Soil improvement method based on soil improvement composition

Abstract

The invention relates to the related technical field of soil improvement, and discloses a soil improvement method based on a soil improvement composition, which comprises the following steps: step a, the soil improvement composition is applied according to a mass ratio of a surface layer to a deep layer of 2: 1 in a zoning manner, the depth of the surface layer is kept between 0 cm and 15 cm, and the depth of the deep layer is kept between 15 cm and 30 cm; b, covering the surface layer with a degradable starch film after the surface layer is applied, wherein the degradation period of the starch film is 20-30 days; c, after deep application, a 0.1-0.3% humic acid solution is injected to activate flora in the composition, the liquid injection amount is 5-10 L / m, the soil temperature is kept at 25-30 DEG C for 48 hours after liquid injection, the oxygen content of soil is kept at 5-8 mg / L during the period, phosphoric acid in the composition activates biochar to destroy capillary continuity, a hydrophobic barrier is formed after a starch film is degraded, and the biochar in the composition is degraded to form a hydrophobic barrier. A salt ascending channel is blocked, a compound flora activated by humic acid establishes quorum sensing in a micro-aerobic environment, and the flora secretes a polysaccharide cementitious body to drive organic matters to migrate upwards, so that the content of the organic matters in the soil is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field related to soil improvement, and more specifically, particularly relates to a soil improvement method based on a soil improvement composition. Background Art

[0002] Soil, as the basic carrier of agricultural production, its water and gas regulation ability directly determines the growth potential of crops. Under the current situation where arable land resources are tense and there is pressure on food security, soil compaction has become the key bottleneck restricting the sustainable development of agriculture. The micropores of compacted soil decrease, which will lead to unbalanced hydraulic conductivity, inhibited biological activity, poor water permeability, difficult infiltration of deep soil, reduced abundance of aerobic microorganisms, and decreased organic matter mineralization, resulting in insufficient soil fertility.

[0003] Therefore, in view of this, research and improvement are carried out on the existing structure and deficiencies, and a soil improvement method based on a soil improvement composition is provided, with the expectation of achieving a more practical value. Summary of the Invention

[0004] The present invention provides a soil improvement method based on a soil improvement composition to overcome the above-mentioned defects in the prior art.

[0005] The purpose and efficacy of a soil improvement method based on a soil improvement composition of the present invention are achieved by the following specific technical means: A soil improvement method based on a soil improvement composition includes the following steps: Step a, applying the soil improvement composition in zones according to a surface layer: deep layer mass ratio of 2:1, where the depth of the surface layer is maintained at 0 cm to 15 cm, and the depth of the deep layer is maintained at 15 cm to 30 cm; Step b, covering with a degradable starch film after surface application, and the degradation period of the starch film is 20 - 30 days; Step c, injecting a 0.1 - 0.3% humic acid solution after deep application to activate the bacteria in the composition, the injection volume is 5 to 10 L / m², and after injection, the soil temperature is maintained at 25 - 30 °C for 48 hours, and during this period, the soil oxygen content is maintained at 5 - 8 mg / L.

[0006] A further technical solution, the composition includes: 20 to 40 parts of phosphoric acid-activated biochar, 10 to 30 parts of modified calcium silicate minerals, and 5 to 15 parts of composite bacteria.

[0007] It should be noted that in saline-alkali soil, the naturally occurring micron-scale pores (diameter 0.1 - 10 μm) form a capillary network. When the soil moisture evaporates, these pores generate capillary force, continuously sucking the deep high-salt water to the surface layer, resulting in salt enrichment. A high proportion of the composition in the surface layer forms a composite barrier with the starch film, blocking the upward movement of salt. Its working mechanism is that the phosphoric acid-activated biochar forms a porous medium layer on the surface layer, with the pore size distribution mainly in the range of 50 - 200 μm, much larger than the capillary pore size, destroying the continuity of the original capillary. And the starch film directly blocks the evaporation flow as a physical barrier before degradation. The hydrophobic fragments - glycerol esterification products remaining after the degradation of the starch film adhere to the pore walls, reducing the surface energy, making it impossible for the capillary force to form a continuous liquid column, and physically interrupting the path of salt rising with water.

[0008] Applying humic acid solution deep into the soil to construct a micro-oxygen environment, activating the anaerobic respiration of the composite microbial community, and the microbial community extends to the surface layer to achieve two-way regulation of downward leaching of salt and upward migration of organic matter, breaking the limitation of the unidirectional infiltration of traditional soil amendments.

[0009] A further technical solution is that the modified calcium silicate mineral is prepared by calcining diatomite and phosphogypsum in a mass ratio of 3:1 to 5:1, and the calcination temperature is 650 °C to 750 °C, and the activation degree of SiO2 in the modified calcium silicate mineral ≥ 80%.

[0010] It should be noted that diatomite mainly contains amorphous SiO2, and the molecular formula of phosphogypsum is CaSO4·2H2O. Step-by-step reactions occur during the calcination process: (1) Dehydration stage (100 - 200 °C): CaSO4·2H2O → CaSO4 + 2H2O↑ (2) Solid-phase reaction (650 - 750 °C): SiO2 + CaSO4 → β-CaSiO3 + SO3↑ (main reaction) 3SiO2 + 2CaSO4 → Ca2Si3O8 + 2SO3↑ (side reaction) The product is mainly β-CaSiO3, containing a small amount of wollastonite variants.

[0011] A further technical solution is that the composite microbial community includes Trichoderma harzianum and Burkholderia, and the viable cell number ratio of Trichoderma harzianum to Burkholderia is 3:1 to 5:1, and the total viable cell number ≥ 1×10 9 CFU / g.

[0012] It should be noted that the Trichoderma harzianum and Burkholderia form a synergistic metabolic chain at a viable cell ratio of 3:1 to 5:1: The cellulase secreted by Trichoderma harzianum decomposes the residual starch film to produce oligosaccharides, which serve as the carbon source for Burkholderia, and the latter promotes the uptake of Fe by Trichoderma harzianum by synthesizing siderophores. 3+ When the total viable cell count ≥ 1 × 10 9 CFU / g, a quorum sensing threshold sufficient to resist the competition of indigenous microorganisms can be established within 48 hours. The ACC deaminase (1-aminocyclopropane-1-carboxylic acid deaminase) secreted by it increases the degradation efficiency of ethylene precursors by 2-3 times, significantly alleviating the plant growth inhibition caused by salt stress.

[0013] In a further technical solution, the phosphoric acid-activated biochar is prepared by impregnating corn straw with a 0.5 mol / L phosphoric acid solution and then carrying out oxygen-limited carbonization at 500°C to 600°C.

[0014] It should be noted that when corn straw is soaked in a 0.5 mol / L phosphoric acid solution, phosphoric acid molecules will penetrate into the gaps between cellulose microfibrils, react with hydroxyl groups to form phosphate esters, weaken the hydrogen bonds between polymer chains. During the carbonization stage at 500°C to 600°C, phosphoric acid catalyzes the dehydration and carbonization of cellulose, and volatile substances escape to form molecular-level micropores. The pyrolysis of lignin generates shrinkage stress, resulting in the collapse of the cell wall but retaining the original macroscopic structure of the vascular bundle, forming macropores. From the surface layer to the deep layer, the phosphoric acid concentration shows a gradient distribution, resulting in different degrees of pyrolysis in different regions, constructing a "micropore adsorption - macropore buffering" gradient pore structure. In the gradient pore structure, macropores serve as transport channels, and micropores serve as storage units, where micropores adsorb salt ions and macropores store the secretions of the microbial community.

[0015] In a further technical solution, the starch film contains 5% to 10% glycerol plasticizer, and the tensile strength ≥ 10 MPa.

[0016] It should be noted that 5-10% glycerol plasticizer enables the starch film to form an "island structure" with alternating β-crystalline and amorphous regions. During the degradation process, the α-1,4 glycosidic bonds of starch molecular chains are preferentially broken, and the remaining branched starch (containing glycerol-esterified hydroxyl groups) forms a hydrophobic film covering the soil particles.

[0017] In a further technical solution, the humic acid has a molecular weight of 1000-5000 Da and the chelated iron content ≤ 0.1%.

[0018] It should be noted that humic acid with a molecular weight of 1000 - 5000 Da contains an appropriate amount of phenolic hydroxyl groups and quinone groups, which promotes the extracellular electron transfer of the microbial community under microaerobic conditions and improves the nitrate reduction efficiency of Burkholderia. Chelated iron ≤ 0.1% can avoid competing with the microbial community for the iron carrier binding site and simultaneously inhibit the oxidative damage caused by the Fenton reaction.

[0019] In a further technical solution, after the starch film is covered in step b, it is activated by spraying with a water volume of 0.3 L / m² to 0.5 L / m², and 0.05 - 0.1 wt% of rhamnolipid is dissolved in the sprayed water.

[0020] It should be noted that 0.05 - 0.1 wt% of rhamnolipid, as a biosurfactant, can form a monolayer on the surface of the starch film after spraying, reduce the surface tension, promote the formation of hydrophilic channels in the film. At the same time, the rhamnose group of rhamnolipid forms a hydrogen bond with the hydroxyl group of the starch film, delaying the complete degradation time and achieving controlled release coverage.

[0021] In a further technical solution, the calcination process is carried out under nitrogen protection, and the heating rate is maintained at 5 °C / min to 10 °C / min.

[0022] It should be noted that a heating rate of 5 - 10 °C / min can ensure that phosphogypsum completes the stepwise dehydration of dihydrate → hemihydrate → anhydrous gypsum before 650 °C, avoiding lattice defects caused by rapid heating.

[0023] In a further technical solution, the calcined modified calcium silicate mineral is activated by treatment with a citric acid solution, and the concentration of the citric acid is 0.5 - 1.5 mol / L.

[0024] It should be noted that 0.5 - 1.5 mol / L of citric acid preferentially dissolves the free CaO in the modified calcium silicate mineral to form a calcium citrate coating layer, which can slowly release Ca in the soil 2+ to displace Na + , and at the same time, citric acid chelates Fe 3+ / Al 3+ on the surface of the mineral, exposing more silanol groups and enhancing the electrostatic adsorption of Na + .

[0025] Compared with the prior art, the present invention has the following beneficial effects: In a soil improvement method based on the soil improvement composition of the present invention, the composition is injected into the soil in layers. The phosphoric acid-activated biochar in the composition destroys the capillary continuity, and a hydrophobic barrier is formed after the starch film degrades, blocking the upward channel of salts. The composite microbial community activated by humic acid establishes quorum sensing under microaerobic conditions, the ACC deaminase activity is improved, and the promotion of Na +Leaching downward, the composite bacterial community secretes polysaccharide cementing substances to drive the upward migration of organic matter, and rhamnolipid reduces the surface tension of the solution to accelerate the downward infiltration of salts.

[0026] The modified calcium silicate mineral undergoes Ca 2+- Na + ion replacement, combined with citric acid activation treatment, to reduce the Na content in the soil layer. + The micropores formed by phosphoric acid-activated biochar adsorb salt ions, and the macropores of phosphoric acid-activated biochar transport the secretions of the bacterial community, forming a synergistic effect. 5 - 10% plasticizer glycerol is added to the starch film so that the residual hydrophobic segments after its degradation continuously inhibit capillary action. It is suitable for regulating saline-alkali land, is beneficial to increasing the content of organic matter in the soil, and the degradation products of the starch film pose no risk to the ecology. Brief Description of the Drawings

[0027] Figure 1 It is a test chart of the addition amount of the modified calcium silicate mineral in Examples 1 - 4 of the present invention on the soil salt content; Figure 2 It is a test chart of the addition amount of the modified calcium silicate mineral in Examples 1 - 4 of the present invention on the sodium ion content in the soil; Figure 3 It is a test chart of the addition amount of the composite bacteria in Examples 1 - 4 of the present invention on the ACC deaminase activity; Figure 4 It is a test chart of the addition amount of glycerol in Examples 1 - 4 of the present invention on the degradation rate of the starch film; Figure 5 It is a test chart of the humic acid solution concentration in Examples 1 - 4 of the present invention on the increment of soil organic matter. Detailed Embodiments

[0028] The following further describes in detail the embodiments of the present invention with reference to the drawings and examples. The following examples are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0029] Example 1: 1. Material preparation: Phosphoric acid-activated biochar: Corn straw is crushed to 2 - 5 mm, impregnated in 0.5 mol / L phosphoric acid solution (liquid-solid ratio 3:1) for 24 hours, drained, and then placed in a tube furnace. Under a nitrogen atmosphere, it is heated to 550 °C at a rate of 8 °C / min and carbonized for 2 h, and the pH of the product is 5.2.

[0030] Modified calcium silicate mineral: Diatomite (SiO2 92%) and phosphogypsum (CaSO4·2H2O ≥ 95%) are mixed in a mass ratio of 4:1, calcined at 700 °C at a rate of 8 °C / min for 2.5 h under nitrogen protection, and activated at room temperature for 1 h with 1 mol / L citric acid solution (liquid-solid ratio 5:1). The measured content of β-CaSiO3 is 78%, and the activation degree of SiO2 is 83%.

[0031] Composite microbial community: Trichoderma harzianum with the preservation number of CGMCC 5.1242, Latin scientific name Trichoderma harzianum, culture temperature 25°C; Burkholderia with the preservation number: CGMCC 1.10442, Latin scientific name: Burkholderia kururiensis, Chinese translation: Burkholderia kururiensis, culture temperature 37°C. Burkholderia is mixed in a ratio of 4:1, and the total viable count is 1.2×10 9 CFU / g (plate counting method).

[0032] 2. Implementation of soil improvement Basic parameters of saline-alkali soil: salt content 1.85% (measured by conductivity method), pH = 9.3, Na + content 1.2 g / kg.

[0033] Step a: The composition is mixed with 35 parts of phosphoric acid-activated biochar, 25 parts of modified calcium silicate minerals, and 12 parts of composite microbial community. 60 kg / mu is applied to the surface layer (10 - 15 cm), and 30 kg / mu is applied to the deep layer (25 - 30 cm) Step b: Cover with a starch film containing 8% glycerol and spray-treat with 0.4 L / m². The liquid contains 0.08% rhamnolipid.

[0034] Step c: Inject 8 L / m² of 0.2% humic acid solution. The molecular weight of humic acid is 2800 Da, and the proportion of chelated iron in the solution is 0.08%. Use an infrared thermometer to measure the soil temperature and keep the soil temperature covered with plastic film at 28 ± 1°C. Use a dissolved oxygen meter to detect the oxygen concentration and control the soil oxygen concentration to maintain at 6.5 ± 0.5 mg / L.

[0035] Index Improved group Blank control group Salt content in 0 - 15 cm soil 0.69% 1.72% Na⁺ content in 15 - 30 cm soil 0.8 g / kg 1.35 g / kg Degradation rate of starch film 82% - ACC deaminase activity 3.8 U / g 1.2 U / g Porosity change (%) +18.3 -2.1 Increment of organic matter (g / kg) 4.2 0.3 .

[0036] Example 2: 1. Material preparation: Phosphoric acid-activated biochar: Crush corn straw to 2 - 5 mm, immerse it in 0.4 mol / L phosphoric acid solution (liquid-solid ratio 4:1) for 24 hours, drain, and then place it in a tube furnace. Carbonize at 600°C for 1.5 h with a heating rate of 8°C / min under a nitrogen atmosphere. Modified calcium silicate minerals: Mix diatomite and phosphogypsum in a ratio of 3:1, calcine at 650°C for 3 h with a heating rate of 8°C / min under nitrogen protection, and activate at room temperature for 1 h with 1.5 mol / L citric acid solution (liquid-solid ratio 5:1). Composite microbial community: Mix Trichoderma harzianum (CGMCC 5.1242) and Burkholderia (CGMCC 1.10442) in a ratio of 3:1, and the total viable count is 5×10 8 CFU / g.

[0037] 2. Soil improvement implementation Step a: The composition is mixed with 30 parts of phosphoric acid-activated biochar, 20 parts of modified calcium silicate minerals, and 8 parts of composite microbial communities, and 60 kg / mu is applied to the surface layer (10 - 15 cm), and 30 kg / mu is applied to the deep layer (25 - 30 cm).

[0038] Step b: Cover with a starch film containing 5% glycerol, and spray-treat at 0.3 L / m². The liquid contains 0.05% rhamnolipid.

[0039] Step c: Inject 10 L / m² of 0.3% humic acid solution. The molecular weight of humic acid is 2800 Da, and the proportion of chelated iron in the solution is 0.08%. Use an infrared thermometer to measure the soil temperature, and maintain the soil temperature of the covered plastic film at 30 ± 1°C. Use a dissolved oxygen meter to detect the oxygen concentration, and control the soil oxygen concentration to be maintained at 5.0 ± 0.5 mg / L.

[0040] Detection index Improved group Blank control group Salt content in 0 - 15 cm soil 0.96 1.72% Na⁺ content in 15 - 30 cm 1.05 1.35 g / kg Degradation rate of starch film 78 - ACC deaminase activity 2.6 1.2 U / g Soil porosity change +15.2 -2.1% Increment of organic matter 3.5 0.3 g / kg 。

[0041] Example 3: 1. Material preparation Phosphoric acid-activated biochar: Corn straw is crushed to 2 - 5 mm, impregnated with 0.6 mol / L phosphoric acid solution (liquid-solid ratio 2:1) for 24 hours, drained, and then placed in a tube furnace. Under a nitrogen atmosphere, it is heated to 500°C at a rate of 8°C / min and carbonized for 3 h, and the product pH = 5.8.

[0042] Modified calcium silicate minerals: Diatomite (SiO2 92%) and phosphogypsum (CaSO4·2H2O ≥ 95%) are mixed in a mass ratio of 5:1, heated to 750°C at a rate of 8°C / min under nitrogen protection and calcined for 2 h, and activated at room temperature with 1.0 mol / L citric acid solution (liquid-solid ratio 5:1) for 1 h. The measured β-CaSiO3 content is 82%, and the SiO2 activation degree is 88%.

[0043] Composite microbial communities: Trichoderma harzianum (CGMCC 5.1242) and Burkholderia sp. (CGMCC 1.10442) are mixed in a ratio of 5:1, and the total viable count is 2×10 9 CFU / g (plate counting method).

[0044] 2. Soil improvement implementation Step a: The composition is mixed with 20 parts of phosphoric acid-activated biochar, 30 parts of modified calcium silicate minerals, and 15 parts of composite microbial communities, and 60 kg / mu is applied to the surface layer (10 - 15 cm), and 30 kg / mu is applied to the deep layer (25 - 30 cm).

[0045] Step b: Cover with a starch film containing 10% glycerol, and spray-treat at 0.5 L / m². The liquid contains 0.1% rhamnolipid.

[0046] Step c: Inject 5 L / m² of 0.1% humic acid solution into the 15 - 20 cm layer and 3 L / m² of 0.2% humic acid solution into the 20 - 30 cm layer. The molecular weight of the humic acid is 2800 Da, and the proportion of chelated iron is 0.08%. Use an infrared thermometer to measure the soil temperature and maintain it at 25 ± 1°C. Use a dissolved oxygen meter to control the oxygen concentration at 8.0 ± 0.5 mg / L.

[0047] Detection index Improved group Blank control group Salt content in 0 - 15 cm soil 0.58% 1.72% Na⁺ content in 15 - 30 cm 0.65 g / kg 1.35 g / kg Degradation rate of starch film 85% - ACC deaminase activity 3.7 U / g 1.2 U / g Soil porosity change +18.1% -2.1% Increment of organic matter 4.1 g / kg 0.3 g / kg 。

[0048] Example 4: 1. Material preparation: Phosphoric acid - activated biochar: The same as in Example 1 (0.5 mol / L phosphoric acid solution, carbonized at 550°C for 2 h).

[0049] Modified calcium silicate minerals: The same as in Example 2 (ratio of 3:1, calcined at 650°C for 3 h).

[0050] Composite microbial community: Trichoderma harzianum (CGMCC 5.1242) and Burkholderia sp. (CGMCC 1.10442) are mixed in a ratio of 4:1, and the total viable count is 1×10 9 CFU / g.

[0051] 2. Soil improvement implementation Step a: The composition is mixed with 40 parts of phosphoric acid - activated biochar, 15 parts of modified calcium silicate minerals, and 10 parts of composite microbial community. Apply 60 kg / mu to the surface layer (10 - 15 cm) and 30 kg / mu to the deep layer (25 - 30 cm).

[0052] Step b: Cover with a starch film containing 6% glycerol (add 1% cellulase to accelerate degradation), and spray - treat at 0.4 L / m². The liquid contains 0.08% rhamnolipid.

[0053] Step c: Inject 6 L / m² of 0.15% humic acid solution. The molecular weight of the humic acid is 2800 Da, and the proportion of chelated iron is 0.08%. Control the soil temperature at 25 ± 1°C and the oxygen concentration at 7.0 ± 0.5 mg / L.

[0054] Detection index Improved group Blank control group Salt content in 0 - 15 cm soil 0.75% 1.72% Na⁺ content in 15 - 30 cm 0.88 g / kg 1.35 g / kg Degradation rate of starch film 95% - ACC deaminase activity 3.1 U / g 1.2 U / g Soil porosity change +16.8% -2.1% Increment of organic matter 3.8 g / kg 0.3 g / kg 。

[0055] Detection index Example 1 Example 2 Example 3 Example 4 Blank control Salt content in 0 - 15 cm (%) 0.69 0.96 0.58 0.75 1.72 Na⁺ in 15 - 30 cm (g / kg) 0.80 1.05 0.65 0.88 1.35 Degradation rate of starch film (%) 82 78 85 95 - ACC deaminase (U / g) 3.8 2.6 3.7 3.1 1.2 Porosity change (%) +18.3 +15.2 +18.1 +16.8 -2.1 Increment of organic matter (g / kg) 4.2 3.5 4.1 3.8 0.3 。

[0056] Combined with the comparative data of Examples 1 - 4, and combined with Figures 1 - 5 , the saline - alkali soil improvement composition of the present invention shows a significant synergistic effect, and its mechanism of action can be summarized as follows: In Example 3, the desalination rate in the 0-15 cm layer is the highest. The proportion of modified calcium silicate minerals is 30 parts, the content of β-CaSiO3 is 82%, and the activation degree is 88%, which is significantly better than that in Example 2 with 20 parts of calcium silicate minerals. Regarding the relationship between the proportion of modified calcium silicate minerals and the desalination effect of the soil, as Figure 1 shown, generally, the proportion of modified calcium silicate minerals shows a negative correlation with the soil salt content, proving that an increase in the proportion of modified calcium silicate minerals can effectively improve the desalination effect.

[0057] In the 15-30 cm soil layer, the change in Na + content is as Figure 2 shown. The Na + content in Example 3 (0.65 g / kg) is reduced by 51.9% compared with the blank group, while in Example 4 (0.88 g / kg), the rapid degradation (95%) of the starch film leads to the short-term release of Na + . Generally speaking, calcium silicate minerals show a good adsorption effect. When the addition amount is 30 parts, the Na + content is the lowest (0.65 g / kg), showing a dose-dependent relationship. Its mechanism of action is that ion exchange dominated by calcium silicate minerals. β-CaSiO3 generates soluble Na2SiO3 through Ca 2+ -Na + exchange, and gradient injection of liquid promotes deep leaching. Rhamnolipid reduces the surface tension of the solution and enhances the migration efficiency of Na + .

[0058] As Figure 3 shown, in Example 1, due to the 4:1 flora ratio and the total bacteria amount of 1.2×10 9 CFU / g, and the ACC deaminase of 3.8 U / g, the activity is the highest; in Example 2, due to a 58% reduction in the bacteria amount, the enzyme activity decreases significantly. The core role of Burkholderia: the ACC deaminase secreted by it decomposes the ethylene precursor (ACC) to relieve salt stress. The requirement for flora balance: in Example 3, the flora ratio is 5:1, and the high bacteria amount of 2×10 9 CFU / g compensates for the competition of Trichoderma (the activity still reaches 3.7 U / g), proving that the total bacteria amount needs to be synergistically optimized with the ratio.

[0059] Regarding the soil porosity, Example 1 (+18.3%) and Example 3 (+18.1%) perform the best, depending on 35 parts of phosphoric acid-activated biochar activated at 550°C and 30 parts of highly active calcium silicate minerals respectively. Regarding the change in the increase of organic matter, as Figure 5As shown, Example 1 (4.2 g / kg) has the highest humic acid input of 8 L / m², while Example 4 (3.8 g / kg) has a 40% biochar ratio but a lower humic acid dosage (6 L / m²). Biochar and minerals form pores in coordination, and phosphoric acid activates biochar to form mesopores that complement the micron-scale pores of β-CaSiO3. 2800Da humic acid binds to the surface of biochar through carboxyl groups to form an organic-mineral complex.

[0060] About starch film degradation and salt dynamic balance Figure 4 As shown, in Example 4, the starch film degradation rate was 95%, and the degradation rate was the fastest due to the addition of 1% cellulase, but the short-term salt release resulted in a 0-15cm salt content of 0.75%, which was slightly higher than 0.69% in Example 1. In the natural degradation group, Examples 1-3, the degradation rate was 78-85%, which was positively correlated with the glycerol content.

[0061] For the remediation of heavily saline soil, preferred embodiment 3 is used to achieve deep desalination and synergistic optimization of pores; for the need for rapid remediation, preferred embodiment 4 is required to cooperate with leaching within 7 days after degradation; preferred embodiment 1 is used for the economical solution, which has the best overall cost performance, with a desalination rate of 60.5%, an organic matter increment of 4.2 g / kg, and a bacterial activity of 3.8 U / g.

[0062] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A soil improvement method based on a soil improvement composition, characterized in that, It includes the following steps: Step a: The soil improvement composition is applied in zones according to the surface layer: deep layer = 2:1 mass ratio, where the depth of the surface layer is maintained at 0 cm to 15 cm, and the depth of the deep layer is maintained at 15 cm to 30 cm; Step b: After the surface layer is applied, a degradable starch film is covered, and the degradation period of the starch film is 20 - 30 days; Step c: After the deep layer is applied, a 0.1 - 0.3% humic acid solution is injected to activate the bacterial community in the composition. The injection volume is 5 to 10 L / m². After injection, the soil temperature is maintained at 25 - 30 °C for 48 hours, and during this period, the soil oxygen content is maintained at 5 - 8 mg / L.

2. The soil improvement method based on a soil improvement composition according to claim 1, characterized in that, The composition includes: 20 to 40 parts of phosphoric acid-activated biochar, 10 to 30 parts of modified calcium silicate mineral, and 5 to 15 parts of composite bacterial community.

3. The soil improvement method based on a soil improvement composition according to claim 2, wherein The modified calcium silicate mineral is prepared by calcining diatomite and phosphogypsum according to a mass ratio of 3:1 to 5:

1. The calcination temperature is 650 °C to 750 °C, and the activation degree of SiO2 in the modified calcium silicate mineral is ≥ 80%.

4. A soil improvement method based on a soil improvement composition according to claim 2, characterized in that The composite bacterial community includes Trichoderma harzianum and Burkholderia, and the viable cell number ratio of Trichoderma harzianum to Burkholderia is 3:1 to 5:1, and the total viable cell number ≥ 1×10 9 CFU / g.

5. A soil improvement method based on the soil improvement composition according to claim 2, characterized in that, The phosphoric acid-activated biochar is prepared by impregnating corn straw with a 0.5 mol / L phosphoric acid solution and then performing oxygen-limited carbonization at 500 °C to 600 °C.

6. A soil improvement method based on a soil improvement composition according to claim 1, characterized in that, The starch film contains 5% to 10% glycerol plasticizer.

7. A soil improvement method based on a soil improvement composition according to claim 1, characterized in that, The humic acid has a molecular weight of 1000 - 5000 Da and the chelated iron content is ≤ 0.1%.

8. A soil improvement method based on a soil improvement composition according to claim 1, characterized in that, After the starch film is covered in step b, it is activated by spraying with 0.3 L / m² to 0.5 L / m² of water, and 0.05 - 0.1 wt% of rhamnolipid is dissolved in the spraying water.

9. A soil improvement method based on the soil improvement composition according to claim 3, characterized in that, The calcination process is carried out under nitrogen protection, and the heating rate is maintained at 5 °C / min to 10 °C / min.

10. A soil improvement method based on a soil improvement composition according to claim 3, characterized in that, The calcined modified calcium silicate mineral is activated by treatment with a citric acid solution, and the concentration of the citric acid is 0.5 - 1.5 mol / L.

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