Organic-inorganic composite salt-alkali soil improvement fertilizer and preparation method thereof

Abstract

The application relates to the technical field of saline-alkali soil improvement, in particular to an organic-inorganic composite saline-alkali soil improvement fertilizer and a preparation method thereof. The improvement fertilizer comprises, in terms of weight parts, 25-40 parts of straw biochar, 15-25 parts of humic acid, 20-35 parts of organic fertilizer, 10-20 parts of desulfurized gypsum, 5-12 parts of sulfur, 3-8 parts of superphosphoric acid, 2-6 parts of ferrous sulfate, 4-10 parts of a modified functional agent, 6-12 parts of a filling agent, 2-5 parts of a composite microbial agent and 3-6 parts of a binder. The modified functional agent and the filling agent are added, the adsorption and fixation capacity of the improvement fertilizer to salt ions and the soil structure improvement capacity are significantly enhanced, the organic material and the inorganic material are synergistically compounded, the improvement fertilizer is suitable for the improvement of medium and heavy saline-alkali soil, and the improvement fertilizer is particularly suitable for the synergistic application of a straw interlayer technology.

Description

Technical Field

[0001] This invention relates to the field of improved fertilizer technology, specifically to an organic-inorganic compound saline-alkali land improvement fertilizer and its preparation method. Background Technology

[0002] Excessive salt ions and high pH levels in saline-alkali soils severely inhibit crop growth, leading to low yields or even crop failure. Traditional methods for improving saline-alkali soils mainly include water conservancy engineering measures (irrigation to leach salt, open ditch drainage, and underground pipe salt removal), chemical improvement measures (application of gypsum, sulfur, ferrous sulfate, etc.), and biological improvement measures (planting salt-tolerant plants, applying organic fertilizers, and microbial agents, etc.). However, single improvement measures have problems such as limited effectiveness, high cost, and long cycle time.

[0003] In recent years, straw-based salt-blocking technology has attracted widespread attention as a novel physical soil improvement method. This technology involves laying straw beneath the topsoil (a process of soil lifting, spreading, and covering) to form an isolation layer. The capillary action of the straw layer inhibits the upward migration of deep-seated salts while simultaneously promoting water infiltration and salt leaching, effectively controlling salt accumulation in the topsoil. However, while straw-based salt-blocking primarily addresses the issue of salt upward migration, its effects on improving soil structure, enhancing fertility, and activating biological activity are limited.

[0004] Research on organic-inorganic composite soil amendments has provided a new approach for the comprehensive improvement of saline-alkali land. Organic materials (biochar, humic acid, organic fertilizer) can improve soil structure, increase organic matter content, and enhance cation exchange capacity; inorganic materials (desulfurized gypsum, sulfur, ferrous sulfate, etc.) can provide calcium ions to replace sodium ions, lower soil pH, and supplement trace elements. The synergistic use of both can produce an improvement effect of "1+1>2". However, existing composite soil amendment products have the following technical problems:

[0005] First, the combination of organic and inorganic components lacks scientific basis and has not been optimized for different degrees of salinization, resulting in poor product adaptability and unstable effects.

[0006] Second, the addition of microbial agents lacks specificity. Conventional microbial agents are difficult to adapt to the high-salt, high-pH environment of saline-alkali land, resulting in poor survival rates and colonization abilities, thus limiting their functionality.

[0007] Third, the product preparation process has a significant impact on microbial activity; high-temperature granulation and high-temperature drying will greatly reduce the live bacteria content of the inoculant.

[0008] Fourth, there is a lack of systematic research on the synergistic application of products and straw barrier technology, and a comprehensive technical system of "physical barrier + chemical improvement + biological activation" has not been formed.

[0009] To address the aforementioned technical problems, this invention develops an organic-inorganic compound fertilizer for improving saline-alkali land, which is suitable for saline-alkali land improvement and can be used in conjunction with straw interlayer technology, by screening salt-tolerant functional bacteria, optimizing the organic-inorganic component ratio, and developing a low-temperature preparation process. Summary of the Invention

[0010] In view of the deficiencies of the prior art, the purpose of this invention is to provide an organic-inorganic composite saline-alkali land improvement fertilizer and its preparation method, so as to solve the problems mentioned in the background art.

[0011] The present invention solves the technical problem by adopting the following technical solution:

[0012] This invention provides an organic-inorganic compound fertilizer for improving saline-alkali land. The raw materials, by weight, include: 25-40 parts straw biochar, 15-25 parts humic acid, 20-35 parts organic fertilizer, 10-20 parts desulfurized gypsum, 5-12 parts sulfur, 3-8 parts superphosphate, 2-6 parts ferrous sulfate, 4-10 parts modified functional agent, 6-12 parts filler, 2-5 parts compound microbial agent, and 3-6 parts binder.

[0013] (I) Preparation of Modified Functional Agents

[0014] Preferably, the method for preparing the modified functional agent is as follows:

[0015] S201: Mix nano zeolite and nano sepiolite in a weight ratio of (3-5):(1-2), add 3-5 times the mass of deionized water, and ultrasonically disperse for 30-60 min to obtain a mixed mineral dispersion.

[0016] S202: Add 5-10% of polydimethyldiallylammonium chloride and 3-6% of chitosan by total mineral mass to the mixed mineral dispersion, and stir at 400-600 r / min for 2-3 h at 40-60℃.

[0017] S203: After the reaction is complete, filter and wash, dry at 80-100℃ for 4-6 hours, grind through a 200-300 mesh sieve to obtain the modified functional agent.

[0018] Design principles of modified functional agents:

[0019] Nano-zeolites possess a three-dimensional framework structure and uniform microporous channels (pore size 0.3-1.0 nm), resulting in a large specific surface area (≥300 m²). 2 / g), silicon-to-aluminum ratio adjustable. The zeolite framework carries a permanent negative charge and is effective against Na+. + K + Ca 2+ Mg 2+Cationic ions possess strong ion exchange and selective adsorption capabilities. In the improvement of saline-alkali land, nano-zeolites can adsorb Na+ from the soil solution. + This reduces sodium ion activity and, at the same time, reacts with the Ca provided by the desulfurized gypsum. 2+ Ion exchange occurs, promoting the replacement of sodium ions with calcium ions and their excretion with water.

[0020] Nano-sepiolite is a fibrous hydrous magnesium silicate mineral with a nanoscale fibrous structure (length 200-500 nm, diameter 10-30 nm) and a specific surface area ≥200 m². 2 / g. Sepiolite has a unique porous structure and surface active sites, which can adsorb salt ions. At the same time, its fibrous structure can penetrate between soil particles, enhancing the stability of soil aggregates.

[0021] Polydimethyl diallyl ammonium chloride is a cationic polymer with a positive charge. It can be adsorbed onto the negatively charged surfaces of zeolites and sepiolite via electrostatic interactions, forming a polymer coating layer on the mineral particles. This can modulate the surface charge properties of minerals and enhance their attraction to anions (such as Cl-). - SO4 2- On the one hand, the polymer has the ability to adsorb mineral particles; on the other hand, the long chain structure of the polymer can form bridges between mineral particles, preventing the aggregation of nanoparticles.

[0022] Chitosan is a natural cationic polysaccharide with biocompatibility and biodegradability. The abundant hydroxyl and amino groups on the chitosan molecular chain can form hydrogen bonds with the silanol groups on the surface of zeolite and sepiolite, simultaneously forming a hydrophilic organic layer on the mineral surface, enhancing its compatibility with soil organic matter. The addition of chitosan can also promote the formation of soil aggregates and improve soil structure.

[0023] Synergistic effect of nano-zeolite and nano-sepiolite: Zeolite provides a three-dimensional porous structure to realize ion exchange and molecular sieving, while sepiolite provides a fibrous structure to realize physical interpenetration and network reinforcement. The two work together to form a dual-reinforcement network of "pore adsorption + fiber bridging".

[0024] Preferably, the nano-zeolite has a particle size of 50-150 nm, a silicon-to-aluminum ratio of 2-5, and a specific surface area ≥300 m². 2 / g; the nano-sepiolite fibers have a length of 200-500nm, a diameter of 10-30nm, and a specific surface area ≥200m². 2 / g; the degree of deacetylation of the chitosan is ≥90%, and the molecular weight is 50,000-200,000.

[0025] (II) Preparation of the filler

[0026] Preferably, the filler is prepared by:

[0027] S301: Mix diatomaceous earth and vermiculite in a weight ratio of (5-8):(3-5) and calcine at 300-500℃ for 1-2 hours to obtain an activated composite carrier;

[0028] S302: Add the activated composite carrier to a 3-8% (w / w) polyvinyl alcohol solution, soak for 2-4 hours, filter, and dry at 60-80℃ to obtain the polymer-modified carrier;

[0029] S303: Mix the polymer-modified carrier with sodium carboxymethyl cellulose at a weight ratio of (8-12):1, add 5-10% glycerol of the total carrier mass, spray wet, granulate, and pass through a 20-60 mesh sieve to obtain the filler.

[0030] Design principles of filler:

[0031] Diatomite is a biogenic siliceous sedimentary rock, mainly composed of diatom remains, with a rich microporous structure (pore size 50-500 nm) and a specific surface area ≥ 50 m². 2 Diatomaceous earth possesses excellent water absorption, retention, and adsorption properties, enabling it to adsorb salt ions. Simultaneously, its porous structure provides a habitat for microorganisms. After calcination and activation, the organic matter in diatomaceous earth is removed, making the pores more open and improving its adsorption performance.

[0032] Vermiculite is a layered silicate mineral with excellent cation exchange capacity (CEC ≥ 100 cmol / kg). After high-temperature calcination, it expands 8-20 times, forming a porous structure with expanded interlayers. Expanded vermiculite has good water absorption and retention capacity and ion exchange capacity, and can adsorb K+. + Ca 2+ Mg 2+ Isonutrient molecules provide a sustained-release effect.

[0033] Polyvinyl alcohol (PVA) is used as a film-forming material to form a hydrophilic polymer film on the surface of diatomite and vermiculite. On the one hand, it enhances the structural stability of the composite carrier and prevents it from disintegrating during application and irrigation; on the other hand, the hydroxyl groups of PVA can form hydrogen bonds with soil particles, promoting the formation of aggregates.

[0034] Sodium carboxymethyl cellulose acts as a binder and thickener, playing a binding and shaping role in the granulation process; glycerin acts as a plasticizer and humectant, improving the flexibility and water retention of the granules.

[0035] Synergistic effect of diatomite and vermiculite: Diatomite provides a multi-level porous structure to achieve physical adsorption, while vermiculite provides a layered structure to achieve ion exchange and slow release of nutrients. The combination of the two forms a dual-functional carrier of "porous adsorption + interlayer exchange".

[0036] Preferably, the diatomaceous earth has a silica content of ≥75% and a specific surface area of ​​≥50 m². 2 / g; the expansion ratio of the vermiculite is ≥8 times, and the cation exchange capacity is ≥100cmol / kg; the degree of alcoholysis of the polyvinyl alcohol is 85-99%, and the molecular weight is 5000-20000.

[0037] (iii) Other components

[0038] The method for preparing the straw biochar is as follows: crop straw is pyrolyzed at 400-500℃ under limited oxygen for 2-4 hours and then crushed and passed through a 40-80 mesh sieve; the humic acid is mineral-derived humic acid with a humic acid content ≥50%; the organic fertilizer is prepared by composting and fermenting cow and sheep manure and earthworm castings with an organic matter content ≥45%.

[0039] The desulfurized gypsum is a byproduct of flue gas desulfurization in coal combustion, with a calcium sulfate dihydrate content ≥85%; the sulfur is industrial sulfur powder with a sulfur content ≥99%; the superphosphate is ordinary superphosphate with an effective P2O5 content ≥16%; and the ferrous sulfate is ferrous sulfate heptahydrate with a FeSO4·7H2O content ≥95%.

[0040] The preparation method of the compound microbial agent is as follows:

[0041] S501: *Bacillus amyloliquefaciens*, *Bacillus subtilis*, *Bacillus megaterium*, *Bacillus mucilaginosus*, *Bacillus licheniformis*, and *Bacillus halophilicus* are cultured separately in a liquid submerged fermentation process, with a viable cell count ≥10⁻⁶ in the fermentation broth. 9 CFU / mL, add 1-2% NaCl to the fermentation medium of each strain for salt tolerance acclimatization;

[0042] S502: Mix the fermentation broths of various strains in a weight ratio of (2-3):(1.5-2.5):(1-2):(1-1.5):(0.8-1.5):(0.5-1), add 10-20% corn starch and 5-10% trehalose of the total fermentation broth, and spray dry (inlet air temperature 120-140℃, outlet air temperature 60-80℃) to obtain a compound microbial powder with a viable bacteria content ≥5×10⁻⁶. 10 CFU / g.

[0043] The introduction of halophilic and alkaliphilic bacteria is the key innovation of this invention, which solves the problem of low survival rate of conventional microbial agents in saline-alkali environments.

[0044] The binder is at least one of bentonite, starch, and polyacrylamide.

[0045] (iv) Preparation method

[0046] This invention also provides a method for preparing an organic-inorganic compound saline-alkali land improvement fertilizer, comprising the following steps: S601: Desulfurized gypsum, sulfur, superphosphate, and ferrous sulfate are pulverized and passed through a 60-100 mesh sieve, and mixed evenly according to the specified ratio to obtain an inorganic mixture; S602: Straw biochar, humic acid, and organic fertilizer are mixed according to the specified ratio, pulverized and passed through a 40-60 mesh sieve, and mixed evenly to obtain an organic mixture; S603: Modifying functional agent and filler are mixed and stirred at 200-300 r / min for 10-20 min to obtain a functional-filler premix; S604: The inorganic mixture, Organic Mixture and Function - Add the premixed material into the mixer and stir for 15-30 minutes to obtain the main mixture; S605: Mix the compound microbial agent and binder evenly, add them to the main mixture, and continue stirring for 10-20 minutes to obtain the improved fertilizer mixture; S606: Extrude the improved fertilizer mixture or use disc granulation, with a particle size of 3-8 mm and a granulation pressure of 15-25 MPa; S607: Dry the granules at a low temperature of 40-55℃, controlling the moisture content to ≤10%, and then sieve and grade; S608: Vacuum package to obtain the organic-inorganic compound saline-alkali land improvement fertilizer.

[0047] (v) Synergistic application with straw interlayer technology

[0048] This invention's improved fertilizer is particularly suitable for synergistic application with straw interlayer technology. The installation of the straw interlayer involves four steps: "soil lifting—material spreading—soil covering—compacting."

[0049] First, the wide-blade shovel, controlled by a hydraulic cylinder, cuts into a predetermined depth (30-40cm), smoothly lifting the intact soil layer. The lifted soil then enters a vibrating conveyor chain, where it is initially broken up during the backward transport. The retaining plate behind the shovel and below the conveyor chain forms a stable, full-width cavity. The straw in the feed box is pushed backward at a controllable speed by the bottom conveyor chain. After being initially broken up by the coarse feeding roller and forcibly torn apart by the fine spreading roller, it is evenly scattered downward into the cavity along the full width of the machine. The adjustable scraper at the rear levels the straw layer, forming a straw layer of uniform thickness. The soil falling from the conveyor chain naturally covers the straw layer, and the compaction roller compacts it, completing the four processes of "lifting soil, spreading material, covering soil, and compacting".

[0050] After the straw interlayer is buried, apply this improved fertilizer to the topsoil layer (0-30cm) above the interlayer at a rate of 200-600 kg / mu. The straw interlayer inhibits the upward movement of deep salts, while the improved fertilizer reduces residual salts in the topsoil layer and improves soil fertility. Together, they form a comprehensive improvement system integrating "interlayer-improvement-cultivation".

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] 1. This invention, through the design of a modified functional agent (modified nano-zeolite-sepiolite composite), utilizes the synergistic effect of the three-dimensional porous structure of nano-zeolite and the fibrous structure of nano-sepiolite, and through dual modification with polydimethyldiallyl ammonium chloride and chitosan, significantly improves the resistance to Na+. + Cl - SO4 2- The adsorption and fixation capacity of salt ions is increased by more than 30% compared with conventional modifiers.

[0053] 2. This invention designs an infill agent (modified diatomite-vermiculite composite), which is then activated by calcination and modified with polyvinyl alcohol to form a composite carrier with a multi-level pore structure and excellent ion exchange performance. This can effectively improve the soil aggregate structure, increase soil porosity and permeability, and enhance salt leaching efficiency.

[0054] 3. The modified functional agent and the filler of this invention have a synergistic effect. The modified functional agent provides nanoscale ion adsorption and exchange functions, while the filler provides micrometer-scale structural support and water and fertilizer retention functions. The two form a "nano-micro" multi-scale composite structure, which constructs a three-dimensional network framework in the soil, significantly improving the physical structure and chemical properties of the soil.

[0055] 4. The compound microbial agent of the present invention contains halophilic and alkaliphilic Bacillus, which can adapt to the high-salt and high-pH environment of saline-alkali land, and work synergistically with functional bacteria such as phosphorus-solubilizing, potassium-solubilizing, and antibacterial bacteria to achieve bio-enhancing effects of "adjusting salt with bacteria and promoting growth with bacteria".

[0056] 5. This invention employs a low-temperature drying process and vacuum packaging to maximize the preservation of microbial inoculant activity, resulting in a product viable bacteria content ≥ 5 × 10⁻⁶. 10 CFU / g, shelf life can reach more than 18 months.

[0057] 6. This invention has good synergy with straw layer technology, forming a four-in-one comprehensive improvement system for saline-alkali land, which integrates "physical barrier (straw layer) + chemical improvement (calcium ion replacement) + biological activation (microbial agents) + structural reshaping (functional agents and fillers)". It can effectively manage moderate to severe saline-alkali land and increase crop yield by 40-60%. Detailed Implementation

[0058] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] Example 1

[0060] An organic-inorganic compound fertilizer for improving saline-alkali land, the raw materials by weight include: 32 parts straw biochar, 20 parts humic acid, 28 parts organic fertilizer, 15 parts desulfurized gypsum, 8 parts sulfur, 5 parts superphosphate, 4 parts ferrous sulfate, 7 parts modified functional agent, 9 parts filler, 3.5 parts compound microbial agent, and 4 parts bentonite.

[0061] (I) Preparation of Modified Functional Agents

[0062] Nano-zeolite (particle size 80nm, silicon-to-aluminum ratio 3.5, specific surface area 380m²) 2 / g), nano-sepiolite (fiber length 300nm, diameter 20nm, specific surface area 250m²) 2 Mix the minerals in a weight ratio of 4:1.5, add 4 times the mass of deionized water, and ultrasonically disperse for 45 min (power 500W) to obtain a mixed mineral dispersion; add 8% of the total mineral mass of polydimethyldiallyl ammonium chloride and 5% of chitosan (degree of deacetylation 92%, molecular weight 100,000) to the dispersion, and stir at 500 r / min for 2.5 h at 50 °C; filter, wash, dry at 90 °C for 5 h, grind through a 250 mesh sieve to obtain the modified functional agent.

[0063] (II) Preparation of the filler

[0064] Diatomaceous earth (SiO2 content 78%, specific surface area 65m² / g) and vermiculite (expansion ratio 10 times, CEC 125cmol / kg) were mixed at a weight ratio of 6.5:4 and calcined at 400℃ for 1.5h to obtain an activated composite carrier. The activated composite carrier was added to a 5% (w / w) polyvinyl alcohol solution (degree of alcoholysis 88%, molecular weight 12000) and soaked for 3h. After filtration, it was dried at 70℃ to obtain a polymer-modified carrier. The polymer-modified carrier was mixed with sodium carboxymethyl cellulose at a weight ratio of 10:1, and 8% (w / w) of glycerol was added to the total carrier mass. After spray wetting, the mixture was granulated and passed through a 40-mesh sieve to obtain the filler.

[0065] (III) Preparation of compound microbial agents

[0066] Fermentation culture of each strain: Bacillus amyloliquefaciens, Bacillus subtilis, Bacillus megaterium, Bacillus mucilaginosus, Bacillus licheniformis, and Bacillus halophilic-alkaliphilic were fermented separately. 1.5% NaCl was added to the fermentation medium, and the viable cell count in the fermentation broth was ≥10⁻⁶. 9 CFU / mL.

[0067] The fermentation broths of various strains were mixed in a weight ratio of 2.5:2:1.5:1.2:1.2:0.8, and 15% corn starch and 8% trehalose were added to the mixture. The mixture was then spray-dried (inlet air temperature 130℃, outlet air temperature 70℃) to obtain a compound microbial powder with a viable cell content of 5.8 × 10⁻⁶. 10 CFU / g.

[0068] (iv) Preparation of improved fertilizer

[0069] S601: Desulfurized gypsum, sulfur, superphosphate, and ferrous sulfate are pulverized and passed through an 80-mesh sieve, then mixed evenly according to the specified ratio to obtain an inorganic mixture; S602: Straw biochar (corn straw, pyrolyzed at 450℃ for 3 hours, passed through a 50-mesh sieve), humic acid (mineral source, content 55%), and organic fertilizer (composted cow and sheep manure, organic matter 48%) are mixed according to the specified ratio, pulverized and passed through a 50-mesh sieve, and mixed evenly to obtain an organic mixture; S603: Modified functional agent and filler are mixed and stirred at 250 r / min for 15 min to obtain a functional-filler premix; S604: Add the inorganic mixture, organic mixture, and functional premix to the mixer and stir for 20 minutes to obtain the main mixture; S605: Mix the compound microbial agent and bentonite evenly, add it to the main mixture, and continue stirring for 15 minutes to obtain the improved fertilizer mixture; S606: Extrude granulation, with a particle size of 4-6 mm and a granulation pressure of 20 MPa; S607: Dry the granules at a low temperature of 50℃, controlling the moisture content to ≤8%, and sieve and grade; S608: Vacuum package to obtain the organic-inorganic compound saline-alkali soil improved fertilizer.

[0070] Example 2

[0071] An organic-inorganic compound fertilizer for improving saline-alkali land, the raw materials by weight include: 25 parts straw biochar, 15 parts humic acid, 20 parts organic fertilizer, 10 parts desulfurized gypsum, 5 parts sulfur, 3 parts superphosphate, 2 parts ferrous sulfate, 4 parts modified functional agent, 6 parts filler, 2 parts compound microbial agent, and 3 parts starch.

[0072] Modifying functional agents: nano zeolite: nano sepiolite = 3:1, polydimethyldiallyl ammonium chloride 5%, chitosan 3%.

[0073] Filler: Diatomaceous earth:vermiculite = 5:3, calcination temperature 300℃, polyvinyl alcohol concentration 3%, polymer modified carrier to sodium carboxymethyl cellulose ratio 8:1.

[0074] The ratio of compound microbial inoculant is 2:1.5:1:1:0.8:0.5.

[0075] The preparation process is the same as in Example 1, with an extrusion granulation pressure of 15 MPa and a drying temperature of 40°C.

[0076] Example 3

[0077] An organic-inorganic compound fertilizer for improving saline-alkali land, the raw materials by weight include: 40 parts straw biochar, 25 parts humic acid, 35 parts organic fertilizer, 20 parts desulfurized gypsum, 12 parts sulfur, 8 parts superphosphate, 6 parts ferrous sulfate, 10 parts modified functional agent, 12 parts filler, 5 parts compound microbial agent, 3 parts bentonite, and 3 parts polyacrylamide.

[0078] Modifying functional agents: nano zeolite: nano sepiolite = 5:2, polydimethyldiallyl ammonium chloride 10%, chitosan 6%.

[0079] Filler: Diatomaceous earth:vermiculite = 8:5, calcination temperature 500℃, polyvinyl alcohol concentration 8%, polymer modified carrier to sodium carboxymethyl cellulose ratio 12:1.

[0080] The ratio of compound microbial inoculant is 3:2.5:2:1.5:1.5:1.

[0081] The preparation process is the same as in Example 1, with an extrusion granulation pressure of 25 MPa and a drying temperature of 55°C.

[0082] Scale settings

[0083] Comparative Example 1: No modifying functional agent was added, and the rest was the same as in Example 1.

[0084] Comparative Example 2: No filler was added, and the rest was the same as in Example 1.

[0085] Comparative Example 3: No nano-sepiolite was added to the modified functional agent (only nano-zeolite), and the rest was the same as in Example 1.

[0086] Comparative Example 4: No chitosan and polydimethyldiallylammonium chloride (unmodified) were added to the modified functional agent; the rest was the same as in Example 1.

[0087] Comparative Example 5: No vermiculite was added to the filler (only diatomaceous earth), and the rest was the same as in Example 1.

[0088] Comparative Example 6: The filler was not modified with polyvinyl alcohol, and the rest was the same as in Example 1.

[0089] Comparative Example 7: The compound microbial agent did not contain Bacillus halophilus or Bacillus alkaliphilus, and the rest was the same as in Example 1.

[0090] Comparative Example 8: No compound microbial agent was added; otherwise, it was the same as Example 1.

[0091] Comparative Example 9: Commercially available ordinary saline-alkali soil improvement fertilizer.

[0092] Performance testing

[0093] 1. Performance indicators of improved fertilizer products

[0094] Example 1 5.2 7.5 26 8.5 Example 2 4.0 8.2 22 10.2 Example 3 5.6 7.0 30 7.5 Comparative Example 1 5.1 7.6 25 9.0 Comparative Example 2 5.0 7.8 24 12.5 Comparative Example 3 5.0 7.7 25 9.2 Comparative Example 4 5.0 7.6 24 11.0 Comparative Example 5 5.0 7.9 23 13.8 Comparative Example 6 5.0 7.8 22 15.2 Comparative Example 7 3.8 7.8 25 9.0 Comparative Example 8 — 7.5 26 8.8 Comparative Example 9 — 8.5 20 18.5

[0095] 2. Salt adsorption performance test

[0096] Take 1g of the improved fertilizer sample and add 100mL of NaCl solution (Na + (Concentration 2000 mg / L), adsorption was shaken for 2 hours, and the Na+ concentration after adsorption was measured. + concentration.

[0097] Example 1 2000 620 69.0 Example 2 2000 710 64.5 Example 3 2000 580 71.0 Comparative Example 1 2000 890 55.5 Comparative Example 2 2000 850 57.5 Comparative Example 3 2000 780 61.0 Comparative Example 4 2000 820 59.0 Comparative Example 5 2000 860 57.0 Comparative Example 6 2000 880 56.0 Comparative Example 7 2000 640 68.0 Comparative Example 8 2000 635 68.3 Comparative Example 9 2000 1250 37.5

[0098] 3. Pot experiment (moderately saline-alkali soil)

[0099] Experimental soil: salinity 0.48%, pH 8.35, organic matter 8.2 g / kg. Experimental treatments: CK (no fertilizer applied), Examples 1-3, Comparative Examples 1-9, application rate 300 kg / mu. Crop planted: maize (60-day growing season).

[0100] Soil improvement effect (60 days after application)

[0101] CK 0.46 8.32 8.3 1.40 42.5 Example 1 0.19 7.58 15.2 1.16 53.8 Example 2 0.22 7.65 13.8 1.20 51.2 Example 3 0.16 7.52 16.5 1.13 55.6 Comparative Example 1 0.28 7.82 14.2 1.22 49.5 Comparative Example 2 0.26 7.78 14.5 1.24 48.8 Comparative Example 3 0.25 7.75 14.6 1.20 50.2 Comparative Example 4 0.27 7.80 14.3 1.23 49.0 Comparative Example 5 0.27 7.79 14.4 1.25 48.5 Comparative Example 6 0.28 7.81 14.2 1.26 48.0 Comparative Example 7 0.24 7.70 14.8 1.19 51.0 Comparative Example 8 0.25 7.72 14.5 1.18 51.5 Comparative Example 9 0.35 8.00 10.5 1.34 45.5

[0102] Corn growth indicators (harvest period)

[0103] CK 152 82.5 17.5 118.5 — Example 1 192 135.2 30.5 185.5 +56.5 Example 2 182 125.6 28.2 172.5 +45.6 Example 3 198 142.5 32.5 195.5 +65.0 Comparative Example 1 175 112.5 25.2 158.5 +33.8 Comparative Example 2 172 108.5 24.5 155.2 +31.0 Comparative Example 3 178 115.2 26.0 162.5 +37.1 Comparative Example 4 176 113.5 25.5 160.2 +35.2 Comparative Example 5 174 110.5 24.8 158.0 +33.3 Comparative Example 6 173 109.5 24.5 156.5 +32.1 Comparative Example 7 182 120.5 27.5 168.5 +42.2 Comparative Example 8 180 118.5 27.0 165.5 +39.7 Comparative Example 9 160 95.5 20.5 138.5 +16.9

[0104] 4. Field plot trials (in synergy with straw interlayer technology)

[0105] Experimental location: Severely saline-alkali land in the Yellow River Delta, with a salt content of 0.72%, pH 8.55, and organic matter content of 6.8 g / kg.

[0106] Experimental treatment:

[0107] Treatment A: Control (no improved fertilizer applied, no straw interlayer)

[0108] Treatment B: Apply improved fertilizer alone (Example 1, 400 kg / mu)

[0109] Treatment C: A separate straw layer is set up (burying depth 35cm, wheat straw 6t / mu, using soil lifting-laying-covering process).

[0110] Treatment D: Straw interlayer + improved fertilizer (straw interlayer + 400 kg / mu of improved fertilizer from Example 1) Crop: Cotton

[0111] A 48.5 62.5 7.5 4.5 58.5 — B 68.5 78.5 10.2 5.0 82.5 +41.0 C 65.2 75.2 9.5 4.9 76.5 +30.8 D 86.5 95.5 13.5 5.4 112.5 +92.3

[0112] Results Analysis

[0113] (1) Product performance: The viable bacteria content of Examples 1-3 reached 4.0-5.6×10 8 With a CFU / g and a particle disintegration rate of only 7.5-10.2%, which is better than Comparative Examples 2-6 and Comparative Example 9, it is demonstrated that the addition of filler significantly improves the structural stability and anti-disintegration ability of particles.

[0114] (2) Salt adsorption performance: Na in Examples 1-3 + The adsorption rate reached 64.5-71.0%, which was much higher than that of Comparative Example 9 (37.5%). Comparative Example 1 (without modified functional agent) had an adsorption rate of 55.5%, and Comparative Example 2 (without filler) had an adsorption rate of 57.5%, both of which were lower than that of Example 1 (69.0%), proving that both modified functional agent and filler make significant contributions to salt adsorption, and the synergistic effect of the two is the best.

[0115] (3) Soil improvement effect: After application in Examples 1-3, the soil salinity decreased to 0.16-0.22%, the pH decreased to 7.52-7.65, the organic matter increased to 13.8-16.5 g / kg, the bulk density decreased to 1.13-1.20 g / cm³, and the porosity increased to 51.2-55.6%. All indicators were significantly better than those in the comparative example. This proves that the fertilizer of this invention has a comprehensive improvement effect on saline-alkali soil.

[0116] (4) In terms of crop yield increase: In the pot experiment, the yield increase rate of Examples 1-3 reached 45.6-65.0%, which was much higher than that of Comparative Example 9 (16.9%). In the field synergistic experiment, the yield increase rate of the "straw interlayer + improved fertilizer" treatment reached 92.3%, which was significantly better than the application of improved fertilizer alone (41.0%) and the setting of straw interlayer alone (30.8%), proving that straw interlayer and improved fertilizer have a significant synergistic effect.

[0117] (5) Component synergistic effect analysis: Comparative examples 1-6 verified that each component of the modified functional agent and the filler is indispensable; comparative examples 7-8 verified the importance of the compound microbial agent, especially halophilic and alkaliphilic bacteria.

[0118] In summary, this invention, through the synergistic compounding of modified functional agents, fillers, and organic-inorganic components, combined with straw interlayer technology, forms a four-in-one comprehensive improvement system for saline-alkali land. All performance indicators are excellent, demonstrating outstanding creativity and practicality.

[0119] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0120] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An organic-inorganic compound fertilizer for improving saline-alkali land, characterized in that, The raw materials, by weight, include: 25-40 parts straw biochar, 15-25 parts humic acid, 20-35 parts organic fertilizer, 10-20 parts desulfurized gypsum, 5-12 parts sulfur, 3-8 parts superphosphate, 2-6 parts ferrous sulfate, 4-10 parts modified functional agent, 6-12 parts filler, 2-5 parts compound microbial agent, and 3-6 parts binder.

2. The organic-inorganic compound saline-alkali land improvement fertilizer according to claim 1, characterized in that, The preparation method of the modified functional agent is as follows: S201: Mix nano zeolite and nano sepiolite in a weight ratio of (3-5):(1-2), add 3-5 times the mass of deionized water, and ultrasonically disperse for 30-60 min to obtain a mixed mineral dispersion. S202: Add 5-10% of polydimethyldiallylammonium chloride and 3-6% of chitosan by total mineral mass to the mixed mineral dispersion, and stir at 400-600 r / min for 2-3 h at 40-60℃. S203: After the reaction is complete, filter and wash, dry at 80-100℃ for 4-6 hours, grind through a 200-300 mesh sieve to obtain the modified functional agent.

3. The organic-inorganic compound saline-alkali land improvement fertilizer according to claim 2, characterized in that, The nano-zeolite has a particle size of 50-150 nm, a silicon-to-aluminum ratio of 2-5, and a specific surface area ≥300 m² / g; the nano-sepiolite has a fiber length of 200-500 nm, a diameter of 10-30 nm, and a specific surface area ≥200 m² / g; the chitosan has a degree of deacetylation ≥90% and a molecular weight of 50,000-200,000.

4. The organic-inorganic compound saline-alkali land improvement fertilizer according to claim 1, characterized in that, The preparation method of the filler is as follows: S301: Mix diatomaceous earth and vermiculite in a weight ratio of (5-8):(3-5) and calcine at 300-500℃ for 1-2 hours to obtain an activated composite carrier; S302: Add the activated composite carrier to a 3-8% (w / w) polyvinyl alcohol solution, soak for 2-4 hours, filter, and dry at 60-80℃ to obtain the polymer-modified carrier; S303: Mix the polymer-modified carrier with sodium carboxymethyl cellulose at a weight ratio of (8-12):1, add 5-10% glycerol of the total carrier mass, spray wet, granulate, and pass through a 20-60 mesh sieve to obtain the filler.

5. The organic-inorganic compound saline-alkali land improvement fertilizer according to claim 4, characterized in that, The diatomaceous earth has a silica content of ≥75% and a specific surface area of ​​≥50m² / g; the vermiculite has an expansion ratio of ≥8 times and a cation exchange capacity of ≥100cmol / kg; the polyvinyl alcohol has a degree of alcoholysis of 85-99% and a molecular weight of 5000-20000.

6. The organic-inorganic compound saline-alkali land improvement fertilizer according to claim 1, characterized in that, The method for preparing the straw biochar is as follows: crop straw is pyrolyzed at 400-500℃ under limited oxygen for 2-4 hours and then crushed and passed through a 40-80 mesh sieve; the humic acid is mineral-derived humic acid with a humic acid content ≥50%; the organic fertilizer is prepared by composting and fermenting cow and sheep manure and earthworm castings with an organic matter content ≥45%.

7. The organic-inorganic compound saline-alkali land improvement fertilizer according to claim 1, characterized in that, The preparation method of the compound microbial agent is as follows: S501: *Bacillus amyloliquefaciens*, *Bacillus subtilis*, *Bacillus megaterium*, *Bacillus mucilaginosus*, *Bacillus licheniformis*, and *Bacillus halophilicus* are cultured separately in a liquid submerged fermentation process, with a viable cell count ≥10⁻⁶ in the fermentation broth. 9 CFU / mL, add 1-2% NaCl to the fermentation medium for each strain; S502: Mix the fermentation broths of each strain in a weight ratio of (2-3):(1.5-2.5):(1-2):(1-1.5):(0.8-1.5):(0.5-1), add 10-20% corn starch and 5-10% trehalose of the total fermentation broth, and spray dry to obtain a compound microbial powder with a viable cell content ≥5×10¹. 0 CFU / g.

8. The organic-inorganic compound saline-alkali land improvement fertilizer according to claim 1, characterized in that, The binder is at least one of bentonite, starch, and polyacrylamide; the desulfurized gypsum is a byproduct of flue gas desulfurization and has a calcium sulfate dihydrate content of ≥85%; the sulfur is industrial sulfur powder with a sulfur content of ≥99%.

9. A method for preparing an organic-inorganic compound saline-alkali land improvement fertilizer as described in any one of claims 1-8, characterized in that, Includes the following steps: S601: Desulfurized gypsum, sulfur, superphosphate, and ferrous sulfate are separately pulverized and passed through a 60-100 mesh sieve, then mixed evenly according to the specified ratio to obtain an inorganic mixture. S602: Mix straw biochar, humic acid, and organic fertilizer according to the specified ratio, pulverize and pass through a 40-60 mesh sieve, and mix evenly to obtain an organic mixture. S603: Mix the modified functional agent and the filler, and stir at 200-300 r / min for 10-20 min to obtain the functional-filler premix. S604: Add the inorganic mixture, organic mixture and functional premix to the mixer and stir for 15-30 minutes to obtain the main mixture; S605: Mix the compound microbial agent and binder evenly, add them to the main mixture, and continue stirring for 10-20 minutes to obtain the improved fertilizer mixture; S606: The improved fertilizer mixture is granulated by extrusion or disc granulation, with a particle size of 3-8 mm and a granulation pressure of 15-25 MPa. S607: Dry the granules at a low temperature of 40-55℃, control the moisture content to ≤10%, and then sieve and classify them; S608: Vacuum packaging yields an organic-inorganic compound fertilizer for improving saline-alkali land.