A humic acid organic-inorganic compound fertilizer for slow release and improving fertilizer utilization rate and a preparation method thereof

Abstract

The application belongs to the technical field of fertilizers, and particularly relates to a humic acid organic-inorganic compound fertilizer with slow release and improved fertilizer utilization rate and a preparation method thereof. The humic acid organic-inorganic compound fertilizer comprises the following raw materials in parts by weight: 22-30 parts of biogas residue, 35-55 parts of humic acid, 8-13 parts of fine columnar algae powder, 5-8 parts of urea, 12-17 parts of ammonium sulfate, 12-15 parts of superphosphoric acid calcium, 15-20 parts of potassium sulfate and 10-15 parts of slow release coating suspension. Test results show that the humic acid organic-inorganic compound fertilizer with slow release and improved fertilizer utilization rate prepared by the application can reduce the nitrogen and phosphorus release rates of the humic acid inorganic compound fertilizer, has better slow release effect, significantly promotes the plant height, stem diameter and root length of soybeans and corn, has obvious growth promotion effect, and has wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of fertilizer technology, specifically relating to a slow-release humic acid organic-inorganic compound fertilizer that improves fertilizer utilization and its preparation method. Background Technology

[0002] Humic acid, a widely available natural organic polymer mixture (such as weathered coal and lignite), exhibits enormous application potential in agriculture due to its unique structural properties. Studies have shown that humic acid can improve soil aggregate structure, regulate pH balance, activate microbial activity, and enhance soil nutrient availability through integration or activation. Therefore, using humic acid as a synergist to prepare humic acid-enhanced fertilizers has become an important technological direction for achieving increased crop yields, improved quality, and soil improvement.

[0003] Organic-inorganic compound fertilizers combine the advantages of both organic and inorganic fertilizers, providing readily available nutrients while improving soil and extending fertilizer effectiveness through organic matter. This represents a sustainable fertilization approach suited to my country's national conditions. However, conventional organic-inorganic compound fertilizers still suffer from a mismatch between nutrient release rates and long-term crop needs, potentially leading to early nutrient loss or insufficient later supply, thus limiting further improvement in their effectiveness. Slow-release fertilizers, through coating and other technologies, control nutrient release, more precisely meeting the needs of crops throughout their entire growth cycle and improving fertilizer utilization. However, traditional slow-release materials have potential environmental impacts and relatively limited functionality, with limited soil improvement effects.

[0004] In summary, how to efficiently, cost-effectively, and environmentally friendly combine the soil-improving and growth-promoting functions of humic acid, the all-around nutritional characteristics of organic-inorganic compound fertilizers, and the controlled-release advantages of slow-release technology to develop a new type of fertilizer that can intelligently control release, improve utilization, and actively improve soil is a technical problem that urgently needs to be solved in the fertilizer field. Summary of the Invention

[0005] The primary objective of this invention is to provide a slow-release humic acid organic-inorganic compound fertilizer that improves fertilizer utilization.

[0006] The second objective of this invention is to provide a method for preparing a slow-release humic acid organic-inorganic compound fertilizer that improves fertilizer utilization.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A slow-release humic acid organic-inorganic compound fertilizer for improving fertilizer utilization comprises the following raw materials in parts by weight: 22-30 parts of biogas residue, 35-55 parts of humic acid, 8-13 parts of fine columnar algae powder, 5-8 parts of urea, 12-17 parts of ammonium sulfate, 12-15 parts of superphosphate, 15-20 parts of potassium sulfate, and 10-15 parts of slow-release coated suspension.

[0008] Furthermore, the sustained-release coated suspension is a modified sodium-based montmorillonite suspension.

[0009] Furthermore, the method for preparing the sustained-release coated suspension is as follows: A. Sodium-based montmorillonite is ultrasonically dispersed in deionized water, magnetically stirred for 1-3 hours, and allowed to stand to obtain a montmorillonite suspension. The temperature is raised to 70-80℃, and hexadecanoic acid propyltrimethylammonium chloride is slowly added dropwise, along with the intercalation aid isopropanol. The reaction time is 1-3 hours to obtain a pretreated sodium-based montmorillonite mixture. B. Under a nitrogen atmosphere, the pretreated sodium-based montmorillonite mixture obtained in step A is cooled to 60-70°C, N-vinyl isobutyramide and anhydrous ethanol are added, and AIBN initiator is added. The reaction time is 4-6 hours to obtain the product. C. The product obtained in step B is washed with anhydrous ethanol, centrifuged, filtered, dried, ground, and passed through a 200-300 mesh sieve. The modified sodium montmorillonite is then ultrasonically dispersed in deionized water for 0.5-1 hour to obtain a sustained-release coated suspension.

[0010] Further, in step A, the mass ratio of isopropanol, sodium montmorillonite, hexadecanoic acid propyltrimethylammonium chloride, and deionized water is 1:(10-15):(2-3):(150-200).

[0011] Further, in step B, the mass ratio of the pretreated sodium montmorillonite mixture, N-vinyl isobutyramide, AIBN, and anhydrous ethanol is 1:(0.1-0.3):(0.02-0.05):(5-10).

[0012] Further, in step C, the mass ratio of modified sodium-based montmorillonite to deionized water is 1:(10-15).

[0013] Furthermore, the specific steps for preparing humic acid are as follows: S1 Dry weathered coal is pulverized to 60-80 mesh and roasted in an oxygen-free environment at 300-400℃, followed by oxidative roasting at 150-300℃ to obtain the calcined product; S2 The calcined product obtained in step S1 is mixed with a NaOH alkaline solution with a concentration of 4-6 w / v% at a solid-liquid ratio of 1g:(7-9)mL, and reacted at 80-100℃ for 2-3h to obtain a mixture; S3 Centrifuge the mixture obtained in step S2, collect the supernatant, and dry it to obtain the final product.

[0014] The preparation method of the slow-release humic acid organic-inorganic compound fertilizer with improved fertilizer utilization rate as described above includes the following steps: (1) Dry, crush, and sieve the biogas residue; (2) Weigh out the biogas residue, humic acid, fine columnar algae powder, urea, ammonium sulfate, superphosphate and potassium sulfate according to the weight parts, mix them to obtain a mixture, mix with hot water and granulate to obtain coarse compound fertilizer; (3) Spray the crude compound fertilizer prepared in step (2) with a slow-release coating suspension, and dry it to obtain a slow-release humic acid organic-inorganic compound fertilizer that improves fertilizer utilization.

[0015] Furthermore, the mesh size of the sieve in step (1) is 80-100.

[0016] Furthermore, in step (2), the amount of hot water added is 0.2-0.25 times the total weight of the mixture; the temperature of the hot water is 50-80℃.

[0017] Compared with the prior art, the main advantages of the present invention are as follows: 1. Significant improvement in humic acid activity and fertilizer efficiency: This invention thermally activates weathered coal through two-step roasting with oxygen isolation and oxidation, breaking its stable structure and creating active sites; then, humic acid is efficiently dissolved and modified through alkaline treatment, ultimately forming a humic acid product with both high activity and slow-release function, which significantly improves its fertilizer efficiency and soil adaptability.

[0018] 2. A two-step modification method was used to successfully construct a slow-release structure with dual hydrophobic barriers. First, sodium-based montmorillonite was pretreated with hexadecanoic acid propyltrimethylammonium chloride, which inserted long-chain alkyl groups into the interlayer of montmorillonite, significantly expanding the interlayer spacing and forming a hydrophobic barrier formed by the arrangement of alkyl chains. Subsequently, in-situ graft polymerization of N-vinyl isobutyramide into the interlayer of the pretreated montmorillonite further stabilized the interlayer structure and introduced a hydrophobic polymer backbone, forming a second, more stable hydrophobic barrier. The synergistic effect of these two barriers significantly prolonged the diffusion path of water molecules and nutrient ions within the coating layer, effectively inhibiting the rate of soil moisture penetration into the fertilizer particles. Ultimately, this structure significantly delayed the rapid dissolution and loss of nutrients, achieving a stable and long-lasting slow-release effect.

[0019] 3. This coating system achieves functional enhancement and environmental friendliness through a multi-mechanism synergy: First, the amide groups on the polymer chain can form strong hydrogen bonds with humic acid, significantly enhancing the flexibility, wear resistance, and adhesion to compound fertilizers of the coating layer, preventing peeling and cracking. Second, the N-vinyl isobutyramide used as a thermosensitive monomer modifier enables the coating layer to respond to diurnal temperature variations, actively regulating nutrient flux and forming an intelligent release rhythm of "slow release during the day and micro-release at night." Finally, the added fine columnar algae powder, with its nanoporous silica cell wall structure, forms a nanoscale porous structure that can specifically adsorb urea and ammonium ions, reducing nitrogen loss. Simultaneously, the released silicon element, after being absorbed by the crop, strengthens the cell wall structure, synergistically enhancing the crop's stress resistance and disease and pest resistance.

[0020] 4. Experimental results show that the humic acid organic-inorganic compound fertilizer prepared in this invention, by adding fine columnar algae powder and slow-release coating suspension, can reduce the initial release rate of nitrogen and phosphorus nutrients in the product, prolong the nutrient supply period, and has a significant slow-release effect; it also increases the plant height, stem diameter, and root length of soybeans and corn, exhibiting a significant growth-promoting effect. These results verify the comprehensive advantages of the humic acid organic-inorganic compound fertilizer in promoting crop growth and improving fertilizer utilization. Attached Figure Description

[0021] Figure 1 This is a scanning electron microscope image of the modified sodium-based montmorillonite prepared in Example 1 of the present invention; Figure 2 This refers to a slow-release humic acid organic-inorganic compound fertilizer that improves fertilizer utilization by reducing nitrogen release rate. Figure 3 This is a slow-release humic acid organic-inorganic compound fertilizer that improves fertilizer utilization by reducing phosphorus release rate. Detailed Implementation

[0022] 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.

[0023] The preparation method of humic acid used in the embodiments of the present invention is as follows: S1 Dry weathered coal is pulverized to 70 mesh and roasted in an oxygen-free environment at 350℃, followed by oxidative roasting at 220℃ to obtain the calcined product; S2 The calcined product obtained in step S1 is mixed with a 5 w / v% NaOH alkaline solution at a solid-liquid ratio of 1 g: 8 mL, and reacted at 90 °C for 3 h to obtain a mixture; S3 Centrifuge the mixture obtained in step S2, collect the supernatant, and dry it to obtain the final product.

[0024] The preparation method of the fine columnar algae powder used in the embodiments of the present invention is as follows: (1) Take seawater pre-filtered through a 20 μm sieve, add nutrients according to the f / 2 medium formula, and prepare f / 2 medium. Inoculate with logarithmic growth phase *Cyclocarya paliurus* seed culture at an inoculation rate of 5 v / v % and incubate at 20 ℃, with a light-dark cycle of 12 h:12 h and a light intensity of 60 μmol photons m -2 s -1 Under the specified conditions, the algal solution was cultured for 7 days, and then concentrated under reduced pressure using a 0.22 μm microporous membrane to obtain a concentrated solution.

[0025] (2) Centrifuge the concentrated solution obtained in step (1) at 4 °C at 8000 × g for 10 minutes and collect the algal mud. Pre-freeze the algal mud in an ultra-low temperature freezer at -80 °C, freeze-dry it, grind it through a 200-mesh sieve to obtain algal powder with a water content ≤5 w / w%, and store it at -20 °C in the dark.

[0026] Example 1 A slow-release humic acid organic-inorganic compound fertilizer for improving fertilizer utilization comprises the following raw materials in parts by weight: 26 parts biogas residue, 45 parts humic acid, 10 parts fine columnar algae powder, 6 parts urea, 14 parts ammonium sulfate, 14 parts superphosphate, 17 parts potassium sulfate, and 12 parts slow-release coated suspension.

[0027] A method for preparing a slow-release humic acid organic-inorganic compound fertilizer to improve fertilizer utilization includes the following steps: (1) Dry, crush, and pass the biogas residue through a 90-mesh sieve; (2) Weigh 26 parts of biogas residue, 45 parts of humic acid, 10 parts of fine column algae powder, 6 parts of urea, 14 parts of ammonium sulfate, 14 parts of superphosphate and 17 parts of potassium sulfate according to the weight ratio, mix them to obtain a mixture, then mix it with hot water at 65°C and put it into a granulator for granulation to obtain a coarse compound fertilizer; the amount of hot water added is 0.22 times the total weight of the mixture.

[0028] (3) Place the crude compound fertilizer prepared in step (2) into a drum, spray 12 parts of modified sodium montmorillonite suspension evenly with a spray gun, and then dry it to obtain a slow-release humic acid organic-inorganic compound fertilizer that improves fertilizer utilization.

[0029] The method for preparing the sustained-release coated suspension includes the following steps: A. Sodium-based montmorillonite was ultrasonically dispersed in deionized water and magnetically stirred for 2 hours. The mixture was then allowed to stand to obtain a montmorillonite suspension. The suspension was heated to 75°C, and hexadecanoic acid-propyltrimethylammonium chloride was slowly added dropwise, along with the intercalation aid isopropanol. The reaction time was 2 hours to obtain a pretreated sodium-based montmorillonite mixture. The mass ratio of isopropanol, sodium-based montmorillonite, hexadecanoic acid-propyltrimethylammonium chloride, and deionized water was 1:12:2:175.

[0030] B. Under a nitrogen atmosphere, the pretreated sodium-based montmorillonite mixture obtained in step A was cooled to 65°C, N-vinyl isobutyramide, anhydrous ethanol, and AIBN initiator were added. The reaction time was 5 hours to obtain the product. The mass ratio of the pretreated sodium-based montmorillonite mixture, N-vinyl isobutyramide, AIBN, and anhydrous ethanol was 1:0.2:0.03:7.

[0031] C. The product obtained in step B was washed with anhydrous ethanol, centrifuged, filtered, dried, ground, and passed through a 250-mesh sieve to obtain modified sodium montmorillonite. This modified sodium montmorillonite was ultrasonically dispersed in deionized water for 0.7 hours to obtain a sustained-release coated suspension. The mass ratio of modified sodium montmorillonite to deionized water was 1:12. The microstructure of the modified sodium montmorillonite was characterized using scanning electron microscopy, and the results are as follows: Figure 1 As shown.

[0032] Example 2 A slow-release humic acid organic-inorganic compound fertilizer for improving fertilizer utilization comprises the following raw materials in parts by weight: 22 parts biogas residue, 35 parts humic acid, 8 parts fine columnar algae powder, 5 parts urea, 12 parts ammonium sulfate, 12 parts superphosphate, 15 parts potassium sulfate, and 10 parts slow-release coated suspension.

[0033] A method for preparing a slow-release humic acid organic-inorganic compound fertilizer to improve fertilizer utilization includes the following steps: (1) Dry, crush, and pass the biogas residue through an 80-mesh sieve; (2) Weigh 22 parts of biogas residue, 35 parts of humic acid, 8 parts of fine column algae powder, 5 parts of urea, 12 parts of ammonium sulfate, 12 parts of superphosphate and 15 parts of potassium sulfate according to the weight ratio, mix them to obtain a mixture, then mix it with hot water at 50°C and put it into a granulator for granulation to obtain a coarse compound fertilizer; the amount of hot water added is 0.2 times the total weight of the mixture.

[0034] (3) Spray 10 portions of the modified sodium-based montmorillonite suspension obtained in step (2) with the crude compound fertilizer, dry it, and obtain a slow-release humic acid organic-inorganic compound fertilizer that improves fertilizer utilization.

[0035] The method for preparing the sustained-release coated suspension includes the following steps: A. Sodium-based montmorillonite was ultrasonically dispersed in deionized water and magnetically stirred for 1 hour. The mixture was then allowed to stand to obtain a montmorillonite suspension. The suspension was heated to 70°C, and hexadecanoic acid-propyltrimethylammonium chloride was slowly added dropwise, along with the intercalation aid isopropanol. The reaction time was 1 hour to obtain a pretreated sodium-based montmorillonite mixture. The mass ratio of isopropanol, sodium-based montmorillonite, hexadecanoic acid-propyltrimethylammonium chloride, and deionized water was 1:10:2:150.

[0036] B. Under a nitrogen atmosphere, the pretreated sodium-based montmorillonite mixture obtained in step A was cooled to 60°C, N-vinyl isobutyramide, anhydrous ethanol, and AIBN initiator were added. The reaction time was 4 hours to obtain the product. The mass ratio of the pretreated sodium-based montmorillonite mixture, N-vinyl isobutyramide, AIBN, and anhydrous ethanol was 1:0.1:0.02:5.

[0037] C. The product obtained in step B is washed with anhydrous ethanol, centrifuged, filtered, dried, ground, and passed through a 200-mesh sieve. The resulting modified sodium montmorillonite is ultrasonically dispersed in deionized water for 0.5 hours to obtain a slow-release coated suspension. The mass ratio of the modified sodium montmorillonite to deionized water is 1:10.

[0038] Example 3 A slow-release humic acid organic-inorganic compound fertilizer for improving fertilizer utilization comprises the following raw materials in parts by weight: 30 parts biogas residue, 55 parts humic acid, 13 parts fine columnar algae powder, 8 parts urea, 17 parts ammonium sulfate, 15 parts superphosphate, 20 parts potassium sulfate, and 15 parts slow-release coated suspension.

[0039] A method for preparing a slow-release humic acid organic-inorganic compound fertilizer to improve fertilizer utilization includes the following steps: (1) Dry, crush, and pass the biogas residue through a 100-mesh sieve; (2) Weigh out 30 parts of biogas residue, 55 parts of humic acid, 13 parts of fine column algae powder, 8 parts of urea, 17 parts of ammonium sulfate, 15 parts of superphosphate and 20 parts of potassium sulfate according to the weight ratio, mix them to obtain a mixture, then mix it with hot water at 80°C and put it into a granulator for granulation to obtain coarse compound fertilizer; the amount of hot water added is 0.25 times the total weight of the mixture.

[0040] (3) Spray 15 portions of the modified sodium-based montmorillonite suspension obtained in step (2) with the crude compound fertilizer, dry it, and obtain a slow-release humic acid organic-inorganic compound fertilizer that improves fertilizer utilization.

[0041] The method for preparing the sustained-release coated suspension includes the following steps: A. Sodium-based montmorillonite was ultrasonically dispersed in deionized water and magnetically stirred for 3 hours. After standing, a montmorillonite suspension was obtained. The suspension was heated to 80°C, and hexadecanoic acid propyltrimethylammonium chloride was slowly added dropwise, along with the intercalation aid isopropanol. The reaction time was 3 hours to obtain a pretreated sodium-based montmorillonite mixture. The mass ratio of isopropanol, sodium-based montmorillonite, hexadecanoic acid propyltrimethylammonium chloride, and deionized water was 1:15:3:200.

[0042] B. Under a nitrogen atmosphere, the pretreated sodium-based montmorillonite mixture obtained in step A was cooled to 70°C, N-vinyl isobutyramide, anhydrous ethanol, and AIBN initiator were added. The reaction time was 6 hours to obtain the product. The mass ratio of the pretreated sodium-based montmorillonite mixture, N-vinyl isobutyramide, AIBN, and anhydrous ethanol was 1:0.3:0.05:10.

[0043] C. The product obtained in step B is washed with anhydrous ethanol, centrifuged, filtered, dried, ground, and passed through a 300-mesh sieve. The resulting modified sodium montmorillonite is ultrasonically dispersed in deionized water for 1 hour to obtain a slow-release coated suspension. The mass ratio of the modified sodium montmorillonite to deionized water is 1:15.

[0044] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the modified sodium montmorillonite in step C is replaced with sodium montmorillonite, while all other aspects are the same as in Example 1.

[0045] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the fine columnar algae powder in the humic acid organic-inorganic compound fertilizer is omitted, while all other aspects are the same as in Example 1.

[0046] Experimental Example 1 Determination of the slow-release properties of a humic acid-based organic-inorganic compound fertilizer to improve fertilizer utilization. The release dynamics of nitrogen and phosphorus nutrients in the humic acid organic-inorganic compound fertilizer prepared according to this invention were determined using the static immersion method to evaluate its slow-release performance. The specific experimental steps are as follows: Weigh 1.0 g each of the humic acid organic-inorganic compound fertilizers prepared in Examples 1-3, Comparative Example 1, and Comparative Example 2, and place them in Erlenmeyer flasks. Add 400 mL of deionized water. Place the Erlenmeyer flasks in a 25°C constant temperature water bath shaker for 50 h. Samples were taken at 0 h, 4 h, 8 h, 10 h, 15 h, 20 h, and 50 h. After each sampling, the sample was centrifuged at 4000 r / min for 5 min, and the supernatant was filtered through a 0.45 μm aqueous filter membrane. The concentrations of total nitrogen and total phosphorus in the filtrate were determined using the standard method in "Methods for Monitoring and Analysis of Water and Wastewater". Each treatment was repeated three times. The dynamic curves of the cumulative release rate of nitrogen and phosphorus are shown below. Figure 2 and Figure 3 As shown.

[0047] The results are as follows Figure 2 , Figure 3 The figures show the nitrogen and phosphorus release rates of a slow-release humic acid organic-inorganic compound fertilizer to improve fertilizer utilization. As can be seen from the figures, compared with the control group, Comparative Example 1, and Comparative Example 2, the nitrogen and phosphorus release rates of the humic acid organic-inorganic compound fertilizers prepared in Examples 1-3 of this invention are significantly reduced. This indicates that the humic acid organic-inorganic compound fertilizers prepared in Examples 1-3 of this invention release nitrogen and phosphorus elements at a slower rate within 50 hours, exhibiting a better slow-release effect.

[0048] Experimental Example 2 Determination of the growth-promoting effect of a slow-release humic acid organic-inorganic compound fertilizer that improves fertilizer utilization. To investigate the effects of a slow-release humic acid organic-inorganic compound fertilizer prepared in this invention, which improves fertilizer utilization, on the growth of soybeans and corn, pot experiments were conducted to evaluate its growth-promoting effects on plant height, stem diameter, and root length. The specific experimental steps are as follows: The soil used in the experiment was nutrient soil, with 2 kg of soil per pot. The tested crops were soybean and corn, and both crops were divided into 6 groups: Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Control Group, with three replicates for each group. The humic acid organic-inorganic compound fertilizer prepared in Examples 1-3 and Comparative Examples 1-2 was applied at 1.5 g / pot, while the control group received no fertilization treatment. All potted plants were placed in a greenhouse and managed uniformly for 30 days. The measured indicators included plant height (cm), stem diameter (mm), and root length (cm), and the specific results are shown in Tables 1 and 2.

[0049] Table 1. Growth-promoting effects of humic acid-organic-inorganic compound fertilizer on corn. Table 2. Growth-promoting effects of humic acid-organic-inorganic compound fertilizer on soybeans. The results are shown in Table 1, which illustrates the growth-promoting effect of humic acid organic-inorganic compound fertilizer on maize. As shown in Table 1, compared with the control group, Comparative Example 1, and Comparative Example 2, the humic acid organic-inorganic compound fertilizer prepared in Examples 1-3 of this invention significantly increased maize plant height, stem diameter, and root length. This indicates that the humic acid organic-inorganic compound fertilizer prepared in Examples 1-3 of this invention has a significant growth-promoting effect on maize, verifying the significant advantages of this fertilizer in promoting crop growth and improving fertilizer utilization.

[0050] The results are shown in Table 2, which illustrates the growth-promoting effect of humic acid organic-inorganic compound fertilizer on soybeans. As can be seen from Table 2, compared with the control group, Comparative Example 1, and Comparative Example 2, the humic acid organic-inorganic compound fertilizer prepared in Examples 1-3 of this invention significantly increased soybean plant height, stem diameter, and root length. This indicates that the humic acid organic-inorganic compound fertilizer prepared in Examples 1-3 of this invention has a significant growth-promoting effect on soybeans, verifying the significant advantages of this fertilizer in promoting crop growth and improving fertilizer utilization.

[0051] 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 slow-release humic acid organic-inorganic compound fertilizer that improves fertilizer utilization, characterized in that, The raw materials contain the following parts by weight: 22-30 parts biogas residue, 35-55 parts humic acid, 8-13 parts fine columnar algae powder, 5-8 parts urea, 12-17 parts ammonium sulfate, 12-15 parts superphosphate, 15-20 parts potassium sulfate, and 10-15 parts slow-release coated suspension.

2. The slow-release humic acid organic-inorganic compound fertilizer for improving fertilizer utilization according to claim 1, characterized in that, The sustained-release coated suspension is a modified sodium-based montmorillonite suspension.

3. The slow-release humic acid organic-inorganic compound fertilizer for improving fertilizer utilization according to claim 2, characterized in that, The method for preparing the sustained-release coated suspension is as follows: A. Sodium-based montmorillonite is ultrasonically dispersed in deionized water, magnetically stirred for 1-3 hours, and allowed to stand to obtain a montmorillonite suspension. The temperature is raised to 70-80℃, and hexadecanoic acid propyltrimethylammonium chloride is slowly added dropwise, along with the intercalation aid isopropanol. The reaction time is 1-3 hours to obtain a pretreated sodium-based montmorillonite mixture. B. Under a nitrogen atmosphere, the pretreated sodium-based montmorillonite mixture obtained in step A is cooled to 60-70°C, N-vinyl isobutyramide and anhydrous ethanol are added, and AIBN initiator is added. The reaction time is 4-6 hours to obtain the product. C. The product obtained in step B is washed with anhydrous ethanol, centrifuged, filtered, dried, ground, and passed through a 200-300 mesh sieve. The modified sodium montmorillonite is then ultrasonically dispersed in deionized water for 0.5-1 hour to obtain a sustained-release coated suspension.

4. The slow-release humic acid organic-inorganic compound fertilizer for improving fertilizer utilization according to claim 3, characterized in that, In step A, the mass ratio of isopropanol, sodium montmorillonite, hexadecanoic acid propyltrimethylammonium chloride, and deionized water is 1:(10-15):(2-3):(150-200).

5. The slow-release humic acid organic-inorganic compound fertilizer for improving fertilizer utilization according to claim 3, characterized in that, In step B, the mass ratio of the pretreated sodium montmorillonite mixture, N-vinyl isobutyramide, AIBN, and anhydrous ethanol is 1:(0.1-0.3):(0.02-0.05):(5-10).

6. The slow-release humic acid organic-inorganic compound fertilizer for improving fertilizer utilization according to claim 3, characterized in that, In step C, the mass ratio of modified sodium-based montmorillonite to deionized water is 1:(10-15).

7. The slow-release humic acid organic-inorganic compound fertilizer for improving fertilizer utilization according to claim 1, characterized in that, The specific steps for preparing humic acid are as follows: S1 Dry weathered coal is pulverized to 60-80 mesh and roasted in an oxygen-free environment at 300-400℃, followed by oxidative roasting at 150-300℃ to obtain the calcined product; S2 The calcined product obtained in step S1 is mixed with a NaOH alkaline solution with a concentration of 4-6 w / v% at a solid-liquid ratio of 1g:(7-9)mL, and reacted at 80-100℃ for 2-3h to obtain a mixture; S3 Centrifuge the mixture obtained in step S2, collect the supernatant, and dry it to obtain the final product.

8. A method for preparing a slow-release humic acid organic-inorganic compound fertilizer with improved fertilizer utilization according to any one of claims 1-7, characterized in that, Includes the following steps: (1) Dry, crush, and sieve the biogas residue; (2) Weigh out the biogas residue, humic acid, fine columnar algae powder, urea, ammonium sulfate, superphosphate and potassium sulfate according to the weight parts, mix them to obtain a mixture, mix with hot water and granulate to obtain coarse compound fertilizer; (3) Spray the crude compound fertilizer prepared in step (2) with a slow-release coating suspension, and dry it to obtain a slow-release humic acid organic-inorganic compound fertilizer that improves fertilizer utilization.

9. The method for preparing a slow-release humic acid organic-inorganic compound fertilizer with improved fertilizer utilization rate according to claim 8, characterized in that, The mesh size of the sieve in step (1) is 80-100.

10. The method for preparing a slow-release humic acid organic-inorganic compound fertilizer with improved fertilizer utilization rate according to claim 8, characterized in that, In step (2), the amount of hot water added is 0.2-0.25 times the total weight of the mixture; the temperature of the hot water is 50-80℃.

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