Intelligent responsive nutrient polymerization slow-release fertilizer and preparation method thereof

Abstract

The application discloses an intelligent response type nutrient polymerization slow-release fertilizer and a preparation method thereof, and belongs to the technical field of slow-release fertilizers. The intelligent response type nutrient polymerization slow-release fertilizer of the application solves the problem that the molecular chain length of the nutrient polymerization slow-release fertilizer cannot be controlled by adopting a brominated acetylated substance modified methylene urea technology, and solves the problem that the fertilizer and crop interaction ability is poor by connecting an acid-sensitive substance to a methylene urea fragment with a determined nutrient release period. Organic acid secreted by roots can respond to the nutrient polymerization slow-release fertilizer, so as to promote the release of nutrients, and the nutrient release rate and release amount are positively correlated with the amount of the organic acid secreted by the roots, and the fitting degree with the crop fertilizer requirement law is also higher. Therefore, the nutrient polymerization slow-release fertilizer which can respond to the root nutrient demand signal secretion will be more widely applied to different crops such as wheat, corn, peanut, vegetable and fruit trees, and the application area will be more extensive.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of controlled-release fertilizers, in particular to an intelligent response type nutrient polymerization slow-release fertilizer and a preparation method thereof. BACKGROUND

[0002] In recent years, due to the excessive input of chemical fertilizers, a series of ecological environmental problems have appeared, such as: reduction of nutrient utilization rate, soil degradation, water eutrophication, etc. The use of new fertilization technologies and new fertilizer products is an important way to solve the above problems. Among them, under the background of multidisciplinary intersection, using chemical reaction method to polymerize nitrogen, phosphorus, potassium and other nutrient elements into new polymer fertilizer with nutrient slow-release function has become an important research hotspot at present. The traditional nutrient polymerization slow-release fertilizer has the problems of single nutrient element, complex preparation process, high production cost, and difficult degradation, which restricts the efficient and rapid development of the industry. In recent years, the development of low-cost, nutrient full-element, and superior degradation performance of nutrient polymerization slow-release fertilizer can be expected to improve the above problems, but there are still the following problems:

[0003] (1) The nutrient polymerization slow-release fertilizer mainly generates a large number of hydroxymethyl urea fragments such as methylenediurea, dimethylenetriurea, and trimethylenetetraurea through addition, condensation and other reactions under certain conditions in dilute solution or concentrated solution by urea and formaldehyde. Because there are a large number of active groups in the reaction system, the hydroxymethyl urea fragments will continuously react and be connected by chemical bonds, so that the molecular chain of the fertilizer is infinitely increased and difficult to control, resulting in a long lasting period of fertilizer efficiency of several months or even several years. Therefore, the existing nutrient polymerization slow-release fertilizer is only used in some non-food crops such as lawns, trees, etc. The growth period of food crops (wheat, corn, rice, etc.) is only a few months, and the urea-formaldehyde nutrient polymerization slow-release fertilizer cannot supply sufficient nutrients to the current season crops, which ultimately affects its actual application range in agricultural production.

[0004] (2) The nutrient polymerization slow-release fertilizer will slowly degrade under the catalysis of microorganisms, enzymes and other biological conditions after being applied to the soil, and then release nutrient elements. Because there are great differences in different soil environments, the released nutrients cannot match the nutrient demand of crops, and root fertilizer mutual feeding cannot be achieved.

[0005] The related patent CN110256144B discloses a biodegradable high-molecular slow-release organic nano-fertilizer containing multiple nutrient elements, which is prepared by reacting urea, formaldehyde and phosphate in a corresponding proportion, but this method cannot control the length of the fertilizer molecular chain, and the release period is not improved; the related patent CN115286453A discloses a urea-formaldehyde potassium fulvic acid fertilizer with the functions of acid regulation, alkali pressure, rooting and strong plant, which is prepared by mixing, dissolving, shearing, emulsifying and chelating, and the fertilizer prepared by this method can realize synergistic effect among raw materials, but cannot truly realize the "dialogue" between the fertilizer and crops, and there is a certain waste of resources. SUMMARY

[0006] In view of the above prior art, the purpose of the present application is to provide an intelligent response type nutrient polymer slow-release fertilizer and a preparation method thereof. The intelligent response type nutrient polymer slow-release fertilizer can respond to the signal molecule substances released by the roots of plants in the absence of nutrients, rapidly release nutrients such as nitrogen and phosphorus, and be absorbed and utilized by crops, thereby truly realizing the "dialogue" between the fertilizer and crops.

[0007] To achieve the above purpose, the present application adopts the following technical solutions:

[0008] In a first aspect of the present application, a methylene urea fragment with a specific molecular chain length is prepared by reacting formaldehyde, urea, phosphate, brominated acetylated substance and a first catalyst.

[0009] The weight ratio of the formaldehyde, urea, phosphate and brominated acetylated substance is 1:(1-2):(0.1-0.4):(2-3), and the addition amount of the first catalyst is 1%-3% of the weight of the brominated acetylated substance.

[0010] Preferably, the brominated acetylated substance is selected from one or more of brominated acetylated glucose, brominated acetylated starch and brominated acetylated cellulose.

[0011] Further, the brominated acetylated substance is prepared by the following method:

[0012] (1) Preparation of acetylated substance

[0013] Acetic anhydride is added to a flask in an ice water bath, followed by the addition of 1-5 drops of perchloric acid, then glucose, starch or cellulose is added to the reaction system in portions, and a certain amount of a second catalyst is added, and the reaction is carried out at room temperature for 6-10 h, and then the acetylated substance is extracted.

[0014] More preferably, the weight ratio of the acetic anhydride to glucose, starch or cellulose is (3-6):(1-1.5).

[0015] More preferably, the second catalyst is selected from one or more of sulfamic acid, methanesulfonic acid and sulfuric acid;

[0016] As a preference, the structural unit of the prepared acetylated substance is:

[0017]

[0018]

[0019] (2) Grafting bromide

[0020] The acetylated substance prepared above is added to a flask containing a hydrogen bromide-acetic acid mixed solution (the volume ratio of hydrogen bromide to acetic acid in the hydrogen bromide-acetic acid mixed solution is 1:1), and is placed on a magnetic stirrer to react for 12-20 hours. Then, the reaction product, a brominated acetylated substance, is extracted with dichloromethane and the final product is collected.

[0021] More preferably, the weight ratio of the acetylated substance to the hydrogen bromide-acetic acid mixed solution is (0.5-1):(2-4).

[0022] As a preference, the structural unit of the prepared brominated acetylated substance is:

[0023]

[0024] Preferably, the phosphate salt is selected from one or more of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate and calcium dihydrogen phosphate.

[0025] Preferably, the first catalyst is selected from one or more of polyphosphoric acid, sodium hexametaphosphate and ammonium sulfite.

[0026] As a preference, the molecular structure of the above-mentioned methylene urea fragment of a specific molecular chain length is one or more of the following:

[0027]

[0028] wherein, Glu is a glucose having The acetylated glucose, acetylated starch, acetylated cellulose substance of the unit structure; Ac is an acetyl group.

[0029] The wavy line represents a repeating unit of methylol urea, and the structural formula is as follows:

[0030]

[0031] The methylene urea fragment of the specific molecular chain length of the application is that the acetylated bromide substance is grafted to both ends of the methylene urea molecular chain, thereby playing a role of end capping; taking glucose as an example, glucose has a relatively active hydroxyl group, the purpose of acetylation is to eliminate the activity of the hydroxyl group of glucose, thereby playing a protective role, and the purpose of bromination is to replace one of the acetylated groups with a relatively active group, so that glucose can undergo polycondensation reaction with the active hydroxyl group at both ends of the methylene urea, thereby being grafted to both ends of the methylene urea molecular chain.

[0032] In a second aspect of the application, a preparation method of the methylene urea fragment of the specific molecular chain length is provided, comprising the following steps:

[0033] The pH of formaldehyde is adjusted to 7.5-9.0 and heated to 40-60℃, urea and phosphate are added and stirred, and the acetylated bromide substance and a catalyst are slowly added, and the reaction is carried out for 1.5-2.5h, thereby obtaining the methylene urea fragment of the specific molecular chain length.

[0034] In a third aspect of the application, the methylene urea fragment of the specific molecular chain length is applied to the preparation of the nutrient polymerization type slow-release fertilizer of intelligent response root exudates.

[0035] In a fourth aspect of the application, an intelligent response type nutrient polymerization slow-release fertilizer is provided, which is prepared from the following raw materials by weight:

[0036] The methylene urea fragment of the specific molecular chain length is 10 parts, the polymerization monomer is 5-10 parts, and the substance with acid-sensitive chemical bonds is 5-10 parts.

[0037] Preferably, the polymerization monomer is prepared by the following method:

[0038] The substance A and the substance B are placed in a reaction bottle, dissolved in a certain amount of methanol, and refluxed at 70℃ for 15-20h, then a small amount of sodium bicarbonate is added to terminate the reaction, and the polymerization monomer product is collected at 50℃ by using a rotary evaporator;

[0039] More preferably, the weight ratio of the substance A to the substance B is 1:(1-2); the substance A is one or more of hydroxyl-ethoxybenzaldehyde, glucuronolactone and hydroxyl-methoxybenzaldehyde; and the substance B is one or more of trimethyl orthoformate, ethyl acetate and methyl acetoacetate.

[0040] As preferred, the structural formula of the polymerization monomer can be as follows:

[0041]

[0042] In the formula, the middle circle ball represents a cyclic substance or an olefin substance, the wavy line connected to the middle circle ball represents an alkane straight chain, and the horizontal line connected to the oxygen atom represents a methyl group.

[0043] Preferably, the substance with acid-sensitive chemical bonds is an acetal compound with organic acid-sensitive chemical bonds ketal compound hydrazone compound (-C=N-N), orthoester compound one or more of them.

[0044] In a fifth aspect of the present application, a preparation method of the nutrient polymer slow-release fertilizer responsive to root exudates is provided, comprising the following steps:

[0045] The methylene urea fragment, the polymer monomer, and the substance with acid-sensitive chemical bonds are placed in a reaction tube in a corresponding proportion, stirred at room temperature for 15-30 min in a dry Ar atmosphere, then heated to 70-90°C, and continue to stir for 20-40 min to fully mix the reactants, and continue to polymerize for 1.5-2 h. Thereafter, the reaction tube is cooled to room temperature, the polymer in the reaction tube is dissolved with tetrahydrofuran (THF), a small amount of sodium bicarbonate is added to terminate the polymerization reaction, and continue to stir for 10-20 min; the insoluble substances are removed by filtration, and the filtrate is concentrated and precipitated in anhydrous ethanol containing a small amount of triethylamine to obtain the nutrient polymer slow-release fertilizer responsive to root exudates.

[0046] The present application has the following beneficial effects:

[0047] (1) The nutrient polymer slow-release fertilizer responsive to root exudates prepared by the present application has a methylene urea fragment with a specific molecular chain length, effectively regulates the nutrient release period of the nutrient polymer slow-release fertilizer, and greatly improves the nutrient release efficiency.

[0048] (2) The nutrient polymer slow-release fertilizer responsive to root exudates prepared by the present application connects each methylene urea fragment through acid-sensitive chemical bonds, and the acid-sensitive chemical bonds are broken under the action of root exudate acid, thereby rapidly releasing a certain methylene urea nutrient fragment, thereby efficiently supplying the required nutrients to crops, and truly realizing the "response dialogue" between the fertilizer and the crops.

[0049] (3) The nutrient polymer slow-release fertilizer responsive to root exudates provided by the present application has better stability compared to the coated controlled-release fertilizer formed by physical coating, and improves the nutrient utilization rate and precision rate of the fertilizer.

[0050] (4) The nutrient polymer slow-release fertilizer responsive to root exudates prepared by the present application can be completely degraded under the action of microorganisms and enzymes after being applied to the soil, reducing the harm to the environment, and meeting the needs of contemporary green and sustainable development.

[0051] (5) The nutrient polymerized slow-release of the intelligent responsive root exudate prepared by the present invention has a positive correlation between the nutrient release rate and the amount of release and the amount of organic acid secreted by the root system. It has a higher degree of fit with the crop fertilizer requirement pattern and will be more widely used in different crops such as wheat, corn, peanut, vegetables, and fruit trees. The application area will be more extensive. Attached Figure Description

[0052] Figure 1 : Schematic diagram of the mechanism of response between intelligent responsive nutrient polymer slow-release fertilizer and crop root exudates.

[0053] Figure 2 Schematic diagram of a nutrient-polymerized slow-release fertilizer that responds to root exudates.

[0054] Figure 3 Infrared spectra of methylene urea fragments with specific molecular chain lengths prepared in Example 1 of this invention; by Figure 3 It is known that the methylene urea fragment contains the -CO- characteristic group, proving that a methylene urea fragment with a specific molecular chain length has been successfully prepared.

[0055] Figure 4 Infrared spectrum of the intelligent responsive root exudate nutrient polymer slow-release fertilizer prepared in Example 2 of this invention; from Figure 4 It is known that this nutrient polymer slow-release fertilizer contains a large number of -CO- characteristic groups, proving that a nutrient polymer slow-release fertilizer that responds to root exudates has been successfully prepared.

[0056] Figure 5 Nutrient release curves in the rhizosphere microdomain of the intelligent responsive root exudate nutrient polymer slow-release fertilizer and the traditional nutrient polymer slow-release fertilizer; the nutrient release curves demonstrate that, compared with the traditional nutrient polymer slow-release fertilizer, the intelligent responsive root exudate nutrient polymer slow-release fertilizer prepared in Example 2 is more in line with the nutrient requirements of crops. Detailed Implementation

[0057] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0058] As mentioned earlier, the molecular chain length of existing nutrient-polymerized slow-release fertilizers cannot be controlled, resulting in long and uncertain nutrient release cycles, which greatly limits their practical application effects and scope. In addition, the nutrient release of existing nutrient-polymerized slow-release fertilizers varies greatly in different soil environments, and their nutrient release cannot match the crop's nutrient requirements. A direct connection cannot be established between the fertilizer and the plant root system, which leads to a certain waste of resources.

[0059] In view of the above problems, the present application realizes original technical breakthrough from the following aspects:

[0060] (1) In view of the fact that the molecular chain length of the nutrient polymer type slow-release fertilizer cannot be controlled, the present application grafts one or more modifiers of brominated acetylated glucose, brominated acetylated starch, brominated acetylated cellulose, etc. to both ends of the methylene urea fragment, eliminates the active functional groups, and prepares a nutrient polymer type slow-release fertilizer with a specific molecular chain length and a determinable nutrient release period. The traditional nutrient polymer type slow-release fertilizer cannot relatively accurately control the molecular weight within a certain range, because the urea and formaldehyde continuously generate hydroxyl groups and other active groups at both ends of the chain under the reaction conditions of addition, condensation and the like, and the active groups will continuously react with urea and formaldehyde to make the molecular chain of the nutrient polymer type slow-release fertilizer continuously grow. Therefore, by grafting one or more of brominated acetylated glucose, brominated acetylated starch, and brominated acetylated cellulose capable of eliminating hydroxyl groups and other active groups to both ends of the methylene urea fragment, these substances can well eliminate hydroxyl groups and other active groups, reduce the possibility of unlimited growth of the molecular chain, and preliminarily realize the feasibility of the transformation of the nutrient polymer type slow-release fertilizer to the nutrient polymer type controlled-release fertilizer.

[0061] (2) In view of the fact that the nutrient release of the traditional nutrient polymer type slow-release fertilizer cannot match the needs of crops, and the fertilizer and crops have not established a direct connection, the present application originally connects the methylene urea fragments with specific molecular chain lengths through acid-sensitive chemical bond substances. The methylene urea fragments with specific molecular chain lengths and acid sensitivity are combined together, which can greatly expand the transportation of the fertilizer in the soil. Under the corresponding pH, the acid-sensitive chemical bond will break, so that the specific molecular chain fragments connected by the acid-sensitive chemical bond will be removed, such as acetal, ketal, hydrazone, ortho ester acid and the like. The types and amounts of organic acids released by the roots of crops at different growth stages will be significantly different, and the types and amounts of released organic acids are positively correlated with the degree of nutrient deficiency. Different organic acid secretions also have certain differences in the effect on nutrient elements. For example, citric acid, oxalic acid, malic acid, tartaric acid and the like have relatively strong acidity, and have relatively large effects on nitrogen and phosphorus, while other organic acid substances have corresponding effects on the activation and absorption of phosphorus.

[0062] When plants are in lack of nutrients, root system releases signal molecule substances such as organic acid substances including citric acid, oxalic acid, malic acid, tartaric acid, acetic acid and the like. The slow-release fertilizer of the application can intelligently respond to the signal molecule substances released by the root system of plants, and through the acid-sensitive chemical bond connection, not only can the slow-release fertilizer of the application realize real-time 'communication and interaction' with the whole growth dynamic process of crops, but also can release the required types and amounts of nutrient elements in time according to the requirements of crops. The methylene urea fragment with specific molecular chain length and the acid-sensitive chemical bond substance connecting the methylene urea fragments in the nutrient polymer slow-release fertilizer intelligently responding to the root secretion have good degradation performance, and greatly reduce the pollution to the ecological environment.

[0063] The nutrient polymer slow-release fertilizer intelligently responding to the root secretion prepared by the application can be applied to different crops such as wheat, corn, peanut, vegetables and fruit trees, and the application area will be more extensive. The root secretion of different crops will directly determine the response difference of the acid-sensitive chemical bond, the nutrient release rate and release amount of the fertilizer are positively correlated with the amount of root secretion organic acid, and therefore the nutrient utilization efficiency of the fertilizer can be greatly improved, and the waste of resources is avoided.

[0064] In order for those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific examples.

[0065] The test materials used in the examples and comparative examples of the application are all conventional test materials in the art, and can be purchased through commercial channels. The experimental methods without detailed conditions are carried out according to the conventional test methods or according to the operation instructions recommended by the suppliers.

[0066] Example 1: Preparation of methylene urea fragment with specific molecular chain length

[0067] (1) 50ml acetic anhydride solution was added to a round-bottom flask, followed by 1-5 drops of perchloric acid, the flask was placed on a magnetic stirrer filled with ice water, 10g glucose was added in 5 times according to the standard of 2g each time, 1g sulfamic acid was added at the same time when the first glucose was added, and the reaction was carried out at room temperature for 6h; then the reaction solution was diluted with 20ml ethyl acetate, and extracted with chloroform to obtain acetylated glucose; then 5g acetylated glucose was added to 20ml hydrogen bromide-acetic acid mixed solution (the volume ratio of hydrogen bromide to acetic acid in the hydrogen bromide-acetic acid mixed solution is 1:1), and placed on a magnetic stirrer for reaction for 24h; then the reaction was extracted with dichloromethane, and finally the product of brominated acetylated glucose was prepared.

[0068] (2) Adjust the pH of 20 g of formaldehyde in a reaction flask to 8.0 and heat to 50°C, then add 30 g of urea and 4 g of ammonium dihydrogen phosphate and start stirring, after the urea and ammonium dihydrogen phosphate are dissolved, add 40 g of acetylated glucose bromide and 1.2 g of polyphosphoric acid, and after 2 h of reaction, the reaction is stopped, to prepare a methylene urea fragment with a specific length, i.e. a nutrient polymer slow-release fertilizer with a determinable nutrient release period.

[0069] Example 2: Preparation of an intelligent response type nutrient polymer slow-release fertilizer

[0070] (1) Place substance A (4-(2-hydroxyethoxy)benzaldehyde) and substance B (trimethyl orthoformate) in a reaction flask at a weight ratio of 1:2, dissolve in 80 ml of methanol, and reflux at 70°C for 18 h, then terminate the reaction with 2% sodium bicarbonate relative to the total weight of substance A and substance B, and collect the polymer monomer product at 50°C using a rotary evaporator;

[0071] (2) Place 20 g of the methylene urea fragment with a specific length prepared in Example 1, 15 g of the polymer monomer prepared in step (1), and 5 g of benzaldehyde dimethyl acetal in a reaction tube, stir at room temperature for 20 min in a dry Ar atmosphere, then heat to 80°C and continue stirring for 30 min to fully mix the reactants, and continue polymerization for 2 h. Thereafter, cool the reaction tube to room temperature, dissolve the polymer in the reaction tube with THF, add 0.8 g of sodium bicarbonate to terminate the polymerization reaction, and continue stirring for 15 min; remove the insoluble material by filtration, concentrate the filtrate, and add the concentrated filtrate to a solution of triethylamine in anhydrous ethanol (the content of triethylamine is 10% by volume) to precipitate, and collect the precipitate to prepare an intelligent response type nutrient polymer slow-release fertilizer.

[0072] Quantitative infrared spectroscopy was performed on the methylene urea fragment with a specific length prepared in Example 1 and the intelligent response type nutrient polymer slow-release fertilizer prepared in Example 2, respectively, and the results are shown in Figure 3 and Figure 4 The methylene urea fragment with a specific length contains a -C-O- characteristic group; after the acid-sensitive chemical bond is subjected to polycondensation with the methylene urea fragment with a specific length, a -C-O- characteristic group is also formed, and according to quantitative infrared analysis, the number of -C-O- characteristic groups in the intelligent response root exudate nutrient polymer slow-release fertilizer is significantly increased. Thus, it can be proved that the methylene urea fragment with a specific length and the intelligent response type nutrient polymer slow-release fertilizer have been successfully prepared.

[0073] Comparative Example: Preparation of a traditional nutrient polymer slow-release fertilizer

[0074] The 20 g of formaldehyde in the reaction bottle was adjusted to pH 8.0 and heated to 50°C, then 30 g of urea and 4 g of ammonium dihydrogen phosphate were added and stirring was started, after the urea and ammonium dihydrogen phosphate were dissolved, the reaction was stopped after 2 h, and the traditional nutrient polymer slow-release fertilizer was prepared.

[0075] Test Example: Nutrient Release Effect Simulation Test of Rhizosphere Microdomain

[0076] 1. Test Method

[0077] 10 g of the nutrient polymer slow-release fertilizer prepared in Example 2 and the traditional nutrient polymer slow-release fertilizer prepared in the comparative example were taken respectively in a mesh with a pore size of 0.074 mm, soaked in a plastic bottle containing 200 ml of deionized water, sealed with a lid, and placed in a biochemical incubator at 25°C. The pH value of the culture system was adjusted in the order of 7.0, 6.5, 6.0, and 5.5. During the first 10 days of culture, pH 7.0 buffer was used, during the 10th to 28th day, pH 5.5 buffer was used, during the 28th to 56th day, pH 6.0 buffer was used, and during the 56th to 70th day, pH 6.5 buffer was used.

[0078] At the sampling time nodes of 1st, 3rd, 5th, 7th, 10th, 14th, 28th, 42nd, 56th, and 70th days, the aqueous solution in the plastic bottle was poured out, and the nitrogen content in the solution was determined by the Kjeldahl method. Then 200 ml of buffer was added to the bottle containing the mesh, sealed with a lid, and placed in the biochemical incubator for further culture.

[0079] Considering that the synthetic process of the intelligent response nutrient polymer slow-release fertilizer for root exudates prepared in Example 2 and the traditional nutrient polymer slow-release fertilizer prepared in the comparative example is different, the nutrient content is slightly different, so the nutrient release amount is represented by the ratio of the release amount to the nutrient content of the fertilizer.

[0080] 2. Test Results:

[0081] In this test example, the pH value of the culture system was adjusted in time according to the growth law of crops, the release amount of nutrients at each period was determined, and compared with the fertilizer requirement of crops at that period, and finally the relationship between the nutrient release rate and the fertilizer requirement of crops was obtained.

[0082] The test results are as follows: Figure 5As shown, it can be seen that in the period of 70 days, the nutrient release of the intelligent response type nutrient polymer slow-release fertilizer prepared in the embodiment 2 of the application has a good matching degree with the crop fertilizer requirement law; in the whole period of crop growth, a large amount of organic acid secretion is released in the early stage, which causes the increase of the acidity of the rhizosphere micro area, thus promoting the nutrient release of the fertilizer, the secretion amount of the organic acid decreases in the middle and late stages of the crop growth, so the rate of the nutrient release slows down; thus, the "dialogue" between the fertilizer and the crop is realized.

[0083] The above merely describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A nutrient polymer slow-release fertilizer which is intelligent in response to root exudates, characterized by, The following raw materials are prepared by weight parts: The methylene urea fragment with specific molecular chain length is prepared by reacting formaldehyde, urea, phosphate, acetylated bromide substance and first catalyst; The weight ratio of the formaldehyde, urea, phosphate, acetylated bromide substance is 1: (1-2): (0.1-0.4): (2-3), and the first catalyst is added in an amount of 1%-3% of the weight of the acetylated bromide substance; the acetylated bromide substance is selected from one or more of acetylated bromide glucose, acetylated bromide starch and acetylated bromide cellulose; and the first catalyst is selected from one or more of polyphosphoric acid, sodium hexametaphosphate and ammonium sulfite; The preparation method of the methylene urea fragment with specific molecular chain length comprises the following steps: The pH of the formaldehyde is adjusted to 7.5-9.0 and heated to 40-60℃, urea and phosphate are added and stirred, and then the acetylated bromide substance and the first catalyst are slowly added, and the reaction is carried out for 1.5-2.5h to prepare the methylene urea fragment with specific molecular chain length; The polymerization monomer is prepared by the following method: Substance A and substance B are dissolved in methanol, and refluxed at 70℃ for 15-20h, and then sodium bicarbonate is added to terminate the reaction to prepare the polymerization monomer; The weight ratio of the substance A and the substance B is 1: (1-2); the substance A is one or more of hydroxy-ethoxybenzaldehyde, glucuronolactone and hydroxy-methoxybenzaldehyde; and the substance B is one or more of methyl orthoformate, ethyl acetate and methyl acetoacetate; The substance with acid-sensitive chemical bond is one or more of acetal compounds, ketal compounds, hydrazone compounds and orthoester compounds. The acetylated bromide substance is prepared by the following method:

2. The smart responsive root exudite nutrient polymeric slow release fertilizer according to claim 1, characterized in that, Acetic anhydride is mixed with glucose, starch or cellulose, and a second catalyst is added to react at room temperature for 6-10h to prepare the acetylated substance; The acetylated substance is reacted with a mixed solution of hydrogen bromide-acetic acid for 12-20h to prepare the acetylated bromide substance; The second catalyst is selected from one or more of sulfamic acid, methanesulfonic acid and sulfuric acid. The following steps are included:

3. The method for preparing the smart responsive root exudate nutrient polymeric slow release fertilizer according to claim 1 or 2, characterized in that, The methylene urea fragment with specific molecular chain length, the polymerization monomer and the substance with acid-sensitive chemical bond are stirred at room temperature for 15-30min in a dry Ar atmosphere, and then heated to 70-90℃, and the stirring is continued for 20-40min to fully mix the reactants, and the polymerization is continued for 1.5-2h; the polymer is dissolved in tetrahydrofuran, sodium bicarbonate is added to terminate the polymerization reaction, and the stirring is continued for 10-20min; the insoluble substances are removed by filtration, the filtrate is concentrated, and precipitated in anhydrous ethanol containing triethylamine to prepare the nutrient polymerization type slow-release fertilizer for intelligent response root exudates. ​

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