A kind of for improving saline-alkali soil and preparation method thereof

Abstract

The application discloses a kind of for improving saline-alkali soil's Potamogeton crispus soil conditioner and preparation method thereof, it is related to soil improvement technical field, belongs to patent classification C05G3 / 00.The method is alkalized after Potamogeton crispus powder, with acrylic acid, 2-acrylamide-2-methylpropane sulfonic acid graft copolymerization and load calcium ion, obtain salt-alkali modified Potamogeton crispus;After attapulgite is acidified by citric acid, with salt-alkali modified Potamogeton crispus and citric acid powder mixed heat treatment;Again with ammonium bicarbonate granulation, heating foaming construction multistage pore, finally by impregnation sodium silicate and calcium chloride are carried out pore wall strengthening, and prepared conditioner.The soil conditioner prepared by the application has the characteristics of ion exchange salt-alkali reduction, multistage pore air permeability improvement and long-term stable structure, etc., can comprehensively reduce soil salinity and significantly improve air permeability.

Description

Technical Field

[0001] This invention relates to the field of soil improvement technology, belonging to patent classification number C05G3 / 00, specifically to a *Potamogeton crispus* soil conditioner for improving saline-alkali land and its preparation method. Background Technology

[0002] Soil salinization is one of the major environmental problems restricting sustainable agricultural development worldwide. High concentrations of soluble salts and excessive exchangeable sodium ions in saline-alkali soils lead to soil compaction, poor aeration, low available nutrient content, and excessively high osmotic pressure, severely inhibiting crop root development and nutrient absorption, resulting in reduced yields or even crop failure. Currently, saline-alkali soil improvement technologies mainly fall into three categories: physical, chemical, and biological improvement. In chemical improvement, the application of chemical conditioners such as gypsum, ferrous sulfate, and humic acid can rapidly reduce soil sodium ion concentration and pH, but these methods suffer from low efficiency or secondary pollution. In recent years, the preparation of soil conditioners using agricultural waste or aquatic plant resources has attracted attention, but existing technologies generally suffer from insufficient salt-reducing capacity or neglect of improving soil permeability. *Potamogeton crispus*, a submerged plant widely distributed in the Xishui River in my country, has extremely high reproductive capacity and is often considered a harmful species due to its excessive reproduction leading to eutrophication. Large quantities of *Potamogeton crispus* are typically harvested and disposed of as waste, resulting in significant resource waste. Potamogeton crispus is rich in natural polymers such as cellulose, hemicellulose, and pectin, and has great potential as a raw material for soil conditioners. However, there are currently no reports on technologies that can effectively convert Potamogeton crispus into soil conditioners specifically for saline-alkali land. Furthermore, the core of saline-alkali land improvement lies in reducing soil salinity and improving soil physical structure. However, in the development of soil conditioners, there is often a contradiction between improving salinity reduction and improving soil aeration: polymer modifications used to enhance ion exchange and salt adsorption often produce a swelling effect upon contact with water, which can clog aeration channels and reduce soil aeration. Summary of the Invention

[0003] The purpose of this invention is to provide a *Potamogeton crispus* soil conditioner for improving saline-alkali land and its preparation method, so as to solve the technical problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land includes the following steps:

[0006] (1) The collected pickled grass is washed, dried and crushed to obtain pickled grass powder;

[0007] (2) Add the powder of *Potamogeton crispus* to a sodium hydroxide solution for treatment, filter, wash and dry to obtain alkalized *Potamogeton crispus*;

[0008] (3) Add alkalized zedock to deionized water, and add acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, ammonium persulfate and N,N'-methylenebisacrylamide under protective gas to react, filter and wash to obtain graft copolymer;

[0009] (4) The graft copolymer was immersed in calcium chloride solution for treatment, filtered, washed and dried to obtain salt-alkali modified pickled mustard greens;

[0010] (5) Add attapulgite to citric acid solution for treatment, filter and dry to obtain acidified attapulgite;

[0011] (6) Mix salt-alkali modified pickled mustard greens, acidified attapulgite and citric acid powder, moisten with water and heat-treat, then cool to obtain modified pickled mustard greens;

[0012] (7) The modified zedoaria was mixed with ammonium bicarbonate, and sodium alginate solution was added for granulation. After drying and heating foaming treatment, porous particles were obtained.

[0013] (8) The porous particles are sequentially immersed in sodium silicate solution and calcium chloride solution for pore wall strengthening treatment. Finally, they are washed, dried and granulated to obtain the podophyllum soil conditioner.

[0014] In the technical solution of this invention, the principle of reducing the salinity of saline-alkali soil is as follows: through three treatment steps—alkalization activation, graft copolymerization, and calcium ion loading—a three-dimensional cross-linked polymer network rich in carboxyl and sulfonic acid groups is constructed on the surface of *Potamogeton crispus* fibers, and a large amount of Ca is preloaded onto this network. 2+ When this conditioner is applied to saline-alkali soil, its salinity-reducing mechanism includes three levels: (1) Ca loaded on the polymer network 2+ With excess Na in the soil + An ion exchange occurs, transferring Na + It is adsorbed and fixed into the conditioner from the soil solution, while releasing Ca, which is beneficial to soil structure. 2+ (1) Reduce the content of soluble sodium in the soil; (2) Release Ca 2+ Further replacement of exchangeable Na on soil colloids + This promotes the flocculation of soil particles to form aggregate structure and improves the hydrophysical properties of the soil; (3) The sulfonic acid groups in the polymer network remain fully ionized under a wide range of pH conditions, which can effectively neutralize alkaline substances in the soil and reduce the soil pH value. The above three synergistic effects comprehensively reduce the salinity of saline-alkali soil from three dimensions: reducing soluble sodium content, improving soil structure and neutralizing alkalinity.

[0015] In the technical solution of this invention, the principle of improving the aeration performance of saline-alkali soil is as follows: through two treatment steps of pore-forming foaming and pore wall reinforcement, a multi-level pore structure with interconnected channels is constructed inside the conditioner particles. When the conditioner is applied to saline-alkali soil, its mechanism of improving soil aeration includes three levels: (1) The macropores inside the conditioner particles serve as the main channels for gas transmission. When a large number of particles are dispersed in the soil, they form a micro-aeration network throughout the cultivated layer, which significantly increases the soil aeration porosity and promotes root respiration and aerobic activity of soil microorganisms; (2) The mesopores provide channels for the transmission of water and solutes, accelerating the process of surface salts migrating to deeper layers with irrigation water and speeding up the desalination rate; (3) The hydrated calcium silicate gel coating on the surface of the pore wall significantly enhances the mechanical strength and water resistance of the pore wall, so that the multi-level pore structure can maintain structural integrity and unobstructedness in the soil moisture environment for a long time, ensuring that the conditioner continues to play a role in promoting aeration throughout the entire crop growing season. The above-mentioned triple synergistic effect comprehensively improves the air permeability of saline-alkali soil from three dimensions: increasing aeration porosity, promoting salt leaching, and ensuring structural stability.

[0016] Preferably, in step (2), the mass concentration of the sodium hydroxide solution is 8-12%.

[0017] Preferably, in step (3), the mass ratio of alkalized zedoaria to acrylic acid is 10:(5-8).

[0018] Preferably, in step (3), the mass ratio of alkalized Potamogeton crispus to 2-acrylamido-2-methylpropanesulfonic acid is 10:(2-4).

[0019] Preferably, in step (4), the concentration of the calcium chloride solution is 0.5 to 1.0 mol / L.

[0020] Preferably, in step (5), the mass concentration of the citric acid solution is 6-10%.

[0021] Preferably, in step (6), the mass ratio of acidified attapulgite to citric acid powder is 5:(1-3).

[0022] This invention discovered in experiments that the three-dimensional polymer network modified on the surface of *Potamogeton crispus* fibers exhibits strong water absorption and swelling properties. When soil conditioners are applied to saline-alkali land and come into contact with water, the polymer network swells rapidly, causing the interconnected hierarchical pore structure built within the subsequent conditioner particles to be squeezed and blocked by the expanding gel, severely weakening the conditioner's aeration-promoting effect on the soil. To solve this technical problem, this invention introduces attapulgite and citric acid, utilizing their synergistic effect to regulate the swelling behavior of the polymer network. Attapulgite is a natural fibrous clay mineral; its rod-shaped nanocrystals possess high rigidity and a high aspect ratio. When dispersed in the polymer network, it forms a rigid framework support system, physically restricting the free movement and swelling space of polymer chain segments. Citric acid, as a small-molecule crosslinking agent containing three carboxyl groups, establishes multiple interactive connections between the attapulgite surface and the polymer network, firmly binding the rigid framework of attapulgite and the organic polymer network together to form a constrained network structure with rigid-flexible coupling characteristics. After the aforementioned synergistic regulation, the swelling rate of the polymer network was significantly reduced, maintaining sufficient ion exchange and salt adsorption capacity while avoiding excessive swelling that could damage the subsequent pore structure. If attapulgite is used alone without citric acid, the swelling rate decreases only slightly, still damaging the pore structure; if citric acid is used alone without attapulgite, although the swelling rate can be reduced to a lower level, the ion exchange efficiency is significantly reduced, severely weakening the salt-alkali reduction function. Only the synergistic use of attapulgite and citric acid can achieve a coordinated balance between the salt-alkali reduction function and the air permeability promotion function.

[0023] Preferably, in step (7), the mass ratio of modified zedpa to ammonium bicarbonate is 10:(1-4).

[0024] Preferably, in step (7), the mass concentration of sodium alginate solution is 1-3%.

[0025] A *Potamogeton crispus* soil conditioner for improving saline-alkali land is prepared by the method described above.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. Through the triple synergistic effect of the exchange between Ca2+ loaded in the polymer network and Na+ in the soil, the release of Ca2+ to replace colloidal sodium ions, and the neutralization of alkaline substances by sulfonic acid groups, salinity and alkalinity are reduced in three aspects: reducing soluble sodium content, improving soil structure, and neutralizing alkalinity.

[0028] 2. A multi-level pore structure is constructed inside the conditioner to form a micro-ventilation network to increase porosity. The mesopores are used to accelerate salt leaching, and the pore wall reinforcement coating ensures the long-term stability of the pore structure, thereby achieving a continuous air permeability promotion function.

[0029] 3. By introducing an attapulgite rigid framework and a citric acid crosslinking agent for synergistic regulation, a rigid-flexible coupled constraint network is formed, which significantly reduces the excessive swelling of the polymer when exposed to water. While maintaining ion exchange capacity, it avoids pore blockage and ensures long-term stable performance in desalination and air permeability. Attached Figure Description

[0030] Figure 1 This is a low-magnification SEM image of the soil conditioner prepared in Example 1 of the present invention.

[0031] Figure 2 This is a medium-magnification SEM image of the soil conditioner prepared in Example 1 of the present invention.

[0032] Figure 3 This is a high-magnification SEM image of the soil conditioner prepared in Example 1 of the present invention.

[0033] Figure 4 The image shows the XRD pattern of the soil conditioner prepared in Example 1 of this invention. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] A method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land includes the following steps:

[0037] (1) Collect 500g of fresh pickled grass, wash it 4 times with deionized water, dry it in an 80℃ oven until constant weight, pulverize it and pass it through a 60-mesh sieve to obtain pickled grass powder.

[0038] (2) Add 100g of Potamogeton crispus powder to 1500g of sodium hydroxide solution with a mass concentration of 11%, stir at 85℃ for 2.5h, filter after the reaction is complete, wash with deionized water until the pH of the filtrate is 7.0±0.5, dry at 60℃ to constant weight to obtain alkalized Potamogeton crispus.

[0039] (3) Add 65g of alkalized zedock to 1300mL of deionized water, purge with nitrogen for 30min, then add 45g of acrylic acid (pre-neutralized with 14g of sodium hydroxide) and 22g of 2-acrylamido-2-methylpropanesulfonic acid, then add 0.585g of ammonium persulfate and 0.176g of N,N'-methylenebisacrylamide, and stir continuously at 65℃ for 5h. After the reaction is completed, filter and wash three times with anhydrous ethanol to obtain the graft copolymer.

[0040] (4) Immerse the graft copolymer in 600 mL of 0.9 mol / L calcium chloride solution, stir at room temperature for 5 h, filter, and wash with deionized water until no Cl is present. - The sample was dried at 60℃ to constant weight to obtain salt-alkali-reduced modified pickled mustard greens.

[0041] (5) Add 50g of attapulgite to 500g of anhydrous citric acid solution with a mass concentration of 9%, stir at 60℃ for 2h, filter, and dry at 60℃ to constant weight to obtain acidified attapulgite.

[0042] (6) Mix 55g of salt-alkali modified pickled clover with 10g of acidified attapulgite, add 5g of anhydrous citric acid powder, mix evenly, add deionized water to wet until the moisture content of the material is about 35%, heat-treat at 130℃ for 2.5h, and cool naturally to room temperature to obtain modified pickled clover.

[0043] (7) Mix the modified pickled sage and ammonium bicarbonate at a mass ratio of 10:3, add a 2.5% sodium alginate aqueous solution (the amount added is 60% of the mass of the modified pickled sage), knead thoroughly, and then extrude and granulate into wet particles with a particle size of 3 mm. First, pre-dry at 60℃ for 1 h, then heat to 140℃ and keep warm for 2 h. After cooling, porous particles are obtained.

[0044] (8) Soak the porous particles in a 5% sodium silicate solution at room temperature for 0.5 h, drain them and immediately soak them in a 3% calcium chloride solution at room temperature for 30 min, wash them three times with deionized water, dry them at 60°C to constant weight, and granulate them to a particle size of 1-3 mm to obtain the podophyllum soil conditioner.

[0045] Example 2

[0046] A method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land includes the following steps:

[0047] (1) Collect 500g of fresh pickled grass, wash it 4 times with deionized water, dry it in an 80℃ oven until constant weight, pulverize it and pass it through a 60-mesh sieve to obtain pickled grass powder.

[0048] (2) Add 100g of Potamogeton crispus powder to 1500g of sodium hydroxide solution with a mass concentration of 9%, stir at 85℃ for 2.5h, filter after the reaction is complete, wash with deionized water until the pH of the filtrate is 7.0±0.5, dry at 60℃ to constant weight to obtain alkalized Potamogeton crispus.

[0049] (3) Add 65g of alkalized zedock to 1300mL of deionized water, purge with nitrogen for 30min to remove oxygen, then add 35g of acrylic acid (pre-neutralized with 14g of sodium hydroxide) and 15g of 2-acrylamido-2-methylpropanesulfonic acid, then add 0.585g of ammonium persulfate and 0.176g of N,N'-methylenebisacrylamide, and stir continuously at 65℃ for 5h. After the reaction is completed, filter and wash three times with anhydrous ethanol to obtain the graft copolymer.

[0050] (4) Immerse the graft copolymer in 600 mL of 0.6 mol / L calcium chloride solution, stir at room temperature for 5 h, filter, and wash with deionized water until no Cl is present. - The sample was dried at 60℃ to constant weight to obtain salt-alkali-reduced modified pickled mustard greens.

[0051] (5) Add 50g of attapulgite to 500g of anhydrous citric acid solution with a mass concentration of 7%, stir at 60℃ for 2h, filter, and dry at 60℃ to constant weight to obtain acidified attapulgite.

[0052] (6) Mix 55g of salt-alkali modified pickled clover with 10g of acidified attapulgite, add 3g of anhydrous citric acid powder, mix evenly, add deionized water to wet until the moisture content of the material is about 35%, heat-treat at 130℃ for 2.5h, and cool naturally to room temperature to obtain modified pickled clover.

[0053] (7) Mix the modified pickled sage and ammonium bicarbonate at a mass ratio of 10:2, add a 1.5% sodium alginate aqueous solution (the amount added is 60% of the mass of the modified pickled sage), knead thoroughly, and then extrude and granulate into wet particles with a particle size of 3 mm. First, pre-dry at 60℃ for 1 h, then heat to 140℃ and keep warm for 2 h, and then cool to obtain porous particles.

[0054] (8) Soak the porous particles in a 5% sodium silicate solution at room temperature for 0.5 h, drain them and immediately soak them in a 3% calcium chloride solution at room temperature for 30 min, wash them three times with deionized water, dry them at 60°C to constant weight, and granulate them to a particle size of 1-3 mm to obtain the podophyllum soil conditioner.

[0055] Example 3

[0056] A method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land includes the following steps:

[0057] (1) Collect 500g of fresh pickled grass, wash it 4 times with deionized water, dry it in an 80℃ oven until constant weight, pulverize it and pass it through a 60-mesh sieve to obtain pickled grass powder.

[0058] (2) Add 100g of Potamogeton crispus powder to 1500g of sodium hydroxide solution with a mass concentration of 10%, stir at 85℃ for 2.5h, filter after the reaction is complete, wash with deionized water until the pH of the filtrate is 7.0±0.5, dry at 60℃ to constant weight to obtain alkalized Potamogeton crispus.

[0059] (3) Add 65g of alkalized zedock to 1300mL of deionized water, purge with nitrogen for 30min to remove oxygen, then add 40g of acrylic acid (pre-neutralized with 14g of sodium hydroxide) and 20g of 2-acrylamido-2-methylpropanesulfonic acid, then add 0.585g of ammonium persulfate and 0.176g of N,N'-methylenebisacrylamide, and stir continuously at 65℃ for 5h. After the reaction is completed, filter and wash three times with anhydrous ethanol to obtain the graft copolymer.

[0060] (4) Immerse the graft copolymer in 600 mL of 0.7 mol / L calcium chloride solution, stir at room temperature for 5 h, filter, and wash with deionized water until no Cl is present. - The sample was dried at 60℃ to constant weight to obtain salt-alkali-reduced modified pickled mustard greens.

[0061] (5) Add 50g of attapulgite to 500g of anhydrous citric acid solution with a mass concentration of 8%, stir at 60℃ for 2h, filter, and dry at 60℃ to constant weight to obtain acidified attapulgite.

[0062] (6) Mix 55g of salt-alkali modified pickled clover with 10g of acidified attapulgite, add 4g of anhydrous citric acid powder, mix evenly, add deionized water to wet until the moisture content of the material is about 35%, heat-treat at 130℃ for 2.5h, and cool naturally to room temperature to obtain modified pickled clover.

[0063] (7) Mix the modified pickled sage and ammonium bicarbonate at a mass ratio of 10:2.5, add a 2% sodium alginate aqueous solution (the amount added is 60% of the mass of the modified pickled sage), knead thoroughly, and then extrude and granulate into wet particles with a particle size of 3 mm. First, pre-dry at 60℃ for 1 h, then heat to 140℃ and keep warm for 2 h. After cooling, porous particles are obtained.

[0064] (8) Soak the porous particles in a 5% sodium silicate solution at room temperature for 0.5 h, drain them and immediately soak them in a 3% calcium chloride solution at room temperature for 30 min, wash them three times with deionized water, dry them at 60°C to constant weight, and granulate them to a particle size of 1-3 mm to obtain the podophyllum soil conditioner.

[0065] Example 4

[0066] A method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land includes the following steps:

[0067] (1) Collect 500g of fresh pickled grass, wash it 4 times with deionized water, dry it in an 80℃ oven until constant weight, pulverize it and pass it through a 60-mesh sieve to obtain pickled grass powder.

[0068] (2) Add 100g of Potamogeton crispus powder to 1500g of sodium hydroxide solution with a mass concentration of 12%, stir at 85℃ for 2.5h, filter after the reaction is complete, wash with deionized water until the pH of the filtrate is 7.0±0.5, dry at 60℃ to constant weight to obtain alkalized Potamogeton crispus.

[0069] (3) Add 65g of alkalized zedock to 1300mL of deionized water, purge with nitrogen for 30min, then add 52g of acrylic acid (pre-neutralized with 14g of sodium hydroxide) and 26g of 2-acrylamido-2-methylpropanesulfonic acid, then add 0.585g of ammonium persulfate and 0.176g of N,N'-methylenebisacrylamide, and stir continuously at 65℃ for 5h. After the reaction is completed, filter and wash three times with anhydrous ethanol to obtain the graft copolymer.

[0070] (4) Immerse the graft copolymer in 600 mL of a 1.0 mol / L calcium chloride solution, stir at room temperature for 5 h, filter, and wash with deionized water until no Cl is present. - The sample was dried at 60℃ to constant weight to obtain salt-alkali-reduced modified pickled mustard greens.

[0071] (5) Add 50g of attapulgite to 500g of anhydrous citric acid solution with a mass concentration of 10%, stir at 60℃ for 2h, filter, and dry at 60℃ to constant weight to obtain acidified attapulgite.

[0072] (6) Mix 55g of salt-alkali modified pickled clover with 10g of acidified attapulgite, add 6g of anhydrous citric acid powder, mix evenly, add deionized water to wet until the moisture content of the material is about 35%, heat-treat at 130℃ for 2.5h, and cool naturally to room temperature to obtain modified pickled clover.

[0073] (7) Mix the modified pickled sage and ammonium bicarbonate at a mass ratio of 10:4, add a 3% sodium alginate aqueous solution (the amount added is 60% of the mass of the modified pickled sage), knead thoroughly, and then extrude and granulate into wet particles with a particle size of 3 mm. First, pre-dry at 60℃ for 1 h, then heat to 140℃ and keep warm for 2 h, and then cool to obtain porous particles.

[0074] (8) Soak the porous particles in a 5% sodium silicate solution at room temperature for 0.5 h, drain them and immediately soak them in a 3% calcium chloride solution at room temperature for 30 min, wash them three times with deionized water, dry them at 60°C to constant weight, and granulate them to a particle size of 1-3 mm to obtain the podophyllum soil conditioner.

[0075] Example 5

[0076] A method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land includes the following steps:

[0077] (1) Collect 500g of fresh pickled grass, wash it 4 times with deionized water, dry it in an 80℃ oven until constant weight, pulverize it and pass it through a 60-mesh sieve to obtain pickled grass powder.

[0078] (2) Add 100g of Potamogeton crispus powder to 1500g of sodium hydroxide solution with a mass concentration of 8%, stir at 85℃ for 2.5h, filter after the reaction is complete, wash with deionized water until the pH of the filtrate is 7.0±0.5, dry at 60℃ to constant weight to obtain alkalized Potamogeton crispus.

[0079] (3) Add 65g of alkalized zedock to 1300mL of deionized water, purge with nitrogen for 30min to remove oxygen, then add 32.5g of acrylic acid (pre-neutralized with 14g of sodium hydroxide) and 13g of 2-acrylamido-2-methylpropanesulfonic acid, then add 0.585g of ammonium persulfate and 0.176g of N,N'-methylenebisacrylamide, and stir continuously at 65℃ for 5h. After the reaction is completed, filter and wash three times with anhydrous ethanol to obtain the graft copolymer.

[0080] (4) Immerse the graft copolymer in 600 mL of 0.5 mol / L calcium chloride solution, stir at room temperature for 5 h, filter, and wash with deionized water until no Cl is visible. - The sample was dried at 60℃ to constant weight to obtain salt-alkali-reduced modified pickled mustard greens.

[0081] (5) Add 50g of attapulgite to 500g of anhydrous citric acid solution with a mass concentration of 6%, stir at 60℃ for 2h, filter, and dry at 60℃ to constant weight to obtain acidified attapulgite.

[0082] (6) Mix 55g of salt-alkali modified pickled clover with 10g of acidified attapulgite, add 2g of anhydrous citric acid powder, mix evenly, add deionized water to wet until the moisture content of the material is about 35%, heat-treat at 130℃ for 2.5h, and cool naturally to room temperature to obtain modified pickled clover.

[0083] (7) Mix the modified pickled sage and ammonium bicarbonate at a mass ratio of 10:1, add a 1% sodium alginate aqueous solution (the amount added is 60% of the mass of the modified pickled sage), knead thoroughly, and then extrude and granulate into wet particles with a particle size of 3 mm. First, pre-dry at 60℃ for 1 h, then heat to 140℃ and keep warm for 2 h, and then cool to obtain porous particles.

[0084] (8) Soak the porous particles in a 5% sodium silicate solution at room temperature for 0.5 h, drain them and immediately soak them in a 3% calcium chloride solution at room temperature for 30 min, wash them three times with deionized water, dry them at 60°C to constant weight, and granulate them to a particle size of 1-3 mm to obtain the podophyllum soil conditioner.

[0085] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that steps (2) to (4) are not performed, that is, the alkalization activation, graft copolymerization modification and calcium ion loading treatment are not performed, and the original Potamogeton powder is directly used for the treatment in steps (5) to (8).

[0086] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that steps (7) to (8) are not performed, that is, the pore-forming foaming and pore wall strengthening treatment are not performed. The modified pickled mustard obtained in step (6) is directly dried and granulated to 1-3 mm as the finished product.

[0087] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that steps (5) to (6) are not performed, that is, attapulgite and citric acid are not added, and the salt-alkali modified pickled mustard greens obtained in step (4) are directly used for the treatment in steps (7) to (8).

[0088] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that only acidified attapulgite is added in step (6), and citric acid powder is not added, while the other conditions remain unchanged.

[0089] Comparative Example 5: The difference between Comparative Example 5 and Example 1 is that only citric acid powder is added in step (6), and acidified attapulgite is not added, while the other conditions remain unchanged.

[0090] Performance testing:

[0091] 1. Swelling Rate Test: Take 2.000 g (accurate to 0.001 g) of each of the soil conditioner samples prepared in Examples 1-5 and Comparative Examples 1-5, place them in a 200-mesh nylon mesh bag and seal it. Completely immerse the mesh bag in a beaker containing 500 mL of deionized water and allow it to soak at room temperature (25±2℃) for 24 h until swelling equilibrium is reached. Remove the mesh bag, suspend it for 15 min to drain excess water, and weigh and record the mass after swelling. The swelling rate is calculated using the formula: Swelling rate (g / g) = (mass after swelling - dry weight) / dry weight. Each sample is measured in triplicate, and the average value is taken. The test results are shown in Table 1.

[0092] 2. Ion exchange efficiency test: Prepare a 0.1 mol / L NaCl solution to simulate saline-alkali soil. Add 2.000 g of each sample to 200 mL of the NaCl solution and place on a 25℃ constant temperature shaker at 150 rpm for 8 hours to allow sufficient ion exchange. After shaking, filter the solution and determine the Ca content in the filtrate using Roche flame atomic absorption spectrometry. 2+ The concentration of Na in the filtrate was determined by Roche flame atomic absorption spectrometry. + Concentration. Ion exchange efficiency is measured by the Na+ concentration in the filtrate. + Calculation of concentration reduction rate: Ion exchange efficiency (%) = (initial Na) / (Na) + Concentration - Na after equilibrium + (concentration) / initial Na + Concentration × 100%. Each sample was measured in triplicate, and the average value was taken. The test results are shown in Table 1.

[0093] 3. Internal Porosity Test: The internal porosity of each sample was determined using the mercury infiltration method. Approximately 1 g of each sample was dried to constant weight at 105℃ and placed in an automated mercury infiltration apparatus. The test pressure range was set to 0.5–60000 psia, and the contact angle was set to 130°. The total porosity, average pore size, and pore size distribution of the samples were measured. The total porosity was expressed as the percentage of the total volume of mercury infiltrated per unit mass of sample relative to the apparent volume of the sample. Each sample was measured twice, and the average value was taken. The test results are shown in Table 1.

[0094] Table 1:

[0095]

[0096] Note: Comparative Example 2 did not undergo pore-forming foaming treatment and has no porous structure, so the particle porosity is represented by " / ".

[0097] Table 1 shows that the swelling ratios of Examples 1-5 ranged from 9.5 to 14.8 g / g, the ion exchange efficiencies ranged from 86.3% to 93.2%, and the particle porosity ranged from 62.4% to 71.5%, all three indicators showing excellent performance. Example 4 had the lowest swelling ratio at 9.5 g / g and the highest ion exchange efficiency at 93.2%; Example 5 had the highest swelling ratio at 14.8 g / g and the lowest ion exchange efficiency at 86.3%, but both were still within acceptable ranges. Comparative Example 1 (without salt reduction) had an ion exchange efficiency of only 12.6%, indicating that the original *Potamogeton crispus* powder without graft copolymerization and calcium ion loading had almost no ion exchange capacity. Comparative Example 3 (without swelling control) had a high swelling ratio of 76.3 g / g, and although the ion exchange efficiency was relatively high (93.5%), such drastic swelling would lead to severe blockage of the pore structure in practical applications. The swelling rate of Comparative Example 4 (attapulgite only) was 36.8 g / g, only about half that of Comparative Example 3, indicating that physical constraints alone are insufficient to effectively limit swelling. The swelling rate of Comparative Example 5 (citric acid only) decreased to 5.8 g / g, but the ion exchange efficiency plummeted to 54.7%, indicating that excessive chemical cross-linking severely weakened the ion exchange function. These results fully demonstrate that attapulgite and citric acid must be used synergistically to effectively control swelling while maintaining sufficient ion exchange activity.

[0098] 4. Field Application Trial: The trial site was located in a saline-alkali land experimental field in Shandong Province. The average soil pH was 9.2, the surface soil salinity was 5.83 g / kg, and the soil bulk density was 1.38 g / cm³. 3 The soil had an aeration porosity of 4.1% and an organic matter content of 8.6 g / kg. The crop planted was maize. Eleven treatments were established: Examples 1-5, Comparative Examples 1-5, and a blank control group. Each treatment group covered an area of ​​1 mu (approximately 0.067 hectares), with 1-m wide protective rows between treatment groups. Examples and comparative examples received 40 kg / mu of their respective prepared soil conditioners, while the blank control group received no conditioner. All other management practices were the same. At harvest, plant height (50 plants randomly selected and averaged), maize 100-kernel weight, and yield per mu were recorded. The test results are shown in Table 2.

[0099] Table 2:

[0100]

[0101] 5. Soil physicochemical property testing: Soil samples were taken from the surface depth of 0–20 cm in each treatment group after harvest. Soil pH was measured using a pH meter, with a soil-to-water ratio of 2.5:1 (volume-to-mass ratio). The pure water used was boiled beforehand to remove carbon dioxide. Soil salinity was determined using a gravimetric method, which involved evaporating the soil extract to dryness and weighing it to calculate the total soluble salt content per kilogram of soil. Soil bulk density was measured using the ring sampler method. Aeration porosity was calculated based on the difference between total soil porosity and capillary porosity, where total porosity was obtained from bulk density and soil saturated water content, and capillary porosity was obtained from field capacity. Soil organic matter was determined using the potassium dichromate oxidation-external heating method. The test results are shown in Table 3.

[0102] Table 3:

[0103]

[0104] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land, characterized in that, Includes the following steps: (1) The collected pickled grass is washed, dried and crushed to obtain pickled grass powder; (2) Add the powder of *Potamogeton crispus* to a sodium hydroxide solution for treatment, filter, wash and dry to obtain alkalized *Potamogeton crispus*; (3) Add alkalized zedock to deionized water, and add acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, ammonium persulfate and N,N'-methylenebisacrylamide under protective gas to react, filter and wash to obtain graft copolymer; (4) The graft copolymer was immersed in calcium chloride solution for treatment, filtered, washed and dried to obtain salt-alkali modified pickled mustard greens; (5) Add attapulgite to citric acid solution for treatment, filter and dry to obtain acidified attapulgite; (6) Mix salt-alkali modified pickled mustard greens, acidified attapulgite and citric acid powder, moisten with water and heat-treat, then cool to obtain modified pickled mustard greens; (7) The modified zedoaria was mixed with ammonium bicarbonate, and sodium alginate solution was added for granulation. After drying and heating foaming treatment, porous particles were obtained. (8) The porous particles are sequentially immersed in sodium silicate solution and calcium chloride solution for pore wall strengthening treatment. Finally, they are washed, dried and granulated to obtain the podophyllum soil conditioner.

2. The method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land according to claim 1, characterized in that, In step (2), the mass concentration of the sodium hydroxide solution is 8-12%.

3. The method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land according to claim 1, characterized in that, In step (3), the mass ratio of alkalized zedoaria to acrylic acid is 10:(5-8).

4. The method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land according to claim 1, characterized in that, In step (3), the mass ratio of alkalized Potamogeton crispus to 2-acrylamido-2-methylpropanesulfonic acid is 10:(2-4).

5. The method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land according to claim 1, characterized in that, In step (4), the concentration of the calcium chloride solution is 0.5–1.0 mol / L.

6. The method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land according to claim 1, characterized in that, In step (5), the mass concentration of the citric acid solution is 6-10%.

7. The method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land according to claim 1, characterized in that, In step (6), the mass ratio of acidified attapulgite to citric acid powder is 5:(1-3).

8. A method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land according to claim 1, characterized in that, In step (7), the mass ratio of modified zephyranthes to ammonium bicarbonate is 10:(1-4).

9. A method for preparing a *Potamogeton crispus* soil conditioner for improving saline-alkali land according to claim 1, characterized in that, In step (7), the mass concentration of sodium alginate solution is 1-3%.

10. A *Potamogeton crispus* soil conditioner for improving saline-alkali land, characterized in that, It is prepared by the method described in any one of claims 1 to 9 above.

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