A method for repairing saline-alkali soil based on microalgae biofertilizer

Abstract

The present invention relates to the technical field of soil remediation, and in particular to a method for remediating saline-alkali soil based on microalgae biofertilizer, comprising the following steps: S1, mixing a microalgae composite liquid, a Rhus chinensis extract, and livestock manure to obtain a fermentation product, adding a composite bacterial agent to the fermentation product and mixing and composting to obtain a microalgae biofertilizer; S2, dividing the saline-alkali soil into a first soil, a second soil, and a third soil according to particle size; S2-1, remediating the first soil; S2-2, remediating the second soil; S2-3, remediating the third soil, and completing the remediation; the present invention divides the saline-alkali soil into the first soil, the second soil, and the third soil according to particle size, reorganizes the soil structure after graded remediation, forms a composite matrix, blocks the capillary salt return path, uses the Rhus chinensis extract as a component of the microalgae biofertilizer, and can neutralize the OH group of the saline-alkali soil. ‑ , which reduces the pH of the surface soil and enhances the effect of saline-alkali land restoration.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a method for remediating saline-alkali soil based on microalgae biofertilizer. Background Art

[0002] Saline-alkali land is a type of salt accumulation, which means that the salt contained in the soil affects the normal growth of crops. Although large amounts of chemical fertilizers have greatly increased crop yields, the early large-scale and single use of chemical fertilizers has caused a decline in soil fertility, aggravated soil salinization and expanded soil desertification.

[0003] Microalgae grow fast and can be cultivated on a large scale. Their biomass can be directly applied to the soil without polluting the surrounding environment, such as groundwater and soil. However, the types and quantities of nutrients contained in microalgae themselves are relatively limited and may not be able to fully meet the various needs of plant growth and soil remediation.

[0004] Therefore, the present invention decides to design a method for repairing saline-alkali soil based on microalgae biofertilizer. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a method for repairing saline-alkali soil based on microalgae biofertilizer.

[0006] A method for repairing saline-alkali soil based on microalgae biofertilizer comprises the following steps:

[0007] S1, mixing the microalgae composite liquid, Rhus chinensis extract, and livestock manure in a mass ratio of 1:8 to 10:1.2 to obtain a fermentation product, adding 0.1 to 0.15% of the mass of the composite bacterial agent to the fermentation product, mixing and composting, ventilating for 15 to 20 minutes every hour at a ventilation rate of 3 to 5 L / min, and composting for 22 to 25 days to obtain a microalgae biofertilizer;

[0008] S2. Classifying the saline-alkali soil into a first soil having a particle size of less than 0.5 mm, a second soil having a particle size of 0.5 to 1 mm, and a third soil having a particle size of greater than 1 mm;

[0009] S2-1, adding 0.2-0.4% of the mass of microalgae biofertilizer to the first soil for repair, to obtain a first repaired soil;

[0010] S2-2, adding 2 to 5 times the mass of magnetized water to the second soil and mixing and pulse treating, drying for 6 to 8 days after the pulse treatment, and adding the first remediated soil and 0.5 to 0.8% of the mass of the second soil to the microalgae biofertilizer for remediation to obtain a second remediated soil;

[0011] S2-3. Plasma bombardment is performed on the third soil. After the bombardment is completed, the second remediation soil and microalgae biofertilizer accounting for 1 to 1.5% of the mass of the second soil are added for remediation. The remediation is completed.

[0012] Furthermore, the preparation method of the Rhus chinensis extract is:

[0013] Rhus chinensis is treated under steam at 1.5-2.5 MPa and 90-105° C. for 5-40 minutes and ground to obtain a powder. The powder is then mixed with deionized water at a solid-liquid ratio of 1 g:3-5 ml to obtain a suspension. The suspension is heated at 70-80° C. for 1.5-2 hours, then transferred to -70--50° C. and frozen for 10-12 hours. After freezing, the suspension is thawed at 30-35° C. for 2.5-3.5 hours. Finally, the suspension is dried at 50-55° C. for 2-3 hours and ground through a 100-200 mesh sieve to obtain a pretreated powder.

[0014] The method comprises adding a composite enzyme accounting for 0.4 to 0.8% by weight of the pretreated wood powder, performing enzymolysis at 25 to 35° C. for 4.5 to 6.5 hours to obtain an enzymolysis material, drying the enzymolysis material to a moisture content of less than 5%, continuously extracting the enzymolysis material with ethanol for 5 to 7 hours, concentrating the obtained extract until the volume no longer changes, and then drying the extract at 50 to 55° C. to a constant weight to obtain a Rhus chinensis extract.

[0015] Description: Steam explosion destroys the lignin-hemicellulose composite structure of Rhus chinensis, and combined with freeze-thaw to generate mechanical stress, which increases the porosity of the cell wall and the dissolution rate of flavonoids (quercetin, myricetin) and phenolic acid (gallic acid); adding complex enzymes converts polysaccharides into soluble oligosaccharides, which increases the carbon source available to microalgae. In addition, the quercetin in the extract forms complex micelles with the polysaccharides, which can remove excess reactive oxygen in saline-alkali soil and improve the survival rate of microalgae. The citric acid and tartaric acid in the extract, combined with the microporous structure generated by freeze-thaw, can neutralize the OH in saline-alkali soil. - , which lowers the pH of the surface soil.

[0016] Furthermore, the complex enzyme comprises cellulase, pectinase and chitosanase in a mass ratio of 1:0.8:0.4-0.6.

[0017] Description: Cellulase specifically cuts β-1,4-glycosidic bonds, degrading the cellulose microfibrils exposed after steam explosion into cellobiose and glucose, increasing the porosity of the cell wall and improving the subsequent flavonoid dissolution rate; pectinase cleaves galacturonan in the intercellular layer, releasing phenolic acids wrapped in pectin, while reducing the viscosity of the extract and accelerating mass transfer; chitosanase targets the decomposition of residual chitosan from possible fungal symbionts, increasing the carbon source of microalgae, and inducing the expression of plant stress resistance genes, enhancing plant salt tolerance.

[0018] Furthermore, the microalgae composite liquid comprises Chlorella vulgaris, Scenedesmus quadricauda and Scenedesmus obliquus in a mass ratio of 0.8:1:1.2-1.8.

[0019] Description: Chlorella can use organic carbon sources for growth and reproduction, and its growth and reproduction speed is fast, which helps to quickly improve the ecological environment of saline-alkali land; Scenedesmus obliquus has a certain adaptability to salinity and is suitable for the restoration of saline-alkali land; Scenedesmus quadricauda has strong environmental adaptability and fast growth rate, can grow in saline-alkali environment, and helps to improve the soil conditions of saline-alkali land.

[0020] Furthermore, the composite bacterial agent comprises a Bacillus subtilis solution, a nitrogen-fixing bacteria solution and a Microbacterium ginseng solution in a mass ratio of 3 to 4:2:1, wherein the content of live bacteria of Bacillus subtilis in the Bacillus subtilis solution, the content of live bacteria of nitrogen-fixing bacteria in the nitrogen-fixing bacteria solution and the content of live bacteria of Microbacterium ginseng in the Microbacterium ginseng solution are 8×10 6～7 CFU / ml.

[0021] Description: Bacillus subtilis has the strongest stress resistance, diverse functions, wide adaptability, and stable effects; nitrogen-fixing bacteria participate in the regulation of salt in the soil through biochemical processes, reducing the salinity of the soil; Microbacterium ginseng has the ability to promote plant growth under saline-alkali conditions.

[0022] Furthermore, the livestock manure includes any one of pig manure, cow manure, and chicken manure.

[0023] Description: Pig manure, cow manure and chicken manure are all high-quality organic fertilizers with rich nutrients and good fertilizer efficiency.

[0024] Furthermore, the magnetized water is prepared by treating tap water at a magnetic field strength of 0.3 to 0.4 T for 5.5 to 7.5 hours, and the DC voltage of the pulse treatment is 0.8 to 2.5 V, and the time is 10 to 20 minutes.

[0025] Note: The second soil is treated with magnetized water to reduce the diameter of water molecule clusters, increase the dissolved oxygen content, and promote the ion exchange efficiency with sodium ions. The cavitation effect produced by pulse treatment can destroy the soil colloid salt adsorption sites and shorten the desalination cycle.

[0026] Furthermore, the parameters of the plasma bombardment include: using oxygen plasma, radio frequency power of 220-280W, pressure of 55-65Pa, and bombardment time of 20-30min.

[0027] Description: Plasma bombardment creates nano-scale pores on the surface of the third soil, increasing the specific surface area and thus increasing the adsorption capacity of microalgae biofertilizer.

[0028] Furthermore, in S2-1 to S2-3, the method for repairing by adding microalgae biofertilizer is: stirring at a speed of 600 to 800 r / min for 25 to 35 minutes, standing for 50 to 80 minutes after the stirring, and then washing and filtering, and the repair is completed.

[0029] Note: High-speed stirring can greatly enhance the contact efficiency between microalgae biofertilizer and saline-alkali soil. During the static period, microalgae form a biofilm on the surface of soil particles, reducing hydraulic conductivity resistance and increasing the migration rate of salt ions.

[0030] Compared with the existing saline-alkali soil remediation methods, the present invention has the following beneficial effects:

[0031] (1) The present application divides saline-alkali soil into first soil, second soil and third soil according to particle size. The first soil has strong salt adsorption capacity and is directly repaired by microalgae biofertilizer. The sodium ion replacement ability of Rhus chinensis extract is combined with the adhesive effect of microalgae extracellular polysaccharides to reduce the soil sodium adsorption ratio; the second soil is treated with magnetized water pulses to accelerate the migration of salt ions, combined with drying to promote salt crystallization, and then microalgae fertilizer is added to form water-stable aggregates; the third soil is plasma bombarded to produce nano-scale pores, enhance the efficiency of microbial colonization, and increase the penetration depth of microalgae biofertilizer repair; after graded repair, the soil structure is reorganized to form a composite matrix to block the capillary salt return path.

[0032] (2) The present application adds Rhus chinensis extract to the microalgae biofertilizer. The Rhus chinensis extract destroys the lignin-hemicellulose composite structure of Rhus chinensis through steam explosion, and generates mechanical stress in combination with freeze-thaw, thereby increasing the porosity of the cell wall and the dissolution rate of flavonoids and phenolic acids. The addition of complex enzymes converts polysaccharides into soluble oligosaccharides, which increases the available carbon source of microalgae, thereby improving the repair activity of microalgae in saline-alkali soil. The quercetin in the extract forms complex micelles with the polysaccharide, which can remove excess active oxygen in saline-alkali soil and further improve the survival rate of microalgae. In addition, the citric acid and tartaric acid present in the Rhus chinensis extract, combined with the microporous structure generated by pretreatment, can neutralize the hydroxide ions in the saline-alkali soil and reduce the pH of the saline-alkali soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a comparison chart of the pH reduction rate results of the present invention's exploration 1;

[0034] Figure 2 This is a comparison chart of the total salt content reduction rate results of the present invention's exploration 1;

[0035] Figure 3 This is a comparison chart of the pH reduction rate results of the present invention's exploration 2;

[0036] Figure 4 This is a comparison chart of the total salt content reduction rate results of the present invention's exploration 2;

[0037] Figure 5 This is a comparison chart of the pH reduction rate results of the present invention's exploration 3;

[0038] Figure 6 This is a comparison chart of the total salt content reduction rate results of Investigation 3 of the present invention. DETAILED DESCRIPTION

[0039] In order to further illustrate the approach and effects achieved by the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with experiments.

[0040] Example 1: A method for repairing saline-alkali soil based on microalgae biofertilizer, comprising the following steps:

[0041] S1, mixing the microalgae complex liquid, Rhus chinensis extract, and livestock feces in a mass ratio of 1:9:1.2 to obtain a fermentation product,

[0042] The preparation method of the Rhus chinensis extract is:

[0043] Rhus chinensis was treated with steam at 2 MPa and 100°C for 25 minutes and ground through a 50-mesh sieve to obtain a powder. The powder was then mixed with deionized water at a solid-liquid ratio of 1 g:4 ml to obtain a suspension. The suspension was heated at 75°C for 1.8 hours, then transferred to -60°C and frozen for 11 hours. After freezing, it was thawed at 33°C for 3 hours, and finally dried at 53°C for 2.5 hours and ground through a 150-mesh sieve to obtain a pretreated powder.

[0044] Adding 0.6% of a complex enzyme by mass to the pretreated wood powder, wherein the complex enzyme includes cellulase, pectinase, and chitosanase in a mass ratio of 1:0.8:0.5, and the enzyme activity of the cellulase, pectinase, and chitosanase is 400 u / g; performing enzymolysis at 30° C. for 5.5 hours to obtain an enzymatic hydrolysis material, and drying the enzymatic hydrolysis material to a moisture content of 4%; then continuously extracting the enzymatic hydrolysis material with ethanol for 6 hours, concentrating the obtained extract until the volume no longer changes, and then drying the extract at 53° C. to a constant weight to obtain a Rhus chinensis extract;

[0045] The microalgae composite liquid comprises Chlorella vulgaris, Scenedesmus quadricauda and Scenedesmus obliquus in a mass ratio of 0.8:1:1.5;

[0046] A composite bacterial agent accounting for 0.13% of the mass of the fermented product was added to mix and compost, wherein the composite bacterial agent included a Bacillus subtilis solution, a nitrogen-fixing bacteria solution, and a Microbacterium ginseng solution in a mass ratio of 3.5:2:1, and the live bacteria content of Bacillus subtilis N24 in the Bacillus subtilis solution, the live bacteria content of nitrogen-fixing bacteria R31 in the nitrogen-fixing bacteria solution, and the live bacteria content of Microbacterium ginseng S4 in the Microbacterium ginseng solution were all 4×10 7CFU / ml, ventilation for 18 min every 1 h, ventilation rate of 4 L / min, composting for 23 days, and microalgae biofertilizer were obtained;

[0047] S2. Classifying the saline-alkali soil into a first soil having a particle size of less than 0.5 mm, a second soil having a particle size of 0.5 to 1 mm, and a third soil having a particle size of greater than 1 mm;

[0048] S2-1, adding 0.3% of the mass of microalgae biofertilizer to the first soil for remediation, to obtain a first remediated soil;

[0049] S2-2, adding 3.5 times the mass of magnetized water to the second soil and mixing and pulse treating, wherein the magnetized water is tap water treated at a magnetic field strength of 0.35 T for 6.5 hours, the DC voltage of the pulse treatment is 1.7 V, and the time is 15 minutes. After the pulse treatment, the soil is aired for 7 days. After the airing is completed, the first remediation soil and 0.65% of the mass of the second soil microalgae biofertilizer are added to the soil for remediation to obtain a second remediation soil;

[0050] S2-3. Plasma bombarding the third soil, wherein the parameters of the plasma bombardment include: using oxygen plasma, a radio frequency power of 240W, a pressure of 60Pa, and a bombardment time of 25 minutes; after the bombardment, the second remediation soil and a microalgae biofertilizer accounting for 1.2% of the mass of the second soil are added for remediation;

[0051] In S2-1 to S2-3, the method of adding microalgae biofertilizer for repair is: stirring at a speed of 700 r / min for 30 minutes, standing for 65 minutes after the stirring is completed, and then washing and filtering, and the repair is completed.

[0052] Example 2: This example differs from Example 1 in that the microalgae composite liquid, Rhus chinensis extract, and livestock manure are mixed in a mass ratio of 1:8:1.2 to obtain a fermentation product, and 0.1% of the mass of the composite bacterial agent is added to the fermentation product to mix and compost.

[0053] Example 3: This example differs from Example 1 in that the microalgae composite liquid, Rhus chinensis extract, and livestock manure are mixed in a mass ratio of 1:10:1.2 to obtain a fermentation product, and a composite bacterial agent accounting for 0.15% of the mass of the fermentation product is added to mix and compost.

[0054] Example 4: This example is different from Example 1 in that the microalgae composite liquid includes Chlorella vulgaris, Scenedesmus quadricauda, ​​and Scenedesmus obliquus in a mass ratio of 0.8:1:1.2.

[0055] Example 5: This example is different from Example 1 in that the microalgae composite liquid includes Chlorella vulgaris, Scenedesmus quadricauda and Scenedesmus obliquus in a mass ratio of 0.8:1:1.8.

[0056] Example 6: This example is different from Example 1 in that the composite bacterial agent includes Bacillus subtilis solution, nitrogen-fixing bacteria solution and Microbacterium ginseng solution in a mass ratio of 3:2:1, and the content of viable Bacillus subtilis in the Bacillus subtilis is 8×10 6 CFU / ml, the content of live bacteria of nitrogen-fixing bacteria in nitrogen-fixing bacteria solution and the content of live bacteria of Microbacterium ginseng in Microbacterium ginseng solution were both 8×10 7 CFU / ml.

[0057] Example 7: This example is different from Example 1 in that the composite bacterial agent includes a Bacillus subtilis solution, a nitrogen-fixing bacteria solution, and a Microbacterium ginseng solution in a mass ratio of 4:2:1, and the content of viable Bacillus subtilis in the Bacillus subtilis is 8×10 7 CFU / ml, the content of live bacteria of nitrogen-fixing bacteria in nitrogen-fixing bacteria solution and the content of live bacteria of Microbacterium ginseng in Microbacterium ginseng solution were both 8×10 6 CFU / ml.

[0058] Example 8: This example differs from Example 1 in that ventilation is performed for 15 minutes every hour, the ventilation rate is 3 L / min, and composting is performed for 22 days.

[0059] Example 9: This example differs from Example 1 in that ventilation is performed for 20 minutes every hour, the ventilation rate is 5 L / min, and composting is performed for 25 days.

[0060] Example 10: This example differs from Example 1 in that the Rhus chinensis is treated with steam at 1.5 MPa and 90° C. for 5 min.

[0061] Example 11: This example differs from Example 1 in that the Rhus chinensis is treated with steam at 2.5 MPa and 105° C. for 40 min.

[0062] Example 12: This example differs from Example 1 in that the powder is mixed with deionized water at a solid-liquid ratio of 1 g:5 ml to obtain a suspension, and the suspension is heated at 70°C for 1.5 h, then transferred to -50°C and frozen for 10 h. After freezing, it is thawed at 30°C for 2.5 h, and finally dried at 50°C for 2 h and ground through a 100-mesh sieve.

[0063] Example 13: This example differs from Example 1 in that the powder is mixed with deionized water at a solid-liquid ratio of 1 g:3 ml to obtain a suspension, and the suspension is heated at 80°C for 2 h, then transferred to -70°C and frozen for 12 h. After freezing, it is thawed at 35°C for 3.5 h, and finally dried at 55°C for 3 h and ground through a 200-mesh sieve.

[0064] Example 14: This example differs from Example 1 in that 0.4% by mass of a composite enzyme is added to the pretreated wood powder, the composite enzyme comprising cellulase, pectinase, and chitosanase in a mass ratio of 1:0.8:0.4, and enzymolysis is carried out at 25°C for 4.5 hours.

[0065] Example 15: This example differs from Example 1 in that 0.8% by mass of a composite enzyme is added to the pretreated wood powder, the composite enzyme comprising cellulase, pectinase, and chitosanase in a mass ratio of 1:0.8:0.6, and enzymolysis is carried out at 35°C for 6.5 hours.

[0066] Example 16: This example differs from Example 1 in that the enzymatic hydrolyzed material is continuously extracted with ethanol for 5 h, the obtained extract is concentrated until the volume no longer changes, and then dried at 50°C to constant weight.

[0067] Example 17: This example differs from Example 1 in that the enzymatic hydrolyzed material is continuously extracted with ethanol for 7 hours, the obtained extract is concentrated until the volume no longer changes, and then dried at 55°C to constant weight.

[0068] Example 18: This example differs from Example 1 in that 0.2% of the mass of microalgae biofertilizer is added to the first soil for repair; after drying, the first repair soil and 0.5% of the mass of the second soil are added for repair; after bombardment, the second repair soil and 1% of the mass of the second soil are added for repair.

[0069] Example 19: This example differs from Example 1 in that 0.4% of the mass of microalgae biofertilizer is added to the first soil for repair; after drying, the first repair soil and 0.8% of the mass of the second soil are added for repair; after bombardment, the second repair soil and 1.5% of the mass of the second soil are added for repair.

[0070] Example 20: This example differs from Example 1 in that magnetized water twice the mass of the second soil is added to the second soil and mixed and pulse treated. The magnetized water is tap water treated at a magnetic field strength of 0.3 T for 5.5 hours. The DC voltage of the pulse treatment is 0.8 V and the time is 10 minutes.

[0071] Example 21: This example differs from Example 1 in that magnetized water, which is five times the mass of the second soil, is added to the second soil and mixed and pulse treated. The magnetized water is tap water treated at a magnetic field strength of 0.4 T for 7.5 hours. The DC voltage of the pulse treatment is 2.5 V and the time is 20 minutes.

[0072] Example 22: This example differs from Example 1 in that the radio frequency power is 220 W, the pressure is 55 Pa, and the bombardment time is 20 min.

[0073] Example 23: This example differs from Example 1 in that the radio frequency power is 280 W, the pressure is 65 Pa, and the bombardment time is 30 min.

[0074] Example 24: This example differs from Example 1 in that the mixture is stirred at a speed of 600 r / min for 25 min and then allowed to stand for 50 min.

[0075] Example 25: This example is different from Example 1 in that the stirring is carried out at a rotation speed of 800 r / min for 35 min and the mixture is allowed to stand for 80 min after the stirring is completed.

[0076] Experimental Example: The description of this experimental example is based on the scheme described in Example 1, and is intended to illustrate the practical application effect of the present invention.

[0077] The remediation methods of the various embodiments of the present application were used to remediate saline-alkali soil with a pH of 8.5 to 9.5 and a total salt content of 3.5 to 9.5 g / kg. The reduction in soil pH and total salt content before and after the remediation of the saline-alkali soil was detected as experimental data support for the present application.

[0078] Exploration 1. Investigate the effects of the components and preparation parameters of microalgae biofertilizer on the pH reduction rate and total salt content reduction rate of saline-alkali soil.

[0079] The difference between Control Example 1 and Example 1 is that no Rhus chinensis extract is added to the microalgae biofertilizer;

[0080] Depend on Figure 1 and Figure 2 The results show that the control example 1 lacks the Rhus chinensis extract, which on the one hand reduces the concentration of the carbon source required by the microalgae, and thus the survival rate of the microalgae is reduced compared with Examples 1 to 9. On the other hand, it reduces the neutralization effect of the Rhus chinensis extract on the hydroxide ions in the saline-alkali soil, ultimately resulting in a significant reduction in the pH reduction rate and total salt content reduction rate of the saline-alkali soil in the control example 1 compared with Examples 1 to 9.

[0081] By comparing Examples 1 to 9, it can be seen that when the proportion of Rhus chinensis extract is too small or too large, the proportion of Chlorella vulgaris is too small or too large, the proportion of Bacillus subtilis is too small or too large, and the parameters of aerated composting are too small or too large, the pH reduction rate and the total salt content reduction rate of the saline-alkali soil will be reduced. Therefore, from a comprehensive perspective, the parameter effect of Example 1 is relatively better.

[0082] Exploration 2: Investigate the effects of the components and preparation parameters of microalgae biofertilizer on the pH reduction rate and total salt content reduction rate of saline-alkali soil.

[0083] The difference between Control Example 2 and Example 1 is that Rhus chinensis is not pretreated;

[0084] Depend on Figure 3 and Figure 4 The results show that the control example 2 lacks pretreatment of Rhus chinensis, so the lignin structure of Rhus chinensis is not completely destroyed, which affects the subsequent enzymatic hydrolysis and extraction effect, and the conversion rate of the subsequent substance into a carbon source for microalgae decreases, resulting in the pH reduction rate and total salt content reduction rate of the saline-alkali soil in the control example 2 being significantly lower than those in Example 1 and Examples 10 to 17;

[0085] By comparing Example 1 and Examples 10 to 17, it can be seen that when the steam explosion parameters of Rhus chinensis are too small or too large, the freeze-thaw parameters are too small or too large, the enzymatic hydrolysis parameters are too small or too large, and the extraction parameters are too small or too large, the pH reduction rate and the total salt content reduction rate of the saline-alkali soil are reduced. Therefore, from a comprehensive perspective, the parameter effect of Example 1 is relatively better.

[0086] Exploration 3. Investigate the effects of saline-alkali soil remediation process parameters on the pH reduction rate and total salt content reduction rate of saline-alkali soil.

[0087] The difference between Control Example 3 and Example 1 is that the saline-alkali soil is not classified by particle size, and the saline-alkali soil and the microalgae biofertilizer are mixed and repaired all at once;

[0088] Comparative Example 4 differs from Example 1 in that the second soil is subjected to ordinary water mixing and pulse treatment;

[0089] Comparative Example 5 differs from Example 1 in that the third soil is not subjected to plasma bombardment;

[0090] Depend on Figure 5 and Figure 6 The results show that Control Example 3 lacks separate treatment for saline-alkali soil particle size, resulting in different absorption effects of saline-alkali soils with different particle sizes on microalgae biofertilizers and uneven repair effects; Control Example 4 lacks magnetization of water, and the untreated ordinary water molecule clusters are large and have poor permeability, which cannot effectively destroy the soil colloid adsorption sites, resulting in a decrease in the desalination efficiency of the second soil; Control Example 5 does not perform plasma bombardment on the third soil, so the third soil with large particle size lacks a pore network, and the microbial colonization rate is reduced; Therefore, the pH reduction rate and total salt content reduction rate of the saline-alkali soil in Control Examples 3 to 5 are significantly reduced compared with Example 1 and Example 18 to Example 25;

[0091] By comparing Example 1 and Examples 18 to 25, it can be seen that the addition amount of microalgae bio-fertilizer is too small or too large, the treatment parameters of the second soil are too small or too large, the plasma bombardment parameters are too small or too large, and the remediation parameters of the microalgae bio-fertilizer are too small. The pH reduction rate and the total salt content reduction rate of the saline-alkali soil will be reduced. The remediation parameters of the microalgae bio-fertilizer in Example 25 are larger, so the pH reduction rate and the total salt content reduction rate of the saline-alkali soil are improved compared with those in Example 1, but the increase is smaller than the increase in the remediation parameters. Therefore, from an economic point of view, the parameter effect of Example 1 is relatively better.

Claims

1. A method for repairing saline-alkali soil based on microalgae biofertilizer, characterized in that: The following steps are involved: S1, mixing the microalgae composite liquid, Rhus chinensis extract, and livestock manure in a mass ratio of 1:8-10:1.2 to obtain a fermentation product, adding 0.1-0.15% of the mass of the composite bacterial agent to the fermentation product, mixing and composting, ventilating for 15-20 minutes every hour at a ventilation rate of 3-5 L / min, and composting for 22-25 days to obtain a microalgae biofertilizer; The preparation method of the Rhus chinensis extract is: Rhus chinensis is treated under steam at 1.5-2.5 MPa and 90-105° C. for 5-40 minutes and ground to obtain a powder. The powder is then mixed with deionized water at a solid-liquid ratio of 1 g:3-5 ml to obtain a suspension. The suspension is heated at 70-80° C. for 1.5-2 hours, then transferred to -70--50° C. and frozen for 10-12 hours. After freezing, the suspension is thawed at 30-35° C. for 2.5-3.5 hours. Finally, the suspension is dried at 50-55° C. for 2-3 hours and ground through a 100-200 mesh sieve to obtain a pretreated powder. Adding 0.4-0.8% of a complex enzyme by weight to the pretreated powder, performing enzymatic hydrolysis at 25-35° C. for 4.5-6.5 hours to obtain an enzymatic hydrolyzed material, drying the enzymatic hydrolyzed material to a moisture content of less than 5%, continuously extracting the enzymatic hydrolyzed material with ethanol for 5-7 hours, concentrating the obtained extract until the volume no longer changes, and then drying the extract at 50-55° C. to a constant weight to obtain a Rhus chinensis extract; S2. Classify the saline-alkali soil into a first soil with a particle size of less than 0.5 mm, a second soil with a particle size of 0.5 to 1 mm, and a third soil with a particle size of more than 1 mm; S2-1, adding 0.2-0.4% of the mass of microalgae biofertilizer to the first soil for remediation, to obtain a first remediated soil; S2-2, adding 2 to 5 times the mass of magnetized water to the second soil and mixing and pulse treating, drying in the sun for 6 to 8 days after the pulse treatment, and adding the first remediation soil and 0.5 to 0.8% of the mass of the second soil to the microalgae biofertilizer for remediation to obtain a second remediation soil; S2-3. Plasma bombardment is performed on the third soil. After the bombardment is completed, the second remediation soil and microalgae biofertilizer accounting for 1 to 1.5% of the mass of the third soil are added for remediation. The remediation is completed.

2. A method for repairing saline-alkali soil based on microalgae biofertilizer according to claim 1, characterized in that: The complex enzyme comprises cellulase, pectinase and chitosanase in a mass ratio of 1:0.8:0.4-0.

6.

3. A method for repairing saline-alkali soil based on microalgae biofertilizer according to claim 1, characterized in that: The microalgae composite liquid comprises Chlorella vulgaris, Scenedesmus quadricauda and Scenedesmus obliquus in a mass ratio of 0.8:1:1.2-1.

8.

4. A method for repairing saline-alkali soil based on microalgae biofertilizer according to claim 1, characterized in that: The composite bacterial agent comprises a Bacillus subtilis solution, a nitrogen-fixing bacteria solution and a Microbacterium ginseng solution in a mass ratio of 3 to 4:2:1, wherein the content of live bacteria of Bacillus subtilis in the Bacillus subtilis solution, the content of live bacteria of nitrogen-fixing bacteria in the nitrogen-fixing bacteria solution and the content of live bacteria of Microbacterium ginseng in the Microbacterium ginseng solution are all 8×10 6~7 CFU / ml.

5. The method for repairing saline-alkali soil based on microalgae biofertilizer according to claim 1, characterized in that: The livestock manure includes any one of pig manure, cow manure and chicken manure.

6. The method for repairing saline-alkali soil based on microalgae biofertilizer according to claim 1, characterized in that: The magnetized water is prepared by treating tap water at a magnetic field strength of 0.3-0.4 T for 5.5-7.5 hours. The DC voltage of the pulse treatment is 0.8-2.5 V, and the time is 10-20 minutes.

7. The method for repairing saline-alkali soil based on microalgae biofertilizer according to claim 1, characterized in that: The parameters of the plasma bombardment include: using oxygen plasma, radio frequency power of 220-280W, pressure of 55-65Pa, and bombardment time of 20-30min.

8. The method for repairing saline-alkali soil based on microalgae biofertilizer according to claim 1, characterized in that: In S2-1 to S2-3, the method of adding microalgae biofertilizer for repair is: stirring at a speed of 600-800 r / min for 25-35 minutes, standing for 50-80 minutes after the stirring is completed, and then washing and filtering, and the repair is completed.

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