A composition for saline-alkali soil improvement and a preparation method thereof

Abstract

The application belongs to the technical field of agricultural soil improvement, and particularly relates to a composition for saline-alkali soil improvement and a preparation method thereof. The composition for saline-alkali soil improvement comprises the following raw materials in parts by weight: 30-45 parts of straw powder, 1-3 parts of microbial inoculum, 5-8 parts of film forming agent, 12-15 parts of humic acid, 5-10 parts of biochar gel microspheres and 15-20 parts of desulfurized gypsum. The composition for saline-alkali soil improvement provided by the application improves the soil dispersion degree, relieves soil compaction and effectively reduces the soil salt content through the synergistic improvement of straw powder, microbial inoculum, film forming agent, humic acid, biochar gel microspheres and desulfurized gypsum, thereby providing a new idea for the comprehensive management of saline-alkali soil.

Description

Technical Field

[0001] This invention belongs to the field of agricultural soil improvement technology, specifically relating to a composition for improving saline-alkali land and its preparation method. Background Technology

[0002] my country has a wide distribution of saline-alkali land, covering a large area, and this area is expanding year by year. Saline-alkali soils contain excessive amounts of soluble sodium, chloride, and other harmful salts, resulting in high soil pH, dispersed soil structure, easy compaction, low porosity, and poor water permeability and fertilizer retention capacity; these factors severely restrict crop growth and the utilization of land resources.

[0003] Various technical approaches have been developed for the improvement of saline-alkali land. Physical improvement measures, such as topsoil application and deep tillage, have some effect, but they involve large-scale engineering, are costly, and only address the symptoms, not the root cause. Chemical improvement measures mainly involve applying calcium-containing substances such as desulfurized gypsum and superphosphate, using calcium ions to replace exchangeable sodium ions on soil colloids, thereby reducing soil alkalinity. Among these, desulfurized gypsum is widely used due to its low cost and significant effects. However, the application of desulfurized gypsum alone has drawbacks: rapid release and leaching of calcium ions, incomplete sodium ion exchange, and limited effects on improving soil structure and water retention capacity.

[0004] Biological soil amendment measures, such as the application of microbial agents and organic materials like straw and humic acid, aim to improve the soil micro-ecological environment, increase soil organic matter, and promote soil aggregate formation through microbial activity and the action of organic colloids. However, conventional saline-alkali soil amendments, after being applied to the soil, are susceptible to stress from the saline-alkali environment, resulting in low survival rates, rapid decomposition, and a mismatch between nutrient release and crop needs, leading to low utilization efficiency. Furthermore, while there are reports of using biochar and polymer materials for saline-alkali soil amendment, these technologies often focus on improving a single function, resulting in unsatisfactory effects. Therefore, developing a saline-alkali soil amendment composition that can effectively reduce soil salinity and alkalinity while continuously improving soil physical structure is a pressing technical problem in the field of agricultural soil improvement. Summary of the Invention

[0005] The first objective of this invention is to provide a composition for improving saline-alkali land.

[0006] A second objective of the present invention is to provide a method for preparing a composition for improving saline-alkali land.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A composition for improving saline-alkali land, the composition comprising the following raw materials in parts by weight: 30-45 parts straw powder, 1-3 parts microbial inoculant, 5-8 parts film-forming agent, 12-15 parts humic acid, 5-10 parts biochar gel microspheres, and 15-20 parts desulfurized gypsum; the preparation of the biochar gel microspheres includes the following steps: (1) Crush and calcine corn stalks to obtain biochar; take coccolithophora powder, add water and stir evenly to obtain coccolithophora dispersion; (2) Add the biochar and spheroidal dispersion obtained in step (1) to the sodium alginate solution and stir until homogeneous to obtain a mixed solution; (3) Add the mixed solution obtained in step (2) to calcium chloride solution for calcification to obtain biochar gel microspheres.

[0008] Further, the calcination temperature in step (1) is 500-700℃ and the time is 2-4h; the mass ratio of the algae powder to water is 1:15-20.

[0009] Further, the concentration of the sodium alginate solution in step (2) is 2-4 wt%; the mass ratio of the biochar, the coccolithophora powder in the dispersion, and the sodium alginate in the sodium alginate solution is 1:1-2:0.5-1.

[0010] Further, in step (3), the volume ratio of the mixed solution to the calcium chloride solution is 1:1.5-2; the concentration of the calcium chloride solution is 1-2wt%; and the calcification time is 22-24h.

[0011] Furthermore, the preparation of the film-forming agent includes the following steps: S1. Remove impurities from seaweed, wash, dry, and pulverize it to obtain seaweed powder; add 15-20 times the weight of the seaweed powder to water and soak for 20-24 hours, filter, collect the filtrate and centrifuge to obtain the supernatant; S2. Concentrate the supernatant obtained in step S1 to 5-8% of its original volume to obtain a concentrate. Add 2-3 times the volume of anhydrous ethanol to the concentrate and precipitate for 12-15 hours. Centrifuge to collect the precipitate, add water to dissolve the precipitate, then add Sevag reagent to remove proteins, centrifuge, concentrate, and dry to obtain the film-forming agent.

[0012] Furthermore, the straw powder is corn straw powder; the diameter of the straw powder is 100-200μm.

[0013] Furthermore, the microbial agent is prepared by mixing Bacillus subtilis and Lactobacillus plantarum powders at a mass ratio of 1:(0.5-1).

[0014] A method for preparing a composition for improving saline-alkali land specifically includes the following steps: According to the formula, desulfurized gypsum is crushed, and then straw powder, microbial inoculant, film-forming agent, humic acid and biochar gel microspheres are added, mixed evenly, and granulated to obtain a composition for saline-alkali land improvement.

[0015] Compared with the prior art, the main advantages of the present invention are as follows: This invention provides a composition for improving saline-alkali land and its preparation method. By synergistically combining straw powder, microbial agents, film-forming agents, humic acid, biochar gel microspheres and desulfurized gypsum, comprehensive improvement of saline-alkali land can be achieved.

[0016] On the one hand, the present invention uses sea hay as raw material, and the sea hay extract obtained by extraction has excellent film-forming properties. When the composition is applied to the soil, the sea hay extract, as a film-forming agent, can form a dense protective film on the surface of soil particles, which can effectively slow down the dissolution rate of active components in the composition, so that the active ingredients are continuously and stably released as the film layer gradually degrades, thereby improving the utilization efficiency of the saline-alkali land improvement composition. At the same time, the film layer can effectively block the migration of salt with water, thereby improving the stability of soil aggregate structure, promoting the formation of water-stable aggregates, reducing the degree of soil dispersion, and alleviating soil compaction.

[0017] On the other hand, this invention uses corn straw biochar, coccolithia powder, and sodium alginate as raw materials, and completes calcification cross-linking with calcium chloride to prepare biochar gel microspheres. Calcium ions dissociated from calcium chloride combine with sodium alginate to form a three-dimensional network gel structure, uniformly encapsulating and fixing the biochar and coccolithia powder within the network. After application to saline-alkali land, the calcium ions in the gel network can undergo ion exchange with sodium ions in the soil colloid, and the sodium ions are adsorbed and fixed by the carboxyl groups of sodium alginate. The shell of coccolithia is rich in calcium carbonate, serving as a natural calcium source that can effectively replenish calcium ions lost through ion exchange, achieving sustained sodium ion exchange, thereby reducing soil salinity and mitigating the harm of soil salinization. Simultaneously, biochar effectively adsorbs harmful salt ions in the soil through its porous structure and abundant surface functional groups, and its skeletal structure enhances the mechanical strength and stability of the gel microspheres. The saline-alkali land improvement composition provided by this invention synergistically improves and enhances the soil's dispersion, alleviates soil compaction, and effectively reduces soil salinity, providing a new approach for the comprehensive management of saline-alkali land. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the biochar gel microspheres obtained in Example 1 of the present invention. Detailed Implementation

[0019] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products obtained through commercial channels.

[0020] The desulfurized gypsum of this invention contains ≥80% calcium sulfate; the straw powder is corn straw powder; the diameter of the straw powder is 100-200μm. Bacillus subtilis powder was purchased from Baoding Ruigu Biotechnology Co., Ltd., with a live bacteria content of 20 billion CFU / g; Lactobacillus plantarum powder was purchased from Shaanxi Lanhe Biotechnology Co., Ltd., with a live bacteria content of 10 billion CFU / g.

[0021] Example 1 A composition for improving saline-alkali land, the composition comprising the following raw materials in parts by weight: 35 parts straw powder, 2 parts microbial agent, 6 parts film-forming agent, 14 parts humic acid, 8 parts biochar gel microspheres, and 18 parts desulfurized gypsum.

[0022] The microbial agent is prepared by mixing Bacillus subtilis and Lactobacillus plantarum powders in a mass ratio of 1:0.8.

[0023] The preparation of the biochar gel microspheres includes the following steps: (1) Crush corn stalks to 2 mm, dry them, and calcine them at 600℃ for 3 h under nitrogen protection, then cool them to room temperature to obtain biochar; take coccolith powder, add 18 times the mass of water to coccolith powder and stir evenly to obtain coccolith dispersion. (2) Disperse sodium alginate in deionized water and stir it with ultrasound to dissolve it completely to obtain a sodium alginate solution with a concentration of 3wt%. Then add biochar and coccolithophora dispersion to the sodium alginate solution and stir evenly to obtain a mixed solution. The mass ratio of biochar, coccolithophora powder in coccolithophora dispersion and sodium alginate in sodium alginate solution is 1:1.5:0.8.

[0024] (3) The mixed solution was added dropwise to a 1.5 wt% calcium chloride solution, with a volume ratio of 1:1.8, and calcified for 23 h. Then, the microspheres were washed with deionized water to obtain biochar gel microspheres. The scanning electron microscope image of the biochar gel microspheres is shown below. Figure 1 As shown. By Figure 1 It can be seen that the particles are regularly spherical, indicating that the cross-linking of sodium alginate and calcium chloride can uniformly encapsulate and fix biochar and spherical algae powder inside the network, thus successfully preparing biochar gel microspheres.

[0025] The preparation of the film-forming agent includes the following steps: S1. The sea hail seaweed is cleaned, dried and crushed to obtain sea hail seaweed powder; 18 times the weight of the sea hail seaweed powder is added to water for soaking for 22 hours. After soaking, the solution is filtered, the filtrate is collected and centrifuged to obtain the supernatant. S2. Concentrate the supernatant obtained in step S1 to 6% of its original volume to obtain a concentrate. Add 2.5 times the volume of anhydrous ethanol to the concentrate, precipitate for 13 hours, centrifuge, and redissolve the precipitate in water. Then add Sevag reagent to remove proteins, centrifuge, concentrate under reduced pressure, and freeze dry to obtain the film-forming agent.

[0026] A method for preparing a composition for improving saline-alkali land specifically includes the following steps: According to the formula, desulfurized gypsum is crushed and passed through a 40-mesh sieve, and then straw powder, microbial inoculants, film-forming agents, humic acid and biochar gel microspheres are added, mixed evenly, and granulated to obtain a composition for improving saline-alkali land.

[0027] Example 2 A composition for improving saline-alkali land, the composition comprising the following raw materials in parts by weight: 30 parts straw powder, 1 part microbial agent, 5 parts film-forming agent, 12 parts humic acid, 5 parts biochar gel microspheres, and 15 parts desulfurized gypsum.

[0028] The microbial agent is prepared by mixing Bacillus subtilis and Lactobacillus plantarum powders in a mass ratio of 1:0.5.

[0029] The preparation of the biochar gel microspheres includes the following steps: (1) Crush corn stalks to 2 mm, dry them, and calcine them at 500°C for 4 hours under nitrogen protection, then cool them to room temperature to obtain biochar; take coccolith powder, add 15 times the mass of water to coccolith powder and stir evenly to obtain coccolith dispersion. (2) Disperse sodium alginate in deionized water and stir it with ultrasound to dissolve it completely to obtain a sodium alginate solution with a concentration of 2wt%. Then add biochar and coccolithophora dispersion to the sodium alginate solution and stir evenly to obtain a mixed solution. The mass ratio of biochar, coccolithophora powder in coccolithophora dispersion and sodium alginate in sodium alginate solution is 1:1:0.5.

[0030] (3) The mixed solution was added dropwise to a calcium chloride solution with a concentration of 1 wt%, wherein the volume ratio of the mixed solution to the calcium chloride solution was 1:1.5, and calcification was carried out for 22 hours. Then, the mixture was washed with deionized water to obtain biochar gel microspheres.

[0031] The preparation of the film-forming agent includes the following steps: S1. The sea hail seaweed is cleaned, dried and crushed to obtain sea hail seaweed powder; 15 times the weight of the sea hail seaweed powder is added to water for soaking for 20 hours. After soaking, the solution is filtered, the filtrate is collected and centrifuged to obtain the supernatant. S2. Concentrate the supernatant obtained in step S1 to 7% of its original volume to obtain a concentrate. Add two volumes of anhydrous ethanol to the concentrate, precipitate for 12 hours, centrifuge, and redissolve the precipitate in water. Then add Sevag reagent to remove proteins, centrifuge, concentrate under reduced pressure, and freeze dry to obtain the film-forming agent.

[0032] A method for preparing a composition for improving saline-alkali land specifically includes the following steps: According to the formula, desulfurized gypsum is crushed and passed through a 40-mesh sieve, and then straw powder, microbial inoculants, film-forming agents, humic acid and biochar gel microspheres are added, mixed evenly, and granulated to obtain a composition for improving saline-alkali land.

[0033] Example 3 A composition for improving saline-alkali land, the composition comprising the following raw materials in parts by weight: 45 parts straw powder, 3 parts microbial agent, 8 parts film-forming agent, 15 parts humic acid, 10 parts biochar gel microspheres, and 20 parts desulfurized gypsum.

[0034] The microbial agent is prepared by mixing Bacillus subtilis and Lactobacillus plantarum powders in a mass ratio of 1:1.

[0035] The preparation of the biochar gel microspheres includes the following steps: (1) Crush corn stalks to 2 mm, dry them, and calcine them at 700℃ for 2 h under nitrogen protection, then cool them to room temperature to obtain biochar; take coccolith powder, add 20 times the mass of water to coccolith powder and stir evenly to obtain coccolith dispersion; (2) Disperse sodium alginate in deionized water and stir it with ultrasound to dissolve it completely to obtain a sodium alginate solution with a concentration of 4wt%. Then add biochar and coccolithophora dispersion to the sodium alginate solution and stir evenly to obtain a mixed solution. The mass ratio of biochar, coccolithophora powder in coccolithophora dispersion and sodium alginate in sodium alginate solution is 1:2:1.

[0036] (3) The mixed solution was added dropwise to a calcium chloride solution with a concentration of 2wt%, wherein the volume ratio of the mixed solution to the calcium chloride solution was 1:2, and calcification was carried out for 24 hours. Then, the mixture was washed with deionized water to obtain biochar gel microspheres.

[0037] The preparation of the film-forming agent includes the following steps: S1. The sea hail is cleaned, dried and crushed to obtain sea hail powder; 20 times the weight of the sea hail powder is added to water for soaking for 24 hours. After soaking, the solution is filtered, the filtrate is collected and centrifuged to obtain the supernatant. S2. Concentrate the supernatant obtained in step S1 to 5% of its original volume to obtain a concentrate. Add 3 times the volume of anhydrous ethanol to the concentrate, precipitate for 15 hours, centrifuge, and redissolve the precipitate in water. Then add Sevag reagent to remove proteins, centrifuge, concentrate under reduced pressure, and freeze dry to obtain the film-forming agent.

[0038] A method for preparing a composition for improving saline-alkali land specifically includes the following steps: According to the formula, desulfurized gypsum is crushed and passed through a 40-mesh sieve, and then straw powder, microbial inoculants, film-forming agents, humic acid and biochar gel microspheres are added, mixed evenly, and granulated to obtain a composition for improving saline-alkali land.

[0039] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 omits coccolithophores in the preparation process of biochar gel microspheres, while otherwise it remains the same as Example 1.

[0040] Specifically, the preparation of the biochar gel microspheres includes the following steps: (1) Crush corn stalks to 2 mm, dry them, heat them to 600℃ and calcine them for 3 hours, then cool them to room temperature to obtain biochar; (2) Disperse sodium alginate in deionized water and stir it with ultrasound to dissolve it completely to obtain a sodium alginate solution with a concentration of 3wt%. Then add biochar to the sodium alginate solution and stir evenly to obtain a mixed solution. The mass ratio of biochar to sodium alginate in the sodium alginate solution is 1:0.8.

[0041] (3) The mixed solution was added dropwise to a calcium chloride solution with a concentration of 1.5 wt%, wherein the volume ratio of the mixed solution to the calcium chloride solution was 1:1.8, and calcification was carried out for 23 hours. Then, the mixture was washed with deionized water to obtain biochar gel microspheres.

[0042] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 omits the film-forming agent, while everything else remains the same as Example 1.

[0043] Application Example 1 The experimental site was a saline-alkali land field. The initial physicochemical properties of the soil were as follows: soil organic matter 8.65 g / kg, field water holding capacity 15.92%; total water-soluble salts 3.43 g / kg; soil bulk density 1.71 g / cm³. 3 The alkalinity was 13.12%. The above experimental fields were divided into Example 1-3 groups and Comparative Example 1-2 groups, with 3 replicates in each group.

[0044] For Examples 1-3 and Comparative Examples 1-2, the prepared saline-alkali land improvement compositions were evenly spread on the soil surface at a rate of 30 kg / mu (approximately 0.067 hectares). Rotary tillage was then performed to a depth of 15 cm to ensure thorough mixing of the compositions with the topsoil. Corn (Jidan 27) was planted 5 days later in June. During the experiment, irrigation, weeding, and pest and disease control measures remained consistent across all groups.

[0045] Soil property testing: After corn harvest, the physicochemical properties of each treatment group were tested, as detailed below: 1. Collect soil samples. During the collection process, use a ring cutter with an inner diameter of 5cm to take samples and determine the soil bulk density. 2. The water-stable aggregates were measured using a soil aggregate analyzer, and the content of water-stable aggregates with a particle size > 0.25 mm was calculated. 3. Determine the total amount of water-soluble salts according to NY / T 1121.16-2006; 4. The alkalinity was determined using LY / T 1249-1999. The results are recorded in Table 1.

[0046] After the corn harvest, the corn yield was tallied; the results are shown in Table 2.

[0047] Table 1

[0048] As shown in Table 1, the soil bulk density, total water-soluble salt content, and alkalinity of Examples 1-3 were all lower than those of Comparative Examples 1 and 2. This indicates that the composition of the present invention can not only effectively reduce soil compaction and alleviate soil compaction, but also effectively reduce soil salinity and alleviate the harm of saline-alkali soil. Compared with Example 1, the soil bulk density, total water-soluble salt content, and alkalinity of Comparative Example 1 (omitting the coccolithophores) increased, indicating that the coccolithophores in the biochar gel microspheres can effectively replenish calcium ions lost due to ion exchange, achieving sustained sodium ion exchange, which can reduce soil salinity and alleviate soil salinization. Compared with Example 1, the soil bulk density, total water-soluble salt content, and alkalinity of Comparative Example 2 increased after omitting the film-forming agent, indicating that the film-forming agent can improve the utilization efficiency of the saline-alkali soil improvement composition, reduce soil dispersion, and alleviate soil compaction.

[0049] The water-stable aggregate content in Examples 1-3 was higher than that in Comparative Examples 1 and 2. The water-stable aggregate content in Comparative Example 2 was significantly lower than that in Example 1. This is because the film-forming agent can form a dense protective film on the surface of soil particles, promoting the formation of water-stable aggregates and improving soil structural stability.

[0050] Table 2

[0051] As shown in Table 2, the yields of Examples 1-3 were higher than those of Comparative Examples 1 and 2. This is consistent with the trend of the comprehensive indicators of Examples 1-3 in Table 1, such as soil bulk density, salinity and alkalinity reduction, and water-stable aggregates. This indicates that the composition of the present invention effectively promotes maize growth by improving the soil environment.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A composition for improving saline-alkali land, characterized in that, The composition comprises the following raw materials in parts by weight: 30-45 parts straw powder, 1-3 parts microbial agent, 5-8 parts film-forming agent, 12-15 parts humic acid, 5-10 parts biochar gel microspheres, and 15-20 parts desulfurized gypsum. The preparation of the biochar gel microspheres includes the following steps: (1) Crush and calcine corn stalks to obtain biochar; take coccolithophora powder, add water and stir evenly to obtain coccolithophora dispersion; (2) Add the biochar and spheroidal dispersion obtained in step (1) to the sodium alginate solution and stir until homogeneous to obtain a mixed solution; (3) Add the mixed solution obtained in step (2) to calcium chloride solution for calcification to obtain biochar gel microspheres.

2. The composition for improving saline-alkali land according to claim 1, characterized in that, The calcination temperature in step (1) is 500-700℃ and the time is 2-4h.

3. The composition for improving saline-alkali land according to claim 1, characterized in that, The mass ratio of the algae powder and water in step (1) is 1:15-20.

4. The composition for improving saline-alkali land according to claim 1, characterized in that, The concentration of the sodium alginate solution in step (2) is 2-4 wt%; the mass ratio of the biochar, the coccolithophora dispersion, and the sodium alginate in the sodium alginate solution is 1:1-2:0.5-1.

5. The composition for improving saline-alkali land according to claim 1, characterized in that, In step (3), the volume ratio of the mixed solution to the calcium chloride solution is 1:1.5-2; the concentration of the calcium chloride solution is 1-2 wt%; and the calcification time is 22-24 h.

6. The composition for improving saline-alkali land according to claim 1, characterized in that, The preparation of the film-forming agent includes the following steps: S1. Remove impurities from seaweed, wash, dry, and pulverize it to obtain seaweed powder; add 15-20 times the weight of the seaweed powder to water and soak for 20-24 hours, filter, collect the filtrate and centrifuge to obtain the supernatant; S2. Concentrate the supernatant obtained in step S1 to 5-8% of its original volume to obtain a concentrate. Add 2-3 times the volume of anhydrous ethanol to the concentrate and precipitate for 12-15 hours. Centrifuge to collect the precipitate, add water to dissolve the precipitate, then add Sevag reagent to remove proteins, centrifuge, concentrate, and dry to obtain the film-forming agent.

7. The composition for improving saline-alkali land according to claim 1, characterized in that, The straw powder is corn straw powder; the diameter of the straw powder is 100-200μm.

8. The composition for improving saline-alkali land according to claim 1, characterized in that, The microbial agent is prepared by mixing Bacillus subtilis and Lactobacillus plantarum powders at a mass ratio of 1:(0.5-1).

9. A method for preparing a composition for improving saline-alkali land according to any one of claims 1-8, characterized in that, Specifically, the following steps are included: According to the formula, desulfurized gypsum is crushed, and then straw powder, microbial inoculant, film-forming agent, humic acid and biochar gel microspheres are added, mixed evenly, and granulated to obtain a composition for saline-alkali land improvement.

Images