Stevia rebaudiana agricultural waste compound substrate as well as preparation method and application thereof

Abstract

The invention discloses an agricultural waste compound substrate for cultivating stevia rebaudiana, which is prepared by mixing rice husk and rice chaff according to a volume ratio of (4-6): 1, adding a urea solution and a microbial agent, uniformly mixing, and carrying out aerobic fermentation. According to the method, the rice husks and the rice chaff which are discarded in agriculture are mixed and fermented, so that harmful substances in the rice husks and the rice chaff are eliminated, and the nutrient concentration, the water content, the water and air permeability, the EC value and other physical and chemical properties of the obtained substrate reach the most suitable stevia rebaudiana growth range by adjusting the proportion and fermentation conditions of the rice husks and the rice chaff. Besides, the substrate can reduce application of nutrient solution or chemical fertilizer and accumulation of salt in the substrate, fertilizer damage to the substrate is avoided, the quality and yield of stevia rebaudiana are improved, the fermentation cost of the substrate is far lower than that of an existing substrate, and the substrate has good economic benefits and application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of planting substrates, and more specifically, relates to a stevia agricultural waste composite substrate and a preparation method and application thereof. Background Art

[0002] Stevia is native to the subtropical region of South America and belongs to the herbaceous plant of the Asteraceae family. The steviol glycosides in stevia leaves are characterized by high sweetness and low calories. The sweetness is 150 to 300 times that of sucrose, and the calories contained are only 0.3% of sucrose. The active substances in stevia leaves do not participate in metabolism, have no side effects, and are highly safe. As a natural, safe, and low-calorie sweetener, stevia has huge market demand and broad market prospects. Stevia leaf extract has pharmacological activities such as antioxidant, antiviral, anti-tumor, and immune regulation. Therefore, stevia is also widely used in the pharmaceutical, health care and other industries. As the world market demand for stevia products becomes increasingly strong, it is expected that the export volume of domestic stevia products will grow rapidly in the next few years, and the stevia planting area will continue to expand. Stevia has also become one of the advantageous industries to promote agricultural efficiency and increase farmers' income.

[0003] In recent years, due to excessive application of nitrogen fertilizer in agricultural production, the ratio of nitrogen, phosphorus and potassium in the soil is unbalanced, which hinders the growth of stevia. Although artificial application of potassium fertilizer and nitrogen fertilizer can meet the nutrient requirements of plants during growth, it will increase production costs and pollute the soil. At present, there are few studies on soilless cultivation of stevia. The commonly used soilless cultivation of stevia is a substrate of slag and sand. The substrate has good air permeability, but lacks the nutrients for the growth of stevia. At present, there is an urgent need for an environmentally friendly, low-cost and efficient stevia cultivation substrate that can not only obtain high-yield and high-quality stevia, but also reduce soil pollution and stevia production costs.

[0004] In addition, my country is a major agricultural producer, and a large amount of agricultural waste will inevitably be generated in the process of agricultural production. The resource utilization of agricultural waste has become an important part of the current sustainable development of agriculture and the development of a green circular economy. It is an important measure to promote the development of the agricultural economy and build a conservation-oriented society. Its harmless and resource-based utilization has become an important topic of current research. The matrix utilization of agricultural waste refers to the process of using agricultural waste that has been treated with harmless and stabilized technologies for crop cultivation through an appropriate formulation process. The matrix utilization of agricultural waste can reduce the use of chemical fertilizers, promote the growth of crops, and alleviate the tension of land resources, and has great development prospects. However, the harmful substances, nutrients, physical and chemical properties of agricultural waste are undesirable. For stevia, which has high requirements for cultivation substrates, how to use agricultural waste to produce stevia-specific cultivation substrates is a difficult problem. Summary of the invention

[0005] The present invention aims to overcome the defects and shortcomings of the existing stevia matrix and provide an agricultural waste composite matrix for cultivating stevia and a preparation method and application thereof.

[0006] The first object of the present invention is to provide an agricultural waste composite matrix for cultivating stevia.

[0007] The second object of the present invention is to provide the use of the above-mentioned composite matrix as or in the preparation of stevia cultivation matrix or stevia fertilizer.

[0008] The third object of the present invention is to provide a method for cultivating stevia.

[0009] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0010] The invention provides an agricultural waste composite matrix for cultivating stevia. The agricultural waste composite matrix is ​​prepared by mixing rice husk and rice bran in a volume ratio of (4-6):1, adding urea and microbial inoculants, mixing and aerobic fermentation.

[0011] Specifically, based on the total weight ratio of rice husk and rice bran, the usage amount of the microbial agent is 0.2-0.6wt%, and the usage amount of urea is 0.4-0.8wt% of a urea solution with a concentration of 6-10%.

[0012] Specifically, the rice husk needs to be soaked in water for 22 to 26 hours and then filtered dry.

[0013] Specifically, the water content of the rice bran is 55-60%.

[0014] Specifically, the aerobic fermentation process needs to be stirred 3 to 5 times a day, and the completion condition of the aerobic fermentation is that the temperature inside the substrate differs from the room temperature by ≤5°C.

[0015] As an optional embodiment, the specific preparation method of the agricultural waste composite matrix for cultivating stevia is as follows:

[0016] S1. Soaking: Soak the rice husks in water for 20 to 28 hours, filter the absorbed rice husks with a filter until the rice husks no longer drip water, and set aside;

[0017] S2. The rice husk treated in step S1 is mixed with rice bran in a volume ratio of (4-6):1, and then 0.6wt% urea solution (concentration of 8%) based on the total weight ratio of the rice husk and the rice bran and 0.4wt% microbial agent based on the total weight ratio of the rice husk and the rice bran are added, and the mixture is stirred evenly, and aerobic fermentation is carried out in a fermentation barrel, and the substrate is stirred and ventilated 3-5 times a day until the temperature in the barrel differs from the room temperature by ≤5°C, and the substrate fermentation is completed;

[0018] S3. After the substrate fermentation is completed, the composite substrate needs to be spread out in the sun to remove the ammonia smell. After the ammonia smell is removed, it is bagged for later use.

[0019] The present invention provides the use of the composite matrix as or in the preparation of a stevia cultivation matrix or a stevia fertilizer.

[0020] The present invention also provides a stevia cultivation method, which comprises the following steps: subjecting stevia seedlings to rooting treatment, cultivating the seedlings on the composite substrate, and applying a composite nutrient solution after the seedling acclimatization period.

[0021] Specifically, the rooting treatment is to immerse the stevia seedlings in a rooting solution for 8 to 12 seconds, wherein the rooting solution is a rooting powder solution; the composite nutrient solution contains one or more of ammonium nitrate, potassium nitrate, calcium nitrate, potassium dihydrogen phosphate, potassium sulfate, magnesium sulfate, ferrous sulfate heptahydrate, disodium ethylenediaminetetraacetic acid, boric acid, manganese sulfate, zinc sulfate, copper sulfate, and ammonium paramolybdate.

[0022] As an optional implementation, the composite nutrient solution is a mixture of nutrient solution A, nutrient solution B and nutrient solution C in a ratio of 1:1:1;

[0023] ① Preparation method of nutrient solution A: add 200g ammonium nitrate, 505g potassium nitrate and 1180g calcium nitrate to 10L water and mix;

[0024] ② Preparation of nutrient solution B: Add 250g potassium dihydrogen phosphate, 435g potassium sulfate and 615g magnesium sulfate to 10L water and mix;

[0025] ③ Preparation method of nutrient solution C: add 278g of ferrous sulfate heptahydrate, 372g of disodium ethylenediaminetetraacetate, 28.6g of boric acid, 21.3g of manganese sulfate, 2.2g of zinc sulfate, 0.8g of copper sulfate and 0.2g of ammonium paramolybdate into 10L of water and mix.

[0026] ④ Take 20 mL each of the prepared nutrient solution A, nutrient solution B and nutrient solution C and add 10 L of water to mix them into a compound nutrient solution.

[0027] The present invention has the following beneficial effects:

[0028] The present invention uses rice husks and rice brans discarded in agriculture for fermentation, so that harmful substances in the rice husks and rice brans are eliminated, and the physical and chemical properties of the obtained matrix such as nutrient concentration, moisture content, water permeability and EC value are adjusted to the range most suitable for the growth of stevia by adjusting the ratio of rice husks and rice brans and fermentation conditions. In addition, the organic matter content of the matrix of the present invention is relatively high, and the ratio of the total nitrogen, total potassium and total phosphorus content contained is more in line with the nutritional ratio of stevia to absorb nitrogen, phosphorus and potassium, which can supply the nutrition required by stevia seedlings, reduce the application of nutrient solution or chemical fertilizers, and reduce the accumulation of salt in the matrix, which not only avoids the fertilizer damage of the matrix, but also improves the quality and yield of stevia, and the fermentation cost of the matrix of the present invention is much lower than that of the existing matrix, and has good economic benefits and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The growth conditions of stevia cultivated in different treated substrates.

[0030] Figure 2 This is the growth condition of Stevia treated with CK in Example 3.

[0031] Figure 3 This is the growth condition of Stevia treated with T1 in Example 3.

[0032] Figure 4 This is the growth condition of Stevia treated with T2 in Example 3. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0034] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0035] The commercial substrates in the following examples are commercially available, and their main components are nutrient soil, coconut husk and perlite.

[0036] The microbial agents in the following examples were purchased from Henan Wobao Biotechnology Co., Ltd.

[0037] The cultivated stevia variety in the following examples is Puxing No. 13.

[0038] The rice bran in the following examples was sourced from Yihe Town, Heyuan City, Guangdong Province.

[0039] The rice husks in the following examples were sourced from Dapu County, Meizhou City, Guangdong Province.

[0040] The perlite used in the following examples is commercially available.

[0041] The rooting powder described in the following examples was purchased from Hebei Dewoduo Fertilizer Co., Ltd.

[0042] In the following examples, the matrix bulk density was determined using the ring knife method, and the matrix acidity and conductivity were determined using a pH meter and a conductivity meter. The alkaline nitrogen, available phosphorus and available potassium content of the matrix were determined using the method of Soil Agrochemical Analysis (China Agriculture Press, 2000); the total nitrogen, total phosphorus, total potassium and organic matter content in the matrix were determined by referring to the method of "Organic Fertilizer" in the Agricultural Industry Standard of the People's Republic of China NY 525-2021; the total porosity, aeration porosity, water holding porosity and moisture content of the matrix were determined with reference to the agricultural standard NY / T2118-2012.

[0043] Example 1 Rice bran fermentation substrate

[0044] 1. Pure rice bran fermentation matrix

[0045] In order to explore whether the rice bran fermentation matrix is ​​suitable for use as a stevia cultivation matrix, a pure rice bran fermentation matrix was prepared. The preparation method of the pure rice bran fermentation matrix is: take rice bran (water content reaches 55% to 60%), add 0.6wt% urea solution (urea solution concentration is 8%) and 0.6wt% microbial agent to the rice bran weight, stir evenly, and then ferment and decompose in a fermentation machine, wait for the pile temperature to be consistent with the ambient temperature (temperature difference ≤5°C), the surface of the rice bran turns from yellow to gray and black, that is, the fermentation is completed, and the fermentation time is about 45 days.

[0046] The properties of the rice bran substrate before and after fermentation were measured, and the results are shown in Tables 1 and 2.

[0047] As shown in Table 1, after fermentation, the bulk density of rice bran decreased slightly, about 0.39 g / cm 3 . Compared with before fermentation, the total porosity, ventilation porosity, and water holding porosity of rice bran after fermentation were slightly reduced, with the total porosity reduced by 5.86%, the ventilation porosity reduced by 5.59%, the water holding porosity reduced by 2.25%, and the ratio of large and small pores decreased by 0.10. After fermentation, the pH of rice bran increased significantly compared with before fermentation, at around 7.53, and the EC of rice bran increased to 3.85ms / cm.

[0048] Table 1 Changes in physical properties of rice bran before and after fermentation

[0049]

[0050] Note: Data in the same column are mean ± standard error.

[0051] As shown in Table 2, compared with before fermentation, the organic matter content of rice bran after fermentation decreased by 4.41% to 62.88%. The content of total nutrients and available nutrients increased, with total nitrogen content increasing by 0.55g / kg, total phosphorus increasing by 2.47g / kg, and total potassium increasing by 4.32g / kg. Alkaline nitrogen, available phosphorus, and available potassium increased to 1373.17mg / kg, 3556.26mg / kg, and 9389.09mg / kg, respectively.

[0052] Table 2 Changes in chemical properties of rice bran before and after fermentation

[0053]

[0054] Note: Data in the same column are mean ± standard error.

[0055] The test of stevia cutting planting showed that the survival rate of stevia was very low, no more than 35%. Therefore, pure rice bran fermentation matrix is ​​not suitable for stevia cultivation.

[0056] 2. Pure rice bran fermentation matrix composite matrix

[0057] Seven treatment groups were set up, and the fermented pure rice bran matrix was mixed with river sand and perlite in different proportions to form the seedling medium:

[0058] Treatment T1 consisted of pure rice bran substrate and perlite in a volume ratio of 10:0;

[0059] Treatment T2 consisted of pure rice bran substrate and perlite in a volume ratio of 8:2;

[0060] Treatment T3 consisted of pure rice bran substrate, river sand, and perlite in a volume ratio of 7:1:2;

[0061] Treatment T4 consisted of pure rice bran substrate, river sand, and perlite in a volume ratio of 6:2:2;

[0062] Treatment T5 consisted of pure rice bran substrate, river sand, and perlite in a volume ratio of 5:3:2;

[0063] Treatment T6 consisted of pure rice bran substrate, river sand, and perlite in a volume ratio of 4:4:2;

[0064] Treatment T7 consisted of pure rice bran substrate, river sand, and perlite in a volume ratio of 3:5:2;

[0065] The control group CK used commercial matrix.

[0066] The seedling substrates of different treatments and the control group were sampled and tested for their physical and chemical properties. The test results of the physical and chemical properties of the seedling substrates of different treatments are shown in Table 3 and Table 4. From the results of Table 3 and Table 4, it can be seen that the physical and chemical properties of the seedling substrates formed by the mixture of different treatments are significantly different. Figure 1 As shown, from Figure 1 It can be seen that the leaves of stevia in the seedling medium treated with T1 and T2 are seriously withered, followed by those in the treatments of T3, T4 and T5, and the stevia cultivated in the seedling medium treated with T6 and T7 grows better. This is because stevia is suitable for planting in fertile sandy loam and loam with a pH value of 5.5-7.5, and the EC value and bulk density of the seedling medium treated with T6 and T7 are closest to the EC value of sandy loam and loam, so the stevia planted in the treatments of T6 and T7 grow well. The EC value of the seedling medium of the other treatments is too high, causing the "seedling burn" phenomenon, and the pH of the medium is too alkaline, so the survival rate of the seedlings in the other groups except the T6 and T7 treatments is low (the survival rate of T1 to T5 is all below 70%, the survival rate of T6 to T7 is higher than 70%, and the survival rate of T7 is especially about 90%). The application ranges of N, P2O5 and K2O fertilizers suitable for stevia growth were 365.26-701.11 mg / kg, 160.20-176.96 mg / kg and 528.35-793.91 mg / kg respectively. The alkaline nitrogen content of the seedling medium treated with T1, T2, T3 and T4 was too high, which hindered the growth of stevia.

[0067] In summary, the growth of stevia in different substrates showed that stevia grew best when the rice bran content was 30%-40% (T6-T7). However, stevia in T1-T7 (including T7 group) showed different degrees of leaf chlorosis and growth retardation.

[0068] Table 3 Physical properties of seedling medium under different treatments

[0069]

[0070]

[0071] Note: Different lowercase letters in the table indicate significant differences (P<0.05), the same letters or no letters indicate no significant differences (P>0.05), and the meanings of letters in subsequent tables are the same as in this table.

[0072] Table 4 Chemical properties of seedling medium under different treatments

[0073]

[0074] Example 2 Agricultural waste composite matrix

[0075] According to the experimental results of Example 1, in order to further explore the agricultural waste composite matrix suitable for cultivating stevia, this example uses rice husk as the matrix raw material to explore the matrix with rice husk and rice bran as materials suitable for cultivating stevia.

[0076] 1. Explore the ratio of rice husk to rice bran

[0077] Three treatments were set up, wherein rice husks and rice bran were mixed in different proportions to form a matrix, wherein the rice husks were soaked in water for 24 hours and then filtered until no water droplets were left, and each treatment was repeated 5 times;

[0078] Treatment A had a volume ratio of rice husk to rice bran of 4:1;

[0079] Treatment B was a volume ratio of rice husk to rice bran of 3:1;

[0080] Treatment C had a volume ratio of rice husk to rice bran of 7:3.

[0081] By determining whether the moisture content of the substrates of treatments A, B, and C meets the optimum moisture content for stevia growth (55%-60%), the three substrate ratios were screened. The determination of the substrate moisture content of three different rice husk and rice bran ratios is shown in Table 5. As shown in Table 5, when the volume ratio of rice husk and rice bran in treatment A is 4:1, the substrate moisture content reaches the most suitable condition for stevia growth, so the volume ratio of rice husk and rice bran in treatment A is 4:1 for subsequent stevia cultivation substrate research.

[0082] Table 5 Water content of different matrix ratios

[0083]

[0084] 2. Preparation of agricultural waste composite matrix

[0085] The agricultural waste composite matrix for cultivating stevia in this embodiment is prepared by mixing rice husks and rice bran in a volume ratio of 4:1, adding 0.6wt% urea solution based on the total weight ratio of rice husks and rice bran and 0.4wt% microbial agent based on the total weight ratio of rice husks and rice bran, mixing and aerobic fermentation. The specific preparation method steps are as follows:

[0086] S1. Soaking: Soak the rice husks in water for 24 hours, filter the absorbed rice husks with a filter until the rice husks no longer drip water, and set aside;

[0087] S2. The rice husk treated in step S1 is mixed with rice bran in a volume ratio of 4:1, and then 0.6wt% urea solution (concentration of 8%) and 0.4wt% microbial agent are added, and the mixture is stirred evenly, and aerobic fermentation is carried out in a fermentation barrel, and the substrate is stirred and ventilated three times a day until the temperature in the barrel differs from the room temperature by ≤5°C, and the substrate fermentation is completed;

[0088] S3. After the substrate fermentation is completed, the composite substrate needs to be spread out in the sun to remove the ammonia smell. After the ammonia smell is removed, it is bagged for later use.

[0089] A pure rice husk fermentation matrix control group is set up. The preparation method of the pure rice husk fermentation matrix is ​​different from the preparation method of the agricultural waste composite matrix for cultivating stevia in that: in step S2, the rice husk is mixed with the urea solution and the microbial agent without adding rice bran, and the other conditions are the same as those in the step.

[0090] The physical and chemical properties of the agricultural waste composite matrix used for cultivating stevia in this embodiment are shown in Table 6. It can be seen from Table 6 that the composite matrix after fermentation reduces the total nitrogen content, avoiding excessive nitrogen from inhibiting the absorption of potassium and phosphorus by stevia, and the total porosity, ventilation porosity, and water holding porosity of the composite matrix after fermentation reach a proportion suitable for the growth of stevia. Compared with the commercial matrix, the composite matrix of this embodiment has an increased organic matter content and three types of porosity that are more suitable, which has certain advantages in stevia cultivation. Compared with the fermented pure rice husk matrix, the composite matrix of this embodiment after fermentation has a higher nitrogen, phosphorus, and potassium content, and a porosity that is more suitable for the growth of stevia, which can provide stevia nutrition and a more suitable ventilation and water permeability environment.

[0091] Table 6 Physicochemical properties of agricultural waste composite matrix used for stevia cultivation

[0092]

[0093] Example 3 Stevia cultivation method based on agricultural waste composite matrix

[0094] (1) Time and Place

[0095] The cutting experiment was carried out in the greenhouse of the College of Resources and Environment of South China Agricultural University from February to April 2024.

[0096] (2) Test materials

[0097] The test variety was Puxing No. 1, and stevia stem segments with uniform growth and moderate maturity were selected for cuttings.

[0098] (3) Test methods

[0099] The matrix raw materials were harmlessly treated (sterilized by sun exposure), and the cutting matrices with different treatments were prepared according to Table 7, wherein the cutting matrices treated with T1 and T2 needed to be added with 0.6wt% urea solution and 0.4wt% microbial agent by total weight ratio for aerobic fermentation. The specific operation was referred to the method for preparing the composite matrix of agricultural waste in Example 2.

[0100] A potted cutting cultivation experiment was carried out using cutting media with different treatments. 5L of cutting media was added to each pot, and 8 stevia stem segments were cut in each pot. Each treatment was repeated 6 times and arranged in random blocks. The survival rate and bud growth rate of stevia with different treatments were determined on the 30th day of cutting cultivation.

[0101] Table 7 Volume ratio of each component in different cutting matrix treatments

[0102]

[0103] The cultivation method of stevia in this embodiment is: after the stevia seedlings are subjected to rooting treatment, they are cultivated on the composite substrate prepared in this embodiment, and the composite nutrient solution is applied after the seedling stage.

[0104] The rooting treatment is to immerse the stevia seedlings in the rooting solution for 10 seconds.

[0105] The rooting solution is prepared by mixing rooting powder and water at a ratio of 4g:1L.

[0106] The composite nutrient solution is prepared by mixing nutrient solution A, nutrient solution B and nutrient solution C in a ratio of 1:1:1;

[0107] ① Preparation method of nutrient solution A: add 200g ammonium nitrate, 505g potassium nitrate and 1180g calcium nitrate to 10L water and mix;

[0108] ② Preparation of nutrient solution B: Add 250g potassium dihydrogen phosphate, 435g potassium sulfate and 615g magnesium sulfate to 10L water and mix;

[0109] ③ Preparation method of nutrient solution C: add 278g of ferrous sulfate heptahydrate, 372g of disodium ethylenediaminetetraacetate, 28.6g of boric acid, 21.3g of manganese sulfate, 2.2g of zinc sulfate, 0.8g of copper sulfate and 0.2g of ammonium paramolybdate into 10L of water and mix.

[0110] ④ Take 20 mL each of the prepared nutrient solution A, nutrient solution B and nutrient solution C and add 10 L of water to mix them into a compound nutrient solution.

[0111] (4) Test results

[0112] The growth conditions of Stevia treated with CK, T1 and T2 are shown in Figure 2. Figure 2 , Figure 3 and Figure 4 The test results are shown in Table 8. The results show that the survival rate and budding rate of stevia in T1 treatment are significantly higher than those in CK and T2 treatments. The survival rate of T1 treatment is 72.92%, and the budding rate is 70.83%, indicating that the substrate in T1 treatment is more suitable as a stevia cutting substrate than the commercial substrate.

[0113] Table 8 Survival rate and budding rate of Stevia rebaudiana under different treatments

[0114]

[0115] Note: The data in the table are the mean ± standard error of 6 replicates

[0116] Moreover, in different repeated tests of the T1 treatment group, the survival rate of stevia can be as high as over 95%, and the sprouting rate can reach over 80%; the survival rate and sprouting rate of all treatments are over 65%.

[0117] Compared with other treatments, the stevia leaves treated with T1 had no obvious leaf chlorosis and growth stunting, and the content of steviol glycosides in stevia leaves was increased.

[0118] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An agricultural waste composite matrix for cultivating stevia, characterized in that: The agricultural waste composite matrix is ​​prepared by mixing rice husk and rice bran in a volume ratio of (4-6):1, and then adding urea and microbial agents, mixing and aerobic fermentation.

2. The composite matrix according to claim 1, characterized in that The usage amount of the microbial agent is 0.2-0.6wt% based on the total weight ratio of rice husk and rice bran.

3. The composite matrix according to claim 1, characterized in that Calculated by the total weight ratio of rice husk and rice bran, the standard usage of urea is 0.4-0.8wt% of urea solution with a concentration of 6-10%.

4. The composite matrix according to claim 1, characterized in that: The rice husk needs to be soaked in water for 22 to 26 hours and then filtered dry.

5. The composite matrix according to claim 1, characterized in that: The water content of the rice bran is 55-60%.

6. The composite matrix according to claim 1, characterized in that During the aerobic fermentation process, the mixture needs to be stirred 3 to 5 times a day.

7. The composite matrix according to claim 1, characterized in that The aerobic fermentation is completed under the condition that the temperature inside the substrate differs from the room temperature by ≤5°C.

8. Use of the composite matrix according to any one of claims 1 to 7 as or in the preparation of a stevia cultivation matrix or a stevia fertilizer.

9. A method for cultivating stevia, characterized in that: After the stevia seedlings are subjected to rooting treatment, they are cultivated on the composite substrate according to any one of claims 1 to 7, and a composite nutrient solution is applied after the seedling acclimatization period.

10. The method according to claim 9, characterized in that: The rooting treatment is to immerse the stevia seedlings in a rooting solution for 8 to 12 seconds, wherein the rooting solution is a rooting powder solution; the composite nutrient solution contains one or more of ammonium nitrate, potassium nitrate, calcium nitrate, potassium dihydrogen phosphate, potassium sulfate, magnesium sulfate, ferrous sulfate heptahydrate, disodium ethylenediaminetetraacetic acid, boric acid, manganese sulfate, zinc sulfate, copper sulfate, and ammonium paramolybdate.

Images