A method for controlling desertified areas

Abstract

The invention provides a method for treating a desertified area, comprising dividing a desertified area to be treated into zones to form a plurality of vegetation blocks and a plurality of urease-coated sandy soil blocks, wherein the vegetation blocks and the urease-coated sandy soil blocks are staggered and connected; planting super-xerophytes in the vegetation blocks, spraying a urease coating agent on the surface of the urease-coated sandy soil blocks, wherein the urease coating agent forms a sand-fixing coating layer of a certain thickness on the surface of the sandy soil to reinforce the surface sandy soil; the urease coating agent comprises two components, wherein the first component is a modified soybean urease solution and the second component is a solidifying liquid; the modified soybean urease solution comprises soybean urease, starch-grafted acrylic acid copolymer particles with a particle size distribution of 0 to 3 mm, and chitosan; the solidifying liquid comprises urea and calcium salt; the first component and the second component are separately contained after being prepared, and before spraying the urease coating agent, the first component and the second component are evenly mixed and sprayed in time. The present invention combines the urease film surface sand fixation technology with the plant root deep reinforcement technology to achieve three-dimensional reinforcement and sand fixation in a low-carbon and environmentally friendly manner, providing a good green management model for desert management.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental governance, and in particular to a method for governing desertified areas. Background Art

[0002] The desertification and erosion caused by the land sandstorm have led to the reduction of biological species and the destruction of the environment, directly or indirectly causing major economic losses and serious ecological problems to the country and society. Therefore, all countries have invested a lot of manpower and material resources in the field of wind and sand control, with the aim of innovating the desert control mechanism, and have achieved some results. Through the control of the desert, not only can the ecological environment and agricultural and animal husbandry production conditions be improved, but more importantly, it is also of great significance to promote economic structural adjustment and social progress.

[0003] Desert aeolian soil is a special soil developed on aeolian sand parent material, with fine particles, good roundness, no cohesion between particles, loose, easy to flow and easy to wind erosion. At present, many scholars at home and abroad have conducted a lot of in-depth research on desertification control and management, and proposed some effective solutions. For example, Chinese patent application publication number CN106717226A discloses a method for desert greening using straw grass blankets, which uses straw grass blankets to manage the desert. The straw grass blankets contain grass seeds, tree seeds, flower seeds, vegetable seeds, etc., and the straw blankets are used for mixed sowing. After these seeds take root and germinate, they can improve the greening and ecology of the desert. The management mode of this scheme is vegetation protection, which mainly depends on the selection of plant species. The disadvantage is that when only relying on plant roots to reinforce and consolidate the soil and prevent wind and sand, the climatic conditions of the desert make it difficult for green vegetation to survive. Even if it survives, it can only turn the mobile sand dunes into semi-fixed sand dunes, and the source of sand and dust cannot be fundamentally cut off. In addition, chemical reinforcement is also a common treatment measure in desert engineering. For example, Chinese patent publication number CN101548595B discloses spraying a hydrophilic polyurethane resin curing agent solution on the sand or soil layer where greening materials are spread to form a porous solidified sand layer. However, this scheme uses chemically refractory grouting materials to reinforce sand and soil, which will cause serious water and soil pollution and have adverse effects on the environment. In recent years, MICP (microbial induced calcium carbonate deposition) technology has become a new type of soil reinforcement technology due to its advantages of low carbon, high efficiency and environmental protection. For example, Chinese patent application publication number CN108929703A discloses a green ecological treatment method of desert in-situ microurease film coating technology, which uses desert self-source microorganisms selected from the soil of the desert area to be treated to fix the surface of the desert area to be treated, forming a microbial film with stable performance, high strength and strong water retention, fundamentally blocking the source of sand and dust, and reducing the impact of foreign microorganisms on the desert area to be treated. However, due to the influence of the size and aerobicity of urease-producing bacteria, the type and depth of MICP treatment of soil are subject to certain limitations. In addition, the scheme also has problems such as complex microbial culture steps, harsh culture conditions, difficulty in mass production, and high cost, making it difficult to apply in actual engineering. Summary of the invention

[0004] 1. Technical problems to be solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for controlling desertified areas, which combines urease film coating surface sand fixation technology and plant root deep reinforcement technology to achieve three-dimensional reinforcement and sand fixation in a low-carbon and environmentally friendly manner, providing a good green management model for desert management.

[0006] (2) Technical solution

[0007] The invention provides a method for treating desertified areas, which includes:

[0008] S1. The desertified area to be treated is divided into zones to form a plurality of vegetation blocks and a plurality of urease-coated sandy soil blocks, and the vegetation blocks and the urease-coated sandy soil blocks are staggered and connected.

[0009] S2. Plant super-xerophytes in the vegetation blocks and spray urease film-coating agent on the surface of urease-coated sand blocks. The urease film-coating agent forms a sand-fixing film layer on the surface of the sand to strengthen the surface sand.

[0010] The urease coating agent comprises two components, component one is a modified soybean urease solution, and component two is a solidifying liquid; the modified soybean urease solution comprises soybean urease solution, starch grafted acrylic acid copolymer particles with a particle size distribution of 0-3 mm, and chitosan; the solidifying liquid comprises urea and calcium salt, and the calcium salt is a water-soluble calcium salt.

[0011] After component one and component two are prepared, they are packaged separately. Before spraying the urease coating agent, component one and component two are mixed evenly and sprayed in time.

[0012] Preferably, the starch grafted acrylic copolymer particles with a particle size of less than 1 mm account for 65-75% of the total mass of the total starch grafted acrylic copolymer particles, and the rest are 1-3 mm starch grafted acrylic copolymer particles. The starch grafted acrylic copolymer particles can be degraded and do not pollute the soil environment.

[0013] Preferably, the distance between two adjacent vegetation blocks does not exceed 2m, preferably 0.5m~2m, more preferably 0.5m~1m; and the specifications of the vegetation blocks can be (3~10)m×(3~10)m, preferably (5~10)m×(5~10)m.

[0014] Since the temperature in desertified areas is high during the day and the surface of the sand is hot, in order to avoid the solution evaporating too quickly under high temperature and the modified soybean urease solution and the solidifying liquid penetrating too quickly in the sand, resulting in uneven distribution of the urease film agent in the soil and affecting the solidification effect, before spraying the urease film agent, a one-phase method is adopted - the modified soybean urease solution and the solidifying liquid are mixed and sprayed, so that the two liquids are mixed and sprayed on the surface of the sand, which promotes the urease film agent to solidify on the surface of the sand to form a sand-fixing film layer before a large amount of evaporation and infiltration occurs.

[0015] According to a preferred embodiment of the present invention, the plants planted in the vegetation blocks are super-xerophytes that are cold-resistant, drought-resistant, wind-erosion-resistant, sand-burying-resistant, fast-growing, have well-developed rhizomes, and are wind-proof and sand-fixing.

[0016] According to a preferred embodiment of the present invention, the preparation method of the modified soybean urease solution is as follows.

[0017] Step 1: After drying the soybeans, crush them with a crusher and sieve them to get soybean powder.

[0018] Step 2: Soak the soybean powder in water and let it stand for more than 2 hours. Remove the soybean powder residue after filtering and keep the filtrate. Let the filtrate stand and retain the supernatant to obtain the soybean urease solution.

[0019] Step 3: After adjusting the pH of the soybean urease solution to 5.5-6, starch grafted acrylic copolymer particles and chitosan with a particle size distribution of 0-3 mm are added, the final concentration of starch grafted acrylic copolymer particles is 0.5-1%, and the final concentration of chitosan is 0.5-2%, thereby obtaining a modified soybean urease solution.

[0020] The pH of the soybean urease solution was adjusted to 5.5-6 with acetic acid. On the one hand, this pH range can reduce the activity of urease, slow down the reaction rate between the modified soybean urease solution and the solidifying liquid, and improve the uniformity of the sand-fixing film layer. On the other hand, this pH helps to promote the dissolution of chitosan in the soybean urease solution, and chitosan and starch-grafted acrylic acid copolymer particles can combine and significantly improve the durability and water retention of the film. Dissolving 0.5%-2% (mass concentration) chitosan in the soybean urease solution can extend the shelf life of the soybean urease solution under high temperature conditions.

[0021] According to a preferred embodiment of the present invention, the urease concentration in the modified soybean urease solution is 20 g / L to 100 g / L, preferably 20 g / L to 40 g / L.

[0022] According to a preferred embodiment of the present invention, the calcium salt in the solidifying liquid is at least one of calcium chloride, calcium acetate and calcium lactate; and the calcium ion concentration in the solidifying liquid is 0.03 mol / L to 0.1 mol / L.

[0023] According to a preferred embodiment of the present invention, the molar concentration ratio of urea to calcium ions in the solidifying liquid is 1:1, that is, the urea concentration is 0.03 mol / L~0.1 mol / L.

[0024] Too high calcium ion concentration will cause serious soil alkalinization and affect vegetation growth. Therefore, controlling the calcium ion concentration in the solidifying liquid at 0.03mol / L~0.1mol / L can reduce the inhibitory effect of high concentration of calcium ions on plant growth.

[0025] According to a preferred embodiment of the present invention, the solidifying liquid is prepared by mixing a calcium salt solution and a urea solution according to a molar concentration of calcium salt to urea of ​​1:1, and the concentrations of urea and calcium ions are 0.03 mol / L~0.1 mol / L, respectively. The pH value of the solidifying liquid is adjusted to 5.5~6, and the solidifying liquid is placed for more than 3 hours after preparation is completed before use, but should be used up within 6 hours.

[0026] According to a preferred embodiment of the present invention, before spraying the urease film-forming agent, the spraying amount of component one and component two is 1L / m²~5L / m² respectively, the mixing volume ratio of component one to component two is 1:1~1:3, and the thickness of the sand-fixing film layer is 0.5cm~2.5cm. Preferably, the urease film-forming agent is sprayed in the evening to avoid too fast evaporation of the solution under high temperature environment and to maximize the uniformity of the sand-fixing film layer. The specific spraying amount is adjusted according to the thickness of the sand-fixing film layer for solidifying sand, and the thickness can be adjusted according to the environment and the goal of governance to adjust the spraying amount of the sand film area.

[0027] According to a preferred embodiment of the present invention, the super xerophyte is one or more of Ammopiptanthus mongolicus, Tamarisk, Aloe, Cactus, Populus euphratica, Nitraria, Hippophae rhamnoides and the like.

[0028] According to a preferred embodiment of the present invention, when planting super-xerophytes in a vegetation block, the root density is adjusted according to the spacing of the planted plants, and the sandy soil of the vegetation block needs to be treated with base fertilizer and mixed with organic fertilizer before the plant is planted to ensure sufficient nutrients for plant growth. The fertilization depth is determined by the characteristics of the super-xerophytes planted, and can generally be 15cm to 40cm in depth. The fertilizers used include new biofertilizers, organic fertilizers, poultry or livestock manure suitable for super-xerophytes, and nitrogen, phosphorus, and potassium fertilizers are applied at the same time.

[0029] According to a preferred embodiment of the present invention, it also includes secondary zoning of the planting blocks; dividing the planting blocks into plant areas and rows and plants, spraying urease film-forming agent on the surface of the sand between the rows and plants to form a sand-fixing film layer; the amount of urease film-forming agent sprayed between the rows and plants is 1 / 2~1 / 4 of the urease film-forming agent in the urease film-forming sandy soil area, or less than 2L / m² of urease film-forming agent is sprayed within a radius of 5 cm centered on the plant diameter, 3L / m²~4L / m² of urease film-forming agent is sprayed outside the radius of 5 cm, and 4L / m²~5 L / m² of urease film-forming agent is sprayed in the urease film-forming sandy soil area.

[0030] The experiment showed that the dosage of 1% chitosan did not affect the permeability of the urease coating agent. At the spraying volume of 2L, 3L and 4L, the thickness of the sand-fixing coating layer was 0.5cm, 0.7cm and 1cm respectively.

[0031] By spraying urease film coating agent with gradient spraying amount, the curing thickness and permeability of the film layer around the plant roots are changed, rainwater is guided to flow to the plant roots, and the water absorption of the plant roots is increased.

[0032] Starch grafted acrylic copolymer particles with a particle size of 1mm~3mm can form a protective layer on the surface, and have excellent water storage and release properties, which can effectively slow down wind erosion, allow rainwater to penetrate downward, and promote the retention of groundwater. Starch grafted acrylic copolymer particles with a particle size of less than 1mm are more evenly distributed in the urease film coating agent, have permeability in sandy soil, and can achieve better improvements in soil structure. As small-sized starch grafted acrylic copolymer particles sink in the sandy soil as rainwater washes the cracks of rock sand, fine water connections are formed, which increases the use of water by plant roots and promotes plant survival.

[0033] (III) Beneficial effects.

[0034] The desertification control method of the present invention can, on the one hand, utilize the urease coating agent to form a horizontal shallow reinforcement and anchoring effect on the desert sandy soil; on the other hand, it can utilize the root system of the super-xerophyte to form a longitudinal deep reinforcement and anchoring effect. In addition, after the plants flourish, their root systems form an intricate extension in all directions to form a deep reinforcement and anchoring effect, thereby forming a three-dimensional reinforcement and sand fixation effect, which can well play the role of maintaining soil moisture and preventing wind and fixing sand, so that the mobile sand dunes are gradually transformed into fixed and semi-fixed sand dunes, which plays a good edge locking protection role on the marginal areas of the desert, and reduces the wind erosion damage of the desert to people's living environment. The control method is conducive to the ecological control and restoration and reconstruction of the desert.

[0035] Compared with urease secreted by microorganisms, the soybean urease used in the present invention is nano-sized, has good water solubility, is in a free state, and is degradable, so it is more suitable for reinforcing fine-grained soil and can further reduce the adverse effects on the microecological environment. The present invention uses a sand-fixing film layer to fix the surface sand, so that the mobile sand dunes become semi-fixed and fixed sand dunes through the fixed film, fundamentally blocking the source of sandstorms.

[0036] Soybean urease forms a sand-fixing film layer under the action of solidifying liquid. The sand-fixing film layer can cement the loose sand into a new green artificial material with certain strength and good permeability, showing the characteristics of affinity with rock and soil matrix, good air permeability and water retention, etc. It will not affect the growth of green plants, and can be jointly optimized with drought-resistant and barren-resistant plants, so as to realize the mutual dependence and mutual support between the in-situ film covering of urease film agent and the green plants in the sand, and jointly build a new pattern of desert ecosystem.

[0037] The solidifying liquid in the urease coating agent is mainly composed of urea and calcium salt. The urea in the solidifying liquid will be hydrolyzed into CO3 by urease. 2- and NH4 + ,CO3 2- Then with Ca in the calcium source 2+Chitosan added to the modified soybean urease solution can wrap the generated calcium carbonate crystals in combination with the generated calcium carbonate, thereby increasing the durability and water retention of the sand-fixing film layer. Chitosan itself also has thickening and film-forming properties, so it can reduce the penetration rate of the urease film-forming agent, allowing the sand-fixing film layer to remain in the shallow surface of the sand, wrapping the generated calcium carbonate crystals, thereby increasing the durability and water retention of the film layer.

[0038] Adding 0.5% to 1% of small-size (0 to 3 mm) starch-grafted acrylic copolymer particles to the soybean urease solution helps to form fine water channels, increase the use of water by plant roots, and promote plant survival. Dissolving 0.5% to 2% chitosan in the soybean urease solution can extend the shelf life of the soybean urease solution under high temperature conditions, and can also be used as a water retainer and thickener to slow down the evaporation and penetration rate of the urease coating agent. Chitosan can also promote the formation of calcium carbonate, thereby reducing the concentration of calcium salts and the amount of solidifying liquid, which not only reduces the material cost of the urease coating agent but also protects plant growth and the environment. Chitosan is degradable, and after degradation, it can fertilize the soil, improve the local microbial environment, and provide nutrients for desert self-sourced microorganisms. As the water evaporates, chitosan gradually shrinks and solidifies, protecting the calcium carbonate crystals in the soil. Dried chitosan also restricts the relative movement between sand particles, and reinforces the sand particles in the form of fibers, making the sand particles larger and heavier and difficult to form sand and dust. The amount of chitosan used can be determined according to the concentration of urease solution and the thickness of the solidified soil.

[0039] The concentration of calcium ions in the solidifying liquid is 0.03mol / L~0.1mol / L, which is mainly used to reduce the inhibitory effect of excessively high concentrations of calcium sources on plant growth. The solidifying liquid is placed for more than 3 hours and less than 6 hours after preparation, so that the distribution of urea and calcium salts in it can be more uniform. The urease filming agent is a mixture of modified soybean urease solution and solidifying liquid, which is sprayed on the surface of the sand in time, so that the mixture of the two components reacts synchronously and generates calcium carbonate during the infiltration process into the sand, so as to improve the uniformity of the sand-fixing film layer.

[0040] The planting area also includes secondary zoning; the planting blocks are divided into plant areas and rows and plants, and urease film-forming agent is sprayed on the sand surface between rows and plants to form a sand-fixing film layer; the amount of urease film-forming agent sprayed between rows and plants is 1 / 2~1 / 4 of the urease film-forming agent in the urease film-forming sand area, or less than 2L / m² of urease film-forming agent is sprayed within a radius of 5cm centered on the plant diameter, 3L / m²~4L / m² of urease film-forming agent is sprayed outside the radius of 5cm, and 4~5 L / m² of urease film-forming agent is sprayed in the urease film-forming sand area. By setting urease filming agents with different spraying thicknesses between rows and plants in urease-coated sandy soil areas and planting blocks, different water penetration resistances are generated, forming a resistance difference and a funnel effect, thereby guiding the surface water runoff in the urease-coated sandy soil area to flow toward the planting blocks, while the water flow in the planting blocks is more likely to flow and infiltrate toward the plant area, making it easier for the water flow to gather at the roots of the plants for use by the plants, thereby increasing the water utilization rate and survival rate of plants in desertified areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of dividing and controlling a desertified area in Example 1.

[0042] Figure 2 This is a schematic diagram of the secondary zoning and management of desertified areas in Example 2.

[0043] Figure 3 This is a schematic diagram of the effect of controlling desertified areas according to Example 2. DETAILED DESCRIPTION

[0044] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0045] Example 1

[0046] like Figure 1 In the embodiment 1 shown, a desertified area is 51m long and 41m wide, and the desertified area is divided into 4m×5m and 9m×9m planting blocks 3 and urease-coated sandy soil blocks 4 located between the planting blocks 3. The width of these urease-coated sandy soil blocks is 1m, and they run through the entire desertified area horizontally and vertically, so that the vegetation blocks 3 and the urease-coated sandy soil blocks 4 are staggered and continuous.

[0047] Super xerophytes 31 with well-developed root systems are sown in vegetation block 3, and urease film-forming agents are sprayed on the surfaces of 4 urease-coated sandy soil areas. The urease film-forming agents form a sand-fixing film layer on the surface of the sandy soil to reinforce the surface sandy soil in the urease-coated sandy soil area.

[0048] When sowing the super-xerophytes 31 with well-developed plant root systems in the vegetation block 3, a vegetation layer of a certain density is first formed. A small amount of organic base fertilizer is applied to all the super-xerophytes according to the variety and quantity of the super-xerophytes to ensure sufficient nutrients for plant growth. The depth of base fertilizer application is determined by the characteristics of the super-xerophytes planted, and can generally be 15cm to 40cm deep. The base fertilizer includes organic fertilizer poultry or livestock manure suitable for super-xerophytes, and nitrogen, phosphorus and potassium fertilizers are applied at the same time.

[0049] The preparation method of the urease coating agent is as follows.

[0050] (1) Dry the soybeans for 5 days, grind them into powder, sieve them to a size of less than 0.25 mm, and obtain fine soybean powder. Soak the soybean powder in tap water for 2 hours, filter and separate the solid and the filtrate, let the filtrate stand and retain the supernatant to obtain the soybean urease solution. At this time, the concentration of the soybean urease solution is 45 g / L.

[0051] (2) After adjusting the pH value of the soybean urease solution to 5.5-6 with acetic acid, chitosan and starch-grafted acrylic acid copolymer particles with a particle size distribution of 0-3 mm (particle size below 1 mm accounts for 65%, and particle size 1-3 mm accounts for 35%) are added to make the mass concentration of chitosan 1% and the concentration of starch-grafted acrylic acid copolymer particles 0.6% to prepare a modified soybean urease solution.

[0052] (3) Urea and calcium chloride are prepared in an equal molar ratio to obtain a urea solution and a calcium chloride solution. The concentrations of the urea solution and the calcium chloride solution are 0.05 mol / L, respectively. The urea solution and the calcium chloride solution are mixed in a volume ratio of 1:1 to obtain a solidifying solution. After the solidifying solution is prepared, acetic acid is used to adjust the pH to 5.5-6.

[0053] (4) After the solidified liquid is placed for 3 hours, the solidified liquid is mixed with the modified soybean urease solution of step (3) in a volume ratio of 1:2, and immediately sprayed onto the surface of the urease coated sand area 4. The spraying amount of the solidified liquid is 1.5 L / ㎡, and the spraying amount of the modified soybean urease solution is 3 L / ㎡. The spraying time is preferably in the evening to reduce the volatilization rate.

[0054] The roots of the plants sown in vegetation block 3 form a longitudinal anchoring and sand-fixing effect on the sand at a certain depth below the surface of the sand, while in the urease-coated sand area 4, the calcium carbonate formed by the soybean urease coating agent forms a solidified coating layer on the surface of the sand. The solidified coating layer can cement the loose sand into a new green artificial material with a certain strength and good permeability, showing the characteristics of affinity with the rock and soil matrix, good air permeability and water retention, etc. It will not affect the growth of green plants and can be combined with drought-resistant and barren-resistant plants to fix sand. The plant roots of vegetation block 3 form reinforced anchoring points on the sand in the longitudinal depth; as the plants sown in vegetation block 3 survive and flourish, their roots continue to extend downward and horizontally, intertwined, and the roots of two adjacent vegetation blocks 3 are connected together under the sand layer, forming cross-linked anchoring points in all directions of depth. The longitudinal depth and depth level of the reinforced sand-fixing anchor points formed by the vegetation block 3 and the sand-fixing film layer of the urease-coated sandy soil area 4 combine to form a three-dimensional reinforced sand-fixing effect. Furthermore, as the plants sown in the vegetation block 3 spread horizontally, some plant buds emerge from the urease-coated sandy soil area 4 or take root under the sand of the urease-coated sandy soil area 4, so that the mobile sand in the urease-coated sandy soil area 4 is gradually covered and anchored by vegetation.

[0055] In this embodiment, the urease-coated sand layer can fundamentally block the source of sand and dust, has strong vegetation affinity, does not affect plant growth, reduces blowing sand, prevents plants from being buried by sand, and improves the ability to retain rainwater and dew. The tiny starch-grafted acrylic copolymer particles penetrate into the sand to form a water connection path, increasing the survival rate of the vegetation seedlings in the vegetation block 3. So far, the in-situ filming of the urease film-coating agent and the green plants in the sand are interdependent and mutually dependent, realizing the ecological governance of the desert and jointly building a new pattern of the desert ecosystem. Plant soybean urease does not pollute the desert environment, and there will be no invasion of alien species. All components of the sand-fixing film layer can be degraded, which is conducive to the governance of the desert ecology.

[0056] Example 2

[0057] This embodiment further divides the vegetation block 3 into plant zone 1 and inter-row and inter-plant zone 2 based on the embodiment 1, and the area within a radius of 5 cm around the plant ground diameter is defined as plant zone 1. Since multiple plants are planted in vegetation block 3 according to certain row spacing and inter-plant spacing, and the root system of the plants is not well developed during the seedling period, and the anchoring effect on the sand is poor, in this embodiment, urease film-forming agent is sprayed in inter-row and inter-plant zone 2, but urease film-forming agent is not sprayed in plant zone 1, forming a leakage zone around the plant ground diameter. Figure 2As shown, the vegetation block 3 with a length of 8m and a width of 5m is divided into 3×5 plant areas 1 with a size of 1m×1m. Super-xerophytes such as Ammopiptanthus mongolicus or Nitraria tangutorum are planted in the plant area 1. At the same time, areas with a row spacing of 0.5m and a plant spacing of 0.5m are obtained. Urease film-forming agent is also sprayed on this area to form a sand-fixing film layer on the shallow surface of the sand.

[0058] In this embodiment, the urease coating agent can be prepared in the manner of Example 1. In this embodiment, in order to allow surface water runoff to quickly penetrate into the roots of the plants, the concentration of the urease coating agent sprayed between rows and plants can be reduced or the spraying amount can be reduced to promote the rapid penetration of surface water into the roots of the plants. For example, in this embodiment, the urease concentration in the modified soybean urease solution is 20g / L, the chitosan concentration is 2%, and the starch grafted acrylic copolymer particle concentration is 1% (70% of the particles are below 1mm in diameter, and 30% of the particles are 1mm~3mm in diameter). The urea concentration in the solidifying liquid is 0.1mol / L, and the calcium ion concentration is 0.04mol / L. Before spraying, the modified soybean urease solution and the solidifying liquid are mixed in a volume ratio of 1:1 and sprayed in time, and the spraying thickness between rows and plants 2 can be 1 / 2 of the spraying thickness of the urease film-coated sandy soil area 4.

[0059] Since surface water tends to infiltrate from places with less resistance when it flows,

[0060] By setting different spraying thicknesses of urease filming agents between rows and plants in the urease filming sand area and the planting area, different water penetration resistances are generated, forming a resistance difference, guiding the rainwater runoff in the urease filming sand area to flow to the vegetation block 3, while the rainwater runoff in the vegetation block 3 is easy to flow and infiltrate to the plant area 1, making it easier for the water flow to gather at the roots of the plants for the plants to use; and the large amount of chitosan and small-particle starch-grafted acrylic copolymer particles around the ground diameter of the plants increase the water utilization rate and survival rate of the plants by using their water retention, which greatly promotes the horizontal connection of the roots under the sand after the plants survive, and spreads between plants to increase the anchoring effect on the sand. Figure 3 As shown, the solidified film layer formed by vegetation and urease creates a three-dimensional anchoring effect on the sand.

[0061] Example 3

[0062] The present embodiment is similar to the embodiment 2 in that the vegetation block 3 is further divided into the plant area 1 and the row and plant spacing 2. Since the vegetation block 3 is planted with multiple plants according to certain row spacing and plant spacing. For example, the vegetation block 3 with a length of 8m and a width of 5m is divided into 3×5 plant areas 1 with a specification of 1m×1m, and super-xerophytic plants such as Ammopiptanthus or Nitraria are planted in the plant area 1. At the same time, an area with a row spacing of 0.5m and a plant spacing of 0.5m is obtained. This part of the area is also sprayed with urease film-forming agent to form a sand-fixing film layer on the shallow surface of the sand. The main difference from Example 2 is: using the urease film-forming agent prepared in Example 1, when spraying the urease film-forming agent, this embodiment sprays less than 2L / m² of urease film-forming agent within a radius of 5cm centered on the plant's ground diameter, sprays 3L / m²~4L / m² of urease film-forming agent outside the radius of 5cm, and sprays 4L / m²~5L / m² of urease film-forming agent in the urease-coated sandy soil area 4.

[0063] In order to prevent the loss of sand around the ground diameter of the plant seedlings, this embodiment also sprays a small amount of urease coating agent to solidify the sand. However, by spraying different amounts of urease coating agent in a gradient, the rainwater runoff in the urease coated sand area 4 can flow to the inter-row and inter-plant 2, and the rainwater runoff in the inter-row and inter-plant 2 can flow to the ground diameter of the plant and seep downward. At the same time, with the help of the starch grafted acrylic copolymer particles in the urease coating agent, it surrounds the ground diameter of the plant and plays a local water retention role. The starch grafted acrylic copolymer particles with a particle size of less than 1 mm can be washed by rainwater and the movement of sand particles, and continuously sink along the gaps between sand particles to the vicinity of the plant root system, thereby improving the water retention capacity of the sand near the root system and improving the survival rate of the plant seedlings.

[0064] Comparative Example 1

[0065] This example compares the results of replacing chitosan in Example 1 with an equal amount of starch, sugar or other organic matter that provides nucleation sites for calcium carbonate deposition. The resulting urease coating agents were sprayed in laboratory sand pile samples at a spray rate of 4 L / m². The preparation method is the same as that in Example 1, except that the chitosan was replaced or the starch-grafted acrylic acid copolymer particles were removed.

[0066] After spraying, leave it overnight, spray 3L / m² of clean water every 3 days to simulate rain, turn on the fan to simulate wind, and the wind should be just enough to blow the sand before spraying the urease film agent. Continue for 2 hours every day. After 18 days, observe and compare the sand fixation performance of each group of urease film agents. The comparison is as follows.

[0067]

[0068] Urea is a commonly used nitrogen fertilizer, but it cannot be directly absorbed by plants. It must first be converted into ammonia nitrogen before it can be absorbed and utilized by plant roots. The presence and activity of urease are crucial to the effectiveness of urea fertilizer in the soil. It accelerates the decomposition of urea, allowing ammonia to be quickly converted into a form that can be used by plants, thereby improving the efficiency of soil nitrogen supply and promoting nitrogen absorption and growth of plants. Chitosan is a natural polysaccharide extracted from the shells of crustaceans. It is a bioactive material obtained after deacetylation. Modern agricultural research has shown that chitosan treatment can significantly promote seed germination, improve seed vitality, accelerate seedling formation, improve photosynthesis efficiency in plants, promote stem and leaf growth and the transport of photosynthetic products, and thus increase crop yield and quality. Chitosan has a regulatory function on plant nitrogen metabolism, can optimize the carbon-nitrogen ratio, promote the absorption and utilization of nitrogen by plants, especially increase the storage protein content of low-protein crops, and can also enhance the plant's tolerance to various abiotic stresses (such as salinity, heavy metals, etc.) and resistance to biotic stresses (such as diseases and insect pests) by inducing plants to produce broad-spectrum resistance and enhancing their own defense mechanisms.

[0069] The urease film coating agent of the present invention can cement loose sand into a new green artificial film layer with certain strength and good permeability. It also has the characteristics of good air permeability, water permeability, water retention, etc., is plant-friendly, and can promote the survival and growth of super-xerophytes in desert areas.

[0070] Comparative Example 2

[0071] This comparative example differs from Example 1 in step (4).

[0072] First, the modified soybean urease solution is sprayed on the desert soil surface at 3L / m², and then 1.5L / m² of the solidifying liquid is sprayed on the desert soil surface. Comparing the uniformity of the solidified film layer formed in Example 1 and this comparative example, it can be seen that spraying the soybean urease solution and the solidifying liquid in batches is not conducive to obtaining a uniform solidified film layer, and its anchoring effect on the sand is poor. This is mainly due to the strong permeability of the sand. The liquid sprayed for the first time will infiltrate quickly, while the liquid sprayed for the second time will infiltrate relatively more slowly. Therefore, the soybean urease solution and the solidifying liquid cannot infiltrate synchronously, resulting in the two components being unable to fully react and form calcium carbonate crystals, making it difficult to evenly cement the sand particles.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for treating desertified areas, characterized in that: It includes: S1. Divide the desertified area to be treated into zones to form a plurality of vegetation blocks and a plurality of urease-coated sandy soil blocks, wherein the vegetation blocks and the urease-coated sandy soil blocks are staggered and connected; S2. Planting super-xerophytes in the vegetation block, spraying urease film-forming agent on the surface of the urease film-forming sand block, the urease film-forming agent forms a sand-fixing film layer on the surface of the sand to strengthen the surface sand; The urease coating agent comprises two components, component one is a modified soybean urease solution, and component two is a solidifying liquid; the modified soybean urease solution comprises a soybean urease solution, starch grafted acrylic acid copolymer particles with a particle size distribution of 0-3 mm, and chitosan; the solidifying liquid comprises urea and calcium salt, and the calcium salt is a water-soluble calcium salt; After component one and component two are prepared, they are separately packed, and before spraying the urease coating agent, component one and component two are evenly mixed and sprayed in time; S3. Divide the planting area into two levels; divide the planting area into plant area and inter-row area, spray urease film-forming agent on the sandy soil surface between rows and plants to form a sand-fixing film layer; the amount of urease film-forming agent sprayed between rows and plants is 1 / 2~1 / 4 of the urease film-forming sandy soil area or Spray less than 2L / m² of urease film-forming agent within a radius of 5cm centered on the plant diameter, spray 3~4L / m² of urease film-forming agent outside the radius of 5cm, and spray 4~5 L / m² of urease film-forming agent in the urease-film-forming sandy soil area.

2. The treatment method according to claim 1, characterized in that: The plants planted in the vegetation blocks are super-xerophytes that are cold-resistant, drought-resistant, wind-erosion-resistant, sand-burying-resistant, fast-growing, have well-developed rhizomes, and are wind-proof and sand-fixing.

3. The treatment method according to claim 1, characterized in that: The preparation method of the modified soybean urease solution is as follows: Step 1: After drying the soybeans, crush them with a crusher and sieve them to obtain soybean powder; Step 2: Soak the soybean powder in water, let it stand for more than 2 hours, filter and remove the soybean powder residue, keep the filtrate, let the filtrate stand and retain the supernatant to obtain the soybean urease solution; Step 3: After adjusting the pH of the soybean urease solution to 5.5-6, starch grafted acrylic copolymer particles and chitosan with a particle size distribution of 0-3 mm are added, the final concentration of starch grafted acrylic copolymer particles is 0.5-1%, and the final concentration of chitosan is 0.5-2%, thereby obtaining a modified soybean urease solution.

4. The treatment method according to claim 1, characterized in that: The urease concentration in the modified soybean urease solution is 20-100 g / L.

5. The treatment method according to claim 4, characterized in that: The calcium salt in the solidifying liquid is at least one of calcium chloride, calcium acetate and calcium lactate; and the calcium ion concentration in the solidifying liquid is 0.03-0.1 mol / L.

6. The treatment method according to claim 5, characterized in that: The molar concentration ratio of urea to calcium ions in the solidifying liquid is 1:1, that is, the urea concentration is 0.03-0.1 mol / L.

7. The treatment method according to claim 1, characterized in that: The solidifying liquid is prepared by mixing a calcium salt solution and a urea solution according to a molar concentration of calcium salt to urea of ​​1:1, and the concentrations of urea and calcium ions are 0.03-0.1 mol / L, respectively. The pH of the solidifying liquid is adjusted to 5.5-6, and the solidifying liquid is placed for more than 3 hours after preparation is completed before use, but should be used up within 6 hours.

8. The treatment method according to claim 1, characterized in that: Before spraying the urease film-forming agent, measure component one and component two at a spraying rate of 1~5L / m² respectively. When mixing, the mixing volume ratio of component one to component two is 1:1~1:3, and the thickness of the sand-fixing film layer is 0.5cm~2.5cm.

9. The treatment method according to claim 1, characterized in that: The super-xerophytes are one or more of Ammopiptanthus mongolicus, red willow, aloe, cactus, poplar, Nitraria spp., and sea buckthorn; when planting super-xerophytes in vegetation blocks, the root density is adjusted according to the spacing of the planted plants, and fertilizers need to be applied to the sandy soil of the vegetation blocks before planting the plants, with a fertilization depth of 15 to 40 cm; fertilizers include new biofertilizers suitable for super-xerophytes, organic fertilizers, poultry or livestock manure, and nitrogen, phosphorus and potassium fertilizers.

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