Organic potassium phosphate liquid fertilizer and preparation method thereof

Abstract

The invention aims to protect an organic potassium phosphate liquid fertilizer and a preparation method thereof. The liquid organic potassium phosphate is obtained by esterification of orthophosphoric acid and binary or trihydric alcohol and salt formation with potassium carbonate or potassium hydroxide, can replace inorganic potassium hydrogen phosphate and potassium dihydrogen phosphate to be used as a fertilizer, has excellent leaf affinity, can be quickly absorbed at leaves and roots, enters plants and does not need to be converted into phospholipid, and the organic potassium phosphate can be used as an organic fertilizer. The phosphate can be directly utilized after being absorbed by plants, so that the absorption and utilization rate of phosphorus and potassium is effectively improved, and the effect is quick; meanwhile, the stability of phosphorus is improved, the phosphorus and medium trace elements are not prone to generating precipitates, the phosphorus can be well mixed with pesticides, the fertilizer is suitable for modern fertilization modes such as unmanned aerial vehicle flight prevention, and the defect that leaves are damaged due to traditional high-concentration application of monopotassium phosphate is overcome. The method has the advantages of mild reaction, operation at normal temperature, no need of heating and simple synthesis steps, and is suitable for industrial production and large-scale popularization and application.

Description

Technical Field

[0001] This invention belongs to the field of liquid fertilizer technology, specifically relating to an organic potassium phosphate liquid fertilizer and its preparation method. Background Technology

[0002] Liquid fertilizer is a fast-acting fertilizer that uses water as a medium and carries essential nutrients to plants in a dissolved or suspended state. Its core advantages lie in its excellent water solubility, lack of residue, and direct absorption by crop roots or leaves, resulting in significantly faster fertilization than traditional solid fertilizers. With the development of modern agriculture, new and efficient fertilization methods such as drone spraying and drip irrigation are gradually replacing traditional methods, thus placing higher demands on liquid fertilizers. These demands include higher nutrient content, lower water-insoluble matter, and considerations for raw material costs, component forms, safety, and processing methods. Commonly used phosphate fertilizer raw materials in liquid fertilizers include ammonium hydrogen phosphate, ammonium dihydrogen phosphate, potassium monohydrogen phosphate, potassium dihydrogen phosphate, and polyphosphoric acid; common potassium fertilizer raw materials include potassium monohydrogen phosphate, potassium dihydrogen phosphate, potassium chloride, and potassium nitrate.

[0003] Traditional liquid fertilizers often use potassium monohydrogen phosphate (KH2PO4) or potassium dihydrogen phosphate (KD2PO4) as phosphorus and potassium sources, dissolved in water before application. This process is complex, reliant on manual labor, and difficult to standardize. Furthermore, traditional KH2PO4 and KD2PO4 are inorganic fertilizers with poor affinity for leaves, resulting in low absorption and utilization rates. Strict concentration control is required when applying them to leaves to prevent leaf burn. Potassium phosphate salts are relatively unstable in solution, potentially crystallizing and releasing free phosphate ions that can precipitate with micronutrients such as calcium, magnesium, iron, and aluminum, affecting crop absorption. Patent CN109627087A addresses this by compounding urea-formaldehyde nitrogen solution with specific water-soluble phosphate and potassium fertilizers and adding stabilizers to achieve a clear liquid fertilizer with a lower crystallization temperature. However, this approach relies heavily on a specific formulation system; combining it with other fertilizers or pesticides can disrupt the system's stability, thus failing to fundamentally solve the problems of stability and absorption of liquid phosphate fertilizers. Patent CN116693342B proposes to polymerize phosphoric acid with urea to obtain polyphosphate in order to improve the water solubility and stability of phosphorus. However, the polyphosphate molecules are large, resulting in poor foliar spreading when applied to leaves. Furthermore, after absorption by plants, it needs to be converted into phosphate esters before it can be utilized, leading to low absorption and utilization efficiency.

[0004] Therefore, there is an urgent need for a liquid phosphate fertilizer that can balance stability, high solubility, and efficient absorption to meet the needs of modern agricultural development. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide an organic potassium phosphate liquid fertilizer that is highly stable, does not easily precipitate, has a high absorption and utilization rate, good leaf affinity, and high safety.

[0006] On the other hand, the present invention also aims to provide a simple method for preparing the above-mentioned organic potassium phosphate liquid fertilizer.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] An organic potassium phosphate liquid fertilizer, comprising at least one potassium phosphate compound selected from formulas I to V;

[0009]

[0010] Formula I Formula II

[0011]

[0012] Formula III Formula IV

[0013]

[0014] Formula V;

[0015] Formula I is potassium dihydrogen bisphosphate ethylene glycol ester;

[0016] Formula II is potassium monohydrogen bisphosphate 1,3-propanediol ester;

[0017] Formula III is potassium monohydrogen bisphosphate 1,4-butanediol ester;

[0018] Formula IV is potassium dihydrogen bisphosphate diethylene glycol ester;

[0019] Formula V is potassium dihydrogen glyceride.

[0020] Another aspect of the present invention provides a method for preparing the above-mentioned organic potassium phosphate liquid fertilizer, comprising the following steps: esterification reaction of phosphoric acid with the corresponding diol or triol to obtain the corresponding diphosphate ester, and then neutralization reaction with potassium carbonate or potassium hydroxide to form a salt.

[0021] Preferably, the phosphoric acid can be phosphoric acid powder, molten phosphoric acid, or an aqueous solution of phosphoric acid; specifically, the concentration of the aqueous solution of phosphoric acid is 70% to 85%.

[0022] Preferably, cooling water is introduced during the neutralization reaction to lower the temperature, controlling the reaction temperature between 20 and 60°C; more preferably, it is controlled below 50°C. The neutralization reaction releases a large amount of heat. To ensure process safety and prevent alcohol volatilization, the temperature must be controlled below 50°C. If the temperature exceeds 50°C, the reaction becomes too vigorous and cannot be implemented in industrial production. Furthermore, at high temperatures, unreacted diols or triols will react with potassium carbonate or potassium hydroxide to produce byproducts, which not only reduces the yield but also easily damages the stability of the system and causes toxicity to plants.

[0023] Preferably, an aqueous solution of potassium carbonate or potassium hydroxide is added to the neutralization reaction; wherein the molar ratio of potassium carbonate to bisphosphonate is 1:1 (bisphosphonate is in 100% yield); or the molar ratio of potassium hydroxide to bisphosphonate is 2:1 (bisphosphonate is in 100% yield).

[0024] Preferably, the diol or triol is selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, or glycerol.

[0025] Preferably, the molar ratio of H3PO4 to diol or triol in the esterification reaction is 1.5:1 to 2:1. More preferably, the molar ratio of H3PO4 to diol or triol in the esterification reaction is 2:1. By controlling the amount of phosphoric acid, the two terminal hydroxyl groups of the diol or triol are ensured to undergo esterification with phosphoric acid, thereby forming a stable structure of diphosphate. This not only increases the phosphorus and potassium content in the final liquid fertilizer, but also improves the wetting and spreading performance of diphosphate on the leaf surface, which is beneficial to improving the absorption and utilization rate of nutrients by plants. If the molar ratio of H3PO4 to diol or triol is less than 1.5:1, the yield of diphosphate is low, and the product contains a large amount of active diol or triol and monophosphate, resulting in poor stability. If the molar ratio of H3PO4 to diol or triol exceeds 2:1, the excess phosphoric acid exists in a free form, which is not conducive to the stability of the system, and the inorganic potassium phosphate is not easily absorbed and utilized by plants.

[0026] Preferably, the reaction pathway for the specific preparation steps is as follows (the equations for the neutralization reactions of the bisphosphate with potassium carbonate or potassium hydroxide in the reaction pathway are listed separately):

[0027] The reaction pathway for potassium dihydrogen bisphosphate ethylene glycol ester is as follows:

[0028] ;

[0029] or ;

[0030] The reaction pathway of potassium monohydrogen phosphate 1,3-propanediol ester is as follows:

[0031] ;

[0032] or ;

[0033] The reaction pathway of potassium monohydrogen phosphate 1,4-butanediol ester is as follows:

[0034] ;

[0035] or ;

[0036] The reaction pathway of potassium dihydrogen bisphosphate diethylene glycol ester is as follows:

[0037] ;

[0038] or ;

[0039] The reaction pathway of potassium dihydrogen phosphate is as follows:

[0040] ;

[0041] or .

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The organic potassium phosphate liquid fertilizer of the present invention is a small molecule organic liquid phosphate fertilizer that can be absorbed by roots and has good affinity with leaves, effectively improving the absorption of nutrients by plants and increasing the utilization rate of fertilizer; it can be adapted to a variety of fertilization methods and has more diverse application scenarios.

[0044] 2. The potassium diphosphate fertilizer designed and synthesized in this invention has a simple preparation process, which only requires esterification and neutralization reactions. The raw materials are simple and there are no harmful by-products. The pH of the prepared product is usually 5-7, which can be used directly as a liquid fertilizer. It overcomes the complicated process of traditional liquid fertilizers that require solid-state dissolution and mixing and the solubility problem therein. It is more convenient and efficient to use, and it is less likely to burn leaves when applied at high concentrations. It is also more flexible and safer to use.

[0045] 3. The potassium diphosphate liquid fertilizer designed in this invention is stable in nature. It is not easy to form precipitates with metal ions, and it can be mixed with a variety of pesticides. The use of pesticides and fertilizers can effectively improve the efficiency of daily field management and reduce application costs.

[0046] 4. This invention uses potassium dihydrogen phosphate instead of traditional potassium monohydrogen phosphate and potassium dihydrogen phosphate as phosphate fertilizer. Phospholipids are the final form of phosphorus utilization by plants, meaning they can be absorbed and utilized by plants without conversion. On the one hand, they are effective quickly, and on the other hand, they improve the absorption and utilization rate of plants, which meets the policy requirements of "reducing fertilizer and increasing efficiency". Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and should not be used to limit the scope of protection of the present invention.

[0048] Example 1

[0049] This embodiment provides an organic potassium phosphate liquid fertilizer, comprising potassium monohydrogen phosphate ethylene glycol ester, which is prepared by the following method:

[0050] In a reactor, 85% phosphoric acid and ethylene glycol are mixed in a molar ratio of H3PO4 to ethylene glycol of 2:1 to carry out an esterification reaction to obtain ethylene glycol diphosphate. After the reaction is completed, a saturated potassium carbonate solution is added to the reactor, wherein the molar ratio of potassium carbonate to ethylene glycol diphosphate is 1:1 (based on a 100% yield of ethylene glycol diphosphate). The cooling water is turned on, and the reaction temperature is controlled below 50°C for a neutralization reaction of 30 minutes to obtain the final product.

[0051] Example 2

[0052] This embodiment provides an organic potassium phosphate liquid fertilizer, comprising 1,3-propanediol bisphosphate monohydrogen ester, which is prepared by the following method:

[0053] In a reaction vessel, 85% phosphoric acid and 1,3-propanediol were mixed in a molar ratio of H3PO4:1 to 1,3-propanediol and subjected to an esterification reaction to obtain 1,3-propanediol diphosphate. After the reaction was completed, a saturated potassium hydroxide solution was added to the reaction vessel, wherein the molar ratio of potassium hydroxide to 1,3-propanediol diphosphate was 2:1 (based on a 100% yield of 1,3-propanediol diphosphate). The cooling water was turned on, and the reaction temperature was controlled below 50°C for a neutralization reaction of 30 minutes to obtain the final product.

[0054] Example 3

[0055] This embodiment provides an organic potassium phosphate liquid fertilizer, comprising potassium monohydrogen phosphate 1,4-butanediol ester, which is prepared by the following method:

[0056] In a reactor, 85% phosphoric acid and 1,4-butanediol were mixed in a molar ratio of H3PO4:1 to 1,4-butanediol and subjected to an esterification reaction to obtain 1,4-butanediol diphosphate. After the reaction was completed, a saturated potassium hydroxide solution was added to the reactor, wherein the molar ratio of potassium hydroxide to 1,4-butanediol diphosphate was 2:1 (based on a 100% yield of 1,4-butanediol diphosphate). The cooling water was turned on, and the reaction temperature was controlled below 50°C for a neutralization reaction of 30 minutes to obtain the final product.

[0057] Example 4

[0058] This embodiment provides an organic potassium phosphate liquid fertilizer, comprising potassium dihydrogen bisphosphate diethylene glycol ester, which is prepared by the following method:

[0059] In a reaction vessel, 85% phosphoric acid and diethylene glycol are mixed in a molar ratio of H3PO4:diethylene glycol of 2:1 to carry out an esterification reaction to obtain diethylene glycol diphosphate. After the reaction is completed, a saturated potassium hydroxide solution is added to the reaction vessel, wherein the molar ratio of potassium hydroxide to diethylene glycol diphosphate is 2:1 (based on a 100% yield of diethylene glycol diphosphate). The cooling water is turned on, and the reaction temperature is controlled below 50°C for a neutralization reaction of 30 minutes to obtain the final product.

[0060] Example 5

[0061] This embodiment provides an organic potassium phosphate liquid fertilizer, comprising potassium glycerol dihydrogen phosphate, which is prepared by the following method:

[0062] In a reaction vessel, 85% phosphoric acid and glycerol are mixed in a molar ratio of H3PO4 to glycerol of 2:1 and subjected to esterification to obtain glyceryl diphosphate. After the reaction is completed, a saturated potassium carbonate solution is added to the reaction vessel, wherein the molar ratio of potassium carbonate to glyceryl diphosphate is 1:1 (based on a 100% yield of glyceryl diphosphate). The cooling water is turned on, and the reaction temperature is controlled below 50°C. The neutralization reaction is carried out for 30 minutes to obtain the final product.

[0063] Performance testing

[0064] Field Trial 1

[0065] Test location: Pingyuan County, Dezhou City, Shandong Province

[0066] Experimental crop: maize

[0067] Crop variety: Zhengdan 958

[0068] Planting time: Sowing on June 25, 2024

[0069] Planting area: 10 mu

[0070] Planting plan and field management: 4500-5000 plants per mu, and apply 50 kg of Maoshi controlled-release fertilizer (25-5-10 controlled-release fertilizer) per mu as base fertilizer during the period.

[0071] The experiment was set up with 6 treatments:

[0072] Treatment 1: Control group. During the male elongation period, potassium dihydrogen phosphate solution was sprayed on the leaves by drone (100g of potassium dihydrogen phosphate dissolved in 2L of water per acre). The spraying was repeated once after an interval of 10 days.

[0073] Treatments 2-6: Experimental groups, each of which was sprayed with diluted organic potassium phosphate liquid fertilizer of Examples 1-5 (all diluted with water to a phosphorus content (P2O5) of 2.5%) by drone during the male emergence period, with 2L sprayed per acre, and the spraying was repeated once after an interval of 10 days.

[0074] Set up a blank control (CK): spray the same amount of clean water as the treatment group at the same time via drone.

[0075] Other field management practices were carried out according to local farmers' habits, and the management methods for each treatment remained consistent. Harvest was conducted on October 24th, and the statistical results are shown in Table 1.

[0076] Table 1

[0077] CK Process 1 Process 2 Process 3 Process 4 Process 5 Process 6 Yield / kg / mu 488.4 507.2 534.6 542.5 538.2 533.4 533.7 Number of grains per ear / grains per ear 478.5 490.3 492.2 491.4 494.6 462.4 462.2 1000-grain weight / g 250.2 253.5 266.2 270.1 266.7 282.7 283.1

[0078] Based on the actual yield results, the organic potassium phosphate liquid fertilizer of this invention has a significant yield-increasing effect on maize, increasing yield by 5% to 7% compared to the traditional use of potassium dihydrogen phosphate fertilizer. The fullness of maize kernels is improved, with the thousand-kernel weight increasing to over 280g, and the fruit quality is better, indicating that the organic potassium phosphate liquid fertilizer can be absorbed and utilized by maize more efficiently, thereby improving yield and quality. The experimental field applying 1,3-propanediol potassium dihydrogen phosphate showed the highest yield and relatively higher thousand-kernel weight, possibly related to its better affinity with maize leaves due to its molecular structure. Furthermore, leaf burn was observed in maize plants in treatment group 1, while no obvious leaf burn was observed in treatments 2-6, indicating that the organic potassium phosphate liquid fertilizer is milder and safer.

[0079] Field Trial 2

[0080] Test location: Guichi District, Chizhou City, Anhui Province

[0081] Experimental crop: Rice

[0082] Crop variety: Y Liangyou 900

[0083] Planting time: Sowing on June 5, 2024

[0084] Planting area: 10 mu

[0085] Planting plan and field management: The seed and fertilizer are sown together with the seed and fertilizer. During the planting period, 50 kg of controlled-release fertilizer (29-10-12 controlled-release fertilizer) per mu is applied as base fertilizer.

[0086] The experiment was set up with 6 treatments:

[0087] Treatment 1: Control group. During the heading stage of rice, potassium dihydrogen phosphate solution was sprayed on the leaves by drone (100g of potassium dihydrogen phosphate dissolved in 2L of water per mu). The spraying was repeated once after an interval of 10 days.

[0088] Treatments 2-6: Experimental groups, each of the following was sprayed with diluted organic potassium phosphate liquid fertilizers from Examples 1-5 (all diluted with water to a phosphorus content (P2O5) of 2.5%) via drone spraying during the heading stage of rice. 2L per mu was sprayed, and the spraying was repeated once after an interval of 10 days.

[0089] Set up a blank control (CK): spray the same amount of clean water as the treatment group at the same time via drone.

[0090] Other field management during this period was carried out according to local farmers' habits, and the management methods for each treatment remained consistent. Harvest was conducted on October 8th, and the statistical results are shown in Table 2.

[0091] Table 2

[0092] CK Process 1 Process 2 Process 3 Process 4 Process 5 Process 6 Yield / kg / mu 461.5 472.1 501.4 505.8 502.9 506.4 502.6 1000-grain weight / g 22.1 22.2 22.6 23.8 23.5 22.7 23.2 number of grains per ear 197.1 198.4 196.4 185.4 190.6 193.5 189.2 Fruit set rate % 75.5 76.4 80.4 81.6 80.2 82.5 81.7

[0093] The results above indicate that the organic potassium phosphate liquid fertilizer of this invention is suitable for rice, exhibiting a significant yield-increasing effect. Compared to using potassium dihydrogen phosphate, it increases yield by 6% to 7.3%, and improves the grain filling rate by nearly 8%. It is also safer for crops and has a high absorption and utilization rate. Considering the thousand-grain weight and number of grains per panicle, rice treated with the organic potassium phosphate liquid fertilizer of this invention is fuller, demonstrating that the organic potassium phosphate liquid fertilizer of this invention improves both the yield and quality of rice.

[0094] Field Trial 3

[0095] Test location: Yongqiao District, Suzhou City, Anhui Province

[0096] Experimental crop: wheat

[0097] Crop variety: Zhongxin Wheat 998

[0098] Planting time: Sowing on October 20, 2024

[0099] Planting area: 10 mu

[0100] Planting plan and field management: Sow 26 kg / mu, and apply 40 kg of Maoshi controlled-release fertilizer (26-15-8 controlled-release fertilizer) per mu as base fertilizer.

[0101] The experiment was set up with 6 treatments:

[0102] Treatment 1: Control group. During the heading stage of wheat, potassium dihydrogen phosphate solution was sprayed on the leaves by drone (100g of potassium dihydrogen phosphate dissolved in 2L of water per acre was sprayed). The spraying was repeated once after an interval of 10 days.

[0103] Treatments 2-6: The experimental group was sprayed with diluted organic potassium phosphate liquid fertilizer (all diluted with water to a phosphorus content (P2O5) of 2.5%) from Examples 1-5 by drone at the wheat heading stage. The spraying was repeated once every 10 days.

[0104] Set up a blank control (CK): spray the same amount of clean water as the treatment group at the same time via drone.

[0105] Other field management practices were carried out according to local farmers' habits, and the management methods for each treatment remained consistent. Harvest was conducted on June 5th, and the statistical results are shown in Table 3.

[0106] Table 3

[0107] CK Process 1 Process 2 Process 3 Process 4 Process 5 Process 6 Yield / kg / mu 504.5 521.5 560.2 564.1 561.8 568.2 563.6 1000-grain weight / g 38.9 38.7 40.4 40.5 41.2 40.8 41.1 number of grains per ear 41.2 42.8 44.1 44.2 43.4 44.3 43.6

[0108] The above results indicate that the organic potassium phosphate liquid fertilizer of this invention significantly improves wheat yield and quality, increasing yield from a maximum of 521.5 kg / mu to 568.2 kg / mu, an increase of 8.95%. The thousand-grain weight is significantly improved, with all treatment groups achieving an increase of over 40 g, thus improving quality and economic benefits. Furthermore, the number of grains per ear is also increased, especially since potassium dihydrogen phosphate diethylene glycol ester has a higher affinity for wheat and a higher absorption and utilization rate.

Claims

1. An organic potassium phosphate liquid fertilizer, characterized in that, Including at least one potassium phosphate compound selected from formulas I to V; 2. Formula I is potassium dihydrogen bisphosphate ethylene glycol ester; Formula II is potassium monohydrogen bisphosphate 1,3-propanediol ester; Formula III is potassium monohydrogen bisphosphate 1,4-butanediol ester; Formula IV is potassium dihydrogen bisphosphate diethylene glycol ester; Formula V is potassium dihydrogen glyceride.

3. A method for preparing organic potassium phosphate liquid fertilizer according to claim 1, characterized in that, The process includes the following steps: esterification of phosphoric acid with the corresponding di or triol to obtain the corresponding bisphosphonate, followed by neutralization reaction with potassium carbonate or potassium hydroxide to form a salt. Cooling water is introduced during the neutralization reaction to lower the temperature and control the reaction temperature between 20 and 50°C. The diol or triol is selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, or glycerol.

4. The method for preparing organic potassium phosphate liquid fertilizer according to claim 2, characterized in that, The molar ratio of H3PO4 to diol or triol in the esterification reaction is 1.5:1 to 2:

1.

5. The method for preparing organic potassium phosphate liquid fertilizer according to claim 3, characterized in that, The reaction pathway for the preparation steps is as follows: The reaction pathway for potassium dihydrogen bisphosphate ethylene glycol ester is as follows: ； or ; The reaction pathway of potassium monohydrogen phosphate 1,3-propanediol ester is as follows: ； or ; The reaction pathway of potassium monohydrogen phosphate 1,4-butanediol ester is as follows: ； or ; The reaction pathway of potassium dihydrogen bisphosphate diethylene glycol ester is as follows: ； or ; The reaction pathway of potassium dihydrogen phosphate is as follows: ； or .

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