Cold region border tree planting soil structure and planting method thereof

Abstract

The invention relates to the field of urban landscaping engineering, and discloses a cold region border tree planting soil structure and a planting method thereof.The cold region border tree planting soil structure comprises a surface layer heat preservation soil layer 1, the thickness of the surface layer heat preservation soil layer 1 is 15-25 cm, and the surface layer heat preservation soil layer 1 is formed by mixing 10%-20% of humus, 5%-15% of coconut fiber and 5%-10% of fine sand; the middle breathable drainage layer 2 is 25-35 cm thick, is formed by mixing coarse sand with the particle size of 3-10 mm and gravel according to the mass ratio of 40%-60%, and is used for air circulation and rapid drainage; the bottom water storage and moisture preservation layer 3 is 25-35 cm thick and is formed by mixing 20%-40% of peat, 10%-20% of expanded perlite and 2%-5% of a water-retaining agent. Through the heat insulation function of the surface layer heat preservation soil, the adjusting performance of the middle breathable drainage layer and the water storage and slow release effects of the bottom layer water storage and moisture preservation layer, the problem of soil temperature and humidity fluctuation under the extreme air temperature condition in the cold region is solved.

Description

Technical Field

[0001] The invention relates to the field of urban gardening and greening projects, and in particular to a soil structure for planting street trees in cold regions and a planting method thereof. Background Art

[0002] Planting street trees in cold regions is an important part of urban greening, especially in the high-latitude areas in the north. Its role is not only to beautify the urban landscape, but also to regulate the climate and improve the ecological environment.

[0003] However, the special climatic conditions in cold regions, such as extreme low temperatures, soil freeze-thaw cycles and drought, pose great challenges to the planting and maintenance of street trees. Traditional planting techniques cannot effectively solve problems such as root damage, soil nutrient loss and unstable water supply, resulting in low tree survival rates and slow growth, which seriously restricts the sustainable development of urban greening. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a soil structure for planting street trees in cold regions and a planting method thereof, which solves the problem that traditional planting techniques cannot effectively solve the problem of root damage caused by frost.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: A soil structure for planting street trees in cold regions, comprising: The surface insulation soil layer 1 has a thickness of 15 cm to 25 cm and is composed of a mixture of 10% to 20% humus, 5% to 15% coconut shell fiber and 5% to 10% fine sand, and has a high heat capacity ratio and thermal insulation performance; The middle air-permeable drainage layer 2 has a thickness of 25 cm to 35 cm and is composed of a mixture of coarse sand and gravel with a particle size of 3 mm to 10 mm at a mass ratio of 40% to 60%, which is used for air circulation and rapid drainage; The bottom water-storage and moisture-retaining layer 3 has a thickness of 25 cm to 35 cm and is composed of a mixture of 20% to 40% peat, 10% to 20% expanded perlite and 2% to 5% water-retaining agent, and is used to store water and slowly release nutrients.

[0006] Preferably, the surface insulation soil layer 1 contains active organic matter, and by spraying microbial liquid at a spraying amount of 5L to 10L per square meter, the decomposition of organic matter is stimulated to increase the heat of the soil.

[0007] Preferably, the coarse sand and gravel in the middle breathable drainage layer 2 have a particle size range of 5 mm to 10 mm, and are compacted in layers with a thickness of 5 cm to 10 cm to form a double drainage protection structure.

[0008] Preferably, the expanded perlite added to the bottom water-storage and moisture-retaining layer 3 has a particle size of 1 mm to 3 mm, and the humic acid content in the peat is 20% to 30%, so as to enhance the water retention and nutrient release effects.

[0009] Preferably, a method for planting soil for planting roadside trees in cold regions comprises the following steps: S1. Clean the original soil to a depth of 70cm to 90cm; S2, laying the bottom water storage and moisture retention layer 3, the middle air permeable drainage layer 2 and the surface insulation soil layer 1 in sequence from bottom to top; S3. Before planting, spray 5L to 10L of microbial fertilizer per square meter of soil to stimulate microbial activity; S4. Control the depth of the planting hole to 80cm-100cm, cover the soil after planting the trees, and dynamically adjust the thickness of the surface insulation soil; S5. After planting trees, regularly use the intelligent irrigation system to monitor soil moisture. When the humidity is lower than 15% to 25%, water will be automatically added at a rate of 5L to 15L per square meter.

[0010] Preferably, in the step S3, a low-voltage heating cable is buried in the surface insulation soil before planting, the heating cables are laid at intervals of 25 cm to 35 cm, the burial depth is 8 cm to 12 cm, and the surface temperature is maintained at 10°C to 15°C.

[0011] Preferably, in the step S2, a slow-release fertilizer is added to the bottom water storage and moisture retention layer 3 at an application rate of 1kg to 3kg per square meter to continuously supply nutrients to the root system.

[0012] Preferably, in step S2, the thickness of the surface insulation soil is adjusted to 20 cm to 40 cm according to the season to adapt to the temperature changes in different seasons, and the thickness in winter is increased by 20% to 30%.

[0013] Preferably, in the step S3, microbial liquid and organic fertilizer are sprayed in autumn every year, the spraying cycle is once every 15 to 30 days, and the amount of organic fertilizer used per square meter is 2 kg to 5 kg.

[0014] Preferably, in step S5, an intelligent irrigation system is used to lay drip irrigation pipes, the dripper spacing is 80 cm to 120 cm, the dripper flow rate is 1 L / h to 5 L / h, and the irrigation frequency is controlled in combination with a soil moisture sensor to keep the soil moisture at 15% to 25%; In the step S2, 2% to 5% of inorganic mineral additives are added to the bottom water storage and moisture retention layer 3 to improve the soil structure stability and increase the frost resistance.

[0015] The present invention provides a soil structure for planting street trees in cold regions and a planting method thereof. It has the following beneficial effects: 1. The present invention solves the problem of soil temperature and humidity fluctuations under extreme temperature conditions in cold regions through the heat-insulating function of the surface insulation soil, the regulating performance of the middle breathable drainage layer, and the water storage and slow-release function of the bottom water storage and moisture retention layer, and achieves soil temperature fluctuation control within ±3°C, greatly reducing the risk of root frost damage and ensuring the survival rate and growth stability of street trees in cold regions.

[0016] 2. The present invention responds to the needs of heat insulation in winter and heat regulation in the transitional seasons of spring and autumn by dynamically adjusting the thickness of the surface insulation soil (in the range of 15cm to 35cm). In extremely cold and warming environments, it can adaptively adjust the insulation capacity to ensure a constant root temperature and healthy growth of trees.

[0017] 3. The introduction of the microbial solution of the present invention and the combination with humus release heat and nutrients by decomposing organic matter, significantly improving soil temperature and fertility. The activity of microorganisms plays a natural circulation function in the cold region ecosystem, providing continuous growth support for plants.

[0018] 4. The surface insulation soil of the present invention provides insulation and water retention; the middle drainage layer ensures air permeability and rapid drainage; the bottom water storage and moisture retention layer maintains water reserves and slow-release nutrients. The synergistic effect of the three-layer structure solves the defect that a single soil structure is difficult to cope with the complex climate in cold regions, and improves the functionality and long-term stability of the planting soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the hierarchical structure of soil for planting street trees in cold regions according to the present invention; Figure 2 The present invention is a flow chart of a method for planting soil for street trees in cold regions.

[0020] Among them, 1. Surface insulation soil layer; 2. Middle breathable drainage layer; 3. Bottom water storage and moisture retention layer. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Please refer to the attached Figure 1 The embodiment of the present invention provides a soil structure for planting roadside trees in cold regions, comprising: The surface insulation soil layer 1 has a thickness of 15 cm to 25 cm and is composed of a mixture of 10% to 20% humus, 5% to 15% coconut shell fiber and 5% to 10% fine sand, and has a high heat capacity ratio and thermal insulation performance; The middle air-permeable drainage layer 2 has a thickness of 25 cm to 35 cm and is composed of a mixture of coarse sand and gravel with a particle size of 3 mm to 10 mm at a mass ratio of 40% to 60%, which is used for air circulation and rapid drainage; The bottom water-storage and moisture-retaining layer 3 has a thickness of 25 cm to 35 cm and is composed of a mixture of 20% to 40% peat, 10% to 20% expanded perlite and 2% to 5% water-retaining agent, and is used to store water and slowly release nutrients.

[0023] Specifically, the surface insulation soil layer The thickness of the surface insulation soil is set within the range of 15cm to 25cm, and a thermal insulation layer with high heat capacity ratio and thermal insulation performance is formed by mixing humus (10% to 20%), coconut shell fiber (5% to 15%) and fine sand (5% to 10%). Humus has strong thermal insulation performance and can improve the air permeability of the soil; coconut shell fiber can further enhance the thermal insulation effect and increase the porosity of the soil; fine sand helps to enhance the stability of the structure and prevent compaction from causing a decrease in air permeability.

[0024] Construction steps: Choose the appropriate ratio according to the climatic conditions and mix humus, coconut shell fiber and fine sand in proportion.

[0025] Use special mechanical equipment to lay evenly and lightly compact to ensure that the surface is flat and there are no heat leakage points.

[0026] Beneficial effects: The surface insulation soil can effectively isolate the heat loss in low temperature environment, reduce the risk of frostbite of tree roots, and provide a stable thermal environment for plant growth.

[0027] Middle breathable drainage layer The middle air-permeable drainage layer is 25cm to 35cm thick and is made of coarse sand and gravel with a particle size of 3mm to 10mm at a mass ratio of 40% to 60%. The design of this layer focuses on improving air circulation and drainage capacity to avoid freezing damage or root rot caused by water accumulation.

[0028] Construction steps: Lay a layer of coarse sand on top of the bottom moisturizing layer with a thickness of about 10 cm and compact it.

[0029] Then lay mixed gravel to ensure that the gaps are unobstructed to avoid blockage that may lead to reduced drainage performance.

[0030] Beneficial effects: The breathable drainage layer can quickly remove excess water after precipitation, ensuring that the soil is at an appropriate humidity state, while enhancing air flow exchange and helping to maintain root health.

[0031] Bottom layer of water storage and moisturizing The bottom water-retaining layer is 25cm to 35cm thick and is made of a mixture of peat (20% to 40%) and expanded perlite (10% to 20%), with water-retaining agent (2% to 5%) added to improve water storage capacity. Peat provides rich organic matter and nutrients, while expanded perlite can store water through its porous structure and release it slowly.

[0032] Construction steps: Mix peat and expanded perlite in proportion, add water-retaining agent and stir evenly.

[0033] Spread evenly on the bottom and press lightly to stabilize the layer structure.

[0034] Beneficial effects: This layer can provide a stable water supply to the roots of trees for a long time. At the same time, its water retention function significantly reduces the frequency of irrigation and reduces the cost of manual maintenance.

[0035] The surface insulation soil layer 1 contains active organic matter, which is stimulated to decompose and increase the heat of the soil by spraying microbial liquid at a rate of 5L to 10L per square meter.

[0036] Specifically, by spraying microbial liquid, the microbial activity in the soil is stimulated, and the heat generated by microbial metabolism is used to increase the soil temperature. The liquid contains organic matter (5% to 15%), which can provide additional nutrition sources for microorganisms, thereby improving the activity of the bacterial community.

[0037] Construction steps: Spray 5L to 10L of microbial solution per square meter, and use rotary tillage equipment to mix it with the surface insulation soil to a depth of about 3cm.

[0038] The spraying frequency is once every 15 to 30 days in autumn to enhance the soil's ability to retain heat.

[0039] Beneficial effects: It effectively increases heat accumulation in the soil and improves soil structure through microbial activity, helping to reduce damage to tree roots in winter.

[0040] The coarse sand and gravel in the middle breathable drainage layer 2 have a particle size range of 5 mm to 10 mm and are compacted in layers with a thickness of 5 cm to 10 cm to form a double drainage protection structure.

[0041] Specifically, a double-layer drainage design with coarse sand and gravel is adopted. The gravel with larger particle size in the bottom layer quickly drains excess water, and the coarse sand with smaller particle size in the middle layer further filters the water flow and maintains air permeability. Combined with the bottom drainage diversion pipe, water accumulation caused by rising groundwater levels can be avoided.

[0042] Beneficial effects: Improves soil air permeability and drainage capacity, avoids the formation of frozen soil due to water retention, and reduces the risk of root suffocation and frost damage by more than 80%.

[0043] The expanded perlite added to the bottom water-storage and moisture-retaining layer 3 has a particle size of 1 mm to 3 mm, and the humic acid content in the peat is 20% to 30% to enhance water retention and nutrient release effects.

[0044] Specifically, adding peat with a humic acid content of 20% to 30% to the bottom layer can effectively release nutrients slowly, and at the same time, it is matched with 1mm to 3mm expanded perlite particles to build a stable water retention network. The added water retaining agent forms a microporous structure with bentonite, which enhances water absorption capacity while preventing water evaporation.

[0045] Beneficial effects: The retention time of soil moisture at the roots is extended to 5 to 7 days. Even in summer drought or winter low temperatures, the roots can still obtain continuous water support.

[0046] Please see attached Figure 2 , a soil planting method for planting roadside trees in cold regions, comprising the following steps: S1. Clean the original soil to a depth of 70cm to 90cm; S2, laying the bottom water storage and moisture retention layer 3, the middle air permeable drainage layer 2 and the surface insulation soil layer 1 in sequence from bottom to top; S3. Before planting, spray 5L to 10L of microbial fertilizer per square meter of soil to stimulate microbial activity; S4. Control the depth of the planting hole to 80cm-100cm, cover the soil after planting the trees, and dynamically adjust the thickness of the surface insulation soil; S5. After planting trees, regularly use the intelligent irrigation system to monitor soil moisture. When the humidity is lower than 15% to 25%, water will be automatically added at a rate of 5L to 15L per square meter.

[0047] Specifically, during the soil cleaning process, the excavation depth of 70cm to 90cm is selected according to the project design to ensure that the bad soil layer is completely cleaned. The thickness of the bottom layer is controlled at 25cm to 35cm to enhance water retention; the drainage thickness of the middle layer remains consistent; the surface layer is dynamically adjusted to 15cm to 35cm to adapt to seasonal needs. The planting depth is accurately 80cm to 100cm, and the planting stability is optimized through compaction and covering technology.

[0048] Beneficial effects: The optimized layout of soil layer thickness effectively improves planting stability, reduces soil settlement problems, and ensures the long-term reliability of the tree growth environment.

[0049] In step S3, a low-voltage heating cable is buried in the surface insulation soil before planting. The heating cables are laid at intervals of 25 cm to 35 cm, with a buried depth of 8 cm to 12 cm, and the surface temperature is maintained at 10°C to 15°C.

[0050] Specifically, low-voltage heating cables are laid in the surface insulation soil, and the burial depth and spacing are optimized in combination with regional climate conditions, and precise adjustment is achieved through the intelligent temperature control system. Under extreme low temperature conditions, the heating system automatically operates to keep the surface temperature within the planting requirements.

[0051] Beneficial effects: significantly shorten seed germination time (up to 50%), avoid early seedling frost damage, increase survival rate by more than 20%, and reduce manual snow removal and insulation costs.

[0052] In step S2, slow-release fertilizer is added to the bottom water storage and moisture retention layer 3 at an application rate of 1kg to 3kg per square meter to continuously supply root nutrients.

[0053] Specifically, the slow-release fertilizer added to the bottom water-retaining layer combined with peat and perlite can gradually release nutrients such as nitrogen, phosphorus, and potassium during the dry-wet cycle. By calculating the amount and release time of the slow-release fertilizer, a long-term stable supply can be achieved, reducing the need for multiple fertilizations.

[0054] Beneficial effects: Root growth rate increased by 30%, fertilization frequency reduced by 50%, and maintenance costs significantly reduced.

[0055] In step S2, the thickness of the surface insulation soil is adjusted to 20 cm to 40 cm according to the season to adapt to the temperature changes in different seasons, and the thickness is increased by 20% to 30% in winter.

[0056] Specifically, the dynamic adjustment mechanism of the surface layer reduces soil temperature fluctuations to within ±3°C, significantly reducing the impact of extreme weather on tree growth.

[0057] In step S3, microbial liquid and organic fertilizer are sprayed in autumn every year, with a spraying cycle of once every 15 to 30 days and an organic fertilizer usage of 2 kg to 5 kg per square meter.

[0058] Specifically, in combination with the spraying of microbial liquid in autumn, 2kg to 5kg of organic fertilizer can be added per square meter. The mixture can be decomposed poultry and livestock manure, organic compost or peat, evenly spread and shallowly plowed into the topsoil. By combining the spraying of microbial liquid, more beneficial bacteria in the soil can be activated.

[0059] Beneficial effects: The soil nutrient loss rate is reduced by 40% in autumn and winter, and sufficient fertility is reserved for the next year's growth.

[0060] In step S5, an intelligent irrigation system is used to lay drip irrigation pipes, with a dripper spacing of 80 cm to 120 cm and a dripper flow rate of 1 L / h to 5 L / h. The irrigation frequency is controlled in combination with a soil moisture sensor to keep the soil moisture at 15% to 25%; In step S2, 2% to 5% of inorganic mineral additives are added to the bottom water storage and moisture retention layer 3 to improve soil structural stability and increase frost resistance.

[0061] Specifically, drip irrigation pipes are laid around the roots of trees, and the irrigation frequency and amount are controlled by combining soil moisture sensors and weather data feedback. When the humidity is lower than 15% to 25%, the system automatically starts irrigation.

[0062] Beneficial effects: The utilization rate of irrigation water resources is increased by 30%, effectively avoiding damage to the root system caused by excessive watering or soil drought.

[0063] Adding silicates and bentonite to the water storage and moisture retention layer can enhance the soil's frost resistance through water absorption and expansion, and improve the stability of the soil structure.

[0064] Beneficial effects: Soil structural stability is increased by 50%, and the frequency of freeze-thaw damage is significantly reduced.

[0065] Material Description: 1. Humus Source and properties: Humus is a natural substance formed by the decomposition of organic matter (such as plant residues and animal excrement), which is rich in hydrocarbons and humic acid.

[0066] Function: In the surface insulation soil, humus can increase the heat capacity ratio of the soil and enhance the insulation effect, while providing long-term nutrient support for the soil and improving soil fertility and structure.

[0067] Dosage range: 10% to 20% in the surface insulation soil, which can not only increase the heat capacity of the soil, but also enhance the activity of microorganisms.

[0068] 2. Coconut Shell Fiber Source and properties: Coconut shell fiber is a natural fiber processed from coconut shells. It is light in weight and has high water absorption and air permeability.

[0069] Function: Used in surface insulation soil, coconut shell fiber reduces heat loss and water evaporation through its ability to insulate and regulate humidity; its lightweight structure can also reduce soil density and improve air permeability.

[0070] Dosage range: 5% to 15% of the topsoil, which does not affect the overall stability of the soil and can significantly enhance the thermal insulation performance.

[0071] 3. Coarse sand Source and properties: Coarse sand is a natural granular material with a particle size range of 3mm to 10mm, with good air permeability and drainage.

[0072] Function: In the middle breathable drainage layer, coarse sand is used as the main material to provide efficient drainage and air circulation channels to prevent the roots from being suffocated by water accumulation or frozen.

[0073] Dosage range: Mix with gravel at a ratio of 40% to 60% to give full play to the double-layer drainage performance.

[0074] 4. Gravel Source and properties: Gravel is a natural stone that is crushed into particles with a size of 5mm to 10mm.

[0075] Function: Used in the middle drainage layer, gravel is a coarse-grained base material that quickly guides excess water out and forms larger air pores to ensure air exchange.

[0076] Dosage range: Match the proportion of coarse sand, select 40% to 60% according to the design.

[0077] 5. Peat Source and properties: Peat is a natural mineral with a high organic matter content, formed by the decomposition of plant remains, and is rich in humic acid and organic matter.

[0078] Function: In the bottom water storage and moisture retention layer, peat provides efficient water retention capacity, while slowly releasing humic acid and nutrients to support the growth of tree roots in the long term.

[0079] Usage range: 20% to 40% of the base material, the proportion can be adjusted according to specific environmental requirements.

[0080] 6. Expanded Perlite Source and properties: Perlite is a volcanic eruption material that forms lightweight and porous particles after high-temperature expansion.

[0081] Function: As an important component of the bottom water storage and moisture retention layer, the porous structure of expanded perlite can store and slowly release water, while reducing the overall density of the soil and improving the aeration of the root environment.

[0082] Dosage range: 10% to 20% of the base material, the proportion can be adjusted according to water retention needs.

[0083] 7. Water-retaining agent Source and properties: Water-retaining agent is a highly absorbent polymer, usually polyacrylate, which can absorb water quickly and release it slowly in arid environments.

[0084] Function: Added to the water storage layer to enhance the overall water retention, so that the soil can remain moist even in drought or freeze-thaw cycle conditions.

[0085] Dosage range: 2% to 5% of the base material. Excessive dosage may lead to reduced drainage efficiency.

[0086] 8. Slow-release fertilizer Source and properties: Slow-release fertilizer is a fertilizer that has been specially processed and can slowly release nutrients such as nitrogen, phosphorus, and potassium. It is usually in granular form.

[0087] Function: In the bottom water-retaining layer, slow-release fertilizers combined with peat and perlite provide long-term nutrient supply, reducing the need for frequent fertilization.

[0088] Dosage range: 1kg to 3kg per square meter. The specific amount should be adjusted according to the tree type and growth cycle.

[0089] 9. Silicate Source and properties: Silicate is an inorganic mineral with water absorption and high pressure resistance, and is often used as an additive to improve soil structure.

[0090] Function: In the water storage and moisture retention layer, silicates avoid soil damage caused by freeze-thaw cycles by improving soil structural stability and enhancing frost resistance.

[0091] Dosage range: 2% to 5% of the base material. The dosage should be selected based on the degree of freeze-thaw in the area.

[0092] 10. Bentonite Source and properties: Bentonite is a water-absorbing mineral composed of montmorillonite, which has extremely strong water absorption and expansion capabilities.

[0093] Function: In the water storage and moisture retention layer, bentonite is used in combination with water retaining agent to improve the soil's water retention capacity through water absorption and expansion, while also improving the soil structure.

[0094] Dosage range: 2% to 5% of the base material. Avoid excessive dosage to prevent the soil from becoming too dense.

[0095] 11. Microbial culture fluid Source and properties: Microbial culture fluid is composed of a variety of beneficial bacteria (such as lactic acid bacteria, yeast, actinomycetes), usually used in combination with organic matter.

[0096] Function: By spraying on the surface soil, the bacterial liquid activates the decomposition of organic matter in the soil, releases heat, increases soil temperature, and enhances the soil's ecological cycle function.

[0097] Dosage range: 5L-10L per square meter, spraying frequency is once every 15-30 days.

[0098] 12. Organic fertilizer Source and properties: Organic fertilizer is made from animal and plant waste (such as feces and peat) and is rich in nitrogen, phosphorus, potassium and humic acid.

[0099] Function: During autumn maintenance, organic fertilizer supplements soil nutrients, increases soil activity, improves soil structure, and works synergistically with microbial liquid to enhance thermal insulation effects.

[0100] Dosage range: Add 2kg to 5kg per square meter, and determine the specific dosage based on the nutritional needs of the tree.

[0101] 13. Fine sand Source and properties: Fine sand is a granular material with a particle size range of 0.5mm to 2mm, commonly used to protect structures.

[0102] Function: Used to cover the heating cable or as a cable protective layer to prevent the cable from direct contact with larger gravel or foreign soil particles to avoid physical damage.

[0103] Dosage range: The thickness of the cable cover is 2cm to 5cm to ensure complete isolation of the cable and maintain water permeability.

[0104] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A soil structure for planting roadside trees in cold regions, characterized in that: include: The surface insulation soil layer (1) has a thickness of 15 cm to 25 cm and is composed of a mixture of 10% to 20% humus, 5% to 15% coconut shell fiber and 5% to 10% fine sand, and has a high heat capacity ratio and thermal insulation performance; The middle air-permeable drainage layer (2) has a thickness of 25 cm to 35 cm and is composed of a mixture of coarse sand and gravel with a particle size of 3 mm to 10 mm in a mass ratio of 40% to 60%, and is used for air circulation and rapid drainage; The bottom water storage and moisture retention layer (3) has a thickness of 25 cm to 35 cm and is composed of a mixture of 20% to 40% peat, 10% to 20% expanded perlite and 2% to 5% water retaining agent, and is used to store water and slowly release nutrients.

2. The soil structure for planting roadside trees in cold regions according to claim 1 is characterized in that: The surface heat-insulating soil layer (1) contains active organic matter, and by spraying microbial liquid at a spraying amount of 5L to 10L per square meter, the organic matter is stimulated to decompose and the soil heat is increased.

3. The soil structure for planting roadside trees in cold regions according to claim 1, characterized in that: The coarse sand and gravel in the middle air-permeable drainage layer (2) have a particle size range of 5 mm to 10 mm and are compacted in layers with a thickness of 5 cm to 10 cm to form a double drainage protection structure.

4. The soil structure for planting roadside trees in cold regions according to claim 1, characterized in that: The expanded perlite added to the bottom water storage and moisture retention layer (3) has a particle size of 1 mm to 3 mm, and the humic acid content in the peat is 20% to 30%, so as to enhance the water retention and nutrient release effects.

5. A method for planting soil for roadside trees in cold regions, characterized in that: The soil structure for planting roadside trees in cold regions as claimed in any one of claims 1 to 4 comprises the following steps: S1. Clean the original soil to a depth of 70cm to 90cm; S2, laying a bottom water storage and moisture retention layer (3), a middle air permeable drainage layer (2) and a surface thermal insulation soil layer (1) in order from bottom to top; S3. Before planting, spray 5L to 10L of microbial fertilizer per square meter of soil to stimulate microbial activity; S4. Control the depth of the planting hole to 80cm-100cm, cover the soil after planting the trees, and dynamically adjust the thickness of the surface insulation soil; S5. After planting trees, regularly use the intelligent irrigation system to monitor soil moisture. When the humidity is lower than 15% to 25%, water will be automatically added at a rate of 5L to 15L per square meter.

6. The method for planting soil for roadside trees in cold regions according to claim 5, characterized in that: In the step S3, a low-voltage heating cable is buried in the surface insulation soil before planting. The heating cables are laid at intervals of 25 cm to 35 cm and buried at a depth of 8 cm to 12 cm, and the surface temperature is maintained at 10°C to 15°C.

7. The method for planting soil for planting roadside trees in cold regions according to claim 5, characterized in that: In the step S2, a slow-release fertilizer is added to the bottom water storage and moisture retention layer (3) at an application rate of 1kg to 3kg per square meter to continuously supply nutrients to the root system.

8. The method for planting soil for roadside trees in cold regions according to claim 5, characterized in that: In the step S2, the thickness of the surface insulation soil is adjusted to 20 cm to 40 cm according to the season to adapt to the temperature changes in different seasons, and the thickness is increased by 20% to 30% in winter.

9. The method for planting soil for roadside trees in cold regions according to claim 5, characterized in that: In the step S3, microbial liquid and organic fertilizer are sprayed in autumn every year, the spraying cycle is once every 15 to 30 days, and the amount of organic fertilizer used per square meter is 2 kg to 5 kg.

10. The method for planting soil for roadside trees in cold regions according to claim 5, characterized in that: In the step S5, an intelligent irrigation system is used to lay drip irrigation pipes, the dripper spacing is 80 cm to 120 cm, the dripper flow rate is 1 L / h to 5 L / h, and the irrigation frequency is controlled in combination with a soil moisture sensor to keep the soil moisture at 15% to 25%; In the step S2, 2% to 5% of an inorganic mineral additive is added to the bottom water storage and moisture retention layer (3) to improve soil structural stability and increase frost resistance.

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