Straw-based degradable plant seedling cultivation porous substrate and preparation method thereof

Abstract

The invention relates to the technical field of plant seedling raising and industrialized seedling raising substrates, and discloses a straw-based degradable plant seedling raising cultivation porous substrate and a preparation method thereof.The straw-based degradable plant seedling raising cultivation porous substrate is characterized in that polyvinyl alcohol monomers are cross-linked and cured to form a cross-linked carrier, and straw powder, charcoal powder and a slow release fertilizer are loaded in the cross-linked carrier; the cross-linked carrier is prepared by uniformly mixing the raw materials of a polyvinyl alcohol aqueous solution, a pore-forming agent, a foaming agent, a dispersing and defoaming agent, a compatibility improver, a plasticizer and a cross-linking agent, heating and curing. The matrix material in the scheme has good biocompatibility, specifically, the raw materials including the cross-linked carrier formed by cross-linking and curing the polyvinyl alcohol monomer, the straw powder, the charcoal powder and the slow release fertilizer are all very friendly to plant root systems and plant tissues and high in safety, support and nutrition can be effectively provided for the plant seedling raising stage, and the matrix material has good application prospects. The plant seedling growing process is promoted.

Description

Technical Field

[0001] The invention relates to the field of plant seedling cultivation technology and factory-based seedling cultivation matrix technology, and in particular to a straw-based degradable plant seedling cultivation porous matrix and a preparation method thereof. Background Art

[0002] Lightweight, clean, water- and fertilizer-retaining plant seedling and cultivation substrates are an important foundation for factory-scale plant seedling and production. High-quality substrates are crucial to controlling plant production cycles, seedling specifications and quality. Currently, plant seedlings and cultivation mostly use natural soil or a mixture of soil and substrates. Although the water- and fertilizer-retaining effects are acceptable, their high bulk density and uncontrollable porosity limit their large-scale application.

[0003] Prior art CN107285851A discloses a matrix for the introduction and cultivation of garden plants and its preparation, comprising a polyvinyl formal carrier, biochar and decomposed material; the biochar and decomposed material are in situ composited on the surface and / or pores of the polyvinyl formal carrier, and the obtained material has stable and excellent performance. However, the prior art still has the following technical problems: (1) The prior art uses a polyvinyl formal carrier as the main matrix, and the polyvinyl formal carrier may be absorbed by the plant root system, causing root damage and affecting plant growth; (2) The matrix obtained by the prior art is stable in performance and not easy to degrade. The main reason for this is that the polyvinyl formal carrier is not easy to degrade in the soil, and long-term accumulation is likely to cause soil pollution, thereby further reducing production safety.

[0004] In view of this, the development of a lighter, cleaner, water- and fertilizer-retaining, uniformly adjustable pore size, green and degradable porous matrix for plant seedling cultivation can not only effectively make up for the shortcomings of existing technologies, but also effectively improve the performance of the cultivation matrix and enhance the plant seedling cultivation effect, which is of great significance for achieving efficient and high-quality seedling cultivation and plant factory production. Summary of the invention

[0005] The present invention aims to provide a straw-based degradable porous substrate for plant seedling cultivation and a preparation method thereof, so as to solve the technical problem that the existing cultivation substrate has low safety.

[0006] To achieve the above object, the present invention adopts the following technical scheme: a straw-based degradable porous matrix for plant seedling cultivation, comprising polyvinyl alcohol monomer cross-linked and solidified into a cross-linked carrier, in which straw powder, biochar powder and slow-release fertilizer are loaded.

[0007] The principle of this scheme is:

[0008] This solution prepares polyvinyl alcohol into a foamed, porous carrier material, and adds plant straw, biochar and slow-release fertilizer to the carrier material to make it more suitable for plant cultivation. Specifically, the straw in the matrix decomposes during use to produce organic matter, which provides organic nutrients for the growth and reproduction of microorganisms; and the straw slowly decomposes during use, producing a new pore structure in the matrix, which can also effectively improve the problem of blockage of the matrix material during use that affects nutrient transfer. Biochar has a well-developed pore structure and is suitable for the growth and reproduction of microorganisms, providing a physical space for the growth and reproduction of microorganisms; auxiliary materials such as straw and its decomposition products, biochar, etc. can improve the water and fertilizer retention properties of the matrix material.

[0009] The advantages of this solution are:

[0010] 1. Compared with the matrix materials in the prior art that damage plant roots and affect plant growth, the matrix materials of this scheme have better biocompatibility. Specifically, the raw materials including polyvinyl alcohol monomer cross-linked and solidified into a cross-linked carrier, straw powder, biochar powder and slow-release fertilizer are very friendly to plant roots and plant tissues, have high safety, and can also effectively provide support and nutrition for the plant seedling stage, thereby promoting the plant seedling process.

[0011] 2. This scheme uses non-toxic polyvinyl alcohol monomers to prepare cross-linked carriers, which can slowly degrade in nature, effectively reducing the risk of long-term accumulation; and the straw powder, biochar powder and slow-release fertilizer loaded in the cross-linked carriers of this scheme can all be effectively degraded, which not only effectively provides nutrition for plant seedlings, but also can improve soil water absorption, water retention and air permeability after degradation, promote plant root development, and further improve the plant seedling effect.

[0012] Preferably, as an improvement, the cross-linked carrier is prepared by uniformly mixing a raw material polyvinyl alcohol aqueous solution, a pore former, a foaming agent, a dispersing defoaming agent, a compatibility improving agent, a plasticizer and a cross-linking agent and then curing the mixture at high temperature.

[0013] Technical effect: This scheme adopts the above-mentioned setting, which is convenient for preparing a cross-linked carrier with developed pores, stable chemical structure and strength. Specifically, there is an interface effect between auxiliary materials such as straw biochar and porous polymers. In the present invention, the connection between the polymer and straw and biochar is enhanced by a compatibility improver. The applicant found in the experiment that if the compatibility improver is not added, the prepared material will have a powder falling phenomenon (straw and carbon powder falling).

[0014] Preferably, as an improvement, the following raw materials are included in parts by mass: 100 parts of polyvinyl alcohol monomer, 5-10 parts of pore former, 10-20 parts of foaming agent, 5-10 parts of dispersing defoaming agent, 5-15 parts of plasticizer, 0.5-5 parts of cross-linking agent, as well as 50-100 parts of straw powder, 10-50 parts of biochar powder, 1-10 parts of slow-release fertilizer and 0.1-2 parts of compatibility improver.

[0015] Technical effect: This scheme adopts the above-mentioned setting, which is convenient for producing and preparing porous matrix materials with high safety, high porosity, rich nutrition and easy degradation. The applicant found through long-term experiments that if the amount of foaming agent is too little, the pores of the material will be small and dense, while if the amount of foaming agent is too much, the pores of the material will be too large; if the amount of dispersing defoaming agent is too little, the material texture will be uneven, while if the amount of dispersing defoaming agent is too much, it will cause subsequent removal difficulties; if the amount of plasticizer is too little, the toughness of the matrix material will be insufficient and it will be destroyed as the plant grows; if the amount of cross-linking agent is too little, the foaming will fail due to insufficient strength of the polymer material, while if the amount of cross-linking agent is too much, the material will be uneven due to too many cross-linking points. If the amount of straw powder is too little, the growth and reproduction of microorganisms will be slow due to insufficient easily decomposable organic matter, and the matrix fertilizer retention effect will be poor. If the amount of straw powder is too much, the mechanical properties of the material will decrease due to exceeding the material loading capacity; if the amount of biochar powder is too little, the growth and reproduction of microorganisms and cation exchange sites will be insufficient, and the matrix fertilizer retention effect will be poor. If the amount of biochar powder is too much, the mechanical properties of the material will decrease due to exceeding the material loading capacity; if the amount of slow-release fertilizer is too little, the matrix fertility will be insufficient; if the amount of compatibility improver is too little, the connection between the polymer and the straw and biochar will be unstable, resulting in the falling off of straw and biochar during the use of the material.

[0016] Preferably, as an improvement, the bulk density of the matrix is ​​in the range of 0.2 to 0.7 g / cm 3 ; The moisture content of the substrate on day 7 is 42-75%.

[0017] Technical effect: This scheme adopts the above-mentioned setting to effectively enhance the promotion effect of porous matrix materials on plant seedling cultivation. Specifically, the porous matrix produced and prepared by this scheme is not only light in weight, easy to store and transport, but also has strong water absorption capacity. It belongs to medium and high density porous materials, which effectively provide water for seedlings, save water resources and improve the growth of seedlings.

[0018] Preferably, as an improvement, the pore-forming agent is starch.

[0019] Technical effect: This scheme adopts the above-mentioned setting to improve the porosity of the matrix material. Specifically, when starch is mixed with water, a gel-like substance is formed, which has good adhesion and fluidity; and during the high-temperature curing stage, starch reacts with other materials to produce gas, thereby forming pores. In addition, starch is widely available, low-cost, and degradable, which effectively reduces the production cost of porous matrices and improves production efficiency.

[0020] Preferably, as an improvement, the foaming agent is citric acid.

[0021] Technical effect: This scheme adopts the above settings to further improve the porosity of the porous matrix. Specifically, citric acid (C6H8O7) is a weak acid that can react with alkaline substances (such as sodium carbonate, sodium bicarbonate, etc.) to generate carbon dioxide gas. After the carbon dioxide is discharged, pores are formed to improve the porosity of the matrix material. In addition, citric acid is a polybasic weak organic acid and is solid at room temperature. The citric acid gas production process is mild, and the sample storage and transportation are convenient.

[0022] Preferably, as an improvement, the dispersing defoaming agent is vegetable oil.

[0023] Technical effect: This solution adopts the above-mentioned setting to facilitate the removal of foam on the surface of the material solution. Specifically, the surface activity and interfacial adsorption characteristics of vegetable oil can reduce the surface tension at the gas-liquid interface, thereby destroying the stability of the bubbles. It can also be adsorbed on the surface of the bubbles to form a thin film, hindering the merging and stability of the bubbles, causing the bubbles to burst, and achieving the effect of dispersion and defoaming. The applicant has found through long-term experiments that if the amount of vegetable oil is too much, negative effects such as greasy surface or increased viscosity will occur.

[0024] Preferably, as an improvement, the plasticizer is a phthalate plasticizer, preferably one of dimethyl phthalate and diethyl phthalate, or a mixture of the two in any proportion.

[0025] Technical effect: This scheme adopts the above-mentioned setting to improve the plasticity and strength of the porous matrix. Compared with the poor stability of degradable plasticizers at high temperatures, this scheme adopts phthalate plasticizers, which not only effectively increases the overall plasticity of the material, but also can stably exert its efficacy at high temperatures, improve the quality stability of the porous mechanism product, and facilitate its effect. Preferably, as an improvement, the cross-linking agent is polyethylene glycol with a degree of polymerization of 1000-2000.

[0026] Technical effect: This scheme adopts the above-mentioned setting, which is convenient for cross-linking to form a stable porous structure, and improves the release rate and stability of the nutrient elements in the cross-linked carrier. If glutaraldehyde is used instead of polyethylene glycol, the cross-linking reaction at high temperature will cause environmental pollution.

[0027] Preferably, as an improvement, the compatibility improver is a phthalate coupling agent.

[0028] Technical effect: This scheme adopts the above-mentioned setting, and by improving the interface compatibility, it can reduce the defects and gaps at the interface and improve the overall performance of the material. If a silane coupling agent is used instead of a phthalate coupling agent, the compatibility between the cross-linked polymer-loaded straw and biochar will decrease.

[0029] The present invention also provides a method for preparing a straw-based degradable porous matrix for growing plant seedlings, comprising the following steps:

[0030] Step 1, raw material mixing: prepare the above raw materials, prepare polyvinyl alcohol aqueous solution, add straw powder, biochar, slow-release fertilizer and compatibility improver, mix well, add pore former, dispersing defoamer, foaming agent, plasticizer to obtain foaming solution;

[0031] Step 2, porous matrix molding: adding a crosslinking agent to the foaming solution, injecting it into a mold after high-speed stirring, causing a crosslinking reaction, heating the slurry to solidify it; cooling, demolding, washing and drying to obtain a porous matrix.

[0032] Technical effect: This scheme adopts the above settings to facilitate the preparation of a porous mechanism with rich nutrition, well-developed pores, stable chemical structure and strength.

[0033] Preferably, as an improvement, the concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 5-10%.

[0034] Technical effect: This scheme adopts the above settings, which is convenient.

[0035] Preferably, as an improvement, in step 2, the curing conditions are: react at 50-100°C for 0.5-1h, then react at 100-150°C for 1-5min, and finally keep warm at 80°C until completely cured.

[0036] Technical effect: This scheme adopts the above-mentioned setting, which is convenient for curing the slurry obtained by mixing and cross-linking multiple raw materials into a porous material. Specifically, the temperature in the first stage facilitates further cross-linking of the raw materials to form a preliminary three-dimensional network structure; and the three-dimensional network structure after cross-linking is heated to 100-150°C to form a denser and stable cross-linked network, thereby improving the mechanical properties and heat resistance of the material. The 80°C in the third stage not only effectively ensures that these incompletely reacted cross-linking agents continue to react, making the cross-linked network more perfect; it can also reduce the thermal stress caused by rapid cooling, contribute to the uniform distribution of the cross-linked network, reduce local defects and unevenness, and reduce the thermal stress caused by rapid cooling; furthermore, low-temperature insulation helps to remove residual moisture in the material, further improve the dryness and stability of the material, and further improve the mechanical properties and durability of the material, which is suitable for applications requiring long-term stability.

[0037] Preferably, as an improvement, in step 2, the stirring speed is 500-1500 rpm.

[0038] Technical effect: This solution adopts the above settings to facilitate the thorough mixing of the raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1The straw-based degradable plant seedling cultivation porous matrix prepared in an embodiment of the present invention (left picture: high biochar content, such as 50 parts; right picture: low biochar content, such as 10 parts). DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following examples and experimental examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used can be obtained from commercial sources.

[0041] Program Overview

[0042] The present invention provides a straw-based degradable porous matrix for plant seedling cultivation, comprising a cross-linked carrier formed by cross-linking and curing polyvinyl alcohol monomers, and the cross-linked carrier is loaded with straw powder, biochar powder and slow-release fertilizer. The cross-linked carrier is formed by mixing raw polyvinyl alcohol aqueous solution, pore-forming agent, foaming agent, dispersing defoaming agent, compatibility improving agent, plasticizer and cross-linking agent and curing them by heating.

[0043] The porous matrix of this scheme includes the following raw materials in parts by weight: 100 parts of polyvinyl alcohol monomer, 5-10 parts of pore former, 10-20 parts of foaming agent, 5-10 parts of dispersing defoaming agent, 5-15 parts of plasticizer, 0.5-5 parts of cross-linking agent, 50-100 parts of straw powder, 10-50 parts of biochar powder, 1-10 parts of slow-release fertilizer and 0.1-2 parts of compatibility improver.

[0044] As a reference, the pore-forming agent is starch, the foaming agent is citric acid, the dispersing and defoaming agent is vegetable oil, the compatibility improver is a phthalate coupling agent, the plasticizer is a phthalate plasticizer, preferably one of dimethyl phthalate and diethyl phthalate or a mixture of both in any proportion, the cross-linking agent is polyethylene glycol with a degree of polymerization of 1000-2000, and the compatibility improver is a phthalate coupling agent.

[0045] As a reference, the bulk density of the porous matrix of this scheme ranges from 0.2 to 0.7 g / cm3; the moisture content of the matrix after 7 days is 42 to 75%.

[0046] The present invention also provides a method for preparing a straw-based degradable porous matrix for growing plant seedlings, comprising the following steps:

[0047] Step 1, raw material mixing: prepare the above raw materials, prepare a polyvinyl alcohol aqueous solution with a concentration of 5-10%, add straw powder, biochar, slow-release fertilizer and compatibility improver, mix well, add pore former, dispersing defoamer, foaming agent, plasticizer to obtain a foaming solution;

[0048] Step 2, porous matrix molding: add a crosslinking agent to the above foaming solution, stir at a speed of 500-1500 rpm and then inject into a mold to cause a crosslinking reaction, heat the slurry to solidify it; cool, demould, rinse and dry to obtain a porous matrix.

[0049] As a reference, the curing conditions are: react at 50-100°C for 0.5-1h, then react at 100-150°C for 1-5min, and finally keep warm at 80°C until completely cured.

[0050] The present solution also provides an application of a straw-based degradable plant seedling cultivation porous matrix in plant seedling cultivation, including using the porous matrix in the seedling cultivation stage and the seedling stage to assist plant germination or growth.

[0051] Example 1

[0052] A straw-based degradable porous matrix for growing plant seedlings, the raw materials comprising: 100 parts of polyvinyl alcohol monomer, 5 parts of pore-forming agent starch, 10 parts of citric acid as a foaming agent, 5 parts of vegetable oil as a dispersant and defoamer, 10 parts of dimethyl phthalate as a plasticizer, 1 part of polyethylene glycol with a polymerization degree of 1000 as a cross-linking agent, 50 parts of straw powder, 50 parts of biochar powder, 2 parts of slow-release fertilizer and 0.1 part of a phthalate coupling agent as a compatibility improver;

[0053] The steps include: preparing a 5% polyvinyl alcohol aqueous solution, adding auxiliary materials such as straw powder with a diameter of 0.2-2mm, biochar, slow-release fertilizer, and a compatibility improver, and mixing them evenly; adding a pore former, a dispersant, a defoamer, a foaming agent, and a plasticizer to the above to obtain a foaming solution, and mixing it evenly; adding a crosslinking agent to the above system, injecting it into a mold after high-speed stirring, and causing a crosslinking reaction; reacting the slurry at 80°C for 0.5 hour, reacting at 120°C for 2 minutes, and keeping it at 80°C until it is completely solidified; cooling, demolding, rinsing and drying to obtain a porous matrix.

[0054] The matrix prepared in this example has a bulk density of 0.46 g / cm3, a porosity of 62%, and a water absorption rate of 650%.

[0055] Example 2

[0056] A straw-based degradable porous matrix for growing plant seedlings, the raw materials comprising: 100 parts of polyvinyl alcohol monomer, 10 parts of pore-forming agent starch, 15 parts of foaming agent citric acid, 5 parts of dispersant and defoaming agent vegetable oil, 10 parts of plasticizer diethyl phthalate, 2 parts of cross-linking agent polyethylene glycol with a polymerization degree of 1200, 40 parts of straw powder, 20 parts of biochar powder, 1 part of slow-release fertilizer and 1 part of compatibility improver phthalate coupling agent;

[0057] The steps include: preparing an 8% polyvinyl alcohol aqueous solution, adding auxiliary materials such as straw powder with a diameter of 0.2-2mm, biochar, slow-release fertilizer, and a compatibility improver, and mixing them evenly; adding a pore former, a dispersant, a defoamer, a foaming agent, and a plasticizer to the above to obtain a foaming solution, and mixing it evenly; adding a crosslinking agent to the above system, injecting it into a mold after high-speed stirring, and causing a crosslinking reaction; reacting the slurry at 80°C for 0.5 hour, reacting at 120°C for 2 minutes, and keeping it warm at 80°C until it is completely solidified; cooling, demolding, rinsing and drying to obtain a porous matrix.

[0058] The matrix prepared in this example has a bulk density of 0.38 g / cm3, a porosity of 71%, and a water absorption rate of 920%.

[0059] Example 3

[0060] A straw-based degradable porous matrix for growing seedlings of plants, the raw materials of which include: 100 parts of polyvinyl alcohol monomer, 8 parts of pore-forming agent starch, 20 parts of citric acid as a foaming agent, 10 parts of vegetable oil as a dispersant and defoamer, 15 parts of a plasticizer (a mixture of dimethyl phthalate and diethyl phthalate of equal weight), 5 parts of polyethylene glycol with a cross-linking agent polymerization degree of 2000, 100 parts of straw powder, 20 parts of biochar powder, 10 parts of slow-release fertilizer and 2 parts of a compatibility improving agent phthalate coupling agent;

[0061] The steps include: preparing a 10% polyvinyl alcohol aqueous solution, adding auxiliary materials such as straw powder with a diameter of 0.2-2mm, biochar, slow-release fertilizer, and a compatibility improver, and mixing them evenly; adding a pore former, a dispersant, a defoamer, a foaming agent, and a plasticizer to the above to obtain a foaming solution, and mixing it evenly; adding a crosslinking agent to the above system, injecting it into a mold after high-speed stirring, and causing a crosslinking reaction; reacting the slurry at 80°C for 0.5 hour, reacting at 120°C for 2 minutes, and keeping it warm at 80°C until it is completely solidified; cooling, demolding, rinsing and drying to obtain a porous matrix.

[0062] The matrix prepared in this example has a bulk density of 0.31 g / cm 3 , porosity 84.6%, water absorption 630%.

[0063] Comparative Example 1

[0064] This comparative example is basically the same as Example 3, except that no straw powder is added.

[0065] The matrix obtained in this comparative example has a bulk density of 0.18 g / cm 3 , porosity 92.2%, water absorption 1270%.

[0066] Comparative Example 2

[0067] This comparative example is basically the same as Example 3, except that no biochar powder is added.

[0068] Comparative Example 3

[0069] This comparative example is basically the same as Example 3, except that no compatibility improver is added.

[0070] Comparative Example 4

[0071] This comparative example is basically the same as Example 3, except that 5 parts of citric acid are used.

[0072] Experimental Example 1: Matrix Performance

[0073] The matrix block bulk density, porosity and water and fertilizer retention performance of the porous matrix obtained in accordance with the reference standards GB / T6343-2009 Determination of apparent density of foam plastics and rubber, GB / T10799-2008 Determination of volume percentage of open and closed cells of rigid foam plastics, and GB / T23348-2009 Slow-release fertilizer detection Example 3 and Comparative Examples 1-4 are shown in Table 1 for details.

[0074] Table 1 Comparison of the properties of the porous substrates obtained in Example 1 and Comparative Examples 1 to 3

[0075] Group <![CDATA[Bulk density (density) / g / cm 3 > Porosity / % Seven-day moisture content / % 28-day nutrient release rate / % Example 3 0.31 84.6 74.5 53.5 Comparative Example 1 0.18 92.2 48.1 71.2 Comparative Example 2 0.25 86.8 60.4 66.4 Comparative Example 3 0.30 84.1 70.9 60.5 Comparative Example 4 0.62 51.5 23.6 38.1

[0076] Experimental data show that the bulk density range of the matrix is: 0.2-0.7g / cm3; the moisture content of the matrix can be controlled at 42-75% on the 7th day, which is particularly suitable for factory-based seedling cultivation and plant production. If straw powder is lacking (such as comparative example 1), not only will the bulk density of the porous medium be significantly reduced, but the moisture content of the matrix will also be reduced and the nutrient release will be accelerated due to the reduction of fiber in the material, and the growth of the plant in the later stage cannot be supported. If biochar powder is lacking (such as comparative example 2), the moisture content of the porous matrix will be mainly reduced, thereby reducing the utilization rate of water resources and increasing costs; the growth of plants will also be affected due to the excessive release of nutrients. If a compatibility improver is lacking (such as comparative example 3), the unstable connection between the polymer and the straw and biochar will cause the straw and biochar to fall off during the use of the material, thereby reducing its overall performance. If there is too little foaming agent (such as comparative example 4), the moisture content and nutrient release effect of the matrix material will be affected due to the small number of pores in the matrix material, thereby slowing down the growth of plants.

[0077] Experimental Example 2: Application of substrate seedling cultivation

[0078] The leafy vegetable Shanghai Qing was used as the test sample and cultivated in the substrates of Example 1 and Comparative Examples 1, 2, 3, 4 and the control group (rock wool) for 50 days. The growth conditions of the cultivated plants are shown in Table 2.

[0079] Table 2 Comparison of seedling raising effects of porous substrates obtained in Example 1 and Comparative Examples 1 to 3

[0080] Group Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Control group Fresh weight / g 135.3±7.7 104.5±5.9 117.8±9.4 121.4±4.8 82.2±11.4 94.2±11.5

[0081] Experimental data show that the matrix produced by this scheme effectively improves plant growth. Specifically, the lack of any of the three straw powder, biochar powder, and compatibility improver will greatly reduce the effect of the porous matrix on plant growth. In addition, if the foaming agent citric acid is too little, it will also significantly weaken the growth of plants. The applicant analyzed that the reason is that if the foaming agent is too little, the porosity of the porous matrix will be reduced due to the low porosity, which will affect its water content and nutrient release effect, and ultimately affect the growth of plants.

[0082] In summary, the present invention can adjust the void structure of the matrix material by adjusting the ratio of pore former (starch), foaming agent (citric acid) and cross-linking agent (polyethylene glycol) during the polymerization of polyvinyl alcohol monomer. In addition, the mechanical strength, water and fertilizer retention performance and microbial habitat of the flexible matrix can be adjusted by adjusting the ratio of straw to biochar to meet the growth needs of different plants and different growth periods. In addition, a compatibility improver is added to the present invention to reduce the interface effect between straw, biochar and porous materials, and increase the stability of straw and biochar in the matrix. After this solution is used for factory-based seedling cultivation and plant growth, the growth of plants is effectively improved and the production efficiency is improved.

[0083] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A straw-based degradable porous substrate for growing plant seedlings, characterized in that: The method comprises the steps of polymerizing polyvinyl alcohol monomers and cross-linking and solidifying them into a porous polymer carrier, wherein the porous polymer carrier is loaded with straw powder, biochar powder and slow-release fertilizer.

2. The straw-based degradable porous matrix for growing plant seedlings according to claim 1, characterized in that: The porous polymer carrier is prepared by uniformly mixing raw material polyvinyl alcohol aqueous solution, pore-forming agent, foaming agent, dispersing defoaming agent, compatibility improving agent, plasticizer and cross-linking agent, and then heating and curing.

3. The straw-based degradable porous matrix for growing plant seedlings according to claim 2, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of polyvinyl alcohol monomer, 5-10 parts of pore former, 10-20 parts of foaming agent, 5-10 parts of dispersing defoaming agent, 5-15 parts of plasticizer, 0.5-5 parts of cross-linking agent, 50-100 parts of straw powder, 10-50 parts of biochar powder, 1-10 parts of slow-release fertilizer and 0.1-2 parts of compatibility improver.

4. The straw-based degradable porous matrix for growing plant seedlings according to claim 3, characterized in that: The bulk density of the matrix is ​​in the range of 0.2 to 0.7 g / cm 3 ; The moisture content of the substrate on day 7 is 42-75%.

5. The straw-based degradable porous substrate for growing plant seedlings according to claim 3, characterized in that: The pore-forming agent is starch, the foaming agent is citric acid, the dispersing and defoaming agent is vegetable oil, and the compatibility improving agent is a phthalate coupling agent.

6. The straw-based degradable porous substrate for growing plant seedlings according to claim 5, characterized in that: The plasticizer is a phthalate plasticizer, preferably one of dimethyl phthalate and diethyl phthalate, or a mixture of the two in any proportion.

7. The straw-based degradable porous substrate for growing plant seedlings according to claim 6, characterized in that: The cross-linking agent is polyethylene glycol with a polymerization degree of 1000-2000, and the compatibility improving agent is a phthalate coupling agent.

8. A method for preparing a straw-based degradable porous matrix for growing plant seedlings, characterized in that: The steps include: Step 1, mixing raw materials: preparing the raw materials in any one of claims 1 to 8, preparing a polyvinyl alcohol aqueous solution, adding straw powder, biochar, slow-release fertilizer and compatibility improver, mixing and adding a pore former, a dispersing defoamer, a foaming agent and a plasticizer to obtain a foaming solution; Step 2, porous matrix molding: adding a crosslinking agent to the foaming solution, injecting it into a mold after high-speed stirring, causing a crosslinking reaction, heating the slurry to solidify it; cooling, demolding, washing and drying to obtain a porous matrix.

9. The method for preparing a straw-based degradable porous matrix for growing plant seedlings according to claim 8, characterized in that: The polyvinyl alcohol concentration in the polyvinyl alcohol aqueous solution is 5-10%.

10. The method for preparing a straw-based degradable porous matrix for growing plant seedlings according to claim 8, characterized in that: In step 2, the curing conditions are: react at 50-100° C. for 0.5-1 h, then react at 100-150° C. for 1-5 min, and finally keep warm at 80° C. until completely cured; the stirring speed is 500-1500 rpm.

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