g of deionized water. Heat the mixture in a water bath at 60℃ and stir for 0.5h to obtain a 3wt.% gelatin solution. (3) Weigh the dolomite powder and biochar powder obtained in step (1), 3g of dolomite and 1g of biochar, add them to the gelatin solution obtained in step (2) in sequence, stir at 60℃ for 1.5h to obtain a mixed slurry; (4) Add 0.1 mL of 25% glutaraldehyde solution to the mixed slurry obtained in step (3), stir evenly, pour it into a silicone mold while hot, the silicone mold has a single size of 5×5×5 mm; solidify at room temperature, wash, dry, and obtain soil conditioner.

[0021] Example 2

[0022] (1) Take dolomite and biochar, grind them through an 80-mesh sieve to obtain dolomite powder and biochar powder; (2) Weigh 3g of gelatin and mix it with 97g of deionized water. Heat the mixture in a water bath at 60℃ and stir for 0.5h to obtain a 3wt.% gelatin solution. (3) Weigh the dolomite powder and biochar powder obtained in step (1), 4g dolomite and 1g biochar, add them to the gelatin solution obtained in step (2) in sequence, stir at 60℃ for 1.5h to obtain a mixed slurry; (4) Add 0.1 mL of 25% glutaraldehyde solution to the mixed slurry obtained in step (3), stir evenly, pour it into a silicone mold while hot, the silicone mold has a single size of 5×5×5 mm; solidify at room temperature, wash, dry, and obtain soil conditioner.

[0023] Example 3

[0024] (1) Take dolomite and biochar, grind them through an 80-mesh sieve to obtain dolomite powder and biochar powder; (2) Weigh 3g of gelatin and mix it with 97g of deionized water. Heat the mixture in a water bath at 60℃ and stir for 0.5h to obtain a 3wt.% gelatin solution. (3) Weigh the dolomite powder and biochar powder obtained in step (1), 5g dolomite and 1g biochar, add them to the gelatin solution obtained in step (2) in sequence, stir at 60℃ for 1.5h to obtain a mixed slurry; (4) Add 0.1 mL of 25% glutaraldehyde solution to the mixed slurry obtained in step (3), stir evenly, pour it into a silicone mold while hot, the silicone mold has a single size of 5×5×5 mm; solidify at room temperature, wash, dry, and obtain soil conditioner.

[0025] Example 4

[0026] (1) Take dolomite and biochar, grind them through an 80-mesh sieve to obtain dolomite powder and biochar powder; (2) Weigh 3g of gelatin and mix it with 97g of deionized water. Heat the mixture in a water bath at 60℃ and stir for 0.5h to obtain a 3wt.% gelatin solution. (3) Weigh the dolomite powder and biochar powder obtained in step (1), 6g of dolomite and 1g of biochar, add them to the gelatin solution obtained in step (2) in sequence, stir at 60℃ for 1.5h to obtain a mixed slurry; (4) Add 0.1 mL of 25% glutaraldehyde solution to the mixed slurry obtained in step (3), stir evenly, pour it into a silicone mold while hot, the silicone mold has a single size of 5×5×5 mm; solidify at room temperature, wash, dry, and obtain soil conditioner.

[0027] Example 5

[0028] (1) Take dolomite, biochar and montmorillonite, grind them through an 80-mesh sieve to obtain dolomite powder, montmorillonite powder and biochar powder; (2) Weigh 3g of gelatin and mix it with 97g of deionized water. Heat the mixture in a water bath at 60℃ and stir for 0.5h to obtain a 3wt.% gelatin solution. (3) Weigh the dolomite powder, montmorillonite powder and biochar powder obtained in step (1), 3g dolomite, 1g biochar and 1g montmorillonite, add them to the gelatin solution obtained in step (2) in sequence, stir at 60℃ for 1.5h to obtain a mixed slurry; (4) Add 0.1 mL of 25% glutaraldehyde solution to the mixed slurry obtained in step (3), stir evenly, pour it into a silicone mold while hot, the silicone mold has a single size of 5×5×5 mm; solidify at room temperature, wash, dry, and obtain soil conditioner.

[0029] Example 6

[0030] (1) Take dolomite, biochar and montmorillonite, grind them through an 80-mesh sieve to obtain dolomite powder, montmorillonite powder and biochar powder; (2) Weigh 3g of gelatin and mix it with 97g of deionized water. Heat the mixture in a water bath at 60℃ and stir for 0.5h to obtain a 3wt.% gelatin solution. (3) Weigh the dolomite powder, montmorillonite powder and biochar powder obtained in step (1), 3g dolomite, 1g biochar and 2g montmorillonite, add them to the gelatin solution obtained in step (2) in sequence, stir at 60℃ for 1.5h to obtain a mixed slurry; (4) Add 0.1 mL of 25% glutaraldehyde solution to the mixed slurry obtained in step (3), stir evenly, pour it into a silicone mold while hot, the silicone mold has a single size of 5×5×5 mm; solidify at room temperature, wash, dry, and obtain soil conditioner.

[0031] Example 7

[0032] (1) Take dolomite, biochar and montmorillonite, grind them through an 80-mesh sieve to obtain dolomite powder, montmorillonite powder and biochar powder; (2) Weigh 3g of gelatin and mix it with 97g of deionized water. Heat the mixture in a water bath at 60℃ and stir for 0.5h to obtain a 3wt.% gelatin solution. (3) Weigh the dolomite powder, montmorillonite powder and biochar powder obtained in step (1), 3g dolomite, 1g biochar and 3g montmorillonite, add them to the gelatin solution obtained in step (2) in sequence, stir at 60℃ for 1.5h to obtain a mixed slurry; (4) Add 0.1 mL of 25% glutaraldehyde solution to the mixed slurry obtained in step (3), stir evenly, pour it into a silicone mold while hot, the silicone mold has a single size of 5×5×5 mm; solidify at room temperature, wash, dry, and obtain soil conditioner.

[0033] Example 8

[0034] (1) Take dolomite, biochar and montmorillonite, grind them through an 80-mesh sieve to obtain dolomite powder, montmorillonite powder and biochar powder; (2) Weigh 3g of gelatin and mix it with 97g of deionized water. Heat the mixture in a water bath at 60℃ and stir for 0.5h to obtain a 3wt.% gelatin solution. (3) Weigh the dolomite powder, montmorillonite powder and biochar powder obtained in step (1), 3g dolomite, 1g biochar and 4g montmorillonite, add them to the gelatin solution obtained in step (2) in sequence, stir at 60℃ for 1.5h to obtain a mixed slurry; (4) Add 0.1 mL of 25% glutaraldehyde solution to the mixed slurry obtained in step (3), stir evenly, pour it into a silicone mold while hot, the silicone mold has a single size of 5×5×5 mm; solidify at room temperature, wash, dry, and obtain soil conditioner.

[0035] Implementation Results

[0036] Acid buffering capacity was determined for Examples 1-8, dolomite, and biochar. 0.5 g of each sample was weighed and placed into seven 50 mL centrifuge tubes. 0.2 mol / L HNO3 was added in gradient volumes (0, 0.5, 1.0, 2.0, 4.0, 6.0, and 8.0 mL), followed by the addition of deionized water to a final volume of 20 mL. The pH of the solution was measured using a pH meter, and then the solution was shaken at 25°C for 2 hours. A curve was plotted based on the test results.

[0037] according to Figure 1 and Figure 2 It is known that, generally, a flatter acid titration curve indicates a stronger acid buffering capacity, while a steeper curve indicates a lower acid buffering capacity. When the system pH value decreased from 5.0 to 4.0, and when the system pH value decreased from 5.5 to 4.0, the curves of the soil conditioners in the eight examples compared to the raw materials (dolomite and biochar) were flatter, indicating that their acid buffering capacity was stronger. The results show that by constructing a three-dimensional network structure through gelatin cross-linking to encapsulate biochar, dolomite, and montmorillonite, the pH buffering components are slowly released, delaying the sudden drop in pH under exogenous acidic conditions, and demonstrating good acid buffering capacity.

Claims

1. A conditioner for improving the acid buffer capacity of soil, characterized in that, The improved soil acid buffering capacity conditioner is prepared by the following method: (1) Gelatin solution preparation: gelatin is dissolved in deionized water to obtain a gelatin solution; (2) Mixed slurry preparation: under stirring, dolomite powder, montmorillonite powder and biochar powder are sequentially added into the gelatin solution obtained in step (1) and uniformly dispersed to form a mixed slurry; (3) Crosslinking molding and post-treatment: a crosslinking agent is added into the mixed slurry obtained in step (2) and uniformly mixed under stirring, and then poured into a silica gel mold, and the molded product is washed and dried to obtain the improved soil acid buffering capacity conditioner. The crosslinking agent is a glutaraldehyde solution.

2. The conditioner for modifying the acid buffer capacity of soil according to claim 1, wherein Step (1) is performed as follows: gelatin and deionized water are mixed and placed in a water bath at 40-70°C, and continuously stirred for 0.5-1 h until the gelatin is completely dissolved to obtain a gelatin solution.

3. The conditioner for modifying the acid buffer capacity of soil according to claim 1, wherein The mass fraction of the gelatin solution obtained in step (1) is 1-10%.

4. The conditioner for modifying the acid buffer capacity of soil according to claim 1, wherein In step (2), the mass ratio of dolomite powder, montmorillonite powder, biochar powder and gelatin is (3-6):(0-4):1:

3.

5. The conditioner for modifying the acid buffer capacity of soil according to claim 1, wherein In step (3), the mass fraction of the glutaraldehyde solution is 25%.

6. The conditioner for modifying the acid buffer capacity of soil according to claim 1, wherein In step (3), the volume ratio of the glutaraldehyde solution to the gelatin solution of step (1) is (1-3):1000.

7. The conditioner for modifying the acid buffer capacity of soil according to claim 1, wherein In step (3), the size of the silica gel mold is (5-10)×(5-10)×(5-10) mm.

8. The conditioner for modifying the acid buffer capacity of soil according to claim 1, wherein In step (3), the temperature for standing and solidifying molding is 10-30°C, and the time is 3-5 h.

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