Organic-inorganic polymerized water-retaining slow-release fertilizer special for watermelons and preparation method thereof

Abstract

The invention relates to the technical field of fertilizers, in particular to an organic-inorganic polymerized water-retaining slow-release fertilizer special for watermelons and a preparation method thereof. Comprising the following steps: crushing and puffing diatomite to obtain puffed diatomite, adding the puffed diatomite into distilled water, adding N, N-methylene bisacrylamide and potassium persulfate, uniformly stirring, standing, filtering out the puffed diatomite, adding the puffed diatomite into the distilled water, adding an inorganic fertilizer, adding an acrylamide reaction monomer, uniformly stirring, adding a crosslinking agent, and uniformly stirring to obtain a uniform mixture; heating and reacting to obtain a gelatinous reaction product, and drying and crushing the reaction product to obtain the water-retaining fertilizer. According to the invention, the acrylamide monomer is subjected to cross-linking reaction on the surface of the diatomite and in the pore diameter, so that the prepared fertilizer has good slow release effect and water retention effect at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizers, in particular to an organic-inorganic polymer water-retaining slow-release fertilizer special for watermelon and a preparation method thereof. Background Art

[0002] The use of fertilizers has been increasing significantly, but the increase in grain production has not reached the same level. There are many reasons for this phenomenon. The reduction in fertilizer and water utilization is an important reason for the decline in the yield increase effect. It is particularly important to improve the utilization rate of water and fertilizers, reduce the amount of fertilizer and water, and save labor for fertilization. "Adjust water with fertilizers and promote fertilizers with water", give full play to the synergistic effect of water and fertilizers, improve the drought resistance of crops and the efficiency of water and fertilizer utilization, effectively save economic costs and improve the ecological environment. Water-retaining slow / controlled-release fertilizers can greatly improve the fertilizer nutrient utilization rate and water resource utilization rate by regulating the nutrient release rate so that it is basically synchronized with the crop nutrient absorption. Therefore, the development of water-retaining slow / controlled-release fertilizers plays an important role in the sustainable development of China's agriculture.

[0003] Chinese patent publication number CN107032858 discloses a sugarcane fertilizer, including fermented poultry and livestock manure, wood ash, comfrey, wormwood, peanut bran, iron sulfate, potassium sulfate, ammonium molybdate, boric acid, magnesium sulfate, zinc sulfate, manganese sulfate, potassium nitrate, copper sulfate, silkworm feces and disodium hydrogen phosphate. This fertilizer is an ordinary fertilizer, does not have the functions of water retention and fertilizer slow release, and cannot improve the fertilizer nutrient utilization rate and water resource utilization rate.

[0004] For example, Chinese patent publication No. CN113307699 discloses a slow-release waste material containing modified diatomaceous earth and a preparation method thereof. By improving the selection of diatomaceous earth particle size, the expansion process, and the fertilizer loading process, the adsorption effect of the modified diatomaceous earth on fertilizers is effectively improved. The prepared fertilizer has a slow-release effect, but does not have a water retention function. Summary of the invention

[0005] In order to overcome the above technical problems, the present invention provides an organic-inorganic polymer water-retaining slow-release watermelon special fertilizer and a preparation method thereof. The organic-inorganic polymer water-retaining slow-release watermelon special fertilizer of the present invention not only has a slow-release function, but also has a soil water-retaining function, which significantly improves the utilization rate of fertilizer and water resources.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions: A method for preparing an organic-inorganic polymer water-retaining slow-release fertilizer specifically for watermelon comprises the following steps: (1) crushing diatomaceous earth and expanding it to obtain expanded diatomaceous earth; (2) Add expanded diatomaceous earth to distilled water, then add N,N-methylenebisacrylamide and potassium persulfate. Stir well, let stand, then filter out the expanded diatomaceous earth and set aside; (3) adding the expanded diatomaceous earth obtained after filtering in step (2) into distilled water, then adding inorganic fertilizer, and then adding acrylamide reaction monomer to heat and react to obtain a gel reaction product, and drying and crushing the reaction product to obtain a water-retaining fertilizer.

[0007] The present invention uses diatomite as a carrier, and now expands the diatomite. The expanded diatomite has a porous structure, can absorb inorganic fertilizers, and slowly releases the fertilizers in the soil, thereby improving the utilization rate of the fertilizers. In addition, acrylamide monomers undergo cross-linking reactions inside and on the surface of the cavities of the expanded diatomite to form a three-dimensional network structure, forming a water-retaining gel, storing water in the soil, and improving the utilization rate of water resources. The present invention combines diatomite with acrylamide, which not only has a slow-release effect on the fertilizer, but also has a water-retaining effect on the soil, thereby improving the utilization rate of water resources.

[0008] Preferably, the diatomaceous earth expansion method in step (1) is to first pressurize the diatomaceous earth at atmospheric pressure and then depressurize it.

[0009] Preferably, the expanded diatomaceous earth in step (2) is subjected to a modification treatment, comprising the following steps: Ethanol and water are mixed to obtain a mixed solution, silane coupling agent KH-550 is added to the mixed solution, stirred and mixed evenly, and then expanded diatomaceous earth is added, heated and stirred for reaction, and modified expanded diatomaceous earth is obtained through separation, washing and drying.

[0010] The present invention team discovered during the experiment that expanded diatomite has poor compatibility with acrylamide, which makes it difficult for acrylamide to undergo cross-linking reaction in the micropores and surface of diatomite. To solve the above problem, the present invention modifies the expanded diatomite by grafting silane coupling agent KH-550 onto the surface of expanded diatomite, so that the surface of expanded diatomite is loaded with amino groups, thereby improving its compatibility with acrylamide and allowing acrylamide to undergo cross-linking reaction in the micropores and surface of diatomite.

[0011] Preferably, the inorganic fertilizer in step (3) is a mixture of potassium nitrate, magnesium sulfate, sodium hydrogen phosphate and ammonium molybdate.

[0012] Preferably, the mass ratio of potassium nitrate, magnesium sulfate, sodium hydrogen phosphate and ammonium molybdate is 1:1:1:3.

[0013] Preferably, the mass ratio of expanded diatomaceous earth to inorganic fertilizer in step (3) is 1:4-5.

[0014] Preferably, the mass ratio of expanded diatomaceous earth to acrylamide in the modification (3) is 1:2-3.

[0015] Preferably, the heating reaction time in step (3) is controlled within 30-90 minutes.

[0016] Preferably, the heating reaction time in step (3) is controlled within 30-57 minutes.

[0017] Through experiments, it was found that acrylamide cross-linking reaction time of 30-90min can form a relatively stable three-dimensional network structure gel with good water retention effect. Although the gel formed within the reaction time of 30-90min has a good water retention effect. However, a further problem is that the prepared product often has a poor release effect of inorganic fertilizers and cannot meet the needs of plant growth. After in-depth research by the team of the present invention, it was found that this is related to the cross-linking degree of acrylamide reaction. Excessive cross-linking of acrylamide will cause diatomaceous earth micropores to be blocked, thereby affecting the release of inorganic fertilizers. Therefore, the present invention strictly controls the cross-linking degree of acrylamide reaction, that is, by controlling the reaction time to be less than or equal to 57min, excessive cross-linking of acrylamide is controlled.

[0018] An organic-inorganic polymer water-retaining slow-release fertilizer special for watermelon is prepared by the method described above.

[0019] The present invention has the following beneficial effects: 1) The present invention uses acrylamide monomer to cause cross-linking reaction on the surface and inside the pores of diatomaceous earth, and the prepared fertilizer has good slow-release effect and water retention effect; 2) The expanded diatomite is modified by grafting the silane coupling agent KH-550 onto the surface of the expanded diatomite, so that the surface of the expanded diatomite is loaded with amino groups, thereby improving its compatibility with acrylamide and causing acrylamide to undergo cross-linking reactions inside and on the surface of the diatomite micropores. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below in conjunction with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0021] Unless otherwise specified, the raw materials used in the examples of the present invention are all commercially available or available to those skilled in the art; unless otherwise specified, the methods used in the examples of the present invention are all methods known to those skilled in the art.

[0022] Example 1 A method for preparing an organic-inorganic polymer water-retaining slow-release fertilizer specifically for watermelon comprises the following steps: (1) diatomaceous earth is crushed and passed through a 300-mesh sieve, first pressurized to 2 standard atmospheres, and then decompressed to 0.5 standard atmospheres to obtain expanded diatomaceous earth; Modification of expanded diatomite: Ethanol and water are mixed in a volume ratio of 8:1 to obtain a mixed solution, silane coupling agent KH-550 is added, the mass ratio of the silane coupling agent to the mixed solution is 1:90, and the mixture is stirred and mixed evenly, and then expanded diatomaceous earth is added, the mass ratio of the expanded diatomaceous earth to the silane coupling agent is 1:0.08, heated to 70° C., stirred and reacted for 3 hours, and separated, washed and dried to obtain modified expanded diatomaceous earth; (2) Add the modified expanded diatomaceous earth into distilled water at a mass volume ratio of 1 g / 200 mL, and then add N,N-methylenebisacrylamide and potassium persulfate, the mass ratio of the modified expanded diatomaceous earth, N,N-methylenebisacrylamide, and potassium persulfate is 1:1:0.5, stir evenly, let stand for 2 hours, and then filter out the expanded diatomaceous earth for later use; (3) adding the expanded diatomaceous earth obtained after filtering in step (2) to distilled water at a mass volume ratio of 1 g / 500 mL, and then adding inorganic fertilizer, wherein the mass ratio of expanded diatomaceous earth to inorganic fertilizer is 1:4.8, and the inorganic fertilizer is a mixture of potassium nitrate, magnesium sulfate, sodium hydrogen phosphate, and ammonium molybdate, and the ratio of the four is controlled at 1:1:1:3, to obtain a mixed solution; Under ice bath conditions, 2 mol / L sodium hydroxide solution was added dropwise to acrylamide to adjust the neutralization degree of acrylamide to 70% to obtain acrylamide reaction monomer, and the acrylamide reaction monomer was added to the above mixed solution, the mass ratio of expanded diatomaceous earth to acrylamide was 1:2.7, the reaction temperature was controlled at 80°C, the reaction was heated for 50 minutes, and a gel reaction product was obtained. The reaction product was dried and crushed to obtain a water-retaining fertilizer.

[0023] Example 2 A method for preparing an organic-inorganic polymer water-retaining slow-release fertilizer specifically for watermelon comprises the following steps: (1) diatomaceous earth is crushed and passed through a 300-mesh sieve, first pressurized to 2 standard atmospheres, and then decompressed to 0.5 standard atmospheres to obtain expanded diatomaceous earth; Modification of expanded diatomite: Ethanol and water are mixed in a volume ratio of 8:1 to obtain a mixed solution, silane coupling agent KH-550 is added, the mass ratio of the silane coupling agent to the mixed solution is 1:90, and the mixture is stirred and mixed evenly, and then expanded diatomaceous earth is added, the mass ratio of the expanded diatomaceous earth to the silane coupling agent is 1:0.08, heated to 70° C., stirred and reacted for 3 hours, and separated, washed and dried to obtain modified expanded diatomaceous earth; (2) Add the modified expanded diatomaceous earth into distilled water at a mass volume ratio of 1 g / 200 mL, and then add N,N-methylenebisacrylamide and potassium persulfate, the mass ratio of the modified expanded diatomaceous earth, N,N-methylenebisacrylamide, and potassium persulfate is 1:1:0.5, stir evenly, let stand for 2 hours, and then filter out the expanded diatomaceous earth for later use; (3) adding the expanded diatomaceous earth obtained after filtering in step (2) to distilled water at a mass volume ratio of 1 g / 500 mL, and then adding inorganic fertilizer, wherein the mass ratio of expanded diatomaceous earth to inorganic fertilizer is 1:4.2, and the inorganic fertilizer is a mixture of potassium nitrate, magnesium sulfate, sodium hydrogen phosphate, and ammonium molybdate, and the ratio of the four is controlled at 1:1:1:3, to obtain a mixed solution; Under ice bath conditions, 2 mol / L sodium hydroxide solution was added dropwise to acrylamide to adjust the neutralization degree of acrylamide to 70% to obtain acrylamide reaction monomer, and the acrylamide reaction monomer was added to the above mixed solution, the mass ratio of expanded diatomaceous earth to acrylamide was 1:2.3, the reaction temperature was controlled at 80°C, the reaction was heated for 35 minutes, and a gel reaction product was obtained. The reaction product was dried and crushed to obtain a water-retaining fertilizer.

[0024] Example 3 A method for preparing an organic-inorganic polymer water-retaining slow-release fertilizer specifically for watermelon comprises the following steps: (1) diatomaceous earth is crushed and passed through a 300-mesh sieve, first pressurized to 2 standard atmospheres, and then decompressed to 0.5 standard atmospheres to obtain expanded diatomaceous earth; Modification of expanded diatomite: Ethanol and water are mixed in a volume ratio of 8:1 to obtain a mixed solution, silane coupling agent KH-550 is added, the mass ratio of the silane coupling agent to the mixed solution is 1:90, and the mixture is stirred and mixed evenly, and then expanded diatomaceous earth is added, the mass ratio of the expanded diatomaceous earth to the silane coupling agent is 1:0.08, heated to 70° C., stirred and reacted for 3 hours, and separated, washed and dried to obtain modified expanded diatomaceous earth; (2) Add the modified expanded diatomaceous earth into distilled water at a mass volume ratio of 1 g / 200 mL, and then add N,N-methylenebisacrylamide and potassium persulfate, the mass ratio of the modified expanded diatomaceous earth, N,N-methylenebisacrylamide, and potassium persulfate is 1:1:0.5, stir evenly, let stand for 2 hours, and then filter out the expanded diatomaceous earth for later use; (3) adding the expanded diatomaceous earth obtained after filtering in step (2) to distilled water at a mass volume ratio of 1 g / 500 mL, and then adding inorganic fertilizer, wherein the mass ratio of expanded diatomaceous earth to inorganic fertilizer is 1:4.5, and the inorganic fertilizer is a mixture of potassium nitrate, magnesium sulfate, sodium hydrogen phosphate, and ammonium molybdate, and the ratio of the four is controlled at 1:1:1:3, to obtain a mixed solution; Under ice bath conditions, 2 mol / L sodium hydroxide solution was added dropwise to acrylamide to adjust the neutralization degree of acrylamide to 70% to obtain acrylamide reaction monomer, and the acrylamide reaction monomer was added to the above mixed solution, the mass ratio of expanded diatomaceous earth to acrylamide was 1:2.5, the reaction temperature was controlled at 80°C, the reaction was heated for 45 minutes, and a gel reaction product was obtained. The reaction product was dried and crushed to obtain a water-retaining fertilizer.

[0025] Example 4 A method for preparing an organic-inorganic polymer water-retaining slow-release fertilizer specifically for watermelon comprises the following steps: (1) diatomaceous earth is crushed and passed through a 300-mesh sieve, first pressurized to 2 standard atmospheres, and then decompressed to 0.5 standard atmospheres to obtain expanded diatomaceous earth; Modification of expanded diatomite: Ethanol and water are mixed in a volume ratio of 8:1 to obtain a mixed solution, silane coupling agent KH-550 is added, the mass ratio of the silane coupling agent to the mixed solution is 1:90, and the mixture is stirred and mixed evenly, and then expanded diatomaceous earth is added, the mass ratio of the expanded diatomaceous earth to the silane coupling agent is 1:0.08, heated to 70° C., stirred and reacted for 3 hours, and separated, washed and dried to obtain modified expanded diatomaceous earth; (2) Add the modified expanded diatomaceous earth into distilled water at a mass volume ratio of 1 g / 200 mL, and then add N,N-methylenebisacrylamide and potassium persulfate, the mass ratio of the modified expanded diatomaceous earth, N,N-methylenebisacrylamide, and potassium persulfate is 1:1:0.5, stir evenly, let stand for 2 hours, and then filter out the expanded diatomaceous earth for later use; (3) adding the expanded diatomaceous earth obtained after filtering in step (2) to distilled water at a mass volume ratio of 1 g / 500 mL, and then adding inorganic fertilizer, wherein the mass ratio of the expanded diatomaceous earth to the inorganic fertilizer is 1:5, and the inorganic fertilizer is a mixture of potassium nitrate, magnesium sulfate, sodium hydrogen phosphate, and ammonium molybdate, and the ratio of the four is controlled at 1:1:1:3, to obtain a mixed solution; Under ice bath conditions, 2 mol / L sodium hydroxide solution was added dropwise to acrylamide to adjust the neutralization degree of acrylamide to 70% to obtain acrylamide reaction monomer, and the acrylamide reaction monomer was added to the above mixed solution, the mass ratio of expanded diatomaceous earth to acrylamide was 1:3, the reaction temperature was controlled at 80°C, the reaction was heated for 57 minutes, and a gel reaction product was obtained. The reaction product was dried and crushed to obtain a water-retaining fertilizer.

[0026] Example 5 A method for preparing an organic-inorganic polymer water-retaining slow-release fertilizer specifically for watermelon comprises the following steps: (1) diatomaceous earth is crushed and passed through a 300-mesh sieve, first pressurized to 2 standard atmospheres, and then decompressed to 0.5 standard atmospheres to obtain expanded diatomaceous earth; Modification of expanded diatomite: Ethanol and water are mixed in a volume ratio of 8:1 to obtain a mixed solution, silane coupling agent KH-550 is added, the mass ratio of the silane coupling agent to the mixed solution is 1:90, and the mixture is stirred and mixed evenly, and then expanded diatomaceous earth is added, the mass ratio of the expanded diatomaceous earth to the silane coupling agent is 1:0.08, heated to 70° C., stirred and reacted for 3 hours, and separated, washed and dried to obtain modified expanded diatomaceous earth; (2) Add the modified expanded diatomaceous earth into distilled water at a mass volume ratio of 1 g / 200 mL, and then add N,N-methylenebisacrylamide and potassium persulfate, the mass ratio of the modified expanded diatomaceous earth, N,N-methylenebisacrylamide, and potassium persulfate is 1:1:0.5, stir evenly, let stand for 2 hours, and then filter out the expanded diatomaceous earth for later use; (3) adding the expanded diatomaceous earth obtained after filtering in step (2) to distilled water at a mass volume ratio of 1 g / 500 mL, and then adding inorganic fertilizer, wherein the mass ratio of expanded diatomaceous earth to inorganic fertilizer is 1:4, and the inorganic fertilizer is a mixture of potassium nitrate, magnesium sulfate, sodium hydrogen phosphate, and ammonium molybdate, and the ratio of the four is controlled at 1:1:1:3, to obtain a mixed solution; Under ice bath conditions, 2 mol / L sodium hydroxide solution was added dropwise to acrylamide to adjust the neutralization degree of acrylamide to 70% to obtain acrylamide reaction monomer, and the acrylamide reaction monomer was added to the above mixed solution, the mass ratio of expanded diatomaceous earth to acrylamide was 1:2, the reaction temperature was controlled at 80°C, and the reaction was heated for 30 minutes to obtain a gel reaction product, and the reaction product was dried and crushed to obtain a water-retaining fertilizer.

[0027] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that: In step (1), the expanded diatomaceous earth is not modified. The remaining steps are the same as those in Example 1.

[0028] Comparative Example 2 The difference between Comparative Example 2 and Example 4 is that: The heating reaction time in step (3) is controlled at 58 min. The remaining steps are the same as those in Example 4.

[0029] Comparative Example 3 The difference between Comparative Example 3 and Example 4 is that: The thermal reaction time in step (3) is controlled within 60 min. The remaining steps are the same as those in Example 4.

[0030] Comparative Example 4 The difference between Comparative Example 4 and Example 4 is that: The thermal reaction time in step (3) is controlled at 65 min. The remaining steps are the same as those in Example 4.

[0031] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that: No expanded diatomaceous earth is added during the fertilizer preparation process. The remaining steps are the same as those in Example 1.

[0032] Performance Testing 1. 3 g of the fertilizer prepared in Example 1 and Comparative Example 1 was mixed with 100 g of dry soil, and 60 mL of water was added. The mixture was placed in the same environmental conditions. After 24 h, 48 h, 72 h, and 96 h, the water holding capacity of the soil was tested by sampling. The results were as follows: Water holding capacity (24h) Water holding capacity (48h) Water holding capacity (72h) Water holding capacity (96h) Example 1 42.2% 38.6% 34.3% 30.7% Comparative Example 1 33.6% 26.2% 19.8% 13.3% From the above test results, it can be seen that the water retention performance of the fertilizer prepared in Comparative Example 1 is significantly lower than that in Example 1. This is because during the preparation process of the water-retaining fertilizer in Comparative Example 1, acrylamide failed to fully enter or contact the inside and surface of the diatomite pores, and could not fully undergo a cross-linking reaction to form a three-dimensional network cross-linked structure gel with water absorption performance, and the water retention performance was significantly lower than that in Example 1. 2. According to the requirements of the national standard GB / T23348-2009 for slow-release fertilizers, the dissolution effects of the fertilizers of Example 4, Example 5, and Comparative Examples 2-5 were tested in 25°C still water for 1 day, 3 days, 10 days, and 28 days. The results are as follows:

[0033] From the comparison of the slow-release effects of the above-mentioned embodiment and the comparative example, it can be obtained that the release rates of the slow-release fertilizer in the comparative example after 28 days are 3.56%, 3.27% and 3.03%, respectively, and the fertilizer is almost not released, which is far from meeting the biological needs of the plants.

[0034] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing an organic-inorganic polymer water-retaining slow-release fertilizer for watermelon, characterized in that: The following steps are involved: (1) crushing diatomaceous earth and expanding it to obtain expanded diatomaceous earth; (2) Add expanded diatomaceous earth to distilled water, then add N,N-methylenebisacrylamide and potassium persulfate. Stir well, let stand, then filter out the expanded diatomaceous earth and set aside; (3) adding the expanded diatomaceous earth obtained after filtering in step (2) into distilled water, then adding inorganic fertilizer, and then adding acrylamide reaction monomer to heat and react to obtain a gel reaction product, and drying and crushing the reaction product to obtain a water-retaining fertilizer.

2. The method for preparing an organic-inorganic polymer water-retaining slow-release watermelon fertilizer according to claim 1, characterized in that: The diatomaceous earth expansion method in step (1) is to first pressurize the diatomaceous earth under atmospheric pressure and then reduce the pressure.

3. The method for preparing an organic-inorganic polymer water-retaining slow-release watermelon fertilizer according to claim 1, characterized in that: In step (1), the expanded diatomaceous earth is subjected to modification treatment, which comprises the following steps: Ethanol and water are mixed to obtain a mixed solution, silane coupling agent KH-550 is added to the mixed solution, stirred and mixed evenly, and then expanded diatomaceous earth is added, heated and stirred for reaction, and modified expanded diatomaceous earth is obtained through separation, washing and drying.

4. The method for preparing an organic-inorganic polymer water-retaining slow-release watermelon fertilizer according to claim 3, characterized in that: The inorganic fertilizer in step (3) is a mixture of potassium nitrate, magnesium sulfate, sodium hydrogen phosphate and ammonium molybdate.

5. The method for preparing an organic-inorganic polymer water-retaining slow-release fertilizer for watermelon according to claim 4, characterized in that: The mass ratio of the potassium nitrate, magnesium sulfate, sodium hydrogen phosphate and ammonium molybdate is 1:1:1:

3.

6. The method for preparing an organic-inorganic polymer water-retaining slow-release fertilizer for watermelon according to claim 3, characterized in that: In the step (3), the mass ratio of expanded diatomaceous earth to inorganic fertilizer is 1:4-5.

7. The method for preparing an organic-inorganic polymer water-retaining slow-release fertilizer for watermelon according to claim 3, characterized in that: In the step (3), the mass ratio of expanded diatomaceous earth to acrylamide is 1:2-3.

8. The method for preparing an organic-inorganic polymer water-retaining slow-release fertilizer for watermelon according to claim 3, characterized in that: The heating reaction time in step (3) is controlled within 30-90 minutes.

9. The method for preparing an organic-inorganic polymer water-retaining slow-release fertilizer for watermelon according to claim 8, characterized in that: The heating reaction time in step (3) is controlled within 30-57 minutes.

10. An organic-inorganic polymer water-retaining slow-release fertilizer for watermelon, characterized in that: The method is prepared by any one of claims 1 to 9.

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