Compound slow-release fertilizer for promoting plant growth and preparation method of compound slow-release fertilizer

Abstract

The invention relates to the technical field of fertilizers, in particular to a compound slow-release fertilizer for promoting plant growth and a preparation method thereof. The invention provides a compound slow-release fertilizer for promoting plant growth. The compound slow-release fertilizer is prepared from the following components in parts by mass: 8 to 16 parts of wormcast, 30 to 40 parts of cow dung, 25 to 35 parts of straw, 20 to 30 parts of garden waste, 10 to 16 parts of complex microbial inoculants, 5 to 9 parts of brown sugar, 0.5 to 3.5 parts of zinc sulfate, 0.15 to 0.45 part of borax, 0.3 to 0.9 part of ferrous sulfate, 1 to 6 parts of algae and 10 to 20 parts of modified polyacrylate. Garden garbage, straw and other wastes are fully utilized to prepare the base fertilizer, the treatment pressure of the wastes is relieved, and the prepared composite slow release fertilizer can effectively promote the growth and development of plants, does not cause harm and pollution to soil and environment, and is suitable for wide popularization.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizers, and in particular to a composite slow-release fertilizer for promoting plant growth and a preparation method thereof. Background Art

[0002] Although there are many special base fertilizers and topdressing fertilizers suitable for fast-growing trees such as elm, poplar or crabapple on the market, most of them are quick-acting fertilizers with fast fertilizer effects and short duration. They are mostly applied by broadcasting or digging shallow pits and the amount of fertilizer applied is increased by the tree itself. In addition, the root system of trees is not well developed during the seedling stage, and the absorption rate of quick-acting fertilizers is low and incomplete. In the long run, it is easy to aggravate soil compaction and acidification, causing the soil fertility to decline and affecting sustainable planting.

[0003] Traditional fertilizers are prone to volatilization, loss, leaching or being fixed by the soil, which leads to low nutrient utilization efficiency. The nutrients that cannot be absorbed and utilized by plants are lost to the surrounding environment, which will seriously pollute groundwater sources and cause eutrophication of rivers, lakes and seas. In addition, long-term application of these fertilizers will also cause soil acidification or alkalization, destroy soil structure, make soil compacted, reduce fertility quality, and ultimately lead to reduced crop yields and reduced crop quality.

[0004] Therefore, there is an urgent need for a fertilizer that is easily absorbed, has a long-lasting fertilizer effect, can be efficiently utilized by plants, and is environmentally friendly. Summary of the invention

[0005] The purpose of the present invention is to provide a composite slow-release fertilizer for promoting plant growth. The composite slow-release fertilizer of the present invention can not only effectively promote the growth and development of plants and increase the nutrient release period, but also will not cause harm or pollution to the soil and the environment.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a composite slow-release fertilizer for promoting plant growth, comprising the following components in parts by weight:

[0008] 8-16 parts of earthworm manure, 30-40 parts of cow dung, 25-35 parts of straw, 20-30 parts of garden waste, 10-16 parts of compound bacterial agent, 5-9 parts of brown sugar, 0.5-3.5 parts of zinc sulfate, 0.15-0.45 parts of borax, 0.3-0.9 parts of ferrous sulfate, 1-6 parts of algae, and 10-20 parts of modified polyacrylate.

[0009] Preferably, the straw includes corn straw and / or wheat straw; the garden waste includes leaves, branches, bark and grass clippings; and the algae includes one or more of cyanobacteria, diatoms and chlorella.

[0010] Preferably, the composite bacterial agent comprises Bacillus subtilis, lactic acid bacteria and yeast;

[0011] The mass ratio of the Bacillus subtilis, the lactic acid bacteria and the yeast is 1:0.5-1.5:2-4.

[0012] Preferably, the initial viable count of the yeast is 1 to 4×10 6 cfu / g; the initial viable count of the lactic acid bacteria is 1 to 6×10 8 cfu / g; the initial viable count of Bacillus subtilis is 1 to 6×10 8 cfu / g.

[0013] Preferably, the preparation method of the modified polyacrylate comprises the following steps:

[0014] Mixing nano-silicon dioxide, polyacrylate emulsion, water and hydroxymethyl cellulose to obtain modified polyacrylate;

[0015] The mass ratio of the nano silicon dioxide, polyacrylate emulsion, water and hydroxymethyl cellulose is 1:80-90:90-100:0.2-0.8.

[0016] The present invention also provides a method for preparing the composite slow-release fertilizer, comprising the following steps:

[0017] (1) composting and fermenting earthworm manure, cow dung, straw, garden waste, composite bacterial agent, and brown sugar to obtain fermented fertilizer;

[0018] (2) mixing the fermented fertilizer, zinc sulfate, borax, ferrous sulfate, and algae to obtain a mixture; granulating and drying the mixture to obtain a compound fertilizer;

[0019] (3) The compound fertilizer and the modified polyacrylate are mixed and dried to obtain a compound slow-release fertilizer.

[0020] Preferably, in step (1), the temperature of the composting fermentation is 65-75° C.; the humidity of the composting fermentation is 55-65%; and the time of the composting fermentation is 40-50 days.

[0021] Preferably, in step (2), the drying is vacuum freeze drying; the vacuum degree of the drying is 4 to 8 Pa; the drying includes precooling and low-temperature drying; the precooling temperature is -45 to -55°C; the precooling time is 30 to 40 minutes; the low-temperature drying temperature is 30 to 40°C; and the low-temperature drying time is 40 to 50 minutes.

[0022] Preferably, in step (3), the drying is forced air drying; the drying temperature is 30 to 40° C.; and the drying time is 20 to 30 minutes.

[0023] Beneficial effects of the present invention:

[0024] The invention provides a composite slow-release fertilizer for promoting plant growth. The invention makes full use of garden garbage, straw, cow dung, earthworm castings and composite microbial agents for composting and fermentation to prepare fermented fertilizer. In the fermentation process, adding brown sugar can improve the activity of the composite microbial agent and improve the fermentation efficiency. The fermented fertilizer is mixed with zinc sulfate, borax, ferrous sulfate and algae to prepare a mixture. The zinc sulfate, borax and ferrous sulfate can provide nutrition for the growth and development of plants. The algae is rich in nutrients required for the growth of various plants, which can not only provide nutrition for the growth of plants, but also improve the vitality and stress resistance of plants. The algae also has natural plant growth regulators such as auxin and cytokinin, which can promote the development of plant roots and the growth of aboveground parts. The algae can also repair soil and improve soil structure. Finally, the mixture is mixed with modified polyacrylate to prepare the composite slow-release fertilizer, thereby increasing the nutrient release period.

[0025] The present invention makes full use of wastes such as garden garbage and straw to prepare base fertilizer, which alleviates the pressure of waste treatment. The composite slow-release fertilizer can also effectively promote the growth and development of plants, and will not cause harm or pollution to the soil and the environment, and is suitable for wide promotion. DETAILED DESCRIPTION

[0026] The present invention provides a composite slow-release fertilizer for promoting plant growth, comprising the following components in parts by weight:

[0027] 8 to 16 parts of earthworm castings, preferably 10 to 14 parts, more preferably 12 parts;

[0028] 30-40 parts of cow dung, preferably 33-37 parts, more preferably 35 parts;

[0029] 25 to 35 parts of straw, preferably 28 to 32 parts, more preferably 30 parts;

[0030] 20 to 30 parts of garden waste, preferably 23 to 27 parts, more preferably 25 parts;

[0031] 10 to 16 parts of the composite bacterial agent, preferably 12 to 14 parts, more preferably 13 parts;

[0032] 5 to 9 parts of brown sugar, more preferably 6 to 8 parts, more preferably 7 parts;

[0033] 0.5 to 3.5 parts of zinc sulfate, preferably 1.5 to 2.5 parts, more preferably 2 parts;

[0034] 0.15-0.45 parts of borax, preferably 0.25-0.35 parts, more preferably 0.30 parts;

[0035] 0.3 to 0.9 parts of ferrous sulfate, preferably 0.5 to 0.7 parts, more preferably 0.6 parts

[0036] 1 to 6 parts of algae, preferably 3 to 4 parts, more preferably 3.5 parts;

[0037] The modified polyacrylate is 10 to 20 parts, preferably 13 to 17 parts, and more preferably 15 parts.

[0038] In the present invention, the straw includes corn straw and / or wheat straw, preferably corn straw and wheat straw; the mass ratio of the corn straw to the wheat straw is 1:1 to 3, preferably 1:2;

[0039] The garden waste includes leaves, branches, bark and grass clippings;

[0040] The algae include one or more of cyanobacteria, diatoms and chlorella, preferably diatoms and / or chlorella, and more preferably diatoms and chlorella; the mass ratio of diatoms to chlorella is 1:0.5-1.5, and more preferably 1:1.

[0041] In the present invention, the composite bacterial agent includes Bacillus subtilis, lactic acid bacteria and yeast;

[0042] The Bacillus subtilis is Bacillus subtilis subsp. subtilis, purchased from the General Microbiological Center of China Microbiological Culture Collection Administration, with a collection number of CGMCC No. 21826;

[0043] The lactic acid bacteria is Enterococcus faecalis, purchased from the General Microbiological Center of China Microbiological Culture Collection Administration, with the collection number of CGMCC No.5092;

[0044] The yeast is Saccharomyces cerevisiae G1, which was purchased from the General Microbiological Center of China Microbiological Culture Collection Administration, with a collection number of CGMCC NO: 11044.

[0045] The mass ratio of the Bacillus subtilis, the lactic acid bacteria and the yeast is 1:0.5-1.5:2-4, preferably 1:0.8-1.2:2.5-3.5, and more preferably 1:1:3.

[0046] In the present invention, the initial viable count of the yeast is 1 to 4×10 6 cfu / g, preferably 2 to 3×10 6cfu / g, more preferably 2.5×10 6 cfu / g;

[0047] The initial viable count of the lactic acid bacteria is 1 to 6×10 8 cfu / g, preferably 3 to 4×10 8 cfu / g, more preferably 3.5×10 8 cfu / g;

[0048] The initial viable count of the Bacillus subtilis is 1 to 6×10 8 cfu / g, preferably 3 to 4×10 8 cfu / g, more preferably 3.5×10 8 cfu / g.

[0049] In the present invention, the preparation method of the modified polyacrylate comprises the following steps:

[0050] Mixing nano-silicon dioxide, polyacrylate emulsion, water and hydroxymethyl cellulose to obtain modified polyacrylate;

[0051] The mass ratio of the nano-silicon dioxide, polyacrylate emulsion, water and hydroxymethyl cellulose is 1:80-90:90-100:0.2-0.8, preferably 1:83-87:93-97:0.4-0.6, and more preferably 1:85:95:0.6.

[0052] In the present invention, the mixing method is ultrasound-assisted water bath heating mixing;

[0053] The mixing temperature is 90-100°C, preferably 93-97°C, preferably 95°C;

[0054] The mixing power is 150-250W, preferably 180-220W, and more preferably 200W;

[0055] The mixing time is 20 to 30 minutes, preferably 23 to 27 minutes, and more preferably 25 minutes.

[0056] The present invention also provides a method for preparing the composite slow-release fertilizer, comprising the following steps:

[0057] (1) composting and fermenting earthworm manure, cow dung, straw, garden waste, composite bacterial agent, and brown sugar to obtain fermented fertilizer;

[0058] (2) mixing compound fertilizer, zinc sulfate, borax, ferrous sulfate, and algae to obtain a mixture; granulating and drying the mixture to obtain compound fertilizer;

[0059] (3) The compound fertilizer and the modified polyacrylate are mixed and dried to obtain a compound slow-release fertilizer.

[0060] In the present invention, in step (1), the temperature of the compost fermentation is 65-75°C, preferably 68-72°C, and more preferably 70°C; the humidity of the compost fermentation is 55-65%, preferably 58-62%, and more preferably 60%; the time of the compost fermentation is 40-50d, preferably 43-47d, and more preferably 45d.

[0061] In the present invention, in step (2), the drying is vacuum freeze drying; the vacuum degree of the drying is 4 to 8 Pa, preferably 5 to 7 Pa, and more preferably 6 Pa; the drying includes precooling and low-temperature drying; the precooling temperature is -45 to -55°C, preferably -48 to -52°C, and more preferably -50°C; the precooling time is 30 to 40 min, preferably 33 to 37 min, and more preferably 35 min; the low-temperature drying temperature is 30 to 40°C, preferably 33 to 37°C, and more preferably 35°C; the low-temperature drying time is 40 to 50 min, preferably 43 to 47 min, and more preferably 45 min.

[0062] In the present invention, in step (3), the drying is forced air drying; the drying temperature is 30 to 40°C, preferably 33 to 37°C, and more preferably 35°C; the drying time is 20 to 30 min, preferably 23 to 27 min, and more preferably 25 min.

[0063] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0064] In the embodiments, comparative examples and experimental examples of the present invention, the Bacillus subtilis subsp. subtilis used was purchased from the General Microbiology Center of China National Microbiological Culture Collection Administration, with a deposit number of CGMCC No.21826; Enterococcus faecalis was purchased from the General Microbiology Center of China National Microbiological Culture Collection Administration, with a deposit number of CGMCC No.5092; and Saccharomyces cerevisiae G1 was purchased from the General Microbiology Center of China National Microbiological Culture Collection Administration, with a deposit number of CGMCC N0:11044.

[0065] Example 1

[0066] Preparation of modified polyacrylate: 0.1 kg of nano-silicon dioxide, 8.5 kg of polyacrylate emulsion, 9.5 kg of water and 0.06 kg of hydroxymethyl cellulose were mixed by ultrasonic-assisted water bath heating at a power of 200 W and a temperature of 95° C. for 25 min to obtain modified polyacrylate.

[0067] (1) 12 kg of earthworm manure, 35 kg of cow dung, 30 kg of straw (corn straw and wheat straw mixed in a mass ratio of 1:2), 25 kg of garden waste, 13 kg of composite bacterial agent, and 7 kg of brown sugar were composted and fermented at a temperature of 70° C. and a humidity of 60% for 45 days to obtain a fermented fertilizer;

[0068] The composite bacterial agent is 3.5×10 8 cfu / g Bacillus subtilis subsp. Subtilis, 3.5×10 8 cfu / g Enterococcus faecalis and 2.5×10 6 cfu / g Saccharomyces cerevisiae G1 was prepared by mixing in a mass ratio of 1:1:3;

[0069] (2) mixing the fermented fertilizer, 2 kg of zinc sulfate, 0.3 kg of borax, 0.6 kg of ferrous sulfate, and 3.5 kg of algae (diatoms and chlorella are mixed in a mass ratio of 1:1) to obtain a mixture; granulating the mixture, setting the vacuum degree to 6 Pa, precooling at -50°C for 35 minutes, and then low-temperature drying at 35°C for 45 minutes to obtain a compound fertilizer;

[0070] (3) The compound fertilizer and 15 kg of modified polyacrylate were mixed and dried at 35° C. for 25 min to obtain a compound slow-release fertilizer.

[0071] Example 2

[0072] Preparation of modified polyacrylate: 0.1 kg of nano-silica, 8 kg of polyacrylate emulsion, 10 kg of water and 0.3 kg of hydroxymethyl cellulose were mixed by ultrasonic-assisted water bath heating at a power of 250 W and a temperature of 90° C. for 30 min to obtain modified polyacrylate.

[0073] (1) 10 kg of earthworm manure, 40 kg of cow dung, 25 kg of straw (corn straw and wheat straw mixed in a mass ratio of 1:1), 30 kg of garden waste, 15 kg of composite bacterial agent, and 8 kg of brown sugar were composted and fermented at a temperature of 65° C. and a humidity of 55% for 50 days to obtain a fermented fertilizer;

[0074] The composite bacterial agent is 3×10 8 cfu / g Bacillus subtilis subsp.Subtilis, 5×108 cfu / g Enterococcus faecalis and 2×10 6 cfu / g Saccharomyces cerevisiae G1 was prepared by mixing in a mass ratio of 1:0.5:4;

[0075] (2) mixing the fermented fertilizer, 1 kg of zinc sulfate, 0.2 kg of borax, 0.8 kg of ferrous sulfate, and 5 kg of algae (diatoms and chlorella are mixed in a mass ratio of 1:1.5) to obtain a mixture; granulating the mixture, setting the vacuum degree to 4 Pa, precooling at -45°C for 40 minutes, and then low-temperature drying at 30°C for 50 minutes to obtain a compound fertilizer;

[0076] (3) The compound fertilizer and 18 kg of modified polyacrylate were mixed and dried at 35° C. for 25 min to obtain a compound slow-release fertilizer.

[0077] Example 3

[0078] Preparation of modified polyacrylate: 0.1 kg of nano-silica, 9 kg of polyacrylate emulsion, 9 kg of water and 0.6 kg of hydroxymethyl cellulose were mixed by ultrasonic-assisted water bath heating at a power of 180 W and a temperature of 100° C. for 23 min to obtain modified polyacrylate.

[0079] (1) 16 kg of earthworm manure, 22 kg of cow dung, 32 kg of straw (corn straw and wheat straw mixed in a mass ratio of 1:3), 20 kg of garden waste, 12 kg of composite bacterial agent, and 5 kg of brown sugar were composted and fermented at a temperature of 75° C. and a humidity of 65% for 40 days to obtain a fermented fertilizer;

[0080] The composite bacterial agent is 6×10 8 cfu / g Bacillus subtilis subsp.Subtilis, 1×10 8 cfu / g Enterococcus faecalis and 4×10 6 cfu / g Saccharomyces cerevisiae G1 was prepared by mixing in a mass ratio of 1:1.5:2;

[0081] (2) mixing the fermented fertilizer, 3 kg of zinc sulfate, 0.4 kg of borax, 0.3 kg of ferrous sulfate, and 2 kg of green algae to obtain a mixture; granulating the mixture, setting the vacuum degree to 8 Pa, precooling at -55°C for 30 minutes, and then low-temperature drying at 40°C for 40 minutes to obtain a compound fertilizer;

[0082] (3) The compound fertilizer and 10 kg of modified polyacrylate were mixed and dried at 35° C. for 25 min to obtain a compound slow-release fertilizer.

[0083] Comparative Example 1

[0084] The difference from Example 1 is that no earthworm castings are added, and the other steps are the same as Example 1.

[0085] Comparative Example 2

[0086] The difference from Example 1 is that cow dung is replaced by chicken dung, and the other steps are the same as Example 1.

[0087] Comparative Example 3

[0088] The difference from Example 1 is that no algae is added, and the other steps are the same as Example 1.

[0089] Comparative Example 4

[0090] The difference from Example 1 is that diatoms are replaced by green algae, and the other steps are the same as Example 1.

[0091] Comparative Example 5

[0092] The difference from Example 1 is that no modified polyacrylate is added, and the other steps are the same as Example 1.

[0093] Comparative Example 6

[0094] The difference from Example 1 is that the composite bacterial agent is replaced with 3×10 8 cfu / g Bacillus subtilis subsp. Subtilis, and the other steps are the same as those in Example 1.

[0095] Experimental Example 1

[0096] A field experiment was conducted in a nursery in Wei County, Hebei Province. The composite slow-release fertilizer described in Example 1 and Comparative Examples 1 to 6 was used as a base fertilizer, and 60 kg of base fertilizer was applied per mu. Decomposed farmyard manure was used as a blank control. One-year-old narrow-crowned black poplar seedlings were selected for planting, and the poplar seedlings were managed using conventional methods. After one year of planting, the survival rate, tree height and breast diameter growth of the narrow-crowned black poplars were statistically analyzed. The results are shown in Table 1.

[0097] Table 1 Effects of different compound slow-release fertilizers on poplar growth

[0098] Survival rate / % Tree height / m Diameter at breast height / cm Example 1 96 3.24 5.72 Comparative Example 1 94 2.87 5.15 Comparative Example 2 92 3.02 5.26 Comparative Example 3 89 2.46 4.87 Comparative Example 4 85 2.55 4.80 Comparative Example 5 94 3.01 4.92 Comparative Example 6 72 1.52 3.16 Blank control group 80 1.94 3.33

[0099] It can be seen from Table 1 that the use of the composite slow-release fertilizer described in Example 1 can significantly improve the survival rate of poplars;

[0100] It can be seen from Example 1 and Comparative Examples 1-2 that the deletion of earthworm manure or the replacement of cow dung will affect the tree height and breast diameter growth of poplars. The co-fermentation of earthworm manure and cow dung can improve the soil and increase the activity of soil microorganisms. The fermented products can provide rich nutrition for poplars, thereby promoting the growth of plants.

[0101] It can be seen from Example 1 and Comparative Examples 1-2 that the addition of diatoms can effectively improve the survival rate of poplars, promote the growth of tree height and diameter at breast height, and the combination of diatoms and Chlorella has a synergistic effect;

[0102] It can be seen from Example 1 and Comparative Example 5 that the slow-release compound fertilizer prepared by adding modified polyacrylate has little effect on the survival rate of poplars, but can increase the nutrient release period and promote the growth of tree height and diameter at breast height of poplars;

[0103] It can be seen from Example 1 and Comparative Example 6 that only using Bacillus subtilis for fermentation cannot completely decompose cow dung, straw and garden waste, and uncomposted fertilizers will harm plants, thereby reducing the survival rate of poplar trees and the growth of tree height and diameter at breast height.

[0104] Experimental Example 2

[0105] A field experiment was conducted at the Green Farm Nursery in Yanshan County, southeast of Cangzhou City, Hebei Province. The composite slow-release fertilizer described in Example 1 and Comparative Examples 1 to 6 was used as a base fertilizer, and 60 kg of base fertilizer was applied per mu to use decomposed farmyard manure; one-year-old cutting elm (Jiyu No. 2) seedlings were selected for planting, and the elm seedlings were managed using conventional methods; after one year of planting, the survival rate, tree height and breast diameter growth of the elm trees were statistically analyzed, and the results are shown in Table 2.

[0106] Table 2 Effects of different compound slow-release fertilizers on elm growth

[0107] Survival rate / % Tree height / m Diameter at breast height / cm Example 1 95 1.65 7.51 Comparative Example 1 93 1.38 6.97 Comparative Example 2 92 1.51 7.26 Comparative Example 3 84 1.39 6.09 Comparative Example 4 82 1.25 5.84 Comparative Example 5 92 1.48 6.28 Comparative Example 6 69 0.84 4.29 Blank control group 79 1.05 4.65

[0108] It can be seen from Table 2 that the use of the composite slow-release fertilizer described in Example 1 can significantly improve the survival rate of elm trees and promote the growth of tree height and breast diameter.

[0109] It can be seen from the above embodiments that the present invention provides a composite slow-release fertilizer for promoting plant growth and a preparation method thereof. The present invention makes full use of waste materials such as garden garbage and straw to prepare base fertilizer, which alleviates the pressure of waste treatment. The composite slow-release fertilizer can also effectively promote the growth and development of plants without causing harm or pollution to the soil and the environment.

[0110] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A composite slow-release fertilizer for promoting plant growth, characterized in that: The composition includes the following components in parts by weight: 8-16 parts of earthworm manure, 30-40 parts of cow dung, 25-35 parts of straw, 20-30 parts of garden waste, 10-16 parts of compound bacterial agent, 5-9 parts of brown sugar, 0.5-3.5 parts of zinc sulfate, 0.15-0.45 parts of borax, 0.3-0.9 parts of ferrous sulfate, 1-6 parts of algae, and 10-20 parts of modified polyacrylate.

2. The composite slow-release fertilizer according to claim 1, characterized in that: The straw includes corn straw and / or wheat straw; the garden waste includes leaves, branches, bark and grass clippings; and the algae includes one or more of cyanobacteria, diatoms and chlorella.

3. The composite slow-release fertilizer according to claim 2, characterized in that: The composite bacterial agent includes Bacillus subtilis, lactic acid bacteria and yeast; The mass ratio of the Bacillus subtilis, the lactic acid bacteria and the yeast is 1:0.5-1.5:2-4.

4. The composite slow-release fertilizer according to claim 3, characterized in that: The initial viable count of the yeast is 1 to 4×10 6 cfu / g; the initial viable count of the lactic acid bacteria is 1 to 6×10 8 cfu / g; the initial viable count of Bacillus subtilis is 1 to 6×10 8 cfu / g.

5. The composite slow-release fertilizer according to claim 4, characterized in that: The preparation method of the modified polyacrylate comprises the following steps: Mixing nano-silicon dioxide, polyacrylate emulsion, water and hydroxymethyl cellulose to obtain modified polyacrylate; The mass ratio of the nano silicon dioxide, polyacrylate emulsion, water and hydroxymethyl cellulose is 1:80-90:90-100:0.2-0.

8.

6. The method for preparing the composite slow-release fertilizer according to any one of claims 1 to 5, characterized in that: The steps include: (1) composting and fermenting earthworm manure, cow dung, straw, garden waste, composite bacterial agent, and brown sugar to obtain fermented fertilizer; (2) mixing the fermented fertilizer, zinc sulfate, borax, ferrous sulfate, and algae to obtain a mixture; granulating and drying the mixture to obtain a compound fertilizer; (3) The compound fertilizer and the modified polyacrylate are mixed and dried to obtain a compound slow-release fertilizer.

7. The preparation method according to claim 6, characterized in that: In step (1), the temperature of the composting fermentation is 65-75° C.; the humidity of the composting fermentation is 55-65%; and the time of the composting fermentation is 40-50 days.

8. The preparation method according to claim 7, characterized in that: In step (2), the drying is vacuum freeze drying; the vacuum degree of the drying is 4 to 8 Pa; the drying includes precooling and low-temperature drying; the precooling temperature is -45 to -55°C; the precooling time is 30 to 40 minutes; the low-temperature drying temperature is 30 to 40°C; and the low-temperature drying time is 40 to 50 minutes.

9. The preparation method according to claim 8, characterized in that: In step (3), the drying is forced air drying; the drying temperature is 30 to 40° C.; and the drying time is 20 to 30 minutes.