Desertification soil water retention and structure modification and method

Abstract

The present application relates to a kind of desertification soil water-retention structure and method, including frame, and first sand layer, water-retention layer, second sand layer, surface reinforcement layer and one-way water guide component are sequentially arranged from bottom to top in frame;The first sand layer includes sand and graphite powder with mass ratio of 1 :(0.005-0.03);The water-retention layer includes organic compost and water-retaining agent with mass ratio of 1 :(0.05-0.2);The second sand layer includes sand and bentonite with mass ratio of 1 :(0.005-0.05);The surface reinforcement layer includes fly ash, sand and hardened granules obtained by granulating concrete with mass ratio of (3-5) :(4-6) :1;The one-way water guide component includes multiple hook type hollow tubes.The present application constructs a specific chemical component spatial distribution, forms a physical space with super water-retention for plant root system.Compared with prior art, the present application has the advantages of strong wind and sand resistance, high raw material utilization rate, convenient pouring water, good water-retention improvement performance, remarkable desertification control effect and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of soil improvement and remediation, and particularly relates to a desertification soil water-retention improvement structure and method. BACKGROUND

[0002] It is very important to improve the water-holding capacity of soil, improve the composition and trace elements of soil, reduce soil wind erosion, and provide a good soil environment for plants by using soil improvers. CN114874054A discloses a desert sand soil improver and its preparation method and application, which mainly uses the solid waste fly ash of a thermal power plant to improve the mechanical composition of soil, reduce the soil bulk density, and supplement the missing trace elements of soil. However, the fly ash is still in powder form, has low bulk density, and weak wind and sand resistance. CN212876843U discloses a soil improvement structure suitable for vegetation planting, which improves the soil by reconstructing the soil profile structure to enhance the water-retention and fertilizer-retention effects of the soil. The upper black soil layer, the middle clay layer, and the lower black soil layer are connected by cotton threads. However, the desertification sandy soil has poor adhesion and water-retention performance, and the cotton threads in the middle increase the evaporation of water. CN114806590A discloses a soil ecological improvement composition and its preparation method, which uses organic compost, microbial fertilizer, water-retention agent, and biochar powder to prepare the soil ecological improvement composition. However, the raw materials are mixed together, which results in waste of raw materials and unsatisfactory water-retention improvement performance. SUMMARY

[0003] The present application is to overcome the defects of the prior art, and provides a desertification soil water-retention improvement structure and method to overcome the problems of low bulk density, weak wind and sand resistance, waste of raw materials, and unsatisfactory water-retention improvement performance.

[0004] The purpose of the present application can be achieved by the following technical solution: a desertification soil water-retention improvement structure, characterized in that it comprises a surrounding frame and a first sandy soil layer, a water-retention layer, a second sandy soil layer, and a surface strengthening layer arranged in the surrounding frame from bottom to top, and further comprises a one-way water guide assembly. The first sandy soil layer comprises sand and graphite powder with a mass ratio of 1:(0.005-0.03). The water-retention layer comprises organic compost and water-retention agent with a mass ratio of 1:(0.05-0.2). The second sandy soil layer comprises sand and bentonite with a mass ratio of 1:(0.005-0.05). The surface strengthening layer comprises fly ash, sand, and hardened particles obtained by granulating concrete with a mass ratio of (3-5):(4-6):1. The one-way water guide assembly comprises a plurality of hook-shaped hollow tubes, which are convenient for irrigation and can prevent water evaporation. A specific chemical composition spatial distribution is constructed to form a physical space with super water-retention for plant roots.

[0005] The graphite powder in the first sand layer has excellent thermal conductivity, with a thermal conductivity of 116-200 W / (m·K), higher than that of iron (80 W / (m·K)), and has the characteristics of stable properties, no odor, non-toxic and harmless. The graphite powder uniformly doped in the first sand layer can effectively conduct root heat, reduce root temperature, inhibit water evaporation, and help maintain the water content in the sand.

[0006] The bentonite in the second sand layer has the characteristics of dispersibility, hygroscopicity and adhesion, and plays a role in increasing the porosity of sand and improving the soil structure. When the lower layer of water vapor transpires upward, the bentonite uniformly dispersed in the second sand layer expands when it meets water vapor, hindering the upward diffusion of water vapor.

[0007] The organic compost material includes fermented and decomposed straw, grain husk or livestock manure.

[0008] The water-retaining agent is prepared by mixing grain husk, acrylic acid and fly ash in a mass ratio of 1:(10-70):(0.1-5) under a nitrogen atmosphere at 35-75°C, using potassium persulfate as an initiator and N,N-methylene bisacrylamide as a crosslinking agent. The initiator is added in an amount of 0.01-0.2 times the mass of the grain husk, and the crosslinking agent is added in an amount of 0.01-0.05 times the mass of the grain husk.

[0009] Potassium persulfate is easily decomposed by heat into sulfate radicals SO4 - with a high oxidation-reduction potential. These radicals react with the hydroxyl groups in the grain husk to form alkoxy groups on the grain husk skeleton, which then react with acrylic acid to form new polymer chains, and combine with adjacent radicals to form crosslinked chains. The Ca, Mg, K and Na cations in the fly ash neutralize the acrylic acid to form neutral Ca / Mg / K / Na salts of acrylic acid. Under the action of the crosslinking agent N,N-methylene bisacrylamide, the active silanol groups in the fly ash participate in the graft copolymerization reaction, and polymerize around the grain husk fragments to form a three-dimensional network structure containing a large number of water-retaining spaces that can absorb and store water, forming an efficient and economical water-retaining system.

[0010] The grain husk used in the organic compost material and the water-retaining agent includes quinoa husk, wheat husk, rice husk, sorghum husk or bean husk.

[0011] The hardening particles in the surface reinforcement layer are obtained by mixing fly ash, sand and concrete, using the alkaline substances Ca, Mg and Al in the fly ash to undergo condensation and solidification reactions with the active Si in the concrete, and coating and solidifying the sand to prevent sand from moving. The mixture is then mixed with water to adjust the mass ratio of water to mixture to (0.4-0.5):1, and then allowed to stand at 20-30°C at a stirring speed of 400-500 r·min-1 The speed stirring 1~30min, prevent completely solidified, control the main particle size between 2~10mm.

[0012] The surface reinforcement layer includes the hardened particles obtained by granulating fly ash, sand and concrete, and the sand mixed according to the mass ratio (0.5~2):1.

[0013] The frame is woven by straw, and the straw includes any one or combination of rice straw or wheat straw.

[0014] The first sand layer in the frame is 5~10cm thick, the water retaining layer is 20~30cm thick, the second sand layer is 5~10cm thick, and the surface reinforcement layer is 10~20cm thick.

[0015] The lower end of the hook-shaped hollow pipe is inserted into the water retaining layer, and the upper end is protruded from the soil and flush with the surface of the surface reinforcement layer, so that the snow, rain and irrigation water on the soil surface can be freely guided to the plant root system in the deep soil and continuously stored in the water retaining layer; the lower part is hook-shaped, and the hook section forms an upward 30°~70° angle with the horizontal plane, which is beneficial to the water in the water retaining layer not being easily migrated upward and evaporated.

[0016] The application also provides a method for improving desertification soil by using the structure, which comprises the following steps:

[0017] (1) weaving a frame by straw;

[0018] (2) arranging the frame around and at the bottom of the sand;

[0019] (3) arranging the frame into a first sand layer, a water retaining layer, a second sand layer and a surface reinforcement layer from bottom to top, and combining the frame and the surface reinforcement layer into a three-dimensional comprehensive protection shell of the internal water-containing soil;

[0020] (4) arranging a one-way water guiding assembly, including the lower end of a plurality of hook-shaped hollow pipes being buried in the water retaining layer, the upper end being protruded from the soil and flush with the surface of the surface reinforcement layer, and the bottom hook forming an upward 30°~70° angle with the horizontal plane.

[0021] Compared with the prior art, the application has the following beneficial effects:

[0022] (1) The application adopts the reaction of grain husks, potassium persulfate, acrylic acid, fly ash and N,N-methylene bisacrylamide under specific conditions, the Ca, Mg, K, Na and other cations in fly ash neutralize with acrylic acid to form neutral Ca / Mg / K / Na salt of acrylic acid. Under the action of N,N-methylene bisacrylamide as crosslinking agent, the active silanol groups in fly ash participate in graft copolymerization reaction, and polymerize into three-dimensional network structure around grain husk fragments, which contains a large number of water storage space and can absorb and store water to form an efficient and economical water retaining system. Fly ash can reduce the cost of water retaining agent on the one hand, and can fully exert the self-benefits of fly ash on the other hand. In addition, the addition of the obtained water retaining agent makes the organic compost material needed for plant growth uniformly dispersed, slowly releases water and nutrients in the process of seed germination, emergence and growth, plays the role of "micro reservoir" and "nutrient reservoir", and has a long-lasting effect. The low-cost mineral composite water retaining agent has multiple functions such as drought resistance, water saving, fertilizer preservation, yield increase, heat preservation, seedling protection and the like, and greatly enhances the survival rate of plants.

[0023] (2) The application sets up sand layers above and below the water retaining layer. The sand layer below the water retaining layer is mixed with graphite powder, which has excellent heat conduction performance and can cool the roots of plants and condense water vapor. The sand layer above the water retaining layer is mixed with bentonite, which can quickly absorb moisture and expand when encountering upwardly migrating transpiration water vapor, and its adhesion makes the upper loose sand layer relatively compact, thereby inhibiting water evaporation, dust raising and wind erosion.

[0024] (3) The application adopts a special surface strengthening layer, which granulates fly ash, sand and concrete. Fly ash is stable in nature and contains a large amount of silicon dioxide, aluminum oxide and other metal oxides. After mixing with sand and concrete, it can form hardened particles with hard texture, which are permeable to water and air and are not easy to be eroded into powder.

[0025] (4) The application uses straw weaving to protect the improved sand. The four sides and the bottom of the frame can exchange water and air with the sand, and also have a certain supporting effect. The sand and the modifier in the frame are respectively the first sand layer, the water retaining layer, the second sand layer and the surface strengthening layer from bottom to top. The frame and the hardened surface strengthening layer on the top form a three-dimensional comprehensive protective shell containing water-containing soil inside. The application of the hook-shaped hollow tube as a one-way water guide assembly in soil improvement and irrigation has not been reported. The assembly makes it easy for water in the external environment to enter the protective shell, while the evaporation process from the inside to the outside is inhibited, and the soil permeability is not affected in the process of one-way water guide, providing a good ventilation and moisture retention environment for plant growth. The water retaining layer is composed of organic compost material and water retaining agent, forming a stable water retaining layer protected by the four sides. The surface strengthening layer is granulated with fly ash, sand and concrete, and after granulation, it is mixed with sand at a mass ratio of (0.5-2):1 to increase the wind and sand resistance.

[0026] (5) This invention constructs a unique spatial distribution of chemical components, forming a physical space with super-strong water retention for plant roots: ① The surface reinforcement layer uses locally sourced materials, including sand, concrete, and fly ash from industrial and mining waste, to make hardened particles, maintaining good water and air permeability of the sand and strengthening the protection of the underlying soil; ② The lower sand layer improves soil structure by adding bentonite, blocking the upward movement of residual water in the lower water-retaining layer, inhibiting water loss from the soil surface, and providing an additional protective barrier for water at the plant roots; ③ The middle water-retaining layer contains water-retaining agents and nutrients required by plants, serving as an important site for plant root growth. A specially structured hollow bend inserted into the water-retaining layer provides an important channel for water acquisition; ④ The sand layer below the water-retaining layer, by adding graphite ash, can quickly lower the root temperature, inhibit water evaporation, and allow more water to be retained near the roots; ⑤ The design of the hook-shaped hollow tube has not been reported in soil improvement. It can utilize agricultural waste straw to unidirectionally introduce water into the water-retaining layer, providing a direct channel for water supply to the water-retaining layer, and inhibiting the outflow of excess water from the water-retaining layer; ⑥ The use of the enclosure frame is adapted to local conditions, utilizes agricultural waste, and has a certain water and fertilizer retention effect. The internal structure of the enclosure frame has a good water storage and retention function. The outer enclosure frame and the surface reinforcement layer cover the sand like a bun, which plays a role in sand fixation and water retention, while also having the air permeability required for plant growth. It can improve the soil's resistance to wind erosion, water retention and fertilizer retention in a three-dimensional, economical and efficient manner. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the desertification soil water retention improvement structure of the present invention. Detailed Implementation

[0028] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. The sand used in this invention originates from aeolian sand deposited in the Qinghai Lake desert, with a density of 1.5 g / cm³. 3 The fly ash used is sourced from waste fly ash from a power plant in Ningxia, with a density of 1.8 g / cm³. 3 The graphite powder used was a commercially available AR-grade product from Sinopharm Chemical Reagent Co., Ltd.; the bentonite used had a particle size of 0–50 μm and a density of 1.1 g / cm³. 3 The organic composted materials of this invention are prepared using conventional composting methods in the art. For example, the fermented and composted straw and grain husks used in the following embodiments are prepared in accordance with the local standard "Technical Specification for Aerobic Composting of Rice Straw" implemented on April 1, 2021; the fermented and composted poultry and livestock manure used in the following embodiments are prepared in accordance with the industry standard "Technical Specification for Composting of Livestock and Poultry Manure" implemented on September 1, 2019.

[0029] Example 1:

[0030] A structural form for improving water retention in desertified soils, such as Figure 1 As shown, the structure includes a straw-woven frame 1; a first sand layer 2 with a thickness of 10cm; a water-retaining layer 3 with a thickness of 20cm; a second sand layer 4 with a thickness of 5cm; and a surface reinforcement layer 5 with a thickness of 20cm. The unidirectional water-guiding component used is a hook-shaped hollow pipe 6 (a conventional metal pipe is used in this embodiment), with its lower end embedded in the water-retaining layer 3, its upper end flush with the surface of the surface reinforcement layer 5, and its bottom hook forming an upward 30° angle with the horizontal plane.

[0031] The first sand layer 2 contains sand and graphite powder in a mass ratio of 1:0.03. The second sand layer 4 contains sand and bentonite in a mass ratio of 1:0.05. The water-retaining layer 3 contains a mixture of fermented and decomposed straw and a water-retaining agent in a mass ratio of 1:0.1, wherein:

[0032] The water-retaining agent is synthesized by mixing pulverized quinoa hulls with water at 60°C to form a homogeneous mixture. The temperature of this mixture is adjusted to 50°C, and potassium persulfate solution is added as an initiator, reacting for 0.5 hours. Then, acrylic acid (neutralized to a 30% neutralization degree with 1 mol / L KOH solution), fly ash, and N,N-methylenebisacrylamide (a crosslinking agent) are added, and the mixture is reacted for 0.5 hours under a nitrogen atmosphere. The reaction product is cooled to room temperature, immersed in anhydrous ethanol for 10 hours, filtered, washed with water, and the filter cake is dried to constant weight and then pulverized. The solid-liquid ratio of quinoa hulls to water is 1:10. The amount of potassium persulfate solution added should be such that the mass of potassium persulfate is 0.01 times that of the grain hulls. The mass of acrylic acid added should be 10 times that of the grain hulls. The mass of fly ash added should be 0.5 times that of the grain hulls. The mass of N,N-methylenebisacrylamide added should be 0.02 times that of the grain hulls. The filter cake is crushed to 50 mesh to obtain a water-retaining agent.

[0033] The mixture of fly ash, sand, and concrete was granulated in a mass ratio of 4:5:1. The granulation reaction process was as follows: the mass ratio of water to the mixture of fly ash, sand, and concrete was adjusted to 0.45:1, and the mixture was granulated at 30℃ and 450 r·min. -1 Stir at a speed of 1 minute, then solidify for 24 hours to form hardened particles. Mix the hardened particles with sand at a mass ratio of 1:1 and spread them on the surface to form surface reinforcement layer 5.

[0034] The above-mentioned structure for improving water retention in desertified soil can maintain a water content of over 20% for more than 3 weeks under conditions of 30℃, 20% relative humidity, and 80% water absorption rate of the water retention layer.

[0035] Example 2:

[0036] A structural form for improving water retention in desertified soils, such as Figure 1 As shown, the structure includes a straw-woven frame 1; a first sand layer 2 with a thickness of 5 cm; a water-retaining layer 3 with a thickness of 30 cm; a second sand layer 4 with a thickness of 10 cm; and a surface reinforcement layer 5 with a thickness of 10 cm. The unidirectional water-guiding component used is a hook-shaped hollow pipe 6, with its lower end embedded in the water-retaining layer 3, its upper end flush with the surface of the surface reinforcement layer 5, and its bottom hook forming a 60° upward angle with the horizontal plane.

[0037] The first sand layer 2 consists of a uniform mixture of sand and graphite powder in a mass ratio of 1:0.01. The second sand layer 4 consists of a uniform mixture of sand and bentonite in a mass ratio of 1:0.02. The water-retaining layer 3 consists of a mixture of fermented and decomposed grain husks and a water-retaining agent in a mass ratio of 1:0.2, wherein:

[0038] The water-retaining agent is synthesized by mixing pulverized wheat husks with water at 70°C to form a homogeneous mixture. The temperature of this mixture is adjusted to 60°C, and potassium persulfate solution is added as an initiator, reacting for 2 hours. Then, acrylic acid (neutralized to a 65% neutralization degree with 1 mol / L KOH solution), fly ash, and N,N-methylenebisacrylamide (a crosslinking agent) are added, and the mixture is reacted for 3 hours under a nitrogen atmosphere. The reaction product is cooled to room temperature, immersed in anhydrous ethanol for 15 hours, filtered, washed with water, and the filter cake is dried to constant weight and then pulverized. The solid-liquid ratio of wheat husks to water is 1:40. The amount of potassium persulfate solution added should be 0.10 times the mass of the wheat husks. The mass of acrylic acid added should be 40 times the mass of the wheat husks. The mass of fly ash added should be 3 times the mass of the wheat husks. The mass of N,N-methylenebisacrylamide added should be 0.03 times the mass of the wheat husks. The filter cake is pulverized to 70 mesh to obtain the water-retaining agent.

[0039] The mixture of fly ash, sand, and concrete was granulated at a mass ratio of 3:6:1. The granulation reaction process was as follows: the mass ratio of water to the mixture of fly ash, sand, and concrete was adjusted to 0.4:1, and the mixture was granulated at 25℃ and 500 r·min. -1 Stir at a constant speed for 5 minutes, then solidify for 36 hours to form hardened granules. Mix the hardened granules with sand at a mass ratio of 0.5:1 and spread them evenly on the surface to form surface reinforcement layer 5.

[0040] The above-mentioned structure for improving water retention in desertified soil can maintain a water content of over 20% for more than 3 weeks under conditions of 35℃, 20% relative humidity, and 80% water absorption rate of the water retention layer.

[0041] Example 3:

[0042] A structural form for improving water retention in desertified soils, such as Figure 1 As shown, the structure includes a straw-woven frame 1; a first sand layer 2 with a thickness of 6 cm; a water-retaining layer 3 with a thickness of 25 cm; a second sand layer 4 with a thickness of 5 cm; and a surface reinforcement layer 5 with a thickness of 18 cm. The unidirectional water-guiding component used is a hook-shaped hollow tube 6. The lower end of the hook-shaped hollow tube 6 extends into the water-retaining layer 3, its upper end is flush with the surface of the surface reinforcement layer 5, and the bottom hook forms an upward 45° angle with the horizontal plane.

[0043] The first sand layer 2 contains sand and graphite powder in a mass ratio of 1:0.005. The second sand layer 4 contains sand and bentonite in a mass ratio of 1:0.01. The water-retaining layer 3 contains a mixture of fermented and decomposed poultry and livestock manure and a water-retaining agent in a mass ratio of 1:0.05, wherein:

[0044] The water-retaining agent is synthesized by mixing pulverized sorghum husks with water at 80°C to form a homogeneous mixture. The temperature of this mixture is adjusted to 75°C, and potassium persulfate solution is added as an initiator, reacting for 0.1 h. Then, acrylic acid (added as a 70% neutralized acrylic acid solution neutralized with 1 mol / L KOH solution), fly ash, and N,N-methylenebisacrylamide (a crosslinking agent) are added, and the mixture is reacted for 5 h under a nitrogen atmosphere. The reaction product is cooled to room temperature, immersed in anhydrous ethanol for 48 h, filtered, washed with water, and the filter cake is dried to constant weight and then pulverized. The solid-liquid ratio of sorghum husks to water is 1:60. The amount of potassium persulfate solution added should be 0.20 times the mass of the sorghum husks. The mass of the acrylic acid added should be 70 times the mass of the sorghum husks. The mass of the fly ash added should be 5 times the mass of the sorghum husks. The mass of the N,N-methylenebisacrylamide added should be 0.05 times the mass of the sorghum husks. The filter cake is crushed to 100 mesh to obtain a water-retaining agent.

[0045] The mixture of fly ash, sand, and concrete was granulated at a mass ratio of 5:4:1. The granulation reaction process was as follows: the mass ratio of water to the mixture of fly ash, sand, and concrete was adjusted to 0.5:1, and the mixture was granulated at 20℃ and 400 r·min. -1 Stir at a high speed for 10 minutes, then solidify for 48 hours to form hardened particles. Mix the hardened particles with sand at a mass ratio of 2:1 and spread them on the surface to form surface reinforcement layer 5.

[0046] The above-mentioned structure for improving water retention in desertified soil can maintain a water content of over 20% for one month under conditions of 30℃, 20% relative humidity, and 80% water absorption rate of the water retention layer.

[0047] Example 4:

[0048] A structural form for improving water retention in desertified soil, referring to Figure 1 The system includes a straw-woven frame 1; a first sand layer 2 with a thickness of 8 cm; a water-retaining layer 3 with a thickness of 20 cm; a second sand layer 4 with a thickness of 6 cm; and a surface reinforcement layer 5 with a thickness of 20 cm. The unidirectional water-guiding component used is a hook-shaped hollow tube 6, the lower end of which extends into the water-retaining layer 3, the upper end of which is flush with the surface of the surface reinforcement layer 5, and the bottom hook forms an upward 70° angle with the horizontal plane.

[0049] The first sand layer 2 contains sand and graphite powder in a mass ratio of 1:0.025. The second sand layer 4 contains sand and bentonite in a mass ratio of 1:0.03. The water-retaining layer 3 contains a mixture of fermented and decomposed grain husks and a water-retaining agent in a mass ratio of 1:0.1, wherein:

[0050] The water-retaining agent is synthesized by mixing pulverized soybean hulls with water at 50°C to form a homogeneous mixture. The temperature of this mixture is adjusted to 35°C, and potassium persulfate solution is added as an initiator, reacting for 1 hour. Then, acrylic acid (added as a 50% neutralized acrylic acid solution neutralized with 1 mol / L KOH solution), fly ash, and N,N-methylenebisacrylamide as a crosslinking agent are added, and the mixture is reacted for 1 hour under a nitrogen atmosphere. The reaction product is cooled to room temperature, immersed in anhydrous ethanol for 5 hours, filtered, washed with water, and the filter cake is dried to constant weight and then pulverized. The solid-liquid ratio of soybean hulls to water is 1:30. The amount of potassium persulfate solution added should be such that the mass of potassium persulfate is 0.05 times the mass of the grain hulls. The mass of acrylic acid added should be 20 times the mass of the grain hulls. The mass of fly ash added should be 0.1 times the mass of the grain hulls. The mass of N,N-methylenebisacrylamide added should be 0.01 times the mass of the grain hulls. The filter cake is crushed to 30 mesh to obtain a water-retaining agent.

[0051] The mixture of fly ash, sand, and concrete was granulated at a mass ratio of 4:5:1. The granulation reaction process was as follows: the mass ratio of water to the mixture of fly ash, sand, and concrete was adjusted to 0.45:1, and the mixture was granulated at 20℃ and 450 r·min. -1 Stir at a high speed for 20 minutes, then solidify for 48 hours to form hardened granules. Mix the hardened granules with sand at a mass ratio of 0.5:1 and spread evenly on the surface to form surface reinforcement layer 5.

[0052] The above-mentioned structure for improving water retention in desertified soil can maintain a water content of over 20% for more than 3 weeks under conditions of 30℃, 20% relative humidity, and 80% water absorption rate of the water retention layer.

[0053] Example 5:

[0054] A structural form for improving water retention in desertified soil includes a frame 1 woven from a mixture of rice straw and wheat straw; a first sand layer 2 with a thickness of 10 cm; a water-retaining layer 3 with a thickness of 28 cm; a second sand layer 4 with a thickness of 8 cm; and a surface reinforcement layer 5 with a thickness of 13 cm. The unidirectional water-guiding component used is a hook-shaped hollow pipe 6, with its lower end embedded in the water-retaining layer 3, its upper end flush with the surface of the surface reinforcement layer 5, and its bottom hook forming a 45° upward angle with the horizontal plane.

[0055] The first sand layer 2 contains sand and graphite powder in a mass ratio of 1:0.02. The second sand layer 4 contains sand and bentonite in a mass ratio of 1:0.005. The water-retaining layer 3 contains a mixture of fermented and decomposed straw and a water-retaining agent in a mass ratio of 1:0.15, wherein:

[0056] The water-retaining agent is synthesized by mixing pulverized rice husks with water at 80°C to form a homogeneous mixture. The temperature of this mixture is adjusted to 60°C, and potassium persulfate solution is added as an initiator, reacting for 1.5 hours. Then, acrylic acid (neutralized to a 40% neutralization degree with 1 mol / L KOH solution), fly ash, and N,N-methylenebisacrylamide (a crosslinking agent) are added, and the mixture is reacted for 2 hours under a nitrogen atmosphere. The reaction product is cooled to room temperature, immersed in anhydrous ethanol for 36 hours, filtered, washed with water, and the filter cake is dried to constant weight and then pulverized. The solid-liquid ratio of rice husks to water is 1:20. The amount of potassium persulfate solution added should be such that the mass of potassium persulfate is 0.15 times the mass of the rice husks. The mass of acrylic acid added should be 50 times the mass of the rice husks. The same mass of fly ash as the rice husks is added. The mass of N,N-methylenebisacrylamide added should be 0.04 times the mass of the rice husks. The filter cake is pulverized to 40 mesh to obtain the water-retaining agent.

[0057] Granulation was carried out using fly ash, sand, and concrete in a mass ratio of 4.5:4.5:1. The granulation reaction process is as follows: the mass ratio of water to the mixture of fly ash, sand, and concrete was adjusted to 0.5:1, and the mixture was granulated at 30℃ and 400 r·min. -1 Stir at a high speed for 30 minutes, then solidify for 72 hours to form hardened particles. Mix the hardened particles with sand at a mass ratio of 1.5:1 and spread evenly on the surface to form surface reinforcement layer 5.

[0058] The above-mentioned structure for improving water retention in desertified soil can maintain a water content of over 15% for one month under conditions of 35℃, 20% relative humidity, and 80% water absorption rate of the water retention layer.

[0059] The performance of each embodiment was tested as follows:

[0060] Experiment 1: Water Retention Test of Frame and Water-Retaining Layer

[0061] The experiment used aeolian sand from the Qinghai Lake desert. First, 30 grams of dry sand was added to the bottom layer of a 50 ml centrifuge tube (with a 1 mm hole at the bottom). Then, 20 grams of the water-retaining layer prepared in Examples 1-5 were added to the centrifuge tube. Two identical dry sand samples were prepared: one sample used the frame from Example 1 instead of the water-retaining layer as control group 1; the other sample used 20 grams of dry sand instead of the water-retaining layer as control group 2.

[0062] Slowly spray deionized water onto the surface of each of the above sand samples until water droplets fall from the bottom of the centrifuge tube. Calculate the water-holding capacity W of each sand sample when there is a water-retaining layer, when there is a frame, and when the sample is entirely sand, according to formula (1). h .

[0063] W h (%)=(M2-M1) / M1×100% (1)

[0064] Where M1 is the weight of the sand sample when it is dry; M2 is the weight of the sand sample when it is saturated with water.

[0065] Example 1 Example 2 Example 3 Example 4 Example 5 Control 1 Control 2 Water retention 49％ 57％ 50％ 52％ 55％ 37％ 31％

[0066] The experimental results show that the water holding capacity of the sand sample in control group 2, which used dry sand to replace the water-retaining layer, was 31%; the water holding capacity of the sand sample in control group 1, which used the frame, was 37%; and the water holding capacity of the sand sample using the water-retaining layer prepared in Examples 1-5 was significantly improved, increasing to a minimum of 49%. It can be seen that both the frame and the water-retaining layer can enable desert soil to hold more water, which is beneficial to crop growth.

[0067] Experiment 2: Water Retention Test of Water-Retaining Layer and Hook-Type Hollow Pipe Combined with Water-Retaining Layer

[0068] The experiment used aeolian sand from the Qinghai Lake desert. First, 30 grams of dry sand was added to a centrifuge tube (with a 1 mm hole at the bottom). 20 grams of the water-retaining layer prepared in Examples 1-5 were added to the centrifuge tube, and a top layer of 10 grams of dry sand was placed over it. Two identical dry sand samples were prepared. One sample used the hook-shaped hollow tube from Example 3, with its lower end buried in the 20-gram water-retaining layer prepared in Example 1, its upper end flush with the surface of the top layer of dry sand, and its bottom hook forming a 45° upward angle with the horizontal plane; this served as control group 1. The second sample used 20 grams of dry sand instead of the water-retaining layer; this served as test control group 2.

[0069] Slowly spray deionized water onto the surface of each sand sample until water droplets fall from the bottom of the centrifuge tube. Place each water-saturated sand sample at room temperature, measure its mass daily, and calculate the water retention capacity W of the sand sample within 30 days for the following conditions: with a water-retaining layer, with a combination of a hook-shaped hollow tube and a water-retaining layer, and completely sandy soil, according to formula (2).r .

[0070] W r (%) = (M) t -M1) / (M t -M2)×100% (2)

[0071] Where M1 is the weight of the sand sample when dry; M2 is the weight of the sand sample when saturated with water; M t It is the daily weight of the sand sample after it has become water-saturated.

[0072]

[0073] The experimental results show that after 15 days at room temperature, the water retention rate of the sand sample in control group 2 was 41%; the water retention rate of the sand sample using the water-retaining layer prepared in Examples 1-5 was 60%-71%; and the water retention rate of the sand sample in control group 1, which used a combination of a hook-shaped hollow tube and a water-retaining layer, was 67%. After 30 days at room temperature, the water retention rate of the sand sample in control group 2 decreased to 2%; while the water retention rate of the sand sample using the water-retaining layer was 22%-30%, an increase of more than 10 times; and the water retention rate of the sand sample in control group 1, which used a combination of a hook-shaped hollow tube and a water-retaining layer, was 25%. It is evident that the combination of a water-retaining layer and a hook-shaped hollow tube is beneficial for allowing water to freely enter the lower sand layer while effectively reducing upward evaporation and loss of water. The lower part of the hook-shaped hollow tube is hook-shaped with a bend angle of 30° to 70°, allowing snow and rainwater / irrigation water to directly enter the water-retaining layer from the ground, thereby increasing the water content of the water-retaining layer. When the outside air is dry, its hook-shaped structure can effectively reduce the upward movement and loss of moisture in the water-retaining layer, thereby inhibiting evaporation and unidirectional moisture conduction, and there is no white pollution.

[0074] Experiment 3: Wind Erosion Resistance Test of Surface Reinforced Layer and Hook-Shaped Hollow Tube

[0075] The experiment used aeolian sand from the Qinghai Lake desert. First, dry sand was poured into a stainless steel tray with a bottom length of 30cm and a bottom width of 20cm, forming a 10cm thick layer. The sand was compacted and the surface was smoothed. Several identical dry sand samples were prepared. The surface reinforcement layer used in Examples 1-5 was laid on the top layer of the tray with a thickness of 5cm. In control group 1, a 5cm thick water-retaining layer, as used in Example 1, was laid under the 10cm thick sand layer. Then, a hook-shaped hollow pipe was buried, with its upper end penetrating the sand layer and flush with its surface, and its lower end buried in the water-retaining layer. The lower hook section formed an upward 45° angle with the horizontal plane. In control group 2, a 5cm thick layer of dry sand was laid on the top layer of the tray instead of the surface reinforcement layer.

[0076] Each of the above sand samples was placed in the wind tunnel laboratory in sequence. The wind speed at the center of the wind tunnel was set to 15 m / s and the erosion time was 10 min. Then the mass of the sample after the wind erosion test was weighed and the loss per unit area of ​​the sample was calculated.

[0077] Example 1 Example 2 Example 3 Example 4 Example 5 Control 1 Control 2 Wind erosion 13 g / m 2 ]] 22 g / m 2 ]] 8 g / m 2 ]] 17 g / m 2 ]] 10 g / m 2 ]] 265 g / m 2 ]] 5072 g / m 2 ]]

[0078] The test results show that the wind erosion of the sand samples with the surface reinforcement layer used in Examples 1 to 5 is 8 to 22 g / m. 2 The wind erosion rate of the control group sand sample 1, which had a hollow pipe with a hook-shaped core, was 265 g / m³. 2 All were far lower than the wind erosion amount in the control group 2, which consisted entirely of sandy soil (5072 g / m²). 2 This indicates that laying a surface reinforcement layer and burying hook-shaped hollow pipes can effectively reduce wind erosion in sandy soil and improve the situation where plant roots are exposed due to wind erosion.

[0079] Experiment 4: Fertilizer Retention Test of Frame and Water-Retaining Layer

[0080] The experiment used aeolian sand from the Qinghai Lake desert. First, 30 grams of dry sand was added to the bottom layer of a centrifuge tube (with a 1 mm hole at the bottom). Then, 10 grams of the water-retaining layer prepared in each example was added to the centrifuge tube. Next, 10 grams of dry sand and 0.1 grams of urea were mixed evenly and added to the top layer of the centrifuge tube. Two identical dry sand samples were prepared: one sample used the frame from Example 1 instead of the water-retaining layer as control group 1; the other sample used 10 grams of dry sand instead of the water-retaining layer as control group 2.

[0081] 50 mL of deionized water was slowly added to each sand sample, the leachate was collected, and the absolute nitrogen content in the leachate was determined by standard method. The leaching loss rate W of urea in each sand sample was calculated using formula (3). f .

[0082] W f (%) = N2 / N1 × 100% (3)

[0083] Where N1 is the nitrogen content in the sand before leaching, and N2 is the nitrogen content in the leachate.

[0084]

[0085] The experimental results showed that, compared with control group 2, the nitrogen leaching loss rate of urea decreased from 49% to 21%–36% when using the water-retaining layer prepared in Examples 1–5; the nitrogen leaching loss rate of urea decreased to 40% when using the frame in control group 1. This indicates that both the frame and the water-retaining layer can reduce the loss of fertilizer nutrients during the leaching process. In conclusion, the application of the frame and the water-retaining layer to the soil can effectively reduce the nutrient loss rate in fertilized soils, and has great application potential in agriculture.

[0086] Bentonite and graphite dust are abundant, inexpensive, readily available, stable, and non-toxic. Adding small amounts of each to different sandy soil layers improves the adsorption and adhesion properties of sand particles in the upper layer and the water vapor condensation rate in the lower layer, respectively. Combined with the aforementioned three-dimensional structure, this allows for greater retention of water vapor within the structure, enhancing plant water utilization without affecting gas transport in the soil, and also suppressing wind erosion and dust. The framing and the use of hook-shaped hollow pipes made from materials such as straw, utilizing waste straw, not only effectively utilizes solid waste and enhances the water-holding and conductivity of sandy soil but also increases the organic matter content and fertility of the soil. Compared to one-way permeable layers made from chemical materials, this method is more economical and environmentally friendly. Experiments one through four fully demonstrate the feasibility and effectiveness of this invention.

Claims

1. A soil water retention improvement structure for desertified areas, characterized in that, The device includes a frame, and within the frame, arranged sequentially from bottom to top, a first sand layer, a water-retaining layer, a second sand layer, a surface-reinforcing layer, and a unidirectional water-guided component. The first sand layer contains sand and graphite powder in a mass ratio of 1:(0.005~0.03). The water-retaining layer contains organic compost and a water-retaining agent in a mass ratio of 1:(0.05~0.2). The second sand layer contains sand and bentonite in a mass ratio of 1:(0.005~0.05). The surface-reinforcing layer contains hardened particles obtained by granulating fly ash, sand, and concrete in a mass ratio of (3~5):(4~6):

1. The unidirectional water-guided component includes multiple hook-shaped hollow tubes, the lower end of which is buried in the water-retaining layer, and the upper end extends out of the soil, flush with the surface of the surface-reinforcing layer. The bottom hooks form an upward angle of 30°~70° with the horizontal plane.

2. The desertification soil water retention improvement structure according to claim 1, characterized in that, The organic composted materials include fermented and composted straw, grain husks, or poultry and livestock manure.

3. The desertification soil water retention improvement structure according to claim 1, characterized in that, The water-retaining agent is prepared by mixing grain hulls, acrylic acid, and fly ash in a mass ratio of 1:(10~70):(0.1~5) under a nitrogen atmosphere at 35~75℃, using potassium persulfate as an initiator and N,N-methylenebisacrylamide as a crosslinking agent.

4. A soil water retention improvement structure for desertified areas according to claim 2 or 3, characterized in that, The grain husks mentioned include quinoa husks, wheat husks, rice husks, sorghum husks, or bean husks.

5. The desertification soil water retention improvement structure according to claim 1, characterized in that, The hardened particles in the surface strengthening layer are obtained by mixing fly ash, sand, and concrete to obtain a mixture, adding water, and adjusting the mass ratio of water to the mixture to (0.4~0.5):

1. The mixture is then heated at 20~30℃ and at 400~500 r·min. -1 Stir at a speed of 1~30 min, then cure for 24~72 h to form hardened particles.

6. The desertification soil water retention improvement structure according to claim 5, characterized in that, The surface strengthening layer is made by mixing hardened particles obtained by granulating fly ash, sand and concrete with sand at a mass ratio of (0.5~2):

1.

7. The desertification soil water retention improvement structure according to claim 1, characterized in that, The frame is woven from straw, which includes any one or a combination of rice straw or wheat straw.

8. The desertification soil water retention improvement structure according to claim 1, characterized in that, The first sand layer inside the frame is 5-10cm thick, the water-retaining layer is 20-30cm thick, the second sand layer is 5-10cm thick, and the surface reinforcement layer is 10-20cm thick.

9. A method for improving desertified soil using the structure described in any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Use straw to weave the frame; (2) Set up the enclosure around the perimeter and bottom of the sand; (3) The frame is composed of a first sand layer, a water-retaining layer, a second sand layer, and a surface reinforcement layer from bottom to top. (4) Set up a one-way water guide component, including burying the lower ends of multiple hook-shaped hollow pipes into the water-retaining layer, the upper ends extending out of the soil and flush with the surface of the surface reinforcement layer, and the bottom hooks forming an upward angle of 30°~70° with the horizontal plane.

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