Multifunctional composite soil conditioner as well as preparation and application thereof

Abstract

The invention provides a novel soil conditioner as well as a preparation method and an application method thereof, aiming at solving the problems of single function, difficulty in coping with soil heavy metal pollution, nutrient loss, insufficient microbial activity and the like at the same time, and the defects of poor effect persistence, environmental risk and the like of the existing soil conditioner. According to the modifier, multiple effective components are creatively fused, and multiple effects are achieved. The soil conditioner not only can improve the physical structure of soil and adjust the pH value, but also can efficiently fix heavy metals and prevent secondary release of the heavy metals from harming crops and the environment; through special formula design, the decomposition speed of organic materials is effectively slowed down, the lasting time of the improvement effect is prolonged, and the application frequency is reduced; meanwhile, soil microorganism breeding and activity improvement are actively promoted, and the stability of a soil ecological system is enhanced. The preparation method disclosed by the invention is simple and easy to implement and relatively low in cost, and the prepared soil conditioner is environment-friendly and pollution-free, can be widely applied to remediation and improvement of various polluted and degraded soil, and provides powerful technical support for guaranteeing agricultural sustainable development and ecological environment safety.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of soil improvement, and specifically relates to a multifunctional composite soil improver as well as a preparation method and application thereof, which is suitable for the remediation and improvement of saline-alkali soil, heavy metal contaminated soil, infertile soil and degraded soil, and simultaneously has the functions of water retention, nutrient slow release, bacteriostasis and plant growth promotion. BACKGROUND

[0002] Soil, as the foundation of agricultural production and an important component of the ecological system, its quality is directly related to the yield and quality of crops, as well as the stability and health of the ecological environment. However, with the rapid advancement of industrialization, the continuous improvement of agricultural intensification, and the long-term unreasonable land use mode, soil is facing many severe problems, and soil degradation is becoming increasingly serious, which poses a great threat to global food security and ecological balance. Under this background, the research and application of soil improvers have become a key means to solve soil problems, but there are still many bottlenecks to be broken through in the existing technology.

[0003] 1. Existing technical problems

[0004] (1) Single function: Traditional soil improvers are numerous, such as lime, which is mainly used to adjust the acid-base value of acidic soil, to improve the soil pH value by neutralizing acidic substances in the soil, to create a suitable environment for crop growth; humic acid can improve the physical structure of soil and enhance the water and fertilizer retention capacity of soil; polyacrylamide focuses on improving the stability of soil aggregates and reducing soil erosion. However, these improvers have relatively single functions, and can only improve certain aspects of soil problems. In the actual situation of soil degradation, soil often has multiple problems such as heavy metal pollution, nutrient loss and insufficient microbial activity. For example, industrial waste discharge leads to excessive heavy metals in soil, which inhibits crop growth and poses potential harm to human health; unreasonable fertilization and irrigation methods cause nutrient loss, resulting in soil fertility decline; and long-term single crop planting and large-scale use of chemical pesticides also destroy the balance of soil microbial community and reduce microbial activity. The existing single-function improvers cannot simultaneously address these complex problems, and it is difficult to achieve comprehensive remediation and sustainable use of soil.

[0005] (2) Effect persistence is poor: Organic materials such as straw, livestock and poultry manure, etc. are rich in organic matter and nutrients, and are widely used in soil improvement. They can increase soil organic matter content, improve soil structure, provide carbon source and energy for microorganisms, thereby promoting the growth and reproduction of microorganisms. However, these organic materials are easily decomposed by microorganisms in the soil. In warm and humid environmental conditions, microorganisms are active, and organic materials may be decomposed in a short time, making it difficult to maintain the improvement effect. In order to maintain the improved state of the soil, it is necessary to frequently apply organic materials, which not only increases the cost of agricultural production, but also may cause soil nutrient imbalance and environmental pollution due to excessive application.

[0006] (3) Environmental risk: Chemical modifiers such as phosphates and sulfides are used to fix heavy metals in the soil in some cases, reducing their bioavailability. However, these chemicals may undergo a series of complex chemical reactions in the soil, causing secondary pollution. For example, the precipitate formed by the reaction of phosphate with heavy metal ions may re-dissolve under certain conditions, causing the release of heavy metals into the soil environment. In addition, biochar, as a new type of soil improvement material, has the advantages of adsorbing heavy metals and improving soil structure, but its preparation cost is high, and it mainly focuses on physical adsorption, and has limited effect on soil microbial activity and nutrient cycling, making it difficult to meet the needs of comprehensive soil improvement. SUMMARY

[0007] The present application aims to provide a multifunctional, long-acting and environmentally friendly soil conditioner that can simultaneously improve soil physical structure, adjust pH, effectively fix heavy metals, reduce nutrient loss, enhance microbial activity, achieve comprehensive repair and sustainable improvement of soil, reduce improvement cost, avoid secondary pollution, and ensure the healthy development of agricultural production and ecological environment.

[0008] To achieve the above-mentioned purpose, the present application realizes the following technical solutions:

[0009] A multifunctional composite soil conditioner, comprising the following components in mass percentage:

[0010] Functional components:

[0011] Straw powder 20%-50%;

[0012] Bentonite 10%-30%;

[0013] Fly ash 10%-30%;

[0014] Lignin 5%-15%;

[0015] Synergistic components:

[0016] Water-soluble high molecular compound 5%-10%;

[0017] Modified montmorillonite 5% - 15%;

[0018] Microcapsules of bactericidal essential oil 1% - 5%;

[0019] Auxiliary components:

[0020] Activated carbon 3% - 8%.

[0021] Further, the microcapsules of bactericidal essential oil are prepared by the following method:

[0022] (1) Dissolve the essential oil of Litsea cubeba or Litsea rotundifolia in toluene-2, 4-diisocyanate in toluene to form an oil phase;

[0023] (2) Dissolve the polyethylene glycol emulsifier in deionized water to form an aqueous phase;

[0024] (3) Mix the oil phase with the aqueous phase, add the initiator potassium persulfate, and polymerize in a constant temperature water bath at 50°C for 2 hours to form slow-release polymer microcapsules;

[0025] (4) After washing, suction filtering and drying, the bactericidal essential oil microcapsules with nanoscale particle size are obtained.

[0026] Further, the water-soluble high molecular compound is guar gum or modified starch with a molecular weight range of 50000-500000 Da, which is used to enhance the stability of soil aggregate structure and the cohesiveness of the amendment.

[0027] Further, the modified montmorillonite is sodium-based or organically modified montmorillonite with an interlayer cation exchange capacity ≥80 cmol / kg, which is used to adjust the soil pH and achieve slow and controlled release of water.

[0028] A preparation method of a multifunctional composite soil amendment, comprising the following steps:

[0029] (1) Straw powder preparation: crush corn straw, wheat straw or soybean straw, and pass through a 50-100 mesh sieve to obtain straw powder;

[0030] (2) Mixed slurry preparation: mix the straw powder, bentonite, lignin, fly ash, water-soluble high molecular compound and water according to the mass ratio, stir until uniform, and control the slurry solid content at 10%-40%;

[0031] (3) Microcapsule compounding: add the microcapsules of bactericidal essential oil and activated carbon according to the mass ratio of 1:0.05-0.08 to the mixed slurry, and stir uniformly;

[0032] (4) Spray drying: spray dry the mixed slurry, with an inlet temperature of 350-450°C and an outlet temperature of 200-300°C;

[0033] (5) Post-processing: Dry the dried product at 80-150°C for 1-10 hours, crush it and sieve it to obtain a finished improver with a particle size of ≤2 mm.

[0034] Furthermore, in the spray drying step, the feed rate is 5-20 L / h and the atomization pressure is 0.2-0.8 MPa, ensuring that the modifying agent particles are uniform and the moisture content is ≤5%.

[0035] Furthermore, a multifunctional composite soil conditioner is used in the following scenarios:

[0036] (1) Improvement of saline-alkali land: reduce soil pH and salinity, improve soil structure, and increase crop yields;

[0037] (2) Remediation of heavy metal contaminated soil: fixation of heavy metals in the soil, including cadmium, lead or arsenic, and reduction of their bioavailability;

[0038] (3) Water conservation in arid areas: increase soil water storage, achieve slow release of water, and extend the drought resistance period of crops;

[0039] (4) Soil-borne disease prevention and control: Slow-release microcapsules of bactericidal essential oils can be used to inhibit the pathogens of Fusarium and Rhizoctonia solani, thereby reducing the incidence of crop diseases.

[0040] Further,

[0041] In the improvement of saline-alkali land, the application rate of the improver is 30-50 kg / mu. After application, the soil pH is reduced by 0.5-1.2 units and the salt content is reduced by 30%-60%.

[0042] In the remediation of heavy metal pollution, the application rate of the modifier is 5-15kg / hm 2 , the effective content of heavy metals in the soil is reduced by 40%-70%;

[0043] To conserve water in arid areas, the application rate of the amendment is 20-40 kg / mu, the soil water storage capacity increases by 20%-50%, and the water release period reaches 90-150 days.

[0044] Beneficial effects of the present invention:

[0045] (1) Multifunctional collaboration:

[0046] Physical improvement: Bentonite and straw powder form water-stable aggregates, reducing soil bulk density and improving air permeability;

[0047] Chemical remediation: Aluminosilicates in fly ash fix heavy metals (such as Cd and Pb), and modified montmorillonite adjusts pH;

[0048] Biological promotion: Lignin and high molecular compounds provide carbon sources for microorganisms, and bactericidal essential oils inhibit pathogens.

[0049] (2) Long-acting:

[0050] Straw powder and lignin slowly decompose, continuously release organic matter, and the effective period is more than 2 years;

[0051] Microcapsule technology realizes slow release of bactericidal components, and maintains the soil bacteriostatic environment for 6-12 months.

[0052] (3) Environmental protection and economy:

[0053] The raw materials are mainly agricultural waste (straw, fly ash), and the cost is reduced by 40%-60%;

[0054] No chemical synthetic additives, avoid secondary pollution. DETAILED DESCRIPTION

[0055] The preparation method and application effect of the multifunctional composite soil conditioner are described in detail in combination with specific embodiments, but the protection scope of the present application is not limited to the following embodiments.

[0056] I. Raw materials and reagents

[0057]

[0058] II. Preparation method examples

[0059] Example 1:

[0060] Preparation of bactericidal essential oil microcapsules

[0061] Oil phase preparation:

[0062] Take 10g of piper methysticum essential oil and 5g of TDI, add 20mL of toluene, ultrasonic dissolution (power 200W, time 5min), and form a uniform oil phase.

[0063] Water phase preparation:

[0064] Take 3g of PEG-400, dissolve in 50mL of deionized water, stir until completely dissolved, and form a water phase.

[0065] Emulsion polymerization:

[0066] Slowly drop the oil phase into the water phase, stir at 800rpm for 30min, and form a stable emulsion;

[0067] Add 0.5g of potassium persulfate, heat to 50℃, and react in a constant temperature water bath for 2h to form a polymer microcapsule suspension.

[0068] Post-processing:

[0069] The suspension was centrifuged (4000 rpm, 10 min), the supernatant was discarded, the precipitate was washed with ethanol for 3 times, and dried at 60°C under vacuum for 6 h to obtain the microcapsules of bactericidal essential oil with particle size of 200-500 nm (yield 85%).

[0070] Example 2:

[0071] Preparation of multifunctional composite soil conditioner

[0072] Pre-treatment of straw powder:

[0073] The corn straw was crushed and passed through an 80-mesh sieve, and dried at 105°C to constant weight to obtain straw powder with water content of ≤8%.

[0074] Preparation of mixed slurry:

[0075] 30 kg of straw powder, 20 kg of bentonite, 15 kg of fly ash, 10 kg of lignin, and 8 kg of guar gum were weighed according to the mass ratio, added with 50 L of water, and stirred at high speed (1500 rpm) for 30 min to form a uniform slurry (solid content 35%).

[0076] Microcapsule complexation:

[0077] 3 kg of the microcapsules of bactericidal essential oil prepared in Example 1 and 5 kg of activated carbon were added to the slurry, and stirring was continued for 15 min until the mixture was uniform.

[0078] Spray drying:

[0079] The slurry was pumped into a spray drying tower (inlet temperature 400°C, outlet temperature 220°C, feed rate 15 L / h, atomization pressure 0.5 MPa) to obtain dry particles with particle size of 1-2 mm.

[0080] Finished product treatment:

[0081] The particles were dried at 120°C for 2 h, crushed and passed through a 40-mesh sieve, and sealed and packaged to obtain the finished product of the conditioner (water content ≤4%).

[0082] III. Application Examples

[0083] Example 3:

[0084] Saline-alkali soil improvement test

[0085] Test site: saline-alkali soil in a city of Shandong Province (pH 8.5, salt content 0.6%, organic matter content 0.8%).

[0086] Test design:

[0087] Three treatment groups were set: control group (no conditioner applied), low-dose group (30 kg / acre), and high-dose group (50 kg / acre), with 3 replicates for each group.

[0088] Application method:

[0089] The amendment is evenly applied to the surface of the soil, with a plowing depth of 20 cm and a soil moisture content of 60%-70%.

[0090] Effect monitoring:

[0091] After 6 months of application, the soil pH in the low-dose group decreased to 8.0, and the salt content decreased to 0.4%; the pH in the high-dose group decreased to 7.7, and the salt content decreased to 0.3%;

[0092] The corn plant height increased by 12%-18% compared with the control group, and the yield increased by 15%-22% (Table 1).

[0093] Table 1 Improvement effect of saline-alkali soil (after 6 months of application)

[0094]

[0095] Example 4:

[0096] Heavy metal contaminated soil remediation test

[0097] Test site: A cadmium-contaminated paddy field in Hunan Province (Cd content 7.23 mg / kg, pH 5.8).

[0098] Test design:

[0099] Two treatment groups were set up: control group (no amendment), amendment group (10 kg / hm 2 ), with 3 replicates for each group.

[0100] Application method:

[0101] The amendment was mixed with the soil at a mass ratio of 1:20, plowing depth 15 cm, and flooded cultivation for 30 days.

[0102] Effect monitoring:

[0103] After remediation, the effective cadmium content of the soil decreased to 2.78 mg / kg (61.6% reduction), and the cadmium content of the rice grain decreased from 1.23 mg / kg to 0.72 mg / kg (40.7% reduction), meeting the GB 2762-2022 standard (≤0.2 mg / kg for further safe use).

[0104] Example 5:

[0105] Drought area water retention test

[0106] Test site: A drought area in a city in Gansu Province (annual rainfall 150 mm, soil moisture content 8%).

[0107] Test design:

[0108] Two treatment groups were set: control group (without amendment), amendment group (33 kg / acre), each group with 3 replicates.

[0109] Application method:

[0110] The amendment was mixed with the surface soil (0-20 cm), and the soil water storage was measured after simulated rainfall (50 mm / time).

[0111] Effect monitoring:

[0112] The soil water storage of the amendment group reached 48 tons / acre (36 tons / acre for the control group), and after water absorption, it was slowly released for 150 days, and the survival rate of corn increased from 55% to 82%.

[0113] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A multifunctional composite soil conditioner, characterized in that: It is composed of the following components in percentage by mass: Functional components: Straw powder 20%-50%; Bentonite 10%-30%; Fly ash 10%-30%; Lignin 5%-15%; Synergistic ingredients: Water-soluble polymer compounds 5%-10%; Modified montmorillonite 5%-15%; Bactericidal essential oil microcapsules 1%-5%; Auxiliary components: Activated carbon 3%-8%.

2. A multifunctional composite soil conditioner according to claim 1, characterized in that: The bactericidal essential oil microcapsules are prepared by the following method: (1) dissolving Litsea cubeba essential oil or Litsea cubeba essential oil and toluene-2,4-diisocyanate in toluene to form an oil phase; (2) dissolving polyethylene glycol emulsifier in deionized water to form an aqueous phase; (3) mixing the oil phase with the water phase, adding potassium persulfate as an initiator, and polymerizing in a constant temperature water bath at 50°C for 2 hours to form slow-dissolving polymer microcapsules; (4) After washing, filtering and drying, bactericidal essential oil microcapsules with nanometer particle size are obtained.

3. The multifunctional composite soil conditioner according to claim 1, characterized in that: The water-soluble high molecular compound is guar gum or modified starch, and its molecular weight range is 50,000-500,000 Da, which is used to enhance the stability of soil aggregate structure and the cohesiveness of the improver.

4. The multifunctional composite soil conditioner according to claim 1, characterized in that: The modified montmorillonite is sodium-based or organically modified montmorillonite, and its interlayer cation exchange capacity is ≥80 cmol / kg, and is used to adjust soil pH and achieve slow and controlled release of water.

5. A method for preparing the multifunctional composite soil conditioner according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Preparation of straw powder: Grind corn straw, wheat straw or soybean straw and pass through a 50-100 mesh sieve to obtain straw powder; (2) Preparation of mixed slurry: Mix straw powder, bentonite, lignin, fly ash, water-soluble polymer and water according to the mass ratio, stir until uniform, and control the solid content of the slurry to 10%-40%; (3) Microcapsule compounding: add bactericidal essential oil microcapsules and activated carbon into the mixed slurry at a mass ratio of 1:0.05-0.08 and stir evenly; (4) Spray drying: spray drying the mixed slurry at an inlet temperature of 350-450°C and an outlet temperature of 200-300°C; (5) Post-processing: Dry the dried product at 80-150°C for 1-10 hours, crush it and sieve it to obtain a finished improver with a particle size of ≤2 mm.

6. The preparation method according to claim 5, characterized in that: In the spray drying step, the feed rate is 5-20 L / h and the atomization pressure is 0.2-0.8 MPa, ensuring that the modifying agent particles are uniform and the moisture content is ≤5%.

7. Use of the multifunctional composite soil conditioner according to any one of claims 1 to 4 in the following scenarios: (1) Improvement of saline-alkali land: reduce soil pH and salinity, improve soil structure, and increase crop yields; (2) Remediation of heavy metal contaminated soil: fixation of heavy metals in the soil, including cadmium, lead or arsenic, and reduction of their bioavailability; (3) Water conservation in arid areas: increase soil water storage, achieve slow release of water, and extend the drought resistance period of crops; (4) Soil-borne disease prevention and control: Slow-release microcapsules of bactericidal essential oils can be used to inhibit the pathogens of Fusarium and Rhizoctonia solani, thereby reducing the incidence of crop diseases.

8. The use according to claim 7, characterized in that: In the improvement of saline-alkali land, the application rate of the improver is 30-50 kg / mu. After application, the soil pH is reduced by 0.5-1.2 units and the salt content is reduced by 30%-60%. In the remediation of heavy metal pollution, the application rate of the modifier is 5-15kg / hm 2 , the effective content of heavy metals in the soil is reduced by 40%-70%; To conserve water in arid areas, the application rate of the amendment is 20-40 kg / mu, the soil water storage capacity increases by 20%-50%, and the water release period reaches 90-150 days.

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