Fertilizer for promoting rooting and fruit swelling of crops and preparation method thereof

Abstract

The invention belongs to the technical field of compound fertilizers, and particularly relates to a fertilizer for promoting rooting and fruit swelling of crops and a preparation method thereof. The development of crop root systems and the expansion of fruits need to be supported by fertility. In order to improve the yield and quality of crops, various fertilizers need to be applied in agricultural production. The fertilizer changes the properties of soil while bringing high yield to agricultural production, and hardening and acidification are the most specific embodiment. The invention discloses a fertilizer for promoting rooting and fruit swelling of crops and a preparation method of the fertilizer, and fulvic acid, humic acid, oxamide, plant ash and trace elements are combined to meet various components and trace elements required by rooting and fruit swelling of the crops. By means of the innovative preparation method, the slow release effect of the fertilizer is improved, the utilization rate of key components in the fertilizer is increased, loss of microelements in soil is reduced, and hardening and acidification of the soil are relieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of compound fertilizers, and particularly relates to a fertilizer for promoting the rooting and fruit swelling of crops and a preparation method thereof. Background Art

[0002] With the continuous improvement of people's living standards, people have put forward higher requirements for the quantity and quality of agricultural products. To improve the yield and quality of agricultural products, it is necessary to apply various fertilizers to crops to promote the rooting and fruit swelling of crops. While fertilizers bring high yields to agriculture, they also change the nature of the soil, and soil compaction and acidification are the most specific manifestations.

[0003] In 2023, "CN116406681A" disclosed a fruit swelling and sweetening agent containing Chinese medicinal materials and its preparation and use methods. The fruit swelling and sweetening agent includes plant ash, biochemical fulvic acid potassium, Eucommia ulmoides, Poria cocos, Rehmannia glutinosa, seaweed, brown sugar, Lysimachia christinae, soybean meal, cinnamon, and white peony root. The fruit swelling and sweetening agent provided by this invention provides nutrients and organic matter for fruit trees, promotes the conversion of sugars, cell division, promotes fruit swelling, sweetening and coloring, the fruit quality is excellent, the fruit shape coloring is uniform, the peel is delicate and smooth, and at the same time activates the soil, improves the soil aggregate structure, nourishes the roots, improves quality and increases production, and it is non-toxic to humans and livestock and friendly to the natural environment. However, it has the defect of high price.

[0004] In 2025, "CN119306518A" disclosed a preparation and use method of a fertilizer for promoting plant rooting and fruit swelling. The preparation method of the fertilizer for promoting plant rooting and fruit swelling mainly ferments straw, edible mushroom residue, trehalose, and tea residue by Trichoderma harzianum and Lactobacillus plantarum, then filters the fermentation product, and the filter residue is mixed with animal manure for retting as solid organic fertilizer, and folic acid, disodium succinate, and caffeine are added to the filtrate as liquid fertilizer, and fertilization management is carried out during the plant seedling raising and transplanting periods. This invention overcomes the deficiencies of the prior art, sets the combined use of solid organic fertilizer and liquid fertilizer, effectively promotes the rooting effect during the seedling raising period of plant seeds and is convenient for later transplantation, and at the same time can effectively promote the high yield of subsequent crops and the fruit swelling, improving the economic benefits of planting. However, the fertilizer for promoting plant rooting and fruit swelling described in this invention has the problem that the effective components are easily lost.

[0005] In summary, the existing fertilizers for promoting the rooting and fruit swelling of crops generally have problems such as high loss rate and low utilization rate of key components, and are prone to soil compaction and acidification. Summary of the Invention

[0006] The technical problem to be solved by the present invention: Aiming at the problems of easy loss of key components, low utilization rate, and easy soil compaction and acidification existing in the existing fertilizers for rooting and fruit swelling.

[0007] Technical solution adopted by the present invention: A fertilizer for promoting root growth and fruit swelling of crops, characterized in that the fertilizer comprises fulvic acid, humic acid, oxamide, plant ash, and trace elements. The present invention promotes root growth and fruit swelling of crops through the compounding of fulvic acid, humic acid, oxamide, plant ash, and trace elements. Among them, the effects of each component in the fertilizer on crops are as follows:

[0008] Fulvic acid: A water-soluble grayish-black powdery substance. It is a plant growth regulator that can promote plant growth and plays an important role in drought resistance. It can improve plant stress resistance, increase yield, and improve quality. The main application objects are wheat, corn, sweet potato, millet, rice, cotton, peanut, rape, tobacco, mulberry, fruits, vegetables, etc. It mainly promotes plant life activities by regulating enzymatic action. It has the effects of increasing chlorophyll content, promoting photosynthesis, enhancing respiration, and promoting the absorption and transport of mineral elements.

[0009] Humic acid: Humic acid is a macromolecular organic substance widely present in nature and is widely used in various fields such as agriculture, forestry, animal husbandry, petroleum, chemical industry, building materials, medicine and health, and environmental protection. In agriculture, humic acid fertilizers made by combining with elements such as nitrogen, phosphorus, and potassium have functions such as fertilizer efficiency enhancement, soil improvement, stimulation of crop growth, and improvement of agricultural product quality.

[0010] Oxamide: Oxamide has certain applications in the agricultural field. It can be used to synthesize pesticides and plant growth regulators. Since it is insoluble in water, it can be used as a slow-release fertilizer to replace existing fertilizers such as urea. It has the characteristics of high nitrogen content, long-lasting fertilizer effect, and not easily causing soil compaction, and is a slow-release fertilizer with broad application prospects.

[0011] Plant ash: Plant ash is the residue after plant combustion. It is an insoluble substance. As a fertilizer, plant ash contains almost all the minerals in the plant, so it has wide applicability. Due to the light texture and alkaline nature of plant ash, it is easy to drift away with the wind when dry and easy to flow away with water when wet, so it is easy to cause nitrogen element volatilization loss when contacting with nitrogen fertilizers. Plant ash mainly has the effects of promoting root growth, preventing aphids, controlling fruit tree diseases, sterilization, and preventing wound infection.

[0012] Trace elements: Provide trace elements necessary for root growth and fruit swelling of crops.

[0013] The present invention achieves the effects of complementing each other's advantages and cooperating synergistically through the compounding of fulvic acid, humic acid, oxamide, plant ash, and trace elements, realizes the effect of promoting root growth and fruit swelling of crops, and has the characteristics of long-lasting fertilizer effect and not easily being lost.

[0014] To facilitate the understanding and implementation of the technical solution of the present invention by those skilled in the art, the present invention also has the following additional technical features.

[0015] Preferably, the mass ratio of the fulvic acid, humic acid, oxamide, plant ash, and trace elements is 1: 0.5 - 2.5: 5.0 - 15.0: 0.2 - 2.0: 0.01 - 0.06. Through comparative experiments, the inventor determined that the components in the compound fertilizer of the present invention can maximize the function of promoting root growth and fruit swelling when adopting the above-mentioned ratio. Long-term use of the compound fertilizer of the present invention can maintain the soil pH value near 7, with the least negative impact on the soil.

[0016] Preferably, the trace elements include zinc oxide, magnesium oxide, manganese dioxide, copper sulfate, and borax. The present invention uses zinc oxide, magnesium oxide, manganese dioxide, copper sulfate, and borax as trace elements. On the one hand, it can supplement the trace elements required for the growth and development of crops, and on the other hand, it can partially neutralize the acidity of fulvic acid and humic acid, maintaining the soil pH value at neutral.

[0017] The present invention also discloses a preparation method of the fertilizer for promoting root growth and fruit swelling of crops as described above. Specifically, the fertilizer is prepared through the following processes:

[0018] S1. Mix the fulvic acid, humic acid, and water evenly in a mixer to form a mixture;

[0019] S2. Extrude and granulate the mixture to form a core material;

[0020] S3. Crush the trace elements with a pulverizer to form fine trace element powder;

[0021] S4. Mix the plant ash and the fine trace element powder evenly in a mixer to form a first wall material;

[0022] S5. Crush the oxamide with a pulverizer to form a second wall material;

[0023] S6. Coat the core material and the first wall material in a coating machine to form a coated body;

[0024] S7. Spray an adhesive on the surface of the coated body to form an adhesive body;

[0025] S8. Coat the adhesive body and the second wall material in a coating machine to form the fertilizer for promoting root growth and fruit swelling of crops.

[0026] Different from the prior art's direct mixing method, the present invention uses a double-layer coating technology to prepare the fertilizer for promoting the rooting and fruit swelling of crops. First, fulvic acid, humic acid, and water are mixed evenly by a mixer to form a mixture. The mixture is extruded into pellets to form the core material. The water content of the mixture here is very crucial, generally controlled at 2-10%. The advantages are as follows: 1. Facilitate granulation and forming; 2. The particles can adhere to the first wall material; 3. Avoid the problem of easy loss of active components caused by too much water. Then, trace elements are crushed by a crusher to form fine trace element powder. Plant ash and the fine trace element powder are mixed evenly by a mixer to form the first wall material. Oxamide is crushed by a crusher to form the second wall material. Plant ash contains potassium carbonate and its aqueous solution is alkaline. Most of the trace elements are metal oxides and are alkaline, and no side reaction will occur when the two are mixed. Subsequently, the core material and the first wall material are coated in a coating machine to form a coated body. An adhesive is sprayed on the surface of the coated body to form an adhesive body. In the present invention, the first wall material of the double-layer coating is a mixture of plant ash and trace elements. Although the first wall material is alkaline and will undergo a neutralization reaction with the acidic core material, since the core material is formed by extrusion granulation and its internal structure is dense, the first wall material is not easily able to enter the interior of the core material. Coupled with the strict control of the water content of the core material, the neutralization reaction between the first wall material and the core material can be avoided, reducing the loss of active components. Spraying an adhesive on the surface of the coated body to form an adhesive body creates conditions for secondary coating and also enhances the strength of the first wall material. Finally, the adhesive body and the second wall material are coated in a coating machine to form the fertilizer for promoting the rooting and fruit swelling of crops. The present invention uses oxamide as the second wall material to wrap around the outside of the adhesive body. Due to the water-insolubility of oxamide, it can serve as a slow-release nitrogen fertilizer by itself and can also serve as a wall material to protect the core material well. During use, the outermost oxamide is damaged due to external force or long-term erosion by water, forming defects. Water will enter the interior of the compound fertilizer from the defects, pass through the plant ash and trace element layer, and finally enter the high-strength fulvic acid and humic acid layer. Gradually, a complex process of neutralization reaction between fulvic acid, humic acid and plant ash, trace elements, and slow release of nitrogen element from oxamide in an alkaline environment occurs. The overall result is to slowly provide various effective components required for crop rooting and fruit swelling. Due to its slow-release property, it is very convenient to apply and there is no need to deliberately apply it at a certain stage of the crop life cycle. During the secondary coating process, the adhesive can be sprayed on the outside of the adhesive body in several batches and the second wall material can be added in several batches to increase the thickness of the second wall material.

[0027] Preferably, the extrusion granulation process described in step S2 is carried out in a twin-screw extruder. The fertilizer for promoting the rooting and fruit swelling of crops according to the present invention belongs to a three-layer structure, and the innermost layer is a core layer composed of fulvic acid and humic acid. The periphery of the core layer is wrapped with a first wall material composed of plant ash and trace elements. The periphery of the first wall material is wrapped with a second wall material composed of oxamide. From the inside to the outside, it is acidic, approximately alkaline, and neutral in turn. That is, it not only meets the fertility requirements for promoting the rooting and fruit swelling of crops, but also realizes the slow-release effect, and reduces the negative impact on soil compaction and acidification through precise proportioning. Among them, the mechanical strength of the core layer is very important and is crucial for improving the slow-release effect of the fertilizer. The release effect can be artificially controlled by adjusting the pressure during the extrusion granulation process.

[0028] More preferably, the pressure during the extrusion granulation process is controlled to be 3-5 MPa, and the temperature is 30-50 °C. When the pressure during the extrusion granulation process is 3-5 MPa and the temperature is 30-50 °C, it can ensure that the core material has a compressive strength of 0.5-10 N, and can ensure the final slow-release effect. The extrusion granulation temperature and pressure are related. When the extrusion granulation temperature is high, the pressure will become smaller; when the extrusion granulation temperature is low, the pressure will become larger. Of course, it is also related to the water content of the core material. If the water content is high, the pressure during extrusion granulation will decrease under the same temperature conditions.

[0029] Preferably, the core material described in step S2 is cylindrical, with a diameter of 2-5 mm and a height of 3-10 mm. Since a twin-screw extruder is used for granulation, the core material obtained in the present invention will be cylindrical, and its diameter needs to be controlled to be 2-5 mm and the height to be 3-10 mm. The core material of this size has the characteristics of high extrusion efficiency during the extrusion granulation process and is more convenient to use during the application process. If the diameter is too small, the pressure during the extrusion granulation process will increase; if the diameter is too large, the particle forming will be poor.

[0030] Preferably, the passing rate of the second wall material sieved through a 200-mesh sieve in step S5 is 100%. Controlling the particle size of the second wall material can well control the effect of the second coating. When the particle size of the second wall material is smaller, the binder is coated more completely, which is more beneficial to the slow-release process. When the particle size of the second wall material is larger, the binder is coated less completely, and structural defects may occur, affecting the slow-release effect.

[0031] Preferably, the binder in step S7 is an aqueous sucrose solution. Spraying an aqueous sucrose solution on the outer surface of the coated body can improve the adhesiveness of the coated body, make it easier to bond the second wall material, make the strength of the second coating higher and the stability better. It can also enhance the strength of the first wall material and better control the release of the core material.

[0032] Further preferably, the concentration of the sucrose aqueous solution is 15-25%. Through comparative experiments, the inventors determined that when the concentration of the sucrose aqueous solution is 15-25%, the best adhesion effect can be achieved, and the oxamide powder can be firmly adhered to the outer surface of the adhesive body. The usage amount of the sucrose aqueous solution needs to meet two criteria: the adhesive body can adhere to a sufficient amount of oxamide and the adhesive bodies do not adhere to each other. Generally, the usage amount is 5-10% of the mass of the core material.

[0033] In summary, the present invention discloses a fertilizer for promoting the rooting and fruit swelling of crops and its preparation method. The fertilizer has the characteristics of low loss rate, high utilization rate, not easy to cause soil compaction and acidification, and long-lasting fertilizer effect. Specific embodiments

[0034] The present invention will be specifically described below through examples, but the present invention is not limited to these examples.

[0035] Example 1

[0036] Mixing: Add fulvic acid: 2.5 kg and humic acid: 2.8 kg to a single-cone mixer, and turn on the single-cone stirring device for mixing. After mixing for 10 minutes, slowly spray atomized water: 0.22 kg into the single-cone mixer, and continue to stir and mix for 30 minutes.

[0037] Granulation: Replace the die of the twin-screw extruder with a 3-mm aperture die, control the temperature at the extrusion end of the twin-screw extruder at 35°C, and put the mixed material into the feeding port of the twin-screw extruder. Turn on the twin-screw extruder. When there is material extruded from the small holes of the die, turn on the cutter for cutting. Control the rotation speed of the cutter to control the length of the particles extruded from the twin-screw extruder at about 6 mm to form the core material for standby.

[0038] Crushing: Replace the screen of the centrifugal crusher with a 100-mesh stainless steel screen in advance. Put copper sulfate pentahydrate: 0.02 kg into the centrifugal crusher and turn on the centrifugal crusher for crushing. The crushed copper sulfate pentahydrate is for standby.

[0039] Prepare the first wall material: Put plant ash: 0.8 kg, zinc oxide: 0.03 kg, magnesium oxide: 0.01 kg, manganese dioxide: 0.02 kg, crushed copper sulfate pentahydrate: 0.02 kg, and borax: 0.05 kg into a single-cone mixer, turn on the stirring device of the single-cone mixer, and mix evenly to form the first wall material.

[0040] Prepare the second wall material: Replace the screen of the centrifugal crusher with a 200-mesh stainless steel screen in advance. Batchwise put oxamide: 18.5 kg into the centrifugal crusher and turn on the centrifugal crusher for crushing to form the second wall material for standby.

[0041] Preparation of coated particles: Charge 0.93 kg of the first wall material into the coating machine, and start the stirring device of the coating machine. Charge 5.52 kg of the core material into the coating machine and perform coating to obtain the coated particles.

[0042] Spraying of binder: Start the stirring device of the coating machine, and spray 0.12 kg of 18.5% sucrose aqueous solution into the coating machine using an atomizer. After spraying is completed, a bonded body is formed.

[0043] Preparation of compound fertilizer: Slowly add 6.0 kg of the second wall material into the coating machine. After the second wall material is completely adhered by the bonded body, spray 0.12 kg of 30% sucrose aqueous solution into the coating machine using an atomizer. Then, slowly add another 6.0 kg of the second wall material into the coating machine, and spray 0.12 kg of 30% sucrose aqueous solution into the coating machine using an atomizer again. Finally, slowly add 6.5 kg of the second wall material into the coating machine, and continue mixing and coating for 30 minutes to obtain a fertilizer that promotes the rooting and fruit swelling of crops.

[0044] Evaluation method:

[0045] 1. Slow-release evaluation:

[0046] Weigh 100 g of deionized water and 20 g of the prepared compound fertilizer into a conical flask. Place the conical flask at room temperature and observe that the complete disintegration time of the compound fertilizer is 145 minutes. The pH after disintegration and standing for 48 hours is 6.9.

[0047] 2. Cultivate sweet potatoes in the experimental field. Apply 0.02 kg of compound fertilizer per square meter each time before planting, in the first month after transplanting, in the second month after transplanting, and in the third month after transplanting. Finally, the average mass of the sweet potatoes obtained is 0.343 kg per piece.

[0048] Example 2

[0049] The preparation process of Example 2 is basically the same as that of Example 1, except that the extrusion pressure is controlled at 3.0 MPa.

[0050] Evaluation method:

[0051] 1. Slow-release evaluation:

[0052] Weigh 100 g of deionized water and 20 g of the prepared compound fertilizer into a conical flask. Place the conical flask at room temperature and observe that the complete disintegration time of the compound fertilizer is 110 minutes. The pH after disintegration and standing for 48 hours is 6.8.

[0053] 2. Cultivate sweet potatoes in the experimental field. Apply 0.02 kg of compound fertilizer per square meter each time before planting, in the first month after transplanting, in the second month after transplanting, and in the third month after transplanting. Finally, the average mass of the sweet potatoes obtained is 0.324 kg per piece.

[0054] Example 3

[0055] The preparation process of Example 3 is basically the same as that of Example 1, except that the extrusion pressure is controlled at 5.0 MPa.

[0056] Evaluation method:

[0057] 1. Sustained-release evaluation:

[0058] Weigh 100 g of deionized water and 20 g of the prepared compound fertilizer into a conical flask, place the conical flask at room temperature, and observe that the complete disintegration time of the compound fertilizer is 190 minutes. The pH after disintegration and standing for 48 hours is 7.0.

[0059] 2. Cultivate sweet potatoes in the experimental field. Apply 0.02 kg of compound fertilizer per square meter each time before planting, in the first month after transplanting, in the second month after transplanting, and in the third month after transplanting. Finally, the average mass of the sweet potatoes obtained is 0.385 kg per piece.

[0060] Example 4

[0061] The preparation process of Example 4 is basically the same as that of Example 1, except that the twin-screw extruder is replaced with a die with a 2-mm aperture, the cutter speed is controlled, and the length of the particles extruded from the twin-screw extruder is controlled at about 3 mm to form the core material.

[0062] Evaluation method:

[0063] 1. Sustained-release evaluation:

[0064] Weigh 100 g of deionized water and 20 g of the prepared compound fertilizer into a conical flask, place the conical flask at room temperature, and observe that the complete disintegration time of the compound fertilizer is 105 minutes. The pH after disintegration and standing for 48 hours is 6.9.

[0065] 2. Cultivate sweet potatoes in the experimental field. Apply 0.02 kg of compound fertilizer per square meter each time before planting, in the first month after transplanting, in the second month after transplanting, and in the third month after transplanting. Finally, the average mass of the sweet potatoes obtained is 0.306 kg per piece.

[0066] Example 5

[0067] The preparation process of Example 5 is basically the same as that of Example 1, except that the twin-screw extruder is replaced with a die with a 5-mm aperture, the cutter speed is controlled, and the length of the particles extruded from the twin-screw extruder is controlled at about 10 mm to form the core material.

[0068] Evaluation method:

[0069] 1. Sustained-release evaluation:

[0070] Weigh deionized water: 100 g and the prepared compound fertilizer: 20 g into an Erlenmeyer flask. Place the Erlenmeyer flask at room temperature and observe that the complete disintegration time of the compound fertilizer is: 210 minutes. The pH after disintegration and standing for 48 hours is 7.0.

[0071] 2. Cultivate sweet potatoes in the experimental field. Before planting, in the first month after transplanting, in the second month after transplanting, and in the third month after transplanting, apply compound fertilizer at 0.02 kg per square meter each time. Finally, the average mass of the sweet potatoes obtained is: 0.367 kg per piece.

[0072] Comparative Example 1

[0073] The preparation process of Comparative Example 1 is basically the same as that of Example 1. The difference is that for mixing: add fulvic acid: 2.5 kg, humic acid: 2.8 kg into a single-cone mixer, slowly spray atomized water: 0.22 kg into the single-cone mixer, and continue to stir and mix for 30 minutes. Then, add plant ash: 0.8 kg, zinc oxide: 0.03 kg, magnesium oxide: 0.01 kg, manganese dioxide: 0.02 kg, copper sulfate pentahydrate: 0.02 kg, borax: 0.05 kg, and oxamide: 18.5 kg, and start the single-cone stirring device for mixing. After mixing for 10 minutes, spray 18.5% sucrose aqueous solution: 0.36 kg into the coating machine using an atomizer, and continue to stir and mix for 30 minutes to obtain a fertilizer for promoting root growth and fruit swelling of crops.

[0074] Evaluation method:

[0075] 1. Sustained-release evaluation:

[0076] Weigh deionized water: 100 g and the prepared compound fertilizer: 20 g into an Erlenmeyer flask. Place the Erlenmeyer flask at room temperature and observe that the complete disintegration time of the compound fertilizer is: 1 minute. The pH after disintegration and standing for 48 hours is 6.7.

[0077] 2. Cultivate sweet potatoes in the experimental field. Before planting, in the first month after transplanting, in the second month after transplanting, and in the third month after transplanting, apply compound fertilizer at 0.02 kg per square meter each time. Finally, the average mass of the sweet potatoes obtained is: 0.243 kg per piece.

[0078] Comparative Example 2

[0079] The preparation process of Comparative Example 2 is basically the same as that of Example 1, except that, mixing: 2.5 kg of fulvic acid, 2.8 kg of humic acid, 0.8 kg of plant ash, 0.03 kg of zinc oxide, 0.01 kg of magnesium oxide, 0.02 kg of manganese dioxide, 0.02 kg of copper sulfate pentahydrate, and 0.05 kg of borax are added to a single cone mixer, and a single cone stirring device is opened for mixing. After mixing for 10 minutes, 0.22 kg of atomized water is slowly sprayed into the single cone mixer, and stirring and mixing is continued for 30 minutes.

[0080] Granulation: Replace the twin-screw extruder with a die with a 3mm aperture, control the temperature of the extrusion end of the twin-screw extruder at 35°C, and feed the mixed material into the feeding port of the twin-screw extruder. Start the twin-screw extruder, and when material is extruded from the die hole, start the cutter for cutting. Control the cutter speed, and control the length of the pellets extruded from the twin-screw extruder to about 6mm to form the core material for standby use.

[0081] Preparation of wall material: replace the screen of the centrifugal pulverizer with a 200-mesh stainless steel screen in advance. Add 18.5 kg of oxalamide to the centrifugal pulverizer in batches, and start the centrifugal pulverizer to pulverize to form wall material for later use.

[0082] Spraying adhesive: put the prepared core material into the coating machine, turn on the stirring device of the coating machine, and use an atomizer to spray 0.12 kg of 18.5% sucrose aqueous solution into the coating machine. After spraying, an adhesive body is formed.

[0083] Preparation of compound fertilizer: slowly add 6.0 kg of wall material into the coating machine, and after the wall material is adhered to the adherend, use an atomizer to spray 0.12 kg of 30% sucrose aqueous solution into the coating machine. Then, slowly add 6.0 kg of wall material into the coating machine, and use an atomizer to spray 0.12 kg of 30% sucrose aqueous solution into the coating machine. Finally, slowly add 6.5 kg of wall material into the coating machine, continue mixing and coating for 30 minutes to obtain a fertilizer that promotes rooting and fruit expansion of crops.

[0084] Evaluation method:

[0085] 1. Sustained release evaluation:

[0086] Weigh 100 g of deionized water and 20 g of the prepared compound fertilizer into a conical flask, place the conical flask at room temperature, and observe that the compound fertilizer completely disintegrates in 95 minutes. After disintegration and 48 hours, the pH is 6.9.

[0087] 2. Sweet potatoes were cultivated in the experimental field. Before planting, in the first month of transplanting, in the second month of transplanting, and in the third month of transplanting, an average of 0.02 kg of compound fertilizer was applied per square meter. The final average weight of the sweet potatoes was 0.271 kg per piece.

[0088] Comparative Example 3

[0089] The preparation process of Comparative Example 3 is basically the same as that of Example 1, except that an equal amount of urea is used to replace oxamide as the second wall material.

[0090] Evaluation method:

[0091] 1. Sustained-release evaluation:

[0092] Weigh 100 g of deionized water and 20 g of the prepared compound fertilizer into a conical flask, place the conical flask at room temperature, and observe that the complete disintegration time of the compound fertilizer is 12 minutes. The pH after disintegration and standing for 48 hours is 6.2.

[0093] 2. Cultivate sweet potatoes in the experimental field. Apply 0.02 kg of compound fertilizer per square meter each time before planting, in the first month after transplanting, in the second month after transplanting, and in the third month after transplanting. The average mass of the finally obtained sweet potatoes is 0.227 kg per piece.

[0094] Comparative Example 4

[0095] The preparation process of Comparative Example 4 is basically the same as that of Example 1, except that when preparing the second wall material: replace the screen of the centrifugal pulverizer with a 100-mesh stainless steel screen in advance. Charge 18.5 kg of oxamide into the centrifugal pulverizer in batches, start the centrifugal pulverizer for pulverization to form the second wall material, and set it aside for use.

[0096] 1. Sustained-release evaluation:

[0097] Weigh 100 g of deionized water and 20 g of the prepared compound fertilizer into a conical flask, place the conical flask at room temperature, and observe that the complete disintegration time of the compound fertilizer is 80 minutes. The pH after disintegration and standing for 48 hours is 6.8.

[0098] 2. Cultivate sweet potatoes in the experimental field. Apply 0.02 kg of compound fertilizer per square meter each time before planting, in the first month after transplanting, in the second month after transplanting, and in the third month after transplanting. The average mass of the finally obtained sweet potatoes is 0.302 kg per piece.

Claims

1. A fertilizer for promoting root growth and fruit swelling of crops, characterized in that, The fertilizer includes fulvic acid, humic acid, oxamide, plant ash, and trace elements.

2. The fertilizer according to claim 1, characterized in that, The mass ratio of the fulvic acid, humic acid, oxamide, plant ash, and trace elements is 1: 0.5 - 2.5: 5.0 - 15.0: 0.2 - 2.0: 0.01 - 0.

06.

3. The fertilizer according to claim 1, characterized in that, The trace elements include zinc oxide, magnesium oxide, manganese dioxide, copper sulfate, and borax.

4. The fertilizer according to claim 1, wherein The fertilizer is prepared through the following processes: S1. Mix the fulvic acid, humic acid, and water evenly in a mixer to form a mixture. S2. Granulate the mixture by extrusion to form a core material. S3. Crush the trace elements with a pulverizer to form fine trace element powder. S4. Mix the plant ash and the fine trace element powder evenly in a mixer to form a first wall material. S5. Crush the oxamide with a pulverizer to form a second wall material. S6. Coat the core material and the first wall material in a coating machine to form a coated body. S7. Spray an adhesive on the surface of the coated body to form an adhered body. S8. Coat the adhered body and the second wall material in a coating machine to form the fertilizer for promoting the rooting and fruit swelling of crops.

5. The preparation method according to claim 4, characterized in that, The extrusion granulation process described in step S2 is carried out in a twin-screw extruder.

6. The preparation method according to claim 5, characterized in that, Control the pressure of the extrusion granulation process to be 3 - 5 MPa and the temperature to be 30 - 50 °C.

7. The preparation method according to claim 4, characterized in that, The core material described in step S2 is cylindrical, with a diameter of 2 - 5 mm and a height of 3 - 10 mm.

8. The preparation method according to claim 4, wherein The passing rate of the second wall material described in step S5 through a 200-mesh sieve is 100%.

9. The preparation method according to claim 4, characterized in that, The adhesive described in step S7 is a sucrose aqueous solution.

10. The preparation method according to claim 9, characterized in that, The concentration of the sucrose aqueous solution is 15 - 25%.