Coated microbial fertilizer particle and preparation method thereof

Abstract

The invention relates to the technical field of microbial fertilizer preparation, and provides coated microbial fertilizer granules and a preparation method thereof in order to solve the problems that microbial fertilizer granules are short in storage time, loose in microbial agent, weak in compression resistance and the like, the coated fertilizer is composed of a microbial fertilizer granule core layer and a film layer coating the outer layer of the fertilizer, the mass ratio of the two components is 100: (0.5-10). Wherein the core layer can be made of trichoderma harzianum, penicillium baylii or aspergillus niger microbial fertilizer particles, and the film layer can be made of a mixture of polyvinyl alcohol (PVA) and hydrophilic materials capable of providing glycogen, such as starch, glucose, maltose, dextrin and the like. The coated microbial fertilizer disclosed by the invention has longer container life and stronger anti-pressure ability, the looseness problem is also greatly improved, the problems that traditional microbial fertilizer particles are easy to inactivate, easy to break, easy to loosen and the like are solved, and the coated microbial fertilizer has better popularization and application values.

Description

Technical Field

[0001] This invention relates to the field of microbial fertilizer preparation technology, and provides a coated microbial fertilizer granule and its preparation method. Background Technology

[0002] Microbial fertilizer granules are a type of fertilizer product that uses microbial agents as the core to enable crops to obtain specific fertilizer effects. As a low-cost and environmentally friendly new type of fertilizer, it can effectively improve soil, increase soil fertility, increase crop yield, and at the same time reduce crop losses caused by pathogens.

[0003] However, microbial granules generally suffer from problems such as short shelf life, poor pressure resistance, loose texture leading to powder shedding, and difficulty in being wetted by water. Firstly, after prolonged storage, the number of live bacteria in the microbial fertilizer granules significantly decreases, resulting in a marked decline in fertilization effectiveness. Secondly, microbial fertilizer granules generally have low pressure resistance and are easily broken by external forces, severely affecting their preparation, storage, and use. Furthermore, microbial fertilizer granules are very loose and prone to powder shedding. Finally, hydrophobic microbial fertilizer granules have poor affinity with aqueous solutions and are difficult to wet. Therefore, there is an urgent need for a coated microbial fertilizer granule to solve these technical problems. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a coated microbial granular fertilizer and its preparation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing coated microbial fertilizer, wherein the coated microbial fertilizer granules include a microbial fertilizer granule core layer and a membrane layer covering the fertilizer core, and the mass ratio of the fertilizer core to the membrane layer is 100:(0.5-10).

[0006] The microbial fertilizer granules are microbial fertilizer granules such as Trichoderma harzianum, Penicillium barometz, or Aspergillus niger.

[0007] The microbial fertilizer granules can also be microbial fertilizer granules obtained by mixing microbial agents such as Trichoderma harzianum, Penicillium barometz or Aspergillus niger with one or more carriers such as bentonite and diatomaceous earth. The number of live bacteria can be controlled by the weight ratio of microbial agents to carriers, ranging from about 100 million / g to 50 billion / g.

[0008] The membrane layer of the microbial fertilizer granules is a mixture of polyvinyl alcohol (PVA) and hydrophilic materials that can provide glycogen, such as starch, glucose, maltose and dextrin, with a mass ratio ranging from 9:1 to 1:9, preferably 7:3 to 3:7.

[0009] The membrane layer of the microbial fertilizer granules is a mixture of PVA and hydrophilic materials that can provide glycogen, such as starch, glucose, maltose, and dextrin. The selection criteria are as follows: materials such as starch, glucose, maltose, and dextrin have advantages such as low cost and renewability, and can provide nutrients for the germination and growth of microbial agents when used as a coating membrane for microbial fertilizers. However, their low viscosity and poor film-forming properties make them difficult to use alone. PVA has excellent film-forming ability and can be used to modify sugar raw materials. It has been reported that the PVA / glycogen composite system has excellent water absorption, mechanical properties, and biodegradability; therefore, the PVA / glycogen system can serve as the outer shell membrane of microbial fertilizers.

[0010] The coating process of the microbial fertilizer granules includes the following steps, taking PVA / starch coated microbial fertilizer granules as an example: Step 1—Preparing an aqueous solution of PVA: Add PVA to deionized water and stir continuously at 300 r / min for 2 hours at 105℃ until it is completely dissolved to form a transparent and homogeneous PVA solution. Step 2—Preparing a soluble starch solution: Mix soluble starch with deionized water and stir at 300 r / min for 10 minutes at a constant temperature of 75℃ to fully gelatinize the starch and form a transparent solution; Step 3—Preparing the PVA / starch mixed solution: Mix the two solutions in a predetermined ratio, place them in a 75°C water bath, and stir at 600 r / min for 30 minutes to ensure thorough mixing. Transfer the mixed solution to an ultrasonic cleaner and sonicate for 15 minutes to completely remove air bubbles from the solution, obtaining a clear coating solution for later use. Step 4—Preparation of Coated Microbial Fertilizer Granules: Using a coating machine, the prepared mixed solution is evenly sprayed onto the surface of the microbial fertilizer granules, controlling the spraying rate to ensure complete coverage. The coated granules are dried at a temperature ≤90℃ (preferably ≤40℃) to obtain the final coated microbial fertilizer product.

[0011] Advantages of the product of this invention: 1. The coating effectively isolates microbial fertilizer particles from the external environment. In particular, its excellent oxygen barrier properties significantly reduce the probability of microbial germination during storage, decrease the number of dead microorganisms, and thus extend the product's shelf life. Simultaneously, once the fertilizer is applied to the soil, the coating can be naturally degraded by soil microorganisms and moisture. During degradation, the sugars produced by the decomposition of the coating material provide nutrients for the microorganisms, promoting their germination and growth. This characteristic ensures storage stability without affecting the fertilizer's effectiveness in the soil, and may even enhance its fertilizing effect.

[0012] 2. The PVA / glycogen composite coating film has good flexibility and can absorb external pressure through elastic deformation, significantly improving the compression resistance of microbial fertilizer granules and preventing them from breaking or loosening during transportation or use. In addition, the complete coating structure can tightly wrap the microbial agent, effectively reducing the "powdering" phenomenon of fertilizer granules.

[0013] 3. The hydrophilic outer coating overcomes the problem that hydrophobic microbial fertilizers are difficult to wet quickly in water. The coated microbial fertilizers are more easily wetted by water, which is very helpful in improving their germination and survival rate in the soil. Attached Figure Description

[0014] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration: Figure 1 These are optical photographs of the coated microbial fertilizer prepared in Example 1 before and after being pressed with weights; Figure 2 These are optical photographs of the coated microbial fertilizer prepared in Example 2 before and after being pressed with weights; Figure 3 These are optical photographs of the coated microbial fertilizer prepared in Example 3 before and after being pressed with weights; Figure 4 These are optical photographs of the microbial fertilizer in Comparative Example 1 before and after being pressed by weights; Figure 5 These are optical photographs of the microbial fertilizer in Comparative Example 2 before and after being pressed by weights; Figure 6 These are optical photographs of the microbial fertilizer in Comparative Example 3 before and after being pressed by weights. Example 1

[0015] Prepare a 10% PVA solution by adding PVA to deionized water and stirring continuously at 300 rpm for 2 hours at 105°C until completely dissolved to form a transparent and homogeneous PVA solution. Prepare a 10% soluble starch solution by mixing soluble starch with deionized water and stirring at 300 rpm for 10 minutes at a constant temperature of 75°C to fully gelatinize the starch and form a transparent solution. Prepare a PVA / starch mixed solution by mixing the two solutions in a 1:1 ratio and placing them in a 75°C water bath. Stir at 600 rpm for 30 minutes to ensure thorough mixing. Transfer the mixed solution to an ultrasonic cleaner and sonicate for 15 minutes to completely remove air bubbles, obtaining a clear coating solution for later use. Using a coating machine, uniformly spray the prepared mixed solution onto the surface of Harz raspberry microbial fertilizer granules with bentonite as the "carrier," controlling the spraying rate to ensure complete coverage of the coating layer. The coated granules are dried at a temperature ≤40℃ to obtain the final coated microbial fertilizer product. Example 2

[0016] Prepare a 10% PVA solution by adding PVA to deionized water and stirring continuously at 300 rpm for 2 hours at 105°C until completely dissolved to form a transparent and homogeneous PVA solution. Prepare a 10% soluble starch solution by mixing soluble starch with deionized water and stirring at 300 rpm for 10 minutes at a constant temperature of 75°C to fully gelatinize the starch and form a transparent solution. Prepare a PVA / starch mixed solution by mixing the two solutions in a 1:1 ratio and placing them in a 75°C water bath. Stir at 600 rpm for 30 minutes to ensure thorough mixing. Transfer the mixed solution to an ultrasonic cleaner and sonicate for 15 minutes to completely remove air bubbles, obtaining a clear coating solution for later use. Using a coating machine, uniformly spray the prepared mixed solution onto the surface of Penicillium baicale microbial fertilizer granules with bentonite as the "carrier," controlling the spraying rate to ensure complete coverage of the coating layer. The coated granules are dried at a temperature ≤40℃ to obtain the final coated microbial fertilizer product. Example 3

[0017] Prepare a 10% PVA solution by adding PVA to deionized water and stirring continuously at 300 rpm for 2 hours at 105°C until completely dissolved to form a transparent and homogeneous PVA solution. Prepare a 10% soluble starch solution by mixing soluble starch with deionized water and stirring at 300 rpm for 10 minutes at a constant temperature of 75°C to fully gelatinize the starch and form a transparent solution. Prepare a PVA / starch mixed solution by mixing the two solutions in a 1:1 ratio and placing them in a 75°C water bath. Stir at 600 rpm for 30 minutes to ensure thorough mixing. Transfer the mixed solution to an ultrasonic cleaner and sonicate for 15 minutes to completely remove air bubbles, obtaining a clear coating solution for later use. Using a coating machine, uniformly spray the prepared mixed solution onto the surface of Aspergillus niger microbial fertilizer granules with bentonite as the "carrier," controlling the spraying rate to ensure complete coverage of the coating layer. The coated granules are dried at a temperature ≤40℃ to obtain the final coated microbial fertilizer product. Comparative Example 1

[0018] Harz raspberry microbial fertilizer granules using bentonite as a "carrier". Comparative Example 2

[0019] Penicillium baicale microbial fertilizer granules using bentonite as a "carrier". Comparative Example 3

[0020] Aspergillus niger microbial fertilizer granules using bentonite as a "carrier".

[0021] The storage time, microbial agent looseness, and compressive strength of the coated microbial fertilizer granules prepared in Examples 1-3 were tested. The effective viable bacteria count of the microbial fertilizer granules at different storage times was determined according to NY / T2321: the product was stored in a cool, dry, and ventilated warehouse, and its shelf life was then determined. A commonly available compound microbial fertilizer granule was selected as a control group, and the trend of its effective viable bacteria count after 120 days of storage was examined. The test results are shown in Table 1.

[0022] Table 1 Initial viable count (CFU) 100 million / g The number of viable bacteria (CFU) after 120 days is 100 million / g. Effective viable count retention rate Example 1 184 149 81.0% Example 2 180 118 65.6% Example 3 122 108 88.5% Comparative Example 1 226 100 44.2% Comparative Example 2 190 94 49.5% Comparative Example 3 150 79 52.7%

[0023] As shown in Table 1, the effective viable count retention rate of the coated microbial fertilizer granules prepared by Examples 1-3 of the present invention is better than that of the microbial fertilizer granules in the corresponding comparative examples 1-3.

[0024] Further tests were conducted using 40N weights to assess the compressive strength and looseness of different microbial fertilizer granules. The test results are shown below. Figure 1-6Clearly, the microbial fertilizer granules in Comparative Examples 1-3 all exhibited varying degrees of breakage and "powdering" after being pressed by a 40N weight; while the coated microbial fertilizer granules prepared in Examples 1-3 showed little difference before and after being pressed by a 40N weight, indicating that the compressive strength and "powdering" defects of the microbial fertilizer granules were significantly improved at this time.

[0025] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing coated microbial fertilizer granules, wherein the prepared coated microbial fertilizer granules have the following characteristics, including a microbial granule core layer and a membrane layer covering the outside of the fertilizer; The coating process of the microbial fertilizer granules includes the following steps: Prepare aqueous solutions of polyvinyl alcohol (PVA) and a material that can provide glycogen separately, then mix the two, remove air bubbles and set aside; then use a coating machine to evenly spray the mixed solution onto the surface of the microbial fertilizer granules, and after drying, the coated microbial fertilizer granules are produced.

2. The method for preparing coated microbial fertilizer granules according to claim 1, characterized in that, The core layer of the coated microbial granules is composed of microbial fertilizer granules such as Trichoderma harzianum, Penicillium barometz, or Aspergillus niger.

3. The microbial particle core layer according to claim 1, characterized in that, The microbial fertilizer granules containing Trichoderma harzianum, Penicillium baicalensis, or Aspergillus niger can be microbial fertilizer granules obtained by mixing Trichoderma harzianum, Penicillium baicalensis, or Aspergillus niger with one or more carriers such as bentonite or diatomaceous earth.

4. The mixed solution of PVA and a hydrophilic material that can provide glycogen according to claim 1, characterized in that, The aqueous solution of the hydrophilic material that can provide glycogen can be an aqueous solution of starch, glucose, maltose and dextrin and mixtures thereof, with a mass fraction of 1%-50%.

5. The mixed solution of PVA and a hydrophilic material that can provide glycogen according to claim 1, characterized in that, The mass fraction of the PVA aqueous solution is 1%-50%.

6. The PVA according to claim 1 and the aqueous solution that can provide sugar raw materials, characterized in that, The mass ratio of PVA to the hydrophilic material that can provide glycogen is 1:9-9:

1.

7. The method for preparing coated microbial fertilizer granules according to claim 1, characterized in that, The mass ratio of the core layer and the membrane layer of the microbial fertilizer granules is 100:(0.5-10).

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