Humic acid-based coated slow-release potassium chloride and preparation method thereof

Abstract

The invention discloses humic acid-based coated slow-release potassium chloride and a preparation method thereof, and belongs to the technical field of biological slow-release organic and inorganic fertilizers. The fertilizer comprises the following raw materials in parts by weight: 40-55 parts of potassium chloride, 6-8 parts of humic acid, 6-9 parts of urea, 0.5-0.8 part of trace elements and 3.5-5.5 parts of a slow-release porous coating material. According to the invention, ethylenediamine and maleic anhydride are used as raw materials to prepare a functional monomer containing carboxyl and amino groups at the same time, an effective coating material enables the potassium fertilizer to release potassium ions in soil more slowly and uniformly, and the utilization efficiency of potassium is improved. The sustained-release potassium chloride disclosed by the invention has an extremely strong potassium chloride sustained-release effect on one hand, provides sufficient potassium for crops, and can effectively regulate the ecological activity of soil and improve the utilization rate of the potassium on the other hand.

Description

Technical Field

[0001] The invention belongs to the technical field of biological slow-release organic and inorganic fertilizers, and particularly relates to a humic acid-based coated slow-release potassium chloride and a preparation method thereof. Background Art

[0002] The effectiveness of soil potassium to crops depends on its existence form and distribution. In addition to the potassium conversion effect of the soil itself, the biological effectiveness of potassium is also affected by exogenous potassium, which will affect the release and fixation of soil potassium and change the dynamic balance of mutual conversion between potassium forms. If potassium fertilizer is not applied during the crop rotation period, non-exchangeable potassium will be released after the available potassium is absorbed; potassium application can increase the content of water-soluble potassium and exchangeable potassium in the soil and convert it to non-exchangeable potassium. However, traditional potassium chloride and potassium sulfate are easily fixed or converted into non-exchangeable potassium and fixed potassium with lower effectiveness after being applied to the soil, and are easily lost with rainwater leaching or surface runoff, which does not match the potassium demand of crops. Controlled-release potassium chloride can slowly release potassium. After a one-time application, it improves the chlorophyll fluorescence characteristics of crops and increases the available potassium content in the soil, becoming a research hotspot for new potassium fertilizers.

[0003] Controlled-Release Potassium Chloride refers to the use of technical means to slow down the release rate of potassium chloride so that it can continuously supply the nutrients needed by plants to meet the needs of crops throughout the growth cycle. From the perspective of nutrition and environmental protection, the development of controlled-release potassium chloride is of great significance, including the following points: ① Improve fertilizer efficiency. Traditional potassium chloride fertilizers are released at one time, which is difficult to adapt to the changes in the demand for nutrients in various growth stages of plants. Controlled-release potassium chloride can slow down the release rate of potassium elements, so that it can continuously supply the nutrients needed by plants over a long period of time. Therefore, it can improve the utilization efficiency of fertilizers and reduce fertilizer waste. ② Protect the environment. Traditional potassium chloride fertilizers can easily cause soil pollution because their release rate cannot be controlled. Controlled-release potassium chloride can reduce the leaching of chloride ions and the time they remain in the soil, which helps to reduce the overload of chloride ions in the soil, thereby reducing the impact on the environment. ③ Improve crop quality. Traditional potassium chloride fertilizers are prone to burns of crop roots due to their excessively fast release rate, and excessive fertilizer intake also has an adverse effect on crop quality. Controlled-release potassium chloride can control the release rate of potassium and avoid excessive fertilization, thus having a positive effect on crop quality.

[0004] However, the current controlled-release potassium chloride products generally only contain potassium chloride and organic and inorganic sustained-release materials. On the one hand, the function is single, and on the other hand, the sustained-release effect is not ideal and the stability is poor. For example, Chinese patent application CN201810809046.6 discloses a controlled-release potassium chloride with urea as a base coat and a preparation method thereof. The controlled-release potassium chloride with urea as a base coat comprises three layers of materials, the core layer is granular potassium chloride, the middle layer is urea wrapped on the surface of the granular potassium chloride, and the outermost layer is a attapulgite nanocomposite material modified by a silane coupling agent or a surfactant.

[0005] Therefore, developing an efficient slow-release potassium chloride fertilizer is a technical problem that needs to be solved urgently. Summary of the invention

[0006] The present invention aims at the problems existing in the prior art and provides a novel slow-release potassium chloride, which has a strong slow-release effect of potassium chloride and provides sufficient potassium for crops, and can effectively regulate soil ecological activity and improve potassium utilization.

[0007] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0008] A humic acid-based coated slow-release potassium chloride comprises the following raw materials: potassium chloride, humic acid, urea, medium and trace elements and a slow-release porous coating material.

[0009] Furthermore, the weight proportions of the raw materials are: 40-55 parts of potassium chloride, 6-8 parts of humic acid, 6-9 parts of urea, 0.5-0.8 parts of trace elements, and 3.5-5.5 parts of sustained-release porous coating materials.

[0010] Furthermore, the trace elements are one or more of magnesium sulfate, calcium sulfate, sodium molybdate, zinc sulfate, ammonium molybdate, and manganese sulfate.

[0011] Furthermore, the preparation method of the sustained-release porous coating material is:

[0012] (1) Preparation of functional monomer: 50 mL of acetone was placed in a container, and 5 mL of ethylenediamine was added under stirring to obtain a mixture; 10 mL of maleic anhydride in acetone was taken, and after heating at 45-50° C. with stirring to dissolve, the mixture was added dropwise to the mixture, and the reaction was continued for 1 hour, the upper layer of liquid was removed, and the product was dissolved with 30 mL of distilled water, and 80 mL of acetone was added, and the mixture was shaken, and the layers were separated and the lower layer of liquid was collected; the entire solution was then rotary evaporated and dried at 100° C. to obtain a functional monomer;

[0013] (2) Preparation of sustained-release porous coating material: 10 g of hexadecyltrimethylammonium bromide and 25 g of diatomaceous earth were dispersed in 1 L of water. After uniform dispersion, 200 g of functional monomer and 150 g of N,N-methylenebisacrylamide were added and stirred to obtain a mixed solution. 100 mL of rapeseed oil was added to the mixed solution and emulsified at 6000 r / min for 2 min at room temperature. Then 5 g of initiator ammonium persulfate and 0.5 g of cross-linking agent N,N,N,N-tetramethylethylenediamine were added and stirred for 10 min. The mixture was transferred to a sealed container and polymerized in a water bath at 70°C for 24 h to obtain a solid polymer. The polymer was extracted by Soxhlet extraction for 24 h to thoroughly wash off the oil phase. Finally, the mixture was vacuum dried to constant weight to obtain a sustained-release porous coating material.

[0014] Furthermore, the mass concentration of the acetone solution of maleic anhydride in step (1) is 0.5 g / mL.

[0015] A method for preparing humic acid-based coated sustained-release potassium chloride comprises the following preparation steps:

[0016] (1) Potassium chloride, humic acid, urea, and trace elements are placed in a drum and mixed uniformly according to weight to obtain a premix, and the round particles obtained by disk granulation, drum granulation, or spray granulation are preheated to 70-75° C., and sprayed with a 2% by weight polyvinyl alcohol solution and a 5% by weight borax solution;

[0017] (2) under stirring, the sustained-release porous coating material is heated and then sprayed onto the surface of the solid particles, and then sealed with a cellulose acetate solution with a mass concentration of 0.03 g / mL;

[0018] (3) Finally, after drying at 40-55°C, humic acid-coated sustained-release potassium chloride is obtained.

[0019] Furthermore, the amount of the polyvinyl alcohol solution in step (1) is 1-3% of the mass of the premix, and the amount of the borax solution is 3-7% of the mass of the premix.

[0020] Beneficial effects:

[0021] (1) The present invention uses potassium chloride as the main potassium source, and adds nutrient elements such as humic acid, urea, and trace elements as auxiliary materials. Humic acid can activate potassium fertilizer and slowly decompose it, thereby improving the utilization rate of potassium fertilizer by crops. Compared with ordinary oxidized potassium fertilizer, it can better control the release of potassium and prolong its fertilizer effect. Adding a small amount of urea and trace elements in combination can significantly promote crop growth, balance the nutrient elements in the soil, and enhance the disease resistance of crops.

[0022] (2) The present invention uses ethylenediamine and maleic anhydride as raw materials to prepare functional monomers containing both carboxyl and amino groups, and subsequently prepares porous polymer materials by emulsion polymerization. The materials have abundant macropores, micropore structures and surface functional groups, and hydrophilic groups (carboxyl, amino, etc.) can form channels for water molecules to enter and exit the coating, thereby forming a slow-controlled release of fertility. After potassium chloride is coated by the slow-release porous coating material, the moisture in the soil enters the interior through the coating agent channel to form a high-concentration potassium chloride solution, and the carboxyl active group plays the role of a potassium ion porter. The potassium ions coated inside the coating agent diffuse into the soil outside the coating agent through the chelation and release of the carboxyl group, realizing the long-term slow release of nutrients, especially potassium. The amino active group can adsorb and store exchangeable potassium ions through the effects of electrostatic adsorption and π-cation bonds, thereby reducing the loss of potassium and achieving a slow-release effect. The synergistic coordination of these two mechanisms makes the speed at which potassium fertilizer releases potassium ions in the soil slower and more uniform, thereby improving the utilization efficiency of potassium.

[0023] (3) Subsequently, polyvinyl alcohol solution and borax solution are used for encapsulation. The ions in the borax will undergo a cross-linking reaction with the polyvinyl alcohol (PVA) molecules to form a three-dimensional network structure. This structure has good mechanical properties and self-healing ability, which makes the fertilizer particles have good physical properties and slow-release properties.

[0024] (4) Finally, the fertilizer particles are sealed with cellulose acetate solution. The cellulose acetate solution can form a smooth and delicate film that can effectively wrap the fertilizer particles, thereby slowing down the release of nutrients. At the same time, the fertilizer particles coated with cellulose acetate solution have low leaching solubility in the soil, which means that the nutrients in the fertilizer are not easily washed away by rainwater, thereby improving the utilization rate of the fertilizer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The scanning electron microscope images of the sustained-release porous coating material prepared by the present invention, wherein (ac) are three different sampling points of the same sample;

[0026] Figure 2 This is the release curve of the sample of Example 1 of the present invention in still water at 25°C;

[0027] Figure 3 The figures are the results of soil dissolution tests of the embodiments of the present invention and the comparative examples. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below in conjunction with specific embodiments, but is not limited thereto.

[0029] Example 1

[0030] A humic acid-based coated slow-release potassium chloride comprises the following raw materials: potassium chloride, humic acid, urea, trace elements and slow-release porous coating material. The weight proportions of the raw materials are: 40 parts of potassium chloride, 8 parts of humic acid, 6 parts of urea, 0.5 parts of trace elements and 3.5 parts of slow-release porous coating material.

[0031] The trace elements are magnesium sulfate, calcium sulfate, sodium molybdate, zinc sulfate, ammonium molybdate and manganese sulfate mixed in a mass ratio of 10:5:1:0.5:0.3:0.5.

[0032] The preparation method of the sustained-release porous coating material is as follows:

[0033] (1) Preparation of functional monomer: 50 mL of acetone was placed in a container, and 5 mL of ethylenediamine was added under stirring to obtain a mixture; 10 mL of maleic anhydride in acetone was taken, and after heating at 45-50° C. with stirring to dissolve, the mixture was added dropwise to the mixture, and the reaction was continued for 1 hour, the upper layer of liquid was removed, and the product was dissolved with 30 mL of distilled water, and 80 mL of acetone was added, and the mixture was shaken, and the layers were separated and the lower layer of liquid was collected; the entire solution was then rotary evaporated and dried at 100° C. to obtain a functional monomer;

[0034] (2) Preparation of sustained-release porous coating material: 10 g of hexadecyltrimethylammonium bromide and 25 g of diatomaceous earth were dispersed in 1 L of water. After uniform dispersion, 200 g of functional monomer and 150 g of N,N-methylenebisacrylamide were added and stirred to obtain a mixed solution. 100 mL of rapeseed oil was added to the mixed solution and emulsified at 6000 r / min for 2 min at room temperature. Then 5 g of initiator ammonium persulfate and 0.5 g of cross-linking agent N,N,N,N-tetramethylethylenediamine were added and stirred for 10 min. The mixture was transferred to a sealed container and polymerized in a water bath at 70°C for 24 h to obtain a solid polymer. The polymer was extracted by Soxhlet extraction for 24 h to thoroughly wash off the oil phase. Finally, the mixture was vacuum dried to constant weight to obtain a sustained-release porous coating material.

[0035] The mass concentration of the maleic anhydride acetone solution is 0.5 g / mL.

[0036] A method for preparing humic acid-based coated sustained-release potassium chloride comprises the following preparation steps:

[0037] (1) Potassium chloride, humic acid, urea, and trace elements are placed in a drum and mixed uniformly according to weight to obtain a premix, and the round particles obtained by disk granulation, drum granulation, or spray granulation are preheated to 70-75° C., and sprayed with a 2% by weight polyvinyl alcohol solution and a 5% by weight borax solution;

[0038] (2) under stirring, the sustained-release porous coating material is heated and then sprayed onto the surface of the solid particles, and then sealed with a cellulose acetate solution with a mass concentration of 0.03 g / mL;

[0039] (3) Finally, after drying at 40-55°C, humic acid-coated sustained-release potassium chloride is obtained.

[0040] The amount of the polyvinyl alcohol solution in step (1) is 1% of the mass of the premix, and the amount of the borax solution is 3% of the mass of the premix.

[0041] Example 2

[0042] A humic acid-based coated slow-release potassium chloride comprises the following raw materials: potassium chloride, humic acid, urea, trace elements and slow-release porous coating material. The weight proportions of the raw materials are: 44 parts of potassium chloride, 6 parts of humic acid, 8 parts of urea, 0.7 parts of trace elements and 4.5 parts of slow-release porous coating material.

[0043] The trace elements are magnesium sulfate, calcium sulfate and zinc sulfate mixed in a mass ratio of 10:1:0.5.

[0044] The preparation method of the sustained-release porous coating material is as follows:

[0045] (1) Preparation of functional monomer: 50 mL of acetone was placed in a container, and 5 mL of ethylenediamine was added under stirring to obtain a mixture; 10 mL of maleic anhydride in acetone was taken, and after heating at 45-50° C. with stirring to dissolve, the mixture was added dropwise to the mixture, and the reaction was continued for 1 hour, the upper layer of liquid was removed, and the product was dissolved with 30 mL of distilled water, and 80 mL of acetone was added, and the mixture was shaken, and the layers were separated and the lower layer of liquid was collected; the entire solution was then rotary evaporated and dried at 100° C. to obtain a functional monomer;

[0046] (2) Preparation of sustained-release porous coating material: 10 g of hexadecyltrimethylammonium bromide and 25 g of diatomaceous earth were dispersed in 1 L of water. After uniform dispersion, 200 g of functional monomer and 150 g of N,N-methylenebisacrylamide were added and stirred to obtain a mixed solution. 100 mL of rapeseed oil was added to the mixed solution and emulsified at 6000 r / min for 2 min at room temperature. Then 5 g of initiator ammonium persulfate and 0.5 g of cross-linking agent N,N,N,N-tetramethylethylenediamine were added and stirred for 10 min. The mixture was transferred to a sealed container and polymerized in a water bath at 70°C for 24 h to obtain a solid polymer. The polymer was extracted by Soxhlet extraction for 24 h to thoroughly wash off the oil phase. Finally, the mixture was vacuum dried to constant weight to obtain a sustained-release porous coating material.

[0047] The mass concentration of the maleic anhydride acetone solution is 0.5 g / mL.

[0048] A method for preparing humic acid-based coated sustained-release potassium chloride comprises the following preparation steps:

[0049] (1) Potassium chloride, humic acid, urea, and trace elements are placed in a drum and mixed uniformly according to weight to obtain a premix, and the round particles obtained by disk granulation, drum granulation, or spray granulation are preheated to 70-75° C., and sprayed with a 2% by weight polyvinyl alcohol solution and a 5% by weight borax solution;

[0050] (2) under stirring, the sustained-release porous coating material is heated and then sprayed onto the surface of the solid particles, and then sealed with a cellulose acetate solution with a mass concentration of 0.03 g / mL;

[0051] (3) Finally, after drying at 40-55°C, humic acid-coated sustained-release potassium chloride is obtained.

[0052] Furthermore, the amount of the polyvinyl alcohol solution in step (1) is 1% of the mass of the premix, and the amount of the borax solution is 5% of the mass of the premix.

[0053] Example 3

[0054] A humic acid-based coated slow-release potassium chloride comprises the following raw materials: potassium chloride, humic acid, urea, trace elements and slow-release porous coating material. The weight proportions of the raw materials are: 55 parts of potassium chloride, 8 parts of humic acid, 9 parts of urea, 0.8 parts of trace elements and 5.5 parts of slow-release porous coating material.

[0055] The trace elements are magnesium sulfate, calcium sulfate, sodium molybdate, zinc sulfate, ammonium molybdate and manganese sulfate mixed in a mass ratio of 10:6:2:0.3:0.5:0.2.

[0056] The preparation method of the sustained-release porous coating material is as follows:

[0057] (1) Preparation of functional monomer: 50 mL of acetone was placed in a container, and 5 mL of ethylenediamine was added under stirring to obtain a mixture; 10 mL of maleic anhydride in acetone was taken, and after heating at 45-50° C. with stirring to dissolve, the mixture was added dropwise to the mixture, and the reaction was continued for 1 hour, the upper layer of liquid was removed, and the product was dissolved with 30 mL of distilled water, and 80 mL of acetone was added, and the mixture was shaken, and the layers were separated and the lower layer of liquid was collected; the entire solution was then rotary evaporated and dried at 100° C. to obtain a functional monomer;

[0058] (2) Preparation of sustained-release porous coating material: 10 g of hexadecyltrimethylammonium bromide and 25 g of diatomaceous earth were dispersed in 1 L of water. After uniform dispersion, 200 g of functional monomer and 150 g of N,N-methylenebisacrylamide were added and stirred to obtain a mixed solution. 100 mL of rapeseed oil was added to the mixed solution and emulsified at 6000 r / min for 2 min at room temperature. Then 5 g of initiator ammonium persulfate and 0.5 g of cross-linking agent N,N,N,N-tetramethylethylenediamine were added and stirred for 10 min. The mixture was transferred to a sealed container and polymerized in a water bath at 70°C for 24 h to obtain a solid polymer. The polymer was extracted by Soxhlet extraction for 24 h to thoroughly wash off the oil phase. Finally, the mixture was vacuum dried to constant weight to obtain a sustained-release porous coating material.

[0059] The structural characteristics of the sustained-release porous coating material were observed using scanning electron microscopy, such as Figure 1 As shown, the material surface and the whole body present obvious porous structure, which is conducive to the sustained release of nutrients.

[0060] The mass concentration of the maleic anhydride acetone solution is 0.5 g / mL.

[0061] A method for preparing humic acid-based coated sustained-release potassium chloride comprises the following preparation steps:

[0062] (1) Potassium chloride, humic acid, urea, and trace elements are placed in a drum and mixed uniformly according to weight to obtain a premix, and the round particles obtained by disk granulation, drum granulation, or spray granulation are preheated to 70-75° C., and sprayed with a 2% by weight polyvinyl alcohol solution and a 5% by weight borax solution;

[0063] (2) under stirring, the sustained-release porous coating material is heated and then sprayed onto the surface of the solid particles, and then sealed with a cellulose acetate solution with a mass concentration of 0.03 g / mL;

[0064] (3) Finally, after drying at 40-55°C, humic acid-coated sustained-release potassium chloride is obtained.

[0065] The amount of the polyvinyl alcohol solution in step (1) is 3% of the mass of the premix, and the amount of the borax solution is 7% of the mass of the premix.

[0066] Comparative Example 1

[0067] A humic acid-based coated slow-release potassium chloride comprises the following raw materials: potassium chloride, humic acid, urea, trace elements and slow-release porous coating material. The weight proportions of the raw materials are: 40 parts of potassium chloride, 8 parts of humic acid, 6 parts of urea, 0.5 parts of trace elements and 3.5 parts of slow-release porous coating material.

[0068] The preparation method of the sustained-release porous coating material is as follows: 10g of hexadecyltrimethylammonium bromide and 25g of diatomaceous earth are dispersed in 1L of water, and after being evenly dispersed, 200g of acrylic acid and 150g of N,N-methylenebisacrylamide are added, and the mixture is evenly stirred to obtain a mixed solution, 100mL of rapeseed oil is added to the mixed solution, and high-speed shearing emulsification is performed at 6000r / min for 2min under room temperature; 5g of initiator ammonium persulfate and 0.5g of cross-linking agent N,N,N,N-tetramethylethylenediamine are added, and the mixture is transferred to a container and sealed after stirring for 10min, and water-bath polymerized at 70°C for 24h to obtain a solid polymer; the polymer is extracted by Soxhlet extraction for 24h to thoroughly wash off the oil phase, and finally vacuum dried to constant weight to obtain the sustained-release porous coating material.

[0069] In this comparative example, except that conventional acrylic acid is used as a monomer in the preparation method of the sustained-release porous coating material, the other raw materials and preparation method are the same as those in Example 1.

[0070] Comparative Example 2

[0071] A humic acid-based coated slow-release potassium chloride comprises the following raw materials: potassium chloride, humic acid, urea, trace elements and coating materials. The weight proportions of the raw materials are: 40 parts of potassium chloride, 8 parts of humic acid, 6 parts of urea, 0.5 parts of trace elements and 3.5 parts of coating materials.

[0072] The coating material is a common resin, such as epoxy resin.

[0073] A method for preparing humic acid-based coated sustained-release potassium chloride comprises the following preparation steps:

[0074] (1) Potassium chloride, humic acid, urea, and trace elements are placed in a drum and mixed uniformly according to weight to obtain a premix, and the round particles obtained by disk granulation, drum granulation, or spray granulation are preheated to 70-75° C., and sprayed with a 2% by weight polyvinyl alcohol solution and a 5% by weight borax solution;

[0075] (2) under stirring, the epoxy resin is heated and sprayed onto the surface of the solid particles, and then sealed with a cellulose acetate solution with a mass concentration of 0.03 g / mL;

[0076] (3) Finally, after drying at 40-55°C, humic acid-coated sustained-release potassium chloride is obtained.

[0077] In this comparative example, except that epoxy resin is used as the sustained-release material, the other raw materials and preparation methods are the same as those in Example 1.

[0078] Performance Testing

[0079] Fertilizer samples were prepared by the methods of the embodiments and comparative examples, and the potash fertilizer release effect was tested according to the national standard GB / T23348-2009 for slow-release fertilizers. The results are shown in Table 1:

[0080] Table 1 Test results

[0081] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 1d release amount% 1.2 1.1 1.1 4.5 10.2 28d release% 17.8 17.5 17.0 40.2 75.6 140d release% 81.2 81.5 80.6 89.6 95.8

[0082] The potassium release characteristics of the sample in Example 1 were further tested by using the static water nutrient extraction method (25°C) in an indoor incubator. The potassium release characteristics were determined according to the method specified in the Chemical Industry Standard of the People's Republic of China "Controlled Release Fertilizer" "HG / T4215-2011". The results are as follows: Figure 2 shown.

[0083] Soil dissolution performance test:

[0084] Evenly bury 5g of the sample to be tested in 5kg of soil in a polyethylene barrel, and then seal the polyethylene barrel with a black plastic bag to reduce evaporation and loss of water. Sample the soil within a specified time and dry it to constant weight in an electric blast drying oven, then crush it, and the drying temperature is 105℃. Put 2g of crushed soil, 40mL of soil extractant and an appropriate amount of soil decolorizer in a 100ml conical flask, react for 3min under vigorous shaking, and then test the soil soluble potassium content using a G-61 flame photometer. Figure 3 It can be seen that pure granular potassium chloride is quickly released in the soil, and is completely released after a release time of 20-30 days. However, the release period of the potash fertilizer of the embodiment of the present invention is significantly extended, and nutrients are still released until the release time reaches 80 days, which has excellent slow-release performance.

[0085] Field soil slow-release performance test:

[0086] Among various crops, tobacco fields have a higher requirement for potassium fertilizer content, so tobacco fields were selected as the test object. Samples were applied to the land planted with tobacco leaves at a fertilizer rate of 20kg / mu, and soils with depths of 10cm, 20cm, 30cm and 40cm were taken at intervals, dried at 105℃ and crushed, and then the available potassium content of the soil was measured.

[0087] Table 2 Soil available potassium content mg / kg

[0088] 10cm 20cm 30cm 40cm Example 1 108.9 179.8 98.5 25.2 Example 2 106.5 178.5 97.2 23.5 Example 3 107.2 185.2 98.1 24.3 Comparative Example 1 105.6 165.2 190.5 210.5 Comparative Example 2 106.2 167.9 215.5 251.3

[0089] From the data in Table 2, we can see that when the soil depth is 10-20cm, there is not much difference between the quick-acting potassium content of the embodiment and the comparative example soil. As the soil depth increases, the potassium shows an increasing trend when the comparative example group slow-release fertilizer is used. The reason for this change is that after the sample enters the soil, the potassium release rate is relatively fast, and it is released into the deep soil, causing the loss of potash fertilizer. The nutrient release rate of the coated slow-release potash fertilizer of the embodiment is relatively slow, and the release cycle is relatively close to the fertilizer cycle of tobacco leaves, and most of the potash fertilizer is absorbed by tobacco leaves, so only a small amount of potash fertilizer nutrients are lost. An investigation of the local tobacco planting situation found that the limit depth of the nutrient absorption of tobacco leaves roots is 20cm, and the nutrients exceeding 20cm in the soil depth cannot be absorbed by tobacco leaves, that is, it will form a waste of resources, and the coated slow-release potash fertilizer maintains a higher quick-acting potassium content between the soil depth of 10cm-20cm, and the quick-acting potassium content is less after exceeding 20cm, which has a positive impact on tobacco leaf growth and reducing resource waste, showing good field slow-release performance.

[0090] After the tobacco leaves were harvested, they were baked according to the three-stage baking method and graded according to the national standard for flue-cured tobacco 42 grades (GB2635-92). 1.5 kg of tobacco leaves of grade X2F and grade were taken respectively, and the total nitrogen, potassium, nicotine and total sugar content of the tobacco leaves were measured respectively. The tobacco industry standards YC / T1612002, YC / T173-2003, YC / T160-2002 and YC / T159-2002 were used for determination. The samples were applied at a fertilizer rate of 20 kg / mu in the embodiments and comparative examples, and the blank control was not treated in any way. All experimental groups were repeated five times, and the results were averaged. The results are shown in Table 3:

[0091] Table 3 Analysis of chemical components in tobacco leaves after different treatments

[0092]

[0093]

[0094] By applying the slow-release fertilizer of the embodiment of the present invention, potassium is effectively utilized, which not only reduces the nicotine content in tobacco leaves, but also increases the total nitrogen content to varying degrees, thereby achieving the purpose of coordinating the chemical components in tobacco leaves and indirectly improving the quality of flue-cured tobacco and tobacco leaves.

[0095] It should be noted that the above embodiments are only partial embodiments of the preferred methods of implementing the present invention, rather than all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

Claims

1. A humic acid-coated sustained-release potassium chloride, characterized in that: The invention comprises the following raw materials: potassium chloride, humic acid, urea, medium and trace elements and slow-release porous coating materials.

2. The humic acid-coated sustained-release potassium chloride according to claim 1, characterized in that: The raw materials are respectively as follows by weight: 40-55 parts of potassium chloride, 6-8 parts of humic acid, 6-9 parts of urea, 0.5-0.8 parts of trace elements, and 3.5-5.5 parts of slow-release porous coating materials.

3. The humic acid-coated sustained-release potassium chloride according to claim 1, characterized in that: The trace elements are one or more of magnesium sulfate, calcium sulfate, sodium molybdate, zinc sulfate, ammonium molybdate and manganese sulfate.

4. The humic acid-coated sustained-release potassium chloride according to claim 1, characterized in that: The preparation method of the sustained-release porous coating material is as follows: (1) Preparation of functional monomer: 50 mL of acetone was placed in a container, and 5 mL of ethylenediamine was added under stirring to obtain a mixture; 10 mL of maleic anhydride in acetone was taken, and after heating at 45-50° C. with stirring to dissolve, the mixture was added dropwise to the mixture, and the reaction was continued for 1 hour, the upper layer of liquid was removed, and the product was dissolved with 30 mL of distilled water, and 80 mL of acetone was added, and the mixture was shaken, and the layers were separated and the lower layer of liquid was collected; the entire solution was then rotary evaporated and dried at 100° C. to obtain a functional monomer; (2) Preparation of sustained-release porous coating material: 10 g of hexadecyltrimethylammonium bromide and 25 g of diatomaceous earth were dispersed in 1 L of water. After uniform dispersion, 200 g of functional monomer and 150 g of N,N-methylenebisacrylamide were added and stirred to obtain a mixed solution. 100 mL of rapeseed oil was added to the mixed solution and emulsified at 6000 r / min for 2 min at room temperature. Then 5 g of initiator ammonium persulfate and 0.5 g of cross-linking agent N,N,N,N-tetramethylethylenediamine were added and stirred for 10 min. The mixture was transferred to a sealed container and polymerized in a water bath at 70°C for 24 h to obtain a solid polymer. The polymer was extracted by Soxhlet extraction for 24 h to thoroughly wash off the oil phase. Finally, the mixture was vacuum dried to constant weight to obtain a sustained-release porous coating material.

5. The humic acid-coated sustained-release potassium chloride according to claim 4, characterized in that: The mass concentration of the acetone solution of maleic anhydride in step (1) is 0.5 g / mL.

6. A method for preparing the humic acid-coated sustained-release potassium chloride according to any one of claims 1 to 5, characterized in that: The method comprises the following preparation steps: (1) Potassium chloride, humic acid, urea, and trace elements are placed in a drum and mixed uniformly according to weight to obtain a premix, and the round particles obtained by disk granulation, drum granulation, or spray granulation are preheated to 70-75° C., and sprayed with a 2% by weight polyvinyl alcohol solution and a 5% by weight borax solution; (2) under stirring, the sustained-release porous coating material is heated and then sprayed onto the surface of the solid particles, and then sealed with a cellulose acetate solution with a mass concentration of 0.03 g / mL; (3) Finally, after drying at 40-55°C, humic acid-coated sustained-release potassium chloride is obtained.

7. The method for preparing the humic acid-coated sustained-release potassium chloride according to claim 6, characterized in that: The amount of the polyvinyl alcohol solution in step (1) is 1-3% of the mass of the premix, and the amount of the borax solution is 3-7% of the mass of the premix.

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