Compound fertilizer for promoting capillary root development and preparation method thereof

Abstract

The invention relates to the technical field of organic fertilizer manufacturing, in particular to a compound fertilizer for promoting capillary roots to be developed and a preparation method of the compound fertilizer. The invention provides a compound fertilizer for promoting capillary roots to develop. The compound fertilizer is prepared from urea, monoammonium phosphate, potassium sulfate, plant source organic matter, a soil conditioner and a rooting accelerant. The compound fertilizer provided by the invention can promote the development of capillary roots of crops, and especially can promote the development of capillary roots of Shanghai cynanchum otophyllum.

Description

Technical Field

[0001] The present invention relates to the technical field of organic fertilizer manufacturing, and particularly relates to a compound fertilizer for promoting the development of capillary roots and a preparation method thereof. Background Art

[0002] In agricultural production, the health and development degree of crop roots are directly related to the nutrient absorption, water utilization and overall growth of crops, and thus affect the yield and quality of crops. As an important part of crop roots, capillary roots have extremely high absorption activity and are of great significance for improving crop stress resistance and promoting efficient nutrient utilization. Especially in vegetable planting, such as leafy vegetables like Shanghaiqing, a developed capillary root system can significantly improve its growth rate and quality.

[0003] The current technological development in the field of organic compound fertilizers mainly focuses on functions such as nutrient slow release, compounding of microbial agents and soil improvement. In the prior art, although conventional chemical compound fertilizers can provide basic nutrients, long-term use is likely to cause soil compaction and low utilization rate of trace elements. Some organic fertilizers improve the persistence of fertilizer efficiency by adding fermentation materials or slow-release structures, but there are still problems such as incomplete composting and unstable activity of bacterial strains, which may inhibit the normal development of capillary roots.

[0004] Regarding the technology for promoting the growth of capillary roots, traditional methods rely on chemically synthesized rooting agents (such as naphthalene acetic acid, indole butyric acid), and these substances are likely to remain and may disrupt the soil microbial balance. Although some studies have tried to use natural substances such as alginate oligosaccharides and fulvic acid for root promotion, the synergistic mechanism with soil improvers is not yet clear, and there is a lack of targeted formulation design for the growth of capillary roots of specific crops (such as Shanghaiqing).

[0005] Therefore, in the technical field of organic fertilizer manufacturing, it is particularly important to provide an improved compound fertilizer for promoting the development of capillary roots. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a compound fertilizer for promoting the development of capillary roots, which can significantly promote the growth of capillary roots of crops.

[0007] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0008] In the first aspect, the present invention provides a compound fertilizer for promoting the development of capillary roots, and the compound fertilizer includes urea, monoammonium phosphate, potassium sulfate, plant-derived organic matter, a soil improver and a root growth promoter.

[0009] Preferably, the plant-derived organic matter includes corn straw and rapeseed cake.

[0010] Preferably, the soil improver includes molybdenum powder, selenium powder, brassinolide and diatomite.

[0011] Preferably, the rooting promoter includes selenium powder, oligosaccharide alginate, fulvic acid and deionized water.

[0012] Preferably, the preparation method of brassinolide includes the following steps:

[0013] (1) After low-temperature drying rape pollen and sieving to remove impurities, raw materials are obtained.

[0014] (2) The raw materials obtained in step (1) are mixed with ethanol and heated to 50 °C for extraction. The extraction is carried out 3 times, and the extraction time is 2 h. The filtrate is collected.

[0015] (3) After filtering the filtrate obtained in step (2), it is concentrated to 1 / 10 of the original volume to obtain a crude extract.

[0016] (4) The crude extract obtained in step (3) is purified by silica gel column chromatography, gradient elution is carried out with ethanol, monitored by HPLC, and the eluate containing brassinolide is collected.

[0017] (5) The eluate obtained in step (4) is concentrated to a viscous state, then n-hexane and ethyl acetate are added for crystallization, and left standing at 4 °C for 24 h to obtain a crystalline substance.

[0018] (6) After filtering the crystalline substance obtained in step (5), it is freeze-dried to obtain a white powder.

[0019] More preferably, the preparation method of brassinolide includes the following steps:

[0020] (1) After low-temperature drying (temperature < 40 °C, humidity < 5%) the fresh pollen of rape in the full-bloom stage and sieving through an 80-mesh sieve to remove impurities, raw materials are obtained.

[0021] (2) The raw materials obtained in step (1) are mixed with ethanol with a concentration of 70 - 80% according to a volume ratio of 1:10, heated to 50 °C for extraction. The extraction is carried out 3 times, and the extraction time is 2 h. The filtrate is collected.

[0022] (3) After filtering the filtrate obtained in step (2), it is concentrated (50 °C, -0.08 MPa) to 1 / 10 of the original volume to obtain a crude extract.

[0023] (4) The crude extract obtained in step (3) is purified by silica gel column (200 - 300 mesh) chromatography, gradient elution is carried out with ethanol (ethanol-water mixture) (30% → 70%), monitored by HPLC, and the eluate containing brassinolide is collected.

[0024] (5) Concentrate the eluate obtained in step (4) to a viscous state, add n-hexane and ethyl acetate with a volume ratio of 1:1 for crystallization, and let it stand at 4°C for 24 h to obtain a crystalline substance;

[0025] (6) Filter the crystalline substance obtained in step (5), and freeze-dry it (-40°C, vacuum degree 10 Pa) to obtain a white powder (purity ≥ 90%), which is brassinolide.

[0026] Preferably, the mass ratio of corn straw to rapeseed cake in the plant-derived organic matter is 1:1.

[0027] Preferably, the mass ratio of molybdenum powder, selenium powder, brassinolide and diatomite in the soil conditioner is 0.5 - 2:0.1 - 0.5:2 - 6:820 - 910.

[0028] Preferably, the mass ratio of selenium powder, alginate oligosaccharide, fulvic acid and deionized water in the rooting promoter is 0.1 - 0.5:1 - 5:5 - 10:870 - 930.

[0029] Preferably, by mass, the compound fertilizer includes 10 - 30 parts of urea, 10 - 25 parts of monoammonium phosphate, 5 - 20 parts of potassium sulfate, 5 - 20 parts of plant-derived organic matter, 5 - 10 parts of soil conditioner and 1 - 5 parts of rooting promoter.

[0030] In the second aspect, a preparation method of the compound fertilizer of the present invention is provided. The preparation method is: mix urea, monoammonium phosphate and potassium sulfate evenly; add the plant-derived organic matter and stir well; then add the soil conditioner and continue to stir evenly; finally add the rooting promoter and stir evenly; add deionized water to adjust the pH to neutral, and obtain it by extrusion granulation, screening and drying.

[0031] In the third aspect, a compound fertilizer for promoting the development of fine roots of Shanghaiqing is provided, including the compound fertilizer of the present invention.

[0032] In the fourth aspect, an application of the compound fertilizer of the present invention in promoting the growth of fine roots of Shanghaiqing is provided.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] The soil conditioner of the present invention containing specific substances can optimize the rhizosphere microenvironment, while the rooting promoter containing specific substances can directly activate the capillary root differentiation signaling pathway, forming a "soil-root" two-way regulation network, achieving a double improvement in the number and function of capillary roots. In particular, it can promote the development of capillary roots in leafy vegetables such as Shanghaiqing, and can reduce the environmental risk of chemical synthetic substances while enhancing the absorption capacity of capillary roots. The applicant speculates that this may be because the combination of the soil conditioner and the rooting promoter forms a "carrier-signal-nutrient" ternary synergistic network: on the one hand, first of all, diatomite, as a porous carrier, adsorbs alginate oligosaccharides and fulvic acid in the rooting promoter, delays their degradation, and realizes the targeted release of active ingredients (rhizosphere pH-responsive release); in addition, fulvic acid promotes the proliferation of rhizosphere Actinobacteria, and its metabolites (such as strigolactones) and brassinolide synergistically regulate root architecture; furthermore, fulvic acid binds to the surface hydroxyl groups of diatomite to form an organic-inorganic composite colloid, enhancing the adsorption capacity of selenium and molybdenum. On the other hand, brassinolide and alginate oligosaccharides synergistically activate root meristem-related genes (such as WOX5, SCR) through MAPK-ARF signal crosstalk, increasing the meristem speed of capillary roots. On the third hand, the co-diffusion system formed by the substances adsorbed by diatomite and the substances chelated by fulvic acid can match the absorption rhythm of capillary roots.

[0035] The reason why the compound fertilizer of the present invention can promote the development of crop capillary roots is mainly attributed to its scientifically formulated multiple components and their synergistic effects. For example, urea, monoammonium phosphate, and potassium sulfate in the compound fertilizer provide the basic nutrient elements (nitrogen, phosphorus, potassium) required for crop growth, which are the material basis for root growth and development. Another example is that the addition of plant-derived organic matter improves the soil structure and increases the soil organic matter content, creating a good soil environment for root growth. Another example is that when the soil conditioner and the rooting promoter are used in combination, they can play a more significant synergistic effect and jointly promote the development of crop capillary roots. The soil conditioner creates good external conditions for root growth by improving the soil environment and providing necessary trace elements. The rooting promoter directly acts on root cells, promoting cell division and elongation, especially stimulating the formation and development of capillary roots. This combination of internal and external methods enables the roots to obtain more comprehensive support and promotion during growth, thereby achieving the rapid growth and healthy development of capillary roots. Detailed implementation manners

[0036] The following will specifically describe the present invention in combination with the detailed implementation manners and examples, and the advantages and various effects of the present invention will be presented more clearly therefrom. Those skilled in the art should understand that these detailed implementation manners and examples are used to illustrate the present invention, rather than limiting the present invention.

[0037] Next, the technical solutions of the present invention will be described in conjunction with embodiments. However, the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0038] In the embodiment of the present invention, the molybdenum powder is purchased from Zhengzhou Xingyan Mining Co., Ltd., the molybdenum content is ≥99.95%, the mesh number is 200 meshes, and the CAS number is 7439-98-7. The selenium powder is purchased from Hebei Tengshuang Metal Materials Co., Ltd., the content of the active ingredient is 99.999%, the mesh number is 15000 meshes, and the CAS number is 7782-49-2.

[0039] In the embodiment of the present invention, the preparation method of the soil conditioner is as follows:

[0040] Soak the selenium powder in 0.1 mol / L citric acid solution for 2 h; dry the diatomite at 120 °C for 2 h and then cool it; prepare a 10% brassinolide mother liquor (mass concentration) with anhydrous ethanol for the brassinolide.

[0041] Mix the molybdenum powder, the treated selenium powder and the treated diatomite in a three-dimensional mixer (25 rpm) for 30 min to obtain a mixture; spray the brassinolide mother liquor into the mixture, synchronously atomize and add 5% polyethylene glycol and continue to mix for 20 min until the humidity is uniform (moisture ≤5%); sterilize with ultraviolet light (265 nm) for 30 min; obtain the soil conditioner.

[0042] In the embodiment of the present invention, the preparation method of the rooting promoter is as follows:

[0043] Mix the selenium powder and 1 mol / L hydrochloric acid at a ratio of 1:5 (w / v), stir at 60 °C for 2 h to generate a selenic acid solution, and adjust the pH to 6.0 - 6.5 with NaOH.

[0044] Ultrafilter and purify the alginate oligosaccharide (cut-off molecular weight 5000 Da), and prepare a 10% aqueous solution to obtain an alginate oligosaccharide solution.

[0045] Grind the fulvic acid to 200 meshes and prepare a 15% fulvic acid suspension with deionized water.

[0046] Add deionized water to the reaction kettle and heat it to 50 °C; then sequentially add the alginate oligosaccharide solution, the fulvic acid suspension and the selenic acid solution obtained by the above treatment, and stir magnetically (1200 rpm) for 40 min until completely dissolved; obtain the rooting promoter.

[0047] It should be noted that the dilution factor of the rooting promoter during use is 500 - 1000 times.

[0048] In an embodiment of the present invention, the preparation method of brassinolide comprises the following steps:

[0049] (1) After low-temperature drying (temperature < 40°C, humidity < 5%) of fresh pollen during the full-bloom stage of rape, it is sieved through an 80-mesh sieve to remove impurities, obtaining raw materials;

[0050] (2) The raw materials obtained in step (1) are mixed with ethanol with a concentration of 70 - 80% according to a volume ratio of 1:10, heated to 50°C for extraction, the number of extraction times is 3 times, the extraction time is 2 h, and the filtrate is collected;

[0051] (3) After filtering the filtrate obtained in step (2), it is concentrated (50°C, -0.08 MPa) to 1 / 10 of the original volume, obtaining a crude extract;

[0052] (4) The crude extract obtained in step (3) is purified by silica gel column chromatography (200 - 300 mesh), gradient elution (30% → 70%) is carried out with ethanol (ethanol - water mixture), monitored by HPLC, and the eluate containing brassinolide is collected;

[0053] (5) After the eluate obtained in step (4) is concentrated to a viscous state, n-hexane and ethyl acetate with a volume ratio of 1:1 are added for crystallization, and it is left standing at 4°C for 24 h to obtain crystals;

[0054] (6) After filtering the crystals obtained in step (5), freeze-drying (-40°C, vacuum degree 10 Pa) is carried out to obtain a white powder (purity ≥ 90%), which is brassinolide.

[0055] It should be noted that the application method of the compound fertilizer in the embodiment of the present invention is as follows:

[0056] If it is for foliar spraying, the dilution multiple is 800 - 1000 times.

[0057] If it is for root irrigation / drip irrigation, the dilution multiple is 500 - 800 times.

[0058] Example 1

[0059] This example provides a compound fertilizer for promoting the development of capillary roots. According to the mass parts, the compound fertilizer comprises 10 parts of urea, 10 parts of monoammonium phosphate, 5 parts of potassium sulfate, 5 parts of plant-derived organic matter, 5 parts of soil conditioner, and 1 part of root-promoting agent.

[0060] The plant-derived organic matter includes corn straw and rapeseed cake; the mass ratio of corn straw to rapeseed cake in the plant-derived organic matter is 1:1.

[0061] The soil conditioner includes molybdenum powder, selenium powder, brassinolide and diatomite; the mass ratio of molybdenum powder, selenium powder, brassinolide and diatomite in the soil conditioner is 0.5:0.1:2:820.

[0062] The root promoting agent includes selenium powder, alginate oligosaccharide, fulvic acid and deionized water; the mass ratio of selenium powder, alginate oligosaccharide, fulvic acid and deionized water in the root promoting agent is 0.1:1:5:870.

[0063] The dilution multiple of the root promoting agent is 500 times.

[0064] Example 2

[0065] This example provides a compound fertilizer for promoting the development of capillary roots. By mass, the compound fertilizer includes 30 parts of urea, 25 parts of monoammonium phosphate, 20 parts of potassium sulfate, 20 parts of plant-derived organic matter, 10 parts of soil conditioner and 5 parts of root promoting agent.

[0066] The plant-derived organic matter includes corn straw and rapeseed cake; the mass ratio of corn straw and rapeseed cake in the plant-derived organic matter is 1:1.

[0067] The soil conditioner includes molybdenum powder, selenium powder, brassinolide and diatomite; the mass ratio of molybdenum powder, selenium powder, brassinolide and diatomite in the soil conditioner is 2:0.5:6:910.

[0068] The root promoting agent includes selenium powder, alginate oligosaccharide, fulvic acid and deionized water; the mass ratio of selenium powder, alginate oligosaccharide, fulvic acid and deionized water in the root promoting agent is 0.5:5:10:930.

[0069] The dilution multiple of the root promoting agent is 1000 times.

[0070] Example 3

[0071] This example provides a compound fertilizer for promoting the development of capillary roots. By mass, the compound fertilizer includes 25 parts of urea, 20 parts of monoammonium phosphate, 15 parts of potassium sulfate, 8 parts of plant-derived organic matter, 6 parts of soil conditioner and 4 parts of root promoting agent.

[0072] The plant-derived organic matter includes corn straw and rapeseed cake; the mass ratio of corn straw and rapeseed cake in the plant-derived organic matter is 1:1.

[0073] The soil conditioner includes molybdenum powder, selenium powder, brassinolide and diatomite; the mass ratio of molybdenum powder, selenium powder, brassinolide and diatomite in the soil conditioner is 1.25:0.3:4:865.

[0074] The rooting promoter includes selenium powder, oligosaccharide alginate, fulvic acid and deionized water; the mass ratio of selenium powder, oligosaccharide alginate, fulvic acid and deionized water in the rooting promoter is 0.3:3:7.5:900.

[0075] The dilution multiple of the rooting promoter is 700 times.

[0076] Example 4

[0077] This example provides a preparation method of compound fertilizer. The preparation method is as follows: mix urea, monoammonium phosphate and potassium sulfate evenly; add plant-derived organic matter and stir well; then add a soil conditioner and continue to stir evenly; finally, add a rooting promoter and stir evenly; add deionized water to adjust the pH to neutral, and obtain the product through extrusion granulation, screening and drying.

[0078] Comparative Example 1

[0079] This comparative example is the same as Example 3, except that: fulvic acid is replaced by humic acid.

[0080] Comparative Example 2

[0081] This comparative example is the same as Example 3, except that: brassinolide is not added.

[0082] Comparative Example 3

[0083] This comparative example is the same as Example 3, except that: the rooting promoter is not added.

[0084] Experiment 1: Application effect

[0085] Test samples: Compound fertilizers prepared according to the preparation method of Example 4 in Examples 1-3 and Comparative Examples 1-3, with a dilution multiple of 900 times.

[0086] Experimental method: The experiment was carried out in Meijin Vegetable Planting Garden, Zhouzhi County, Xi'an City, Shaanxi Province. There were 6 plots in total for the experiment, and each plot corresponded to a test sample. The plot area was 24m 2 , and the distance between each plot was 60 cm, the row spacing was 50 cm, and the plant spacing was 35 cm. No replicates were set. The test crop was organic Shanghaiqing. Fertilization started from the seedling stage of Shanghaiqing, and it was sprayed once every 15 days for 2 times. It was managed according to the conventional method, and all experimental management methods were the same. After the organic Shanghaiqing was harvested, the plant height, number of leaves per plant and weight per plant of the organic Shanghaiqing obtained from the 6 plots were measured respectively. And the root hair number at 25 days after emergence (randomly dig 10 plants from each plot and take the average root hair number per cm root segment) and the root length at 25 days after emergence (randomly dig 10 plants from each plot and take the average root length) were counted.

[0087] Experimental results: As shown in Tables 1, 2 and 3 below.

[0088] Statistical Results of Root Hair Numbers in Table 1

[0089]

[0090] Statistical Results of Root Lengths in Table 2

[0091]

[0092]

[0093] Application Effects of Compound Fertilizers in Each Group in Table 3

[0094] Experimental group Plant height (cm) Number of leaves per plant (pcs) Weight per plant (g) Example 1 20.1 10 31.3 Example 2 20.6 11 30.5 Example 3 26.2 14 35.2 Comparative example 1 15.3 8 25.1 Comparative example 2 15.0 7 24.6 Comparative example 3 12.0 6 18.7

[0095] To further illustrate the beneficial effects of the present invention, in the embodiments of the present invention, molybdenum powder, selenium powder, brassinolide, diatomite and alginate oligosaccharide are respectively replaced with other similar substances with similar properties, and the root hair numbers and root lengths are statistically counted according to the method in Experiment 1, and their application effects are verified. The results are similar to those in Comparative Example 1 above.

[0096] To further illustrate the beneficial effects of the present invention, in the embodiments of the present invention, molybdenum powder, selenium powder, diatomite, alginate oligosaccharide and fulvic acid are not added respectively, and the root hair numbers and root lengths are statistically counted according to the method in Experiment 1, and their application effects are verified. The results are similar to those in Comparative Example 2 above.

[0097] To further illustrate the beneficial effects of the present invention, in the embodiments of the present invention, no soil conditioner is added, and the root hair numbers and root lengths are statistically counted according to the method in Experiment 1, and their application effects are verified. The results are similar to those in Comparative Example 3 above.

[0098] As can be seen from Table 1 and Table 2, the average number of root hairs per cm root segment of Shanghaiqing applying the compound fertilizer of the present invention is 186.3 - 257.5, and the average root length is 15.2 - 18.6. Both the average number of root hairs and the average root length are superior to those of the compound fertilizer without applying the formula system of the present invention. Among them, the compound fertilizer of Embodiment 3 of the present invention has a significant promoting effect on the growth of the roots of Shanghaiqing. Not only does Shanghaiqing have a large number of root hairs, but also the root length is long.

[0099] As can be seen from Table 3, from the application effects, it can be seen that the plant height of Shanghaiqing applying the compound fertilizer of the present invention is higher, the number of leaves per plant is more, and the weight per plant is heavier. It shows that the compound fertilizer of the present invention can increase the plant height, the number of leaves per plant and the weight per plant of Shanghaiqing. Among them, the compound fertilizer of Embodiment 3 of the present invention has a more significant effect on increasing the plant height, the number of leaves per plant and the weight per plant of Shanghaiqing.

[0100] As can be seen from Experiment 1, the soil conditioner of the present invention containing specific substances can optimize the rhizosphere microenvironment, while the rooting promoter containing specific substances can directly activate the capillary root differentiation signaling pathway, forming a "soil-root" bidirectional regulation network, achieving a double improvement in the number and function of capillary roots. In particular, it can promote the development of capillary roots in leafy vegetables such as Shanghaiqing, and can reduce the environmental risk of chemical synthetic substances while enhancing the absorption capacity of capillary roots. The applicant speculates that this may be because the combination of the soil conditioner and the rooting promoter forms a "carrier-signal-nutrient" ternary synergistic network: on the one hand, first, diatomite, as a porous carrier, adsorbs alginate oligosaccharides and fulvic acid in the rooting promoter, delays their degradation, and realizes the targeted release of active ingredients (rhizosphere pH-responsive release); in addition, fulvic acid promotes the proliferation of rhizosphere Actinobacteria, and its metabolites (such as strigolactones) and brassinolide synergistically regulate the root system architecture; furthermore, fulvic acid binds to the surface hydroxyl groups of diatomite to form an organic-inorganic composite colloid, enhancing the adsorption capacity of selenium and molybdenum. On the other hand, brassinolide and alginate oligosaccharides synergistically activate root meristem-related genes (such as WOX5, SCR) through MAPK-ARF signal cross-talk, increasing the meristem speed of capillary roots by 2-3 times. On the other hand, the co-diffusion system formed by the substances adsorbed by diatomite and the substances chelated by fulvic acid can match the absorption rhythm of capillary roots.

[0101] The reason why the compound fertilizer of the present invention can promote the development of crop capillary roots is mainly attributed to its scientifically formulated various components and their synergistic effects. For example, urea, monoammonium phosphate and potassium sulfate in the compound fertilizer provide the basic nutrient elements (nitrogen, phosphorus, potassium) required for crop growth, and these elements are the material basis for root growth and development. Another example is that the addition of plant-derived organic matter improves the soil structure and increases the organic matter content of the soil, creating a good soil environment for root growth. Another example is that when the soil conditioner and the rooting promoter are used in combination, they can play a more significant synergistic effect and jointly promote the development of crop capillary roots. The soil conditioner creates good external conditions for root growth by improving the soil environment and providing necessary trace elements. The rooting promoter directly acts on root cells, promoting cell division and elongation, especially stimulating the formation and development of capillary roots. This combination of internal and external methods enables the roots to obtain more comprehensive support and promotion during growth, thus achieving the rapid and healthy development of capillary roots.

[0102] It should be understood that the present invention disclosed is not limited to the specific methods, schemes and substances described, as these can vary. It should also be understood that the terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the scope of the present invention, which is only limited by the appended claims.

[0103] Those skilled in the art will also recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. These equivalents are also encompassed by the appended claims. It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment highlighting the differences from other embodiments. For the same or similar parts among the various embodiments, reference may be made to each other.

Claims

1. A compound fertilizer for promoting well-developed capillary roots, characterized in that, The compound fertilizer includes urea, monoammonium phosphate, potassium sulfate, plant-derived organic matter, soil conditioner, and root-promoting agent.

2. The compound fertilizer according to claim 1, wherein The soil conditioner includes molybdenum powder, selenium powder, brassinolide, and diatomite.

3. The compound fertilizer according to claim 1, characterized in that, The root-promoting agent includes selenium powder, alginate oligosaccharide, fulvic acid, and deionized water.

4. The compound fertilizer according to claim 2, characterized in that, The preparation method of the brassinolide includes the following steps: (1) Low-temperature dry the rape pollen, sieve to remove impurities to obtain the raw material; (2) Mix the raw material obtained in step (1) with ethanol, heat to 50 °C for extraction, the number of extractions is 3 times, the extraction time is 2 h, and collect the filtrate; (3) Filter the filtrate obtained in step (2), concentrate to 1 / 10 of the original volume to obtain the crude extract; (4) Purify the crude extract obtained in step (3) by silica gel column chromatography, perform gradient elution with ethanol, monitor by HPLC, and collect the eluate containing brassinolide; (5) Concentrate the eluate obtained in step (4) to a viscous state, add n-hexane and ethyl acetate for crystallization, stand at 4 °C for 24 h to obtain the crystalline substance; (6) Filter the crystalline substance obtained in step (5), freeze-dry to obtain a white powder.

5. The compound fertilizer according to claim 2, wherein, The mass ratio of molybdenum powder, selenium powder, brassinolide, and diatomite in the soil conditioner is 0.5 - 2:0.1 - 0.5:2 - 6:820 - 910.

6. The compound fertilizer according to claim 3, characterized in that, The mass ratio of selenium powder, alginate oligosaccharide, fulvic acid, and deionized water in the root-promoting agent is 0.1 - 0.5:1 - 5:5 - 10:870 - 930.

7. The compound fertilizer according to claim 1, wherein By mass fraction, the compound fertilizer includes 10 - 30 parts of urea, 10 - 25 parts of monoammonium phosphate, 5 - 20 parts of potassium sulfate, 5 - 20 parts of plant-derived organic matter, 5 - 10 parts of soil conditioner, and 1 - 5 parts of root-promoting agent.

8. The preparation method of the compound fertilizer according to any one of claims 1-7, characterized in that, The preparation method is as follows: Mix urea, monoammonium phosphate, and potassium sulfate evenly; add plant-derived organic matter and stir well; then add the soil conditioner and continue to stir evenly; finally add the root-promoting agent and stir evenly; add deionized water to adjust the pH to neutral, and obtain the product through extrusion granulation, screening, and drying.

9. A compound fertilizer for promoting well-developed fine roots of Shanghaiqing, characterized in that, It includes the compound fertilizer according to any one of claims 1 - 7.

10. Application of the compound fertilizer according to any one of claims 1 - 7 in promoting the growth of fine roots of Shanghaiqing.

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