The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.
 The pakchoi cultivation substrate using agricultural waste as the main material in this specific embodiment contains the following components in volume ratio: 4 parts of cotton straw, 2 parts of mushroom residue, 2 parts of grass charcoal, and 2 parts of vermiculite.
 In the method for preparing the pakchoi cultivation substrate using agricultural waste as the main material, the operation steps are as follows:
 1. Preparation of fermentation products of cotton straw:
 1.1. After drying the cotton straw, use a pulverizer to crush it to about 5 cm;
 1.2. Using urea to adjust the material C/N is 25:1, and the moisture content is 65%;
 1.3. Add cellulolytic bacteria (medium temperature + high temperature type), cellulolytic fungi (medium temperature type), and cellulolytic bacteria (medium temperature type, producing cellulolytic enzymes) purchased from the School of Resources and Environment of Nanjing Agricultural University ), starch-degrading spore bacteria (producing starch hydrolase) are compounded into a composite fermentation inoculum, and mixed evenly to make a bottom width of 2.5m, a top width of 1.7m, a height of 1.0m, a bottom length of 3.0m, and a top length 2.2m stack-shaped stack, covered with shed film for heat preservation and moisture retention;
 1.4. Turn the pile once every five days, and the pile will be turned into the original shape until the temperature of the cotton stalk pile is close to the outside air temperature, and the fermentation is completed when the moisture content is stable at 20%;
 2. Preparation of mushroom residue fermentation products:
 2.1. Take the oyster mushroom bag culture residue and crush it to about 2-3cm;
 2.2. Add 0.1% of the weight of mushroom residue to the special fermentation fungus, with a moisture content of 70%, and build a pile after mixing;
 2.3. Turn the pile once every four days. After turning the pile, the pile will be made into its original shape. When the temperature of the pile body is close to the ambient temperature, the temperature will no longer rise and the mushroom residue will turn brown and the texture will be soft and loose. pH6.8-7.5, EC≤3ms Fermentation is complete;
 3. Prepare pure finished peat for substrate and finished vermiculite for substrate;
 4. Mix the above-mentioned cotton straw fermentation product, mushroom residue fermentation product, peat raw material and finished vermiculite according to a volume ratio of 2:1:1:1.
 The beneficial effects of this specific implementation are as follows:
 1. Use agricultural wastes such as cotton stalks and mushroom residues as the main raw materials to make organic cultivation substrates. The raw materials are inexpensive, rich in resources, widely available, safe and environmentally friendly, and can reduce the pollution caused by the burning of straws. It also has the advantage of making full use of resources and reducing Advantages of fertilizer consumption, labor saving and cost reduction;
 2. The pakchoi cultivation substrate has better soil bulk density, porosity, PH value and EC value, which increases the air permeability, water retention and fertility of the substrate, and improves a more suitable growth environment for pakchoi;
 3. The use of the pakchoi cultivation substrate to grow pakchoi can significantly increase the plant height, leaf length, leaf width, leaf area, and dry and fresh weight of the upper part of pakchoi, and promote the growth and development of pakchoi.
 The test comparison operation is as follows:
 1. Choose full, neat and consistent seeds, soak them and then sow them. The seedling container adopts a 50-hole plug tray, and each hole is sowed with 1 seed. When two leaves and one heart, seedlings with the same growth are selected and transplanted into a plastic flowerpot with a height of 15cm and an upper diameter of 15cm. The treatment is repeated 4 times for each 10 plants. Water has been irrigated from sowing to harvest. The growth indicators were measured on the 35th day after emergence. The raw materials for the growth substrate of Chinese cabbage are cotton stalks, mushroom residue, grass charcoal, and vermiculite, which are mixed in different proportions. Add appropriate amount of water and mix well. The experiment has 4 treatments. The internationally recognized ratio V (Peat) :V (Vermiculite)=2:1, see the proportion and number of each treatment and control matrix figure 1.
 2. For the determination of the physical and chemical properties of the matrix, the data is processed and statistically analyzed using Microsoft Excel 2003 and SPSS 17.0:
 The bulk density and porosity of the matrix are determined by referring to the Lian Zhaohuang method. Take a plastic beaker of known volume (V, the full volume of the beaker is 660ml), weigh it (W1), fill up the natural air-dried matrix, and weigh (W2). The plastic beaker containing the substrate is sealed with double gauze, soaked in water for 24 hours, taken out and weighed (W3), and then taken out and placed upside down to allow the free water in the beaker to drain out, weighed (W4), and calculate the bulk density and porosity according to the formula :
 Bulk density BD (g·cm -3 )=(W2-W1)/660
 Total porosity TP (%) = (W3-W2)/660×100
 Aeration pore AFP (%) = (W3-W4)/660×100
 Water holding pore WRP (%) = total porosity-ventilation pore
 Air-water ratio = aeration pore AFP/water holding pore WRP
 The method for determining the pH and EC value of the substrate refers to the method of Cheng Fei. The air-dried substrate is mixed with deionized water in a volume ratio of 1:5, shaken for 2-3 minutes, then allowed to stand for 30 minutes, filtered, and measured with a PHSJ-3F laboratory pH meter. , Measure EC value with DDS-307A conductivity meter.
 2.1, the original cooking properties of a single substrate
 The physical and chemical properties of various single substrates used when compounding substrates in the experiment are shown figure 2. Among them, the bulk density of straw is relatively small, and the bulk density of the four single substrate materials is sorted as mushroom residue> Straw> Vermiculite> Peat. The total porosity reflects the pore condition of the matrix. It refers to the sum of water-holding pores and aeration pores in the matrix. It is expressed as a percentage (%) of the total volume of the matrix. Vermiculite comes next, and mushroom residue is the lowest. The so-called vent pores are also called macro pores. The function of the vent pores is to store air. If the aeration porosity is large, the matrix has a large air storage capacity and weak water storage capacity. In the experiment, the aeration pores of mushroom residue and cotton straw in the four single substrates were larger, which was significantly higher than that of peat and vermiculite. Both peat and vermiculite had lower aeration pores, which was not conducive to root growth. Water-holding pores are also called small pores, which have a large value and strong water holding capacity of the matrix. In the test, the water-holding pores of vermiculite are relatively high. Mushroom residue has the largest gas-water ratio, and vermiculite has the smallest gas-water ratio. Among the four single-substrate materials, the peat is slightly acidic, and the other three are all alkaline. Among them, the pH value of mushroom residue is the highest. Conductivity (EC value) represents the ionized salt concentration inside the matrix, reflecting the amount of soluble salts contained in the matrix. The EC value of vermiculite for the four single matrix materials is the smallest, and peat is slightly higher than vermiculite, but it is significantly lower For mushroom residue and cotton stalks.
 2.2. Physical and chemical properties of substrates with different ratios
 See the physical and chemical properties of the substrates with different proportions in the experiment image 3. The bulk density of the matrix treated with all formulas is significantly greater than that of CK, but the total porosity of the test treatments and the control is within the range of 60%-90% required by the ideal matrix characteristics, and the total porosity of CK treatment is 56.21%, which is significantly higher than A, B, D treatment, the total porosity is large, the matrix is lighter, and the amount of air and water is large. In the experiment, the aeration pores of the different ratio matrix and the control are generally larger. Treatment C was the largest, 25.45%. The water-holding pores of each treatment and the control were relatively small, and the gas-water ratio was relatively large. The water-holding pore treatment has the highest CK, with large water-holding pores and strong water holding capacity of the matrix, but it is easy to cause poor ventilation and water accumulation in the matrix after watering. The overall pH of each formulation treatment was weakly alkaline, and the control was neutral and slightly acidic, which was significantly lower than other treatments. The pH value was ranked as A> C> D> B> CK. The EC value of the matrix with different ratios is quite different, among which the control is the lowest, which is 0.91ms•cm -1 , Other treatments are significantly higher than CK, indicating to a certain extent that the formula matrix has a strong fertilizer supply capacity, and may achieve the goal of no fertilizer supply during the entire growth period of pakchoi.
 3. Determination of the growth index of Chinese cabbage. The data is processed and statistically analyzed using Microsoft Excel 2003 and SPSS 17.0:
 Measure the plant height, number of leaves, leaf length, and leaf width of Chinese cabbage with a ruler; determine the dry weight by the drying method, and use an analytical balance to weigh the fresh weight of the above ground and underground parts; after weighing the fresh weight of the above ground and underground parts Put it in an oven at 105°C for 15 minutes, keep at 80°C for 48 hours, and weigh the dry weight.
 Root shoot ratio = dry weight of underground part per plant/dry weight of aboveground part of individual plant.
 Use a leaf area meter to measure leaf area; use WinRHIZO root scanning analysis system to measure root morphological indicators: total root length, average root diameter, total root surface area, total root volume, and number of root tips (4 plants were repeated for each treatment).
 3.1. The effect of different substrates on the plant height and leaf number of Chinese cabbage
 The nutrients for the growth of pakchoi seedlings are completely provided by the substrate, and whether the nutrient supply is sufficient is related to the growth of the seedlings. The highest plant height in CK treatment was 17.48 cm, A treatment was 15.7 cm, A treatment was significantly higher than B, C, D treatments, and were 34.2%, 13.7%, 29.8% higher ( Figure 4 ); the maximum number of leaves in CK treatment is 6.6, which is significantly higher than other treatments, followed by treatment A, which is 6.1, and the number of leaves is sorted from large to small CK> A> C> D> B ( Figure 5 ).
 3.2. The effect of different substrates on pakchoi leaf length, petiole length and leaf width
 The maximum petiole length of CK treatment is 8.25cm, which is significantly higher than that of A, B, C, and D treatments, and is 40.7%, 84.4%, 50.9%, 88.6% higher than that of treatments ( Image 6 ); The leaf length of A treatment was 18.7cm, which was significantly higher than that of B, C, and D treatments, and was 49.6%, 13.3%, 37.5% higher than that of CK treatment ( Figure 7 ); The leaf width is the largest in CK treatment, 8.1cm, A treatment is 7.1cm, A treatment is significantly higher than B, C, D treatment, the leaf width is in order from large to small CK> A> C> D> B ( Figure 8 ).
 3.3. The effect of different substrates on the leaf area and crown width of Chinese cabbage
 Maximum leaf area A treatment is 54cm 2 , Significantly larger than CK and B, D treatments ( Picture 9 ); the crown width of CK treatment is 24.6cm, which is significantly higher than that of A, B, C, and D treatments, and is 34.4%, 76.9%, 35.2%, 43.8% higher; crown width of A treatment is 18.3cm, the crown width of CK Significantly higher than other treatments, the plant type is not compact, and the commercial property is poor ( Picture 10 ).
 3.4. Effects of different substrates on the dry and fresh weight and root-shoot ratio of Chinese cabbage
 The dry weight of the plant directly reflects the accumulation of dry matter of the plant and is an important index for evaluating plant yield. In the experiment, the effects of different substrates on the dry and fresh weight and root-shoot ratio of Chinese cabbage Picture 11. The fresh weight of the aboveground part was 13.67g, which was significantly higher than that of treatments B, C, and D. Treatment A was 132%, 56.9%, and 135% higher than treatments B, C, and D, respectively, but there was no significant difference from treatment of CK; The maximum fresh weight of B treatment was 0.24g, which was significantly higher than other treatments, and there was no significant difference between A, C, and D treatments. The dry weight of shoots in A treatment was 0.87g, which was significantly higher than that of B and D treatments, but it was no different from CK treatment. Significant difference; the maximum underground dry weight of treatment B is 0.11g, which is significantly higher than treatments A, C, D, and there is no significant difference between treatments A, C, and D; the dry weight of the whole plant is 0.9g for treatment A, which is significantly higher than that of B , C, D treatment, and no significant difference from CK treatment, C, B, D treatment no significant difference. It can be seen that the dry matter accumulation of CK and A in the seedling stage is larger. The maximum root-shoot ratio in D treatment was 0.22, which was significantly higher than that in A, C, and D treatments.
 3.5. The effect of different substrates on the growth of pakchoi root system
 The root system of plants absorbs a lot of water and minerals from the soil, and at the same time plays a role of fixing and supporting plants. In the experiment, the physical and chemical properties of the matrix with different proportions in the experiment Picture 12 The maximum number of root tips was 4378 for D treatment and 4137 for C treatment. There was no significant difference between A, C and D treatments, but it was significantly higher than CK treatment. D treatment was 93.2% higher than CK treatment. The maximum total root volume of C treatment was 1.99 cm 3 , Significantly higher than A, B, D treatment, and 55.5%, 85.9%, 38.2% higher; root surface area C treatment maximum is 241cm 2 , CK processing minimum is 61cm 2 , C treatment is 295% higher than CK treatment, and the surface area is sorted from large to small C> D> A> B> CK; The maximum average root diameter of C treatment is 0.33mm, there is no significant difference between A, B, C, D treatments, the minimum of CK treatment is 0.23mm, and the C treatment is 43.5% higher than that of CK treatment; the maximum total root length of C treatment is 2319cm, C There was no significant difference in treatments D and D, but it was significantly higher than treatments A, B and CK. The minimum of treatment CK was 779cm, and treatment C was higher than CK treatment by 197%.
 4. Test analysis
 This experiment showed that the plants treated with A and CK were significantly better than other treatments, but the crown width and petiole length of the CK treatment were significantly higher than other treatments, and the commercial properties were poor. In the four treatments A, B, C, and D, the plant height, leaf length, leaf width, and leaf area of treatment A were significantly higher than that of treatments B, C, and D, and the dry and fresh weight of the shoots of treatment A was significantly higher than that of treatment B. , C, D treatment, the underground dry fresh weight B treatment was significantly higher than A, C, D treatment, the root system index B treatment was significantly higher than other treatments, but the cabbage as a leafy vegetable, and the growth cycle is short. In summary, the growth of pakchoi treated with A is the best, and the substrate treated with A is the most conducive to the growth of pakchoi.
 Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it is still possible for those skilled in the art to modify the technical solutions described in the foregoing embodiments, or to make equivalent substitutions to some of the technical features. Within the spirit and principle of the present invention, any modification, equivalent replacement, improvement, etc. shall be included in the protection scope of the present invention.