Freeze-thaw slow-release compound organic fertilizer for alpine soil remediation, preparation method thereof and alpine soil remediation method applying freeze-thaw slow-release compound organic fertilizer

Abstract

The invention relates to the technical field of ecological restoration of soil, and provides a freeze-thaw slow-release compound organic fertilizer for restoring alpine soil, which comprises compound organic fertilizer particles and low-temperature response type hydrogel, the compound organic fertilizer particles comprise an organic fertilizer and a microbial agent, are compounded with the low-temperature response type hydrogel and are wrapped in a low-temperature response type hydrogel network; the LCST temperature of the low-temperature response type hydrogel is 5-8 DEG C, and the low-temperature response type hydrogel absorbs water to swell at the temperature below the LCST temperature and shrinks at the temperature above the LCST temperature, so that water in a hydrogel network and the composite organic fertilizer are slowly released. By utilizing the freeze-thaw slow release principle, according to the change of winter and spring in the alpine region, the organic fertilizer and microorganisms are slowly released in the day unfreezing period in winter and the unfreezing period in spring, so that the microorganisms can safely pass through the winter, the efficient utilization of nutrients can be ensured, and accurate release is realized by matching the freeze-thaw period and is synchronous with the seasonal change of soil.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soil ecological restoration, in particular to a freeze-thaw slow-release composite organic fertilizer for alpine soil restoration, a preparation method thereof and an alpine soil restoration method using the same. BACKGROUND

[0002] The alpine ecosystem is fragile, and engineering construction and mining development have caused serious damage to the soil, resulting in soil structure destruction, massive loss of organic matter and imbalance of microbial community, which has led to serious degradation of soil ecological function and posed a major challenge to vegetation restoration.

[0003] When the damaged soil in the alpine region is restored with vegetation, the soil aggregates are disintegrated and hardened due to the significant diurnal temperature difference in the region, causing mechanical damage to plant roots. Meanwhile, the frozen soil layer isolates nutrient absorption, and the runoff during the thawing period intensifies nutrient loss. In addition, the plant growth suitable period in the alpine region is only 3-4 months, and nutrients need to be supplied quickly during the thawing window period. However, the release rate of traditional slow-release fertilizers is delayed in low-temperature environments, which cannot match the plant demand, and the freeze-thaw cycle in winter causes the film to rupture, leading to explosive release and loss of nutrients.

[0004] In view of the above problems, it is urgent to develop a slow-release fertilizer suitable for soil restoration in the alpine region. SUMMARY

[0005] To solve the problems in the background art, the present application provides a freeze-thaw slow-release composite organic fertilizer for alpine soil restoration, a preparation method thereof and an alpine soil restoration method using the same, which improves the efficiency and quality of soil restoration in the alpine environment. The technical solution of the present application to solve the above technical problems is as follows: In a first aspect, the present application provides a freeze-thaw slow-release composite organic fertilizer for alpine soil restoration, comprising composite organic fertilizer particles and low-temperature responsive hydrogel. The composite organic fertilizer particles comprise organic fertilizer and microbial inoculum, and the composite organic fertilizer particles are compounded with low-temperature responsive hydrogel and wrapped in the low-temperature responsive hydrogel network. The LCST temperature of the low-temperature responsive hydrogel is 5-8℃, which swells below the LCST temperature and shrinks above the LCST temperature, slowly releasing the water in the hydrogel network and the composite organic fertilizer particles.

[0006] According to the above scheme, the mass ratio of the composite organic fertilizer particles to the low-temperature responsive hydrogel is 3:7-1:1.

[0007] According to the above scheme, the composite organic fertilizer particles are prepared by fermenting microbial inoculum and organic fertilizer raw materials in an environment of 5-15℃.

[0008] According to the above scheme, the microbial inoculant is a low-temperature resistant inoculant composed of one or more strains, which has the functions of nitrogen fixation, phosphorus solubilization and organic matter degradation at a temperature range of 5-15°C.

[0009] The microbial inoculant can be selected as needed, and when composed of more than one strain, the ratio between the strains can be adjusted according to actual needs. In some specific embodiments of the present application, the microbial inoculant includes Bacillus, Pseudomonas and Flavobacterium microorganisms, such as cold-tolerant Bacillus (purchased from China Ocean Microbial Culture Collection Center 1A21810), cold-tolerant Pseudomonas (purchased from China Typical Culture Collection Center CCTCC AB 2012401), and cold-tolerant Flavobacterium (China Ocean Microbial Culture Collection Center 1A07913), and the above three strains are mixed at a mass ratio of 1:1:1. Other strains with the same functions on the market can also be selected. The microbial inoculant is activated by aeration with brown sugar water before application, and is resuspended after centrifugation.

[0010] According to the above scheme, the microbial inoculant is inoculated into the organic fertilizer raw material, fermented, dried and crushed after composting to obtain the composite organic fertilizer.

[0011] According to the above scheme, the temperature at the start of fermentation is 15-25°C, and the time is 3-5 days, and the environmental temperature at the fermentation stage is 5-15°C, and the time is 30-60 days.

[0012] In some specific embodiments of the present application, the organic fertilizer raw material is a mixed raw material obtained by mixing straw, animal manure and mushroom residue at a certain ratio. Other raw materials can also be selected for fermentation and composting to prepare organic fertilizer.

[0013] According to the above scheme, the low-temperature responsive hydrogel includes a temperature-sensitive material, a natural high-molecular hydrogel matrix, glycerol, a crosslinking agent and an initiator.

[0014] By combining the temperature-sensitive material and the natural high-molecular hydrogel matrix, the LCST temperature of the low-temperature responsive hydrogel can be adjusted, and glycerol can ensure the freeze-thaw resistance of the slow-release composite organic fertilizer at low temperatures.

[0015] According to the above scheme, the temperature-sensitive material is N-isopropyl acrylamide, and the natural high-molecular hydrogel matrix is chitosan or sodium alginate.

[0016] According to the above scheme, the low-temperature responsive hydrogel includes the following components in mass fractions: temperature-sensitive material 15-20 parts, natural high-molecular hydrogel matrix 12-18 parts, glycerol 10-14 parts, crosslinking agent 0.3-0.8 parts, and initiator 0.3-0.8 parts.

[0017] In a preferred embodiment, the low-temperature responsive hydrogel comprises the following components by mass fraction: 18 parts of N-isopropyl acrylamide, 15 parts of a natural polymer hydrogel matrix, 12 parts of glycerol, 0.5 parts of a crosslinking agent, and 0.5 parts of an initiator.

[0018] According to the above scheme, the freeze-thaw slow-release composite organic fertilizer for high-cold soil remediation further comprises SiO2 aerogel particles, and the mass fraction of the SiO2 aerogel particles is 2%-5% of the composite organic fertilizer.

[0019] The addition of the SiO2 aerogel particles in the freeze-thaw slow-release composite organic fertilizer can increase the heat preservation performance of the hydrogel.

[0020] In a second aspect, the present application provides a preparation method of the freeze-thaw slow-release composite organic fertilizer for high-cold soil remediation, comprising the following steps: S1. Fermenting organic fertilizer raw materials and microbial inoculants in an environment at 5-15°C to obtain a composite organic fertilizer, and preparing the composite organic fertilizer into composite organic fertilizer particles; S2. Preparing a low-temperature responsive hydrogel colloid; S3. Adding the composite organic fertilizer particles into the low-temperature responsive hydrogel colloid, mixing uniformly, solidifying, crushing, and freeze-drying to obtain the freeze-thaw slow-release composite organic fertilizer for high-cold soil remediation.

[0021] In step S1, the microbial inoculants are inoculated at an inoculation amount of 1%-2%, and fermented for 30-60 days. The starting temperature of the fermentation is 15-25°C, and the time is 3-5 days. The environmental temperature during the fermentation stage is 5-15°C, and the time is 30-60 days. After maturation, the composite organic fertilizer is dried and crushed to obtain the composite organic fertilizer.

[0022] Further preferably, the crushed composite organic fertilizer particles are passed through a 100-mesh sieve so that the diameter of the composite organic fertilizer particles is less than 0.15 mm.

[0023] According to the above scheme, in step S2, the natural polymer hydrogel matrix is dissolved and stirred until it becomes a transparent viscous liquid, and the pH value is adjusted. Then, N-isopropyl acrylamide, glycerol, and a crosslinking agent are added and stirred until they are completely dissolved. Oxygen is removed, and an initiator is added for a period of time to obtain a low-temperature responsive hydrogel colloid.

[0024] Preferably, in step S3, the organic composite fertilizer particles and SiO2 aerogel particles are added into the low-temperature responsive hydrogel colloid, and stirred until they are uniformly dispersed. Then, low-temperature solidification is performed at 4°C to make the PNIPAM chain segments shrink and form a dense network to lock the composite organic fertilizer particles.

[0025] In a third aspect, the application provides a method for repairing high-cold soil, in which the freeze-thaw slow-release composite organic fertilizer for repairing high-cold soil is applied to the surface layer of 0-10 cm of the soil in a high-cold region at the end of autumn or the beginning of winter, or is formulated into a suspension for application through a drip irrigation system.

[0026] Further, the method can be applied to vegetation-degraded soil or vegetation restoration of engineering wound backfill soil in a high-cold region.

[0027] Specifically, when used in vegetation-degraded soil, the application amount of the freeze-thaw slow-release composite organic fertilizer is 1%-10% of the mass of the soil in the surface layer; when used in vegetation restoration of engineering wound backfill soil in a high-cold region, the freeze-thaw slow-release composite organic fertilizer is 10%-30% of the mass of the soil in the surface layer.

[0028] Further, in order to prevent the microbial agent from being damaged by high temperature / organic solvent during the embedding stage, resulting in a decrease in activity or replacement of the microbial flora by high-temperature bacteria, an activated microbial agent can be further supplemented and applied during application, and the application amount of the microbial agent is 1%-2% of the mass of the soil in the surface layer.

[0029] The freeze-thaw slow-release composite organic fertilizer of the application absorbs water and swells at a temperature lower than the LCST (5-8℃), locks water, organic fertilizer and microbial agent, and shrinks to release water, organic fertilizer and microbial agent at a temperature higher than the LCST.

[0030] The application has the following beneficial effects: The diurnal temperature difference in a high-cold region is large, the daytime temperature in winter is about 8℃, and the nighttime temperature drops to about -20℃. The freeze-thaw slow-release composite organic fertilizer is applied to the soil at the end of autumn or the beginning of winter, utilizes the freeze-thaw slow-release principle, and is synchronized with the seasonal changes in a high-cold region in winter and spring. The organic fertilizer and microbial agent are slowly released during the daytime thawing period in winter and the thawing period in spring, so that the released microbial agent and nutrients penetrate to the plant root layer with water. The freeze-thaw slow-release composite organic fertilizer absorbs water and swells when the nighttime temperature suddenly drops in winter, so as to wrap the water, organic fertilizer and microbial agent in the hydrogel, prevent the water from freezing to cause damage to the plant root system, and provide protection for the microbial agent at low temperatures to prevent inactivation. The microbial flora and nutrients are accurately released when the temperature is suitable, which not only ensures that the microbial agent safely overwinters, but also ensures efficient use of the nutrients. The freeze-thaw slow-release composite organic fertilizer is matched with the freeze-thaw period to realize accurate release and synchronization with the seasonal changes in soil.

[0031] Further, glycerol is added to the freeze-thaw slow-release composite organic fertilizer to enhance the low-temperature toughness of the fertilizer, and SiO2 aerogel is added to reduce soil heat loss and achieve anti-freezing and heat preservation.

[0032] After the soil is repaired, the soil fertility is significantly improved, the nutrients are released, the soil respiration rate is significantly enhanced, and the microbial diversity and activity are also improved, thereby providing good soil conditions for the growth of vegetation. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 Photos of the area to be repaired in the high-cold region project in Example 2 of the present application; Figure 2 The coverage of the vegetation on the wound surface after repair by using the freeze-thaw slow-release compound organic fertilizer and the compound organic fertilizer particles in Example 2 of the present application. DETAILED DESCRIPTION

[0034] The principles and characteristics of the present application are described below in combination with the drawings and specific examples, and the examples are only used to explain the present application and are not used to limit the scope of the present application.

[0035] The mining area, engineering waste dump, and area along the railway in the high-cold region are seriously damaged due to engineering construction and mining development, the soil fertility is seriously decreased, and the vegetation is sparse, which urgently needs to be repaired to restore the ecology. The present application develops a freeze-thaw slow-release compound organic fertilizer for high-cold soil repair for the soil repair of such areas, and provides a preparation method thereof and a high-cold soil repair method. The following is a specific example.

[0036] Example 1 Preparation of freeze-thaw slow-release compound organic fertilizer for high-cold soil repair 1. Preparation of microbial agent A microbial agent with the functions of nitrogen fixation, phosphorus solubilization, and promotion of organic matter degradation at low temperature (5-15℃) is prepared and activated, and specifically, Bacillus, Pseudomonas, and Flavobacterium microbial strains (cold-tolerant Bacillus (purchased from China Ocean Microbial Culture Collection Center 1A21810) with a viable count ≥8 billion / g, cold-tolerant Pseudomonas (purchased from China Typical Culture Collection Center CCTCC AB 2012401) with a viable count ≥3 billion / g, and cold-tolerant Flavobacterium (China Ocean Microbial Culture Collection Center 1A07913) with a viable count ≥5 billion / g) are used to prepare the microbial agent, and the three strains are mixed in a mass ratio of 1:1:1. The strains in the above-mentioned microbial agent have good metabolic activity in the range of 5-15℃, and their synergistic effect improves the soil mineralization rate, inhibits plant pathogenic bacteria, and improves the soil structure, and their metabolic products can promote plant growth.

[0037] Prepare 2% (w / v) brown sugar water, i.e. add 2g brown sugar to 100 mL water, stir until the brown sugar is completely dissolved, and then add the complex microbial agent to the brown sugar water. Perform aeration activation at a constant temperature of 25-30°C for 2 hours. Aeration can be performed using an aeration pump to ensure that the microbial agent is in contact with oxygen and the brown sugar water, thereby activating the activity of the microorganisms. After activation, transfer the microbial agent solution to a centrifuge and centrifuge at an appropriate speed (e.g. 3000-5000 r / min) for a certain period of time (e.g. 10-15 minutes) to precipitate the microorganisms at the bottom and remove the supernatant. Then resuspend the precipitated microbial agent with physiological saline and make up to a concentration of 10^8 CFU / mL.

[0038] 2. Preparation of complex organic fertilizer particles Use straw, sheep manure, and mushroom residue as raw materials for organic fertilizer fermentation. Crush the straw to 3-5 cm to facilitate mixing with other raw materials. Adjust the moisture content of the sheep manure to 50-60%. According to the mass ratio of 1:1:1 of straw, sheep manure (after moisture adjustment), and mushroom residue, weigh the corresponding organic fertilizer raw materials. Pour the weighed straw, sheep manure, and mushroom residue into the fermentation tank and mix thoroughly using a stirring device (e.g. a blender).

[0039] Mix the raw materials and inoculate the activated microbial agent. The concentration of the microbial agent is 1-2% of the total mass of the fertilizer. Control the fermentation starting temperature at 15-25°C for 3-5 days. Control the fermentation temperature at 5-15°C for 30-60 days until the raw materials are fully decomposed, the color is dark, and the texture is soft. Use a thermometer to monitor the fermentation temperature regularly. If the temperature is too low, use thermal insulation materials (such as a cotton blanket) or heating equipment (such as a heating rod) to raise the temperature. If the temperature is too high, use ventilation or water spraying to lower the temperature. During the fermentation process, use a turning machine to turn the raw materials every 5 days to ensure that the raw materials are fully exposed to oxygen. At the same time, use an oxygen detection device to monitor the oxygen concentration in the fermentation tank and control it at around 12%. After decomposition, dry and crush to pass a 100-mesh sieve (particle size <0.15 mm) to obtain complex organic fertilizer particles.

[0040] Mix straw, sheep manure, and mushroom residue in a ratio of 1:1:1. This ratio provides abundant organic matter and nutrients to meet the needs of microbial growth and soil remediation. Ferment at 5-15°C for 30-60 days, turn the raw materials every 5 days during the fermentation process, and control the oxygen concentration at 10-15% to promote the metabolic activity of microorganisms, fully degrade organic matter, and improve the quality and availability of organic fertilizer.

[0041] 3. Preparation of low-temperature responsive hydrogel colloids Dissolve 15 parts of chitosan in 1% (v / v) acetic acid solution, stir until it becomes a transparent viscous liquid, the concentration is generally 1-2 wt %, adjust the pH to 5.5-6. Add 18 parts of poly-N-isopropyl acrylamide (NIPAM), 12 parts of glycerol, 0.5 parts of genipin, stir at 40°C until completely dissolved. Remove oxygen for 20 min under nitrogen, add 0.5 parts of ammonium persulfate (APS), react at 60°C water bath for 3 h, and prepare a low-temperature responsive hydrogel colloid.

[0042] 4. Preparation of freeze-thaw slow-release composite organic fertilizer Add 50 parts of composite organic fertilizer particles and 4 parts of SiO2 aerogel particles to 46 parts of low-temperature responsive hydrogel colloid, stir until uniformly dispersed. Solidify at 4°C for 24 h, cut into 3-5 mm particles, freeze-dry (-40°C pre-freeze for 6 h, -50°C vacuum drying for 24 h), and obtain freeze-thaw slow-release composite organic fertilizer.

[0043] Example 2. Soil remediation in alpine regions 1. Indoor soil remediation test Select an engineering site in an alpine region as the soil collection point, and use appropriate tools (such as a shovel) to collect 0-20 cm surface soil. Place the collected soil in a clean container (such as a plastic bucket), and record the collection location, time, and other information. Pour the collected soil onto a clean floor or sieve, and manually remove obvious plant residues (such as branches and leaves) and gravel. Then sieve the soil using a 2 mm sieve to ensure that the soil particle size is relatively uniform.

[0044] Recollect the sieved soil into the container, and thoroughly mix and stir to homogenize the soil structure. Use a soil pH meter to detect the initial pH value of the soil. Prepare an appropriate amount of dilute sulfuric acid solution (concentration of 0.1-1 mol / L), and slowly and evenly spray the dilute sulfuric acid solution onto the soil while continuously stirring the soil with a shovel to ensure that the sulfuric acid and soil are in full contact. During the addition process, continuously monitor the soil pH value using a pH meter until it is adjusted to about 7.0. Use a soil moisture meter to detect the initial moisture content of the soil.

[0045] If the moisture content is low, evenly spray water onto the soil using a sprayer to increase the soil humidity; if the moisture content is too high, spread the soil in a well-ventilated place to dry, and reduce the moisture content. Finally, adjust the moisture content of the soil to 25%.

[0046] The 0-20 cm surface soil was collected for pretreatment because this layer is greatly affected by human activities and is the main distribution layer of plant roots. Removing plant residues and gravel can avoid interference with subsequent operations and microbial growth. Passing through a 2 mm sieve makes the soil particle size uniform, which is conducive to the distribution and activity of microorganisms. Adjusting the soil pH to 5.5-7.5 is because most microorganisms are more active at this pH range, which can better play a role. Controlling the soil moisture content at 20-30 % provides a suitable survival environment for microorganisms, which is conducive to the colonization of microbial agents.

[0047] Under laboratory conditions, the winter and spring freeze-thaw in alpine regions was simulated, and the pretreated soil to be repaired was used for indoor culture test. The temperature control program was -20 ℃ at night (12 h) and 8 ℃ during the day (12 h), with 1 cycle per day, for a total of 90 freeze-thaw cycles. The soil was a backfilling spoil in the engineering surface of alpine regions, with a total organic carbon content of 3 % and a total nitrogen content of 0.2 %. The experimental treatments are shown in Table 1.

[0048] Table 1

[0049] The test treatment has 3 groups, respectively freeze-thaw slow-release compound organic fertilizer treatment group A, compound organic fertilizer particle treatment group B and blank treatment group C. After 90 days of simulated freeze-thaw cycle, the soil respiration rate (CO2 release rate), total organic carbon (TOC), dissolved organic carbon (DOC), total nitrogen (TN), dissolved total nitrogen (DTN), dissolved total phosphorus (DTP), microbial diversity (16S rDNA sequencing analysis) and carbon and nitrogen related functional gene quantification analysis were determined. The results are shown in Tables 2-4: Table 2 Changes of soil nutrients and respiration rate in alpine engineering surface

[0050] After 90 days of freeze-thaw cycle, the TOC of the soil treated with freeze-thaw slow-release compound organic fertilizer was higher than that of the blank group and the compound organic fertilizer particle group, due to the combined effect of organic fertilizer contribution and water gel carbon sequestration; the DOC, DTN and DTP of the soil treated with freeze-thaw slow-release compound organic fertilizer were higher than those of the blank group and lower than those of the compound organic fertilizer group, due to the release peak of water gel slow-release organic fertilizer; the TN of the soil treated with freeze-thaw slow-release compound organic fertilizer was the highest, due to the contribution of microbial nitrogen fixation.

[0051] Compared with the blank group, the soil respiration rate of the composite organic fertilizer particle treatment group and the freeze-thaw slow-release composite organic fertilizer treatment group increased by 127% and 191%, respectively, which was significantly increased. This was because the composite organic fertilizer particles and freeze-thaw slow-release composite organic fertilizer contained microbial agents, which could improve the activity of soil microorganisms, increase the metabolic activity, increase the respiration of soil, and increase the release of CO2 in soil. The increase of microbial metabolic activity accelerated the soil material circulation and energy exchange, promoted the decomposition and transformation of organic matter in soil, and was beneficial to the recovery of soil ecological function. Further, although the release of microbial agents and organic fertilizer was slow in the freeze-thaw slow-release composite organic fertilizer treatment group, most of the microorganisms were still in the gel network and had not been released, but the soil respiration rate was 1.28 times that of the direct addition of composite organic fertilizer group, indicating that the freeze-thaw slow-release composite organic fertilizer treatment group could provide protection for microorganisms at low temperature, prevent them from inactivation, and accurately release microbial flora and nutrients at appropriate temperature, which could ensure the safety of microorganisms over winter and ensure the efficient use of nutrients.

[0052] Table 3 Change of soil microbial community diversity index in alpine region engineering construction site

[0053] Table 4 Change of soil carbon and nitrogen cycle key gene abundance in alpine region engineering construction site

[0054] Improve the microbial community structure: Introduce functional bacteria such as Bacillus, Pseudomonas and Flavobacterium, which can effectively improve the microbial community structure of alpine soil. The 16S rDNA copy number of the freeze-thaw slow-release composite organic fertilizer group increased by one order of magnitude compared with the blank group. Through 16S rDNA sequencing analysis, the Shannon index of soil microbial community in the freeze-thaw slow-release composite organic fertilizer group was 2.3 times that of the blank group and 1.6 times that of the composite organic fertilizer particle group, and the Chaos index was 1.8 times that of the blank group, mainly due to the protection of hydrogel to microhabitat and the colonization of cold-tolerant bacteria; the abundance of autotrophic carbon fixation enzyme and cellulose decomposition enzyme genes in the freeze-thaw slow-release composite organic fertilizer group increased by about 30%, and the abundance of nitrogen fixation enzyme genes increased by more than 200%. The cold shock proteinase gene in the blank group increased by 250%, the cold shock proteinase gene in the organic fertilizer group increased by 150%, and there was no significant change in the freeze-thaw slow-release composite organic fertilizer group. The blank group forced the overexpression of anti-freezing genes, and the physical shelter of the hydrogel group reduced the demand for physiological stress.

[0055] Through the monitoring and analysis of various indicators, it is found that the fertility of the laboratory cultured soil is significantly improved, the nutrients are released slowly, the soil respiration rate is obviously enhanced, and the microbial diversity is also improved, which provides good soil conditions for the growth of vegetation.

[0056] 2, on-site repair Figure 1 For the soil of the engineering wound area to be repaired in the alpine region, the freeze-thaw slow-release composite organic fertilizer is used for on-site repair. Specifically, in late autumn, suitable mechanical seeding equipment is selected, the freeze-thaw slow-release composite organic fertilizer is mixed with the soil in a mass ratio of 30:100, and is scattered to the soil surface layer of 0-10 cm. During the seeding process, the travel speed, seeding depth and seeding amount of the seeding machine are strictly controlled to ensure uniform distribution of the particles and consistent depth. After scattering, light pressing equipment is used for appropriate pressing to make the particles closely adhere to the soil. The engineering wound repair area treated with the same amount of composite organic fertilizer particles is used as a control. In the second summer, as shown in the table, the emergence rate of the plot treated with the composite freeze-thaw slow-release wrapped particles is >85%, and the emergence rate of the plot treated with the same amount of composite organic fertilizer particles is <60%. Figure 2

[0057] For some areas, some composite freeze-thaw slow-release wrapped particles are selected, which are crushed to a suitable particle size using a grinding device, and are adjusted into a suspension with a suitable concentration, which is applied through a drip irrigation system with water. Before drip irrigation, the drip irrigation equipment needs to be calibrated to ensure that the suspension can be uniformly and stably delivered into the soil.

[0058] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.​

Claims

1. A freeze-thaw slow-release compound organic fertilizer for high-cold soil remediation, characterized in that, The composite organic fertilizer particles and the low-temperature responsive hydrogel are compounded; The composite organic fertilizer particles include organic fertilizer and microbial inoculum, which are compounded with the low-temperature responsive hydrogel and wrapped in the network of the low-temperature responsive hydrogel; The LCST temperature of the low-temperature responsive hydrogel is 5-8℃, which absorbs water and swells below the LCST temperature, shrinks above the LCST temperature, and slowly releases water in the network of the hydrogel and the composite organic fertilizer particles.

2. The freeze-thaw slow-release compound organic fertilizer for high-cold soil remediation according to claim 1, characterized in that, The mass ratio of the composite organic fertilizer particles to the low-temperature responsive hydrogel is 3:7-1:

1.

3. The freeze-thaw slow-release composite organic fertilizer for high-cold soil remediation according to claim 1, characterized in that, The composite organic fertilizer particles are prepared by fermenting microbial inoculum and organic fertilizer raw materials in an environment of 5-15℃.

4. The freeze-thaw slow-release composite organic fertilizer for high-cold soil remediation according to any one of claims 1-3, characterized in that, The microbial inoculum is composed of one or more strains, which have the functions of nitrogen fixation, phosphorus solubilization and organic matter degradation in a temperature range of 5-15℃.

5. The freeze-thaw slow-release composite organic fertilizer for high-cold soil remediation according to claim 1, characterized in that, The low-temperature responsive hydrogel includes temperature-sensitive material, natural polymer hydrogel matrix, glycerol, crosslinking agent and initiator.

6. The freeze-thaw slow-release composite organic fertilizer for high-cold soil remediation according to claim 5, characterized in that, The temperature-sensitive material is N-isopropyl acrylamide, and the natural polymer hydrogel matrix is chitosan or sodium alginate.

7. The freeze-thaw slow-release composite organic fertilizer for high-cold soil remediation according to claim 5 or 6, characterized in that, The low-temperature responsive hydrogel includes the following components in mass fraction: temperature-sensitive material 15-20 parts, natural polymer hydrogel matrix 12-18 parts, glycerol 10-14 parts, crosslinking agent 0.3-0.8 parts, and initiator 0.3-0.8 parts.

8. The freeze-thaw slow-release composite organic fertilizer for high-cold soil remediation according to claim 1 or 2, characterized in that, SiO2 aerogel particles are further included, and the mass of the SiO2 aerogel particles is 2%-5% of the composite organic fertilizer particles.

9. The preparation method of freeze-thaw slow-release compound organic fertilizer for high-cold soil remediation according to any one of claims 1-8, characterized in that, The method includes the following steps: S1. Fermenting organic fertilizer raw materials and microbial inoculum in an environment of 5-15℃ to obtain composite organic fertilizer, and preparing the composite organic fertilizer into composite organic fertilizer particles; S2. Preparing low-temperature responsive hydrogel colloid; S3. Adding the composite organic fertilizer particles into the low-temperature responsive hydrogel colloid, mixing uniformly, solidifying, crushing, freeze-drying to obtain the freeze-thaw slow-release composite organic fertilizer for high-cold soil remediation.

10. A method for remediation of cold soils, characterized in that, The freeze-thaw slow-release composite organic fertilizer for high-cold soil remediation of any one of claims 1-8 is applied to the surface layer of 0-10cm of soil in high-cold areas in late autumn or early winter, or is formulated into a suspension for application through a drip irrigation system.

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