Remediation method for soil in semi-arid region

Abstract

The invention provides a remediation method for soil in a semi-arid region, and belongs to the technical field of soil remediation. According to the remediation method for the soil in the semi-arid region, the physical structure of the soil is optimized through deep ploughing and rainwater collection, a straw matrix, the chemical environment is regulated and controlled through a composite conditioner, the biological function is enhanced through mixed sowing of local pioneer plants and a composite microbial agent, and a multi-dimensional synergistic remediation system is formed; local pioneer plants are selected, so that the invasion risk of alien species is avoided; natural materials such as degradable starch mulching film, decomposed straw and organic fertilizer are adopted and matched with the compound microbial agent, no chemical residue exists, local microbial community optimization can be promoted, and the stability of a soil ecological system can be improved; straw, cattle and sheep manure and other agricultural wastes are used for preparing a matrix and an organic fertilizer, and the raw material cost is reduced; the design of the rainwater collecting ditches is combined with natural rainwater resources, the manual irrigation cost is reduced, the soil ecosystem can be autonomously kept stable after remediation is completed, and secondary degradation is effectively avoided.

Description

A method for soil remediation in semi-arid regions Technical Field

[0001] This invention relates to the field of soil remediation technology, and more particularly to a method for remediating soil in semi-arid regions. Background Technology

[0002] The core climatic characteristics of semi-arid regions are annual precipitation of 200-450 mm, evaporation > precipitation, uneven spatial and temporal distribution of precipitation, distinct dry and wet seasons, and coexistence of wind and water erosion. This climate determines that the soil problems are multi-dimensional, superimposed, and causally related systemic problems, rather than single problems. The problems of soil in semi-arid regions include: (1) soil moisture shortage, extremely poor water retention capacity, and extremely low water utilization rate; (2) soil structure degradation, severe sandification and compaction, and a polarized texture of sandy / clay; (3) soil fertility deficiency, nutrient loss and ineffectiveness, and nutrient supply and demand imbalance; (4) intensified soil erosion (mainly wind erosion, supplemented by water erosion, wind-water combined erosion); (5) secondary soil salinization / salinization; (6) single soil microbial community and low activity.

[0003] Semi-arid regions commonly suffer from soil deficiencies, sandification and compaction, salinization, lack of organic matter, and low microbial activity, severely hindering agricultural production and ecological restoration. Existing soil remediation technologies for semi-arid regions revolve around four main objectives: water conservation, soil stabilization, fertilization, and salinity reduction, and are categorized into four main types: physical remediation, chemical remediation, bioremediation, and agronomic measures. However, each of these existing technologies has its own drawbacks. Physical remediation (such as soil improvement and mulching) suffers from high costs, residual pollution from mulch, and poor sustainability. Chemical remediation (such as the application of water-retaining agents and salinity-reducing agents) is prone to short-lived effects and overuse leading to soil ion imbalance. Bioremediation (such as planting pioneer plants and inoculating with microbial agents) faces bottlenecks such as poor compatibility of pioneer plants with the local ecosystem and difficulties in microbial colonization. Furthermore, existing technologies are often applied in isolation, lacking systematic and synergistic design, leading to secondary degradation of the remediated soil and making it difficult to achieve long-term stable remediation results. Therefore, there is an urgent need to develop a low-cost, residue-free, highly synergistic soil remediation method that is adapted to the environmental characteristics of semi-arid regions, in order to solve the core problems of existing technologies, such as single-function remediation, short-lived effects, and poor ecological compatibility. Summary of the Invention

[0004] The purpose of this invention is to provide a method for soil remediation in semi-arid regions. The remediation method provided by this invention is low-cost, residue-free, highly synergistic, and adapted to the environmental characteristics of semi-arid regions.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for soil remediation in semi-arid regions, comprising the following steps:

[0007] (1) After the soil in the semi-arid area to be restored thaws in spring, when the surface temperature of 5-10cm is stable above 5℃, the soil in the semi-arid area to be restored is deeply tilled to 35-45cm. During the deep tillage, horizontal rain collection ditches are opened at intervals of 20-30cm. After deep tillage, the soil is leveled and the first compound conditioner is sprayed on the surface to achieve the pretreatment of the soil in the semi-arid area to be restored.

[0008] (2) 3 to 5 days after the pretreatment of the soil in the semi-arid area to be restored in step (1) is completed, the top 0 to 20 cm of the soil in the semi-arid area to be restored is inoculated with compound microbial agent, and then the soil is shallowly tilled to a depth of 5 to 8 cm. 2 to 3 days after the inoculation, pioneer plants are mixed and sown, and then covered with 2 to 3 cm of straw fragments.

[0009] (3) During the seedling stage of the pioneer plants in step (2), spray the second compound conditioner and drip irrigate at the same time; during the growth period of the pioneer plants, apply decomposed organic fertilizer in the furrow every 45 to 60 days, combined with rainwater collection in the rainwater collection furrow and drip irrigation; the restoration cycle is 2 to 3 years, and soil indicators are tested every autumn. When the soil organic matter content is ≥1.5%, the salt content is ≤0.3%, the pH value is 6.5 to 8.0, and the microbial community richness is increased by more than 50% compared with before restoration, the vegetation coverage rate is increased to 75%, thus realizing the restoration of soil in semi-arid areas.

[0010] Preferably, in step (1), the depth of the rain collection ditch is 20-25cm, the width of the rain collection ditch is 30-40cm, and the bottom of the rain collection ditch is covered with a 5-8cm thick layer of decomposed straw substrate.

[0011] Preferably, the decomposed straw substrate is made by mixing and decomposing corn stalks, millet stalks and sheep manure for 60 to 90 days; the moisture content of the decomposed straw substrate is 25% to 30%.

[0012] Preferably, in step (1), the first composite conditioner is prepared by mixing humic acid, gypsum powder, and potassium polyacrylate, dissolving and diluting them in warm water; the application rate of the first composite conditioner is 150~200 kg / hm. 2 .

[0013] Preferably, in step (2), the compound microbial agent uses modified humic acid as a carrier and contains at least one of nitrogen-fixing bacteria, salt-tolerant phosphate-solubilizing bacteria, and yeast as the inoculant. During inoculation, the compound microbial agent is mixed with fine soil at a mass ratio of 1:5 and then applied. The inoculation amount of the compound microbial agent is 30-45 kg / hm². 2 .

[0014] Preferably, in step (2), the effective viable count of nitrogen-fixing bacteria in the compound microbial agent is ≥2.0 × 10⁻⁶. 9CFU / g, effective viable count of salt-tolerant phosphate-solubilizing bacteria ≥1.5×10⁻⁶ 9 CFU / g, effective viable yeast count ≥1.0×10⁻⁶ 9 CFU / g.

[0015] Preferably, in step (2), the pioneer plant mixed sowing is a mixture of at least two of the following: native white sheep grass seeds, native astragalus seeds, native February orchid seeds, and native Amorpha fruticosa seeds. The sowing rate of the pioneer plant mixed sowing is 30-45 kg / hm. 2 The sowing depth of the pioneer plant mixed sowing is 2-3 cm.

[0016] Preferably, in step (3), the drip irrigation maintains the soil moisture content at 40-50% of the field capacity, and the drip irrigation time is 10-15 days.

[0017] Preferably, the composted organic fertilizer in step (3) is composted cow or sheep manure, and the application rate of the composted organic fertilizer is 7500~15000 kg / hm. 2 When applying the well-rotted organic fertilizer in trenches, dig trenches 10-15cm away from the plant roots, with a trench depth of 10-15cm, and cover with soil after fertilization.

[0018] Preferably, in step (3), if the semi-arid area to be restored is a crop planting area, after the pioneer plants have grown for 1 year, a biodegradable starch film with a thickness of 0.012~0.015mm is used to cover the crop planting area, and the film coverage area accounts for 60%~70% of the restoration area; 15~20 days after the crops are harvested, the remaining film is recycled and crushed, and mixed with decomposed straw for the preparation of the substrate for the next round of restoration.

[0019] This invention provides a method for soil remediation in semi-arid regions. Through deep tillage and rainwater harvesting, along with straw substrate, the method optimizes the soil's physical structure. It regulates the chemical environment using compound conditioners, and enhances biological functions through mixed sowing of native pioneer plants and compound microbial agents, forming a multi-dimensional synergistic remediation system. This solves the problem of short-lived single-remediation effects in existing technologies. After remediation, the soil's water retention capacity increases by 40%–60%, salinity decreases by 35%–50%, organic matter content increases by 0.5%–1.0%, and microbial activity increases by over 50%. The use of native pioneer plants avoids the risk of invasive species. The use of biodegradable starch mulch, decomposed straw, organic fertilizer, and other natural materials, combined with compound microbial agents, leaves no chemical residues and promotes the optimization of native microbial communities, enhancing the stability of the soil ecosystem. The use of agricultural waste such as straw and cow / sheep manure to prepare substrate and organic fertilizer reduces raw material costs. The rainwater harvesting ditch design incorporates natural rainwater resources, reducing artificial irrigation costs. Through biological cycling, soil organic matter accumulation and nutrient transformation are achieved. After remediation, the soil ecosystem can autonomously maintain stability, effectively preventing secondary degradation. Furthermore, the method provided by this invention is adaptable to various semi-arid degraded soils such as sandy soil, saline-alkali soil, and barren soil, and can be used in ecological restoration areas and agricultural planting areas, making it easy to promote on a large scale. Attached Figure Description

[0020] Figure 1 is a schematic diagram of the principle of the soil remediation method for semi-arid regions provided by the present invention. Detailed Implementation

[0021] This invention provides a method for soil remediation in semi-arid regions, comprising the following steps:

[0022] (1) After the soil in the semi-arid area to be restored thaws in spring, when the surface temperature of 5-10cm is stable above 5℃, the soil in the semi-arid area to be restored is deeply tilled to 35-45cm. During the deep tillage, horizontal rain collection ditches are opened at intervals of 20-30cm. After deep tillage, the soil is leveled and the first compound conditioner is sprayed on the surface to achieve the pretreatment of the soil in the semi-arid area to be restored.

[0023] (2) 3 to 5 days after the pretreatment of the soil in the semi-arid area to be restored in step (1) is completed, the top 0 to 20 cm of the soil in the semi-arid area to be restored is inoculated with compound microbial agent, and then the soil is shallowly tilled to a depth of 5 to 8 cm. 2 to 3 days after the inoculation, pioneer plants are mixed and sown, and then covered with 2 to 3 cm of straw fragments.

[0024] (3) During the seedling stage of the pioneer plants in step (2), spray the second compound conditioner and drip irrigate at the same time; during the growth period of the pioneer plants, apply decomposed organic fertilizer in the furrow every 45 to 60 days, combined with rainwater collection in the rainwater collection furrow and drip irrigation; the restoration cycle is 2 to 3 years, and soil indicators are tested every autumn. When the soil organic matter content is ≥1.5%, the salt content is ≤0.3%, the pH value is 6.5 to 8.0, and the microbial community richness is increased by more than 50% compared with before restoration, the vegetation coverage rate is increased to 75%, thus realizing the restoration of soil in semi-arid areas.

[0025] Unless otherwise specified, all raw materials used in this invention are commercially available products in the art.

[0026] This invention involves deep tilling the soil in a semi-arid region to be restored to a depth of 35-45 cm after the soil thaws in spring and the surface temperature at a depth of 5-10 cm remains stable above 5°C. During deep tilling, transverse rainwater collection ditches are dug at intervals of 20-30 cm. After deep tilling, the soil is leveled and a first compound conditioner is sprayed onto the surface to achieve pretreatment of the soil in the semi-arid region to be restored.

[0027] This invention, through deep tillage, precisely breaks up the plow pan, increasing soil porosity (by 20-30%). This enhances rainwater infiltration and reduces surface runoff, while also providing space for plant roots to penetrate deeper, promoting deeper water absorption. In this invention, the depth of the rainwater collection ditch is preferably 20-25 cm, the width is preferably 30-40 cm, and the bottom of the ditch is preferably covered with a 5-8 cm thick layer of well-rotted straw substrate. This invention utilizes the rainwater collection ditch to quickly collect surface rainwater, reducing water loss, and the spacing ensures that rainwater evenly infiltrates the surrounding soil, avoiding localized waterlogging or drought. In this invention, the well-rotted straw substrate is preferably made from a mixture of corn stalks, millet stalks, and sheep manure, fermented for 60-90 days; the mass ratio of corn stalks, millet stalks, and sheep manure is (2-4):2:1; and the moisture content of the well-rotted straw substrate is preferably 25%-30%. This invention utilizes the fibrous structure of straw substrate to fill soil pores, improving soil aggregate stability and reducing wind and water erosion. The decomposed straw, rich in humus precursors, gradually decomposes to replenish soil organic matter. Simultaneously, the water-retention properties of straw increase the soil water holding capacity at the bottom of the ditch by 30-40%, forming a micro-water storage layer. The combination of corn and millet straw balances fiber toughness and decomposition rate (corn straw is tough but decomposes slowly, while millet straw decomposes quickly, balancing long-term soil stabilization and short-term fertilization). Adding sheep manure introduces microorganisms and readily available nutrients, accelerating straw decomposition. Through the combination of deep plowing, rainwater collection ditches, and straw substrate, this invention optimizes soil physical structure, initially improves water retention capacity, reduces the risk of wind and water erosion, and allows the straw substrate to slowly decompose, replenishing the soil with organic matter and laying the foundation for soil fertility. In this invention, the first composite conditioner is preferably prepared by mixing humic acid, gypsum powder, and potassium polyacrylate, dissolving and diluting them in warm water. More preferably, it is prepared by mixing humic acid, gypsum powder with a particle size of 100-120 mesh, and potassium polyacrylate with a molecular weight of 20 million-30 million in a mass ratio of (4-7):(1-4):2, and then dissolving and diluting it 50 times in warm water at 30-40°C. In this invention, the preferred application rate of the first composite conditioner is 150-200 kg / hm². 2 This invention balances the effects of salinization, water retention, and soil stabilization by adjusting the composition and application amount of the first composite conditioner. Humic acid plays a leading role in colloidal modification, gypsum powder plays a leading role in salinization, and potassium polyacrylate plays a leading role in water retention, thus synergistically improving soil environmental suitability.

[0028] After pretreatment, 3-5 days after the pretreatment of the soil in the semi-arid region to be restored, the present invention inoculates the top 0-20cm of the soil in the semi-arid region to be restored with a compound microbial agent, and then shallowly tills the soil to a depth of 5-8cm; 2-3 days after inoculation, pioneer plants are mixed and sown, and then covered with 2-3cm of straw fragments.

[0029] This invention involves inoculating the soil with a compound microbial agent 3-5 days after pretreatment. Pretreatment increases soil porosity and moisture content, and initially reduces salinity. The 3-5 day interval allows for soil environmental stabilization, preventing the high concentration of residual ions from the conditioner from inhibiting microorganisms and improving their survival rate. In this invention, the compound microbial agent preferably uses modified humic acid as a carrier and contains at least one of nitrogen-fixing bacteria, salt-tolerant phosphate-solubilizing bacteria, and yeast. During inoculation, the compound microbial agent is mixed with fine soil at a mass ratio of 1:5 and then applied. The preferred inoculation rate of the compound microbial agent is 30-45 kg / hm². 2 In this invention, the effective viable count of nitrogen-fixing bacteria in the compound microbial agent is preferably ≥2.0 × 10⁻⁶. 9 CFU / g, with an optimal effective viable count of salt-tolerant phosphate-solubilizing bacteria ≥1.5×10⁻⁶. 9 CFU / g, preferably ≥1.0×10⁻⁶ effective viable yeast cells. 9 CFU / g. This invention, through inoculation with a compound microbial agent, facilitates the increase of readily available nutrients such as nitrogen and phosphorus in the soil, enhances the richness of the microbial community, strengthens the soil's material cycling capacity, and provides nutritional support for the growth of pioneer plants. In this invention, the pioneer plant mixed sowing involves the mixing of at least two of the following: native white sheepgrass seeds, native astragalus seeds, native February orchid seeds, and native Amorpha fruticosa seeds; the preferred sowing rate for the pioneer plant mixed sowing is 30-45 kg / hm². 2 The preferred sowing depth for the pioneer plant mixed sowing is 2-3 cm. This invention uses native species to avoid the risk of invasive species, and the mixed sowing can form a three-dimensional root structure, improving soil retention capacity. At the same time, the nutrient requirements of different plants are complementary, avoiding excessive consumption of certain nutrients by a single plant. The mixed sowing can ensure the soil-fixing effect of the dominant species, while at least two of the native white sheep grass seeds, native astragalus seeds, native February orchid seeds, and native Amorpha fruticosa seeds can improve coverage and nutrient supply. Furthermore, after the pioneer plants are mixed sown, they quickly form surface cover, reducing wind and water erosion. The synergistic effect of plant roots and microorganisms further improves soil fertility and aggregate stability, and the soil ecosystem begins to reconstruct.

[0030] After the pioneer plants are sown together, this invention sprays a second compound conditioner during the seedling stage of the pioneer plants, while simultaneously supplementing water through drip irrigation. During the growth period of the pioneer plants, well-rotted organic fertilizer is applied in furrows every 45-60 days, combined with rainwater collection in drainage ditches and supplementing water through drip irrigation. The restoration cycle is 2-3 years. Soil indicators are tested every autumn. When the soil organic matter content is ≥1.5%, the salt content is ≤0.3%, the pH value is 6.5-8.0, and the microbial community richness is increased by more than 50% compared with before restoration, the vegetation coverage rate is increased to 75%, thus achieving soil restoration in semi-arid areas.

[0031] In this invention, the emergence period of the pioneer plant is preferably 15-20 days after sowing. In this invention, the drip irrigation to maintain soil moisture content is preferably 40-50% of field capacity; the drip irrigation period is preferably 10-15 days. This invention utilizes drip irrigation to precisely control soil moisture content at 40-50%, and maintaining this level for 10-15 days ensures successful seedling rooting and avoids a decrease in emergence rate due to drought. In this invention, the growth period of the pioneer plant is preferably from 30 days after emergence to autumn of the same year. In this invention, during the growth period of the pioneer plant, rainwater is preferably collected through drainage ditches and supplemented with drip irrigation according to soil moisture conditions to maintain soil moisture content at 30-40% (dry period) or 50-60% (vigorous growth period) of field capacity. This invention controls soil moisture content at 30-40% during dry periods (such as summer) to avoid excessive water consumption and stimulate plant roots to absorb water from deeper layers; during vigorous growth periods (such as spring and autumn), it controls it at 50-60% to meet the water requirements of plant growth; combined with rainwater collection ditches, it can make full use of natural water resources and reduce irrigation costs. In this invention, the decomposed organic fertilizer is preferably decomposed cow or sheep manure, and the preferred application rate of the decomposed organic fertilizer is 7500-15000 kg / hm². 2 When applying the well-rotted organic fertilizer in trenches, dig trenches 10-15cm away from the plant roots, with a depth of 10-15cm, and cover with soil after application. This invention utilizes well-rotted organic fertilizer to enhance soil aggregate stability while providing comprehensive nutrients (nitrogen, phosphorus, potassium, and trace elements), avoiding the side effects of chemical fertilizers. The trench application method allows for precise application of organic fertilizer around the roots, improving nutrient absorption efficiency while avoiding direct contact with the roots and preventing root burn. The interval between trench applications matches the plant growth cycle (approximately 45 days between the rapid growth periods of the three plant species), ensuring a continuous supply of nutrients. Furthermore, this invention utilizes segmented water and fertilizer regulation to ensure the continuous growth of pioneer plants and microorganisms, steadily increasing soil organic matter content and further enhancing water retention and nutrient supply capabilities. In this invention, if the semi-arid area to be restored is a crop-growing area, after one year of pioneer plant growth, a biodegradable starch mulch film with a thickness of 0.012-0.015 mm is preferably used to cover the crop planting area, with the mulch film covering 60%-70% of the restoration area. 15-20 days after crop harvest, the remaining film is collected, crushed, and mixed with decomposed straw for use in the preparation of the substrate for the next round of restoration. This invention utilizes biodegradable mulch film to ensure water and heat retention in the crop planting area while avoiding environmental pollution; the recycling of the remaining film further enhances the sustainability of the restoration and reduces raw material costs.

[0032] The remediation method provided in this application works synergistically from physical, chemical, and biological perspectives. Pretreatment establishes the physical foundation through deep tillage and straw substrate, while compound conditioners improve the chemical environment. Biofortification enhances nutrient supply and ecological reconstruction through microbial-plant synergy. Post-treatment maintenance maintains environmental suitability through water and fertilizer regulation and achieves sustainability through recycling. The parameters of each step are precisely matched to the soil characteristics and climatic conditions of semi-arid regions, ultimately achieving a comprehensive technical effect of improving soil water retention capacity, organic matter, and microbial activity, while reducing salinity. At the same time, the cost is controllable, there are no environmental residues, and it is suitable for large-scale implementation.

[0033] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] Figure 1 is a schematic diagram illustrating the principle of the soil remediation method for semi-arid regions provided by this invention. In this invention, pretreatment establishes the physical basis through deep tillage and straw substrate, while compound conditioners improve the chemical environment; biofortification enhances nutrient supply and ecological reconstruction through microbial-plant synergy; post-treatment maintenance maintains environmental suitability through water and fertilizer regulation, and achieves sustainability through recycling; the parameters of each step are precisely matched to the soil characteristics and climatic conditions of semi-arid regions, ultimately achieving a comprehensive technical effect of improving soil water retention capacity, organic matter, and microbial activity, while reducing salinity. Simultaneously, the cost is controllable, there are no environmental residues, and it is suitable for large-scale implementation.

[0035] Unless otherwise specified, all experiments were repeated three times, and the results are expressed as averages.

[0036] Example 1

[0037] The soil indicators of the semi-arid desertified area to be restored before restoration were as follows: soil organic matter content 0.6%, salt content 0.8%, pH value 8.8, soil moisture content 12%, and vegetation coverage less than 20%.

[0038] A method for soil remediation in semi-arid regions, comprising the following steps:

[0039] (1) In late March, the surface temperature of the semi-arid desertified area to be restored was stabilized at 5℃. The soil was deep-plowed to 40cm, and transverse rain collection ditches were opened every 25cm. The depth of the rain collection ditches was 22cm and the width of the rain collection ditches was 35cm. A 6cm thick layer of decomposed straw substrate was laid at the bottom of the ditches. After leveling the soil, the first compound conditioner was sprayed to achieve the pretreatment of the soil in the semi-arid area to be restored.

[0040] The decomposed straw substrate is prepared by mixing corn straw, millet straw, and sheep manure in a mass ratio of 3:2:1 and decomposing for 75 days while maintaining a moisture content of 28%. The preparation steps of the first composite conditioner are as follows: humic acid, gypsum powder with a particle size of 100-120 mesh, and potassium polyacrylate with a molecular weight of 20 million are mixed in a mass ratio of 5:3:2 and dissolved and diluted 50 times with warm water at 35℃ to obtain the first composite conditioner. The spraying rate of the first composite conditioner is 180 kg / hm². 2 ;

[0041] (2) Four days after the pretreatment in step (1), the surface layer of the semi-arid desertified area to be restored is inoculated with compound microbial agent in 5cm. The compound microbial agent is mixed with fine soil at a mass ratio of 1:5 and then spread and shallowly tilled to 6cm. Three days after inoculation, native white sheep grass seeds and native purple locust seeds are sown together at a sowing rate of 38kg / hm. 2 Sowing depth is 2.5cm, covered with 2.5cm of straw fragments;

[0042] The composite microbial agent consists of a modified humic acid carrier and a microbial agent in a mass ratio of 4:1; the effective viable count of nitrogen-fixing bacteria in the composite microbial agent is 2.5 × 10⁻⁶. 9 CFU / g, the effective viable count of salt-tolerant phosphate-solubilizing bacteria is 1.8 × 10⁻⁶. 9 CFU / g, effective viable yeast count is 1.2 × 10⁻⁶. 9 CFU / g; the inoculation amount of the compound microbial agent is 38 kg / hm. 2 The mass ratio of native white sheep grass seeds to native purple acacia seeds is 2:1.

[0043] (3) In step (2), 18 days after sowing (seedling stage), spray the second compound conditioner; drip irrigation is used to supplement water and maintain the soil moisture content at 45% for 12 days; starting 30 days after emergence, apply well-rotted cow and sheep manure in furrows every 50 days at a rate of 12,000 kg / hm. 2 Rainwater is collected through drainage ditches to maintain soil moisture content at 35% during dry periods and 55% during periods of vigorous growth.

[0044] The preparation steps of the second composite conditioner are as follows: Humic acid, gypsum powder with a particle size of 100-120 mesh, and potassium polyacrylate with a molecular weight of 20 million are mixed at a mass ratio of 5:3:2, and dissolved and diluted 80 times with warm water at 35℃ to obtain the second composite conditioner; the spraying rate of the second composite conditioner is 120 kg / hm². 2 ;

[0045] Two years after remediation, the soil indicators tested in the fall were as follows: soil organic matter content increased to 1.6%, salt content decreased to 0.25%, pH value was 8.0, soil water retention capacity increased to 52%, microbial community richness increased to 65%, and vegetation coverage increased to 75%, achieving a stable remediation effect.

[0046] Example 2:

[0047] The semi-arid saline-alkali farmland to be restored had the following soil indicators before restoration: soil organic matter content 0.8%, salt content 1.0%, pH value 9.0, soil moisture content 15%, and wheat was the main crop.

[0048] A method for soil remediation in semi-arid regions, comprising the following steps:

[0049] (1) In early April, the surface temperature of the semi-arid saline-alkali farmland to be restored was stabilized at 5℃. The soil was deep-plowed to 45cm, and transverse rain collection ditches were opened every 30cm. The depth of the rain collection ditches was 25cm and the width of the rain collection ditches was 40cm. An 8cm thick layer of decomposed straw substrate was laid at the bottom of the rain collection ditches. After leveling the soil, the first compound conditioner was sprayed to achieve the pretreatment of the soil in the semi-arid area to be restored.

[0050] The decomposed straw substrate is prepared by mixing corn straw, millet straw, and sheep manure in a mass ratio of 4:2:1 and decomposing for 75 days while maintaining a moisture content of 30%. The preparation steps of the first composite conditioner are as follows: humic acid, gypsum powder with a particle size of 100-120 mesh, and potassium polyacrylate with a molecular weight of 20 million are mixed in a mass ratio of 5:3:2 and dissolved and diluted 50 times with warm water at 40℃ to obtain the first composite conditioner. The spraying rate of the first composite conditioner is 200 kg / hm². 2 ;

[0051] (2) Five days after the pretreatment in step (1), inoculate with compound microbial agent at a rate of 45 kg / hm. 2 Mix the seed coat with fine soil at a ratio of 1:5 and spread it, then lightly till it to a depth of 8 cm. Two days after inoculation, sow a mixture of native white sheepgrass seeds, native astragalus seeds, and native purple locust seeds at a rate of 45 kg / hm². 2 Sow at a depth of 3cm and cover with 3cm of straw fragments;

[0052] The composite microbial agent consists of a modified humic acid carrier and a microbial agent in a mass ratio of 4:1; the effective viable count of nitrogen-fixing bacteria in the composite microbial agent is 2.5 × 10⁻⁶. 9 CFU / g, the effective viable count of salt-tolerant phosphate-solubilizing bacteria is 1.8 × 10⁻⁶. 9 CFU / g, effective viable yeast count is 1.2 × 10⁻⁶. 9 CFU / g; The mass ratio of native white sheep grass seeds, native astragalus seeds, and native purple acacia seeds was 2:1:1;

[0053] (3) In step (2), 20 days after sowing (seedling stage), spray the second compound conditioner; drip irrigation is used to supplement water and maintain the soil moisture content at 50% for 15 days; starting from 30 days after emergence, apply well-rotted cow and sheep manure in furrows every 60 days at a rate of 15,000 kg / hm. 2 One year after the pioneer plants have grown (in the spring of the second year), a 0.015 mm thick biodegradable starch film is laid in the wheat planting belt, covering an area of ​​65%. Eighteen days after the wheat harvest, the film has a natural degradation rate of 88%. The remaining film is mechanically collected, crushed, and used for the next round of straw substrate preparation.

[0054] The preparation steps of the second composite conditioner are as follows: Humic acid, gypsum powder with a particle size of 100-120 mesh, and potassium polyacrylate with a molecular weight of 20 million are mixed at a mass ratio of 7:3:2, and dissolved and diluted 80 times with warm water at 35℃ to obtain the second composite conditioner; the spraying rate of the second composite conditioner is 150 kg / hm². 2 ;

[0055] Three years after the restoration, the soil indicators tested in the fall were as follows: soil organic matter content increased to 1.8%, salinity decreased to 0.22%, pH value was 7.8, soil water retention capacity increased to 60%, microbial community richness increased by 70%, wheat yield increased by 45% compared with before the restoration, and the soil ecosystem was stable.

[0056] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for remediating soil in semi-arid regions, characterized in that, Includes the following steps: (1) After the spring thaw, when the temperature at the surface of the semi-arid area to be restored is stable above 5℃ at 5-10cm, the soil in the semi-arid area to be restored is deeply tilled to 35-45cm. During the deep tillage, transverse rainwater collection ditches are opened at intervals of 20-30cm. After deep tillage, the soil is leveled and the first compound conditioner is sprayed on the surface to achieve pretreatment of the soil in the semi-arid area to be restored; (2) 3-5 days after the pretreatment of the soil in the semi-arid area to be restored in step (1) is completed, compound microbial agents are inoculated into the surface layer of the soil in the semi-arid area to be restored at 0-20cm. After inoculation, the soil is shallowly tilled to 5-8cm. 2-3 days after inoculation, the soil is then subjected to further treatment. (2) Spray the second compound conditioner during the seedling stage of the pioneer plants in step (2) and simultaneously drip irrigation; during the growth period of the pioneer plants, apply decomposed organic fertilizer every 45 to 60 days, combined with rainwater collection in the rain collection ditch and drip irrigation; the restoration cycle is 2 to 3 years, and the soil indicators are tested every autumn. When the soil organic matter content is ≥1.5%, the salt content is ≤0.3%, the pH value is 6.5 to 8.0, and the microbial community richness is increased by more than 50% compared with before restoration, the vegetation coverage rate is increased to 75%, thus realizing the restoration of soil in semi-arid areas.

2. The method for remediating soil in semi-arid regions according to claim 1, characterized in that, In step (1), the depth of the rain collection ditch is 20-25cm, the width of the rain collection ditch is 30-40cm, and the bottom of the rain collection ditch is covered with a 5-8cm thick layer of decomposed straw substrate.

3. The method for remediating soil in semi-arid regions according to claim 2, characterized in that, The decomposed straw substrate is made by mixing corn stalks, millet stalks and sheep manure and decomposing them for 60 to 90 days; the moisture content of the decomposed straw substrate is 25% to 30%.

4. The method for remediating soil in semi-arid regions according to claim 1, characterized in that, In step (1), the first composite conditioner is prepared by mixing humic acid, gypsum powder, and potassium polyacrylate, dissolving and diluting them in warm water; the application rate of the first composite conditioner is 150~200 kg / hm. 2 .

5. The method for remediating soil in semi-arid regions according to claim 1, characterized in that, In step (2), the compound microbial agent uses modified humic acid as a carrier and contains at least one of nitrogen-fixing bacteria, salt-tolerant phosphorus-solubilizing bacteria, and yeast as the inoculant. During inoculation, the compound microbial agent is mixed with fine soil at a mass ratio of 1:5 and then applied. The inoculation amount of the compound microbial agent is 30-45 kg / hm². 2 .

6. The method for remediating soil in semi-arid regions according to claim 1 or 5, characterized in that, In step (2), the effective viable count of nitrogen-fixing bacteria in the compound microbial agent is ≥2.0 × 10⁻⁶. 9 CFU / g, effective viable count of salt-tolerant phosphate-solubilizing bacteria ≥1.5×10⁻⁶ 9 CFU / g, effective viable yeast count ≥1.0×10⁻⁶ 9 CFU / g.

7. The method for remediating soil in semi-arid regions according to claim 1, characterized in that, In step (2), the pioneer plant mixed sowing involves at least two of the following: native white sheep grass seeds, native astragalus seeds, native February orchid seeds, and native Amorpha fruticosa seeds. The sowing rate of the pioneer plant mixed sowing is 30-45 kg / hm². 2 The sowing depth of the pioneer plant mixed sowing is 2-3 cm.

8. The method for remediating soil in semi-arid regions according to claim 1, characterized in that, In step (3), drip irrigation is used to maintain soil moisture content at 40% to 50% of field capacity, and the drip irrigation time is 10 to 15 days.

9. The method for remediating soil in semi-arid regions according to claim 1, characterized in that, In step (3), the composted organic fertilizer is composted cow and sheep manure, and the application rate of the composted organic fertilizer is 7500~15000 kg / hm. 2 When applying the well-rotted organic fertilizer in trenches, dig trenches 10-15cm away from the plant roots, with a trench depth of 10-15cm, and cover with soil after fertilization.

10. The soil remediation method for semi-arid regions according to claim 1, characterized in that, In step (3), if the semi-arid area to be restored is a crop planting area, after the pioneer plants have grown for 1 year, a biodegradable starch film with a thickness of 0.012~0.015mm is used to cover the crop planting area, and the film coverage area accounts for 60%~70% of the restoration area; 15~20 days after the crops are harvested, the remaining film is recycled and crushed, and mixed with decomposed straw for the preparation of the substrate for the next round of restoration.

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