A slow-release agent for fertilizer, slow-release fertilizer and preparation method thereof

Abstract

The present invention relates to a slow-release agent for fertilizer, a slow-release fertilizer, and a preparation method thereof, characterized in that starch, phosphate, and urea are added to water, reacted for 2 to 4 hours at a temperature of 95 to 120° C. and a pressure of 0 to 2 MPa, cooled to 20 to 50° C., Bacillus sp. is added, and the mixture is dried to obtain the slow-release agent for fertilizer. The slow-release agent for fertilizer obtained in the present application has a good slow-release effect when used in fertilizers.

Description

Technical Field

[0001] The invention relates to a slow-release agent for fertilizer, a slow-release fertilizer and a preparation method thereof. Background Art

[0002] Currently, there are two types of slow-release fertilizers: one that achieves a slow-release effect by blocking the fertilizer's contact with the outside world through coating, and the other by adding urease inhibitors or nitrification inhibitors to inhibit enzyme activity. However, coatings are affected by the coating material, some of which are difficult to degrade and can remain in the soil, contaminating it. Inhibitors, such as dicyandiamide, are drugs that not only inhibit nitrite-producing bacteria but also affect other bacteria, disrupting the microecological balance.

[0003] For example, the patent name is a method for preparing a phosphate-carbamate starch ester coated urea slow-release fertilizer, and the patent number is CN 110723990. It provides the following steps: starch, phosphate and urea are mixed uniformly, and then ground to obtain a mixed powder; the mixed powder is transferred to a reactor, and then anhydrous ethanol and deionized water are added to the reactor, and then the reactor is sealed for esterification to obtain a crude phosphate-carbamate starch ester, the crude phosphate-carbamate starch ester is washed 3 times with anhydrous ethanol, and then dried at 60°C for 60 minutes, and then ground for 60 minutes, and finally dried at 60°C for 90 minutes to obtain a phosphate-carbamate starch ester; 20.25g of ethyl cellulose is added to 20mL of distilled water, and then the mixture is stirred at a temperature of 80°C for 2 hours.

[0004] The mixture was stirred at a speed of 500 r / min for 50 minutes to obtain a cellulose dispersion; 10 mL of glycerol, 5 mL of a 40% formaldehyde solution by mass and 5.010 g of sodium hydroxide were added to the cellulose dispersion, and the mixture was stirred at a temperature of 80° C. and a stirring speed of 1000 r / min for 30 minutes, and then cooled to room temperature to obtain an ethyl cellulose binder solution; urea was immersed in the ethyl cellulose binder solution for 40 minutes, and then taken out to obtain urea with a cellulose binder on the surface; the urea with a cellulose binder on the surface was mixed with phosphoric acid-carbamic acid starch ester and added to a rotary evaporator, and then distilled under reduced pressure at a temperature of 50° C. and a pressure of 0.05 MPa for 90 minutes; and its specification 0027 records the present invention The invention provides a method for preparing a phosphate-carbamate starch ester coated urea slow-release fertilizer. The method comprises spraying an ethyl cellulose binder and phosphate-carbamate starch ester on the surface of urea, and controlling the concentration of phosphate-carbamate starch ester, the mass of phosphate-carbamate starch ester, and the thickness of multiple coating layers to obtain a phosphate-carbamate starch ester coated urea slow-release fertilizer with different release rates in water or soil. The method can extend the urea release time and improve the environmental pollution of urea. In addition, the starch derivative can be degraded under natural conditions to form nutrients, thereby avoiding the coating material from being damaged.

[0005] Secondary pollution.

[0006] It can be seen that urea slow-release fertilizer is obtained by coating, which prolongs the urea release time and improves the pollution of urea to the environment. In addition, starch derivatives can be degraded under natural conditions to form nutrients, avoiding the problem of secondary pollution of the coating material. However, the process of preparing slow-release fertilizer is extremely complicated and requires coating 2-8 times.

[0007] What is particularly important is that the urea prepared is coated urea, which is used in water-soluble fertilizers because the adhesion of the film affects the dissolution of urea. Even if the urea is dissolved, the film is still present in the water, and there is a problem of clogging the drip tube eye when used in drip irrigation.

[0008] Water-soluble fertilizers are different from chemical fertilizers. Commonly referred to as water-soluble fertilizers are fast-acting and are mainly applied to shallow-rooted crops such as vegetables. The fertilization interval is short, so fast-acting is required. Since drip irrigation saves both water and fertilizer, water-soluble fertilizers have been applied to field crops. Due to its geographical location, Gansu has been short of water all year round, and drip irrigation equipment for field crops is more widely used. Field crops have relatively deep roots, and watering cannot be as frequent as vegetables. Therefore, the market needs water-soluble fertilizers with simple preparation methods and slow-release effects suitable for field crops. Summary of the Invention

[0009] The present invention provides a slow-release agent for fertilizer, a slow-release fertilizer and a preparation method thereof, and solves the following technical problems: 1) the water-soluble fertilizer is suitable for field crops, has good slow-release effect, and can increase crop yield.

[0010] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0011] A method for preparing a slow-release agent for fertilizer is carried out according to the following steps:

[0012] Add starch, phosphate and urea to water, react for 2 to 4 hours at a temperature of 95 to 120°C and a pressure of 0 to 2 MPa, cool to 20 to 50°C, add Bacillus, stir evenly, and dry to obtain a slow-release agent for fertilizer.

[0013] The mass ratio of starch, phosphate, urea, bacillus and water is 30-50:3-15:0.02-0.6:0.2-10:35-67;

[0014] The Bacillus is capable of degrading starch.

[0015] The phosphate is one or more of potassium dihydrogen phosphate, sodium dihydrogen phosphate, sodium pyrophosphate, potassium pyrophosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, disodium hydrogen phosphate and dipotassium hydrogen phosphate; the Bacillus is one or both of Bacillus amyloliquefaciens and Bacillus subtilis.

[0016] The water is one or both of deionized water and distilled water.

[0017] The total mass fraction of phosphate and urea in the slow-release agent for fertilizer is not greater than 6%; the mesh size of the slow-release agent for fertilizer is greater than or equal to 200 meshes.

[0018] The drying temperature is 40-60° C. and the drying is performed until the moisture content is less than 0.4%.

[0019] The invention relates to a preparation method of a slow-release fertilizer containing a slow-release agent for fertilizer. The slow-release agent for fertilizer is added into the fertilizer and mixed evenly to obtain the slow-release fertilizer.

[0020] The mass ratio of slow-release agent to fertilizer is 0.1-5:95-99.9;

[0021] The nitrogen content of the fertilizer is less than or equal to 20%;

[0022] The fertilizer is a water-soluble fertilizer.

[0023] Also includes granulation.

[0024] The granulation temperature should be lower than 70°C.

[0025] The invention has the following beneficial technical effects:

[0026] 1) This application modifies starch by using phosphate. The modified starch introduces phosphate groups with anionic properties. Therefore, compared with starch, it has better adsorption and hydrophilicity to cations. Nitrogen in fertilizers is highly mobile and easily lost. Therefore, the current slow-release fertilizers mainly release nitrogen fertilizers slowly. Take urea as an example. When it is applied to the soil, amide nitrogen is converted into ammonium nitrogen under the action of urease, forming ammonium carbonate or ammonium bicarbonate. Ammonium carbonate or ammonium bicarbonate is easy to volatilize, resulting in nitrogen loss. The modified starch in this application has better adsorption to cations, that is, it adsorbs NH4 + Thereby reducing the loss of nitrogen and playing a role of slow release, thus having a better slow release effect.

[0027] 2) This application ultimately limits the total mass fraction of phosphate and urea in the slow-release agent for fertilizer to no more than 6%. This is to prevent the salt concentration from being too high during the drying process, causing the Bacillus spores to dehydrate during the drying process, resulting in the inhibition of Bacillus spore growth or even death. As a result, the nutrients fixed in the slow-release agent for fertilizer cannot be released in a timely manner, and the nutrient utilization rate of the fertilizer cannot be improved.

[0028] 3) In this application, the amount of phosphate added is relatively small because the mass fractions of phosphate and urea in the system need to be controlled. Therefore, the water used in this application is required to be deionized water or distilled water, thereby reducing the competition of calcium and magnesium ions in the water for phosphate and improving the utilization rate of the reaction between phosphate and starch.

[0029] 4) In this application, after cooling, Bacillus amyloliquefaciens is added and stirred evenly, so that the modified starch pre-embeds the Bacillus, improving the compatibility of the Bacillus with the fertilizer. Fertilizers have a high salt concentration, with a salt concentration of 10% having a good bactericidal effect, which limits the compatibility of bacteria with fertilizers. However, pre-embedding the Bacillus with the modified starch can prevent direct contact between the Bacillus and fertilizer, thereby improving the compatibility of the Bacillus with fertilizers.

[0030] 5) During preparation, the slow-release fertilizer must be dried to a moisture content of less than 0.4%, thereby placing the Bacillus spores in a dormant state and ensuring the stability of the slow-release fertilizer. When the slow-release fertilizer is applied to the soil, the phosphate-modified starch absorbs water, activating the pre-embedded Bacillus spores. The Bacillus spores then degrade the modified starch, gradually releasing the nutrients immobilized by the slow-release fertilizer, achieving a sustained and sufficient release effect.

[0031] This application's sustained-release mechanism:

[0032] a) The slow-release agent for fertilizer prepared in the present application has high water absorption and adsorption properties, and thus has the effect of retaining water and fertilizer.

[0033] b) Slow-release mechanism of urea: Under normal circumstances, it takes 4 to 7 days for urea to be completely converted into ammonium nitrogen.

[0034] The higher the soil temperature, the faster the conversion; when the soil temperature is 30°C, the conversion only takes 2 to 3 days, and when the soil temperature is 10°C, it takes 7 to 10 days to completely convert into ammonium nitrogen. The slow-release agent for fertilizer prepared in this application mainly adsorbs urea and adsorbs the ammonium nitrogen produced by urea degradation. Due to the high aging stability of phosphate-modified starch, the adsorbed ammonium nitrogen is not easy to release, which will also cause the nitrogen utilization rate to decrease. Therefore, this application adds Bacillus that can degrade starch to degrade the phosphate-modified starch to release its fixed fertilizer nutrients, thereby improving the utilization rate of fertilizer nutrients. Of course, this nutrient release also includes the release of phosphate. DETAILED DESCRIPTION

[0035] In order to better understand the above technical solution, the technical solution of the present invention is described in detail below with reference to preferred examples. Example 1

[0036] A method for preparing a slow-release agent for fertilizer is carried out according to the following steps:

[0037] Add starch, phosphate and urea to water, react at 100°C for 3 hours, cool to 40°C, add Bacillus subtilis, stir evenly, and dry to obtain a slow-release agent for fertilizer;

[0038] The mass ratio of starch, phosphate, urea, Bacillus subtilis and water is 40:5:0.3:1:53.7;

[0039] The phosphate is a composition of potassium dihydrogen phosphate and potassium pyrophosphate in a mass ratio of 2:1; the Bacillus subtilis, purchased from the China Industrial Microbiological Culture Collection Center with the number CICC 25064, produces amylase and can hydrolyze starch.

[0040] The water is deionized water.

[0041] The total mass fraction of phosphate and urea in the slow-release agent for fertilizer was tested to be 1.86%.

[0042] The drying temperature is 50° C. and the mixture is dried until the moisture content is less than 0.4%.

[0043] The invention relates to a preparation method of a slow-release fertilizer containing a slow-release agent for fertilizer. The slow-release agent for fertilizer is added into the fertilizer and mixed evenly to obtain the slow-release fertilizer.

[0044] The mass ratio of slow-release fertilizer to fertilizer is 1:99.

[0045] The fertilizer ratio is 250 parts of urea, 200 parts of industrial-grade ammonium dihydrogen phosphate, 200 parts of potassium sulfate, and 350 parts of ammonium sulfate, with a specific ratio of N 20, P2O5 12, and K2O 10. Example 2

[0046] A method for preparing a slow-release agent for fertilizer is carried out according to the following steps:

[0047] Add starch, phosphate and urea to water, react at 100°C for 3 hours, cool to 40°C, add Bacillus amyloliquefaciens, stir evenly, and dry to obtain a slow-release agent for fertilizer.

[0048] The mass ratio of starch, phosphate, urea, Bacillus amyloliquefaciens and water is 40:5:0.3:1:53.7;

[0049] The phosphate is a composition of potassium dihydrogen phosphate and potassium pyrophosphate in a mass ratio of 2:1; the Bacillus amyloliquefaciens is purchased from the China Industrial Microorganism Culture Collection Center with the number CICC 20164, produces amylase, and can enzymatically hydrolyze starch.

[0050] The water is deionized water.

[0051] The total mass fraction of phosphate and urea in the slow-release agent for fertilizer was tested to be 1.87%.

[0052] The drying temperature is 50° C. and the mixture is dried until the moisture content is less than 0.4%.

[0053] The invention relates to a preparation method of a slow-release fertilizer containing a slow-release agent for fertilizer. The slow-release agent for fertilizer is added into the fertilizer and mixed evenly to obtain the slow-release fertilizer.

[0054] The mass ratio of slow-release fertilizer to fertilizer is 1:99.

[0055] The fertilizer ratio is 250 parts of urea, 200 parts of industrial-grade ammonium dihydrogen phosphate, 200 parts of potassium sulfate, and 350 parts of ammonium sulfate, with a specific ratio of N 20, P2O5 12, and K2O 10. Example 3

[0056] A method for preparing a slow-release agent for fertilizer is carried out according to the following steps:

[0057] Add starch, phosphate and urea to water, react at a temperature of 110°C and a pressure of 1.5 MPa for 2 hours, cool to 30°C, add Bacillus amyloliquefaciens, stir evenly, and dry to obtain a slow-release agent for fertilizer;

[0058] The mass ratio of starch, phosphate, urea, Bacillus amyloliquefaciens and water is 45:8:1:2:44;

[0059] The phosphate is a composition of potassium dihydrogen phosphate and dipotassium hydrogen phosphate in a mass ratio of 1:3; the Bacillus amyloliquefaciens is purchased from the China Industrial Microorganism Culture Collection Center with the number CICC 23281.

[0060] The water is distilled water.

[0061] The total mass fraction of phosphate and urea in the slow-release agent for fertilizer was tested to be 2.98%.

[0062] The drying temperature is 60° C. and the mixture is dried until the moisture content is less than 0.4%.

[0063] The invention relates to a preparation method of a slow-release fertilizer containing a slow-release agent for fertilizer. The slow-release agent for fertilizer is added into the fertilizer, and granulated to obtain a slow-release compound fertilizer.

[0064] The mass ratio of slow-release fertilizer to fertilizer is 2:98.

[0065] The granulation temperature is 65±5°C.

[0066] The fertilizer ratio is N 20, P2O5 10, K2O 12. Example 4

[0067] A method for preparing a slow-release agent for fertilizer is carried out according to the following steps:

[0068] Add starch, phosphate and urea to water, react at 98°C for 4 hours, cool to 45°C, add Bacillus subtilis, stir evenly, and dry to obtain a slow-release agent for fertilizer;

[0069] The mass ratio of starch, phosphate, urea, Bacillus subtilis, and water is 35:3:0.08:0.5:61.43;

[0070] The phosphate is a composition of sodium dihydrogen phosphate and sodium pyrophosphate in a mass ratio of 1:2.

[0071] The water is distilled water.

[0072] The total mass fraction of phosphate and urea in the slow-release agent for fertilizer was tested to be 1.31%.

[0073] The drying temperature is 55° C. and the mixture is dried until the moisture content is less than 0.4%.

[0074] The invention relates to a preparation method of a slow-release fertilizer containing a slow-release agent for fertilizer. The slow-release agent for fertilizer is added into a water-soluble fertilizer and mixed evenly to obtain the slow-release water-soluble fertilizer.

[0075] The mass ratio of slow-release fertilizer to water-soluble fertilizer is 1.2:98.8.

[0076] The fertilizer ratio is 300 parts of urea, 170 parts of industrial-grade ammonium dihydrogen phosphate, 200 parts of potassium sulfate and 330 parts of ammonium sulfate.

[0077] The beneficial effects of the present invention are further illustrated below in conjunction with test data:

[0078] Test materials

[0079] 1.1 Experimental location: Institute of Dryland Agriculture, Gansu Academy of Agricultural Sciences.

[0080] 1.2 Experimental testing: Based on the nitrogen content, the initial nutrient release rate (%), the cumulative nutrient release rate after 28 days (%), and the cumulative nutrient release rate during the nutrient release period (%) were tested.

[0081] 1.3 Test subjects: Blank (except that Bacillus subtilis was not added, the other preparations were consistent with Example 1), Comparison 1 (except that Bacillus subtilis was purchased from the China Industrial Microorganism Culture Collection Center with the number CICC 23830, the others were consistent with Example 1. This Bacillus produces laccase, which can degrade lignin but cannot degrade starch), Comparison 2 (except that the mass ratio of starch, phosphate, urea, Bacillus subtilis and water is 40:5:3:1:51, and the total mass fraction of phosphate and urea in the slow-release fertilizer is 6.79% after testing, the others are consistent with Example 1), Comparison 3 (except that the water used is tap water, the others are consistent with Example 1), Comparison 4 (the slow-release fertilizer prepared in Example 1 is used, and the ratio of the selected fertilizer is N 25, P2O5 12, K2O 10, specifically 450 parts of urea, 200 parts of industrial-grade monoammonium phosphate, 200 parts of potassium sulfate and 150 parts of ammonium sulfate, and the rest are consistent with Example 1), the slow-release fertilizer prepared in Example 1 and Example 2.

[0082] 1.4 Test method: Test in accordance with GB / T 23348-2009 Slow-release fertilizers.

[0083] The standard requires that the initial nutrient release rate (%) is ≤15%; the cumulative nutrient release rate (%) over 28 days is ≤80%; the cumulative nutrient release rate (%) during the nutrient release period is ≥80%;

[0084] 2 Results and Analysis

[0085] The average values of initial nutrient release rate (%), cumulative nutrient release rate over 28 days (%), and cumulative nutrient release rate during the nutrient release period (%) for each treatment are shown in Table 1

[0086]

[0087] As can be seen in Table 1, Comparative Examples 3 and 4 do not meet the requirements of GB / T 23348-2009 for slow-release fertilizers. Comparative Examples 1, 2, Examples 1, and 2 do meet the requirements of GB / T 23348-2009 for slow-release fertilizers, so Comparative Examples 3 and 4 were discarded. The cumulative nutrient release rates during the nutrient release period for the blank and Comparative Example 1 were 84% and 86%, respectively, indicating an issue of excessive nutrient lock-in. This may be due to the slow degradation of the slow-release fertilizer due to its aging resistance, resulting in incomplete nutrient release.

[0088] Comparison 4 should have a higher nitrogen content, and the slow-release agent for fertilizer prepared in this application utilizes its adsorption function for slow release, and the adsorbed nitrogen has an upper limit, and the slow-release fertilizer is a test for nitrogen. Therefore, for nitrogen content higher than 20%, the slow-release agent for fertilizer prepared in this application is limited by its own conditions and cannot meet the requirements of slow-release fertilizer with a nitrogen content higher than 20%.

[0089] Experiment 2

[0090] Test materials

[0091] 1.1 Test location: Seed corn base in Huangyang Town, Liangzhou District, Wuwei City, corn variety Xianyu 335.

[0092] 1.2 Experimental test: number of grains per ear (grains), weight of grains per ear (g), weight of 100 grains (g) and yield (kg). 100 plants were randomly selected from each plot for statistical analysis.

[0093] 1.3 Test subjects: A blank (except that Bacillus subtilis was not added, the other preparations were consistent with Example 1), a control 1 (except that Bacillus subtilis was purchased from the China Industrial Microorganism Culture Collection Center and was numbered CICC 23830, the others were consistent with Example 1, this Bacillus produces laccase, can degrade lignin, and cannot degrade starch), a control 2 (except that the mass ratio of starch, phosphate, urea, Bacillus subtilis and water in the preparation of the slow-release fertilizer was 40:5:3:1:51, and the total mass fraction of phosphate and urea in the slow-release fertilizer was 6.79% after testing, the others were consistent with Example 1), and the slow-release fertilizer prepared in Examples 1 and 2 were mixed with the fertilizer to prepare a slow-release water-soluble fertilizer.

[0094] The fertilizer ratio is 250 parts of urea, 200 parts of industrial-grade ammonium dihydrogen phosphate, 200 parts of potassium sulfate, and 350 parts of ammonium sulfate. The specific ratio is N 20, P2O5 12, and K2O 10.

[0095] 1.4 Experimental design: The adjacent 5 mu corn field was divided into 5 plots, each with 1 mu, and drip irrigation was used for treatment. The method of using water-soluble fertilizer was to dilute the slow-release fertilizer with water 1200 times and then drip irrigation was used.

[0096] In this experiment, each treatment was drip irrigated three times, and the amount of fertilizer used each time was 12 kg.

[0097] Note: The pipes must be cleaned with clean water before and after drip irrigation.

[0098] In this experiment, except for the different treatments, other management methods were the same.

[0099] 2 Results and Analysis

[0100] The average values of the number of grains per ear (grains), grain weight per ear (g), 100-grain weight (g) and yield per mu (kg) for each treatment are shown in Table 2

[0101]

[0102] As can be seen from Table 2, Example 1 and Example 2 can significantly increase the number of kernels per ear, kernel weight per ear, 100-kernel weight, and yield of corn compared to the blank, Comparative 1, and Comparative 2. That is, the addition of Bacillus that can degrade starch can improve the effectiveness of the slow-release fertilizer.

[0103] In comparison 2, although Bacillus subtilis, which can degrade starch, was added, the total mass fraction of phosphate and urea in the slow-release fertilizer was 6.79%, which was greater than 6%. This may cause the added Bacillus subtilis to be unable to adapt to the high-salt environment during drying and storage, and its growth may be inhibited or even die. Therefore, it cannot show excellent effect when used.

[0104] From the data in Table 1 and Table 2, it can be seen that although the blank and comparative 1 can also meet the requirements of slow-release fertilizers, they have the problem of insufficient nutrient release. In actual application, the use effect is not as good as that of Example 1 and Example 2 using Bacillus capable of degrading starch.

Claims

1. A method for preparing a slow-release agent for fertilizer, characterized in that: Follow these steps to proceed Add starch, phosphate and urea to water, react for 2 to 4 hours at a temperature of 95 to 120°C and a pressure of 0 to 2 MPa, cool to 20 to 50°C, add Bacillus, stir evenly, and dry to obtain a slow-release agent for fertilizer. The mass ratio of starch, phosphate, urea, bacillus and water is 30-50:3-15:0.02-0.6:0.2-10:35-67; The Bacillus is capable of degrading starch.

2. The method for preparing a slow-release agent for fertilizer according to claim 1, wherein: The phosphate is one or more of potassium dihydrogen phosphate, sodium dihydrogen phosphate, sodium pyrophosphate, potassium pyrophosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, disodium hydrogen phosphate and dipotassium hydrogen phosphate; the Bacillus is one or both of Bacillus amyloliquefaciens and Bacillus subtilis.

3. The method for preparing a slow-release agent for fertilizer according to claim 2, wherein: The water is one or both of deionized water and distilled water.

4. The method for preparing a slow-release agent for fertilizer according to claim 1, wherein: The total mass fraction of phosphate and urea in the slow-release agent for fertilizer is not greater than 6%; the mesh size of the slow-release agent for fertilizer is greater than or equal to 200 meshes.

5. The method for preparing a slow-release agent for fertilizer according to claim 1, wherein: The drying temperature is 40-60° C. and the drying is performed until the moisture content is less than 0.4%.

6. The method for preparing a slow-release fertilizer containing a slow-release agent for fertilizer according to any one of claims 1 to 5, characterized in that: Add the slow-release agent to the fertilizer and mix well to obtain the slow-release fertilizer.

7. The method for preparing a slow-release fertilizer containing a slow-release agent for fertilizer according to claim 6, wherein: The mass ratio of slow-release agent to fertilizer is 0.1-5:95-99.9; The nitrogen content of the fertilizer is less than or equal to 20%; The fertilizer is a water-soluble fertilizer.

8. The method for preparing a slow-release fertilizer containing a slow-release agent for fertilizer according to claim 6, wherein: Also includes granulation.

9. The method for preparing a slow-release fertilizer containing a slow-release agent for fertilizer according to claim 8, wherein: The granulation temperature should be lower than 70°C.

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