Culture medium and preparation process thereof

Abstract

The invention relates to the technical field of culture substrates, in particular to a culture substrate and a preparation process thereof. The culture medium sequentially comprises a perlite particle layer, a first fiber base material layer, an ammonium magnesium phosphate slow-release fertilizer layer, a temperature-sensitive water-retaining agent layer and a second fiber base material layer from bottom to top, the thickness ratio of the perlite particle layer to the first fiber base material layer to the ammonium magnesium phosphate slow-release fertilizer layer to the temperature-sensitive water-retaining agent layer to the second fiber base material layer is (5-10): (20-40): (1-2): (0.1-1): (10-30); the raw material of the perlite particle layer is perlite particles with the particle size of 2-4 mm. Synergistic longitudinal permeation and transverse diffusion of water can be effectively achieved, water can be locked at low temperature and high humidity, water can be released at high temperature and low humidity, the porosity is enlarged, the system stability is excellent, nutrient substance loss can be effectively avoided, and the substrate state can be stably maintained even if the substrate is used for a long time.

Description

Technical Field

[0001] The present invention relates to the technical field of cultivation substrates, and particularly to a cultivation substrate and a preparation process thereof. Background Art

[0002] In the field of seedling cultivation, the physical structure, water and fertilizer retention capacity, and microbial activity of cultivation substrates are key factors affecting the survival rate of seedlings. In the fields of facility-based seedling cultivation and intensive cultivation, the physical structure and functional regulation of cultivation substrates directly determine the root development and stress resistance of seedlings.

[0003] Traditional substrates are mainly composed of natural materials such as peat, coconut coir, and vermiculite. Among them, peat occupies a dominant position due to its unique physical and chemical properties. As an incomplete decomposition product of marsh plant residues, peat has advantages such as high organic matter content (>50%), low bulk density (0.04 - 0.27 g / cm 3 ) and large porosity (79 - 98%), and can provide a good initial growth environment for seedlings.

[0004] However, with the increasing requirements for controllability of cultivation conditions in modern agriculture, such traditional substrates gradually expose systematic defects: during the periodic wet-dry alternation process, the fiber network of peat substrates is prone to irreversible pore collapse, seriously hindering root oxygen exchange, which is the key inducement for root rot and stunted seedlings of transplanted seedlings.

[0005] In the prior art, to improve the water retention performance, an improved scheme of adding synthetic water retention agents is generally adopted. Although water-absorbing resins represented by sodium polyacrylate can increase the water retention rate of substrates, such materials have a high pore filling rate during water absorption and expansion, resulting in a decrease in the gas diffusion coefficient. More seriously, the interfacial binding force between the resin and peat fibers is weak, and phase separation is prone to occur under temperature / humidity alternating conditions, forming a local closed-pore structure, which instead exacerbates the anisotropy of water permeability and air permeability of the substrate. Moreover, conventional water retention materials lack environmental response characteristics and cannot dynamically adjust water supply according to the transpiration requirements of plants, and instead exacerbate the water stress inside the substrate during high-temperature and strong-light periods, seriously restricting the large-scale production of crops.

[0006] Therefore, developing a cultivation substrate with self-adaptive adjustment function, stable system, water retention and air permeability has become an urgent technical problem to be solved in the field of agricultural cultivation substrates. Summary of the Invention

[0007] The purpose of the present invention is to solve the deficiencies existing in the prior art and to propose a cultivation substrate and a preparation process thereof.

[0008] A cultivation substrate, from bottom to top in sequence: perlite particle layer, first fiber base material layer, magnesium ammonium phosphate slow-release fertilizer layer, temperature-sensitive water-retaining agent layer, and second fiber base material layer; the thickness ratio of the perlite particle layer, first fiber base material layer, magnesium ammonium phosphate slow-release fertilizer layer, temperature-sensitive water-retaining agent layer, and second fiber base material layer is 5-10:20-40:1-2:0.1-1:10-30; the raw material of the perlite particle layer is perlite particles with a particle size of 2-4mm.

[0009] Preferably, the raw materials of both the first fiber base material layer and the second fiber base material layer are fiber base materials, and the raw materials of the fiber base materials include: coconut coir, cassava residue, and the mass ratio of coconut coir to cassava residue is 10-20:1-5.

[0010] Preferably, the fiber base material is prepared by the following specific steps: Mix coconut coir and cassava residue evenly, crush them to a particle size ≤2mm, add them to a sodium hydroxide solution and let stand for 5-10h, filter, wash with water until neutral, dry to a system moisture content of 5-10%, feed them into a steam explosion tank, and introduce 1.5-2MPa saturated steam to maintain for 100-120s and then instantaneously release the pressure.

[0011] Preferably, the concentration of the sodium hydroxide solution is 0.5-1.5mol / L.

[0012] Preferably, the drying temperature is 70-80°C.

[0013] Preferably, the raw material of the temperature-sensitive water-retaining agent layer is a temperature-sensitive water-retaining agent, and the raw materials of the temperature-sensitive water-retaining agent include by mass: 5-20 parts of peat, 1-5 parts of bamboo powder, 1-2 parts of N-isopropylacrylamide, 0.001-0.01 parts of N,N'-methylenebisacrylamide, and 0.01-0.1 parts of initiator.

[0014] Preferably, the temperature-sensitive water-retaining agent is prepared by the following steps: Add peat and bamboo powder to a sodium hydroxide solution, reflux and stir at 70-90°C for 1-2h, cool to room temperature, adjust the pH of the system to 6.5-7 with 1mol / L hydrochloric acid, filter, wash, vacuum dry, add N-isopropylacrylamide and N,N'-methylenebisacrylamide and mix, add the initiator under nitrogen protection, stir at 60-70°C for 1-2h, add potassium dihydrogen phosphate solution and continue to stir for 10-30min, and vacuum dry.

[0015] Preferably, the initiator is a persulfate, specifically ammonium persulfate.

[0016] Preferably, the concentration of the sodium hydroxide solution is 0.5-1.5mol / L.

[0017] Preferably, the concentration of the potassium dihydrogen phosphate solution is 0.5-1mol / L.

[0018] The preparation method of the above cultivation substrate comprises the following steps: laying a perlite particle layer at the bottom layer, covering a first fiber substrate layer on the perlite particle layer, then uniformly laying magnesium ammonium phosphate slow-release fertilizer and a temperature-sensitive water-retaining agent layer in sequence, covering a second fiber substrate layer on the temperature-sensitive water-retaining agent layer, rolling and compacting, and irradiating and sterilizing.

[0019] Preferably, the rolling pressure is 0.1 - 0.15 MPa.

[0020] Preferably, 60 Co-γ rays are used for irradiation sterilization, and the irradiation dose is 3 - 8 kGy.

[0021] Beneficial effects:

[0022] In the present invention, coconut coir and cassava residues are compounded and treated with sodium hydroxide, which not only promotes internal swelling to form a microporous structure, but also undergoes steam explosion, resulting in a rich internal void structure. The obtained fiber substrate not only has excellent adsorption performance, but also has excellent water retention and air permeability effects.

[0023] Due to the small adsorption capacity of the peat structure, nutrients are lost extremely quickly. In the present invention, after peat and bamboo powder are treated with sodium hydroxide, the crystalline structures of lignin and cellulose are destroyed, exposing more hydroxyl sites. N-isopropylacrylamide is compounded and combined with the above products through free radical polymerization. The obtained temperature-sensitive water-retaining agent has an expansion and water absorption effect in a low-temperature environment, while it shrinks to release water when the temperature is higher than 32 °C. At the same time, the adsorbed nutrients are desorbed more quickly with the increase of temperature. When compounded with magnesium ammonium phosphate slow-release fertilizer, it realizes the coordinated slow release of water and nutrients.

[0024] In the present invention, a perlite particle layer is laid at the bottom layer, and then a first fiber substrate layer, a magnesium ammonium phosphate slow-release fertilizer layer, a temperature-sensitive water-retaining agent layer, and a second fiber substrate layer are covered in sequence, which can effectively realize the coordination of longitudinal water penetration and lateral diffusion, and can lock water at low temperature and high humidity, while shrinking and releasing water to form internal connected pores in a high-temperature environment (>32 °C), promoting gas exchange, with excellent system stability, effectively avoiding the loss of nutrients, and maintaining the substrate state stably even after long-term use.

[0025] The cultivation substrate of the present invention has been confirmed by cultivation experiments. When using the cultivation substrate obtained by the present invention to plant Dendrobium officinale, the growth condition of Dendrobium officinale is good. At the same time, compared with the traditional substrate, when using the cultivation substrate obtained by the present invention to plant Dendrobium officinale, the survival rate of Dendrobium officinale is high, the growth is good, and the polysaccharide content of Dendrobium officinale is high, which can realize the sustainable development and utilization of Dendrobium officinale resources and is worthy of popularization and use. Description of the drawings

[0026] Figure 1 It is a comparison chart of the bulk density and water holding capacity of the cultivation substrates obtained in Example 5 and Comparative Examples 1 - 2.

[0027] Figure 2 The comparative diagram of the total porosity and air-water ratio of the cultivation substrates obtained in Example 5 and Comparative Examples 1-2.

[0028] Figure 3 The comparative diagram of the water release rate and porosity change rate of the cultivation substrates obtained in Example 5 and Comparative Examples 1-2 after standing at 35°C for 8 hours.

[0029] Figure 4 The comparative diagram of the above-ground fresh weight and underground fresh weight of Dendrobium officinale in each group at 180 days in the comparative experiment of transplanting Dendrobium officinale using the cultivation substrates obtained in Example 5 and Comparative Examples 1-2.

[0030] Figure 5 The comparative diagram of the longest root system and polysaccharide content of Dendrobium officinale in each group at 180 days in the comparative experiment of transplanting Dendrobium officinale using the cultivation substrates obtained in Example 5 and Comparative Examples 1-2.

[0031] Figure 6 The comparative diagram of the above-ground fresh weight and underground fresh weight of Dendrobium officinale in each group at 180 days in the comparative experiment of transplanting Dendrobium officinale 3 times using the cultivation substrates obtained in Example 5 and Comparative Examples 1-2.

[0032] Figure 7 The comparative diagram of the longest root system and polysaccharide content of Dendrobium officinale in each group at 180 days in the comparative experiment of transplanting Dendrobium officinale 3 times using the cultivation substrates obtained in Example 5 and Comparative Examples 1-2.

[0033] Figure 8 The comparative diagram of the total porosity and air-water ratio of the cultivation substrates in each group after the comparative experiment of transplanting Dendrobium officinale 3 times using the cultivation substrates obtained in Example 5 and Comparative Examples 1-2. Detailed implementation mode

[0034] The present invention will be further explained below with reference to specific examples.

[0035] The ammonium magnesium phosphate slow-release fertilizer used below is purchased from a certain marine technology company in Shandong.

[0036] Example 1

[0037] A cultivation substrate, from bottom to top in sequence: a perlite particle layer with a thickness of 5 mm, a first fiber substrate layer with a thickness of 20 mm, an ammonium magnesium phosphate slow-release fertilizer layer with a thickness of 1 mm, a temperature-sensitive water-retaining agent layer with a thickness of 0.1 mm, and a second fiber substrate layer with a thickness of 10 mm.

[0038] The raw material of the perlite particle layer is perlite particles with a particle size of 2 mm.

[0039] The raw materials of the first fiber base material layer and the second fiber base material layer are both fiber base materials, and the fiber base materials are prepared by the following specific steps: Mix 1000 g of coconut coir and 100 g of cassava residue evenly, crush them to a particle size of ≤2 mm, add them to 5000 g of sodium hydroxide solution with a concentration of 0.5 mol / L, let stand for 5 h, filter, wash with water until neutral, dry at a temperature of 70 °C until the moisture content of the system is 5%, send them into a steam explosion tank, and introduce 1.5 MPa of saturated steam to maintain for 100 s and then instantaneously release the pressure.

[0040] The raw material of the temperature-sensitive water-retaining agent layer is a temperature-sensitive water-retaining agent, and the temperature-sensitive water-retaining agent is prepared by the following steps: Add 500 g of peat and 100 g of bamboo powder to 4000 g of sodium hydroxide solution with a concentration of 0.5 mol / L, reflux and stir at a temperature of 70 °C for 1 h, cool to room temperature, adjust the pH of the system to 6.5 - 7 with 1 mol / L hydrochloric acid, filter, wash, dry in vacuum, add 100 g of N-isopropylacrylamide and 0.1 g of N,N'-methylenebisacrylamide and mix, add 1 g of ammonium persulfate under nitrogen protection, stir at a temperature of 60 °C for 1 h, add 500 g of potassium dihydrogen phosphate solution with a concentration of 0.5 mol / L, continue to stir for 10 min, and dry in vacuum.

[0041] The preparation method of the above cultivation substrate includes the following steps: Lay a perlite particle layer at the bottom, cover the first fiber base material layer on the perlite particle layer, then evenly lay ammonium magnesium phosphate slow-release fertilizer and the temperature-sensitive water-retaining agent layer in sequence, and then cover the second fiber base material layer on the temperature-sensitive water-retaining agent layer, roll and compact at 0.1 MPa, and use 60 Co-γ rays for irradiation sterilization, and the irradiation dose is 5 kGy.

[0042] Example 2

[0043] A cultivation substrate, from bottom to top in sequence: a perlite particle layer with a thickness of 10 mm, a first fiber base material layer with a thickness of 40 mm, an ammonium magnesium phosphate slow-release fertilizer layer with a thickness of 2 mm, a temperature-sensitive water-retaining agent layer with a thickness of 1 mm, and a second fiber base material layer with a thickness of 30 mm.

[0044] The raw material of the perlite particle layer is perlite particles with a particle size of 4 mm.

[0045] The raw materials of the first fiber base material layer and the second fiber base material layer are both fiber base materials, and the fiber base materials are prepared by the following specific steps: Mix 2000 g of coconut coir and 500 g of cassava residue evenly, crush them to a particle size of ≤2 mm, add them to 10000 g of sodium hydroxide solution with a concentration of 1.5 mol / L, let stand for 10 h, filter, wash with water until neutral, dry at a temperature of 80 °C until the moisture content of the system is 10%, send them into a steam explosion tank, and introduce 2 MPa of saturated steam to maintain for 120 s and then instantaneously release the pressure.

[0046] The raw material of the temperature-sensitive water-retaining agent layer is a temperature-sensitive water-retaining agent, which is prepared by the following steps: Add 2000 g of peat and 500 g of bamboo powder to 10000 g of a sodium hydroxide solution with a concentration of 1.5 mol / L, reflux and stir at 90 °C for 2 h, cool to room temperature, adjust the pH of the system to 6.5 - 7 with 1 mol / L hydrochloric acid, filter, wash, vacuum dry, add 200 g of N-isopropylacrylamide and 1 g of N,N'-methylenebisacrylamide, add 10 g of ammonium persulfate under nitrogen protection, stir at 70 °C for 2 h, add 1000 g of a potassium dihydrogen phosphate solution with a concentration of 1 mol / L, continue to stir for 30 min, and vacuum dry.

[0047] The preparation method of the above cultivation substrate includes the following steps: Lay a perlite particle layer at the bottom layer, cover the first fiber substrate layer on the perlite particle layer, then uniformly lay ammonium magnesium phosphate slow-release fertilizer and the temperature-sensitive water-retaining agent layer in sequence, cover the second fiber substrate layer on the temperature-sensitive water-retaining agent layer, roll and compact at 0.15 MPa, and use 60 Co-γ rays for irradiation sterilization, and the irradiation dose is 8 kGy.

[0048] Example 3

[0049] A cultivation substrate, from bottom to top in sequence: a perlite particle layer with a thickness of 7 mm, a first fiber substrate layer with a thickness of 35 mm, an ammonium magnesium phosphate slow-release fertilizer layer with a thickness of 1.2 mm, a temperature-sensitive water-retaining agent layer with a thickness of 0.8 mm, and a second fiber substrate layer with a thickness of 15 mm.

[0050] The raw material of the perlite particle layer is perlite particles with a particle size of 3.5 mm.

[0051] The raw materials of the first fiber substrate layer and the second fiber substrate layer are both fiber substrates, and the fiber substrate is prepared by the following specific steps: Mix 1200 g of coconut coir and 400 g of cassava residue evenly, crush to a particle size ≤ 2 mm, add to 7000 g of a sodium hydroxide solution with a concentration of 1.2 mol / L and let stand for 7 h, filter, wash with water until neutral, dry at 77 °C until the moisture content of the system is 7%, feed it into a steam explosion tank, and introduce 1.9 MPa saturated steam to maintain for 105 s and then instantaneously relieve the pressure.

[0052] The raw material of the temperature-sensitive water-retaining agent layer is a temperature-sensitive water-retaining agent, which is prepared by the following steps: Add 1600 g of peat and 200 g of bamboo powder to 8000 g of a sodium hydroxide solution with a concentration of 0.8 mol / L, reflux and stir at 85 °C for 80 min, cool to room temperature, adjust the pH of the system to 6.5 - 7 with 1 mol / L hydrochloric acid, filter, wash, vacuum dry, add 180 g of N-isopropylacrylamide and 0.3 g of N,N'-methylenebisacrylamide and mix, add 8 g of ammonium persulfate under nitrogen protection, stir at 62 °C for 100 min, add 700 g of a potassium dihydrogen phosphate solution with a concentration of 0.8 mol / L, continue to stir for 15 min, and vacuum dry.

[0053] The preparation method of the above cultivation substrate includes the following steps: Lay a perlite particle layer at the bottom layer, cover a first fiber substrate layer on the perlite particle layer, then evenly lay magnesium ammonium phosphate slow-release fertilizer and a temperature-sensitive water-retaining agent layer in sequence, cover a second fiber substrate layer on the temperature-sensitive water-retaining agent layer, roll and compact at 0.13 MPa, and use 60 Co-γ ray for irradiation sterilization, and the irradiation dose is 6 kGy.

[0054] Example 4

[0055] A cultivation substrate, from bottom to top in sequence: a perlite particle layer with a thickness of 9 mm, a first fiber substrate layer with a thickness of 25 mm, a magnesium ammonium phosphate slow-release fertilizer layer with a thickness of 1.8 mm, a temperature-sensitive water-retaining agent layer with a thickness of 0.2 mm, and a second fiber substrate layer with a thickness of 25 mm.

[0056] The raw material of the perlite particle layer is perlite particles with a particle size of 2.5 mm.

[0057] The raw materials of the first fiber substrate layer and the second fiber substrate layer are both fiber substrates, and the fiber substrate is prepared by the following specific steps: Mix 1800 g of coconut coir and 200 g of cassava residue evenly, crush to a particle size ≤ 2 mm, add to 9000 g of a sodium hydroxide solution with a concentration of 0.8 mol / L and let stand for 9 h, filter, wash with water until neutral, dry at 73 °C until the moisture content of the system is 9%, feed it into a steam explosion tank, and introduce 1.6 MPa of saturated steam to maintain for 115 s and then instantaneously release the pressure.

[0058] The raw material of the temperature-sensitive water-retaining agent layer is a temperature-sensitive water-retaining agent, which is prepared by the following steps: Add 800 g of peat and 400 g of bamboo powder to 6000 g of a sodium hydroxide solution with a concentration of 1.2 mol / L, reflux and stir at 75 °C for 100 min, cool to room temperature, adjust the pH of the system to 6.5 - 7 with 1 mol / L hydrochloric acid, filter, wash, vacuum dry, add 120 g of N-isopropylacrylamide and 0.7 g of N,N'-methylenebisacrylamide and mix, add 4 g of ammonium persulfate under nitrogen protection, stir at 68 °C for 80 min, add 900 g of a potassium dihydrogen phosphate solution with a concentration of 0.6 mol / L, continue to stir for 25 min, and vacuum dry.

[0059] The preparation method of the above cultivation substrate includes the following steps: Lay a perlite particle layer at the bottom layer, cover the first fiber substrate layer on the perlite particle layer, then uniformly lay magnesium ammonium phosphate slow-release fertilizer and the temperature-sensitive water-retaining agent layer in sequence, cover the second fiber substrate layer on the temperature-sensitive water-retaining agent layer, roll and compact at 0.11 MPa, and use 60 Co-γ rays for irradiation sterilization, and the irradiation dose is 7 kGy.

[0060] Example 5

[0061] A cultivation substrate, from bottom to top in sequence: a perlite particle layer with a thickness of 8 mm, a first fiber substrate layer with a thickness of 30 mm, a magnesium ammonium phosphate slow-release fertilizer layer with a thickness of 1.5 mm, a temperature-sensitive water-retaining agent layer with a thickness of 0.5 mm, and a second fiber substrate layer with a thickness of 20 mm.

[0062] The raw material of the perlite particle layer is perlite particles with a particle size of 3 mm.

[0063] The raw materials of the first fiber substrate layer and the second fiber substrate layer are both fiber substrates, and the fiber substrate is prepared by the following specific steps: Mix 1500 g of coconut coir and 300 g of cassava residue evenly, crush to a particle size ≤ 2 mm, add to 8000 g of a sodium hydroxide solution with a concentration of 1 mol / L and let stand for 8 h, filter, wash with water until neutral, dry at 75 °C until the moisture content of the system is 8%, feed into a steam explosion tank, and introduce 1.8 MPa of saturated steam to maintain for 110 s and then instantaneously relieve pressure.

[0064] The raw material of the temperature-sensitive water-retaining agent layer is a temperature-sensitive water-retaining agent, which is prepared by the following steps: Add 1200 g of peat and 300 g of bamboo powder to 7000 g of a sodium hydroxide solution with a concentration of 1 mol / L, reflux and stir at 80 °C for 90 min, cool to room temperature, adjust the pH of the system to 6.5 - 7 with 1 mol / L hydrochloric acid, filter, wash, vacuum dry, add 150 g of N-isopropylacrylamide and 0.5 g of N,N'-methylenebisacrylamide. Using water as a solvent, the total solid content is controlled at 15 - 20%, add 6 g of ammonium persulfate under nitrogen protection, stir at 65 °C for 90 min, add 800 g of a potassium dihydrogen phosphate solution with a concentration of 0.7 mol / L, continue to stir for 20 min, and vacuum dry.

[0065] The preparation method of the above cultivation substrate includes the following steps: Lay a perlite particle layer at the bottom layer, cover a first fiber substrate layer on the perlite particle layer, then sequentially and evenly lay magnesium ammonium phosphate slow-release fertilizer and the temperature-sensitive water-retaining agent layer, and then cover a second fiber substrate layer on the temperature-sensitive water-retaining agent layer, roll and compact at 0.12 MPa, and use 60 Co-γ rays for irradiation sterilization, and the irradiation dose is 3.2 kGy.

[0066] Comparative Example 1

[0067] A cultivation substrate, from bottom to top in sequence: a perlite particle layer with a thickness of 8 mm, a first fiber substrate layer with a thickness of 30 mm, a magnesium ammonium phosphate slow-release fertilizer layer with a thickness of 1.5 mm, a water-retaining agent layer with a thickness of 0.5 mm, and a second fiber substrate layer with a thickness of 20 mm.

[0068] The raw material of the perlite particle layer is perlite particles with a particle size of 3 mm.

[0069] The raw materials of the first fiber substrate layer and the second fiber substrate layer are both fiber substrates, and the fiber substrate is prepared by the following specific steps: Mix 1500 g of coconut coir and 300 g of tapioca residue evenly, crush to a particle size ≤ 2 mm, add to 8000 g of a sodium hydroxide solution with a concentration of 1 mol / L and let stand for 8 h, filter, wash with water until neutral, dry at 75 °C until the water content of the system is 8%, feed it into a steam explosion tank, and introduce 1.8 MPa of saturated steam to maintain for 110 s and then instantaneously relieve the pressure.

[0070] The raw material of the water-retaining agent layer is a water-retaining agent, which is prepared by the following steps: Add 1200 g of peat and 300 g of bamboo powder to 800 g of a potassium dihydrogen phosphate solution with a concentration of 0.7 mol / L and stir for 20 min, and vacuum dry.

[0071] The preparation method of the above cultivation substrate includes the following steps: laying a perlite particle layer at the bottom layer, covering a first fiber substrate layer on the perlite particle layer, then sequentially and evenly laying ammonium magnesium phosphate slow-release fertilizer and a temperature-sensitive water-retaining agent layer, covering a second fiber substrate layer on the temperature-sensitive water-retaining agent layer, rolling and compacting at 0.12 MPa, and using 60 Co-γ rays for irradiation sterilization, and the irradiation dose is 3.2 kGy.

[0072] Comparative Example 2

[0073] A cultivation substrate, from bottom to top in sequence: a perlite particle layer with a thickness of 8 mm, a first fiber substrate layer with a thickness of 30 mm, an ammonium magnesium phosphate slow-release fertilizer layer with a thickness of 1.5 mm, a temperature-sensitive water-retaining agent layer with a thickness of 0.5 mm, and a second fiber substrate layer with a thickness of 20 mm.

[0074] The raw material of the perlite particle layer is perlite particles with a particle size of 3 mm.

[0075] The raw materials of the first fiber substrate layer and the second fiber substrate layer are both fiber substrates. The fiber substrate is prepared by the following specific steps: mixing 1500 g of coconut coir and 300 g of tapioca residue evenly, crushing to a particle size ≤ 2 mm, adding to 8000 g of a sodium hydroxide solution with a concentration of 1 mol / L, standing for 8 h, filtering, washing with water until neutral, drying at a temperature of 75 °C until the moisture content of the system is 8%, feeding into a steam explosion tank, and introducing 1.8 MPa of saturated steam to maintain for 110 s and then instantaneously releasing the pressure.

[0076] The raw material of the temperature-sensitive water-retaining agent layer is a temperature-sensitive water-retaining agent. The temperature-sensitive water-retaining agent is prepared by the following steps: mixing 1200 g of peat, 300 g of bamboo powder, 150 g of N-isopropylacrylamide, and 0.5 g of N,N'-methylenebisacrylamide, using water as a solvent, controlling the total solid content at 15-20%, adding 6 g of ammonium persulfate under nitrogen protection, stirring at a temperature of 65 °C for 90 min, adding 800 g of a potassium dihydrogen phosphate solution with a concentration of 0.7 mol / L, continuing to stir for 20 min, and drying in vacuum.

[0077] The preparation method of the above cultivation substrate includes the following steps: laying a perlite particle layer at the bottom layer, covering a first fiber substrate layer on the perlite particle layer, then sequentially and evenly laying ammonium magnesium phosphate slow-release fertilizer and a temperature-sensitive water-retaining agent layer, covering a second fiber substrate layer on the temperature-sensitive water-retaining agent layer, rolling and compacting at 0.12 MPa, and using 60 Co-γ rays for irradiation sterilization, and the irradiation dose is 3.2 kGy.

[0078] The physical properties of the cultivation substrates obtained in Example 5 and Comparative Examples 1-2 were measured. Take a 5L beaker and weigh its net weight (W1); fill each group of naturally air-dried cultivation substrates into the beaker to the 3L graduation line and weigh (W2); then seal the beaker containing the substrate with two layers of wet gauze and soak it in water at 20°C for 24 h (the water level should always be at least 2 cm above the top of the container), take it out of the water, pour out the water above the 3L graduation line, and weigh it in the saturated water state (W3), and weigh the wet gauze used for sealing (W4); finally, wrap the beaker with the wet gauze and invert it for 8 h to let the water (gravitational water) in the beaker drain freely, and weigh (W5).

[0079] Bulk density = (W2 - W1) ÷ 3000.

[0080] Water holding capacity = (W5 - W1 - W4) ÷ (W2 - W1) × 100%.

[0081] Total porosity = (W3 - W2) ÷ 3000 × 100%.

[0082] Air-water ratio = aeration porosity / water holding porosity. Among them, aeration porosity = (W3 + W4 - W5) ÷ 3000 × 100%; water holding porosity = total porosity - aeration porosity.

[0083] As Figure 1 and Figure 2 shown, the cultivation substrate obtained in Example 5 had the smallest bulk density, while the water holding capacity, total porosity and air-water ratio were the largest, being superior to Comparative Examples 1-2 (P < 0.05).

[0084] After the above-mentioned free drainage, each group of cultivation substrates was placed in a constant temperature and humidity chamber at 35°C and 50% RH and left standing for 8 h. Subsequently, the beaker was wrapped with the above-mentioned wet gauze and inverted for 8 h to let the water (gravitational water) in the beaker drain freely, and weighed (W6); then it was soaked in water at 20°C for 24 h (the water level should always be at least 2 cm above the top of the container), taken out of the water, and the water above the 3L graduation line was poured out, and weighed in the saturated water state (W7).

[0085] Water release rate = (W5 - W6) ÷ (W5 - W1 - W4) × 100%.

[0086] Porosity change rate = (W4 + W7 - W6) ÷ (W4 + W3 - W5) × 100%.

[0087] As Figure 3 shown, the cultivation substrate obtained in Example 5 had the highest water release rate and porosity change rate at a higher temperature, being superior to Comparative Examples 1-2 (P < 0.05).

[0088] A comparative experiment on the transplantation of Dendrobium officinale was carried out using the cultivation substrates obtained in Example 5 and Comparative Examples 1-2. The transplantation was carried out from March 11th to March 16th and ended from December 15th to December 20th. The experiment adopted a randomized block design and destructive sampling. Each group used the cultivation substrates obtained in Example 5 and Comparative Examples 1-2, with 9 pots in each group and two Dendrobium officinale seedlings in each pot.

[0089] When planting, the roots were naturally stretched, the substrate covered all the roots, and the root-fixing water was thoroughly watered after planting; for daily ventilation, lighting, temperature and humidity, etc., the conventional cultivation management of Dendrobium officinale was followed.

[0090] The survival rate was investigated 30 days after planting, and the survival rate of each group was greater than 90%; the number of germinations was investigated 60 days after planting, and the number of germinations in each group was greater than 6.80; the plant height was investigated 90 days after planting, and the plant height in each group was greater than 5.65 cm. It was confirmed that the cultivation substrates of each group could effectively protect the transplantation of Dendrobium officinale.

[0091] At 180 days, the above-ground fresh weight, underground fresh weight and the longest root system were measured, and the polysaccharide content of Dendrobium officinale was detected.

[0092] As Figure 4 and Figure 5 shown, when transplanting Dendrobium officinale using the cultivation substrate obtained in Example 5, its above-ground fresh weight, underground fresh weight, the longest root system and polysaccharide content were all the largest, superior to Comparative Examples 1-2 (P < 0.05).

[0093] Dendrobium officinale was transplanted again 2 times according to the above steps (that is, Dendrobium officinale was transplanted 3 times in total with the same cultivation substrate), and no any materials were added to the cultivation substrate during this period. During the third transplantation period, Dendrobium officinale was detected (at 180 days, the above-ground fresh weight, underground fresh weight and the longest root system were measured, and the polysaccharide content of Dendrobium officinale was detected).

[0094] As Figure 6 and Figure 7 shown, after the cultivation substrates of each group were transplanted with Dendrobium officinale 3 times, the above-ground fresh weight, underground fresh weight, the longest root system and polysaccharide content of Dendrobium officinale obtained from the third transplantation all decreased significantly; but when transplanting Dendrobium officinale using the cultivation substrate obtained in Example 5, its above-ground fresh weight, underground fresh weight, the longest root system and polysaccharide content were still the largest, superior to Comparative Examples 1-2 (P < 0.05).

[0095] After the end of the third transplantation, the total porosity and air-water ratio of the cultivation substrates of each group were detected again. As Figure 8 shown, the total porosity and air-water ratio of the cultivation substrates of each group decreased; but the total porosity and air-water ratio of the cultivation substrate obtained in Example 5 were still the largest, superior to Comparative Examples 1-2 (P < 0.05).

[0096] The applicant believes that: This is because in the present invention, coconut coir and cassava residues are compounded and treated with sodium hydroxide, which not only promotes internal swelling to form a microporous structure, but also undergoes steam explosion, resulting in a rich internal void structure. The obtained fiber substrate not only has excellent adsorption performance, but also has an excellent water retention and air permeability effect. At the same time, in the present invention, peat and bamboo powder are treated with sodium hydroxide, the crystalline structures of lignin and cellulose are destroyed, exposing more hydroxyl sites. N-isopropylacrylamide is compounded and combined with the above products through free radical polymerization. The obtained temperature-sensitive water retaining agent has a swelling and water absorption effect in a low-temperature environment, while when the temperature is higher than 32 °C, it shrinks to release water, and the adsorbed nutrients are desorbed more rapidly with the increase in temperature. When compounded with magnesium ammonium phosphate slow-release fertilizer, the coordinated slow release of water and nutrients is achieved. By laying a perlite particle layer at the bottom layer of the present invention, and then successively covering a first fiber substrate layer, a magnesium ammonium phosphate slow-release fertilizer layer, a temperature-sensitive water retaining agent layer, and a second fiber substrate layer, the coordination of longitudinal water penetration and lateral diffusion can be effectively achieved, and water can be locked in at low temperature and high humidity, while water is released and the porosity is increased at high temperature and low humidity. The system has excellent stability, can effectively avoid the loss of nutrients, and can stably maintain the matrix state even after long-term use.

[0097] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A cultivation medium, characterized in that: From bottom to top, they are: perlite particle layer, first fiber substrate layer, magnesium ammonium phosphate slow-release fertilizer layer, thermosensitive water retaining agent layer, and second fiber substrate layer; The thickness ratio of the perlite particle layer, the first fiber substrate layer, the magnesium ammonium phosphate slow-release fertilizer layer, the thermosensitive water retaining agent layer and the second fiber substrate layer is 5-10:20-40:1-2:0.1-1:10-30; The raw material of the perlite granular layer is perlite granules with a particle size of 2-4 mm.

2. The cultivation substrate according to claim 1, characterized in that: The raw materials of the first fiber substrate layer and the second fiber substrate layer are both fiber substrates. The raw materials of the fiber substrates include: coconut bran and cassava residue. The mass ratio of coconut bran to cassava residue is 10-20:1-5.

3. The cultivation substrate according to claim 2, characterized in that: The fiber substrate is prepared by the following specific steps: coconut bran and cassava residue are mixed evenly, crushed to a particle size of ≤2 mm, added to a sodium hydroxide solution and allowed to stand for 5-10 hours, filtered, washed with water to be neutral, dried to a system moisture content of 5-10%, sent to a steam explosion tank, and 1.5-2MPa saturated steam is introduced to maintain 100-120 seconds and then the pressure is released instantly.

4. The cultivation substrate according to claim 3, characterized in that: The concentration of the sodium hydroxide solution is 0.5-1.5 mol / L.

5. The cultivation substrate according to claim 3, characterized in that: The drying temperature is 70-80℃.

6. The cultivation substrate according to claim 1, characterized in that: The raw material of the thermosensitive water retaining agent layer is a thermosensitive water retaining agent, and the raw materials of the thermosensitive water retaining agent include, by mass, 5-20 parts of peat, 1-5 parts of bamboo powder, 1-2 parts of N-isopropyl acrylamide, 0.001-0.01 parts of N,N'-methylenebisacrylamide, and 0.01-0.1 parts of initiator.

7. The cultivation substrate according to claim 6, characterized in that: The thermosensitive water-retaining agent is prepared by the following steps: adding peat and bamboo powder to sodium hydroxide solution, reflux stirring at 70-90°C for 1-2 hours, cooling to room temperature, filtering, washing, vacuum drying, adding N-isopropylacrylamide and N,N'-methylenebisacrylamide to mix, adding initiator under nitrogen protection, stirring at 60-70°C for 1-2 hours, adding potassium dihydrogen phosphate solution and continuing stirring for 10-30 minutes, and vacuum drying.

8. The cultivation substrate according to claim 6, characterized in that: The initiator is a persulfate, specifically ammonium persulfate.

9. The cultivation substrate according to claim 6, characterized in that: The concentration of the sodium hydroxide solution is 0.5-1.5 mol / L, and the concentration of the potassium dihydrogen phosphate solution is 0.5-1 mol / L.

10. A method for preparing a cultivation substrate as claimed in any one of claims 1 to 9, characterized in that: The method comprises the following steps: laying a perlite particle layer on the bottom layer, covering the first fiber substrate layer on the perlite particle layer, then evenly laying magnesium ammonium phosphate slow-release fertilizer and a thermosensitive water-retaining agent layer in sequence, and then covering the second fiber substrate layer on the thermosensitive water-retaining agent layer, rolling and compacting, and irradiating and sterilizing.

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