Multifunctional soil conditioner for forestry ecological restoration and preparation method thereof

Abstract

The application discloses a multifunctional soil modifier for forestry ecological restoration and a preparation method thereof, and belongs to the technical field of forestry ecological restoration.The modified biochar is prepared by loading iron-manganese oxides on pine sawdust as raw material after phosphoric acid activation; the rotten agricultural and forestry waste is a compost product of poplar branches and legume straw in a specific ratio; the mineral composite powder comprises a specific compound of bentonite, glauconite and phosphogypsum; the microbial agent is composed of bacillus subtilis, gelatinous-like bacillus and arbuscular mycorrhizal fungi; and the slow-release nutrient particles are obtained by embedding nitrogen, phosphorus, potassium and trace elements with sodium alginate as wall material.The preparation method comprises the steps of raw material pretreatment, step-by-step mixing, granulation and post-treatment.The application realizes the multiple functions of soil structure improvement, nutrient slow release, heavy metal passivation and vegetation promotion through the synergistic effect of various components, is especially suitable for the ecological restoration of degraded forest land in the southern acid red soil area, and has the characteristics of long-term stability, environmental friendliness and simple preparation process.

Description

Technical Field

[0001] This invention belongs to the field of forestry ecological restoration technology, and specifically relates to a multifunctional soil conditioner for forestry ecological restoration and its preparation method. Background Technology

[0002] The red soil region in southern my country covers an area of ​​approximately 2.18 million square kilometers, of which forest land accounts for more than 40%, making it an important forestry production base and ecological barrier. However, long-term irrational management has led to widespread problems in this region, including aggravated soil acidification (pH value dropping to 4.0-5.5), organic matter deficiency (content <1.5%), destruction of aggregate structure (aggregates >0.25mm account for <40%), and increased heavy metal activity (available cadmium and lead exceed the standard rate by more than 30%), which seriously restricts the growth of trees and the functioning of ecological functions.

[0003] Existing soil amendment technologies have the following limitations: applying lime alone to adjust pH can easily lead to soil compaction and cannot improve nutrient status; while ordinary organic fertilizers can increase organic matter, their passivation effect on heavy metals is limited; chemical amendments can easily cause secondary pollution; biochar applications focus primarily on adsorption performance and lack synergistic design with microorganisms and nutrients. Furthermore, traditional amendments have limited functionality, making it difficult to simultaneously meet the multiple needs of structural improvement, nutrient supply, and pollution remediation. They also suffer from short-lasting effects (usually <6 months), complex preparation processes, and high costs, making them unsuitable for large-scale forestry ecological restoration projects.

[0004] In recent years, although some research has attempted to develop composite soil conditioners, problems still exist regarding the unreasonable combination of components. For example, existing technologies do not consider the specific adsorption of heavy metals by biochar surface modification, and the survival rate of microorganisms is low; the mineral composite formulations used in existing technologies lack synergy with organic components, resulting in asynchronous nutrient release. Therefore, there is an urgent need to develop a forestry-specific soil conditioner with synergistic components, multiple functions, and long-lasting stability to address the shortcomings of existing technologies. Summary of the Invention

[0005] In view of this, the present invention provides a multifunctional soil conditioner for forestry ecological restoration and its preparation method, so as to solve or alleviate one of the technical problems existing in the prior art, and at least provide a beneficial option.

[0006] The technical solution of this invention is implemented as follows: A multifunctional soil conditioner for forestry ecological restoration is prepared from the following raw materials in parts by weight: 35-45 parts modified biochar, 20-30 parts decomposed agricultural and forestry waste, 15-25 parts mineral composite powder, 5-10 parts microbial inoculant, and 8-12 parts slow-release nutrient granules. The modified biochar is prepared as follows: pine sawdust is dried at 105℃ to constant weight, pulverized and passed through a 60-mesh sieve, and mixed with a 20% phosphoric acid solution at a solid-liquid ratio of 1:3. After soaking at room temperature for 4 hours, it is stirred in an 80℃ water bath until the water evaporates. The mixture is then transferred to a muffle furnace and carbonized for 2 hours at 500℃ under nitrogen protection at a rate of 10℃ / min. After cooling, it is washed until neutral and then impregnated in a 0.5mol / L solution. and Modified biochar was prepared by ultrasonic dispersion for 30 min in a mixed solution (Fe:Mn molar ratio = 2:1), drying at 80℃, and calcining at 300℃ for 1 h. The decomposed agricultural and forestry waste is made by mixing poplar branches and soybean straw at a dry weight ratio of 7:3, adjusting the carbon-nitrogen ratio to 25:1, and the moisture content to 60%. It is inoculated with high-temperature cellulose-degrading bacteria and composted aerobically at 55-65℃ for 28 days, turning the pile every 7 days. After the composting is completed, it is aged for 15 days. The mineral composite powder is made by grinding and mixing bentonite, glauconite and phosphogypsum in a mass ratio of 5:3:2 and passing it through a 200-mesh sieve. The microbial agent is a compound of Bacillus subtilis, Bacillus colloidis and arbuscular mycorrhizal fungi in a live count ratio of 3:2:1, and the agent carrier is diatomaceous earth. The wall material of the slow-release nutrient granules is sodium alginate, and the core material is a mixture of urea, potassium dihydrogen phosphate, potassium sulfate and zinc sulfate heptahydrate. The mass ratio of core material to wall material is 5:1. The granules are prepared into particles with a diameter of 2-3 mm by emulsification crosslinking method.

[0007] Preferably, the modified biochar has a specific surface area of ​​450-550 m² / g, a total pore volume of 0.35-0.45 cm³ / g, and a surface Fe-Mn oxide loading of 8-12 wt%. The organic matter content of the decomposed agricultural and forestry waste is 65-75 wt%, the humic acid content is 25-30 wt%, and the pH value is 7.2-7.8; The mineral composite powder has a cation exchange capacity of 45-55 cmol / kg and a montmorillonite content of 55-65 wt%. The total number of viable bacteria in the microbial agent is 2 × 10¹. 0 -5×10¹ 0 CFU / g; the total nitrogen, phosphorus and potassium content of the slow-release nutrient granules is 35-40wt%, the zinc content is 0.8-1.2wt%, and the cumulative release rate over 28 days is 55-65%.

[0008] Preferably, the inoculum amount of the high-temperature cellulose-degrading microbial agent is 0.3-0.5% of the dry weight of the compost raw material, and the microbial agent contains a composite spore powder of Trichoderma reesei and Trichoderma viride, with a spore germination rate of ≥90%.

[0009] Preferably, the preparation of the sustained-release nutrient granules specifically involves: mixing urea, potassium dihydrogen phosphate, potassium sulfate, and zinc sulfate heptahydrate in a specific ratio. The mixtures were homogeneous at a mass ratio of 15:10:12:1. Sodium carboxymethyl cellulose (5% by mass of the core material) was added as a binder, and the mixture was granulated into core material particles of 1-1.5 mm. Sodium alginate was dissolved in deionized water to prepare a 2% (w / w) solution, which was then added to the core material particles. After stirring evenly, the solution was added dropwise to a 2% (w / w) calcium chloride solution. The mixture was cross-linked and cured for 30 min, filtered, washed, and dried at 40°C until the moisture content was ≤8%, thus obtaining the slow-release nutrient granules.

[0010] Preferably, the raw material also includes 0.5-1% of triammonium citrate by mass of the modified biochar, which is used to adjust the loading morphology of metal oxides during the preparation of modified biochar.

[0011] Preferably, the following steps are included: S1: Raw material pretreatment: Weigh each raw material according to the ratio, crush the modified biochar, decomposed agricultural and forestry waste, and mineral composite powder into 80 mesh sieves, premix the microbial agent and diatomaceous earth carrier at a mass ratio of 1:3, and place the slow-release nutrient granules in a sterile environment for later use. S2: Stepwise mixing: First, put the modified biochar and mineral composite powder into a double cone rotary mixer and mix at 30 r / min for 15 min. Then add the decomposed agricultural and forestry waste and mix at 45 r / min for 20 min. Finally, add the microbial agent and slow-release nutrient granules and mix at 20 r / min for 10 min to obtain the mixture. S3: Granulation: The mixture is fed into a ring die granulator and granules with a diameter of 5-8 mm are produced under the conditions of a die compression ratio of 1:5 and a ring die speed of 250 r / min. S4: Post-processing: The granulated granules are dried with hot air at 45℃ until the moisture content is ≤10%, cooled to room temperature and then packaged to obtain the finished product.

[0012] Preferably, in step S2, the ambient temperature is controlled to be ≤30℃ and the relative humidity to be ≤50% during the mixing process, and sterile air is introduced into the mixer to maintain a slight positive pressure.

[0013] Preferably, in step S3, 0.5% by mass of food-grade calcium stearate is added to the mixture as a lubricant before granulation to reduce ring die wear.

[0014] Preferably, in step S4, the dried granules are packaged in a double layer, with an inner layer of polyethylene film bag and an outer layer of aluminum foil composite bag, and are stored in a nitrogen-filled and sealed container.

[0015] Preferably, the amendment is suitable for acidic degraded forest soil with a pH of 4.5-6.0, and the application rate is 150-300 kg / mu, applied by trenching or hole application, with an application depth of 20-30 cm, matching the distribution layer of the tree root system.

[0016] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions: (1) Significant synergistic effect of components: Modified biochar forms specific adsorption sites through Fe-Mn oxide loading, which enhances the adsorption capacity of the modified biochar. , The adsorption capacity reaches 45-55 mg / g, which is more than 120% higher than that of unmodified biochar; the decomposed agricultural and forestry waste provides humus to promote the formation of aggregate structure, and synergistically with mineral composite powder to increase the cation exchange capacity to 35-45 cmol / kg; under the protection of the amendment carrier, the soil colonization survival rate of microbial agents is increased by 3-5 times, effectively promoting the absorption of phosphorus and zinc by forest roots; the slow-release nutrient granules realize the release of nutrients on demand, and the cumulative release rate is controlled at 55-65% in 28 days, avoiding leaching loss.

[0017] (2) High integration of multiple functions: A single application can simultaneously increase pH value by 0.8-1.5 units, increase organic matter by 1.2-1.8 percentage points, increase the proportion of aggregates >0.25mm by 25-35%, reduce available heavy metals by 40-60%, and increase the survival rate of trees by 20-30%. The comprehensive improvement effect is better than the superposition of single measures.

[0018] (3) Excellent long-term stability: The aromatic structure of modified biochar makes its half-life in soil >5 years, the interlayer fixation of mineral composite powder delays nutrient release, and the carrier protection of microbial agents extends its functional duration to more than 18 months. The overall improvement effect can be maintained for 3-5 years, reducing the number of repeated applications.

[0019] (4) Strong environmental friendliness: All raw materials are derived from agricultural and forestry waste or natural minerals, with no chemically synthesized additives. The preparation process has no wastewater or waste gas emissions. After being applied to the soil, it can be completely degraded and will not cause secondary pollution.

[0020] (5) The preparation process is simple and feasible: large-scale production can be achieved using conventional equipment, with low energy consumption (electricity consumption per ton of product ≤ 80 kW·h) and raw material cost controlled at 1200-1500 yuan / ton, making it suitable for large-scale forestry engineering applications.

[0021] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the invention will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a flowchart illustrating the preparation process of the modified biochar of this invention. Figure 2 This is a flowchart illustrating the preparation process of composted agricultural and forestry waste according to the present invention. Detailed Implementation

[0024] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0025] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0026] Example 1

[0027] 1. Raw material preparation

[0028] 2. Preparation process: (1) Preparation of modified biochar: Pine sawdust was dried at 105℃ for 24h, pulverized and passed through a 60-mesh sieve, mixed with 20% phosphoric acid solution at a solid-liquid ratio of 1:3, soaked at room temperature for 4h, stirred in an 80℃ water bath until nearly dry, carbonized at 500℃ for 2h under nitrogen protection, cooled and washed with water until neutral, and impregnated in 0.5mol / L - In a solution (Fe:Mn=2:1), it was sonicated for 30 min, dried at 80℃, and then calcined at 300℃ for 1 h.

[0029] (2) Preparation of decomposed agricultural and forestry waste: Poplar branches and soybean straw are crushed to 2-3cm, mixed at a dry weight ratio of 7:3, C / N=25:1, moisture content 60%, inoculated with 0.4% high temperature cellulose degradation agent (Trichoderma reesei + Trichoderma viride, spore germination rate 95%), aerobic composting at 55-65℃ for 28 days, turning the pile every 7 days, and aging for 15 days.

[0030] (3) Preparation of mineral composite powder: Bentonite, glauconite and phosphogypsum were ground through a 200-mesh sieve and mixed evenly in a mass ratio of 5:3:2.

[0031] (4) Preparation of microbial inoculants: The three strains were fermented and cultured to the logarithmic growth phase, mixed in a ratio of 3:2:1 for viable bacteria, and adsorbed with sterilized diatomaceous earth carrier at a mass ratio of 1:3. The mixture was then freeze-dried under vacuum until the moisture content was ≤5%.

[0032] (5) Preparation of slow-release nutrient granules: urea, potassium dihydrogen phosphate, potassium sulfate, and zinc sulfate heptahydrate are mixed according to... Mix the components in a 15:10:12:1 ratio, add 5% sodium carboxymethyl cellulose binder to granulate (1-1.5 mm), add the granules to a 2% sodium alginate solution, and then add the mixture dropwise to a 2% calcium chloride solution for cross-linking and curing for 30 min. Filter, wash, and dry at 40℃ until the moisture content is ≤8%.

[0033] (6) Preparation of finished product: Weigh each raw material according to the ratio, mix the modified biochar and mineral composite powder for 15 min (30 r / min), add the decomposed agricultural and forestry waste and mix for 20 min (45 r / min), and finally add the microbial agent and slow-release nutrient granules and mix for 10 min (20 r / min). Grind the mixture into 5-8 mm particles by ring die granulation (compression ratio 1:5, rotation speed 250 r / min), dry at 45℃ until the moisture content is ≤10%, and package in double layer.

[0034] 3. Performance Testing

[0035] Example 2

[0036] 1. Raw material preparation

[0037] 2. The preparation process is the same as in Example 1, except for the following adjustments: In the preparation of modified biochar, the concentration of phosphoric acid solution was adjusted to 18%, and the carbonization temperature was 480℃; The composting temperature of well-rotted agricultural and forestry waste should be controlled at 50-60℃, and the composting time should be shortened to 25 days. N in the core material of slow-release nutrient granules: : : Adjusted to 14:9:11:0.9; In the mixing process, the mixing time in the first step is extended to 18 minutes, and the mixing speed in the second step is reduced to 40 r / min.

[0038] 3. Performance Testing

[0039] Example 3

[0040] 1. Raw material preparation

[0041] 2. The preparation process is the same as in Example 1, except for the following adjustments: In the preparation of modified biochar, - The solution concentration was adjusted to 0.6 mol / L, and the calcination temperature was 320℃; The inoculum amount of well-rotted agricultural and forestry waste was increased to 0.5%, and 0.2% superphosphate was added to adjust the pH. In the core material of slow-release nutrient granules Adjusted to 16:11:13:1.1; In the granulation process, the die compression ratio is adjusted to 1:6, and the ring die rotation speed is 220 r / min.

[0042] 3. Performance Testing

[0043] Field trial results

[0044] An application trial was conducted in degraded Masson pine forests in southern Jiangxi Province. The basic physicochemical properties of the soil in the experimental area were: pH 4.8, organic matter 1.2%, available nitrogen 45 mg / kg, available phosphorus 5.2 mg / kg, available potassium 68 mg / kg, and available Cd 0.68 mg / kg. Three treatments were set up: CK (no fertilizer), T1 (ordinary organic fertilizer, 300 kg / mu), and T2 (amendment from Example 1 of this invention, 200 kg / mu), with each treatment replicated three times in a randomized block design. The results were measured 12 months after application as follows:

[0045] The results show that the modifier of this invention is significantly better than ordinary organic fertilizer in all indicators at a lower application rate, especially in terms of passivation of heavy metals and promotion of tree growth, and has significant application value in forestry ecological restoration.

[0046] All raw materials not mentioned in this invention are commercially available conventional products, and all test methods not detailed are standard methods known in the art. The embodiments are merely preferred solutions; in actual production, the raw material ratios can be adjusted according to specific soil conditions, but must not exceed the scope of protection of the claims.

[0047] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multifunctional soil conditioner for forestry ecological restoration, characterized in that, It is prepared from the following raw materials in parts by weight: Modified biochar 35-45 parts, decomposed agricultural and forestry waste 20-30 parts, mineral composite powder 15-25 parts, microbial inoculant 5-10 parts, slow-release nutrient granules 8-12 parts. The modified biochar is prepared as follows: pine sawdust is dried at 105℃ to constant weight, pulverized and passed through a 60-mesh sieve, and mixed with a 20% phosphoric acid solution at a solid-liquid ratio of 1:

3. After soaking at room temperature for 4 hours, it is stirred in an 80℃ water bath until the water evaporates. The mixture is then transferred to a muffle furnace and carbonized for 2 hours at 500℃ under nitrogen protection at a rate of 10℃ / min. After cooling, it is washed until neutral and then impregnated in a 0.5mol / L solution. and Modified biochar was prepared by ultrasonic dispersion for 30 min in a mixed solution (Fe:Mn molar ratio = 2:1), drying at 80℃, and calcining at 300℃ for 1 h. The decomposed agricultural and forestry waste is made by mixing poplar branches and soybean straw at a dry weight ratio of 7:3, adjusting the carbon-nitrogen ratio to 25:1, and the moisture content to 60%. It is inoculated with high-temperature cellulose-degrading bacteria and composted aerobically at 55-65℃ for 28 days, turning the pile every 7 days. After the composting is completed, it is aged for 15 days. The mineral composite powder is made by grinding and mixing bentonite, glauconite and phosphogypsum in a mass ratio of 5:3:2 and passing it through a 200-mesh sieve. The microbial agent is a compound of Bacillus subtilis, Bacillus colloidis and arbuscular mycorrhizal fungi in a live count ratio of 3:2:1, and the agent carrier is diatomaceous earth. The wall material of the slow-release nutrient granules is sodium alginate, and the core material is a mixture of urea, potassium dihydrogen phosphate, potassium sulfate and zinc sulfate heptahydrate. The mass ratio of core material to wall material is 5:

1. The granules are prepared into particles with a diameter of 2-3 mm by emulsification crosslinking method.

2. The multifunctional soil conditioner for forestry ecological restoration according to claim 1, characterized in that, The modified biochar has a specific surface area of ​​450-550 m² / g, a total pore volume of 0.35-0.45 cm³ / g, and a surface Fe-Mn oxide loading of 8-12 wt%. The organic matter content of the decomposed agricultural and forestry waste is 65-75 wt%, the humic acid content is 25-30 wt%, and the pH value is 7.2-7.8; The mineral composite powder has a cation exchange capacity of 45-55 cmol / kg and a montmorillonite content of 55-65 wt%. The total number of viable bacteria in the microbial agent is 2 × 10¹. 0 -5×10¹ 0 CFU / g; the total nitrogen, phosphorus and potassium content of the slow-release nutrient granules is 35-40wt%, the zinc content is 0.8-1.2wt%, and the cumulative release rate over 28 days is 55-65%.

3. The multifunctional soil conditioner for forestry ecological restoration according to claim 1, characterized in that, The inoculum amount of the high-temperature cellulose-degrading microbial agent is 0.3-0.5% of the dry weight of the compost raw material. The microbial agent contains a compound spore powder of Trichoderma reesei and Trichoderma viride, with a spore germination rate of ≥90%.

4. The multifunctional soil conditioner for forestry ecological restoration according to claim 1, characterized in that, The preparation of the sustained-release nutrient granules specifically involves: mixing urea, potassium dihydrogen phosphate, potassium sulfate, and zinc sulfate heptahydrate in the following manner... The mixtures were homogeneous at a mass ratio of 15:10:12:

1. Sodium carboxymethyl cellulose (5% by mass of the core material) was added as a binder, and the mixture was granulated into core material particles of 1-1.5 mm. Sodium alginate was dissolved in deionized water to prepare a 2% (w / w) solution, which was then added to the core material particles. After stirring evenly, the solution was added dropwise to a 2% (w / w) calcium chloride solution. The mixture was cross-linked and cured for 30 min, filtered, washed, and dried at 40°C until the moisture content was ≤8%, thus obtaining the slow-release nutrient granules.

5. The multifunctional soil conditioner for forestry ecological restoration according to claim 1, characterized in that, The raw materials also include 0.5-1% of triammonium citrate by mass of the modified biochar, which is used to adjust the loading morphology of metal oxides during the preparation of modified biochar.

6. The method for preparing the multifunctional soil conditioner for forestry ecological restoration according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Raw material pretreatment: Weigh each raw material according to the ratio, crush the modified biochar, decomposed agricultural and forestry waste, and mineral composite powder into 80 mesh sieves, premix the microbial agent and diatomaceous earth carrier at a mass ratio of 1:3, and place the slow-release nutrient granules in a sterile environment for later use. S2: Stepwise mixing: First, put the modified biochar and mineral composite powder into a double cone rotary mixer and mix at 30 r / min for 15 min. Then add the decomposed agricultural and forestry waste and mix at 45 r / min for 20 min. Finally, add the microbial agent and slow-release nutrient granules and mix at 20 r / min for 10 min to obtain the mixture. S3: Granulation: The mixture is fed into a ring die granulator and granules with a diameter of 5-8 mm are produced under the conditions of a die compression ratio of 1:5 and a ring die rotation speed of 250 r / min. S4: Post-processing: The granulated granules are dried with hot air at 45℃ until the moisture content is ≤10%, cooled to room temperature and then packaged to obtain the finished product.

7. The preparation method according to claim 6, characterized in that, In step S2, the ambient temperature is controlled to be ≤30℃ and the relative humidity to be ≤50% during the mixing process, and sterile air is introduced into the mixer to maintain a slight positive pressure.

8. The preparation method according to claim 6, characterized in that, In step S3, 0.5% by weight of food-grade calcium stearate is added to the mixture as a lubricant before granulation to reduce ring die wear.

9. The preparation method according to claim 6, characterized in that, In step S4, the dried granules are packaged in a double layer: an inner polyethylene film bag and an outer aluminum foil composite bag, and then sealed with nitrogen.

10. The multifunctional soil conditioner for forestry ecological restoration according to claim 1, characterized in that, The amendment is suitable for acidic degraded forest soil with a pH of 4.5-6.

0. The application rate is 150-300 kg / mu, applied by trenching or hole application at a depth of 20-30 cm, matching the distribution layer of the tree root system.

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