Soil in-situ reconstruction and soil improvement method suitable for open grassland mining area

Abstract

According to the soil in-situ reconstruction and soil improvement method suitable for the open-air grassland mining area, soil in the grassland mining area is reconstructed, the subsoil layer, the isolation layer and the reconstructed soil layer are sequentially arranged from bottom to top, the added clay isolation layer has the water and fertilizer retention effect, plant growth is facilitated, and the soil in-situ reconstruction and soil improvement effects are achieved. Sandy soil and clay are compounded to serve as a reconstructed soil layer, the used clay is high in organic matter content and can be bonded into micro aggregates and large aggregates, the soil texture is compact, soil particle gaps are small, and the water and fertilizer retention capacity is high. On the basis, the multi-dimensional soil improvement method is provided and comprises the steps of platform and slope soil reconstruction, platform soil fertility improvement and platform microtopography finishing, and the ecology of the grassland mining area can be effectively restored through the synergistic effect of the multi-dimensional improvement scheme.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a method for in-situ soil reconstruction and soil improvement suitable for open-pit grassland mining areas. Background Art

[0002] Northern open-pit grassland mining areas are typical semi-arid grasslands, where the ecological stability of vegetation is relatively fragile. Once damaged, restoration is extremely difficult. The biggest challenge in ecological restoration in open-pit mining areas is the severe loss of topsoil due to coal mining. The surface of the mining area and dumping grounds is essentially covered with surrounding rock and rock debris, with no soil to cover. Soil reconstruction is a prerequisite for ensuring vegetation growth and re-establishment, and has become a key technical means of soil remediation in northern open-pit grassland mining areas. Therefore, soil reconstruction in open-pit grassland mining dumps is the prerequisite and foundation for successful ecological restoration.

[0003] The existing soil reconstruction scheme mainly adopts two modes: one is to directly and evenly cover the surface soil with a thickness of about 50cm in the area where the soil quality is poor and the vegetation does not have the conditions to stand; the other is to directly level and compact the gravel or coarse sand layer when there is no topsoil available. The above soil reconstruction scheme has the following technical problems: (1) Due to the limited amount of topsoil, the thickness of the available topsoil is less than 1 meter. Due to the limited amount of stored topsoil, the topsoil is mostly a mixture of topsoil and sand or there is basically no soil to cover. The soil has a low clay content, low water retention capacity, poor nutrients, low biological activity and other problems, which are usually not suitable for plant growth. In addition, the core problem of directly using sand mixed with topsoil as topsoil is that the sand content is too high, there is a lack of silt and clay, the organic matter content is low, and it cannot be bonded into micro-aggregates and macro-aggregates. The soil texture is loose, the gaps between soil particles are large, the water and fertilizer retention capacity is poor, which is not conducive to crop growth and there are problems of "water leakage and fertilizer leakage". (2) The thickness of the topsoil used is generally about 50cm. The thickness of the topsoil is large, and the cost of construction and transportation of the topsoil is high. At the same time, the compaction of the topsoil is poor, and the water storage capacity is poor. The amount of water used for topsoil irrigation is large, and the number of irrigations is high, so the irrigation cost is relatively high. (3) The ability to improve fertility is insufficient. For example, only by applying organic fertilizer to increase the content of organic matter and nitrogen, phosphorus, potassium and other elements in the soil, the vegetation survival rate is low and the vegetation growth is poor. (4) The soil remediation method is relatively simple, and single-dimensional means are mostly used to repair the soil, and the soil remediation effect does not meet the requirements.

[0004] Therefore, in response to the above problems, it is urgent to propose a soil in situ reconstruction method and soil improvement method suitable for open-pit grassland mining areas to carry out ecological restoration work. Summary of the Invention

[0005] In view of this, in a first aspect, the present invention aims to propose a soil in-situ reconstruction method suitable for open-pit grassland mining areas, so as to solve the problems that existing soil reconstruction schemes are not conducive to vegetation growth and have high construction costs.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A soil in-situ reconstruction method applicable to open-pit grassland mining areas comprises the following steps:

[0008] Step 1: Level and compact the ground surface within the spoil dump platform of the open-pit grassland mining area to form a subsoil layer;

[0009] Step 2: directly cover the subsoil layer with a layer of 5-10 cm clay as an isolation layer;

[0010] Step 3: Cover the isolation layer with a mixture of sand and clay to a thickness of 15 to 20 cm as a reconstructed soil layer.

[0011] Furthermore, the volume ratio of clay to sand in the reconstructed soil layer is (1:2.5) to (1:5.5).

[0012] Furthermore, the volume ratio of clay to sand in the reconstructed soil layer is 1:4 to 1:5, the thickness of the isolation layer is 8 to 10 cm, and the thickness of the reconstructed soil layer is 18 to 20 cm.

[0013] Furthermore, the volume ratio of clay to sand in the reconstructed soil layer is 1:5, the thickness of the isolation layer is 10 cm, and the thickness of the reconstructed soil layer is 20 cm.

[0014] Furthermore, the method further comprises step 4 of improving the soil. The soil improvement comprises applying two inorganic fertilizers, quick-acting fertilizer and slow-release fertilizer, and organic materials. The organic materials in step 4 are sourced from livestock and poultry manure, herbaceous plant straw from the spoil dump, and other agricultural waste in the mining area.

[0015] Furthermore, the mass ratio of N, P and K in the inorganic fertilizer is 4:2:1.

[0016] Furthermore, the clay is clay that occurs near an open-pit grassland mining area.

[0017] Furthermore, the quick-acting fertilizer and the slow-release fertilizer, the two inorganic fertilizers, the organic fertilizer and the sandy soil mixture are evenly mixed by using deep plowing machinery (the plowing depth is about 20 cm) to plow the soil multiple times.

[0018] On the other hand, the present invention also proposes a multi-dimensional soil improvement method suitable for open-pit grassland mining areas, including platform soil reconstruction, slope soil reconstruction, platform soil fertility improvement, and platform micro-topography renovation.

[0019] The platform soil reconstruction method has been described above and will not be repeated here. The following is a detailed description of slope soil reconstruction, platform soil fertility improvement and platform micro-topography renovation.

[0020] (1) Slope soil reconstruction

[0021] The slope soil reconstruction plan adopts the technical model of sand / clay compounding to improve soil texture. Specifically, clay and sand are mixed in a ratio of 1:2 to obtain a reconstructed soil matrix. Fertilizer, organic material, starch branched adhesive and the reconstructed soil matrix are fully mixed. When covering the soil, a certain amount of water is mixed into a paste, and the paste is sprayed on the slope of the spoil field using spraying technology (preferably with a thickness of 15 to 20 cm).

[0022] When covering the soil, the reconstructed soil matrix is stirred into a uniform paste by mixing it with a certain amount of water. This paste is then sprayed onto the slope of the dumping area using a small sprayer at a 20cm covering thickness. The slope-surface spraying technology using a starch-branched adhesive helps conserve water and fertilizer, and prevents soil erosion. Furthermore, this new spraying technology can replace the traditional straw mat method used in ecological restoration. It requires minimal labor, is quick to install, and offers excellent results. The construction cost is low, resulting in excellent economic benefits.

[0023] (2) Improvement of soil fertility on the platform

[0024] Specifically, by combining quick-acting fertilizers, slow-release fertilizers and a variety of organic fertilizers.

[0025] Soil element deficiencies are common in mine remediation, but this problem is particularly acute in open-pit grassland mining areas located in semi-arid grassland regions. During mine ecological restoration, soil quality often declines significantly due to the damage mining activities inflict on the surrounding environment, including damage to land and water sources. Due to the arid climate and scarce rainfall in these areas, the soil's inherent moisture and nutrient content is relatively low. Combined with the damage caused by mining activities, soil quality deteriorates further, leading to even more severe deficiencies in nutrients such as nitrogen, phosphorus, and potassium.

[0026] Soil nutrient analysis and testing results indicate that the reclaimed soil in the dump site is low in nitrogen, phosphorus, and potassium, necessitating the addition of fertilizers containing nitrogen, phosphorus, and potassium to meet plant growth requirements. To increase soil nutrient content, reduce the need for complex construction procedures, and improve fertilizer utilization, improved fertilization methods, including the use of quick-acting and slow-release fertilizers and organic fertilizers, can be used to optimize fertilization structure, promote scientific and rational fertilization techniques, and enhance fertilizer utilization efficiency.

[0027] Fast-acting fertilizers generally have a short duration of action and contain high concentrations of nutrients, typically including nitrogen, phosphorus, and potassium. These nutrients are released quickly, increasing plant absorption, thereby rapidly boosting the nutrient content of vegetation in the dumping area and promoting plant growth and regreening. Slow-release fertilizers, on the other hand, slowly release their nutrients over the entire growing season, or even several seasons. This delays plant absorption and utilization, resulting in a longer-lasting effect than standard fast-acting fertilizers. The slower release of slow-release fertilizers can eliminate the need for additional topdressing. They also have a positive impact on soil remodeling in dumping areas, specifically in three ways: First, they increase soil nutrient content. Applying fast-acting fertilizers can quickly replenish key nutrients like nitrogen, phosphorus, and potassium in the soil, meeting the basic needs of plant growth. This increase in nutrients helps promote plant growth and development, enhancing their adaptability to the environment. Second, they improve soil structure. Applying fast-acting fertilizers can indirectly impact soil structure by promoting plant growth and root development. The growth and expansion of plant roots helps increase soil looseness and porosity, improving soil aeration and water permeability. At the same time, the secretions of plant roots and the decomposition of fallen leaves also contribute to the formation of soil organic matter, further improving soil structure. Thirdly, it enhances soil microbial activity. The application of quick-acting fertilizers can promote plant growth and development, thereby providing more organic matter and energy sources for soil microorganisms. This helps increase the number and activity of soil microorganisms, promoting their metabolism and reproduction. Soil microorganisms play an important role in soil nutrient cycling and organic matter decomposition, so increasing their activity can help further improve soil quality.

[0028] Organic materials are sourced from locally produced agricultural waste, such as livestock and poultry manure and straw from herbaceous plants in dumping grounds. By fully utilizing these wastes and fermenting them into compost, they can reduce fertilizer use, increase soil organic matter and nutrient content, and address agricultural waste disposal issues, achieving recycling and aligning with the concept of green agricultural development. The application of organic materials improves the soil structure of dumping grounds, reconstructing the soil, and increasing soil organic matter content. The organic matter in manure accelerates the decomposition of organic materials, thereby increasing the humus content in the topsoil. Furthermore, they improve soil physical properties. As organic materials decompose in the soil, they form numerous micropores, which increase soil aeration and water permeability. This improved soil pore structure facilitates root growth and respiration, as well as water infiltration and drainage. The application of organic materials can also regulate soil compaction, making the soil more loose. Loose soil facilitates root penetration and expansion, improving soil quality. The humus produced by the decomposition of organic materials is a key binder for soil aggregate formation. Functional groups in humus can form chemical bonds with metal ions on the surface of soil particles, binding them together to form stable aggregates. Finally, substances such as polysaccharides and proteins in organic materials also possess viscosity and elasticity, promoting the formation of soil aggregates. These substances form a network structure within the soil, increasing soil stability. Therefore, by combining quick-acting and slow-release fertilizers with a variety of organic materials, the content of water-stable aggregates and organic matter in the reconstructed soil of the dumping ground can be increased, soil carbon sequestration can be increased, and the reconstructed soil structure can be improved, thereby enhancing the fertility of the reconstructed soil.

[0029] (3) Platform micro-topography renovation

[0030] To address the widespread drought and water shortages in open-pit grassland mining areas, micro-topography remediation is a key complementary technology alongside in-situ soil reconstruction within the overall soil remediation technology approach. Its core objective is to maximize surface and soil moisture retention, inhibit surface runoff, and promote vertical infiltration of surface water, while also helping to prevent soil erosion. Micro-topography remediation and in-situ soil reconstruction are complementary technical measures that work synergistically to improve the water and fertilizer retention properties of reconstructed soils.

[0031] Surface microtopography modification technology involves designing the platform's surface microtopography during the reclamation and leveling process. Specifically, a bulldozer or leveler is used to level the platform, creating a slope toward the dumping road, creating a reverse slope to prevent water from eroding the dumping site's slopes. The platform is then partially leveled with typical designs such as gridded ridges and borders. A grid-like pattern is then used to intercept and store water. The primary goal is to achieve this by intercepting and storing water in sections along the platform's grid, reducing surface runoff, increasing vertical infiltration, and improving soil moisture content. This allows for full utilization of limited rainfall and facilitates vegetation restoration.

[0032] Compared with the existing technology, the soil reconstruction and soil remediation method applicable to open-pit grassland mining areas described in the present invention has the following advantages:

[0033] 1. The thickness of the reconstructed soil in the present invention is 20 to 30 cm, which is significantly lower than the 50 cm thickness of the covering soil in the prior art. Reducing the thickness of the covering soil reduces the cost of covering soil construction and transportation, and solves the problem of limited covering soil reserves.

[0034] 2. The added clay isolation layer has the function of retaining water and fertilizer, which is beneficial to plant growth. At the same time, it can reduce the amount of water used for irrigation and the number of irrigation times, thereby reducing irrigation costs.

[0035] 3. The clay used in the isolation layer and the reconstructed soil layer can bond into microaggregates and macroaggregates, making the soil texture compact, the gaps between soil particles small, and the ability to retain water and fertilizer strong, solving the problem of "water and fertilizer leakage" and benefiting crop growth.

[0036] 4. Compared with traditional single restoration methods, the present invention restores the ecology of open-pit grassland mining areas from three dimensions: soil reconstruction, fertility improvement, and micro-topography renovation. The three methods work together to achieve better ecological restoration effects.

[0037] 5. Open-pit grassland mining areas are mostly pastoral areas, where most herders make their livings from grazing. They use large quantities of agricultural waste, such as livestock and poultry manure and herbaceous straw from spoil dumps, as organic fertilizer. This facilitates local access and utilization, reducing procurement costs while also maintaining the local microbial ecosystem. Fermentation and composting of these wastes increases soil organic matter and nutrient content. Quick-acting and slow-release inorganic fertilizers are used to mitigate rapid nutrient loss. Slow-release fertilizers are significantly effective in increasing crop yields, reducing fertilizer application rates, and mitigating environmental pollution caused by nutrient loss.

[0038] 6. Using a starch-branched matrix spraying technique on slopes helps conserve water and fertilizer, and prevent soil erosion. This new spraying technique replaces the traditional method of covering with straw mats for soil and water conservation, reducing the use of straw mats and the material costs of water conservation. Furthermore, it requires less labor, lowering labor costs, and allows for rapid installation, excellent results, and a low construction cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the in situ reconstructed soil structure;

[0040] Figure 2 This is the disappearance time diagram of surface water under different treatments;

[0041] Figure 3This is the overall trend diagram of soil moisture content under different treatments over time;

[0042] Figure 4 This is the change diagram of vegetation biomass under different fertilization treatments under soil reconstruction mode;

[0043] Figure 5 This is a graph showing the changes in plant biomass under different soil reconstruction treatments under fertilization patterns;

[0044] Figures 6 to 8 This is a graph showing the changes in soil nutrient content (available nitrogen, available phosphorus and available potassium) under different soil reconstruction treatments under fertilization modes. DETAILED DESCRIPTION

[0045] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein may be combined with each other.

[0046] The present invention will be described in detail below with reference to the accompanying drawings and examples. The following examples of the present invention, especially the experimental design and data, are all from the actual project "Key Technologies for Soil Construction and Rapid Maturation of Newly Renovated Black Soil Farmland" (Project No.: 2024YFD1500500).

[0047] like Figure 1 As shown, an embodiment of the present invention provides a soil in-situ reconstruction method applicable to open-pit grassland mining areas, comprising the following steps:

[0048] Step 1: Level and compact the surface of the spoil dump platform in the open-pit grassland mining area to form a subsoil layer;

[0049] Step 2: continuously and evenly covering the subsoil layer with a layer of clay having a thickness of 5 to 10 cm as an isolation layer;

[0050] Step 3: Covering the isolation layer with a reconstructed soil layer having a thickness of 15 to 20 cm, wherein the reconstructed soil layer is a mixture of sand and clay in a volume ratio of (1:2.5) to (1:5.5);

[0051] The clay is clay associated with open-pit grassland mining areas.

[0052] In an embodiment of the present invention, the surface of the platform of the spoil dump in the open-pit grassland mining area is first leveled and compacted not only for the convenience of subsequent operations (such as covering the isolation layer and laying the reconstructed soil layer), but also to form a solid foundation. 5 to 10 cm of clay as an isolation layer not only retains water and fertilizer, but also ensures the highest cost-effectiveness of reconstruction. The reconstructed soil layer and the isolation layer with a covering thickness of 15 to 20 cm make the reconstructed soil thickness reach 20 to 30 cm, reducing the thickness of the covering soil while reducing the cost of covering soil construction and transportation, solving the problem of "water leakage and fertilizer leakage", and being beneficial to crop growth.

[0053] Furthermore, an embodiment of the present invention provides a method for in-situ soil reconstruction suitable for open-pit grassland mining areas, and the volume ratio of clay and sand in the reconstructed soil layer is preferably (1:4) to (1:5). Based on the volume ratio, it is further preferred that the thickness of the isolation layer is 8 to 10 cm. It is further preferred that the thickness of the reconstructed soil layer is 18 to 20 cm. The reconstructed soil layer is composed of sand and clay mixed in a volume ratio of (1:2.5) to (1:5.5), which can basically guarantee the growth environment of vegetation and crops, and a further preferred condition is to achieve cost control and achieve high cost performance on the basis of ensuring a better growth environment for vegetation and crops.

[0054] Furthermore, embodiments of the present invention provide an in-situ soil reconstruction method suitable for open-pit grassland mining areas. Based on experimental results, the volume ratio of clay to sand in the reconstructed soil layer is preferably 1:5. The thickness of the isolation layer is preferably 10 cm. Furthermore, the thickness of the reconstructed soil layer is preferably 20 cm.

[0055] Furthermore, an embodiment of the present invention provides a soil in-situ reconstruction method applicable to open-pit grassland mining areas, comprising:

[0056] Apply an inorganic fertilizer consisting of a quick-acting fertilizer and a slow-release fertilizer, with a N:P:K mass ratio of 4:2:1. The N:P:K mass ratio in the inorganic fertilizer primarily affects the sustained and effective improvement of the soil and the growth requirements of vegetation. The optimal N:P:K mass ratio in the inorganic fertilizer is determined based on numerous experiments combined with vegetation cultivation experience.

[0057] Apply organic materials sourced from local livestock and poultry manure, herbaceous plant straw or agricultural waste in the mining area.

[0058] Furthermore, an embodiment of the present invention provides a soil in situ reconstruction method applicable to open-pit grassland mining areas. Preferably, in step 4, deep plowing machinery is used to plow the soil at a depth of 20 cm to evenly mix the inorganic fertilizer, organic material and the reconstructed soil layer.

[0059] On the other hand, an embodiment of the present invention provides a multi-dimensional soil improvement method applicable to open-pit grassland mining areas, comprising:

[0060] The platform soil is reconstructed using the soil in situ reconstruction method applicable to open-pit grassland mining areas as described above;

[0061] Slope soil reconstruction: Mix clay and sand in a volume ratio of 1:2 to form a reconstructed matrix, mix it with fertilizer, organic materials, and starch-branched adhesive, add water and stir into a paste, and spray it on the slope with a thickness of 15 to 20 cm.

[0062] Furthermore, an embodiment of the present invention provides a multi-dimensional soil improvement method applicable to open-pit grassland mining areas, comprising:

[0063] Improve platform soil fertility: Apply quick-acting fertilizers, slow-release fertilizers and organic materials to the reconstructed platform soil;

[0064] Platform micro-topography renovation: Use a bulldozer to level the platform and form a reverse slope, and then build a ridge or border structure.

[0065] Furthermore, an embodiment of the present invention provides a multi-dimensional soil improvement method suitable for open-pit grassland mining areas, wherein the N, P, and K mass ratio of the inorganic fertilizer formed by the quick-acting fertilizer and the slow-release fertilizer is 4:2:1, and the source of the organic material is local livestock and poultry manure, herbaceous plant straw or agricultural waste in the mining area.

[0066] Furthermore, an embodiment of the present invention provides a multi-dimensional soil improvement method suitable for open-pit grassland mining areas. The platform micro-topography renovation includes using a bulldozer or a leveler to level the table surface so that the entire platform has a certain slope toward the dumping road, forming a reverse slope to prevent the platform water flow from eroding the side slopes of the dumping yard.

[0067] Furthermore, an embodiment of the present invention provides a multi-dimensional soil improvement method suitable for open-pit grassland mining areas, and then the platform surface is designed with grid ridges and ridges to achieve local leveling and adopt grid-type block interception.

[0068] The above four aspects of platform soil reconstruction, slope soil reconstruction, platform soil fertility improvement and platform micro-topography renovation can be based on platform soil reconstruction and combined with any one or two of the other three to form an embodiment.

[0069] Based on the local sand and clay materials in the mining area and the principle of soil configuration, the combination formula of sand and clay compounded into soil at different proportions is explored, which is suitable for the habitat conditions of grassland mining areas and effectively realizes the water and fertilizer retention properties of reconstructed soil.

[0070] Example Experimental Design

[0071] (1) Soil design for soil reconstruction experiments

[0072] The subsoil, clay, and sand in the experiment were all collected from the dumping site of the mine (Zha Mine). The reconstructed soil layers simulated the natural state of the dumping site. From bottom to top, they consisted of: dumping site subsoil (5 cm), a water- and fertilizer-retaining isolation layer (5 cm and 10 cm of clay), and a reconstructed soil layer (20 cm of sand-clay composite soil). The sand-clay composite soil experiment involved mixing clay and sand in different ratios (1:0, 1:1, 1:2, 1:5, and 0:1) and then potting them. A total of 15 treatments were performed, with four replicates for each treatment. The experimental setup is shown in Table 1.

[0073] Table 1 Experimental settings

[0074]

[0075] (2) Fertilization design for soil reconstruction experiments

[0076] Fertilization experiments were carried out based on soil reconstruction experiments.

[0077] Soils in grassland areas are typically typical meadow soils or brown soils, which have relatively high requirements for nitrogen, phosphorus, and potassium. Grassland vegetation, such as herbaceous plants and grasslands, typically has a high nitrogen requirement, as it is a key nutrient for plant growth. Phosphorus and potassium are also essential for plant growth, but in relatively lower quantities.

[0078] Fertilizer Ratio Experimental Design: According to the experimental design, a 10cm layer of clay was laid as a water- and fertilizer-retaining layer, and a 20cm layer of clay-sand mixture was laid on top, with a sand-to-clay ratio of 1:5. Four treatments were set up: CK (blank control), Fertilization Treatment 1, Fertilization Treatment 2, and Fertilization Treatment 3, with five replicates per treatment. The total seed dosage for the vegetation was 15kg / mu. The vegetation consisted of legumes, grasses, and weeds. Three fertilizers were used: urea containing 46% nitrogen (N), superphosphate containing 16% phosphorus (P2O5), and potassium sulfate containing 52% potassium (K2O). The urea dosage was 15kg / mu. The ratio of N:P:K in Treatment 1 was 4:2:1; in Treatment 2, it was 3:1:0; and in Treatment 3, it was 1.4:1:0. The fertilizer ratios are shown in Table 2.

[0079] Table 2 Fertilizer ratio treatment

[0080]

[0081] Experimental results analysis

[0082] (1) Soil texture

[0083] According to international soil classification standards, clay content is the primary criterion. When the clay content is less than 15%, the soil may be sandy or loamy; when the content is between 15% and 25%, the soil may be clay loam; and when the content is greater than 25%, the soil may be clay. When the silt content reaches 45% or more, the word "silty" should be added before the texture classification name. When the sand content is between 55% and 85%, the word "sandy" should be added before the texture classification name; when the sand content is greater than 85%, the soil is simply designated as loamy sand; and when the sand content is greater than 90%, it is simply designated as sandy soil. Table 3 shows the soil textures of the reconstructed soil layers at different mix ratios.

[0084] Table 3 Soil texture of reconstructed soil layers under different ratios

[0085]

[0086] (2) Changes in surface water disappearance time under different treatments

[0087] After mixing sand and clay according to the different experimental treatment ratios and potting, the reconstituted soil was allowed to settle naturally for 11 days before testing its water retention. Each pot was evenly and slowly watered with 5.2 L of water, ensuring complete saturation. The time it took for the visible water to disappear was carefully recorded. The soil moisture content was measured daily at the same time (3:00 PM) for six days.

[0088] like Figure 2 As shown in the figure, by analyzing the changes in the disappearance time of the surface water under different treatments, it can be concluded that among all treatments, the surface water disappearance time of the full clay treatment (T1, T1B1, and T1B2) was the slowest, all lasting more than one hour, indicating that the soil water retention efficiency of the full clay treatment was the best. Compared with the other treatments, the surface water disappeared fastest in the full sand treatment (T5) and the full sand treatment with a 5cm isolation layer (T5B1). However, the surface water disappearance time was slowed in the treatment with a 10cm isolation layer (T5B2), indicating that the addition of a 10cm isolation layer to the full sand treatment can effectively increase the water retention capacity of the reconstructed soil.

[0089] When the clay-sand ratio was 1:1 or 1:2 (T2 and T3), indicating relatively low sand content, the effect of adding an isolation layer was not significant. However, when the clay-sand ratio was 1:5 and the all-sand treatments (T4 and T5), with a relatively high sand content in the reconstructed soil, the thicker the isolation layer, the better the water retention of the reconstructed soil.

[0090] (III) Soil moisture content under different soil reconstruction treatments over time

[0091] Each treatment was watered 5.2L to ensure that the soil was completely irrigated. After the surface water disappeared, the first sampling was carried out to measure the soil moisture content. At this time, the soil moisture content reflects the water holding capacity of the soil. The overall trend of soil moisture content under different treatments over time is as follows Figure 3 shown.

[0092] The soil moisture content on the first day of different treatments was as follows: under the full-clay treatment, i.e., the clay-sand ratio of 1:0 (T1, T1B1, T1B2), the soil moisture content was 50%-55%; under the clay-sand ratio of 1:1 (T2, T2B1, T2B2), the soil moisture content was 35%-40%; under the clay-sand ratio of 1:2 (T3, T3B1, T3B2), the soil moisture content was 30%-35%; under the clay-sand ratio of 1:5 (T4, T4B1, T4B2), the soil moisture content was 30%-35%; under the full-sand treatment, i.e., the clay-sand ratio of 0:1 (T5, T5B1, T5B2), the soil moisture content was 25%-30%. It can be seen that under the full-clay treatment (T1, T1B1, T1B2), the soil moisture content of the reconstructed soil is the highest, and the soil moisture content decreases with the increase of sand content in the composite soil, indicating that clay has a good water-holding effect, while sand has a poor water-holding capacity. As the proportion of sand increases, the water-holding capacity of the reconstructed soil becomes less ideal.

[0093] from Figure 3 A clear trend can be seen: during the first three days of the experiment, regardless of soil composition, the measured moisture content showed a nearly V-shaped pattern. Soil moisture content in all treatments showed a rapid decline on the second day before recovering, and generally showed a steady downward trend by the fourth day. The all-sand treatments (T5, T5B1, and T5B2) showed the most pronounced decline on the second day, indicating that sandy soils have poor water retention and are unable to provide and maintain the moisture required for crop growth over the long term.

[0094] When the clay-sand ratio was 1:1 or 1:2 (T2 and T3), the effect of adding an isolation layer was not significant, and the trend of change was not clear. However, when the clay-sand ratio was 1:5 and the all-sand treatment was 1:5 (T4 and T5), the sand content was relatively high. As the sand content increased, the thicker the isolation layer, the higher the soil moisture content, and the more significant the effect. In the clay-sand ratio of 1:5 and the treatment with a 10cm water-retention layer (T4B2), the soil moisture content reached a maximum of 38.73% on the third day. This shows that the addition of an isolation layer can have a water-retention effect in treatments with a clay-sand ratio of 1:5 or above, that is, in reconstructed soils with a sand content of 83% or more, and the addition of a 10cm isolation layer has the best water-holding capacity.

[0095] (IV) Changes in vegetation biomass under different fertilization treatments under soil reconstruction model

[0096] from Figure 4 It can be seen that all fertilization treatments increased the biomass of plants. In fertilization treatment 1, that is, the ratio of fertilizer N:P:K=4:2:1, the biomass of plants was the highest, which was 56.45 g / m 2 , an increase of 85% compared to the no-fertilization treatment.

[0097] (V) Changes in plant biomass under different soil reconstruction treatments under fertilization patterns

[0098] from Figure 5 As can be seen, biomass in all treatments under fertilization (N:P:K = 4:2:1) was higher than that in the unfertilized treatment. Furthermore, under fertilization, the reconstructed soil with the isolation layer had relatively high vegetation biomass, and as the thickness of the isolation layer increased from 5 cm to 10 cm, the vegetation biomass also increased.

[0099] (V) Changes in soil nutrient content under different soil reconstruction treatments under fertilization patterns

[0100] Fertilization was performed using a mixed fertilizer of urea, superphosphate, and potassium sulfate with a ratio of N:P:K=4:2:1. The mixed fertilizer was evenly spread on the soil of the experimental group and stirred to mix thoroughly, and the soil nutrient content was monitored.

[0101] Nitrogen, phosphorus and potassium are essential nutrients for plant growth and development, and plants have high demands for them. Among them, nitrogen mainly affects the development of tree branches, leaves and fruits, phosphorus affects the number of female flowers, and potassium can promote the assimilation of leaves and the thickness of branches.

[0102] Soil quality is a comprehensive reflection of various soil properties (physical, chemical, and biological). Soil fertility is its essential attribute, the core foundation of soil quality, and one of the most important indicators for evaluating soil quality. Soil fertility includes both fully available and readily available components. Fully available components generally reflect the fertility characteristics of the soil, while readily available nutrients have a greater impact on short-term plant growth. Therefore, readily available nitrogen, readily available phosphorus, and readily available potassium were selected as indicators to reflect soil fertility.

[0103] Depend on Figures 6-8 As can be seen, the soils in the fully clayed soil treatments (T1, T1B1, and T1B2) had the highest levels of available nitrogen, available phosphorus, and available potassium, exceeding those in all other soil treatments. In the unfertilized soil treatment, soil nutrient content decreased with increasing sand content in the composite soil. Compared to soil samples without an isolation layer, soils with an isolation layer had higher nutrient contents than those without (T1, T2, T3, T4, and T5), indicating that the isolation layer has a nutrient-retaining effect on the soil.

[0104] Under the fertilization treatment, the soil nutrient content in the treatments with clay-sand ratios of 1:2 and 1:5 increased as the soil isolation layer increased from 5 cm to 10 cm, indicating that the fertility retention capacity of the reconstructed soil was increased when the isolation layer thickness was 10 cm.

[0105] The nutrient contents (available nitrogen, available phosphorus, and available potassium) of soil samples after fertilization increased compared to those in the unfertilized treatment. The highest nutrient contents were achieved in the treatment with a clay-sand ratio of 1:5 and a 10-cm water-retaining layer (T4B2), with available nitrogen at 44 mg / kg, available phosphorus at 69 mg / kg, and available potassium at 139 mg / kg. According to the soil nutrient content classification standard (Table 4), the abundance of available nitrogen increased from "very low" to "low," the abundance of available phosphorus increased from "medium-high" to "very high," and the abundance of available potassium increased from "medium" to "medium-high." Therefore, the fertilization effect was greatest in the treatment with a clay-sand ratio of 1:5 and a 10-cm water-retaining layer (T4B2), with soil nutrient contents increasing by 1-2 grades after fertilization.

[0106] Table 4 Soil nutrient content classification standards

[0107]

[0108] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A soil in-situ reconstruction method suitable for open-pit grassland mining areas, comprising the following steps: Step 1: Level and compact the surface of the spoil dump platform in the open-pit grassland mining area to form a subsoil layer; Step 2: continuously and evenly covering the subsoil layer with a layer of clay having a thickness of 5 to 10 cm as an isolation layer; Step 3: Covering the isolation layer with a reconstructed soil layer having a thickness of 15 to 20 cm, wherein the reconstructed soil layer is a mixture of sand and clay in a volume ratio of (1:2.5) to (1:5.5); The clay is clay associated with open-pit grassland mining areas.

2. The method according to claim 1, characterized in that The volume ratio of clay to sand in the reconstructed soil layer is 1:4 to 1:5, the thickness of the isolation layer is 8 to 10 cm, and the thickness of the reconstructed soil layer is 18 to 20 cm.

3. The method according to claim 2, characterized in that The volume ratio of clay to sand in the reconstructed soil layer is 1:5, the thickness of the isolation layer is 10 cm, and the thickness of the reconstructed soil layer is 20 cm.

4. The method according to any one of claims 1 to 3, characterized in that The method further includes step 4 of improving the reconstructed soil layer, including: Inorganic fertilizer consisting of quick-acting fertilizer and slow-release fertilizer is applied, wherein the mass ratio of N, P and K in the inorganic fertilizer is 4:2:

1. Apply organic materials sourced from local livestock and poultry manure, herbaceous plant straw or agricultural waste in the mining area.

5. The method according to claim 4, characterized in that In step 4, the soil is tilled to a depth of 20 cm by a deep tillage machine to evenly mix the inorganic fertilizer, organic material and the reconstructed soil layer.

6. A multi-dimensional soil improvement method suitable for open-pit grassland mining areas, characterized in that: include: Reconstructing platform soil using the method according to any one of claims 1 to 5; Slope soil reconstruction: Mix clay and sand in a volume ratio of 1:2 to form a reconstructed matrix, mix it with fertilizer, organic materials, and starch-branched adhesive, add water and stir into a paste, and spray it on the slope with a thickness of 15 to 20 cm.

7. The method according to claim 6, characterized in that include: Improve platform soil fertility: Apply quick-acting fertilizers, slow-release fertilizers and organic materials to the reconstructed platform soil; Platform micro-topography renovation: Use a bulldozer to level the platform and form a reverse slope, and then build a ridge or border structure.

8. The method according to claim 7, characterized in that The inorganic fertilizer formed by the quick-acting fertilizer and the slow-release fertilizer has a mass ratio of N, P, and K of 4:2:1, and the organic material comes from local livestock and poultry manure, herbaceous plant straw, or agricultural waste in the mining area.

9. The method according to claim 7, characterized in that The platform micro-topography renovation includes using a bulldozer or a leveler to level the platform surface so that the entire platform has a certain slope toward the dumping road, forming a reverse slope to prevent the platform water flow from eroding the dumping site slope.

10. The method according to any one of claims 7 to 9, characterized in that Then the platform surface is designed with grid ridges and ridges to achieve local leveling, and grid-type block interception is adopted.

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