Fertilizer based on potassium formate and preparation method thereof

Abstract

The invention provides a potassium formate-based fertilizer and a preparation method thereof, and the method comprises the following steps: step S1: dissolving and dispersing potassium formate and humic acid in water to obtain a first mixed solution; s2, adjusting the pH value of the first mixed solution, adding glutaraldehyde, and carrying out a cross-linking reaction, so that humic acid is cross-linked and is combined with potassium formate, and a second mixed solution is obtained; and S3, carrying out spray drying treatment on the second mixed solution to obtain the potassium formate-based fertilizer. According to the application, the fertilizer obtained by the method has a good slow-release effect, and can realize long-acting release of the potassium element, so that the utilization rate of the potassium element by plants is improved, and the loss and waste of the potassium element are reduced.

Description

Technical Field

[0001] This application belongs to the technical field of chemical fertilizer production, and particularly relates to a fertilizer based on potassium formate and a preparation method thereof. Background Art

[0002] Potassium formate (chemical formula: HCOOK) is an inorganic compound, usually in the form of white crystals or granules and soluble in water. It is the potassium salt of formic acid and is commonly used in agriculture, the chemical industry, and some biological applications. Since potassium formate can provide the potassium element required by plants and the formate ion has little impact on plant growth, it is often used as a potassium source in chemical fertilizers. Compared with other potassium salt fertilizers, potassium formate has better comprehensive performance and is particularly suitable for high-value cash crops.

[0003] However, the problem with it as a potassium fertilizer is that the nutrient release rate is relatively fast. This may cause plants to absorb more potassium elements in the short term, but the long-term continuous supply is insufficient. The too-fast nutrient release may prevent plants from continuously absorbing the required potassium elements from the soil for a long time, resulting in an increased application frequency. The rapid loss of potassium elements also causes resource waste and cost increase.

[0004] Therefore, when using potassium formate as the potassium element in fertilizers, it is necessary to control the release of potassium formate in the fertilizers, so as to achieve the slow-release effect, promote the full absorption and utilization of potassium elements in the fertilizers by plants, reduce the waste of potassium elements, and achieve the effect of providing potassium elements for a long time.

[0005] Current slow-release fertilizers generally exist in the form of granules. Generally, inert porous materials are used as carriers to fix pesticides or fertilizers on the surface or in the porous structure of the carriers; or directly perform coating treatment on pesticides or fertilizers to achieve the slow-release effect. However, these methods are not suitable for the slow release of potassium formate.

[0006] Patent CN119100881A discloses a nano slow-release pesticide-fertilizer with a polydopamine coating and a preparation method thereof. This nano slow-release pesticide-fertilizer uses a simple one-pot method. By means of the coordination assembly between zinc ions and imidazole-2-carboxaldehyde, fungicides and fertilizers are encapsulated in the synthesized zinc-based nano-carrier ZIF-90, and finally a layer of polydopamine is coated outside the carrier. This nano slow-release pesticide-fertilizer, by mass percentage, includes the following components: 45-60 wt% zinc-based nano-carrier ZIF-90, 15-30 wt% pesticide-fertilizer, and 5-15 wt% coating material polydopamine. The nano slow-release pesticide-fertilizer prepared by this patent has the characteristics of small average particle size, good biocompatibility, and environmental safety, and has good application prospects.

[0007] Patent 119241305A discloses a slow-release fertilizer for saline-alkali land and its preparation method, including: a granular core formed by co-granulating a basic fertilizer composition and biochar powder; a first coating layer formed on the surface of the granular core by a mixture of γ-polyglutamic acid or its derivative and sodium alginate; a second coating layer formed by sulfur on the surface of the first coating layer; a third coating layer formed by an anti-caking agent on the surface of the second coating layer. This slow-release fertilizer for saline-alkali land has strong functionality, good slow-release effect, improves soil aggregate structure, increases water and fertilizer utilization rate, synergistically reduces the pH of saline-alkali soil, increases the content of nutrients and organic matter in the soil, promotes plant growth and development, and improves soil microecology.

[0008] The above patents all achieve the slow-release effect by loading pesticides or fertilizers using specific inorganic carriers and then coating them. However, the general inorganic carriers have poor loading effects on potassium formate. Therefore, it is difficult to achieve the slow-release of potassium formate by the above methods.

[0009] Based on this, there is a need to provide a potassium formate-based fertilizer with good slow-release effect. Summary of the Invention

[0010] In view of this, the present application provides a potassium formate-based fertilizer and its preparation method. This fertilizer has a good slow-release effect, can achieve the long-term release of potassium element, thereby improving the utilization rate of potassium element by plants and reducing the loss and waste of potassium element.

[0011] In a first aspect, the present application provides a method for preparing a potassium formate-based fertilizer, which is characterized by including the following steps:

[0012] Step S1: Dissolve and disperse potassium formate and humic acid in water to obtain a first mixed solution;

[0013] Step S2: Adjust the pH of the first mixed solution and then add glutaraldehyde for cross-linking reaction to cross-link humic acid and combine with potassium formate to obtain a second mixed solution;

[0014] Step S3: Spray-dry the second mixed solution to obtain a potassium formate-based fertilizer.

[0015] According to the present application, the inventor found that humic acid has a good loading effect on potassium formate, and under the action of glutaraldehyde, humic acid is cross-linked. The fertilizer obtained by spray-drying has a good slow-release effect, can achieve the long-term release of potassium element, thereby improving the utilization rate of potassium element by plants and reducing the loss and waste of potassium element.

[0016] In some embodiments, in step S1, the mass ratio of potassium formate to humic acid in the first mixed solution is 1:2 - 4, and the mass percentage content of potassium formate in the first mixed solution is 0.5% - 3%.

[0017] In some embodiments, in step S1, after dissolving and dispersing potassium formate and humic acid in water, the following steps are further included: adding an aqueous solution of aminopolysaccharide to obtain a first mixture; wherein the aminopolysaccharide includes chitosan and / or carboxymethyl chitosan.

[0018] In some embodiments, in step S1, the mass ratio of potassium formate to aminopolysaccharide in the first mixture is 1:1 to 3.

[0019] In some embodiments, in step S1, the aminopolysaccharide includes chitosan and carboxymethyl chitosan, and the mass ratio of chitosan to carboxymethyl chitosan is 1:0.5 to 1.

[0020] In some embodiments, the degree of deacetylation of chitosan is 75% to 98%; the degree of carboxymethyl substitution of carboxymethyl chitosan is 80% to 95%.

[0021] In some embodiments, in step S2, the pH adjustment includes: adjusting the pH of the first mixture to 6.5 to 7.5.

[0022] In some embodiments, in step S2, the conditions for the cross-linking reaction include: the mass concentration of glutaraldehyde in the reaction system is 0.1% to 1%, the reaction temperature is 40 to 60°C, and the reaction time is 20 to 60 min.

[0023] In some embodiments, in step S3, the conditions for spray drying include: the temperature of the feed liquid is 25 to 30°C, the inlet air temperature is 120 to 160°C, the outlet air temperature is 60 to 90°C, the nozzle diameter is 0.4 to 1 mm, and the spray pressure is 1.5 to 2.5 MPa.

[0024] In a second aspect, the present application provides a fertilizer based on potassium formate, which is prepared by the method according to any one of the embodiments in the first aspect. Specific Embodiments

[0025] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the following further details the present application in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0026] In the description of this specification, the descriptions with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0027] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0028] In a first aspect, the present application provides a method for preparing a formate-based fertilizer, which is characterized by including the following steps:

[0029] Step S1: Dissolve and disperse formate and humic acid in water to obtain a first mixed solution;

[0030] Step S2: Adjust the pH of the first mixed solution and then add glutaraldehyde for cross-linking reaction to cross-link the humic acid and bind the formate to obtain a second mixed solution;

[0031] Step S3: Perform spray drying treatment on the second mixed solution to obtain a formate-based fertilizer.

[0032] According to the present application, the inventors found that humic acid has a good loading effect on formate, and under the action of glutaraldehyde, the humic acid is cross-linked. The fertilizer obtained by spray drying has a good slow-release effect, can achieve the long-term release of potassium elements, thereby improving the utilization rate of potassium elements by plants and reducing the loss and waste of potassium elements.

[0033] Specifically, humic acid is a complex natural organic macromolecule mainly composed of aromatic and aliphatic skeletons. The molecule contains various active groups, including hydroxyl groups, carboxyl groups, phenolic hydroxyl groups, ether bonds, amino groups, and carbonyl groups, etc. Among them, the carboxyl group can be deprotonated to form carboxylate salts, making humic acid carry a large amount of negative charges. It can adsorb potassium ions through electrostatic interaction, thus preventing the rapid loss of potassium elements. In addition, due to its special structure, the formate group in potassium formate can act on the hydroxyl or amino groups in humic acid and combine with humic acid through physical (forming hydrogen bonds with hydroxyl groups) or chemical (reacting with hydroxyl or amino groups to form hemiacetals or imines), thereby further increasing the negative charge of humic acid and making it have a stronger adsorption effect on potassium elements. At the same time, it can be understood that the aromatic structure in the humic acid molecule provides a hydrophobic environment and can also fix potassium formate molecules or potassium elements through physical adsorption or chelation. Therefore, through the above effects, humic acid has a good loading effect on potassium formate, and the formed complex has a strong adsorption and fixation effect on potassium elements.

[0034] In step S2, the complex formed in the first mixture further undergoes crosslinking under the action of glutaraldehyde. The hydroxyl and amino groups in humic acid can react with the aldehyde groups of glutaraldehyde, which can cause crosslinking between the chain structures of humic acid to form a more stable three-dimensional crosslinked network. The inventor found that the crosslinked humic acid has a better loading and slow-release effect on potassium elements, which can further improve the loading efficiency of the fertilizer for potassium elements and achieve a longer-lasting slow-release effect.

[0035] In step S3, the crosslinked product formed in the second mixture is dried by using the spray drying method. Spray drying can obtain fertilizers with complete structures and uniform particle size distributions, thereby making the fertilizers have a more stable slow-release effect.

[0036] Based on this, the fertilizer based on potassium formate obtained by the above method has a good slow-release effect, can achieve the long-term release of potassium elements, thereby improving the utilization rate of potassium elements by plants and reducing the loss and waste of potassium elements.

[0037] In some embodiments, in step S1, the mass ratio of potassium formate to humic acid in the first mixture is 1:2 - 4, and the mass percentage content of potassium formate in the first mixture is 0.5% - 3%.

[0038] In the above-mentioned some embodiments, controlling the mass ratio of potassium formate to humic acid within the above range and simultaneously controlling the mass percentage content of potassium formate in the first mixture within the above range, appropriate reactant concentrations are beneficial to the full dissociation and combination of each component, which can make potassium formate fully combine with humic acid to form a more stable potassium salt complex, thereby preventing the rapid dissolution and loss of potassium formate in the fertilizer after application, and the obtained fertilizer has a better slow-release effect.

[0039] In some embodiments, in step S1, after dissolving and dispersing potassium formate and humic acid in water, the following steps are further included: adding an aqueous solution of amino polysaccharide to obtain a first mixture; wherein the amino polysaccharide includes chitosan and / or carboxymethyl chitosan.

[0040] In the above-mentioned some embodiments, the inventors further found that since the amino content in humic acid is generally low and the reaction activity of hydroxyl groups is relatively weak, the crosslinking density of the formed crosslinked product is relatively reduced. By further adding amino polysaccharide to the first mixture, the amino groups on the amino polysaccharide can be further crosslinked with humic acid under the action of glutaraldehyde, and at the same time, the hydroxyl groups on the amino polysaccharide can bind to humic acid through hydrogen bonds, so that the crosslinking density of the crosslinked product is higher, and it has a better adsorption and fixation effect on potassium elements, improving the loading efficiency. At the same time, after the fertilizer is applied, the polysaccharide segments in the crosslinked product will gradually decompose and the crosslinking density will gradually decrease, thus realizing the long-term release of potassium elements, and the obtained fertilizer has a better slow-release effect.

[0041] It can be understood that amino polysaccharide refers to polysaccharide compounds containing amino groups, generally including chitosan and carboxymethyl chitosan. Chitosan is a product formed by removing part of the acetyl groups from chitin to form amino groups, and carboxymethyl chitosan is a product obtained by carboxymethyl modification of chitosan, which converts part of the amino groups and hydroxyl groups into carboxymethyl groups.

[0042] In some embodiments, in step S1, the mass ratio of potassium formate to amino polysaccharide in the first mixture is 1:1 to 3.

[0043] In the above-mentioned some embodiments, controlling the mass ratio of potassium formate to amino polysaccharide in the first mixture within the above range can further improve the crosslinking density of the crosslinked product, and at the same time, the easily degradable amino polysaccharide can regulate the slow release of potassium elements in the fertilizer, so that the fertilizer has a better slow-release effect.

[0044] In some embodiments, in step S1, the amino polysaccharide includes chitosan and carboxymethyl chitosan, and the mass ratio of chitosan to carboxymethyl chitosan is 1:0.5 to 1.

[0045] In some of the above embodiments, the amino polysaccharide includes chitosan and carboxymethyl chitosan at the same time, and the mass ratio of the two is controlled within the above range. The inventors found that although chitosan contains a large amount of amino groups that can effectively increase the crosslinking density of the crosslinked product, there are still a large number of unreacted amino groups in chitosan, which will balance the negative charge of the humic acid and potassium formate complex, resulting in a weakened electrostatic attraction to potassium ions. Although the resulting crosslinked product has better slow-release performance, its potassium ion loading performance becomes weak. Therefore, in the early stage of application of the fertilizer obtained by spray drying, the non-tightly loaded potassium element is released too fast. Therefore, although the fertilizer obtained by further crosslinking with only chitosan can achieve the effect of long-term slow release of potassium element, due to the weakened loading effect, the release rate is too fast in the early stage; based on this, by using a certain proportion of chitosan and carboxymethyl chitosan for crosslinking, where chitosan can effectively increase the crosslinking density of the crosslinked product, and some hydroxyl and amino groups on carboxymethyl chitosan can also participate in the crosslinking reaction. At the same time, a large number of carboxymethyl groups on carboxymethyl chitosan can increase the negative charge of the crosslinked product, thereby reducing the influence of unreacted amino groups on chitosan on the charge of the crosslinked product. At this time, the obtained crosslinked product has good loading efficiency for potassium ions, and thus the obtained fertilizer has better long-term slow-release effect.

[0046] In some embodiments, the deacetylation degree of chitosan is 75% - 98%; the carboxymethyl substitution degree of carboxymethyl chitosan is 80% - 95%. Based on the above embodiments, when the deacetylation degree of chitosan and the carboxymethyl substitution degree of carboxymethyl chitosan are within the above range, the fertilizer has better slow-release effect.

[0047] In some embodiments, in step S2, adjusting the pH includes: adjusting the pH of the first mixture to 6.5 - 7.5. Based on the above embodiments, when the pH in the mixture is within the above range, glutaraldehyde has good reaction activity with both amino groups and hydroxyl groups, which can promote the crosslinking of each component in the mixture.

[0048] In some embodiments, in step S2, the conditions for the crosslinking reaction include: the mass concentration of glutaraldehyde in the reaction system is 0.1% - 1%, the reaction temperature is 40 - 60 °C, and the reaction time is 20 - 60 min. Based on the above embodiments, under the above crosslinking reaction conditions, a crosslinked product with a suitable crosslinking density can be obtained, and the obtained fertilizer has better slow-release effect.

[0049] In some embodiments, in step S3, the conditions for spray drying include: the temperature of the feed liquid is 25 - 30 °C, the inlet air temperature is 120 - 160 °C, the outlet air temperature is 60 - 90 °C, the nozzle diameter is 0.4 - 1 mm, and the spray pressure is 1.5 - 2.5 MPa. Based on the above embodiments, under the above conditions of spray drying, a fertilizer with a suitable uniformity and particle size can be obtained, and the obtained fertilizer has a stable slow-release effect.

[0050] In a second aspect, the present application provides a formate-based fertilizer prepared according to the method of any of the embodiments of the first aspect.

[0051] According to the present application, the fertilizer is prepared according to any of the embodiments of the first aspect, and thus has the beneficial effects of the first aspect, that is, the fertilizer has a good slow-release effect, can achieve the long-term release of potassium element, thereby improving the utilization rate of potassium element by plants and reducing the loss and waste of potassium element.

[0052] Humic acid, from Xinjiang Shengda Yifang Biotechnology Co., Ltd.;

[0053] Chitosan, with a degree of deacetylation of 90%, from Hubei Shiteng Chemical Technology Co., Ltd.;

[0054] Carboxymethyl chitosan, with a degree of deacetylation of 92% and a carboxymethyl substitution degree of 90%, from Hubei Shiteng Chemical Technology Co., Ltd.

[0055] The following specific examples are used to illustrate the solutions of the present application. Unless otherwise specified, the raw materials used in the following examples are all from ordinary commercially available products, and the devices or equipment used are all purchased from conventional market sales channels.

[0056] Example 1

[0057] Dissolve 120 g of chitosan and 80 g of carboxymethyl chitosan in 4800 g of 1 wt% acetic acid aqueous solution to obtain an amino polysaccharide aqueous solution;

[0058] Disperse 300 g of humic acid in 4600 g of water, adjust the pH to 7 with sodium hydroxide, stir to obtain a humic acid aqueous solution, add 100 g of potassium formate to the humic acid aqueous solution, and stir for 1 h to obtain a humic acid-potassium formate composite solution;

[0059] Slowly add the amino polysaccharide aqueous solution to the humic acid-potassium formate composite solution, stir evenly at 60 rpm to obtain a first mixed solution;

[0060] After adjusting the pH of the first mixed solution to 6.5, add a 25 wt% glutaraldehyde aqueous solution dropwise to make the concentration of glutaraldehyde in the system 0.5 wt%. Stir and react at 45°C and 60 rpm for 35 min to obtain a second mixed solution;

[0061] Cool the second mixed solution to 25°C and then perform spray drying, with an inlet air temperature of 135°C, an outlet air temperature of 65°C, a nozzle diameter of 0.8 mm, and a spray pressure of 2 MPa to obtain a formate-based fertilizer.

[0062] Example 2

[0063] Disperse 300 g of humic acid in 9600 g of water, adjust the pH to 7 using sodium hydroxide, stir to obtain an aqueous humic acid solution, add 100 g of potassium formate to the aqueous humic acid solution, and stir for 1 h to obtain a humic acid - potassium formate composite solution, which is the first mixed solution;

[0064] After adjusting the pH of the first mixed solution to 6.5, add dropwise a 25 wt% aqueous glutaraldehyde solution to make the concentration of glutaraldehyde in the system 0.5 wt%. Stir and react at 45 °C at 60 rpm for 35 min to obtain a second mixed solution;

[0065] Cool the second mixed solution to 25 °C and then perform spray drying. The inlet air temperature is 135 °C, the outlet air temperature is 65 °C, the nozzle diameter is 0.8 mm, and the spray pressure is 2 MPa to obtain a potassium - formate - based fertilizer.

[0066] Example 3

[0067] Dissolve 200 g of chitosan in 4800 g of 1 wt% acetic acid aqueous solution to obtain an aqueous amino - polysaccharide solution;

[0068] Disperse 300 g of humic acid in 4600 g of water, adjust the pH to 7 using sodium hydroxide, stir to obtain an aqueous humic acid solution, add 100 g of potassium formate to the aqueous humic acid solution, and stir for 1 h to obtain a humic acid - potassium formate composite solution;

[0069] Slowly add the aqueous amino - polysaccharide solution to the humic acid - potassium formate composite solution and stir evenly at 60 rpm to obtain a first mixed solution;

[0070] After adjusting the pH of the first mixed solution to 6.5, add dropwise a 25 wt% aqueous glutaraldehyde solution to make the concentration of glutaraldehyde in the system 0.5 wt%. Stir and react at 45 °C at 60 rpm for 35 min to obtain a second mixed solution;

[0071] Cool the second mixed solution to 25 °C and then perform spray drying. The inlet air temperature is 135 °C, the outlet air temperature is 65 °C, the nozzle diameter is 0.8 mm, and the spray pressure is 2 MPa to obtain a potassium - formate - based fertilizer.

[0072] Example 4

[0073] Dissolve 200 g of carboxymethyl chitosan in 4800 g of water to obtain an aqueous amino - polysaccharide solution;

[0074] Disperse 300 g of humic acid in 4600 g of water, adjust the pH to 7 using sodium hydroxide, stir to obtain an aqueous humic acid solution, add 100 g of potassium formate to the aqueous humic acid solution, and stir for 1 h to obtain a humic acid - potassium formate composite solution;

[0075] Slowly add the aqueous solution of amino polysaccharide to the potassium formate-humic acid composite solution, and stir evenly at 60 rpm to obtain the first mixed solution;

[0076] After adjusting the pH of the first mixed solution to 6.5, add an aqueous solution of 25 wt% glutaraldehyde dropwise so that the concentration of glutaraldehyde in the system is 0.5 wt%. Stir and react at 45 °C and 60 rpm for 35 min to obtain the second mixed solution;

[0077] Cool the second mixed solution to 25 °C and then perform spray drying. The inlet air temperature is 135 °C, the outlet air temperature is 65 °C, the nozzle diameter is 0.8 mm, and the spray pressure is 2 MPa to obtain the formate-based fertilizer.

[0078] Comparative Example 1

[0079] Disperse 300 g of humic acid in 9600 g of water, adjust the pH to 7 using sodium hydroxide, stir to obtain an aqueous solution of humic acid, and add 100 g of potassium formate to the aqueous solution of humic acid and stir for 1 h to obtain the potassium formate-humic acid composite solution, which is the first mixed solution;

[0080] After the first mixed solution is at 25 °C, perform spray drying. The inlet air temperature is 135 °C, the outlet air temperature is 65 °C, the nozzle diameter is 0.8 mm, and the spray pressure is 2 MPa to obtain the formate-based fertilizer.

[0081] Test method:

[0082] Perform simulated soil release tests on the fertilizers obtained in Examples 1 to 4 and Comparative Example 1, specifically including:

[0083] Prepare the soil: Take 500 g of air-dried soil and put it into a breathable container.

[0084] Mix the fertilizer: Mix evenly according to 5 g of fertilizer / 500 g of soil.

[0085] Simulate irrigation: Simulate rainfall or irrigation every 3 days and add 50 mL of water.

[0086] Regular sampling: Take soil samples at 20-day intervals. Disperse the soil samples in water for 30 min and then centrifuge to take the supernatant, and measure the content of potassium ions in the soil solution, so as to obtain the content of potassium element in the soil, and calculate the release rate of potassium element in the fertilizer; Release rate = (content of potassium element in the soil on the nth day - content of potassium element in the original soil solution) / content of potassium element in the fertilizer.

[0087] The test results are shown in Table 1.

[0088] Table 1

[0089]

[0090] Due to certain errors in the testing process, it is generally considered that a release rate greater than 98% can be regarded as complete release. In addition, since the unbound potassium formate will be rapidly released into the soil in the first 20 days, the loading efficiency of the fertilizer for potassium can be judged according to the size of the 20-day release rate.

[0091] As can be seen from Table 1, the fertilizers obtained in each example have better loading efficiency for potassium and better slow-release effects compared with the comparative example. In Comparative Example 1, only potassium formate and humic acid were compounded and dried to obtain the fertilizer, which was compounded through the interaction between humic acid and potassium formate. The loading efficiency and fixation effect on potassium were poor, and it was easily dissociated under the action of water and microorganisms, resulting in a poor slow-release effect.

[0092] As can be seen from Examples 1 to 4, the fertilizer obtained by cross-linking a certain proportion of chitosan and carboxymethyl chitosan with glutaraldehyde in Example 1 has better loading efficiency for potassium and better slow-release effects; although cross-linking treatment with glutaraldehyde was carried out in Example 2, the effect was limited and it was basically completely released in 80 days; in Example 3, chitosan was used in combination with glutaraldehyde for cross-linking treatment. Although it has a good slow-release effect, its 20-day release rate is relatively high, indicating that its loading efficiency for potassium is poor and it is easy to cause the loss of potassium in the early stage of application; in Example 4, carboxymethyl chitosan was used in combination with glutaraldehyde for cross-linking treatment. Although its loading efficiency for potassium is good, the improvement of the cross-linking density is small, and the slow-release effect is not as good as that of Example 1.

[0093] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a fertilizer based on potassium formate, characterized in that The following steps are involved: Step S1: dissolving potassium formate and humic acid in water to obtain a first mixed solution; Step S2: adjusting the pH of the first mixed solution and then adding glutaraldehyde to carry out a cross-linking reaction, so that the humic acid is cross-linked and combined with potassium formate to obtain a second mixed solution; Step S3: spray-drying the second mixed solution to obtain a potassium formate-based fertilizer.

2. The method according to claim 1, characterized in that In the step S1, the mass ratio of potassium formate to humic acid in the first mixed solution is 1:2-4, and the mass percentage of potassium formate in the first mixed solution is 0.5%-3%.

3. The method according to claim 2, characterized in that In the step S1, after dissolving and dispersing potassium formate and humic acid in water, the step further includes: An amino polysaccharide aqueous solution is added to obtain a first mixed solution; wherein the amino polysaccharide includes chitosan and / or carboxymethyl chitosan.

4. The method according to claim 3, characterized in that In the step S1, the mass ratio of the potassium formate to the amino polysaccharide in the first mixed solution is 1:1-3.

5. The method according to claim 4, characterized in that In the step S1, the amino polysaccharide includes chitosan and carboxymethyl chitosan, and the mass ratio of the chitosan to the carboxymethyl chitosan is 1:0.5-1.

6. The method according to claim 5, characterized in that The deacetylation degree of the chitosan is 75% to 98%; the carboxymethyl substitution degree of the carboxymethyl chitosan is 80% to 95%.

7. The method according to any one of claims 1 to 6, characterized in that: In the step S2, adjusting the pH includes: adjusting the pH of the first mixed solution to 6.5-7.

5.

8. The method according to claim 7, characterized in that In step S2, the conditions of the cross-linking reaction include: the mass concentration of glutaraldehyde in the reaction system is 0.1% to 1%, the reaction temperature is 40 to 60°C, and the reaction time is 20 to 60 minutes.

9. The method according to claim 1, characterized in that: In step S3, the spray drying conditions include: feed liquid temperature of 25-30°C, air inlet temperature of 120-160°C, air outlet temperature of 60-90°C, nozzle diameter of 0.4-1 mm, and spray pressure of 1.5-2.5 MPa.

10. A fertilizer based on potassium formate, characterized in that Prepared according to the method according to any one of claims 1 to 9.

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