Soil conditioner for saline-alkali soil and soil improvement method

Abstract

The invention belongs to the technical field of soil improvement, and relates to a soil conditioner for saline-alkali soil and a soil improvement method. The soil conditioner comprises vinegar residues, chitin, glucose, a composite biological preparation, a modified gel and a functional additive, the composite biological agent comprises bacillus subtilis powder, bacillus licheniformis powder, trichoderma spore powder, brown algae powder and light calcium carbonate; the functional auxiliary agent comprises modified bentonite, polyglutamic acid, pregelatinized starch and biochar potassium humate. Through the synergistic effect of multiple components and structural design optimization, systematic remediation of physical properties, chemical properties and biological activity of the saline-alkali soil is achieved. According to the technology, the limitation of single function of a traditional improvement measure is broken through, and the long-standing technical problems of return salt rebound, low fertility, microbial community imbalance and the like in saline-alkali soil treatment are effectively solved by constructing a multi-layer and multi-dimensional soil improvement system.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil improvement, and relates to a soil conditioner for saline-alkali land and a soil improvement method. Background Art

[0002] Globally, soil salinization has become an important challenge restricting the sustainable development of agriculture. With the intensification of climate change and unreasonable water resource utilization, the abnormal accumulation of salts in the soil has led to a significant decline in land productivity, especially in arid and semi-arid regions, where this problem is more prominent. Salinization not only weakens the water and fertilizer retention capacity of the soil, but also destroys the microbial community structure, forming a vicious cycle that gradually makes the originally arable land lose its agricultural value. Although traditional improvement measures such as water conservancy projects and the application of organic fertilizers have been widely used, they still face problems such as high costs, unstable effects, or ecological side effects in actual operation. For example, over-reliance on chemical conditioners may cause secondary pollution, while physical remediation methods are difficult to apply on a large scale. Therefore, the development of new soil improvement technologies with high efficiency, environmental friendliness, and economic feasibility has become a key direction that urgently needs to be broken through in the current fields of agriculture and environmental science. Summary of the Invention

[0003] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a soil conditioner for saline-alkali land and a soil improvement method. Through the synergistic action of multiple components and the optimization of structural design, the systematic repair of the physical properties, chemical properties, and biological activities of saline-alkali soil is achieved. This technology breaks through the single-function limitation of traditional improvement measures. By constructing a multi-level and multi-dimensional soil improvement system, it effectively solves the long-existing technical problems in saline-alkali land treatment, such as salt return and rebound, low fertility, and microbial community imbalance.

[0004] To achieve this purpose, the present invention adopts the following technical solutions:

[0005] In the first aspect, the present invention provides a soil conditioner for saline-alkali land, and the soil conditioner includes vinegar residue, chitin, glucose, compound biological agent, modified gelling agent, and functional auxiliary agent.

[0006] The compound biological agent includes Bacillus subtilis powder, Bacillus licheniformis powder, Trichoderma spore powder, brown algae powder, and light calcium carbonate.

[0007] The functional auxiliary agent includes modified bentonite, polyglutamic acid, pregelatinized starch, biochar, and potassium humate.

[0008] The preparation of the modified gelling agent includes treating montmorillonite with quaternary ammonium salt to obtain intercalated montmorillonite, and then reacting acrylic acid, sodium alginate, and N,N'-methylenebisacrylamide to obtain a reaction product solution; then dispersing the intercalated montmorillonite in the reaction product solution to obtain a precursor solution, and reacting with calcium chloride solution to obtain the modified gelling agent.

[0009] The present invention provides a soil conditioner for saline-alkali soil improvement and its supporting application method. Its core advantage lies in achieving systematic restoration of the physical properties, chemical properties, and biological activity of saline-alkali soil through the synergistic action of multiple components and structural design optimization. This technology breaks through the single-function limitation of traditional improvement measures and effectively solves long-existing technical problems such as salt return and rebound, low fertility, and microbial community imbalance in saline-alkali soil treatment by constructing a multi-level and multi-dimensional soil improvement system.

[0010] The soil conditioner provided by the present invention combines organic materials and functional materials. Among them, vinegar residue, as the main source of organic matter, is rich in lignin, cellulose and other difficult-to-degrade components, and gradually mineralizes under the action of microorganisms to release small molecule organic acids, which can not only reduce the soil pH value, but also chelate free salt ions. Chitin activates the activity of native microorganisms in the soil through its unique biostimulation effect. At the same time, its degradation product chitosan can form a natural polymer network to enhance the stability of soil aggregates. Glucose, as a rapid carbon source, provides energy for functional microorganisms, promotes their rapid colonization and initiates metabolic activities. The multi-strain synergistic system (Bacillus subtilis, Bacillus licheniformis, Trichoderma viride) in the compound biological agent forms a complete functional chain from phosphorus and potassium solubilization to antibacterial and disease resistance. Among them, bacteria of the genus Bacillus secrete extracellular enzymes to decompose organic matter and release essential nutrients for plants, while Trichoderma viride inhibits the reproduction of pathogenic bacteria through antagonistic effects and constructs a healthy rhizosphere microenvironment. The combined action of fucoidan and light calcium carbonate in brown algae powder forms a microporous structure while adjusting the soil pH, improving soil permeability. After the modified bentonite in the functional auxiliary agent is intercalated and modified with cetyltrimethylammonium bromide, its layer spacing expands to the nanometer level, significantly increasing the cation exchange capacity, which can effectively adsorb Na+, K+ and other ions in the soil. Combined with the molecular chain entanglement effect of polyglutamic acid, a dynamic salt buffer system is formed to prevent salts from migrating to the surface and aggregating with water.

[0011] The preparation process of the modified gelling agent endows the material with unique microscopic structure and functional characteristics. Through ultrasonic stripping and intercalation modification of nano-montmorillonite, a layered structure with a high specific surface area is formed, providing rich active sites for subsequent polymerization reactions. The neutralization reaction of acrylic acid and sodium hydroxide generates a hydrophilic backbone of sodium polyacrylate, and sodium alginate forms an elastic network under the cross-linking action of N,N'-methylenebisacrylamide. After the two are compounded and blended with intercalated montmorillonite, through Ca 2+Trigger a cross-linking reaction, ultimately forming composite gel particles with a three-dimensional interconnected pore structure. This structure can not only maintain long-term stability in the soil but also continuously hold water through capillary action, forming a "miniature reservoir" under drought conditions, while relieving soil compaction through gel swelling during waterlogging. The freeze-drying process retains the three-dimensional network structure of the gel, enabling it to slowly degrade after being applied to the soil, achieving the dual goals of long-term salt control and slow-release fertilizer supply.

[0012] In terms of the application plan, the present invention regulates the dosage and application method of the soil conditioner according to the degree of salinization, reflecting the concept of precise treatment. For severely saline-alkali soil (pH value > 9), high-dose and enhanced deep improvement are adopted. The soil conditioner is distributed in the topsoil and plow layer through two separate applications, combined with backfilling deep pits, which can effectively break the hard salt crust, promote the soil conditioner to penetrate deep into the soil body, and reconstruct the soil profile structure. For moderately and slightly saline-alkali soil (pH value = 7 - 9), a strategy of gradually decreasing dosage and layered mixing application is adopted. By adjusting the ratio of the first and second soil conditioners, the nutrient release rate and the diffusion range of microorganisms are controlled to avoid excessive activation of surface salts. This differential application mode not only ensures the timeliness of the improvement effect but also takes into account economy and environmental safety.

[0013] The action mechanism of the soil conditioner provided by the present invention presents a multi-dimensional synergistic effect: on the one hand, the elastic skeleton formed by the modified gelling agent improves the soil pore distribution, reduces the bulk density, increases the total porosity, and enhances the soil compressive strength, fundamentally changing the poor properties of saline-alkali soil such as "muddy when wet and hard when dry". On the other hand, the organic acids produced by the composite biological agent and the ion exchange effect of bentonite form a dual salt reduction system, reducing the content of exchangeable sodium ions in the surface soil by 40 - 60%, and the pH value steadily decreasing by 0.5 - 1.2 units. At the same time, a Ca 2 +-humic acid complex is formed to passivate the activity of heavy metals. On the other hand, functional microorganisms promote soil enzyme activity through metabolic activities, accelerate the process of organic matter mineralization, and form a benign material cycle. The plant hormones (such as IAA) and antibiotics (such as chitinase) secreted by them can effectively promote the root development of crops and enhance the stress resistance.

[0014] As a preferred technical solution of the present invention, based on 100 parts by weight of the soil conditioner, it includes the following components in parts by weight:

[0015]

[0016] Among them, the weight parts of the vinegar residue can be 40 parts, 40.5 parts, 41 parts, 41.5 parts, 42 parts, 42.5 parts, 43 parts, 43.5 parts, 44 parts, 44.5 parts or 45 parts; the weight parts of chitin can be 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts or 10 parts; the weight parts of glucose can be 3.0 parts, 3.2 parts, 3.4 parts, 3.6 parts, 3.8 parts, 4.0 parts, 4.2 parts, 4.4 parts, 4.6 parts, 4.8 parts or 5.0 parts; the weight parts of the composite biological agent can be 15 parts, 15.5 parts, 16 parts, 16.5 parts, 17 parts, 17.5 parts, 18 parts, 18.5 parts, 19 parts, 19.5 parts or 20 parts; the weight parts of the modified gelling agent can be 15 parts, 15.5 parts, 16 parts, 16.5 parts, 17 parts, 17.5 parts, 18 parts, 18.5 parts, 19 parts, 19.5 parts or 20 parts; the weight parts of the functional auxiliary agent can be 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts or 15 parts, but are not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0017] As an organic matter carrier and also the main carbon source, the lignin and cellulose components of the vinegar residue are gradually decomposed under the action of microorganisms. The released organic acids can not only effectively reduce the soil pH value, but also fix free salt ions through chelation. The mineralization process of the vinegar residue can continuously release small molecule organic acids, reducing the content of exchangeable sodium ions in the soil by 40 - 60%. Chitin is hydrolyzed through β-1,4-glycosidic bonds to form chitosan, forming a natural polymer network and enhancing the stability of soil aggregates. Its unique biostimulation effect can activate the activity of native soil microorganisms and induce a 2 - 3-fold increase in the expression levels of plant defense enzymes (such as PAL, POD). The acid-base regulation ability of the vinegar residue and the natural polymer network formed by chitin complement each other, and there is a synergistic effect between them. The chitosan produced by the degradation of chitin can enhance the stability of soil aggregates, and its biostimulation effect further activates the native microbial community. Under the synergistic action of the two, the soil compressive strength is significantly improved, effectively improving the physical dilemma of saline-alkali land being "muddy when wet and hard when dry".

[0018] A small amount of glucose is also added to the soil conditioner of the present invention. As a highly active carbon source, glucose provides instant energy for functional microorganisms (such as Bacillus spp., Trichoderma spp., etc.), promoting their rapid colonization and initiating metabolic activities. In addition, glucose can also promote the secretion efficiency of phosphorus- and potassium-solubilizing enzymes (such as alkaline phosphatase, glucanase) by regulating the carbon-nitrogen metabolic balance of microorganisms. At the same time, under anaerobic conditions, glucose participates in the sulfate reduction reaction as an electron donor, indirectly reducing the soil redox potential, inhibiting denitrification, and reducing nitrogen loss.

[0019] In severely saline-alkali soil with pH > 9, glucose and the modified gelling agent form a "carbon-structure" synergistic system. Glucose promotes the rapid colonization of microorganisms in the gel, accelerates the accumulation of organic matter in the gel pores, and extends the gel life by 2 - 3 years. In moderately and mildly saline-alkali soil (pH value = 7 - 8), the gradient dosage design (0.5 - 1.5 tons per mu) matches the glucose metabolism rate with the soil respiration intensity, avoiding denitrification losses caused by carbon overload.

[0020] In the composite biological agent, phosphorus- and potassium-solubilizing functional groups (such as Bacillus) secrete extracellular enzymes to decompose mineral phosphorus and potassium, providing readily available nutrients for plants. The biocontrol antagonistic system (such as Trichoderma) secretes chitinase to inhibit the reproduction of pathogenic bacteria, constructing a healthy rhizosphere microenvironment. This clearly divided combination of microorganisms forms a complete functional chain from nutrient release to disease prevention and control. There is also a synergistic effect between brown algae powder and light calcium carbonate. Fucoidan in brown algae powder forms a microporous structure while regulating the pH, and light calcium carbonate stabilizes the pH value through a neutralization reaction. The synergy between the two makes the soil pore distribution more reasonable, with the air permeability increased by more than 30%.

[0021] Regarding the modified gelling agent, through the ultrasonic exfoliation and intercalation modification of nano-montmorillonite, the material layer spacing is expanded to the nanoscale, providing abundant active sites for subsequent polymerization reactions. The neutralization reaction between acrylic acid and sodium hydroxide generates a hydrophilic backbone, and sodium alginate forms an elastic network under the action of a cross-linking agent. After the two are compounded and blended with intercalated montmorillonite, composite gel particles with a three-dimensional interconnected pore structure are finally formed. This structure shows excellent water absorption performance, with a saturated water absorption rate of over 500%. At the same time, it can slowly release water under drought conditions, forming a "miniature reservoir". The freeze-drying process retains the three-dimensional network structure of the gel, enabling it to slowly degrade in the soil and achieving the dual goals of long-term salt control and slow-release fertilizer supply.

[0022] In some alternative examples, taking 100 parts by weight of the composite biological agent as the basis, it includes the following components in parts by weight:

[0023]

[0024] Among them, the parts by weight of the Bacillus subtilis powder can be 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts or 35 parts; the parts by weight of the Bacillus licheniformis powder can be 20 parts, 20.5 parts, 21 parts, 21.5 parts, 22 parts, 22.5 parts, 23 parts, 23.5 parts, 24 parts, 24.5 parts or 25 parts; the parts by weight of the Trichoderma spore powder can be 15 parts, 15.5 parts, 16 parts, 16.5 parts, 17 parts, 17.5 parts, 18 parts, 18.5 parts, 19 parts, 19.5 parts or 20 parts; the parts by weight of the brown algae powder can be 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts or 15 parts; the parts by weight of the light calcium carbonate can be 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts or 15 parts. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0025] As the core functional module of the saline-alkali soil conditioner, the compound biological agent constructs a whole-chain functional system from organic matter decomposition to nutrient activation and from pathogen antagonism to ecological restoration through the mechanism of multi-strain cooperation and nutritional complementarity.

[0026] As phosphorus- and potassium-solubilizing functional bacteria, the Bacillus subtilis powder and the Bacillus licheniformis powder secrete alkaline phosphatase and glucanase respectively to convert insoluble apatite and potassium feldspar in the soil into phosphate ions (H2PO4 - / HPO4 2- ), and available potassium (K+) that can be absorbed by plants. This biochemical conversion ability directly determines the biological availability of phosphorus and potassium elements in saline-alkali soil.

[0027] Bacillus subtilis quickly decomposes organic matter (such as lignocellulose in vinegar residues), releases metabolic intermediates such as α-ketoglutaric acid, and provides a carbon source for antagonistic bacteria such as Trichoderma. In addition, the extracellular polysaccharide (EPS) secreted by Bacillus subtilis and the fucoidan of brown algae powder form a composite colloid network, enhancing the water stability of soil aggregates.

[0028] The lipopeptide substances (such as iturin) secreted by Bacillus licheniformis can not only inhibit pathogenic bacteria, but also enhance the survival ability of Bacillus under salt stress by regulating the cell membrane osmotic pressure; in addition, the lipopeptide substances of Bacillus licheniformis and the fucoidan of brown algae powder form a synergistic micelle structure, making the surface charge distribution of the soil tend to be uniform and reducing the electrostatic adsorption potential energy of sodium ions. When the salt concentration reaches 8‰, the synergistic effect of Bacillus licheniformis increases the survival rate of Bacillus to more than 80%, ensuring its continuous metabolic activity in extreme environments. This salt tolerance characteristic enables the composite biological agent to maintain functional stability in strongly alkaline soil with pH>9.

[0029] The addition of Trichoderma spore powder constructs a biological control barrier. By secreting chitinase and glucanase, it specifically targets and destroys the cell walls of pathogenic fungi (such as Fusarium and Phytophthora), forming a natural biological barrier. This antagonistic mechanism not only directly inhibits the reproduction of pathogenic bacteria, but also enhances the self-defense ability of crops by inducing systemic resistance in plants. In addition, as a decomposer functional bacterium, Trichoderma can efficiently degrade complex organic matters in the soil (such as cellulose and lignin). The cellulase secreted by it can convert macromolecular organic matters into oligosaccharides and monosaccharides, providing a carbon source for its own growth and promoting the mineralization process of soil organic matter. At the same time, the metabolites of Trichoderma (such as γ-aminobutyric acid and gibberellin) also have plant physiological regulation functions. γ-aminobutyric acid can relieve the oxidative damage of plants under salt stress and increase the proline accumulation; gibberellin promotes the elongation of hypocotyls and enhances the stress resistance of seedlings. This dual effect increases the survival rate of crops under saline-alkali stress by 2-3 times.

[0030] The combination of brown algae powder and light calcium carbonate exhibits physical-chemical dual regulation functions. The fucoidan in brown algae powder forms a natural colloid during degradation, which can adsorb sodium ions on the surface of soil colloids. Its molecular weight distribution is complementary to that of light calcium carbonate, expanding the pH buffering range of calcium carbonate to 7.5-8.5. This combination effectively avoids the problem of soil compaction caused by simple lime improvement. At the same time, the gelation property of brown algae polysaccharide and the microporous structure of calcium carbonate work together to increase the soil porosity in the improved area by 18-22%.

[0031] The present invention particularly limits the weight portion of the Bacillus subtilis powder to 25-35 parts. As the core phosphorus-solubilizing functional bacterium, the alkaline phosphatase activity secreted by Bacillus subtilis is non-linearly positively correlated with the population density. When the dosage of the Bacillus subtilis powder is less than 25 parts, the enzyme activity is not sufficient to effectively hydrolyze the stable apatite minerals in the soil, resulting in a decrease in the phosphorus activation efficiency; while when the dosage of the Bacillus subtilis powder exceeds 35 parts, the organic acids produced by the metabolism of the bacteria accumulate excessively, which will instead inhibit the activities of itself and other beneficial bacterial populations, and may break the population balance inside the compound biological agent due to carbon source competition. In addition, the salt tolerance characteristics of Bacillus are closely related to its quorum sensing mechanism. The dosage of 25-35 parts can maintain the optimal concentration range of the quorum sensing signal molecules, ensuring the cooperative metabolism efficiency of the bacterial population in an environment with pH>9.

[0032] In addition, Bacillus subtilis releases monosaccharides by decomposing the lignocellulose in the vinegar residue, which not only provides energy for itself but also provides growth intermediates for Bacillus licheniformis, forming a metabolic synergy of the "phosphorus-solubilizing - antagonistic" functional chain. When the dosage of the Bacillus subtilis powder is insufficient, this synergy weakens, resulting in a decrease in the inhibition rate of the antagonistic bacterium against the pathogenic bacterium; when the Bacillus subtilis powder is excessive, the over-accumulation of ammonium nitrogen is caused by the imbalance of the carbon-nitrogen ratio, which is instead not conducive to crop absorption.

[0033] The present invention particularly limits the weight portion of the Bacillus licheniformis powder to 20-25 parts. The lipopeptide substances (such as iturin) secreted by Bacillus licheniformis can enhance the membrane fluidity and transmembrane ion transport efficiency of Bacillus under salt stress by regulating the synthesis of phosphatidylcholine in the cell membrane. When the dosage of the Bacillus licheniformis powder is less than 20 parts, the secretion amount of the lipopeptide substances is not sufficient to form an effective membrane protection layer, resulting in a decrease in the ATPase activity of Bacillus in an environment with pH>9 and a reduction in the metabolic rate; while when the dosage of the Bacillus licheniformis powder exceeds 25 parts, the lipopeptide substances will non-specifically bind to the alkaline phosphatase secreted by Bacillus subtilis, inhibiting the exposure of the catalytic site of the enzyme and causing a 12-15% decrease in the phosphorus activation efficiency. In addition, the metabolites of Bacillus licheniformis (such as γ-polypeptide) have a dynamic regulatory effect on the quorum sensing signal molecules. The dosage of 20-25 parts can maintain the signal molecule concentration in the threshold range of 1.2-1.8 nM, ensuring the synchronous metabolic rhythm of the Bacillus community.

[0034] In addition, Bacillus licheniformis degrades the cellulose in the vinegar residue into oligosaccharides through the secreted glucanase, providing a carbon source for Bacillus subtilis. Under the synergistic action of the two, the efficiency of increasing the content of available phosphorus in the soil is 40% higher than that of a single bacterial species. When the dosage of the Bacillus licheniformis powder is insufficient, the glucanase activity is limited, resulting in incomplete decomposition of cellulose and affecting the carbon source supply chain; excessive addition of the Bacillus licheniformis powder will squeeze the living space of other functional bacteria (such as Trichoderma) due to carbon metabolism competition, causing a 20-30% decrease in the abundance of the antagonistic bacterium.

[0035] In some optional examples, based on 100 parts by weight of the functional auxiliary agent, it includes the following components in parts by weight:

[0036]

[0037] The modified bentonite is sodium bentonite intercalated and modified with cetyltrimethylammonium bromide.

[0038] Among them, the parts by weight of the modified bentonite can be 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts or 40 parts; the parts by weight of polyglutamic acid can be 15 parts, 15.5 parts, 16 parts, 16.5 parts, 17 parts, 17.5 parts, 18 parts, 18.5 parts, 19 parts, 19.5 parts or 20 parts; the parts by weight of pregelatinized starch can be 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts or 15 parts; the parts by weight of biochar can be 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts or 15 parts; the parts by weight of potassium humate can be 15 parts, 15.5 parts, 16 parts, 16.5 parts, 17 parts, 17.5 parts, 18 parts, 18.5 parts, 19 parts, 19.5 parts or 20 parts. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0039] After the modified bentonite is intercalated and modified with cetyltrimethylammonium bromide, its layer spacing expands from 1.2 nm of natural bentonite to 3.8 - 4.5 nm, and the cation exchange capacity is increased to 120 - 150 meq / 100 g, forming efficient adsorption sites for alkali metal ions such as Na+ and K+. This modification not only enhances the ion exchange ability, but also the introduction of its hydrophobic groups reduces the surface energy of clay particles, making the bentonite not easily agglomerate in saline-alkali environments, and the dispersibility is increased by 3 - 5 times.

[0040] As a biostimulant, polyglutamic acid has abundant carboxyl and amino groups on its molecular chain, which can bind to soil colloids through hydrogen bonds and ionic bonds to form a dynamic salt buffer system. In a strongly alkaline environment with pH > 9, the γ-carboxyl group of polyglutamic acid preferentially binds to Na+ to form a reversible complex, delaying the migration rate of sodium ions to crop roots. Its molecular weight distribution (80 - 120 kDa) and the small molecular fragments of potassium humate (<5 kDa) are complementary to construct a wide-band ion adsorption network, increasing the efficiency of reducing exchangeable sodium ions in the soil by 40%.

[0041] As a quick-acting carbon source, the pregelatinized starch forms a porous structure after gelatinization, providing attachment sites for functional microorganisms. Three days after inoculation, it can increase the soil microbial biomass carbon by 1.5 to 2 times. Its α-1,4 glycosidic bonds are gradually degraded under the action of microorganisms, releasing monosaccharides such as glucose, which not only provides energy for Bacillus but also promotes the mineralization of soil organic matter through the glycolysis pathway. The addition of pregelatinized starch maintains the C / N ratio of the modifier at 25 to 30, effectively avoiding the ammonia volatilization loss caused by the carbon-nitrogen imbalance of pure organic materials.

[0042] Biochar, with its developed pore structure (specific surface area of 800 - 1200 m 2 / g) and surface negative charge characteristics, forms a natural "ion sieve", and the adsorption capacity for heavy metals such as Cd 2+ , Pb 2+ reaches 120 - 150 mg / g. The quinone groups, phenolic hydroxyl groups and other active groups formed by its polycyclic aromatic hydrocarbon structure during pyrolysis can undergo π-π conjugation with the aromatic structure of potassium humate, forming a stable organic-inorganic complex, which increases the heavy metal passivation efficiency by 2 - 3 times. The micropores of biochar also provide a shelter for microorganisms, and can still maintain 60 - 70% of the microbial activity under long-term drought conditions.

[0043] Potassium humate undergoes a complexation reaction with soil minerals through its active functional groups (such as carboxyl groups and phenolic hydroxyl groups), converting insoluble elements such as Fe, Al, and Ca into plant-available forms. Its molecular weight distribution (300 - 20000 Da) forms a gradient adsorption with polyglutamic acid. The large molecular fragments preferentially occupy the large pores, and the small molecular fragments penetrate into the micropores, realizing the hierarchical regulation of pore space. The addition of potassium humate increases the content of soil water-stable aggregates by 25 - 30%, and the average diameter of the aggregates increases from 0.82 mm to 1.25 mm, significantly improving the soil permeability.

[0044] The synergistic effect among the components is reflected in the three-dimensional construction of the functional network. Among them, modified bentonite and polyglutamic acid form a "physical adsorption - chemical complexation" double barrier, which can increase the sodium ion adsorption capacity to 3.2 meq / g in a soil environment with pH > 9; the carbon source supply of pregelatinized starch enables the rapid proliferation of the microbial community, and its metabolites (such as organic acids) in turn promote the activation of potassium humate, forming a carbon-nutrient cycle loop; the porous structure of biochar and the layered structure of bentonite complement each other, increasing the overall porosity of the modifier to 58 - 62%, and improving the soil air permeability by 40 - 50%.

[0045] The present invention specifically limits the weight portion of the modified bentonite to 30-40 parts. After the modified bentonite is intercalated and modified with cetyltrimethylammonium bromide, the interlayer spacing is expanded to 3.8-4.5 nm, forming an efficient ion adsorption channel. When the dosage of the modified bentonite is less than 30 parts, the density of the effective adsorption sites provided by it is insufficient, and it is difficult to cover the surface of the saline-alkali soil colloid, resulting in a decrease in the sodium ion adsorption efficiency. Especially in a strong alkaline environment with pH>9, ion exchange saturation easily occurs between the layers of the insufficiently modified bentonite, triggering the phenomenon of sodium ion rebound. At the same time, its synergistic effect with polyglutamic acid depends on a specific mass ratio. When the dosage of bentonite is insufficient, the carboxyl groups of polyglutamic acid cannot be fully anchored on the surface of the bentonite, and the construction of the dynamic salt buffer system is blocked, and the long-term stability of the soil exchangeable sodium ions is difficult to maintain.

[0046] In addition, adding 30-40 parts of the modified bentonite can form an ideal physical barrier structure. The hydrophobic group modification of the modified bentonite enables it to maintain dispersion in the saline-alkali environment and avoid agglomeration, so as to be uniformly dispersed in the soil particle gaps and construct a stable ion adsorption network. If the dosage of the modified bentonite exceeds 40 parts, the excessive bentonite particles will generate steric hindrance due to electrostatic repulsion, hindering the uniform distribution of other functional components (such as composite biological agents, pregelatinized starch), resulting in limited microbial activity and insufficient carbon source supply. In addition, although the layered structure of bentonite can increase the porosity, excessive filling will compress the proportion of large soil pores, instead reducing the air permeability and affecting root respiration and microbial metabolism.

[0047] It should be noted that the modified bentonite used in the present invention is prepared by the following method:

[0048] First, disperse sodium-based bentonite in ethanol (volume fraction 95%) to prepare a bentonite suspension with a mass fraction of 5-10 wt%.

[0049] Secondly, add cetyltrimethylammonium bromide to the bentonite suspension. The addition amount of cetyltrimethylammonium bromide is 1-3 wt% of the mass of the bentonite, and ultrasonically treat it at 500-600 W for 10-15 min.

[0050] Finally, stir and react for 4-6 h, centrifuge and separate, wash with ethanol 3 times, and dry to constant weight.

[0051] As a preferred technical solution of the present invention, the modified gelling agent is prepared by the following method:

[0052] (Ⅰ) Disperse montmorillonite in ethanol and ultrasonically disperse it, add cetyltrimethylammonium bromide and ultrasonically exfoliate it, centrifuge, wash and dry the centrifuged precipitate to obtain intercalated montmorillonite;

[0053] (II) Acrylic acid is mixed with sodium hydroxide solution to obtain an acrylic acid monomer solution; sodium alginate is mixed with water to obtain a sodium alginate solution, and then N,N'-methylenebisacrylamide is added and ultrasonicated to obtain a mixed solution; the acrylic acid monomer solution is added to the mixed solution, and the mixture is stirred and heated to react to obtain a reaction product solution. Intercalated montmorillonite is dispersed in the reaction product solution to obtain a precursor solution;

[0054] (III) Calcium chloride solution is added to the precursor solution, stirred evenly, and allowed to stand and solidify to obtain a composite gel, which is washed, dried, pulverized, and sieved to obtain the modified gelling agent.

[0055] As a preferred technical solution of the present invention, the modified gelling agent is prepared by the following method:

[0056] (I) Nanometer montmorillonite is dispersed in absolute ethanol and ultrasonically dispersed to obtain a montmorillonite suspension. Cetyltrimethylammonium bromide is added to the montmorillonite suspension, and ultrasonic peeling is carried out, followed by centrifugation. The precipitate obtained after centrifugation is washed and dried to obtain intercalated montmorillonite;

[0057] (II) Acrylic acid monomer is dropped into sodium hydroxide solution, and after mixing evenly, an acrylic acid monomer solution is obtained; sodium alginate is dissolved in deionized water to obtain a sodium alginate solution. N,N'-methylenebisacrylamide is added to the sodium alginate solution, and after ultrasonic treatment, a mixed solution is obtained; under a nitrogen atmosphere, the acrylic acid monomer solution is dropped into the mixed solution. After all are dropped, mixing and stirring are carried out and heating is carried out to react. After the reaction is completed, a reaction product solution is obtained. The intercalated montmorillonite obtained in step (I) is dispersed in the reaction product solution to obtain a precursor solution;

[0058] (III) Under heating conditions, calcium chloride solution is dropped into the precursor solution obtained in step (II). After all are dropped, mixing and stirring are carried out evenly, and then standing and solidifying are carried out to obtain a composite gel; the composite gel is washed, freeze-dried, pulverized and sieved to obtain the modified gelling agent.

[0059] There is a synergistic effect between the modified gelling agent and polyglutamic acid, and an ion barrier can be formed. The layered structure of nanometer montmorillonite provides physical adsorption sites, combined with the molecular chain entanglement of polyglutamic acid, to form a selective adsorption barrier for Na+ and K+. In a strong alkaline environment with pH>9, the adsorption capacity of the gel for sodium ions can reach 2.8 meq / g, effectively reducing the content of exchangeable sodium ions in the soil (the reduction range is 40-60%).

[0060] The synergistic effect between the modified gelling agent and light calcium carbonate can form a pH buffer system, through Ca 2+- The humic acid complex passivates the activity of heavy metals, stabilizing the soil pH value in the range of 7.5 - 8.5. This buffering capacity enables the soil conditioner to maintain a pH fluctuation of less than 0.3 units after heavy rainfall or irrigation.

[0061] In addition, the elastic structure of the modified gelling agent generates pore pressure during water absorption and swelling, promoting the migration of deep soil salts to the leaching layer. In combination with the ion exchange effect of the modified bentonite, the salt leaching efficiency can be increased by 50 - 60%.

[0062] In the process of preparing the modified gelling agent, first, the ultrasonic exfoliation and intercalation modification of nano - montmorillonite break the layered stacking structure of natural montmorillonite. Through the intercalation of cetyltrimethylammonium bromide, the layer spacing expands to the nanoscale, significantly enhancing the specific surface area and cation exchange capacity of the material. This structural transformation not only enhances the adsorption capacity of montmorillonite for ions such as Na+ and K+, but also provides abundant active sites for its subsequent composite with organic polymers, enabling the gel system to rapidly form a stable ion barrier in the saline - alkali environment.

[0063] In the process of constructing the acrylic acid - sodium alginate composite gel, through precise regulation of the cross - linking reaction between acrylic acid monomers and sodium alginate, an interpenetrating network structure with both hydrophilicity and elasticity is formed. The polyacrylate backbone generated after the neutralization of acrylic acid monomers with sodium hydroxide provides good hydrophilicity and water - retaining capacity, while the three - dimensional network formed by sodium alginate under the cross - linking action of N,N'-methylenebisacrylamide endows the gel with excellent mechanical strength and compressive properties. This double - network structure design enables the gel to maintain shape stability during water absorption and swelling, avoiding structural disintegration due to excessive water absorption, and still maintaining a certain mechanical strength after dehydration, effectively preventing soil compaction.

[0064] The cross - linking and curing process induced by calcium chloride further optimizes the microstructure of the gel. Through the titration of calcium chloride solution, calcium ions undergo an ion cross - linking reaction with the carboxylate groups of sodium alginate, significantly enhancing the salt tolerance and anti - degradation ability of the gel. This cross - linking effect not only enhances the long - term stability of the gel in saline - alkali soil, but also controls the swelling rate of the gel by adjusting the calcium ion concentration, enabling it to slowly release water under dry conditions and rapidly absorb water and swell under waterlogged conditions, forming a dynamic soil pore regulation mechanism. In addition, the introduction of the freeze - drying process preserves the integrity of the three - dimensional network structure of the gel, avoiding pore collapse caused by high - temperature drying, so that the gel can still maintain a loose and porous morphology after being applied to the soil, providing a suitable micro - environment for microbial activities and root growth.

[0065] The modified gelling agent prepared by the present invention has both high-efficient ion adsorption capacity, excellent water and fertilizer retention performance, and long-term soil structure improvement function. Its unique pore structure and dynamic water absorption and release characteristics can not only effectively reduce the soil salt content, but also improve the soil permeability, promote nutrient cycling, and ultimately achieve the systematic restoration of the physical, chemical, and biological properties of saline-alkali land.

[0066] As a preferred technical solution of the present invention, in step (Ⅰ), the mass fraction of nano-montmorillonite in the montmorillonite suspension is 2-4 wt%, for example, it can be 2.0 wt%, 2.2 wt%, 2.4 wt%, 2.6 wt%, 2.8 wt%, 3.0 wt%, 3.2 wt%, 3.4 wt%, 3.6 wt%, 3.8 wt% or 4.0 wt%, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0067] In some alternative examples, the ultrasonic power of the ultrasonic dispersion is 200-300 W, for example, it can be 200 W, 210 W, 220 W, 230 W, 240 W, 250 W, 260 W, 270 W, 280 W, 290 W or 300 W, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0068] In some alternative examples, the ultrasonic time of the ultrasonic dispersion is 40-50 min, for example, it can be 40 min, 41 min, 42 min, 43 min, 44 min, 45 min, 46 min, 47 min, 48 min, 49 min or 50 min, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0069] In some alternative examples, the mass ratio of nano-montmorillonite to cetyltrimethylammonium bromide in the montmorillonite suspension is (1-1.5):1, for example, it can be 1.0:1, 1.05:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, 1.35:1, 1.4:1, 1.45:1 or 1.5:1, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0070] In some alternative examples, the ultrasonic power of the ultrasonic exfoliation is 500-600 W, for example, it can be 500 W, 510 W, 520 W, 530 W, 540 W, 550 W, 560 W, 570 W, 580 W, 590 W or 600 W, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0071] The present invention specifically limits the ultrasonic exfoliation process to 500-600W. Ultrasonic exfoliation breaks down the van der Waals forces between montmorillonite layers through the synergistic effects of mechanical shear force and cavitation. When the ultrasonic power is below 500W, the acoustic energy is insufficient to overcome the interlayer electrostatic repulsion, resulting in insufficient exfoliation (the interlayer spacing can only be expanded to 1.5-2.0nm), making it difficult for the nano-montmorillonite to meet the specific surface area and cation exchange site density required for modification. Furthermore, when the ultrasonic power exceeds 600W, the excessive cavitation effect causes excessive fragmentation of the montmorillonite layers, destroying the integrity of the layered structure and reducing the flake diameter to submicron or even nanometer levels. While this increases the specific surface area, the hydroxyl activity at the edges of the flakes increases, making agglomeration more likely to occur, which in turn reduces the efficiency of subsequent intercalation modification.

[0072] Furthermore, a power range of 500–600 W achieved dual optimization of interlayer spacing and lamellar structure. Within this range, ultrasonic energy steadily expanded the interlayer spacing of the montmorillonite to 3.8–4.5 nm, preserving the macroscopic dimensions of the lamellars while providing sufficient interlayer space to accommodate the cetyltrimethylammonium bromide intercalation molecules. This structural characteristic enables the modified montmorillonite to retain sodium ions from the soil through physical adsorption, while also enhancing its interfacial compatibility with the acrylic acid-sodium alginate composite gel due to its regular lamellar arrangement. Insufficient ultrasonic power limits the interlayer spacing, restricting the diffusion of the intercalant molecules and reducing the ion exchange capacity of the modified gel. Excessive ultrasonic power, however, results in excessive exfoliation of the lamellars, leading to pore collapse during water absorption and expansion due to disordered lamellar stacking, thus reducing water retention.

[0073] In some optional examples, the ultrasonic time of the ultrasonic stripping is 2 to 3 hours, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0074] In some optional examples, the centrifugal speed is 8000-10000 rpm, for example, it can be 8000 rpm, 8200 rpm, 8400 rpm, 8600 rpm, 8800 rpm, 9000 rpm, 9200 rpm, 9400 rpm, 9600 rpm, 9800 rpm or 10000 rpm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0075] In some alternative examples, the centrifugation time is 15 to 25 min, such as 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min or 25 min, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0076] In some alternative examples, the drying temperature is 40 to 50 °C, such as 40 °C, 41 °C, 42 °C, 43 °C, 44 °C, 45 °C, 46 °C, 47 °C, 48 °C, 49 °C or 50 °C, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0077] In some alternative examples, the drying time is 12 to 24 h, such as 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h or 24 h, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0078] As a preferred technical solution of the present invention, in step (II), the mass fraction of the sodium hydroxide solution is 1 to 3 wt%, such as 1.0 wt%, 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt%, 2.0 wt%, 2.2 wt%, 2.4 wt%, 2.6 wt%, 2.8 wt% or 3.0 wt%, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0079] In some alternative examples, the molar ratio of the acrylic monomer to sodium hydroxide in the sodium hydroxide solution is 1:1.

[0080] In some alternative examples, the mass fraction of sodium alginate in the sodium alginate solution is 2 to 4 wt%, such as 2.0 wt%, 2.2 wt%, 2.4 wt%, 2.6 wt%, 2.8 wt%, 3.0 wt%, 3.2 wt%, 3.4 wt%, 3.6 wt%, 3.8 wt% or 4.0 wt%, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0081] In some alternative examples, the mass ratio of sodium alginate to N,N'-methylenebisacrylamide in the sodium alginate solution is 100:(1 to 2), for example, it can be 100:1.0, 100:1.1, 100:1.2, 100:1.3, 100:1.4, 100:1.5, 100:1.6, 100:1.7, 100:1.8, 100:1.9 or 100:2.0, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0082] In some alternative examples, the mass ratio of the acrylic monomer in the acrylic monomer solution to N,N'-methylenebisacrylamide in the mixed solution is 100:(1 to 2), for example, it can be 100:1.0, 100:1.1, 100:1.2, 100:1.3, 100:1.4, 100:1.5, 100:1.6, 100:1.7, 100:1.8, 100:1.9 or 100:2.0, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0083] In some alternative examples, the dropping rate of the acrylic monomer solution is 2 to 5 mL / min, for example, it can be 2.0 mL / min, 2.5 mL / min, 3.0 mL / min, 3.5 mL / min, 4.0 mL / min, 4.5 mL / min or 5.0 mL / min, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0084] In some alternative examples, the mixing and stirring time of the acrylic monomer solution and the mixed solution is 40 to 50 min, for example, it can be 40 min, 41 min, 42 min, 43 min, 44 min, 45 min, 46 min, 47 min, 48 min, 49 min or 50 min, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0085] In some alternative examples, the heating temperature during the mixing and stirring of the acrylic monomer solution and the mixed solution is 50 to 60 °C, for example, it can be 50 °C, 51 °C, 52 °C, 53 °C, 54 °C, 55 °C, 56 °C, 57 °C, 58 °C, 59 °C or 60 °C, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0086] In some alternative embodiments, the ratio of the intercalated montmorillonite to the reaction product solution is (1 - 2) g: 1 mL. For example, it can be 1.0 g: 1 mL, 1.1 g: 1 mL, 1.2 g: 1 mL, 1.3 g: 1 mL, 1.4 g: 1 mL, 1.5 g: 1 mL, 1.6 g: 1 mL, 1.7 g: 1 mL, 1.8 g: 1 mL, 1.9 g: 1 mL or 2.0 g: 1 mL. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0087] The present invention particularly defines that the ratio of the intercalated montmorillonite to the reaction product solution is (1 - 2) g: 1 mL. The nanosheet structure of montmorillonite needs to be fully dispersed in the organic solvent to effectively intercalate and composite with the acrylic acid - sodium alginate monomer. When the dosage of the intercalated montmorillonite is too low, the distribution of its layered structure in the reaction system shows a discrete state, resulting in too long a diffusion path for the intercalating agent molecules (such as cetyltrimethylammonium bromide), making it difficult to form a continuous nanoscale intercalated structure, and ultimately affecting the selective adsorption ability of the gel for sodium ions. When the dosage of the intercalated montmorillonite is too high, the high - concentration montmorillonite sheets are prone to agglomeration due to electrostatic repulsion and steric hindrance, destroying the homogeneity of the reaction system, resulting in a defective structure with uneven pore distribution inside the composite gel, and reducing its compressive strength and water absorption kinetics performance.

[0088] In addition, the nanosheets of montmorillonite can not only form a stable interpenetrating network with the sodium polyacrylate backbone through hydrogen - bonding interactions, but also provide uniform nucleation sites for the cross - linking reaction of sodium alginate, enabling the gel to maintain a regular pore structure when swelling by absorbing water. This structural feature enables the gel to slowly release water under arid conditions and quickly absorb excessive salts during waterlogging. If the dosage of the intercalated montmorillonite is too low, the ion - blocking ability and water - retention persistence of the gel will decrease significantly; if the dosage of the intercalated montmorillonite is too high, the pores will be blocked due to the stacking of the sheets, reducing the swelling - shrinkage cycle efficiency of the gel, and it is prone to failure due to structural fatigue during long - term use.

[0089] As a preferred technical solution of the present invention, in step (III), the mass fraction of calcium chloride in the calcium chloride solution is 2 - 5 wt%. For example, it can be 2.0 wt%, 2.5 wt%, 3.0 wt%, 3.5 wt%, 4.0 wt%, 4.5 wt% or 5.0 wt%. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0090] The present invention particularly defines that the mass fraction of calcium chloride in the calcium chloride solution is 2 - 5 wt%. Calcium chloride acts as a cross - linking agent and undergoes an ionic cross - linking reaction with the carboxyl groups of sodium alginate to form a three - dimensional elastic network. When the concentration of calcium chloride is lower than 2 wt%, Ca 2+ and the carboxyl groups of sodium alginate undergo an ionic cross - linking reaction, forming a three - dimensional elastic network. When the concentration of calcium chloride is lower than 2 wt%, Ca 2+The crosslinking density is insufficient, resulting in a large number of unclosed pores in the gel network. After absorbing water, the structure is prone to disintegration due to mechanical stress, and the water retention performance decreases. When the concentration of calcium chloride exceeds 5 wt%, excessive Ca 2+ will cause excessive crosslinking, making the gel network tend to be rigid, reducing the pore connectivity, and hindering the dynamic transport of water and ion exchange.

[0091] In addition, the calcium chloride solution with a concentration of 2-5 wt% enables the gel to maintain a compressive strength of 0.8-1.2 MPa in the dry state, effectively resisting the compaction effect of tillage machinery. When swelling after absorbing water, its pore structure can rapidly expand to more than 50 times the original volume, forming an efficient salt buffering space. If the concentration of the calcium chloride solution is too low, the compressive strength of the gel in saline-alkali soil is insufficient, and it is easily compacted, resulting in deteriorated air permeability. If the concentration of the calcium chloride solution is too high, it will cause a decrease in the gel porosity, inhibiting microbial activity and root growth.

[0092] In some alternative examples, the heating temperature during the dropping process of the calcium chloride solution is 40-50 °C, for example, it can be 40 °C, 41 °C, 42 °C, 43 °C, 44 °C, 45 °C, 46 °C, 47 °C, 48 °C, 49 °C or 50 °C, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0093] In some alternative examples, the dropping rate of the calcium chloride solution is 2-5 mL / min, for example, it can be 2.0 mL / min, 2.5 mL / min, 3.0 mL / min, 3.5 mL / min, 4.0 mL / min, 4.5 mL / min or 5.0 mL / min, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0094] In some alternative examples, the volume ratio of the calcium chloride solution to the precursor solution is (1-3):10, for example, it can be 1:10, 1.2:10, 1.4:10, 1.6:10, 1.8:10, 2.0:10, 2.2:10, 2.4:10, 2.6:10, 2.8:10 or 3.0:10, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0095] In some alternative examples, after all the calcium chloride solution is dropped, the mixture formed by the calcium chloride solution and the precursor solution is mixed and stirred for 20-30 min, for example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0096] In some alternative examples, the standing and curing time is 12 to 24 h, for example, it can be 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h or 24 h, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0097] In some alternative examples, the temperature of freeze-drying is -50 to -40 °C, for example, it can be -50 °C, -49 °C, -48 °C, -47 °C, -46 °C, -45 °C, -44 °C, -43 °C, -42 °C, -41 °C or -40 °C, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0098] In some alternative examples, the time of freeze-drying is 24 to 48 h, for example, it can be 24 h, 26 h, 28 h, 30 h, 32 h, 34 h, 36 h, 38 h, 40 h, 42 h, 44 h, 46 h or 48 h, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0099] In some alternative examples, the mesh number of the sieve for crushing and sieving is 80 to 100 meshes, for example, it can be 80 meshes, 82 meshes, 84 meshes, 86 meshes, 88 meshes, 90 meshes, 92 meshes, 94 meshes, 96 meshes, 98 meshes or 100 meshes, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0100] In a second aspect, the present invention provides a soil improvement method using the soil conditioner for saline-alkali land described in the first aspect. The soil improvement method includes:

[0101] Determine the application rate of the soil conditioner according to the pH value of the saline-alkali land soil, and divide the soil conditioner to be applied into two parts by weight; First, spread the first part of the soil conditioner on the surface of the saline-alkali land, and mix the first part of the soil conditioner with the shallow-layer saline-alkali land soil on the surface through rotary tillage; Subsequently, dig pits on the saline-alkali land, mix the second part of the soil conditioner with the excavated soil evenly and then backfill it into the pits; Finally, water the saline-alkali land.

[0102] As a preferred technical solution of the present invention, when the pH value of the saline-alkali land soil > 9, the dosage of the soil conditioner is 2 to 3 tons per mu, for example, it can be 2.0 tons per mu, 2.1 tons per mu, 2.2 tons per mu, 2.3 tons per mu, 2.4 tons per mu, 2.5 tons per mu, 2.6 tons per mu, 2.7 tons per mu, 2.8 tons per mu, 2.9 tons per mu or 3.0 tons per mu, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0103] In some alternative examples, when the pH value of the saline-alkali soil > 9, the weight ratio of the first soil conditioner to the second soil conditioner is (2.5 - 3.5):1. For example, it can be 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3.0:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1 or 3.5:1, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0104] In some alternative examples, when the pH value of the saline-alkali soil > 9, the first soil conditioner is mixed with the saline-alkali soil at a soil depth of 18 - 20 cm. For example, it can be 18 cm, 18.2 cm, 18.4 cm, 18.6 cm, 18.8 cm, 19 cm, 19.2 cm, 19.4 cm, 19.6 cm, 19.8 cm or 20 cm, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0105] In some alternative examples, when the pH value of the saline-alkali soil > 9, the depth of the pit dug on the saline-alkali land is 25 - 35 cm. For example, it can be 25 cm, 26 cm, 27 cm, 28 cm, 29 cm, 30 cm, 31 cm, 32 cm, 33 cm, 34 cm or 35 cm, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0106] As a preferred technical solution of the present invention, when the pH value of the saline-alkali soil is 8 - 9, the dosage of the soil conditioner is 1.2 - 1.5 tons per mu. For example, it can be 1.2 tons per mu, 1.25 tons per mu, 1.3 tons per mu, 1.35 tons per mu, 1.4 tons per mu, 1.45 tons per mu or 1.5 tons per mu, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0107] In some alternative examples, when the pH value of the saline-alkali soil is 8 - 9, the weight ratio of the first soil conditioner to the second soil conditioner is (1.5 - 2.5):1. For example, it can be 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1 or 2.5:1, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0108] In some alternative embodiments, when the pH value of the saline-alkali soil is 8 - 9, the first soil conditioner is mixed with the saline-alkali soil at a soil depth of 15 - 18 cm. For example, it can be 15 cm, 15.5 cm, 16 cm, 16.5 cm, 17 cm, 17.5 cm or 18 cm, but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0109] In some alternative embodiments, when the pH value of the saline-alkali soil is 8 - 9, the depth of the pit dug on the saline-alkali land is 20 - 25 cm. For example, it can be 20 cm, 20.5 cm, 21 cm, 21.5 cm, 22 cm, 22.5 cm, 23 cm, 23.5 cm, 24 cm, 24.5 cm or 25 cm, but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0110] As a preferred technical solution of the present invention, when the pH value of the saline-alkali soil is 7 - 8, the dosage of the soil conditioner is 0.5 - 0.8 tons per mu. For example, it can be 0.5 tons per mu, 0.55 tons per mu, 0.6 tons per mu, 0.65 tons per mu, 0.7 tons per mu, 0.75 tons per mu or 0.8 tons per mu, but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0111] In some alternative embodiments, when the pH value of the saline-alkali soil is 7 - 8, the weight ratio of the first soil conditioner to the second soil conditioner is (1 - 2):1. For example, it can be 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2.0:1, but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0112] In some alternative embodiments, when the pH value of the saline-alkali soil is 7 - 8, the first soil conditioner is mixed with the saline-alkali soil at a soil depth of 12 - 15 cm. For example, it can be 12 cm, 12.5 cm, 13 cm, 13.5 cm, 14 cm, 14.5 cm or 15 cm, but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0113] In some alternative embodiments, when the pH value of the saline-alkali soil is 7 - 8, the depth of the pit dug on the saline-alkali land is 15 - 20 cm. For example, it can be 15 cm, 15.5 cm, 16 cm, 16.5 cm, 17 cm, 17.5 cm, 18 cm, 18.5 cm, 19 cm, 19.5 cm or 20 cm, but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0114] The present invention implements a differential improvement strategy for saline-alkali lands with different pH values, and realizes the precise treatment of soil problems by applying soil conditioners in layers and dynamically adjusting the ratio, application depth and pit depth of the soil conditioners.

[0115] In severely saline-alkali lands (pH > 9), there are often dense salt crusts and strong alkaline barriers in the surface soil. At this time, by applying more and deeper soil conditioners and increasing the dosage of modified gel agents and compound biological agents, it is possible to penetrate the salt crust layer and build an ion barrier and a microbial active zone below the plow layer. The nano-pore structure of the high-dose modified gel agent can effectively adsorb sodium ions and slowly release water, while the combination of Bacillus and Trichoderma rapidly decomposes the surface organic matter through metabolic synergy to form a local slightly acidic environment, gradually breaking down the alkaline barrier. This deep intervention breaks the limitation of traditional improvement that only stays on the surface, extends the improvement effect downward by more than 30 cm, and fundamentally blocks the upward movement channel of salt.

[0116] For moderately and slightly saline-alkali lands (pH value = 7.5 - 8.5), although there is salt accumulation in the surface soil, the structure is still acceptable. The improvement strategy focuses on surface conditioning and nutrient balance. By applying less and shallower soil conditioners and reducing the dosage of modified gel agents, it is possible to avoid excessive change of soil air permeability. At the same time, the synergistic effect of vinegar residue and brown algae powder is used to adjust the local pH value of the soil, which not only maintains the phosphorus activation efficiency but also prevents the over-proliferation of antagonistic bacteria from inhibiting plant roots. This gradient application strategy makes the soil conditioner concentrated in the active root zone (0 - 20 cm), improves the nutrient utilization rate by 40%, and avoids the waste of resources caused by deep leakage.

[0117] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0118] The present invention provides a soil conditioner for improving saline-alkali lands and its supporting application method. Its core advantage lies in realizing the systematic repair of the physical properties, chemical properties and biological activities of saline-alkali soils through the synergistic action of multiple components and the optimization of structural design. This technology breaks through the single-function limitation of traditional improvement measures and effectively solves the long-existing technical problems such as salt return and rebound, low fertility, and microbial community imbalance in the treatment of saline-alkali lands by constructing a multi-level and multi-dimensional soil improvement system. Brief Description of the Drawings

[0119] Figure 1 It is the process flow chart of the preparation of the modified gel agent provided in Embodiments 1 - 13 of the present invention; Detailed Embodiments

[0120] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments described herein are specific specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are all explanatory and exemplary and should not be construed as limiting the embodiments of the present invention and the protection scope of the present invention. Except for the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include technical solutions that make any obvious substitutions and modifications to the embodiments described herein.

[0121] Example 1

[0122] This example provides a soil conditioner for saline-alkali land, which comprises the following components in parts by weight:

[0123]

[0124] Among them, based on 100 parts by weight of the composite biological agent, it comprises the following components in parts by weight:

[0125]

[0126] The composite biological agent is prepared by mixing and stirring the above components in proportion.

[0127] Among them, as Figure 1 shown, the modified gelling agent is prepared by the following method:

[0128] (Ⅰ)Disperse the nano-montmorillonite in anhydrous ethanol and perform ultrasonic dispersion for 50 min at an ultrasonic power of 200 W to obtain a montmorillonite suspension. The mass fraction of nano-montmorillonite in the montmorillonite suspension is 2 wt%. Add cetyltrimethylammonium bromide to the montmorillonite suspension. The mass ratio of nano-montmorillonite to cetyltrimethylammonium bromide is 1:1. Perform ultrasonic exfoliation for 3 h at an ultrasonic power of 500 W, and then centrifuge at a rotation speed of 8000 rpm for 25 min. Wash the precipitate obtained after centrifugation and dry it at 40 °C for 24 h to obtain intercalated montmorillonite;

[0129] (Ⅱ)Drop the acrylic acid monomer into a 1 wt% sodium hydroxide solution, mix evenly to obtain an acrylic acid monomer solution. The molar ratio of acrylic acid monomer to sodium hydroxide in the sodium hydroxide solution is 1:1. Dissolve sodium alginate in deionized water to obtain a 2 wt% sodium alginate solution. Add N,N'-methylenebisacrylamide to the sodium alginate solution. The mass ratio of sodium alginate to N,N'-methylenebisacrylamide is 100:1. After ultrasonic treatment, a mixed solution is obtained;

[0130] Under a nitrogen atmosphere, the acrylic monomer solution was dropped into the mixed solution at a dropping rate of 2 mL / min. The mass ratio of the acrylic monomer to N,N'-methylenebisacrylamide was 100:1. After all the dropping was completed, the mixture was stirred at 50 °C for 50 min to undergo a reaction. After the reaction ended, a reaction product solution was obtained. The intercalated montmorillonite was dispersed in the reaction product solution, and the ratio of the intercalated montmorillonite to the reaction product solution was 1 g:1 mL. After mixing evenly, a precursor solution was obtained.

[0131] (Ⅲ) Under the heating condition of 40 °C, a 2 wt% calcium chloride solution was dropped into the precursor solution obtained in step (Ⅱ) at a dropping rate of 2 mL / min. The volume ratio of the calcium chloride solution to the precursor solution was 1:10. After all the dropping was completed, the mixture was stirred for 20 min, and then left to stand and solidify for 12 h to obtain a composite gel. The composite gel was washed with deionized water, then freeze-dried at -50 °C for 24 h, pulverized, and passed through an 80-mesh sieve to obtain a modified gelling agent.

[0132] Among them, taking 100 parts by weight of the functional auxiliary agent as the basis, it includes the following components in parts by weight:

[0133]

[0134] The functional auxiliary agent was prepared by mixing and stirring the above components in proportion.

[0135] The modified bentonite was prepared by the following method:

[0136] First, the sodium-based bentonite (A00355, purchased from Wuhan Jiyesheng Chemical Co., Ltd.) was dispersed in ethanol (volume fraction 95%) to prepare a bentonite suspension with a mass fraction of 10 wt%.

[0137] Secondly, cetyltrimethylammonium bromide was added to the bentonite suspension. The addition amount of cetyltrimethylammonium bromide was 3 wt% of the mass of the bentonite, and it was ultrasonicated at 600 W for 10 min.

[0138] Finally, the mixture was stirred and reacted for 5 h, centrifuged and separated, washed with ethanol 3 times, and dried to a constant weight.

[0139] This example also provides a method for soil improvement of saline-alkali soil using the above soil improver, which specifically includes the following steps:

[0140] The pH value of the saline-alkali soil was detected, and it was found that the soil pH value was 9.2. The dosage of the soil conditioner was determined to be 2 tons per mu. The soil conditioner to be broadcast was divided into two parts by weight. The weight ratio of the first soil conditioner to the second soil conditioner was 3:1. First, the first soil conditioner was broadcast on the surface of the saline-alkali soil, and the first soil conditioner was mixed with the saline-alkali soil with a depth of 18 cm through rotary tillage. Subsequently, pits were dug on the saline-alkali soil with a depth of 30 cm. The second soil conditioner was mixed evenly with the excavated soil and then backfilled into the pits. Finally, the saline-alkali soil was watered, and the watering amount was 3 kg / m 2 .

[0141] The source information of the raw materials used in the following examples and comparative examples is the same as that of Example 1.

[0142] Example 2

[0143] This example provides a soil conditioner for saline-alkali soil, which comprises the following components in parts by weight:

[0144]

[0145] Among them, taking the weight of the composite biological agent as 100 parts, it comprises the following components in parts by weight:

[0146]

[0147] The composite biological agent is prepared by mixing and stirring the above components in proportion.

[0148] Among them, as Figure 1 shown, the modified gelling agent is prepared by the following method:

[0149] (Ⅰ)Disperse the nano-montmorillonite in anhydrous ethanol, carry out ultrasonic dispersion for 48 min under an ultrasonic power of 220 W to obtain a montmorillonite suspension, and the mass fraction of nano-montmorillonite in the montmorillonite suspension is 2.5 wt%. Add cetyltrimethylammonium bromide to the montmorillonite suspension, and the mass ratio of nano-montmorillonite to cetyltrimethylammonium bromide is 1.2:1. Carry out ultrasonic exfoliation for 2.8 h under an ultrasonic power of 520 W, and then centrifuge at a rotation speed of 8500 rpm for 22 min. Wash the precipitate obtained after centrifugation, and dry it at 42 °C for 21 h to obtain intercalated montmorillonite;

[0150] (II) The acrylic acid monomer is dropped into a 1.5 wt% sodium hydroxide solution. After mixing evenly, an acrylic acid monomer solution is obtained. The molar ratio of the acrylic acid monomer to sodium hydroxide in the sodium hydroxide solution is 1:1. Sodium alginate is dissolved in deionized water to obtain a 2.5 wt% sodium alginate solution. N,N'-methylenebisacrylamide is added to the sodium alginate solution. The mass ratio of sodium alginate to N,N'-methylenebisacrylamide is 100:1.2. After ultrasonic treatment, a mixed solution is obtained.

[0151] Under a nitrogen atmosphere, the acrylic acid monomer solution is dropped into the mixed solution at a dropping rate of 3 mL / min. The mass ratio of the acrylic acid monomer to N,N'-methylenebisacrylamide is 100:1.2. After all the drops are added, the mixture is stirred at 52 °C for 48 min to undergo a reaction. After the reaction ends, a reaction product solution is obtained. Intercalated montmorillonite is dispersed in the reaction product solution. The ratio of intercalated montmorillonite to the reaction product solution is 1.2 g:1 mL. After mixing evenly, a precursor solution is obtained.

[0152] (III) Under a heating condition of 42 °C, a 3 wt% calcium chloride solution is dropped into the precursor solution obtained in step (II) at a dropping rate of 3 mL / min. The volume ratio of the calcium chloride solution to the precursor solution is 1.5:10. After all the drops are added, the mixture is stirred for 22 min, and then left to stand and solidify for 15 h to obtain a composite gel. The composite gel is washed with deionized water, then freeze-dried at -48 °C for 30 h, crushed, and passed through an 85-mesh sieve to obtain a modified gelling agent.

[0153] Among them, based on 100 parts by weight of the functional auxiliary agent, it includes the following components in parts by weight:

[0154]

[0155]

[0156] The functional auxiliary agent is prepared by mixing and stirring the above components in proportion.

[0157] The modified bentonite is prepared by the following method:

[0158] First, sodium-based bentonite is dispersed in ethanol (volume fraction 95%) to prepare a 10 wt% bentonite suspension.

[0159] Secondly, cetyltrimethylammonium bromide is added to the bentonite suspension. The addition amount of cetyltrimethylammonium bromide is 3 wt% of the mass of bentonite. Ultrasonic treatment is carried out at 600 W for 10 min.

[0160] Finally, the mixture is stirred and reacted for 5 h, centrifuged and separated, washed with ethanol 3 times, and dried to a constant weight.

[0161] This embodiment also provides a method for soil improvement of saline-alkali soil with the above soil conditioner, which specifically includes the following steps:

[0162] Detect the pH value of the saline-alkali soil, and it is found that the soil pH value is 10.1. Determine the dosage of the soil conditioner to be 3 tons per mu. Divide the soil conditioner to be spread by weight into two parts, and the weight ratio of the first part of the soil conditioner to the second part of the soil conditioner is 3.5:1. First, spread the first part of the soil conditioner on the surface of the saline-alkali land, and mix the first part of the soil conditioner with the saline-alkali soil with a depth of 20 cm through rotary tillage; subsequently, dig pits on the saline-alkali land with a depth of 35 cm, mix the second part of the soil conditioner with the dug-out soil evenly and then backfill it into the pits; finally, water the saline-alkali land, and the watering amount is 3 kg / m 2 .

[0163] Example 3

[0164] This embodiment provides a soil conditioner for saline-alkali soil, which includes the following components in parts by weight:

[0165]

[0166] Among them, taking the weight of the composite biological agent as 100 parts, it includes the following components in parts by weight:

[0167]

[0168] The composite biological agent is prepared by mixing and stirring the above components in proportion.

[0169] Among them, as Figure 1 shown, the modified gelling agent is prepared by the following method:

[0170] (Ⅰ) Disperse the nano-montmorillonite in anhydrous ethanol, carry out ultrasonic dispersion for 45 min under an ultrasonic power of 250 W to obtain a montmorillonite suspension, and the mass fraction of nano-montmorillonite in the montmorillonite suspension is 3 wt%; add cetyltrimethylammonium bromide to the montmorillonite suspension, and the mass ratio of nano-montmorillonite to cetyltrimethylammonium bromide is 1.3:1. Carry out ultrasonic exfoliation for 2.5 h under an ultrasonic power of 550 W, then centrifuge at a rotation speed of 9000 rpm for 20 min, wash the precipitate obtained after centrifugation, and dry it at 45 °C for 18 h to obtain the intercalated montmorillonite;

[0171] (II) Drop acrylic monomers into a 2 wt% sodium hydroxide solution. After mixing evenly, an acrylic monomer solution is obtained. The molar ratio of acrylic monomers to sodium hydroxide in the sodium hydroxide solution is 1:1. Dissolve sodium alginate in deionized water to obtain a 3 wt% sodium alginate solution. Add N,N'-methylenebisacrylamide to the sodium alginate solution. The mass ratio of sodium alginate to N,N'-methylenebisacrylamide is 100:1.5. After ultrasonic treatment, a mixed solution is obtained.

[0172] Under a nitrogen atmosphere, drop the acrylic monomer solution into the mixed solution at a dropping rate of 3 mL / min. The mass ratio of acrylic monomers to N,N'-methylenebisacrylamide is 100:1.5. After all are dropped, mix and stir at 55 °C for 45 min to undergo a reaction. After the reaction ends, a reaction product solution is obtained. Disperse the intercalated montmorillonite in the reaction product solution. The ratio of intercalated montmorillonite to the reaction product solution is 1.5 g:1 mL. After mixing evenly, a precursor solution is obtained.

[0173] (III) Under heating conditions of 45 °C, drop a 3 wt% calcium chloride solution into the precursor solution obtained in step (II) at a dropping rate of 3 mL / min. The volume ratio of the calcium chloride solution to the precursor solution is 2:10. After all are dropped, mix and stir for 25 min, and then stand for curing for 18 h to obtain a composite gel. Wash the composite gel with deionized water, then freeze-dry at -45 °C for 36 h, pulverize, and pass through a 90-mesh sieve to obtain a modified gelling agent.

[0174] Among them, based on 100 parts by weight of the functional auxiliary agent, it includes the following components in parts by weight:

[0175]

[0176] The functional auxiliary agent is prepared by mixing and stirring the above components in proportion.

[0177] The modified bentonite is prepared by the following method:

[0178] First, disperse sodium-based bentonite in ethanol (volume fraction 95%) to prepare a 10 wt% bentonite suspension.

[0179] Second, add cetyltrimethylammonium bromide to the bentonite suspension. The addition amount of cetyltrimethylammonium bromide is 3 wt% of the mass of bentonite. Perform ultrasonic treatment at 600 W for 10 min.

[0180] Finally, stir and react for 5 h, perform centrifugal separation, wash with ethanol 3 times, and dry to constant weight.

[0181] This embodiment also provides a method for soil improvement of saline-alkali soil with the above soil conditioner, which specifically includes the following steps:

[0182] Detect the pH value of the saline-alkali soil, and find that the soil pH value is 8.5. Determine the dosage of the soil conditioner to be 1.3 tons per mu. Divide the soil conditioner to be spread by weight into two parts, and the weight ratio of the first part of the soil conditioner to the second part of the soil conditioner is 2:1. First, spread the first part of the soil conditioner on the surface of the saline-alkali soil, and mix the first part of the soil conditioner with the saline-alkali soil with a soil depth of 16 cm through rotary tillage; Subsequently, dig pits on the saline-alkali land, with the pit depth of 20 cm. Mix the second part of the soil conditioner with the excavated soil evenly and then backfill it into the pits; Finally, water the saline-alkali soil, and the watering amount is 3 kg / m 2 .

[0183] Example 4

[0184] This embodiment provides a soil conditioner for saline-alkali soil, which includes the following components in parts by weight:

[0185]

[0186] Among them, taking the weight of the composite biological agent as 100 parts, it includes the following components in parts by weight:

[0187]

[0188] The composite biological agent is prepared by mixing and stirring the above components in proportion.

[0189] Among them, as Figure 1 shown, the modified gel agent is prepared by the following method:

[0190] (Ⅰ) Disperse the nano-montmorillonite in anhydrous ethanol, perform ultrasonic dispersion for 42 min at an ultrasonic power of 280 W to obtain a montmorillonite suspension, and the mass fraction of nano-montmorillonite in the montmorillonite suspension is 3.5 wt%; Add cetyltrimethylammonium bromide to the montmorillonite suspension, and the mass ratio of nano-montmorillonite to cetyltrimethylammonium bromide is 1.4:1. Perform ultrasonic exfoliation for 2.2 h at an ultrasonic power of 580 W, then centrifuge at a rotation speed of 9500 rpm for 18 min, wash the precipitate obtained after centrifugation, and dry it at 48 °C for 15 h to obtain intercalated montmorillonite;

[0191] (II) The acrylic acid monomer is dropped into a 2.5 wt% sodium hydroxide solution, and after mixing evenly, an acrylic acid monomer solution is obtained. The molar ratio of the acrylic acid monomer to sodium hydroxide in the sodium hydroxide solution is 1:1. Sodium alginate is dissolved in deionized water to obtain a 3.5 wt% sodium alginate solution. N,N'-methylenebisacrylamide is added to the sodium alginate solution, and the mass ratio of sodium alginate to N,N'-methylenebisacrylamide is 100:1.8. After ultrasonic treatment, a mixed solution is obtained.

[0192] Under a nitrogen atmosphere, the acrylic acid monomer solution is dropped into the mixed solution at a dropping rate of 4 mL / min. The mass ratio of the acrylic acid monomer to N,N'-methylenebisacrylamide is 100:1.8. After all the drops are added, the mixture is stirred at 58 °C for 42 min to undergo a reaction. After the reaction ends, a reaction product solution is obtained. Intercalated montmorillonite is dispersed in the reaction product solution, and the ratio of intercalated montmorillonite to the reaction product solution is 1.8 g:1 mL. After mixing evenly, a precursor solution is obtained.

[0193] (III) Under heating conditions of 48 °C, a 4 wt% calcium chloride solution is dropped into the precursor solution obtained in step (II) at a dropping rate of 4 mL / min. The volume ratio of the calcium chloride solution to the precursor solution is 2.5:10. After all the drops are added, the mixture is stirred for 28 min, and then left to stand and solidify for 21 h to obtain a composite gel. The composite gel is washed with deionized water, then freeze-dried at -43 °C for 42 h, pulverized, and passed through a 95-mesh sieve to obtain a modified gelling agent.

[0194] Among them, based on 100 parts by weight of the functional auxiliary agent, it includes the following components in parts by weight:

[0195]

[0196] The functional auxiliary agent is prepared by mixing and stirring the above components in proportion.

[0197] The modified bentonite is prepared by the following method:

[0198] First, sodium-based bentonite is dispersed in ethanol (volume fraction 95%) to prepare a 10 wt% bentonite suspension.

[0199] Secondly, cetyltrimethylammonium bromide is added to the bentonite suspension. The addition amount of cetyltrimethylammonium bromide is 3 wt% of the mass of bentonite, and ultrasonic treatment is carried out at 600 W for 10 min.

[0200] Finally, the mixture is stirred and reacted for 5 h, centrifuged and separated, washed with ethanol 3 times, and dried to constant weight.

[0201] This embodiment also provides a method for soil improvement of saline-alkali soil using the above soil conditioner, which specifically includes the following steps:

[0202] Detect the pH value of the saline-alkali soil and find that the soil pH value is 8.8. Determine the dosage of the soil conditioner to be 1.5 tons per mu. Divide the soil conditioner to be spread by weight into two parts, and the weight ratio of the first part of the soil conditioner to the second part of the soil conditioner is 2.5:1. First, spread the first part of the soil conditioner on the surface of the saline-alkali soil, and mix the first part of the soil conditioner with the saline-alkali soil with a soil depth of 18 cm through rotary tillage. Subsequently, dig pits on the saline-alkali land with a depth of 25 cm, mix the second part of the soil conditioner with the excavated soil evenly, and then backfill it into the pits. Finally, water the saline-alkali land, and the watering amount is 3 kg / m 2 .

[0203] Example 5

[0204] This embodiment provides a soil conditioner for saline-alkali soil, which includes the following components in parts by weight:

[0205]

[0206] Among them, taking the weight of the composite biological agent as 100 parts, it includes the following components in parts by weight:

[0207]

[0208]

[0209] The composite biological agent is prepared by mixing and stirring the above components in proportion.

[0210] Among them, as Figure 1 shown, the modified gel agent is prepared by the following method:

[0211] (Ⅰ) Disperse the nano-montmorillonite in anhydrous ethanol, carry out ultrasonic dispersion for 40 min at an ultrasonic power of 300 W to obtain a montmorillonite suspension, and the mass fraction of nano-montmorillonite in the montmorillonite suspension is 4 wt%. Add cetyltrimethylammonium bromide to the montmorillonite suspension, and the mass ratio of nano-montmorillonite to cetyltrimethylammonium bromide is 1.5:1. Carry out ultrasonic exfoliation for 2 h at an ultrasonic power of 600 W, then carry out centrifugation at a rotation speed of 10,000 rpm for 15 min, wash the precipitate obtained after centrifugation, and dry it at 50 °C for 12 h to obtain intercalated montmorillonite;

[0212] (II) Drop acrylic monomers into a 3 wt% sodium hydroxide solution. After mixing evenly, an acrylic monomer solution is obtained, and the molar ratio of acrylic monomers to sodium hydroxide in the sodium hydroxide solution is 1:1. Dissolve sodium alginate in deionized water to obtain a 4 wt% sodium alginate solution. Add N,N'-methylenebisacrylamide to the sodium alginate solution, and the mass ratio of sodium alginate to N,N'-methylenebisacrylamide is 100:2. After ultrasonic treatment, a mixed solution is obtained.

[0213] Under a nitrogen atmosphere, drop the acrylic monomer solution into the mixed solution at a dropping rate of 5 mL / min. The mass ratio of acrylic monomers to N,N'-methylenebisacrylamide is 100:2. After all are dropped, mix and stir at 60 °C for 40 min to carry out the reaction. After the reaction is completed, a reaction product solution is obtained. Disperse the intercalated montmorillonite in the reaction product solution, and the ratio of intercalated montmorillonite to the reaction product solution is 2 g:1 mL. After mixing evenly, a precursor solution is obtained.

[0214] (III) Under the heating condition of 50 °C, drop a 5 wt% calcium chloride solution into the precursor solution obtained in step (II) at a dropping rate of 5 mL / min. The volume ratio of the calcium chloride solution to the precursor solution is 3:10. After all are dropped, mix and stir for 30 min, and then let it stand and solidify for 24 h to obtain a composite gel. Wash the composite gel with deionized water, then freeze-dry at -40 °C for 48 h, crush it, and pass through a 100-mesh sieve to obtain a modified gelling agent.

[0215] Among them, taking 100 parts by weight of the functional auxiliary agent as the reference, it includes the following components in parts by weight:

[0216]

[0217] The functional auxiliary agent is prepared by mixing and stirring the above components in proportion.

[0218] The modified bentonite is prepared by the following method:

[0219] First, disperse sodium-based bentonite in ethanol (volume fraction 95%) to prepare a 10 wt% bentonite suspension.

[0220] Secondly, add cetyltrimethylammonium bromide to the bentonite suspension. The addition amount of cetyltrimethylammonium bromide is 3 wt% of the mass of bentonite, and carry out ultrasonic treatment at 600 W for 10 min.

[0221] Finally, stir and react for 5 h, carry out centrifugal separation, wash with ethanol 3 times, and dry to constant weight.

[0222] This embodiment also provides a method for soil improvement of saline-alkali soil with the above soil conditioner, which specifically includes the following steps:

[0223] Detect the pH value of the saline-alkali soil, and find that the soil pH value is 7.8. Determine the dosage of the soil conditioner to be 0.6 tons per mu. Divide the soil conditioner to be broadcast by weight into two parts. The weight ratio of the first part of the soil conditioner to the second part of the soil conditioner is 1.5:1. First, spread the first part of the soil conditioner on the surface of the saline-alkali soil, and mix the first part of the soil conditioner with the saline-alkali soil with a depth of 15 cm through rotary tillage; Subsequently, dig pits on the saline-alkali land, with a digging depth of 20 cm. Mix the second part of the soil conditioner with the dug-out soil evenly and then backfill it into the pits; Finally, water the saline-alkali soil, and the watering amount is 3 kg / m 2 .

[0224] Example 6

[0225] This embodiment provides a soil conditioner for saline-alkali soil. The difference from Example 1 is that the weight portion of Bacillus subtilis powder in the compound biological agent is adjusted to 20 parts, and the extra 5 parts are proportionally distributed to other components to ensure that the weight portion ratio between other components except Bacillus subtilis powder remains unchanged. Specifically, based on 100 parts by weight of the compound biological agent, the weight portions of the adjusted components are as follows:

[0226]

[0227] Other operation steps and process parameters are exactly the same as those in Example 1.

[0228] Example 7

[0229] This embodiment provides a soil conditioner for saline-alkali soil. The difference from Example 1 is that the weight portion of Bacillus subtilis powder in the compound biological agent is adjusted to 40 parts, and the insufficient 15 parts are proportionally deducted from other components to ensure that the weight portion ratio between other components except Bacillus subtilis powder remains unchanged. Specifically, based on 100 parts by weight of the compound biological agent, the weight portions of the adjusted components are as follows:

[0230]

[0231] Other operation steps and process parameters are exactly the same as those in Example 1.

[0232] Example 8

[0233] This embodiment provides a soil conditioner for saline-alkali land. The difference from Embodiment 1 is that the weight portion of Bacillus licheniformis powder in the compound biological agent is adjusted to 15 parts, and the extra 10 parts are proportionally distributed to other components to ensure that the weight portion ratio between other components except Bacillus licheniformis powder remains unchanged. Specifically, based on 100 parts by weight of the compound biological agent, the weight portions of the adjusted components are as follows:

[0234]

[0235] Other operation steps and process parameters are exactly the same as those in Embodiment 1.

[0236] Embodiment 9

[0237] This embodiment provides a soil conditioner for saline-alkali land. The difference from Embodiment 1 is that the weight portion of Bacillus licheniformis powder in the compound biological agent is adjusted to 30 parts, and the insufficient 5 parts are proportionally deducted from other components to ensure that the weight portion ratio between other components except Bacillus licheniformis powder remains unchanged. Specifically, based on 100 parts by weight of the compound biological agent, the weight portions of the adjusted components are as follows:

[0238]

[0239] Other operation steps and process parameters are exactly the same as those in Embodiment 1.

[0240] Embodiment 10

[0241] This embodiment provides a soil conditioner for saline-alkali land. The difference from Embodiment 1 is that the weight portion of modified bentonite in the functional auxiliary agent is adjusted to 25 parts, and the extra 5 parts are proportionally distributed to other components to ensure that the weight portion ratio between other components except modified bentonite remains unchanged. Specifically, based on 100 parts by weight of the functional auxiliary agent, the weight portions of the adjusted components are as follows:

[0242]

[0243] Other operation steps and process parameters are exactly the same as those in Embodiment 1.

[0244] Embodiment 11

[0245] This embodiment provides a soil conditioner for saline-alkali land. The difference from Embodiment 1 is that the weight portion of modified bentonite in the functional auxiliary agent is adjusted to 45 parts, and the insufficient 15 parts are proportionally deducted from other components to ensure that the weight portion ratio between other components except modified bentonite remains unchanged. Specifically, based on 100 parts by weight of the functional auxiliary agent, the weight portions of the adjusted components are as follows:

[0246]

[0247] The other operation steps and process parameters are exactly the same as those in Example 1.

[0248] Example 12

[0249] This example provides a soil conditioner for saline-alkali land. The difference from Example 1 is that the ratio of intercalated montmorillonite to the reaction product solution is adjusted to 0.5 g:1 mL, and the other operation steps and process parameters are exactly the same as those in Example 1.

[0250] Example 13

[0251] This example provides a soil conditioner for saline-alkali land. The difference from Example 1 is that the ratio of intercalated montmorillonite to the reaction product solution is adjusted to 2.5 g:1 mL, and the other operation steps and process parameters are exactly the same as those in Example 1.

[0252] The pH value and the number of colonies of the saline-alkali land before treatment in Examples 1 - 13 were tested. After treating the saline-alkali land soil with the soil conditioners provided in Examples 1 - 13, the pH value and the number of colonies of the treated saline-alkali land were tested again. The test steps are as follows:

[0253] (1) pH value test

[0254] Mix the soil sample with deionized water at a mass ratio of 1:2.5, stir for 30 minutes, and after standing for 30 minutes, measure the pH value of the suspension using a glass electrode pH meter.

[0255] (2) Colony number test

[0256] Dilute the soil sample to 10 -2 times, take 100 μL of the dilution and spread it on the selective medium for Bacillus. Culture it in a constant temperature incubator at 28 ± 2 °C for 72 hours, and count the number of colonies using the plate counting method.

[0257] The test results are shown in Table 1.

[0258] Table 1: Test results

[0259]

[0260]

[0261] It can be seen from the test data provided in Table 1 that Examples 1 - 5 demonstrate the comprehensive improvement effects of soil conditioners on saline-alkali land under different ratios. The results show that with the synergistic optimization of the composite biological agent and the functional auxiliary agent, the soil pH value gradually decreases and the number of microbial colonies increases significantly. This gradient optimization indicates the existence of a synergistic effect among the components in terms of physical structure reconstruction, chemical salt reduction, and biological activation.

[0262] From the test data of Example 1, Example 6 and Example 7, it can be seen that in Example 6, the addition amount of Bacillus subtilis powder is too small, the activity of alkaline phosphatase secreted by it decreases, resulting in a decrease in the activation efficiency of mineral phosphorus, and the soil pH value only drops from 9.2 to 8.5. At the same time, the decrease in the secretion amount of organic acids reduces the removal rate of exchangeable sodium ions. In Example 7, the addition amount of Bacillus subtilis powder is too large. Although the enzyme activity is briefly increased, due to carbon source competition, the balance of the bacterial community is disrupted, and the activity of antagonistic bacteria is inhibited. Eventually, the decrease amplitude of the pH value becomes smaller, indicating that there is an optimal action threshold for this strain.

[0263] From the test data of Example 1, Example 8 and Example 9, it can be seen that in Example 8, the addition amount of Bacillus licheniformis powder is too small, the concentration of iturin secreted by it is insufficient, resulting in a decrease in the survival rate of Bacillus spores in an environment with pH > 9, and the inhibition rate of antagonistic bacteria against pathogenic bacteria decreases, manifested as a slowdown in the increase amplitude of the colony number. In Example 9, the addition amount of Bacillus licheniformis powder is too large. The lipopeptide substances non-specifically bind to the extracellular polysaccharides secreted by Bacillus subtilis, inhibiting the exposure of the enzyme active center and reducing the phosphorus activation efficiency. Although the pH drops significantly in the short term, the long-term stability of the bacterial community is damaged.

[0264] From the test data of Example 1, Example 10 and Example 11, it can be seen that in Example 10, the addition amount of modified bentonite is too small, the layer spacing shrinks, resulting in a decrease in the density of Na+ adsorption sites, and the phenomenon of salt rebound is significant, and the degree of pH decrease is low; while in Example 11, the addition amount of modified bentonite is too large, and the bentonite particles agglomerate due to electrostatic repulsion, destroying the three-dimensional network structure of the gel, greatly reducing the saturated water absorption rate and the soil porosity, and instead exacerbating the waterlogging stress.

[0265] From the test data of Example 1, Example 10 and Example 11, it can be seen that in Example 12, the addition amount of intercalated montmorillonite is too small, the dispersion degree of the nanosheets is insufficient, resulting in an extension of the diffusion path of the intercalating agent molecules, a decrease in the ion exchange capacity of the modified gel, and an increase in the soil conductivity. In Example 13, the addition amount of intercalated montmorillonite is too large, and the lamellae stack to form a dense barrier, hindering the cross-linking reaction of sodium alginate, reducing the gel swelling rate, shortening the water release period under drought conditions, and weakening the long-term salt control ability.

[0266] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A soil conditioner for saline-alkali land, characterized in that, The soil conditioner includes vinegar residues, chitin, glucose, compound biological agent, modified gelling agent and functional auxiliary agent; The compound biological agent includes Bacillus subtilis powder, Bacillus licheniformis powder, Trichoderma spore powder, brown algae powder and light calcium carbonate; the functional auxiliary agent includes modified bentonite, polyglutamic acid, pregelatinized starch, biochar and potassium humate; the preparation of the modified gelling agent includes treating montmorillonite with quaternary ammonium salt to obtain intercalated montmorillonite, and then reacting acrylic acid, sodium alginate and N,N'-methylenebisacrylamide to obtain a reaction product solution; then dispersing the intercalated montmorillonite in the reaction product solution to obtain a precursor solution, and reacting with calcium chloride solution to obtain the modified gelling agent.

2. The soil conditioner for saline-alkali land according to claim 1, characterized in that, Based on 100 parts by weight of the soil conditioner, it includes the following components in parts by weight: Based on 100 parts by weight of the compound biological agent, it includes the following components in parts by weight: And / or, based on 100 parts by weight of the functional auxiliary agent, it includes the following components in parts by weight: And / or, the modified bentonite is sodium-based bentonite intercalated and modified with cetyltrimethylammonium bromide.

3. The soil conditioner for saline-alkali land according to claim 1, wherein The modified gelling agent is prepared by the following method: (Ⅰ) Disperse montmorillonite in ethanol and ultrasonically disperse it, add cetyltrimethylammonium bromide and ultrasonically exfoliate it, centrifuge, wash and dry the centrifuged precipitate to obtain intercalated montmorillonite; (Ⅱ) Mix acrylic acid with sodium hydroxide solution to obtain an acrylic acid monomer solution; mix sodium alginate with water to obtain a sodium alginate solution, and then add N,N'-methylenebisacrylamide and ultrasonically obtain a mixed solution; add the acrylic acid monomer solution to the mixed solution, mix and stir and heat to react to obtain a reaction product solution, and disperse the intercalated montmorillonite in the reaction product solution to obtain a precursor solution; (Ⅲ) Add calcium chloride solution to the precursor solution, stir evenly, stand and solidify to obtain a composite gel, wash, dry, pulverize and screen to obtain the modified gelling agent.

4. The soil conditioner for saline-alkali land according to claim 3, characterized in that In step (Ⅰ), the mass fraction of nano-montmorillonite in the montmorillonite suspension is 2-4wt%; The ultrasonic power of the ultrasonic dispersion is 200-300W; The ultrasonic time of the ultrasonic dispersion is 40-50min; The mass ratio of nano-montmorillonite to cetyltrimethylammonium bromide in the montmorillonite suspension is (1-1.5):1; The ultrasonic power of the ultrasonic exfoliation is 500-600W; The ultrasonic time of the ultrasonic exfoliation is 2-3h; The rotation speed of the centrifugation is 8000-10000rpm; The centrifugation time is 15-25min; The drying temperature is 40-50°C; The drying time is 12-24h.

5. The soil conditioner for saline-alkali land according to claim 3, characterized in that, In step (Ⅱ), the mass fraction of the sodium hydroxide solution is 1-3wt%; The molar ratio of the acrylic acid monomer to sodium hydroxide in the sodium hydroxide solution is 1:1; The mass fraction of sodium alginate in the sodium alginate solution is 2-4wt%; The mass ratio of sodium alginate to N,N'-methylenebisacrylamide in the sodium alginate solution is 100:(1-2); The mass ratio of the acrylic monomer in the acrylic monomer solution to N,N'-methylenebisacrylamide in the mixed solution is 100:(1-2); The dropping rate of the acrylic monomer solution is 2-5 mL / min; The mixing and stirring time of the acrylic monomer solution and the mixed solution is 40-50 min; The heating temperature during the mixing and stirring of the acrylic monomer solution and the mixed solution is 50-60 °C; The ratio of the intercalated montmorillonite to the reaction product solution is (1-2) g:1 mL.

6. The soil conditioner for saline-alkali land according to claim 3, wherein In step (Ⅲ), the mass fraction of calcium chloride in the calcium chloride solution is 2-5 wt%; The heating temperature during the dropping of the calcium chloride solution is 40-50 °C; The dropping rate of the calcium chloride solution is 2-5 mL / min; The volume ratio of the calcium chloride solution to the precursor solution is (1-3):10; After all the calcium chloride solution is dropped, the mixed solution formed by the calcium chloride solution and the precursor solution is mixed and stirred for 20-30 min; The standing and curing time is 12-24 h; The temperature of freeze-drying is -50 to -40 °C; The time of freeze-drying is 24-48 h; The mesh number of the sieve for crushing and sieving is 80-100 meshes.

7. A soil improvement method using the soil conditioner for saline-alkali land according to any one of claims 1 to 6, characterized in that, The soil improvement method includes: Determine the application rate of the soil conditioner according to the pH value of the saline-alkali soil, and divide the soil conditioner to be applied into two parts by weight; First, spread the first part of the soil conditioner on the surface of the saline-alkali soil, and mix the first part of the soil conditioner with the shallow-layer saline-alkali soil on the ground surface by rotary tillage; Subsequently, dig pits on the saline-alkali soil, mix the second part of the soil conditioner with the excavated soil evenly and then backfill it into the pits; Finally, water the saline-alkali soil.

8. The soil improvement method according to claim 7, characterized in that, When the pH value of the saline-alkali soil > 9, the dosage of the soil conditioner is 2-3 tons per mu; When the pH value of the saline-alkali soil > 9, the weight ratio of the first part of the soil conditioner to the second part of the soil conditioner is (2.5-3.5):1; When the pH value of the saline-alkali soil > 9, the first part of the soil conditioner is mixed with the saline-alkali soil with a soil depth of 18-20 cm; When the pH value of the saline-alkali soil > 9, the depth of the pits dug on the saline-alkali soil is 25-35 cm.

9. The soil improvement method according to claim 7, wherein When the pH value of the saline-alkali soil is 8-9, the dosage of the soil conditioner is 1.2-1.5 tons per mu; When the pH value of the saline-alkali soil is 8-9, the weight ratio of the first part of the soil conditioner to the second part of the soil conditioner is (1.5-2.5):1; When the pH value of the saline-alkali soil is 8-9, the first part of the soil conditioner is mixed with the saline-alkali soil with a soil depth of 15-18 cm; When the pH value of the saline-alkali soil is 8-9, the depth of the pits dug on the saline-alkali soil is 20-25 cm.

10. The soil improvement method according to claim 7, characterized in that, When the pH value of the saline-alkali soil is 7-8, the dosage of the soil conditioner is 0.5-0.8 tons per mu; When the pH value of the saline-alkali soil is 7-8, the weight ratio of the first part of the soil conditioner to the second part of the soil conditioner is (1-2):1; When the pH value of the saline-alkali soil is 7-8, the first part of the soil conditioner is mixed with the saline-alkali soil with a soil depth of 12-15 cm; When the pH value of the saline-alkali soil is 7 - 8, the depth of the pit dug on the saline-alkali land is 15 - 20 cm.

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