Potassium slow-release fertilizer, its preparation method and application

Abstract

The application discloses a kind of potassium slow-release fertilizer and its preparation method and application;The potassium slow-release fertilizer includes potassium-based manganese ore and controlled-release agent loaded on the potassium-based manganese ore;The controlled-release agent includes at least one of 2,6-anthraquinone disulfonic acid, lactate.In the present application, the potassium slow-release fertilizer is loaded with controlled-release agent by potassium-based manganese ore, and the release of potassium and manganese elements in potassium-based manganese ore is promoted by controlled-release agent, thereby increasing the content of potassium and manganese in soil, specifically: after the potassium slow-release fertilizer is applied to soil for 9 days, the potassium element can be released slowly ≥85mg / L, and when the application amount of potassium slow-release fertilizer in soil is increased, the release amount of potassium element can reach about 800mg / L.

Description

Technical Field

[0001] This invention belongs to the field of fertilizers, specifically relating to a slow-release potassium fertilizer, its preparation method, and its application. Background Technology

[0002] Potassium is an essential trace element for the human body and is vital for health. It maintains electrolyte balance, is crucial for heart and muscle function, and can help prevent chronic diseases. Manganese minerals in nature exhibit diversity due to their different oxidation states and structures. Theoretically, even in tetravalent manganese minerals, Mn does not exist in a single form. 4+ It exists, and Mn also exists. 3+ Mn 2+ Plasmatic valence state. Potassium salts such as potassium permanganate and potassium carbonate are commonly used in the preparation of different manganese minerals, allowing potassium to act as interlayer and tunnel filling ions to neutralize negative charges. Previous studies have focused on the differences in oxidation and adsorption properties of manganese ore structures, primarily for the removal of inorganic and organic pollutants from soil, water, and the atmosphere. No studies have yet found applications of manganese ores with different structures in agricultural production to investigate their effects as fertilizers on soil. Summary of the Invention

[0003] In order to overcome at least one of the technical problems existing in the prior art, one of the objectives of the present invention is to provide a potassium slow-release fertilizer.

[0004] The second objective of this invention is to provide a method for preparing potassium slow-release fertilizer.

[0005] The third objective of this invention is to provide the application of the above-mentioned slow-release potassium fertilizer or potassium-based manganese ore in the field of fertilizers.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A first aspect of the present invention provides a potassium slow-release fertilizer comprising potassium-based manganese ore and a controlled-release agent loaded on the potassium-based manganese ore; the controlled-release agent comprising at least one of 2,6-anthraquinone disulfonic acid and lactate.

[0008] In some embodiments of the present invention, the lactate includes at least one of sodium lactate, magnesium lactate, and lactic acid.

[0009] In some embodiments of the present invention, the sodium lactate is selected from at least one of L-sodium lactate, DL-sodium lactate, and D-sodium lactate.

[0010] In some embodiments of the present invention, the mass ratio of the potassium-based manganese ore to the controlled-release agent is 50:(0.1-10); in some embodiments of the present invention, the mass ratio of the potassium-based manganese ore to the controlled-release agent is selected from any value or a range formed by any two of the following: 50:0.1, 50:0.5, 50:1, 50:1.5, 50:2, 50:2.5, 50:3, 50:3.5, 50:4, 50:4.5, 50:5, 50:5.5, 50:6, 50:6.5, 50:7, 50:7.5, 50:8, 50:8.5, 50:9, 50:9.5, 50:10.

[0011] In some embodiments of the present invention, the controlled-release agent comprises 2,6-anthraquinone disulfonic acid and lactate; the mass ratio of the 2,6-anthraquinone disulfonic acid to lactate is 1:(0.1 to 30); in some embodiments of the present invention, the mass ratio of the 2,6-anthraquinone disulfonic acid to lactate can be any value or a range formed by any two of the following: 1:0.1, 1:0.5, 1:1, 1:2, 1:4, 1:6, 1:8, 1:10, 1:12, 1:14, 1:16, 1:18, 1:20, 1:22, 1:24, 1:26, 1:28, 1:30.

[0012] In some embodiments of the present invention, the mass percentage of Mn in the potassium-based manganese ore is 20-60%, and the mass percentage of K is 1-10%. In some embodiments of the present invention, the mass percentage of Mn in the potassium-based manganese ore can be selected from any value or a range formed by any combination of 20%, 30%, 40%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, and 60%. In some embodiments of the present invention, the mass percentage of K in the potassium-based manganese ore is any value or a range formed by any combination of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%.

[0013] In some embodiments of the present invention, the potassium-based manganese ore has a layered structure.

[0014] In some embodiments of the present invention, the potassium-based manganese ore is sodium manganese ore.

[0015] In some embodiments of the present invention, the increase in potassium in the soil after 9 days of application of the potassium slow-release fertilizer is ≥85 mg / L. In some embodiments of the present invention, the increase in potassium in the soil after 9 days of application of the potassium slow-release fertilizer is 85–2000 mg / L; in some embodiments of the present invention, the increase in potassium in the soil after 9 days of application of the potassium slow-release fertilizer is 85–1000 mg / L; in some embodiments of the present invention, the increase in potassium in the soil after 9 days of application of the potassium slow-release fertilizer is 85–820 mg / L.

[0016] The second aspect of the present invention provides a method for preparing the potassium slow-release fertilizer described in the first aspect of the present invention, comprising the following steps:

[0017] The potassium slow-release fertilizer is prepared by mixing raw materials including potassium-based manganese ore and a controlled-release agent.

[0018] In some embodiments of the present invention, the potassium-based manganese ore is prepared by a method comprising the following steps: boiling a mixture of concentrated hydrochloric acid and potassium permanganate and reacting for 10 to 60 minutes, and then aging at 55 to 65°C for 10 to 15 hours to obtain the ore.

[0019] In some embodiments of the present invention, the potassium-based manganese ore is prepared by a method comprising the following steps: first, manganese salt and alkali are mixed, then reacted with potassium permanganate, and then aged at 55-65°C for 10-15 hours to obtain the ore.

[0020] In some embodiments of the present invention, the manganese salt is selected from at least one of manganese chloride, manganese nitrate, and manganese sulfate.

[0021] In some embodiments of the present invention, the potassium-based manganese ore is prepared by a method comprising the following steps: first, mixing potassium permanganate and manganese salt, then reacting with nitric acid at 65-75°C, and then reacting with an alkali to obtain the ore.

[0022] In some embodiments of the present invention, the alkali is selected from at least one of sodium hydroxide and potassium hydroxide.

[0023] The third aspect of the present invention provides the application of the potassium slow-release fertilizer or potassium-based manganese ore described in the first aspect of the present invention in the field of fertilizers.

[0024] The beneficial effects of this invention are as follows: The potassium slow-release fertilizer of this invention uses a potassium-based manganese ore loaded with a controlled-release agent, which promotes the release of potassium and manganese elements in the potassium-based manganese ore, thereby increasing the potassium and manganese content in the soil. Specifically, after the potassium slow-release fertilizer is applied to the soil for 9 days, potassium can be slowly released at a rate of ≥85mg / L. When the amount of potassium slow-release fertilizer applied to the soil is increased, the amount of potassium released can reach about 800mg / L.

[0025] Furthermore, the potassium slow-release fertilizer of this invention can release potassium efficiently, is suitable for different types of soil, has universality and high efficiency, and its preparation method is simple and easy to operate, the raw materials are widely available, it is environmentally friendly, will not have an adverse impact on the original soil, is inexpensive, and is easy to promote and apply. Attached Figure Description

[0026] Figure 1 The X-ray diffraction spectra of manganese ore 1, manganese ore 2 and manganese ore 3 prepared in Example 1 are shown.

[0027] Figure 2 The images are scanning electron microscope (SEM) images of manganese ore 1, manganese ore 2 and manganese ore 3 prepared in Example 1.

[0028] Figure 3 This is a diagram illustrating the mechanism of potassium and manganese release from the potassium slow-release fertilizer in Example 2. Detailed Implementation

[0029] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0030] The sodium lactate used in the following examples is L-sodium lactate.

[0031] Example 1

[0032] This example provides a method for preparing potassium slow-release fertilizer, including the following steps:

[0033] (1) Preparation of potassium-based manganese ore

[0034] Preparation of manganese ore 1: 15 mL of concentrated hydrochloric acid solution was added dropwise to 500 mL of 0.4 mol / L potassium permanganate solution. The mixture was heated in an oil bath until it reached a boiling state, while magnetic stirring was performed simultaneously. Heating was continued for 30 min, followed by aging at 60 °C for 720 min to obtain a suspension of potassium-based manganese ore. The suspension was centrifuged, washed, and dried to obtain potassium-based manganese ore, designated as manganese ore 1. The dried manganese ore 1 was ground through a 100-mesh sieve and stored in a dry environment for later use.

[0035] Preparation of manganese ore 2: 125 mL of 0.3 mol / L MnCl2 and 250 mL of 0.5 mol / L NaOH were mixed at room temperature to obtain a mixed solution; then 125 mL of 0.2 mol / L KMnO4 was added dropwise to the above mixed solution. The resulting suspension was stirred for 30 min and then aged in an oven at 60 °C for 720 min to obtain a suspension of potassium-based manganese ore. The obtained suspension was centrifuged, washed, and dried to obtain potassium-based manganese ore, denoted as manganese ore 2. The dried manganese ore 2 was ground through a 100-mesh sieve and stored in a dry environment for later use.

[0036] Preparation of manganese ore 3: 1.58 g of potassium permanganate and 1.69 g of manganese sulfate monohydrate were dissolved in 70 mL of water and stirred for 10 min. Then, 15 mL of 10% nitric acid solution was added dropwise, and the reaction was carried out at 70 °C for 120 min. After the reaction was completed, 0.5 g of sodium hydroxide was added, and stirring was continued for 10 min. The precipitate formed by the reaction was then washed five times with deionized water and finally dried at 60 °C for 720 min to obtain potassium-based manganese ore, denoted as manganese ore 3. The dried manganese ore 3 was ground through a 100-mesh sieve and stored in a dry environment for later use.

[0037] Manganese ore 1, manganese ore 2, and manganese ore 3 were characterized using X-ray diffraction spectroscopy. Specific test results are as follows: Figure 1 As shown. By Figure 1 It can be seen that manganese ore 1, manganese ore 2 and manganese ore 3 are all sodium manganese ore, among which manganese ore 1 has a better crystal form, while the 001 and 002 crystal planes of manganese ore 2 and manganese ore 3 are very weak.

[0038] Scanning electron microscopy was used to test manganese ore 1, manganese ore 2, and manganese ore 3, respectively. The specific test results are as follows: Figure 2 As shown. By Figure 2 It can be seen that manganese ore 1, manganese ore 2 and manganese ore 3 all have a platy structure.

[0039] Inductively coupled plasma atomic emission spectrometry was used to test the content (i.e., mass percentage) of Mn and K elements in the three different potassium-based manganese ores, respectively. The specific test results are shown in Table 1.

[0040] Table 1. Mn and K content in three different potassium-based manganese ores

[0041] Manganese ore 1 Manganese ore 2 Manganese ore 3 K content 7.2±0.1％ 2.8±0.4％ 1.9±0.1％ Mn content 53.2±1.6％ 51.8±0.9％ 55.5±1.4％

[0042] As shown in Table 1, there are significant differences in interlayer potassium ions among manganese ore 1, manganese ore 2, and manganese ore 3. Among them, manganese ore 1 has a higher potassium content and is more suitable for use as a slow-release potassium fertilizer.

[0043] The effects of three different potassium-based manganese ores prepared by the above method on the release of manganese and potassium from the soil were tested. The specific test methods are as follows:

[0044] 50 mg of each of three different potassium-based manganese ores (manganese ore 1, manganese ore 2, and manganese ore 3) was mixed with 1000 mg of soil sample and shaken in a shaker at 180 r / min for 1 h to ensure uniform mixing. The original soil without manganese ore served as a control. 15 mL of distilled water was added to the mixed sample, and the mixture was placed in a 25℃ incubator. Samples were taken on days 3, 6, and 9 of the experiment, filtered through a 0.22 μm aqueous filter, and the manganese and potassium content in the aqueous solution was determined using inductively coupled plasma atomic absorption spectrometry (ICP-AES). The effects of different potassium-based manganese ores on manganese and potassium release from the soil were evaluated. The specific test results are shown in Table 2 below.

[0045] Table 2. Test results of manganese and potassium release from different potassium-based manganese ores in soil.

[0046]

[0047] As shown in Table 2, manganese ore 1, manganese ore 2, and manganese ore 3 all significantly increased the content of water-soluble potassium in the soil solution. Among them, manganese ore 1 had a more obvious effect on increasing the potassium content in the soil solution, with an increase of about 50 times on the 9th day.

[0048] (2) Loaded with 2,6-anthraquinone disulfonic acid (AQDS)

[0049] 0 mg, 0.226 mg, and 0.907 mg of 2,6-anthraquinone disulfonic acid were added to 50 mg of manganese ore 1, and the mixture was shaken at 180 r / min for 30 min to obtain potassium-based manganese ore loaded with different amounts of 2,6-anthraquinone disulfonic acid.

[0050] The potassium-based manganese ore loaded with different amounts of 2,6-anthraquinone disulfonic acid prepared above was mixed with 1000 mg of soil sample and shaken in a shaker at 180 r / min for 1 h to ensure uniform mixing. The original soil was used as a control. Then, 15 mL of distilled water was added to the mixed sample, and the sample was placed in a 25℃ incubator. Samples were taken on days 3, 6, and 9 of the experiment, filtered through a 0.22 μm aqueous filter, and the manganese and potassium content in the solution was determined using inductively coupled plasma atomic absorption spectrometry (ICP-AES). The effect of different loadings of 2,6-anthraquinone disulfonic acid on the release of manganese and potassium from the potassium-based manganese ore in the soil was evaluated. Specific test results are shown in Table 3.

[0051] Table 3 shows the test results of manganese and potassium release from soil by potassium-based manganese ore loaded with 2,6-anthraquinone disulfonic acid.

[0052]

[0053] As shown in Table 3, the loading of 2,6-anthraquinone disulfonic acid onto manganese ore 1 in this invention significantly increased the potassium content released from the soil. No manganese release was detected during the initial soil incubation process, but loading 0.907 mg of 2,6-anthraquinone disulfonic acid onto manganese ore 1 also increased the manganese content released from the soil. Therefore, it can be concluded that the addition of 2,6-anthraquinone disulfonic acid and manganese ore 1 to the soil increased the potassium release.

[0054] Example 2

[0055] This example provides a method for preparing potassium slow-release fertilizer, including the following steps:

[0056] (1) Preparation of potassium-based manganese ore

[0057] Preparation of manganese ore 1: 15 mL of concentrated hydrochloric acid solution was added dropwise to 500 mL of 0.4 mol / L potassium permanganate solution. The mixture was heated in an oil bath until it reached a boiling state, while magnetic stirring was performed simultaneously. Heating was continued for 30 min, followed by aging at 60 °C for 720 min to obtain a suspension of potassium-based manganese ore. The suspension was centrifuged, washed, and dried to obtain potassium-based manganese ore, designated as manganese ore 1. The dried manganese ore 1 was ground through a 100-mesh sieve and stored in a dry environment for later use.

[0058] (2) Sodium lactate supported

[0059] Add 0.907 mg of 2,6-anthraquinone disulfonic acid to 50 mg of manganese ore 1, and add 0 mg, 2.1 mg, and 5.6 mg of sodium lactate respectively. Shake at 180 r / min for 30 min to obtain 2,6-anthraquinone disulfonic acid modified potassium-based manganese ore with different contents of sodium lactate. Then add 2.1 mg of sodium lactate to 50 mg of manganese ore 1 and prepare potassium-based manganese ore loaded with sodium lactate in the same way.

[0060] Subsequently, the potassium-based manganese ore loaded with sodium lactate prepared above was mixed with 1000 mg of soil sample and shaken in a shaker at 180 r / min for 1 h to mix the potassium-based manganese ore and soil evenly, and the mixed samples were recorded as: Sample 1 (manganese ore 1 loaded with 0.907 mg of AQDS and 0 mg of sodium lactate), Sample 2 (manganese ore 1 loaded with only 2.1 mg of sodium lactate), Sample 3 (manganese ore 1 loaded with 0.907 mg of AQDS and 2.1 mg of sodium lactate), and Sample 4 (manganese ore 1 loaded with 0.907 mg of AQDS and 5.6 mg of sodium lactate). Then, 15 mL of distilled water was added to the above mixed sample, and the sample was placed in a 25°C incubator. Samples were taken on the 3rd, 6th and 9th days of the experiment, and the samples were filtered through a 0.22 μm water filter. The manganese and potassium content in the solution was determined by inductively coupled plasma atomic absorption spectrometry (ICP-AES). The effect of loading different amounts of sodium lactate on the release of manganese and potassium from potassium-based manganese ore in the soil was evaluated. The specific test results are shown in Table 4.

[0061] Table 4 shows the test results of manganese and potassium release from soil by potassium-based manganese ore loaded with 2,6-anthraquinone disulfonic acid and sodium lactate.

[0062]

[0063] Comparing samples 2 and 3-4 in Table 4, it can be seen that loading 2,6-anthraquinone disulfonic acid onto the potassium-based manganese ore of this invention significantly increases the release of potassium into the soil. Comparing samples 1 and 3-4 in Table 4, it can be seen that loading sodium lactate onto potassium-based manganese ore 1 of this invention simultaneously increases the content of both manganese and potassium in the soil. This indicates that sodium lactate enhances the reduction and dissolution of manganese in the stable potassium-based manganese ore, promotes the release of potassium ions from the interlayer of the potassium-based manganese ore structure, and increases the potassium content released from the potassium-based manganese ore into the soil. This not only significantly increases the release of the nutrient element potassium, but also significantly increases the manganese content. Manganese is one of the important micronutrient elements in soil, playing a multifaceted role in plant growth and soil health.

[0064] The mechanism diagram of potassium and manganese release from the soil by the potassium slow-release fertilizer in this example is shown below. Figure 3 As shown, the specific analysis is as follows:

[0065] 2,6-Anthraquinone disulfonic acid primarily acts as a redox medium during the reduction and dissolution of potassium-based manganese ore. It accepts electrons (from microorganisms or reducing substances) and transfers them to the surface of the potassium-based manganese ore, thereby promoting the reduction reaction. Therefore, 2,6-Anthraquinone disulfonic acid promotes the reduction and dissolution of manganese in structurally stable potassium-based manganese ore, releasing potassium ions from the interlayer structure of the ore and increasing the potassium content released from the ore in the soil. The reaction mechanism can be described as follows:

[0066] AQDS+2H + +2e - →AQDSH2

[0067] AQDS (oxidized state, quinone form) accepts electrons and is reduced to the hydroquinone form (AQDSH2).

[0068] K-MnO2+AQDSH2→K + +MnO2 / Mn 3+ / Mn 2+ +AQDS+H2O

[0069] AQDSH2 transfers electrons to K-MnO2, initiating a reduction reaction of manganese oxides, K + It detaches from the K-MnO2 layered structure.

[0070] The reaction mechanism by which sodium lactate promotes the release of manganese is described as follows:

[0071] C3H5O3 - →C3H4O3+2H + +2e -

[0072] Lactate ions (C3H5O3) - It undergoes an oxidation reaction in solution to produce pyruvic acid (C3H4O3) and release electrons.

[0073] K-MnO2+e - +H + →K + +MnO2 / Mn 3+ / Mn 2+

[0074] The electrons provided by sodium lactate are accepted by K-MnO2, triggering the reduction and dissolution of K-MnO2, thereby releasing K from the structure.

[0075] K-MnO2+C3H5O3 - +Microorganisms→K + +MnO2 / Mn 3+ / Mn 2+

[0076] Simultaneously, sodium lactate, by acting as an electron donor, promotes the reduction process of microorganisms and also improves the dissolution efficiency and K content of potassium-based manganese ore. + Release efficiency.

[0077] To investigate the effects of potassium-based manganese ore loaded with potassium-based manganese ore and sodium lactate on the release of manganese and potassium in different soils, the following experiments were conducted:

[0078] Add 0.907 mg of 2,6-anthraquinone disulfonic acid and 5.6 mg of sodium lactate to 50 mg of manganese ore 1, and shake at 180 r / min for 30 min to obtain modified potassium-based manganese ore loaded with sodium lactate and 2,6-anthraquinone disulfonic acid, which is the potassium slow-release fertilizer in this example.

[0079] Subsequently, the aforementioned potassium-based slow-release fertilizer was mixed with 1000 mg of paddy soil, grassland soil, and vegetable soil samples, respectively. The mixture was shaken in a shaker at 180 r / min for 1 h to ensure thorough mixing of the potassium-based manganese ore with the soil, resulting in a mixed sample. Then, 15 mL of distilled water was added to the mixed sample, and the sample was placed in a 25℃ incubator. Samples were taken on days 3, 6, and 9 of the experiment, filtered through a 0.22 μm aqueous filter, and the manganese and potassium content in the solution was determined using inductively coupled plasma atomic absorption spectrometry (ICP-AES). The effect of potassium-based manganese ore on the release of manganese and potassium in different soil types was evaluated. Specific test results are shown in Table 5.

[0080] Table 5 shows the test results of manganese and potassium release from potassium-based manganese ore in different types of soil.

[0081]

[0082]

[0083] As shown in Table 5, the manganese ore 1 loaded with 2,6-anthraquinone disulfonic acid and sodium lactate in this invention significantly increased the release of manganese and potassium in paddy soils, grassland soils, and vegetable soils. This further demonstrates that the potassium slow-release fertilizer in this invention is suitable for various soil types, possessing broad applicability and high application value. Paddy soils are flooded soils, where soil particles and manganese ore undergo reduction and dissolution under chemical and biological processes. If potassium-rich manganese ore 1 is applied to flooded soils, it can slowly reduce and dissolve, accompanied by the release of potassium from its structure, thereby achieving the slow release of potassium nutrients in flooded environments and promoting healthy crop growth.

[0084] To investigate the effect of the application rate of potassium-based manganese ore on the release of manganese and potassium from the soil, the following experiment was conducted:

[0085] 0.907 mg of 2,6-anthraquinone disulfonic acid and 5.6 mg of sodium lactate were added to 50 mg, 100 mg, and 200 mg of potassium-based manganese ore 1, respectively. The mixture was shaken at 180 rpm for 30 min to obtain potassium-based manganese ore modified with sodium lactate and 2,6-anthraquinone disulfonic acid. This mixture was then added to 1000 mg of soil sample and shaken at 180 rpm for 1 h to ensure thorough mixing. 15 mL of distilled water was added to the mixture, and the mixture was placed in a 25℃ incubator. Samples were taken on days 3, 6, and 9 of the experiment, filtered through a 0.22 μm aqueous filter, and inductively coupled plasma atomic absorption spectrometry (ICP-AAS) was used to determine the manganese and potassium content in the solution. The effect of potassium-based manganese ore application on the release of manganese and potassium from the soil was evaluated. The specific test results are shown in Table 6.

[0086] Table 6 shows the test results of manganese and potassium release in the soil based on the application of potassium-based manganese ore.

[0087]

[0088] As shown in Table 6, the manganese and potassium content in the soil solution increases significantly with the increase of the amount of potassium-based manganese ore applied in this invention. However, for cost-effectiveness considerations, the amount of potassium-based manganese ore applied needs to be comprehensively evaluated in practical applications.

[0089] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A slow-release potassium fertilizer, characterized in that: The invention comprises potassium-based manganese ore and a controlled-release agent supported on the potassium-based manganese ore; the controlled-release agent comprises at least one of 2,6-anthraquinone disulfonic acid and lactate. The potassium-based manganese ore is prepared by a method including the following steps: boiling a mixture of concentrated hydrochloric acid and potassium permanganate and reacting for 10-60 minutes, then aging at 55-65℃ for 10-15 hours to obtain the ore.

2. The potassium slow-release fertilizer according to claim 1, characterized in that: The mass ratio of potassium-based manganese ore to controlled-release agent is 50:(0.1~10).

3. The potassium slow-release fertilizer according to claim 1, characterized in that: The controlled-release agent comprises 2,6-anthraquinone disulfonic acid and lactate; the mass ratio of 2,6-anthraquinone disulfonic acid and lactate is 1:(0.1~30).

4. The potassium slow-release fertilizer according to claim 1, characterized in that: In the potassium-based manganese ore, the mass percentage of Mn is 20-60%, and the mass percentage of K is 1-10%.

5. The potassium slow-release fertilizer according to claim 1, characterized in that: The potassium-based manganese ore has a layered structure.

6. The potassium slow-release fertilizer according to any one of claims 1 to 5, characterized in that: The potassium slow-release fertilizer was applied for 9 days, and the increase in potassium in the soil was ≥85 mg / L.

7. The method for preparing potassium slow-release fertilizer according to any one of claims 1 to 6, characterized in that: Includes the following steps: The potassium slow-release fertilizer is prepared by mixing raw materials including potassium-based manganese ore and a controlled-release agent.

8. The application of the potassium slow-release fertilizer according to any one of claims 1 to 6 in the field of fertilizers.

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