A tea tree plug seedling substrate and a preparation method thereof

Abstract

This invention relates to the field of seedling substrates and discloses a tea tree plug tray seedling substrate and its preparation method. The tea tree plug tray seedling substrate includes: decomposed pine needles, composite modified porous biochar, vermiculite, perlite, and river sand. The composite modified porous biochar is prepared by combining a ternary copolymer superabsorbent resin obtained by aqueous solution polymerization of acrylic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid with the modified porous biochar. The modified porous biochar is prepared by high-temperature pyrolysis and potassium hydroxide etching of corn stalks, followed by impregnation of the porous biochar with a modified impregnating agent prepared by transesterification and polycondensation of dimethyl terephthalate, ethylene glycol, PEG2000, and phosphoric acid. This invention adds composite modified porous biochar to replace non-renewable resources such as peat moss, while providing excellent water absorption and retention capacity, which is beneficial to the growth and development of tea trees.

Description

Technical Field

[0001] This invention belongs to the field of seedling substrate technology, specifically relating to a tea tree plug seedling substrate and its preparation method. Background Technology

[0002] Tea is a perennial economic crop, and tea plays an important role in my country's economy, serving as a major source of income for many farmers in mountainous areas. Tea possesses various pharmacological effects, promoting tea consumption and the development of the tea industry. In tea production, seedling cultivation is the primary step, and the quality of seedlings is fundamental to early and high yields in tea gardens. Short-spindle open-field cuttings are currently the most common method for propagating superior tea varieties, preserving the original excellent traits of the tea cultivar. However, the seedling cultivation cycle is long, generally requiring 12-14 months, and it necessitates covering the cutting bed with subsoil, which is both labor-intensive and time-consuming, and also damages the ecological environment. With the rapid development of factory-style seedling production, compared with conventional open-field cutting propagation, factory-style tray seedling production of tea trees can shorten the seedling production cycle to about 6 months, enabling two seasons of tea seedlings to be produced per year, improving land utilization, and has been widely used in production. However, tray seedling production is affected by many factors such as substrate, temperature, and humidity. Among them, the substrate has a particularly important impact on the quality of seedling production and is the key to seedling production. A good substrate should be loose and porous, rich in nutrients, have good performance, and be lightweight, which is conducive to the growth and development of seedlings. Moreover, climate change and drought are the main environmental problems faced by seedling production. Water is a basic element for plant growth, and it is very important to improve its water use efficiency, especially in arid areas, where water loss is mainly due to seepage and evaporation. These processes can lead to serious nutrient loss and economic losses of soil and water. Summary of the Invention

[0003] To address the shortcomings mentioned in the background art, the present invention aims to provide a tea tree seedling tray substrate and its preparation method, which combines decomposed pine needles, composite modified porous biochar, vermiculite, perlite, and river sand. The fibrous structure of the decomposed pine needles, along with vermiculite, perlite, and river sand, creates good aeration and drainage channels. The composite modified porous biochar replaces non-renewable resources such as peat moss, while providing excellent water absorption and retention capacity, which is beneficial to the growth and development of tea trees.

[0004] The objective of this invention can be achieved through the following technical solutions: A substrate for raising tea tree seedlings in plug trays comprises the following components in parts by weight: 20-40 parts of decomposed pine needles, 10-20 parts of composite modified porous biochar, 5-15 parts of vermiculite, 5-15 parts of perlite, and 5-15 parts of river sand. The composite modified porous biochar is made by combining a ternary copolymer superabsorbent resin obtained by aqueous solution polymerization of acrylic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid with modified porous biochar. The modified porous biochar is prepared by pyrolysis of corn stalks at high temperature and etching with potassium hydroxide. Then, the porous biochar is impregnated with a modified impregnating agent prepared by transesterification and polycondensation of dimethyl terephthalate, ethylene glycol, PEG2000 and phosphoric acid.

[0005] Preferably, the preparation method of the composite modified porous biochar includes the following steps: Acrylic acid was added to an aqueous solution of potassium hydroxide and stirred. Then, an aqueous solution of acrylamide and an aqueous solution of 2-acrylamido-2-methylpropanesulfonic acid were added and mixed evenly under magnetic stirring. The mixture was then heated to 50°C and an aqueous solution of N,N'-methylenebisacrylamide was added. After mixing evenly, modified porous biochar was added and the temperature was raised to 60°C. An aqueous solution of ammonium persulfate was slowly added dropwise and the mixture was allowed to react for 3 hours. After the reaction was completed, the biochar was washed, dried, and sieved to obtain the composite modified porous biochar.

[0006] Preferably, the concentration of the potassium hydroxide aqueous solution is 0.243 g / mL; the concentration of the acrylamide aqueous solution is 0.2 g / mL; the concentration of the 2-acrylamido-2-methylpropanesulfonic acid aqueous solution is 0.2 g / mL; the concentration of the N,N'-methylenebisacrylamide aqueous solution is 0.0024 g / mL; and the concentration of the ammonium persulfate aqueous solution is 0.016 g / mL.

[0007] Preferably, the addition ratio of the potassium hydroxide aqueous solution, acrylic acid, acrylamide aqueous solution, 2-acrylamido-2-methylpropanesulfonic acid aqueous solution, N,N'-methylenebisacrylamide aqueous solution, modified porous biochar and ammonium persulfate aqueous solution is 2mL:0.8mL:1mL:1mL:1mL:1~2g:1mL.

[0008] Preferably, the method for preparing the modified porous biochar includes the following steps: (1) Take dimethyl terephthalate and heat it to 150°C until it is completely dissolved. Then add ethylene glycol and anhydrous zinc acetate. Heat it to 180°C under magnetic stirring. Stop the reaction when the generated methanol stops evaporating. Prepare dihydroxyethyl terephthalate. (2) PEG2000, phosphoric acid, triphenyl phosphite and antimony trioxide catalyst were added to dihydroxyethyl terephthalate, nitrogen protection was turned on, and the mixture was heated to 260~280℃ and vacuumed to carry out polycondensation reaction to prepare the modified impregnating agent. (3) Add the modified impregnating agent to anhydrous ethanol and heat and stir until completely dissolved. Then add porous biochar and ultrasonically disperse for 50 min. Then place it in a vacuum drying oven at 60℃ and let it stand for 18 h to prepare the modified porous biochar.

[0009] Preferably, the molar ratio of dimethyl terephthalate, PEG2000 and phosphoric acid is 3:1:0.2.

[0010] Preferably, the addition ratio of the modified impregnating agent, anhydrous ethanol and porous biochar is 0.4~0.8g:100~200mL:1g.

[0011] Preferably, the method for preparing the porous biochar includes the following steps: ① Place corn stalk powder in a corundum boat, then put it into a vacuum tube furnace and purge with nitrogen for 30 minutes. Set the initial temperature to 50℃ and the heating rate to 5℃ / min. After heating to 500℃, calcine at a constant temperature for 2 hours. Then cool down to 50℃ at a cooling rate of 5℃ / min. After naturally cooling to room temperature, take it out to prepare biochar. ② After mixing biochar and potassium hydroxide, place them in a corundum boat and then put them into a vacuum tube furnace. Purge with nitrogen for 30 minutes, set the initial temperature to 50℃, and the heating rate to 5℃ / min. After heating to 700℃, calcine at a constant temperature for 2 hours. Then, cool down to 50℃ at a cooling rate of 5℃ / min. After naturally cooling to room temperature, remove the mixture, add distilled water to dissolve it, and slowly add dilute hydrochloric acid dropwise until neutral while stirring magnetically. After standing overnight, vacuum filter the mixture, rinse it with distilled water, and dry it in a drying oven to obtain porous biochar.

[0012] Preferably, the mass ratio of biochar to potassium hydroxide is 1:3~5.

[0013] The preparation method of the tea tree plug tray seedling substrate as described above includes the following steps: weigh each component according to the weight parts, mix the decomposed pine needles, composite modified porous biochar, vermiculite, perlite and river sand evenly to prepare the tea tree plug tray seedling substrate.

[0014] The beneficial effects of this invention are: This invention utilizes agricultural waste, corn stalks, to prepare porous biochar with high specific surface area and rich pore structure through high-temperature pyrolysis and potassium hydroxide etching. Simultaneously, using dimethyl terephthalate, ethylene glycol, PEG2000, and phosphoric acid as raw materials, a modified impregnating agent containing polyester polyether segments is prepared through transesterification and polycondensation reactions. The porous biochar is then impregnated with this modified impregnating agent to prepare modified porous biochar, thereby introducing hydrophilic polyester polyether segments into the surface and pore structure of the porous biochar. Acrylic acid, acrylamide, and 2-acrylamido-2- A composite modified porous biochar is prepared by combining a ternary copolymer superabsorbent resin obtained by aqueous solution polymerization of methylpropanesulfonic acid with modified porous biochar. The polymer segments of the ternary copolymer superabsorbent resin, after swelling, can entangle with the seedling substrate, forming a colloidal structure and improving the substrate's adsorption and interception capabilities. Furthermore, the introduced hydrophilic polyester polyether segments in the composite of the ternary copolymer superabsorbent resin and modified porous biochar are more compatible with water-soluble monomers such as acrylic acid and acrylamide, forming a stronger composite structure and endowing the seedling substrate with excellent water absorption and retention properties. This invention uses a compound of decomposed pine needles, composite modified porous biochar, vermiculite, perlite, and river sand. The fibrous structure of the decomposed pine needles, along with vermiculite, perlite, and river sand, constructs good aeration and drainage channels. The composite modified porous biochar replaces non-renewable resources such as peat moss, while providing excellent water absorption and retention capabilities, which is beneficial to the growth and development of tea trees. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0016] Example 1: A method for preparing porous biochar includes the following steps: ① Place corn stalk powder in a corundum boat, then put it into a vacuum tube furnace and purge with nitrogen for 30 minutes. Set the initial temperature to 50℃ and the heating rate to 5℃ / min. After heating to 500℃, calcine at a constant temperature for 2 hours. Then cool down to 50℃ at a cooling rate of 5℃ / min. After naturally cooling to room temperature, take it out to prepare biochar. ② Take biochar and potassium hydroxide at a mass ratio of 1:4, place them in a corundum boat, and then put them in a vacuum tube furnace. Purge with nitrogen for 30 minutes, set the initial temperature to 50℃, the heating rate to 5℃ / min, and calcine at a constant temperature for 2 hours after heating to 700℃. Then, cool down to 50℃ at a cooling rate of 5℃ / min, and let it cool naturally to room temperature. Then, add distilled water to dissolve it, and slowly add dilute hydrochloric acid dropwise until neutral while stirring magnetically. After standing overnight, vacuum filter it, rinse it with distilled water, and dry it in a drying oven to obtain porous biochar.

[0017] Example 2: A method for preparing modified porous biochar includes the following steps: (1) Take dimethyl terephthalate and heat it to 150°C until it is completely dissolved. Then add ethylene glycol and anhydrous zinc acetate. Heat it to 180°C under magnetic stirring. Stop the reaction when the generated methanol stops evaporating. Prepare dihydroxyethyl terephthalate. The molar ratio of dimethyl terephthalate to ethylene glycol is 1:1.5. (2) PEG2000, phosphoric acid, triphenyl phosphite and antimony trioxide catalyst were added to diethyl terephthalate, nitrogen protection was turned on, and the mixture was heated to 270°C and vacuumed to carry out polycondensation reaction to prepare a modified impregnating agent. The molar ratio of dimethyl terephthalate, PEG2000 and phosphoric acid was 3:1:0.2, and the amount of antimony trioxide was 230 ppm of the total mass of dimethyl terephthalate. (3) Take 0.7g of modified impregnating agent, add 180mL of anhydrous ethanol, heat and stir until completely dissolved, then add 1g of porous biochar prepared in Example 1, ultrasonically disperse for 50min, then place in a vacuum drying oven at 60℃ for vacuum drying, and let stand for 18h to prepare modified porous biochar.

[0018] Example 3 A method for preparing composite modified porous biochar includes the following steps: Add 4 mL of acrylic acid to 10 mL of potassium hydroxide aqueous solution with a concentration of 0.243 g / mL, stir and mix, then add 5 mL of acrylamide aqueous solution with a concentration of 0.2 g / mL and 5 mL of 2-acrylamido-2-methylpropanesulfonic acid aqueous solution with a concentration of 0.2 g / mL. Mix evenly under magnetic stirring, then heat to 50 °C, add 5 mL of N,N'-methylenebisacrylamide aqueous solution with a concentration of 0.0024 g / mL, mix evenly, then add 1.5 g of the modified porous biochar prepared in Example 2, heat to 60 °C, and slowly add 5 mL of ammonium persulfate aqueous solution with a concentration of 0.016 g / mL. React fully for 3 h. After the reaction is completed, wash, dry and sieve to prepare composite modified porous biochar.

[0019] Example 4 A substrate for tea tree seedling trays, comprising the following components by weight: 22 parts of decomposed pine needles, 11.7 parts of composite modified porous biochar prepared in Example 3, 5.5 parts of vermiculite, 5.5 parts of perlite, and 5.3 parts of river sand.

[0020] The above-mentioned method for preparing the tea tree plug tray seedling substrate includes the following steps: weighing each component according to the weight parts, mixing the decomposed pine needles, composite modified porous biochar, vermiculite, perlite and river sand evenly to prepare the tea tree plug tray seedling substrate.

[0021] Example 5 A substrate for tea tree seedling trays, comprising the following components by weight: 30 parts of decomposed pine needles, 15.5 parts of composite modified porous biochar prepared in Example 3, 10.7 parts of vermiculite, 10.8 parts of perlite, and 10.8 parts of river sand.

[0022] The above-mentioned method for preparing the tea tree plug tray seedling substrate includes the following steps: weighing each component according to the weight parts, mixing the decomposed pine needles, composite modified porous biochar, vermiculite, perlite and river sand evenly to prepare the tea tree plug tray seedling substrate.

[0023] Example 6 A substrate for tea tree seedling trays, comprising the following components by weight: 38 parts of decomposed pine needles, 19.2 parts of composite modified porous biochar prepared in Example 3, 14.8 parts of vermiculite, 14.6 parts of perlite, and 14.6 parts of river sand.

[0024] The above-mentioned method for preparing the tea tree plug tray seedling substrate includes the following steps: weighing each component according to the weight parts, mixing the decomposed pine needles, composite modified porous biochar, vermiculite, perlite and river sand evenly to prepare the tea tree plug tray seedling substrate.

[0025] Comparative Example 1: A method for preparing modified biochar includes the following steps: (1) Take dimethyl terephthalate and heat it to 150°C until it is completely dissolved. Then add ethylene glycol and anhydrous zinc acetate. Heat it to 180°C under magnetic stirring. Stop the reaction when the generated methanol stops evaporating. Prepare dihydroxyethyl terephthalate. The molar ratio of dimethyl terephthalate to ethylene glycol is 1:1.5. (2) PEG2000, phosphoric acid, triphenyl phosphite and antimony trioxide catalyst were added to diethyl terephthalate, nitrogen protection was turned on, and the mixture was heated to 270°C and vacuumed to carry out polycondensation reaction to prepare a modified impregnating agent. The molar ratio of dimethyl terephthalate, PEG2000 and phosphoric acid was 3:1:0.2, and the amount of antimony trioxide was 230 ppm of the total mass of dimethyl terephthalate. (3) Take 0.7g of modified impregnating agent, add 180mL of anhydrous ethanol, heat and stir until completely dissolved, then add 1g of biochar prepared in Example 1 and ultrasonically disperse for 50min, then place in a vacuum drying oven at 60℃ and vacuum dry, let stand for 18h to prepare modified biochar.

[0026] A method for preparing composite modified biochar includes the following steps: Add 4 mL of acrylic acid to 10 mL of potassium hydroxide aqueous solution with a concentration of 0.243 g / mL, stir and mix, then add 5 mL of acrylamide aqueous solution with a concentration of 0.2 g / mL and 5 mL of 2-acrylamido-2-methylpropanesulfonic acid aqueous solution with a concentration of 0.2 g / mL. Mix evenly under magnetic stirring, then heat to 50 °C, add 5 mL of N,N'-methylenebisacrylamide aqueous solution with a concentration of 0.0024 g / mL, mix evenly, then add 1.5 g of the modified biochar prepared above, heat to 60 °C, and slowly add 5 mL of ammonium persulfate aqueous solution with a concentration of 0.016 g / mL. React for 3 h. After the reaction is completed, wash, dry and sieve to prepare composite modified biochar.

[0027] Comparative Example 2: A method for preparing a composite porous biochar includes the following steps: Add 4 mL of acrylic acid to 10 mL of potassium hydroxide aqueous solution with a concentration of 0.243 g / mL, stir and mix, then add 5 mL of acrylamide aqueous solution with a concentration of 0.2 g / mL and 5 mL of 2-acrylamido-2-methylpropanesulfonic acid aqueous solution with a concentration of 0.2 g / mL. Mix evenly under magnetic stirring, then heat to 50 °C, add 5 mL of N,N'-methylenebisacrylamide aqueous solution with a concentration of 0.0024 g / mL, mix evenly, then add 1.5 g of porous biochar prepared in Example 1, heat to 60 °C, and slowly add 5 mL of ammonium persulfate aqueous solution with a concentration of 0.016 g / mL. React fully for 3 h. After the reaction is completed, wash, dry and sieve to prepare composite porous biochar.

[0028] Comparative Example 3: A substrate for raising tea seedlings in plug trays, comprising the following components by weight: 38 parts of decomposed pine needles, 19.2 parts of composite modified biochar prepared in Comparative Example 1, 14.8 parts of vermiculite, 14.6 parts of perlite, and 14.6 parts of river sand.

[0029] The preparation method of the above-mentioned tea tree plug tray seedling substrate includes the following steps: weigh each component according to the weight parts, mix the decomposed pine needles, modified porous biochar, vermiculite, perlite and river sand evenly to prepare the tea tree plug tray seedling substrate.

[0030] Comparative Example 4: A substrate for raising tea tree seedlings in plug trays, comprising the following components by weight: 38 parts of decomposed pine needles, 19.2 parts of composite porous biochar prepared in Comparative Example 2, 14.8 parts of vermiculite, 14.6 parts of perlite, and 14.6 parts of river sand.

[0031] The preparation method of the above-mentioned tea tree plug tray seedling substrate includes the following steps: weigh each component according to the weight parts, mix the decomposed pine needles, modified porous biochar, vermiculite, perlite and river sand evenly to prepare the tea tree plug tray seedling substrate.

[0032] Comparative Example 5: A substrate for raising tea seedlings in plug trays, comprising the following components by weight: 38 parts of decomposed pine needles, 19.2 parts of modified porous biochar prepared in Example 2, 14.8 parts of vermiculite, 14.6 parts of perlite, and 14.6 parts of river sand.

[0033] The preparation method of the above-mentioned tea tree plug tray seedling substrate includes the following steps: weigh each component according to the weight parts, mix the decomposed pine needles, modified porous biochar, vermiculite, perlite and river sand evenly to prepare the tea tree plug tray seedling substrate.

[0034] Performance testing The performance of the tea tree plug seedling substrates prepared in Examples 4-6 and Comparative Examples 3-5 was tested. A known volume and mass of seedling substrate was immersed in deionized water until fully absorbed, and then drained by gravity. This process was repeated three times to ensure the substrate was saturated with water. After 30 minutes of gravity drainage, the volume and mass were measured again. The substrate was then placed in an oven at 105℃ and dried for 7 days. The mass was measured again, and the maximum water holding capacity, total porosity, and aeration porosity were calculated. The tea variety used was Echa No. 1. The seedling trays were 545mm × 280mm, 50-cell rectangular black seedling trays with a height of 5cm. Black shade nets were used, with a thickness of 2 needles. After 90 days, the rooting rate and root length were measured. The data results are shown in Table 1.

[0035] Table 1 Test results of sample performance ; As can be seen from the data results in Table 1, the seedling substrates prepared in Examples 4-6 of this invention are more suitable for the growth of tea trees than those in Comparative Examples 1-2. In Comparative Example 3, when the composite modified porous biochar was replaced with an equal amount of composite modified biochar, the measured total porosity, aeration porosity, water holding capacity, rooting rate, and root length were lower than those in Examples 4-6. In Comparative Example 4, when the composite modified porous biochar was replaced with an equal amount of composite porous biochar, and in Comparative Example 5, when the composite modified porous biochar was replaced with an equal amount of modified porous biochar, the measured water holding capacity, rooting rate, and root length were lower than those in Examples 4-6. This indicates that the addition of composite modified porous biochar is beneficial to improving the seedling performance of the substrate.

[0036] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0037] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A substrate for tea tree seedling tray cultivation, characterized in that, It includes the following components by weight: 20-40 parts of decomposed pine needles, 10-20 parts of composite modified porous biochar, 5-15 parts of vermiculite, 5-15 parts of perlite, and 5-15 parts of river sand; The composite modified porous biochar is made by combining a ternary copolymer superabsorbent resin obtained by aqueous solution polymerization of acrylic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid with modified porous biochar. The modified porous biochar is prepared by pyrolysis of corn stalks at high temperature and etching with potassium hydroxide. Then, the porous biochar is impregnated with a modified impregnating agent prepared by transesterification and polycondensation of dimethyl terephthalate, ethylene glycol, PEG2000 and phosphoric acid.

2. The tea tree seedling tray substrate according to claim 1, characterized in that, The preparation method of the composite modified porous biochar includes the following steps: Acrylic acid was added to an aqueous solution of potassium hydroxide and stirred. Then, an aqueous solution of acrylamide and an aqueous solution of 2-acrylamido-2-methylpropanesulfonic acid were added and mixed evenly under magnetic stirring. The mixture was then heated to 50°C and an aqueous solution of N,N'-methylenebisacrylamide was added. After mixing evenly, modified porous biochar was added and the temperature was raised to 60°C. An aqueous solution of ammonium persulfate was slowly added dropwise and the mixture was allowed to react for 3 hours. After the reaction was completed, the biochar was washed, dried, and sieved to obtain the composite modified porous biochar.

3. The tea tree seedling tray substrate according to claim 2, characterized in that, The concentration of the potassium hydroxide aqueous solution is 0.243 g / mL; the concentration of the acrylamide aqueous solution is 0.2 g / mL; the concentration of the 2-acrylamido-2-methylpropanesulfonic acid aqueous solution is 0.2 g / mL; the concentration of the N,N'-methylenebisacrylamide aqueous solution is 0.0024 g / mL; and the concentration of the ammonium persulfate aqueous solution is 0.016 g / mL.

4. The tea tree seedling tray substrate according to claim 2, characterized in that, The addition ratio of the potassium hydroxide aqueous solution, acrylic acid, acrylamide aqueous solution, 2-acrylamido-2-methylpropanesulfonic acid aqueous solution, N,N'-methylenebisacrylamide aqueous solution, modified porous biochar and ammonium persulfate aqueous solution is 2mL:0.8mL:1mL:1mL:1mL:1~2g:1mL.

5. The tea tree seedling tray substrate according to claim 2, characterized in that, The method for preparing the modified porous biochar includes the following steps: (1) Take dimethyl terephthalate and heat it to 150°C until it is completely dissolved. Then add ethylene glycol and anhydrous zinc acetate. Heat it to 180°C under magnetic stirring. Stop the reaction when the generated methanol stops evaporating. Prepare dihydroxyethyl terephthalate. (2) PEG2000, phosphoric acid, triphenyl phosphite and antimony trioxide catalyst were added to dihydroxyethyl terephthalate, nitrogen protection was turned on, and the mixture was heated to 260~280℃ and vacuumed to carry out polycondensation reaction to prepare the modified impregnating agent. (3) Add the modified impregnating agent to anhydrous ethanol and heat and stir until completely dissolved. Then add porous biochar and ultrasonically disperse for 50 min. Then place it in a vacuum drying oven at 60℃ and let it stand for 18 h to prepare the modified porous biochar.

6. The tea tree seedling tray substrate according to claim 5, characterized in that, The molar ratio of dimethyl terephthalate, PEG2000 and phosphoric acid is 3:1:0.

2.

7. The tea tree seedling tray substrate according to claim 5, characterized in that, The ratio of the modified impregnating agent, anhydrous ethanol and porous biochar is 0.4~0.8g:100~200mL:1g.

8. The tea tree seedling tray substrate according to claim 5, characterized in that, The method for preparing the porous biochar includes the following steps: ① Place corn stalk powder in a corundum boat, then put it into a vacuum tube furnace and purge with nitrogen for 30 minutes. Set the initial temperature to 50℃ and the heating rate to 5℃ / min. After heating to 500℃, calcine at a constant temperature for 2 hours. Then cool down to 50℃ at a cooling rate of 5℃ / min. After naturally cooling to room temperature, take it out to prepare biochar. ② After mixing biochar and potassium hydroxide, place them in a corundum boat and then put them into a vacuum tube furnace. Purge with nitrogen for 30 minutes, set the initial temperature to 50℃, and the heating rate to 5℃ / min. After heating to 700℃, calcine at a constant temperature for 2 hours. Then, cool down to 50℃ at a cooling rate of 5℃ / min. After naturally cooling to room temperature, remove the mixture, add distilled water to dissolve it, and slowly add dilute hydrochloric acid dropwise until neutral while stirring magnetically. After standing overnight, vacuum filter the mixture, rinse it with distilled water, and dry it in a drying oven to obtain porous biochar.

9. The tea tree seedling tray substrate according to claim 8, characterized in that, The mass ratio of biochar to potassium hydroxide is 1:3~5.

10. A method for preparing a tea tree seedling tray substrate according to any one of claims 1 to 9, characterized in that, Includes the following steps: Weigh each component according to the weight proportions, and mix the decomposed pine needles, composite modified porous biochar, vermiculite, perlite and river sand evenly to prepare the tea tree plug seedling substrate.