Method for repairing saline-alkali soil based on microalgae biological fertilizer

Abstract

The invention relates to the technical field of soil remediation, in particular to a method for remediating saline-alkali soil based on a microalgae biological fertilizer, which comprises the following steps: S1, uniformly mixing a microalgae compound liquid, a rhus chinensis extract and livestock manure to obtain a fermented product, adding a complex microbial inoculant into the fermented product, and uniformly mixing and composting to obtain the microalgae biological fertilizer; s2, the saline-alkali soil is divided into first soil, second soil and third soil according to the particle size; s2-1, repairing the first soil; s2-2, repairing the second soil; and S2-3, the third soil is repaired, and repairing is completed. The saline-alkali soil is divided into the first soil, the second soil and the third soil according to the particle size, the soil structure is recombined after graded remediation, the compound matrix is formed, the capillary salt return path is blocked, the rhus chinensis extract serves as a component of the microalgae biological fertilizer, saline-alkali soil OH <-> can be neutralized, the pH of surface soil is reduced, and the saline-alkali soil remediation effect is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and specifically relates to a method for remediating saline-alkali soil based on microalgae bio-fertilizer. Background Technique

[0002] Saline-alkali soil is a type of soil where salts accumulate. It means that the salts contained in the soil affect the normal growth of crops. Although a large amount of chemical fertilizer input has greatly increased the yield of crops, due to the early large-scale and single use of chemical fertilizers, the soil fertility has declined, the soil salinization has been aggravated, and the soil desertification has expanded.

[0003] Microalgae grow rapidly 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 amounts of nutrients contained in microalgae themselves are relatively limited and may not fully meet the various needs of plant growth and soil remediation.

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

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

[0006] A method for remediating saline-alkali soil based on microalgae bio-fertilizer includes the following steps:

[0007] S1. Mix a microalgae composite solution, sumac extract, and livestock and poultry manure in a mass ratio of 1:8-10:1.2 to obtain a fermented product. Add a composite bacterium agent accounting for 0.1-0.15% of its mass to the fermented product and mix well for composting. Ventilate for 15-20 minutes every 1 hour, with a ventilation volume of 3-5 L / min, and compost for 22-25 days to obtain microalgae bio-fertilizer;

[0008] S2. Divide the saline-alkali soil into a first soil with a particle size <0.5 mm, a second soil with a particle size of 0.5-1 mm, and a third soil with a particle size >1 mm;

[0009] S2-1. Add microalgae bio-fertilizer accounting for 0.2-0.4% of its mass to the first soil for remediation to obtain a first remediated soil;

[0010] S2-2. Add magnetized water 2-5 times the mass of the second soil to the second soil, mix and perform pulse treatment. After the pulse treatment is completed, dry in the sun for 6-8 days. After drying is completed, add the first remediated soil and microalgae bio-fertilizer accounting for 0.5-0.8% of the mass of the second soil for remediation to obtain a second remediated soil;

[0011] S2-3. Perform plasma bombardment on the third soil. After the bombardment is completed, add the second repaired soil and microalgae bio-fertilizer accounting for 1-1.5% of the mass of the second soil for repair, and the repair is completed.

[0012] Furthermore, the preparation method of the sumac extract is as follows:

[0013] Treat sumac under steam at 1.5-2.5 MPa and 90-105 °C for 5-40 min, and grind to obtain powder. Then mix the powder with deionized water at a solid-liquid ratio of 1 g: 3-5 ml to obtain a suspension, and heat the suspension at 70-80 °C for 1.5-2 h. Subsequently, transfer it to -70--50 °C for freezing for 10-12 h. After the freezing is completed, thaw it at 30-35 °C for 2.5-3.5 h. Finally, dry it at 50-55 °C for 2-3 h and grind it through a 100-200 mesh sieve to obtain the pretreated powder;

[0014] Add composite enzyme accounting for 0.4-0.8% of the mass of the pretreated wood powder, and perform enzymatic hydrolysis at 25-35 °C for 4.5-6.5 h to obtain the enzymatically hydrolyzed material and dry it to a water content of <5%. Then continuously extract the enzymatically hydrolyzed material with ethanol for 5-7 h, concentrate the obtained extract until the volume no longer changes, and then dry it to a constant weight at 50-55 °C to obtain the sumac extract.

[0015] Note: Steam explosion destroys the lignin-hemicellulose composite structure of sumac, combines with freeze-thaw to generate mechanical stress, improves the cell wall porosity, and increases the dissolution rate of flavonoids (quercetin, myricetin) and phenolic acids (gallic acid); adding composite enzyme converts polysaccharides into soluble oligosaccharides, increasing the carbon source available for microalgae, and quercetin in the extract forms a composite micelle with polysaccharides, which can scavenge excessive reactive oxygen species in saline-alkali land and improve the survival rate of microalgae; citric acid and tartaric acid in the extract combine with the microporous structure generated by freeze-thaw to neutralize OH - in the surface soil, reducing the pH of the surface soil.

[0016] Furthermore, the composite enzyme includes cellulase, pectinase, and chitosanase with a mass ratio of 1: 0.8: 0.4-0.6.

[0017] Note: Cellulase specifically cuts the β-1,4-glycosidic bond, degrades the cellulose microfibrils exposed after steam explosion into cellobiose and glucose, improves the cell wall porosity, and increases the subsequent dissolution rate of flavonoids; pectinase cleaves the galacturonan in the middle lamella of cells, releases phenolic acids wrapped by pectin, and at the same time reduces the viscosity of the extraction solution and accelerates mass transfer; chitosanase targets and decomposes the residual chitosan of possible fungal symbionts, increases the carbon source of microalgae, and can also induce the expression of plant stress-resistant genes and enhance the salt tolerance of plants.

[0018] Furthermore, the microalgae composite solution includes chlorella, scenedesmus quadricauda, and scenedesmus obliquus with a mass ratio of 0.8:1:1.2 to 1.8.

[0019] Explanation: Chlorella can utilize organic carbon sources for growth and reproduction, and has a fast growth and reproduction rate, which helps to rapidly 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 a fast growth rate, and can grow in saline-alkali environments, which helps to improve the soil conditions of saline-alkali land.

[0020] Furthermore, the compound microbial agent includes bacillus subtilis liquid, azotobacter liquid, and microbacterium ginsengisoli liquid with a mass ratio of 3 to 4:2:1. The viable bacteria content of bacillus subtilis in the bacillus subtilis liquid, the viable bacteria content of azotobacter in the azotobacter liquid, and the viable bacteria content of microbacterium ginsengisoli in the microbacterium ginsengisoli liquid is 8×10 6～7 CFU / ml.

[0021] Explanation: Bacillus subtilis has the strongest stress resistance, diverse functions, wide adaptability, and stable effects; azotobacter participates in the regulation of soil salinity through biochemical processes, reducing the soil salinity; microbacterium ginsengisoli has the ability to promote plant growth under saline-alkali conditions.

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

[0023] Explanation: Pig manure, cow manure, and chicken manure are all high-quality organic fertilizers, with rich nutrient components and good fertilizer effects.

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

[0025] Explanation: Treating the second soil with magnetized water reduces the diameter of water molecular clusters, increases the dissolved oxygen content, promotes the ion exchange efficiency with sodium ions, and the cavitation effect generated by the pulse treatment can destroy the salt adsorption sites of soil colloids, shortening the desalination period.

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

[0027] Explanation: Plasma bombardment generates nano-scale pores on the surface of the third soil, increasing the specific surface area, thereby enhancing the adsorption amount of the microalgae bio-fertilizer.

[0028] Furthermore, in S2-1 to S2-3, the method of adding microalgae bio-fertilizer for remediation is as follows: Stir at a speed of 600-800 r / min for 25-35 min, let it stand for 50-80 min after stirring, and then wash and filter to complete the remediation.

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

[0030] Compared with the existing methods for remediating saline-alkali soil, the beneficial effects of the present invention are as follows:

[0031] (1) In this application, the saline-alkali soil is divided into first soil, second soil and third soil according to particle size. The first soil has strong salt adsorption capacity. It is directly remediated with microalgae bio-fertilizer, using the sodium ion replacement ability of sumac extract and the binding effect of microalgae extracellular polysaccharide to reduce the soil sodium adsorption ratio. The second soil accelerates the migration of salt ions through magnetized water pulse treatment, combines with sun drying to promote the precipitation of salt crystals, and then adds microalgae fertilizer to form water-stable aggregates. The third soil is bombarded by plasma to generate nano-scale pores, enhancing the microbial colonization efficiency and increasing the penetration depth of microalgae bio-fertilizer for remediation. After hierarchical remediation, the soil structure is reorganized to form a composite matrix, blocking the capillary salt return path.

[0032] (2) In this application, sumac extract is added to the microalgae bio-fertilizer. The sumac extract destroys the lignin-cellulose composite structure of sumac through steam explosion, combines with freeze-thaw to generate mechanical stress, increasing the cell wall porosity and the dissolution rate of flavonoids and phenolic acids. Adding composite enzymes converts polysaccharides into soluble oligosaccharides, increasing the available carbon source for microalgae, thereby improving the remediation activity of microalgae in saline-alkali soil. Moreover, quercetin in the extract forms a composite micelle with polysaccharides, which can remove excessive reactive oxygen species in the saline-alkali land, further increasing the survival rate of microalgae. In addition, citric acid and tartaric acid in the sumac extract combine with the microporous structure generated by pretreatment to neutralize the hydroxide ions in the saline-alkali soil, reducing the pH of the saline-alkali soil. Description of the Drawings

[0033] Figure 1 It is a comparison chart of the pH reduction rate of Exploration 1 of the present invention;

[0034] Figure 2 It is a comparison chart of the total salt content reduction rate of Exploration 1 of the present invention;

[0035] Figure 3 It is a comparison chart of the pH reduction rate of Exploration 2 of the present invention;

[0036] Figure 4 It is a comparison chart of the total salt content reduction rate of Exploration 2 of the present invention;

[0037] Figure 5 It is the comparison chart of the pH reduction rate of Exploration 3 of the present invention;

[0038] Figure 6 It is the comparison chart of the total salt content reduction rate of Exploration 3 of the present invention. Detailed implementation manners

[0039] To further elaborate on the methods adopted and the effects achieved by the present invention, the technical solutions of the present invention will be clearly and completely described below in combination with experiments.

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

[0041] S1. Mix the microalgae composite solution, sumac extract, and livestock and poultry manure in a mass ratio of 1:9:1.2 to obtain a fermented product.

[0042] The preparation method of the sumac extract is as follows:

[0043] Treat sumac under steam at 2 MPa and 100 °C for 25 min, grind it through a 50-mesh sieve to obtain powder, then mix the powder with deionized water at a solid-liquid ratio of 1 g:4 ml to obtain a suspension, heat the suspension at 75 °C for 1.8 h, then transfer it to -60 °C for freezing for 11 h, thaw it at 33 °C for 3 h after freezing, and finally dry it at 53 °C for 2.5 h and grind it through a 150-mesh sieve to obtain a pretreated powder.

[0044] Add a composite enzyme accounting for 0.6% of the mass of the pretreated wood powder to the pretreated wood powder. The composite enzyme includes cellulase, pectinase, and chitosanase with a mass ratio of 1:0.8:0.5. The enzyme activities of cellulase, pectinase, and chitosanase are all 400 u / g. Enzymolysis is carried out at 30 °C for 5.5 h to obtain an enzymolyzed product and dry it to a water content of 4%. Then continuously extract the enzymolyzed product with ethanol for 6 h, concentrate the obtained extract until the volume no longer changes, and then dry it to a constant weight at 53 °C to obtain the sumac extract.

[0045] The microalgae composite solution includes Chlorella vulgaris, Scenedesmus quadricauda, and Scenedesmus obliquus with a mass ratio of 0.8:1:1.5.

[0046] Add a composite microbial agent accounting for 0.13% of the mass of the fermented product to the fermented product and mix well for composting. The composite microbial agent includes Bacillus subtilis liquid, Azotobacter liquid, and Microbacterium ginsengisoli liquid with a mass ratio of 3.5:2:1. The viable bacteria content of Bacillus subtilis N24 in the Bacillus subtilis liquid, the viable bacteria content of Azotobacter R31 in the Azotobacter liquid, and the viable bacteria content of Microbacterium ginsengisoli S4 in the Microbacterium ginsengisoli liquid are all 4×10 7CFU / ml, ventilate for 18 minutes every 1 hour, the ventilation volume is 4 L / min, and compost for 23 days to obtain microalgae bio-fertilizer;

[0047] S2. Divide the saline-alkali soil into the first soil with a particle size < 0.5 mm, the second soil with a particle size of 0.5 - 1 mm, and the third soil with a particle size > 1 mm;

[0048] S2-1. Add 0.3% of the microalgae bio-fertilizer by mass of the first soil for remediation to obtain the first remediated soil;

[0049] S2-2. Add magnetized water 3.5 times the mass of the second soil to the second soil, mix and perform pulse treatment. The magnetized water is prepared by treating tap water for 6.5 hours under a magnetic field intensity of 0.35 T. The DC voltage of the pulse treatment is 1.7 V, and the time is 15 minutes. After the pulse treatment, dry in the sun for 7 days. After drying, add the first remediated soil and 0.65% of the microalgae bio-fertilizer by mass of the second soil for remediation to obtain the second remediated soil;

[0050] S2-3. Perform plasma bombardment on the third soil. The parameters of the plasma bombardment include: using oxygen plasma, the radio frequency power is 240 W, the pressure is 60 Pa, and the bombardment time is 25 minutes. After the bombardment, add the second remediated soil and 1.2% of the microalgae bio-fertilizer by mass of the second soil for remediation;

[0051] In S2-1 to S2-3, the method of adding microalgae bio-fertilizer for remediation is: stir at a speed of 700 r / min for 30 minutes, let stand for 65 minutes after stirring, and then wash and filter to complete the remediation.

[0052] Example 2: The difference between this example and Example 1 is that the microalgae complex liquid, sumac extract, and livestock and poultry manure are mixed evenly according to a mass ratio of 1:8:1.2 to obtain a fermented product, and 0.1% of a compound bacterial agent by mass of the fermented product is added and mixed evenly for composting.

[0053] Example 3: The difference between this example and Example 1 is that the microalgae complex liquid, sumac extract, and livestock and poultry manure are mixed evenly according to a mass ratio of 1:10:1.2 to obtain a fermented product, and 0.15% of a compound bacterial agent by mass of the fermented product is added and mixed evenly for composting.

[0054] Example 4: The difference between this example and Example 1 is that the microalgae complex liquid includes Chlorella vulgaris, Scenedesmus quadricauda, and Scenedesmus obliquus with a mass ratio of 0.8:1:1.2.

[0055] Example 5: The difference between this example and Example 1 is that the microalgae complex liquid includes Chlorella vulgaris, Scenedesmus quadricauda, and Scenedesmus obliquus with a mass ratio of 0.8:1:1.8.

[0056] Example 6: The difference between this example and Example 1 is that the composite bacterial agent includes Bacillus subtilis liquid, Azotobacter liquid, and Microbacterium ginsengisoli liquid with a mass ratio of 3:2:1. The viable count of Bacillus subtilis in the Bacillus subtilis liquid is 8×10 6 CFU / ml, and the viable counts of Azotobacter in the Azotobacter liquid and Microbacterium ginsengisoli in the Microbacterium ginsengisoli liquid are both 8×10 7 CFU / ml.

[0057] Example 7: The difference between this example and Example 1 is that the composite bacterial agent includes Bacillus subtilis liquid, Azotobacter liquid, and Microbacterium ginsengisoli liquid with a mass ratio of 4:2:1. The viable count of Bacillus subtilis in the Bacillus subtilis liquid is 8×10 7 CFU / ml, and the viable counts of Azotobacter in the Azotobacter liquid and Microbacterium ginsengisoli in the Microbacterium ginsengisoli liquid are both 8×10 6 CFU / ml.

[0058] Example 8: The difference between this example and Example 1 is that ventilation is carried out for 15 minutes every 1 hour, the ventilation volume is 3 L / min, and composting is carried out for 22 days.

[0059] Example 9: The difference between this example and Example 1 is that ventilation is carried out for 20 minutes every 1 hour, the ventilation volume is 5 L / min, and composting is carried out for 25 days.

[0060] Example 10: The difference between this example and Example 1 is that Rhus chinensis Mill. is treated with steam at 1.5 MPa and 90 °C for 5 minutes.

[0061] Example 11: The difference between this example and Example 1 is that Rhus chinensis Mill. is treated with steam at 2.5 MPa and 105 °C for 40 minutes.

[0062] Example 12: The difference between this example and Example 1 is 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 for freezing 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: The difference between this example and Example 1 is 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 for freezing 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: The difference between this example and Example 1 is that a composite enzyme accounting for 0.4% of the mass of the pretreated wood powder is added thereto. The composite enzyme comprises cellulase, pectinase and chitosanase with a mass ratio of 1:0.8:0.4, and enzymatic hydrolysis is carried out at 25 °C for 4.5 h.

[0065] Example 15: The difference between this example and Example 1 is that a composite enzyme accounting for 0.8% of the mass of the pretreated wood powder is added thereto. The composite enzyme comprises cellulase, pectinase and chitosanase with a mass ratio of 1:0.8:0.6, and enzymatic hydrolysis is carried out at 35 °C for 6.5 h.

[0066] Example 16: The difference between this example and Example 1 is that the enzymolysis material is continuously extracted with ethanol for 5 h, the obtained extract is concentrated until the volume no longer changes, and then dried to a constant weight at 50 °C.

[0067] Example 17: The difference between this example and Example 1 is that the enzymolysis material is continuously extracted with ethanol for 7 h, the obtained extract is concentrated until the volume no longer changes, and then dried to a constant weight at 55 °C.

[0068] Example 18: The difference between this example and Example 1 is that microalgae bio-fertilizer accounting for 0.2% of the mass of the first soil is added for remediation. After drying, the first remediation soil and microalgae bio-fertilizer accounting for 0.5% of the mass of the second soil are added for remediation; after bombardment, the second remediation soil and microalgae bio-fertilizer accounting for 1% of the mass of the second soil are added for remediation.

[0069] Example 19: The difference between this example and Example 1 is that microalgae bio-fertilizer accounting for 0.4% of the mass of the first soil is added for remediation. After drying, the first remediation soil and microalgae bio-fertilizer accounting for 0.8% of the mass of the second soil are added for remediation; after bombardment, the second remediation soil and microalgae bio-fertilizer accounting for 1.5% of the mass of the second soil are added for remediation.

[0070] Example 20: The difference between this example and Example 1 is that magnetized water accounting for 2 times the mass of the second soil is added thereto for mixing and pulse treatment. The magnetized water is obtained by treating tap water at a magnetic field intensity of 0.3 T for 5.5 h, and the direct current voltage of the pulse treatment is 0.8 V and the time is 10 min.

[0071] Example 21: The difference between this example and Example 1 is that magnetized water accounting for 5 times the mass of the second soil is added thereto for mixing and pulse treatment. The magnetized water is obtained by treating tap water at a magnetic field intensity of 0.4 T for 7.5 h, and the direct current voltage of the pulse treatment is 2.5 V and the time is 20 min.

[0072] Example 22: The difference between this example and Example 1 is that the radio frequency power is 220 W, the pressure is 55 Pa, and the bombardment time is 20 min.

[0073] Example 23: The difference between this example and Example 1 is that the radio frequency power is 280 W, the pressure is 65 Pa, and the bombardment time is 30 min.

[0074] Example 24: The difference between this example and Example 1 is that it is stirred at a speed of 600 r / min for 25 min, and then left standing for 50 min after the stirring ends.

[0075] Example 25: The difference between this example and Example 1 is that it is stirred at a speed of 800 r / min for 35 min, and then left standing for 80 min after the stirring ends.

[0076] Experimental example: This experimental example is based on the recording scheme in Example 1, aiming to clarify the actual application effect of the present invention.

[0077] The saline-alkali soil with a pH of 8.5 - 9.5 and a total salt content of 3.5 - 9.5 g / kg is repaired by using the repair methods of each embodiment of the present application, and the reduction ranges of the soil pH and the total salt content of the saline-alkali soil before and after the repair are detected as the experimental data support of the present application.

[0078] Investigation 1: Explore the effects of the components and preparation parameters of the microalgae bio-fertilizer on the pH reduction rate and the total salt content reduction rate of the saline-alkali soil.

[0079] The difference between Comparative Example 1 and Example 1 is that the sumac extract is not added to the microalgae bio-fertilizer;

[0080] From Figure 1 and Figure 2 the results, it can be seen that Comparative Example 1 lacks the sumac extract. On the one hand, it reduces the concentration of the carbon source required by the microalgae, and thus the survival rate of the microalgae decreases compared with Examples 1 - 9. On the other hand, it reduces the neutralization effect of the sumac extract on the hydroxide ions in the saline-alkali soil, and finally leads to a significant decrease in the pH reduction rate and the total salt content reduction rate of the saline-alkali soil in Comparative Example 1 compared with Examples 1 - 9;

[0081] By comparing Examples 1 - 9, it can be seen that too small or too large a proportion of the sumac extract, too small or too large a proportion of the chlorella, too small or too large a proportion of the bacillus subtilis, and too small or too large a parameter of the aerated composting will all reduce the pH reduction rate and the total salt content reduction rate of the saline-alkali soil. Therefore, from a comprehensive perspective, the parameter effect of Example 1 is relatively better.

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

[0083] The difference between Comparative Example 2 and Example 1 is that the sumac is not pretreated.

[0084] From Figure 3 and Figure 4 The results show that in Comparative Example 2, the lack of pretreatment of sumac results in incomplete destruction of the lignin structure of sumac, which affects the subsequent enzymatic hydrolysis extraction effect. Then, the conversion rate of the subsequent substances into the carbon source of microalgae decreases, leading to a significant decrease in the pH reduction rate and total salt content reduction rate of the saline-alkali soil in Comparative Example 2 compared with those in Example 1 and Examples 10 to 17.

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

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

[0087] The difference between Comparative Example 3 and Example 1 is that the saline-alkali soil is not classified by particle size, and the whole saline-alkali soil and microalgae bio-fertilizer are mixed and remediated all at once.

[0088] The difference between Comparative Example 4 and Example 1 is that ordinary water mixing and pulse treatment are performed on the second soil.

[0089] The difference between Comparative Example 5 and Example 1 is that the third soil is not bombarded by plasma.

[0090] From Figure 5 and Figure 6 The results show that in Comparative Example 3, the lack of separate treatment for the particle size of saline-alkali soil leads to different absorption effects of saline-alkali soil with different particle sizes on microalgae bio-fertilizer and uneven remediation effects. In Comparative Example 4, the lack of magnetization of water results in large-sized ordinary water molecular clusters with poor permeability, which cannot effectively destroy the soil colloid adsorption sites, leading to a decrease in the desalination efficiency of the second soil. In Comparative Example 5, the third soil is not bombarded by plasma, so the large-sized third soil has a reduced microbial colonization rate due to the lack of pore networks. Therefore, the pH reduction rate and total salt content reduction rate of the saline-alkali soil in Comparative Examples 3 to 5 are significantly lower than those in Example 1 and Examples 18 to 25.

[0091] Comparing Comparative Example 1, Examples 18 to 25, it can be seen that if the addition amount of the microalgae bio-fertilizer is too small or too large, the treatment parameters for the second soil are too small or too large, the plasma bombardment parameters are too small or too large, and the repair 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 decrease. In Example 25, the repair parameters of the microalgae bio-fertilizer are relatively large, 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. However, the improvement amplitude is smaller than the increase amplitude of the repair parameters. Therefore, from the economic perspective, 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 a composite bacterial agent accounting for 0.1-0.15% of the mass of the fermentation product to mix and compost, ventilating for 15-20 minutes every 1 hour, with a ventilation rate of 3-5 L / min, and composting for 22-25 days to obtain a microalgae bio-fertilizer; 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 microalgae biofertilizer by mass to the first soil for restoration, to obtain a first restored soil; S2-2, adding magnetized water accounting for 2 to 5 times the mass of the second soil to mix and pulse treat, drying for 6 to 8 days after the pulse treatment, adding the first repaired soil and microalgae biofertilizer accounting for 0.5 to 0.8% of the mass of the second soil to repair, and obtaining a second repaired soil; S2-3, plasma bombarding the third soil, adding the second repair soil and microalgae biofertilizer accounting for 1 to 1.5% of the mass of the second soil to perform repair after the bombardment is completed, and the repair is completed.

2. A method for repairing saline-alkali soil based on microalgae biofertilizer as claimed in claim 1, characterized in that: The preparation method of the Rhus chinensis extract is: Treat Rhus chinensis with steam at 1.5-2.5MPa and 90-105°C for 5-40min, grind to obtain powder, mix the powder with deionized water at a solid-liquid ratio of 1g:3-5ml to obtain a suspension, heat the suspension at 70-80°C for 1.5-2h, then transfer to -70--50°C and freeze for 10-12h, thaw at 30-35°C for 2.5-3.5h after freezing, and finally dry at 50-55°C for 2-3h, grind through a 100-200 mesh sieve to obtain a pretreated powder; The pretreated wood powder is added with a composite enzyme accounting for 0.4-0.8% of the weight thereof, and enzymolysis is performed at 25-35°C for 4.5-6.5 hours to obtain an enzymolysis material, which is dried to a moisture content of less than 5%, and then the enzymolysis material is continuously extracted with ethanol for 5-7 hours, the obtained extract is concentrated until the volume no longer changes, and then dried at 50-55°C to a constant weight to obtain a Rhus chinensis extract.

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

6.

4. A method for repairing saline-alkali soil based on microalgae biofertilizer as claimed in 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.

5. 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 live bacteria content of Bacillus subtilis in the Bacillus subtilis solution, the live bacteria content of nitrogen-fixing bacteria in the nitrogen-fixing bacteria solution and the live bacteria content of Microbacterium ginseng in the Microbacterium ginseng solution are all 8×10 6～7 CFU / ml.

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

7. A method for repairing saline-alkali soil based on microalgae biofertilizer as claimed in claim 1, characterized in that: The magnetized water is prepared by treating tap water at a magnetic field strength of 0.3-0.4T for 5.5-7.5h. The direct current voltage of the pulse treatment is 0.8-2.5V and the time is 10-20min.

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

9. A method for repairing saline-alkali soil based on microalgae biofertilizer as claimed in 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 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.

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