Soil conditioner for improving fertility of saline-alkali soil and preparation method thereof

Abstract

The invention discloses a soil conditioner for improving fertility of saline-alkali soil and a preparation method thereof, and relates to the technical field of soil improvement. The soil conditioner for improving the fertility of the saline-alkali soil is prepared from a composite filler based on nitrogen-doped modified wood soil peat and zeolite and polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbent resin, the composite filler based on nitrogen-doped modified wood soil peat and zeolite is composed of an external nitrogen source, wood soil peat and zeolite, the composite filler based on nitrogen-doped modified wood soil peat and zeolite is physically crosslinked with polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbent resin to form a loose and porous resin matrix structure, so that the adsorption capacity and the water holding property of the composite resin are effectively improved, the concentration and the pH value of sodium ions in soil are reduced, and the soil quality is improved. The adverse effect of the high-salt and high-alkali problems on fertility is reduced, and the composite filler rich in organic matters can be slowly released, so that the fertility of the soil is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil improvement, and specifically refers to a soil conditioner for improving the fertility of saline-alkali land and a preparation method thereof. Background Art

[0002] Saline-alkali land often appears in arid and semi-arid areas. Saline-alkali soil has a high pH, ​​alkalinity and exchangeable sodium ion content, poor soil permeability and air permeability, low water use efficiency, less organic matter content, and lack of nutrients, which is not conducive to crop growth, resulting in low farmland productivity, restricting the development of sustainable agriculture, and posing a threat to the ecological environment. Soil salinization is usually accompanied by alkalization, leading to a more serious deterioration of soil properties. In the saline-alkali environment, excessive accumulation of sodium in the soil solution and active soil components leads to high soluble salt content and high soil alkalinity in the soil, and the soil salt content will continue to increase. Salt and alkali will cause soil compaction, poor soil permeability, and adverse effects on plant nutrient absorption, seriously restricting plant growth.

[0003] There are many reasons for soil salinization, including natural changes and human practical activities, such as natural disasters, seawater intrusion in coastal areas, high-salt groundwater irrigation and salt accumulation caused by insufficient leaching. In order to change the physical and chemical properties of the soil and the treatment effect, soil conditioners can be added to saline-alkali land to change the ionic composition of the soil, improve the soil structure, and accelerate salt leaching. Common soil conditioners can be divided into organic soil conditioners, inorganic soil conditioners, microbial soil conditioners and other types.

[0004] The existing technology currently has the following problems:

[0005] The treatment effect of a single soil conditioner is general and cannot effectively improve the sodium ion concentration and soil alkalinity of saline-alkali land, which is not conducive to the effective improvement of soil fertility. Summary of the invention

[0006] In view of the above situation, in order to overcome the defects of the prior art, the present invention proposes a soil conditioner for improving the fertility of saline-alkali land, comprising the following components in parts by weight: 50-60 parts of a composite filler based on nitrogen-doped modified wood soil peat and zeolite, and 20-30 parts of a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin.

[0007] The composite filler based on nitrogen-doped modified wood soil peat and zeolite comprises the following components in parts by weight: 60-80 parts of external nitrogen source, 20-40 parts of wood soil peat, and 20-40 parts of zeolite.

[0008] The preparation method of the composite filler based on nitrogen-doped modified wood soil peat and zeolite specifically comprises the following steps:

[0009] (1) Mix 60.0-80.0g of external nitrogen source with 2.0-4.0g of wood soil peat, crush them, add them to a beaker containing 80-100mL of 4% hydrochloric acid solution, stir them at room temperature for 0.5-1h, seal the beaker with plastic wrap, and perform ultrasonic treatment for 1-2h to allow the substances in the beaker to fully contact and mix, then place them on a heated magnetic stirrer and stir them at high speed and heat them in a water bath to 60-80℃ until the water in the mixture is basically evaporated, take out the mixed solids, vacuum dry them, grind them, and then add the wood soil peat. It is a natural organic mineral formed by plant and tree residues in a humid, anaerobic environment. It is loose and porous in structure and contains a large amount of humic acid. It can increase the organic matter content in the soil and improve the saline-alkali environment of the soil. The doping of nitrogen elements further improves the specific surface area and pores of the original wood soil peat, increases the elemental composition, enriches the surface functional groups, and is conducive to the increase of adsorption sites. At the same time, acid treatment can also increase the variable charge on the surface of wood soil peat, and also has a positive effect on the adsorption of sodium ions, thus obtaining nitrogen-doped acid-modified wood soil peat.

[0010] (2) Add the nitrogen-doped acid-modified wood soil peat described in step (1) into a beaker containing 80-100 mL of 4% hydrochloric acid solution, stir at room temperature for 0.5-1 h, then add 2.0-4.0 g of zeolite powder, seal the beaker with plastic wrap, stir for 20-30 min, then perform ultrasonic treatment for 1-2 h, centrifuge, wash the precipitate with ultrapure water 3-5 times, collect the filter cake, vacuum dry, and grind. Zeolite has wide pores and channels. After being compounded with the nitrogen-doped acid-modified wood soil peat, its surface is more The roughening increases the exposed area, thereby increasing the adsorption sites in the structure and improving the adsorption capacity, which is conducive to better adsorption and removal of salt ions such as sodium ions in the soil. In addition, on the one hand, the phenolic hydroxyl group, carboxylic acid group and other groups in the nitrogen-doped acid-modified wood soil peat release hydrogen ions into the water through the exchange of adsorbed cations, and on the other hand, the Si-OH and Al-OH groups introduced by the zeolite can also release hydrogen ions through exchange, thereby effectively reducing the pH value and alkalinity of the soil, and obtaining a composite filler based on nitrogen-doped modified wood soil peat and zeolite;

[0011] Preferably, in step (1), the external nitrogen source is any one of dicyandiamide and urea or a mixture thereof. The main functions of the external nitrogen source include providing nitrogen source, promoting plant growth and improving soil properties.

[0012] The present invention also provides a method for preparing a soil conditioner for improving the fertility of saline-alkali land, which specifically comprises the following steps:

[0013] S1. Add 100 mL of deionized water to a beaker, preheat it in a water bath at 65-75°C, and slowly add 1.0-2.0 g of polyvinyl alcohol under magnetic stirring. Adding it too quickly will cause the polyvinyl alcohol to precipitate. After it is fully added, the temperature is raised to 90°C until the polyvinyl alcohol is completely dissolved. Polyvinyl alcohol can be used as a soil conditioner to improve the soil quality of saline-alkali land by improving soil structure, soil fertility and water retention, and improving soil biological activity. A polyvinyl alcohol solution is obtained;

[0014] S2, add 2.5g potassium hydroxide to 10mL deionized water, stir magnetically until it reaches room temperature, add 4mL acrylic acid liquid, continue stirring to cool to room temperature, then add 1.0g acrylamide, stir until completely dissolved, and use as solution I, measure 4-8mL of the polyvinyl alcohol solution described in step S1, add sodium alginate thereto, continue magnetic stirring, heat to 40-50°C, then dissolve 80mg ammonium persulfate in 4mL deionized water, and then add it to the reactant, then raise the temperature of the reaction mixture to 65°C, add solution I, continue to maintain at 65°C while stirring 30-50min, ammonium persulfate is thermally decomposed to produce sulfate radicals, and the hydroxyl groups on the sodium alginate molecular chain are extracted hydrogen atoms by the free radicals to form macromolecular free radicals, which undergo chain growth reactions with other monomers. Polyvinyl alcohol, as a hydrophilic linear segment, interpenetrates and intersperses with the polymer network. The interpenetrating structure significantly enhances the hydrophilicity of the network. After swelling, the composite resin entangles with the soil to form a colloid, which improves the soil's adsorption of salt and interception of water, prevents water from infiltrating or losing, and effectively improves soil salinization, thereby facilitating the improvement of soil fertility, thereby obtaining a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin;

[0015] S3, adding the composite filler based on nitrogen-doped modified wood soil peat and zeolite and N,N'-methylenebisacrylamide to the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin described in step S2, maintaining the reaction temperature at 55-65°C, stirring and reacting for 2-3h, collecting the product, repeatedly washing it with a 95% ethanol solution for 3-5 times, vacuum drying, and then crushing it, the mesh size is 60-80 mesh, the composite filler based on nitrogen-doped modified wood soil peat and zeolite acts as a physical crosslinking agent, and is fully integrated into The polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin network is evenly distributed on the surface and inside of the composite resin, producing a porous effect, presenting a rich pore structure, greatly increasing the specific surface area, and significantly enhancing the adsorption capacity and water absorption and water holding capacity. At the same time, the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin is used as a matrix, which has a certain slow-release performance, avoiding the root burning and other adverse fertilization effects caused by the large-scale release of wood soil and peat, thereby effectively improving soil fertility, and obtaining a soil conditioner for improving the fertility of saline-alkali land;

[0016] Preferably, in step S2, the amount of sodium alginate added is 0.4-0.6 g. As a biological organic fertilizer, sodium alginate can increase the organic matter content in the soil. Sodium alginate can absorb harmful substances such as salt and heavy metals in the soil, thereby improving the water storage capacity of the soil and improving the salinity of the soil. Sodium alginate can also reduce the pH value of the soil, making it more suitable for plant growth;

[0017] Preferably, in step S3, the amount of N,N'-methylenebisacrylamide added is 10-20 mg. N,N'-methylenebisacrylamide acts as a chemical cross-linking agent to improve the stability of the interpenetrating network structure.

[0018] The beneficial effects achieved by the present invention are as follows:

[0019] The present invention forms a loose and porous resin matrix structure by physically cross-linking a composite filler based on nitrogen-doped modified wood soil peat and zeolite with a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin, thereby effectively improving the adsorption capacity and water holding performance of the composite resin, reducing the sodium ion concentration and pH value in the soil, reducing the adverse effects of high salt and high alkali problems on fertility, and can also slowly release the composite filler rich in organic matter, thereby significantly improving the fertility of the soil; in the composite filler based on nitrogen-doped modified wood soil peat and zeolite, the wood soil peat is firstly subjected to acid treatment and nitrogen doping modification, thereby improving the specific surface area and pores of the wood soil peat, enriching the surface functional groups, and increasing the variable charge on the surface, which is conducive to increasing The adsorption sites and the adsorption capacity of sodium ions are improved. At the same time, the external nitrogen source also supplements the nitrogen fertilizer, which is beneficial to improve the soil fertility. The wide pores of the zeolite are then used to composite with the modified wood soil peat to make its surface rougher and increase the exposed area, thereby increasing the adsorption sites and improving the adsorption capacity, which can not only reduce the loss of nutrients, but also better adsorb and remove salt ions such as sodium ions in the soil, reduce the sodium ion concentration in the soil, and the phenolic hydroxyl, carboxylic acid group and Si-OH, Al-OH groups contained in the composite release hydrogen ions into the water through the exchange of adsorbed cations, effectively reducing the pH value and alkalinity of the soil; in the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin, Sodium alginate reacts with monomers such as ammonium persulfate to form a chain growth reaction. Polyvinyl alcohol, as a hydrophilic linear chain segment, forms a mutually penetrating polymer network, which enhances hydrophilicity and swelling properties, improves soil adsorption of salt and interception of water, prevents water infiltration or loss, effectively improves soil salinization, and is also beneficial to the improvement of fertility. In addition, the polymer network is further improved under the cross-linking effect of N, N'-methylenebisacrylamide. The structural stability is further improved, and the composite filler based on nitrogen-doped modified wood soil peat and zeolite is dispersed on the surface and inside of the composite resin, acting as a physical cross-linking agent to produce a porous effect, thereby presenting a richer pore structure and greatly increasing the specific surface area. The adsorption capacity and water absorption and water holding capacity are significantly enhanced. At the same time, the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin is used as the matrix, and has a certain slow-release performance. The composite filler based on nitrogen-doped modified wood soil peat and zeolite can be released, which can not only effectively play the role of the filler in improving soil salinization and fertility, but also avoid the adverse effects such as root burning caused by large-scale release. The present invention uses a composite filler based on nitrogen-doped modified wood soil peat and zeolite and a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin to prepare a soil conditioner for improving the fertility of saline-alkali land, which reduces the sodium ion concentration and pH value in the soil, effectively improves the salinization problem, has excellent water absorption and water holding performance, and significantly improves soil fertility. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a scanning electron microscope image of the soil conditioner for improving the fertility of saline-alkali land prepared in Example 1 of the present invention;

[0021] Figure 2 The diagram is a diagram showing the improvement results of salinization in Examples 1-4 and Comparative Examples 1-3 of the present invention;

[0022] Figure 3 The maximum water holding capacity results of Examples 1-4 and Comparative Examples 1-3 of the present invention are shown in FIG.

[0023] Figure 4 It is a graph showing the organic matter content results of Examples 1-4 of the present invention and Comparative Examples 1-3. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein may be applied to the present invention. The preferred implementation methods and materials described herein are for demonstration purposes only and are not intended to limit the content of this application.

[0026] The experimental methods in the following examples are conventional methods unless otherwise specified; the experimental materials used in the following examples are purchased from commercial channels unless otherwise specified.

[0027] Example 1

[0028] This embodiment proposes a soil conditioner for improving the fertility of saline-alkali land, comprising the following components in parts by weight: 60 parts of a composite filler based on nitrogen-doped modified wood soil peat and zeolite, and 30 parts of a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin.

[0029] The composite filler based on nitrogen-doped modified wood soil peat and zeolite comprises the following components in parts by weight: 80 parts of external nitrogen source, 40 parts of wood soil peat, and 20 parts of zeolite.

[0030] The preparation method of the composite filler based on nitrogen-doped modified wood soil peat and zeolite specifically comprises the following steps:

[0031] (1) 80.0 g of external nitrogen source was mixed with 4.0 g of wood soil peat, and crushed. The external nitrogen source was a mixture of dicyandiamide and urea. The main functions of the external nitrogen source include providing nitrogen source, promoting plant growth and improving soil properties. Add it to a beaker containing 100 mL of 4% hydrochloric acid solution, stir at room temperature for 1 hour, seal the beaker with plastic wrap, and perform ultrasonic treatment for 2 hours to allow the substances in the beaker to fully contact and mix. Then place it on a heatable magnetic stirrer and stir at high speed and heat it in a water bath to 80°C until the water in the mixture is basically evaporated. Take out the mixed solid and put it into Vacuum drying and grinding are performed. Peat is a natural organic mineral formed by plant and tree residues in a humid, anaerobic environment. It is loose and porous in structure and contains a large amount of humic acid, which can increase the organic matter content in the soil and improve the saline-alkali environment of the soil. The specific surface area and pores of the original peat are further improved by the doping of nitrogen elements, the element composition is increased, the surface functional groups are enriched, and it is beneficial to increase the adsorption sites. At the same time, acid treatment can also increase the variable charge on the surface of peat, and also have a positive effect on the adsorption of sodium ions, so as to obtain nitrogen-doped acid-modified peat.

[0032] (2) The nitrogen-doped acid-modified wood soil peat described in step (1) is added to a beaker containing 100 mL of a 4% hydrochloric acid solution, stirred at room temperature for 1 hour, and then 2.0 g of zeolite powder is added. The beaker is sealed with plastic wrap, stirred for 30 minutes, and then ultrasonically treated for 2 hours. Centrifugation is performed, and the precipitate is washed with ultrapure water 5 times. The filter cake is collected, vacuum dried, and ground. Zeolite has wide pores and channels. After being composited with the nitrogen-doped acid-modified wood soil peat, its surface becomes rougher and the exposed area increases, thereby increasing the adsorption sites in the structure and improving the adsorption capacity, which is conducive to better adsorption and removal of salt ions such as sodium ions in the soil. In addition, on the one hand, the phenolic hydroxyl group, carboxylic acid group and other groups in the nitrogen-doped acid-modified wood soil peat release hydrogen ions into the water through the exchange of adsorbed cations. On the other hand, the Si-OH and Al-OH groups introduced by the zeolite can also release hydrogen ions through exchange, thereby effectively reducing the pH value and alkalinity of the soil, thereby obtaining a composite filler based on nitrogen-doped modified wood soil peat and zeolite.

[0033] This embodiment provides a method for preparing a soil conditioner for improving the fertility of saline-alkali land, which specifically comprises the following steps:

[0034] S1. Add 100 mL of deionized water to a beaker, preheat it in a water bath at 75°C, and slowly add 2.0 g of polyvinyl alcohol under magnetic stirring. Adding it too quickly will cause the polyvinyl alcohol to precipitate. After it is fully added, the temperature is raised to 90°C until the polyvinyl alcohol is completely dissolved. Polyvinyl alcohol can be used as a soil conditioner to improve the soil quality of saline-alkali land by improving soil structure, soil fertility and water retention, and increasing soil biological activity. A polyvinyl alcohol solution is obtained;

[0035] S2, add 2.5g potassium hydroxide to 10mL deionized water, stir magnetically until it reaches room temperature, add 4mL acrylic acid liquid, continue stirring to cool to room temperature, then add 1.0g acrylamide, stir until completely dissolved, and use as solution I, measure 8mL of the polyvinyl alcohol solution described in step S1, add sodium alginate thereto, the amount of sodium alginate added is 0.6g, sodium alginate as a biological organic fertilizer, can increase the organic matter content in the soil, sodium alginate can absorb harmful substances such as salt and heavy metals in the soil, thereby improving the water storage capacity of the soil and improving the salinity of the soil. Sodium alginate can also reduce the pH value of the soil, making it more suitable for plant growth, continue magnetic stirring, heat to 50°C, and then dissolve 80mg ammonium persulfate first The mixture was added to 4 mL of deionized water and then added to the reactants. The temperature of the reaction mixture was then raised to 65° C. Solution I was added and the mixture was kept at 65° C. and stirred for 50 min. Ammonium persulfate was thermally decomposed to generate sulfate radicals. Hydrogen atoms were extracted by the hydroxyl groups on the sodium alginate molecular chains by the free radicals to form macromolecular free radicals. The free radicals then reacted with other monomers to form chain growth reactions. Polyvinyl alcohol, as a hydrophilic linear segment, interpenetrated and interspersed with the polymer network. The interpenetrating structure significantly enhanced the hydrophilicity of the network. After swelling, the composite resin was entangled with the soil to form a colloid, which improved the soil's adsorption of salt and interception of water, prevented water from seeping in or running off, effectively improved soil salinization, and was beneficial to the improvement of soil fertility. Thus, a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin was obtained.

[0036] S3, adding the composite filler based on nitrogen-doped modified wood soil peat and zeolite and N,N'-methylenebisacrylamide to the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin described in step S2, the amount of N,N'-methylenebisacrylamide added is 20 mg, N,N'-methylenebisacrylamide acts as a chemical cross-linking agent to improve the stability of the interpenetrating network structure, maintaining the reaction temperature at 65°C, stirring and reacting for 3 hours, collecting the product, repeatedly washing it with a mass fraction of 95% ethanol solution for 5 times, vacuum drying, and then crushing it, the mesh size is 80 mesh, based on nitrogen doping The composite filler of modified wood soil peat and zeolite acts as a physical cross-linking agent, which is fully integrated into the network of polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin and evenly distributed on the surface and inside of the composite resin, producing a porous effect and presenting a rich pore structure, which greatly increases the specific surface area and significantly enhances the adsorption capacity and water absorption and water holding capacity. At the same time, the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin is used as the matrix and has certain slow-release properties, thereby avoiding adverse fertilization effects such as root burning caused by the large-scale release of wood soil peat, thereby effectively improving soil fertility and obtaining a soil conditioner for improving the fertility of saline-alkali land.

[0037] In this embodiment, the prepared soil conditioner for improving the fertility of saline-alkali land was subjected to scanning electron microscopy to observe its microscopic morphology. Figure 1 This is a SEM image of the soil conditioner for improving the fertility of saline-alkali land prepared in Example 1, magnified 1000 times. Figure 1 The soil conditioner for improving the fertility of saline-alkali land prepared in this embodiment presents an interconnected porous structure.

[0038] Example 2

[0039] This embodiment proposes a soil conditioner for improving the fertility of saline-alkali land, comprising the following components in parts by weight: 50 parts of a composite filler based on nitrogen-doped modified wood soil peat and zeolite, and 20 parts of a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin.

[0040] The composite filler based on nitrogen-doped modified wood soil peat and zeolite comprises the following components in parts by weight: 60 parts of external nitrogen source, 20 parts of wood soil peat, and 40 parts of zeolite.

[0041] The preparation method of the composite filler based on nitrogen-doped modified wood soil peat and zeolite specifically comprises the following steps:

[0042] (1) 60.0 g of external nitrogen source was mixed with 2.0 g of wood soil peat, crushed, and added to a beaker containing 80 mL of 4% hydrochloric acid solution, stirred at room temperature for 0.5 h, sealed the beaker with plastic wrap, and subjected to ultrasonic treatment for 1 h to allow the substances in the beaker to fully contact and mix, then placed on a heated magnetic stirrer, stirred at high speed, and heated in a water bath to 60 °C until the water in the mixture was basically evaporated, and the mixed solid was taken out for vacuum evaporation. Drying, grinding, wood soil peat is a natural organic mineral formed by plant and tree residues in a humid, anaerobic environment. It is loose and porous in structure and contains a large amount of humic acid, which can increase the organic matter content in the soil and improve the saline-alkali environment of the soil. The specific surface area and pores of the original wood soil peat are further improved by the doping of nitrogen elements, the element composition is increased, the surface functional groups are enriched, and it is beneficial to increase the adsorption sites. At the same time, acid treatment can also increase the variable charge on the surface of wood soil peat, and also have a positive effect on the adsorption of sodium ions, so as to obtain nitrogen-doped acid-modified wood soil peat;

[0043] (2) The nitrogen-doped acid-modified wood soil peat described in step (1) is added to a beaker containing 80 mL of a 4% hydrochloric acid solution, stirred at room temperature for 0.5 h, then 4.0 g of zeolite powder is added, the beaker is sealed with plastic wrap, stirred for 20 min, and then ultrasonically treated for 1 h, centrifuged, and the precipitate is washed 3 times with ultrapure water. The filter cake is collected, vacuum dried, and ground. Zeolite has wide pores and channels. After being composited with the nitrogen-doped acid-modified wood soil peat, its surface becomes rougher and the exposed area increases, thereby increasing the adsorption sites in the structure and improving the adsorption capacity, which is conducive to better adsorption and removal of salt ions such as sodium ions in the soil. In addition, on the one hand, the phenolic hydroxyl group, carboxylic acid group and other groups in the nitrogen-doped acid-modified wood soil peat release hydrogen ions into the water through the exchange of adsorbed cations. On the other hand, the Si-OH and Al-OH groups introduced by the zeolite can also release hydrogen ions through exchange, thereby effectively reducing the pH value and alkalinity of the soil, thereby obtaining a composite filler based on nitrogen-doped modified wood soil peat and zeolite.

[0044] This embodiment provides a method for preparing a soil conditioner for improving the fertility of saline-alkali land, which specifically comprises the following steps:

[0045] S1. Add 100 mL of deionized water to a beaker, preheat it in a water bath at 65°C, and slowly add 1.0 g of polyvinyl alcohol under magnetic stirring. Adding it too quickly will cause the polyvinyl alcohol to precipitate. After it is fully added, the temperature is raised to 90°C until the polyvinyl alcohol is completely dissolved. Polyvinyl alcohol can be used as a soil conditioner to improve the soil quality of saline-alkali land by improving soil structure, soil fertility and water retention, and improving soil biological activity. A polyvinyl alcohol solution is obtained;

[0046] S2, add 2.5g potassium hydroxide to 10mL deionized water, stir magnetically until it reaches room temperature, add 4mL acrylic acid liquid, continue stirring to cool to room temperature, then add 1.0g acrylamide, stir until completely dissolved, and use as solution I, measure 4mL of the polyvinyl alcohol solution described in step S1, add sodium alginate thereto, the amount of sodium alginate added is 0.4g, sodium alginate as a biological organic fertilizer, can increase the organic matter content in the soil, sodium alginate can absorb harmful substances such as salt and heavy metals in the soil, thereby improving the water storage capacity of the soil and improving the salinity of the soil. Sodium alginate can also reduce the pH value of the soil, making it more suitable for plant growth, continue magnetic stirring, heat to 40°C, and then dissolve 80mg ammonium persulfate first The mixture was added to 4 mL of deionized water and then added to the reactants. The temperature of the reaction mixture was then raised to 65° C. Solution I was added and the mixture was kept at 65° C. and stirred for 30 min. Ammonium persulfate was thermally decomposed to generate sulfate radicals. Hydrogen atoms were extracted by the hydroxyl groups on the sodium alginate molecular chains to form macromolecular radicals. The radicals then reacted with other monomers to form chain growth reactions. Polyvinyl alcohol, as a hydrophilic linear segment, interpenetrated and interspersed with the polymer network. The interpenetrating structure significantly enhanced the hydrophilicity of the network. After swelling, the composite resin was entangled with the soil to form a colloid, which improved the soil's adsorption of salt and interception of water, prevented water from seeping in or running off, effectively improved soil salinization, and was beneficial to the improvement of fertility. Thus, a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin was obtained.

[0047] S3, adding the composite filler based on nitrogen-doped modified wood soil peat and zeolite and N,N'-methylenebisacrylamide to the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin described in step S2, the amount of N,N'-methylenebisacrylamide added is 10 mg, N,N'-methylenebisacrylamide acts as a chemical cross-linking agent to improve the stability of the interpenetrating network structure, maintaining the reaction temperature at 55°C, stirring and reacting for 2 hours, collecting the product, repeatedly washing it with a mass fraction of 95% ethanol solution for 3 times, vacuum drying, and then crushing it, the mesh size is 60 mesh, based on nitrogen doping The composite filler of modified wood soil peat and zeolite acts as a physical cross-linking agent, which is fully integrated into the network of polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin and evenly distributed on the surface and inside of the composite resin, producing a porous effect and presenting a rich pore structure, which greatly increases the specific surface area and significantly enhances the adsorption capacity and water absorption and water holding capacity. At the same time, the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin is used as the matrix and has certain slow-release properties, thereby avoiding adverse fertilization effects such as root burning caused by the large-scale release of wood soil peat, thereby effectively improving soil fertility and obtaining a soil conditioner for improving the fertility of saline-alkali land.

[0048] Example 3

[0049] This embodiment proposes a soil conditioner for improving the fertility of saline-alkali land, comprising the following components in parts by weight: 55 parts of a composite filler based on nitrogen-doped modified wood soil peat and zeolite, and 25 parts of a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin.

[0050] The composite filler based on nitrogen-doped modified wood soil peat and zeolite comprises the following components in parts by weight: 70 parts of external nitrogen source, 30 parts of wood soil peat, and 30 parts of zeolite.

[0051] The preparation method of the composite filler based on nitrogen-doped modified wood soil peat and zeolite specifically comprises the following steps:

[0052] (1) Mix 70.0 g of external nitrogen source with 3.0 g of peat moss, crush them, and add them into a beaker containing 90 mL of 4% hydrochloric acid solution. Stir for 0.75 h at room temperature. Seal the beaker with plastic wrap and perform ultrasonic treatment for 1.5 h to allow the substances in the beaker to fully contact and mix. Then place the mixture on a heated magnetic stirrer and stir at high speed. Heat the mixture in a water bath to 70 °C until the water in the mixture is basically evaporated. Take out the mixed solid and vacuum evaporation. Air drying, grinding, wood soil peat is a natural organic mineral formed by plant and tree residues in a humid, anaerobic environment. It is loose and porous in structure and contains a large amount of humic acid, which can increase the organic matter content in the soil and improve the saline-alkali environment of the soil. The specific surface area and pores of the original wood soil peat are further improved by the doping of nitrogen elements, the element composition is increased, the surface functional groups are enriched, and it is beneficial to increase the adsorption sites. At the same time, acid treatment can also increase the variable charge on the surface of wood soil peat, and also have a positive effect on the adsorption of sodium ions, so as to obtain nitrogen-doped acid-modified wood soil peat;

[0053] (2) Add the nitrogen-doped acid-modified wood soil peat described in step (1) into a beaker containing 90 mL of 4% hydrochloric acid solution, stir at room temperature for 0.75 h, then add 3.0 g of zeolite powder, seal the beaker with plastic wrap, stir for 25 min, and then perform ultrasonic treatment for 1.5 h. Centrifuge, wash the precipitate with ultrapure water 4 times, collect the filter cake, vacuum dry, and grind. Zeolite has wide pores and channels. After being compounded with the nitrogen-doped acid-modified wood soil peat, its surface becomes rougher and the exposed surface The area increases, thereby increasing the adsorption sites in the structure and improving the adsorption capacity, which is conducive to better adsorption and removal of salt ions such as sodium ions in the soil. In addition, on the one hand, the phenolic hydroxyl group, carboxylic acid group and other groups in the nitrogen-doped acid-modified wood soil peat release hydrogen ions into the water through the exchange of adsorbed cations. On the other hand, the Si-OH and Al-OH groups introduced by the zeolite can also release hydrogen ions through exchange, thereby effectively reducing the pH value and alkalinity of the soil, and obtaining a composite filler based on nitrogen-doped modified wood soil peat and zeolite.

[0054] This embodiment provides a method for preparing a soil conditioner for improving the fertility of saline-alkali land, which specifically comprises the following steps:

[0055] S1. Add 100 mL of deionized water to a beaker, preheat it in a water bath at 70°C, and slowly add 1.5 g of polyvinyl alcohol under magnetic stirring. Adding it too quickly will cause the polyvinyl alcohol to precipitate. After it is fully added, the temperature is raised to 90°C until the polyvinyl alcohol is completely dissolved. Polyvinyl alcohol can be used as a soil conditioner to improve the soil quality of saline-alkali land by improving soil structure, soil fertility and water retention, and increasing soil biological activity. A polyvinyl alcohol solution is obtained;

[0056] S2, add 2.5g potassium hydroxide to 10mL deionized water, stir magnetically until it reaches room temperature, add 4mL acrylic acid liquid, continue stirring to cool to room temperature, then add 1.0g acrylamide, stir until completely dissolved, and use as solution I, measure 6mL of the polyvinyl alcohol solution described in step S1, add sodium alginate thereto, the amount of sodium alginate added is 0.5g, sodium alginate as a biological organic fertilizer, can increase the organic matter content in the soil, sodium alginate can absorb harmful substances such as salt and heavy metals in the soil, thereby improving the water storage capacity of the soil and improving the salinity of the soil. Sodium alginate can also reduce the pH value of the soil, making it more suitable for plant growth, continue magnetic stirring, heat to 45°C, and then dissolve 80mg ammonium persulfate first The mixture was added to 4 mL of deionized water and then added to the reactants. The temperature of the reaction mixture was then raised to 65° C. Solution I was added and the mixture was kept at 65° C. and stirred for 40 min. Ammonium persulfate was thermally decomposed to generate sulfate radicals. Hydrogen atoms on the hydroxyl groups of the sodium alginate molecular chains were extracted by the free radicals to form macromolecular free radicals, which then underwent chain growth reactions with other monomers. Polyvinyl alcohol, as a hydrophilic linear segment, interpenetrated and interspersed with the polymer network. The interpenetrating structure significantly enhanced the hydrophilicity of the network. After swelling, the composite resin was entangled with the soil to form a colloid, which improved the soil's adsorption of salt and interception of water, prevented water from seeping in or running off, effectively improved soil salinization, and was beneficial to the improvement of soil fertility. Thus, a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin was obtained.

[0057] S3, adding the composite filler based on nitrogen-doped modified wood soil peat and zeolite and N,N'-methylenebisacrylamide to the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin described in step S2, the amount of N,N'-methylenebisacrylamide added is 15 mg, N,N'-methylenebisacrylamide acts as a chemical cross-linking agent to improve the stability of the interpenetrating network structure, maintaining the reaction temperature at 60°C, stirring and reacting for 2.5 hours, collecting the product, repeatedly washing it with 95% ethanol solution by mass for 4 times, vacuum drying, and then crushing it, the mesh size is 70 mesh, based on nitrogen doping The composite filler of hetero-modified wood soil peat and zeolite acts as a physical cross-linking agent, is fully integrated into the network of polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin, and is evenly distributed on the surface and inside of the composite resin, producing a porous effect, presenting a rich pore structure, greatly increasing the specific surface area, and significantly enhancing the adsorption capacity and water absorption and water holding capacity. At the same time, the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin is used as the matrix, which has certain slow-release properties, avoiding adverse fertilization effects such as root burning caused by the large amount of release of wood soil peat, thereby effectively improving soil fertility and obtaining a soil conditioner for improving the fertility of saline-alkali land.

[0058] Example 4

[0059] This embodiment proposes a soil conditioner for improving the fertility of saline-alkali land, comprising the following components in parts by weight: 60 parts of a composite filler based on nitrogen-doped modified wood soil peat and zeolite, and 20 parts of a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin.

[0060] The composite filler based on nitrogen-doped modified wood soil peat and zeolite comprises the following components in parts by weight: 60 parts of external nitrogen source, 40 parts of wood soil peat, and 20 parts of zeolite.

[0061] The preparation method of the composite filler based on nitrogen-doped modified wood soil peat and zeolite specifically comprises the following steps:

[0062] (1) Mix 60.0 g of external nitrogen source with 4.0 g of wood soil peat, crush them, and add them into a beaker containing 100 mL of 4% hydrochloric acid solution. Stir for 0.5 h at room temperature, seal the beaker with plastic wrap, and perform ultrasonic treatment for 1 h to allow the substances in the beaker to fully contact and mix. Then, place it on a heatable magnetic stirrer and stir at high speed and heat it in a water bath to 80 °C until the water in the mixture is basically evaporated. Take out the mixed solid. Vacuum drying and grinding are performed. Peat is a natural organic mineral formed by plant and tree residues in a moist, anaerobic environment. It is loose and porous in structure and contains a large amount of humic acid, which can increase the organic matter content in the soil and improve the saline-alkali environment of the soil. The specific surface area and pores of the original peat are further improved by the doping of nitrogen elements, the element composition is increased, the surface functional groups are enriched, and it is beneficial to increase the adsorption sites. At the same time, acid treatment can also increase the variable charge on the surface of peat, and also have a positive effect on the adsorption of sodium ions, so as to obtain nitrogen-doped acid-modified peat.

[0063] (2) The nitrogen-doped acid-modified wood soil peat described in step (1) is added to a beaker containing 100 mL of a 4% hydrochloric acid solution, stirred at room temperature for 0.5 h, then 2.0 g of zeolite powder is added, the beaker is sealed with plastic wrap, stirred for 20 min, and then ultrasonically treated for 1 h, centrifuged, and the precipitate is washed 5 times with ultrapure water. The filter cake is collected, vacuum dried, and ground. Zeolite has wide pores and channels. After being composited with the nitrogen-doped acid-modified wood soil peat, its surface becomes rougher and the exposed area increases, thereby increasing the adsorption sites in the structure and improving the adsorption capacity, which is conducive to better adsorption and removal of salt ions such as sodium ions in the soil. In addition, on the one hand, the phenolic hydroxyl groups, carboxylic acid groups and other groups in the nitrogen-doped acid-modified wood soil peat release hydrogen ions into the water through the exchange of adsorbed cations. On the other hand, the Si-OH and Al-OH groups introduced by the zeolite can also release hydrogen ions through exchange, thereby effectively reducing the pH value and alkalinity of the soil, thereby obtaining a composite filler based on nitrogen-doped modified wood soil peat and zeolite.

[0064] This embodiment provides a method for preparing a soil conditioner for improving the fertility of saline-alkali land, which specifically comprises the following steps:

[0065] S1. Add 100 mL of deionized water to a beaker, preheat it in a water bath at 75°C, and slowly add 1.0 g of polyvinyl alcohol under magnetic stirring. Adding it too quickly will cause the polyvinyl alcohol to precipitate. After it is fully added, the temperature is raised to 90°C until the polyvinyl alcohol is completely dissolved. Polyvinyl alcohol can be used as a soil conditioner to improve the soil quality of saline-alkali land by improving soil structure, soil fertility and water retention, and increasing soil biological activity. A polyvinyl alcohol solution is obtained;

[0066] S2, add 2.5g potassium hydroxide to 10mL deionized water, stir magnetically until it reaches room temperature, add 4mL acrylic acid liquid, continue stirring to cool to room temperature, then add 1.0g acrylamide, stir until completely dissolved, and use as solution I, measure 8mL of the polyvinyl alcohol solution described in step S1, add sodium alginate thereto, the amount of sodium alginate added is 0.6g, sodium alginate as a biological organic fertilizer, can increase the organic matter content in the soil, sodium alginate can absorb harmful substances such as salt and heavy metals in the soil, thereby improving the water storage capacity of the soil and improving the salinity of the soil. Sodium alginate can also reduce the pH value of the soil, making it more suitable for plant growth, continue magnetic stirring, heat to 50°C, and then dissolve 80mg ammonium persulfate first The mixture was added to 4 mL of deionized water and then added to the reactants. The temperature of the reaction mixture was then raised to 65° C. Solution I was added and the mixture was kept at 65° C. and stirred for 30 min. Ammonium persulfate was thermally decomposed to generate sulfate radicals. Hydrogen atoms were extracted by the hydroxyl groups on the sodium alginate molecular chains to form macromolecular radicals. The radicals then reacted with other monomers to form chain growth reactions. Polyvinyl alcohol, as a hydrophilic linear segment, interpenetrated and interspersed with the polymer network. The interpenetrating structure significantly enhanced the hydrophilicity of the network. After swelling, the composite resin was entangled with the soil to form a colloid, which improved the soil's adsorption of salt and interception of water, prevented water from seeping in or running off, effectively improved soil salinization, and was beneficial to the improvement of fertility. Thus, a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin was obtained.

[0067] S3, adding the composite filler based on nitrogen-doped modified wood soil peat and zeolite and N,N'-methylenebisacrylamide to the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin described in step S2, the amount of N,N'-methylenebisacrylamide added is 10 mg, N,N'-methylenebisacrylamide acts as a chemical cross-linking agent to improve the stability of the interpenetrating network structure, maintaining the reaction temperature at 65°C, stirring and reacting for 2 hours, collecting the product, repeatedly washing it with a mass fraction of 95% ethanol solution for 5 times, vacuum drying, and then crushing it, the mesh size is 80 mesh, based on nitrogen doping The composite filler of modified wood soil peat and zeolite acts as a physical cross-linking agent, which is fully integrated into the network of polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin and evenly distributed on the surface and inside of the composite resin, producing a porous effect and presenting a rich pore structure, which greatly increases the specific surface area and significantly enhances the adsorption capacity and water absorption and water holding capacity. At the same time, the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin is used as the matrix and has certain slow-release properties, thereby avoiding adverse fertilization effects such as root burning caused by the large-scale release of wood soil peat, thereby effectively improving soil fertility and obtaining a soil conditioner for improving the fertility of saline-alkali land.

[0068] Comparative Example 1

[0069] This comparative example provides a soil conditioner for improving the fertility of saline-alkali land. The difference between it and Example 1 is that the soil conditioner for improving the fertility of saline-alkali land does not contain a composite filler based on nitrogen-doped modified wood soil peat and zeolite; the preparation method of the soil conditioner for improving the fertility of saline-alkali land is the same as that of Example 1.

[0070] Comparative Example 2

[0071] This comparative example provides a soil conditioner for improving the fertility of saline-alkali land, which differs from Example 1 in that the composite filler based on nitrogen-doped modified wood soil peat and zeolite does not contain zeolite; the preparation method of the composite filler based on nitrogen-doped modified wood soil peat and zeolite does not include step (2); the preparation method of the soil conditioner for improving the fertility of saline-alkali land is the same as that of Example 1.

[0072] Comparative Example 3

[0073] This comparative example provides a soil conditioner for improving the fertility of saline-alkali land, which differs from Example 1 in that the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin does not contain sodium alginate; the preparation method of the composite filler based on nitrogen-doped modified wood soil peat and zeolite is the same as that of Example 1; and sodium alginate is not added in the preparation method S2 of the soil conditioner for improving the fertility of saline-alkali land.

[0074] Experimental Example 1

[0075] Salinization improvement experiment

[0076] Test sample: Soil conditioner for improving fertility of saline-alkali land prepared in Examples 1-4 and Comparative Examples 1-3.

[0077] Test method: Dissolve NaHCO3 solid in ultrapure water to prepare a 1000 mg / L sodium stock solution. Take 20 mL of the solution, add 0.5 g of the test sample, shake at 220 rpm at 25 ° C. After 24 hours, centrifuge and filter with a 0.45 μm filter. Measure the sodium ion removal rate and pH in the liquid. The removal rate is calculated according to the following formula:

[0078] Removal rate (%) = (C0-C e ) / C0×100%

[0079] Where C0 represents the initial concentration before the test (mg / L), C e Indicates the post-test concentration (mg / L).

[0080] Figure 2 The results of salinization improvement of Examples 1-4 and Comparative Examples 1-3 are shown in the figure; as shown in the figure, the sodium ion removal rate and pH of Examples 1-4 are 59-70% and 6.3-7.0, respectively, indicating that the salinization improvement effect is good; the sodium ion removal rate and pH of Comparative Examples 1-3 are 42-50% and 7.6-8.5, respectively, indicating that the salinization improvement effect is general; the soil conditioner for improving the fertility of saline-alkali land in Comparative Example 1 does not contain a composite filler based on nitrogen-doped modified wood soil peat and zeolite, and the filler cannot exert its adsorption of sodium ions, nor can it release hydrogen ions through adsorbed cation exchange, and cannot reduce the pH of the soil, resulting in a general salinization improvement effect; the composite filler based on nitrogen-doped modified wood soil peat and zeolite in Comparative Example 2 The comparative example 3 does not contain zeolite, and thus cannot further modify the nitrogen-doped acid-modified wood soil peat, cannot increase the adsorption sites and improve the adsorption capacity, thereby reducing the adsorption and removal effect of sodium ions, and cannot introduce Si-OH and Al-OH groups of zeolite, thereby reducing the release capacity of hydrogen ions, which is not conducive to lowering the pH value, resulting in a general improvement effect on salinization; the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbent resin of comparative example 3 does not contain sodium alginate, which is not conducive to forming a mutually penetrating and interlaced polymer network structure, thereby not conducive to improving the adsorption of salt, and is not conducive to the stability of the physical cross-linking of the composite filler based on nitrogen-doped modified wood soil peat and zeolite, thereby limiting the adsorption and hydrogen ion release effects, resulting in a general improvement effect on salinization.

[0081] Experimental Example 2

[0082] Water holding capacity test

[0083] Test sample: Soil conditioner for improving fertility of saline-alkali land prepared in Examples 1-4 and Comparative Examples 1-3.

[0084] Test method: Weigh 100g of saline-alkali soil (total salt content 2.0g / kg, pH value 8.7, moisture content 7.8%), add 0.5g of test sample and mix evenly, put the prepared soil into a plastic beaker with small holes at the bottom, cover the bottom with non-absorbent filter paper, place it in a basin of water, let the soil fully absorb water, after 12 hours, take out the beaker and drain the excess water, record the weight after the test, and calculate the net water absorbed by the soil according to the following formula, which is expressed as the maximum water holding capacity (%):

[0085] Maximum water holding capacity (%) = (M 测试后 -M 烧杯 -M 滤纸 ) / 100.5×100%

[0086] Figure 3 The maximum water holding capacity result diagram of Examples 1-4 and Comparative Examples 1-3; as shown in the figure, the maximum water holding capacity of Examples 1-4 is 63.5-72.3%, indicating that the water holding performance is strong; the maximum water holding capacity of Comparative Examples 1-3 is 47.3-55.6%, indicating that the water holding performance is weak; the soil conditioner for improving the fertility of saline-alkali land in Comparative Example 1 does not contain a composite filler based on nitrogen-doped modified wood soil peat and zeolite, and cannot produce a porous effect with the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin, which is not conducive to improving the adsorption and storage of water, resulting in The water-holding performance is weak; the composite filler based on nitrogen-doped modified wood soil peat and zeolite in Comparative Example 2 does not contain zeolite, and the surface roughness cannot be increased by compounding with modified wood soil peat, which is not conducive to the adsorption and storage of water, resulting in weak water-holding performance; the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbent resin in Comparative Example 3 does not contain sodium alginate, which is not conducive to the formation of a mutually penetrating and interlaced polymer network, and cannot play the role of sodium alginate gelling agent to form a stable moisture protection layer in the soil, which increases the evaporation and loss of water, resulting in weak water-holding performance.

[0087] Experimental Example 3

[0088] Fertility experiment

[0089] Test sample: Soil conditioner for improving fertility of saline-alkali land prepared in Examples 1-4 and Comparative Examples 1-3.

[0090] Test method: simulated experimental saline-alkali soil, where the soil in the experimental area is sandy loam, with an organic matter content of 4.3g / kg, a total salt content of 2.0g / kg, and a pH value of 8.7. The saline-alkali land was divided into 7 areas of equal size, each area of ​​0.05 mu; the saline-alkali land was plowed about 18cm, and the test samples were spread at a rate of 120kg per mu, and cultured under the same conditions for 30 days. After the culture period, the improved soil was taken for determination of organic matter content (g / kg). Soil organic matter was determined by potassium dichromate oxidation-external heating method.

[0091] Figure 4 The organic matter content result diagram of Examples 1-4 and Comparative Examples 1-3 is shown in the figure; as shown in the figure, the organic matter content of Examples 1-4 is 25.3-28.9 g / kg, all >25 g / kg, indicating that the effect of improving fertility is better; the organic matter content of Comparative Examples 1-3 is 13.7-18.5 g / kg, all <19 g / kg, indicating that the effect of improving fertility is not good; the soil conditioner for improving saline-alkali land fertility in Comparative Example 1 does not contain a composite filler based on nitrogen-doped modified wood soil peat and zeolite, and cannot supplement the organic matter rich in wood soil peat, Results in poor effect of improving fertility; the composite filler based on nitrogen-doped modified wood soil peat and zeolite in Comparative Example 2 does not contain zeolite, which is not conducive to improving the roughness of the modified wood soil peat structure, is not conducive to improving the adsorption capacity, thereby increasing the loss of nutrients, resulting in poor effect of improving fertility; the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbent resin in Comparative Example 3 does not contain sodium alginate, which is not conducive to forming a mutually penetrating and interlaced polymer network, has an adverse effect on the sustained release performance, and cannot effectively release the filler to improve soil fertility, resulting in poor effect of improving fertility.

[0092] The above experimental results show that the effects of improving salinization, water holding capacity and fertility of Examples 1-4 of the present invention are significantly better than those of Comparative Examples 1-3. Among them, Example 1 using a composite filler based on nitrogen-doped modified wood soil peat and zeolite and a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbent resin has better salinization improvement, stronger water holding capacity and better fertility improvement. The composite filler based on nitrogen-doped modified wood soil peat and zeolite is physically cross-linked with the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbent resin to form a loose and porous resin matrix structure, which effectively improves the adsorption capacity and water holding capacity of the composite resin, reduces the sodium ion concentration and pH value in the soil, reduces the adverse effects of high salt and high alkali problems on fertility, and can also slowly release the composite filler rich in organic matter, significantly improving the fertility of the soil.

[0093] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that many changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the invention.

[0094] The present invention and its implementation methods are described above, which is not restrictive. The drawings are only one of the implementation methods of the present invention, and the actual application is not limited thereto. In short, if ordinary technicians in the field are inspired by it and design methods and embodiments similar to the technical solution without creativity without departing from the purpose of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A soil conditioner for improving the fertility of saline-alkali land, characterized in that: The soil conditioner for improving the fertility of saline-alkali land comprises the following components in parts by weight: 50-60 parts of a composite filler based on nitrogen-doped modified wood soil peat and zeolite, and 20-30 parts of a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin; the composite filler based on nitrogen-doped modified wood soil peat and zeolite comprises the following components in parts by weight: 60-80 parts of an external nitrogen source, 20-40 parts of wood soil peat, and 20-40 parts of zeolite.

2. A method for preparing a soil conditioner for improving saline-alkali land fertility according to claim 1, characterized in that: The specific steps include: S1. Add 100 mL of deionized water into a beaker, preheat it in a water bath at 65-75°C, slowly add 1.0-2.0 g of polyvinyl alcohol under magnetic stirring, and after complete addition, raise the temperature to 90°C until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol solution; S2, add 2.5g potassium hydroxide to 10mL deionized water, stir magnetically until reaching room temperature, add 4mL acrylic acid liquid, continue stirring to cool to room temperature, then add 1.0g acrylamide, stir until completely dissolved, and use as solution I, measure 4-8mL of the polyvinyl alcohol solution described in step S1, add sodium alginate thereto, continue magnetic stirring, heat to 40-50°C, then dissolve 80mg ammonium persulfate in 4mL deionized water, and then add it to the reactant, then raise the temperature of the reaction mixture to 65°C, add solution I, continue to maintain at 65°C while stirring for 30-50min, to obtain a polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin; S3. Add the composite filler based on nitrogen-doped modified wood soil peat and zeolite and N,N'-methylenebisacrylamide to the polyvinyl alcohol semi-interpenetrating sodium alginate composite water-absorbing resin described in step S2, maintain the reaction temperature at 55-65°C, stir and react for 2-3 hours, collect the product, wash it repeatedly with 95% ethanol solution for 3-5 times, vacuum dry it, and then crush it with a sieve aperture of 60-80 mesh to obtain a soil conditioner for improving the fertility of saline-alkali land.

3. The method for preparing a soil conditioner for improving the fertility of saline-alkali land according to claim 2, characterized in that: In step S2, the amount of sodium alginate added is 0.4-0.6 g.

4. The method for preparing a soil conditioner for improving the fertility of saline-alkali land according to claim 3, characterized in that: In step S3, the amount of N,N'-methylenebisacrylamide added is 10-20 mg.

5. The method for preparing a soil conditioner for improving the fertility of saline-alkali land according to claim 4, characterized in that: The preparation method of the composite filler based on nitrogen-doped modified wood soil peat and zeolite specifically comprises the following steps: (1) 60.0-80.0 g of an external nitrogen source and 2.0-4.0 g of wood soil peat are mixed, crushed, and added to a beaker containing 80-100 mL of a 4% hydrochloric acid solution, stirred at room temperature for 0.5-1 h, sealed with plastic wrap, and subjected to ultrasonic treatment for 1-2 h to allow the substances in the beaker to fully contact and mix, and then placed on a heated magnetic stirrer for high-speed stirring and heated in a water bath to 60-80° C. until the water in the mixture is basically evaporated, and the mixed solid is taken out for vacuum drying and grinding to obtain nitrogen-doped acid-modified wood soil peat; (2) Add the nitrogen-doped acid-modified wood soil peat described in step (1) into a beaker containing 80-100 mL of 4% hydrochloric acid solution, stir at room temperature for 0.5-1 h, then add 2.0-4.0 g of zeolite powder, seal the beaker with plastic wrap, stir for 20-30 min, then perform ultrasonic treatment for 1-2 h, centrifuge, wash the precipitate with ultrapure water 3-5 times, collect the filter cake, vacuum dry, and grind to obtain a composite filler based on nitrogen-doped modified wood soil peat and zeolite.

6. The method for preparing a soil conditioner for improving the fertility of saline-alkali land according to claim 5, characterized in that: In step (1), the external nitrogen source is any one of dicyandiamide and urea or a mixture thereof.

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