Method for manufacturing an agricultural substrate

Abstract

The application relates to a method for preparing an agricultural substrate, which comprises the following steps: taking branch powder, mushroom stick (residue) powder or poultry manure, bran and nitrogen-containing wastewater as initial materials; taking part of the initial materials to carry out short-time anaerobic fermentation, so that the initial materials are hydrolyzed and acidified to obtain acidified materials with a pH value of 4.5-5.5; mixing the acidified materials, the remaining initial materials, modified biochar and a decomposition accelerating agent to carry out aerobic composting fermentation, so that the agricultural substrate is obtained; and adding nano-iron-chitosan modified biochar or nano-iron-carboxymethyl cellulose modified biochar into the composting, so that the cytotoxicity of nano-iron to the composting microorganisms is reduced, the metabolic activity of the microorganisms is improved, and the soil or the cultivation environment is improved; the addition of the acidified materials solves the problem of the increase of the pH value of the aerobic composting materials caused by the addition of the strong alkaline biochar, without adding other exogenous pH regulators, the preparation cost of the agricultural substrate is reduced, and the composting process is accelerated.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of agricultural substrates, and particularly relates to a preparation method of an agricultural substrate. BACKGROUND

[0002] The agricultural substrate is a material basis for realizing the industrialization of modern agricultural cultivation and developing efficient modern agriculture. The main raw materials of the existing agricultural substrate include gravel, rock wool, slag, sponge, peat, rice husk, mushroom residue, and vermiculite.

[0003] During the preparation of the agricultural substrate, the organic raw material is subjected to aerobic composting fermentation to obtain a mature product, and biochar is added to the compost as a maturation accelerator. However, since the biochar is strongly alkaline (the pH value is usually greater than 10), the addition of the biochar will cause the increase of the acid-base degree of the compost material, and thus affect the quality of the agricultural substrate.

[0004] Nano-iron, also known as zero-valent nano-iron, refers to a nano material with at least one dimension in the range of 1-100 nm and zero-valent iron as the main component, which has the characteristics of magnetism, small volume, large specific surface area, high reaction activity, and non-toxic and harmless reaction products. Its unique "core-shell" nano structure has multiple pollutant action mechanisms such as adsorption, oxidation / reduction, and precipitation, and has been proven to be able to efficiently remove dozens of environmental pollutants in water, including heavy metals (such as copper, arsenic, lead, zinc, nickel, cobalt, chromium, cadmium, mercury, silver, etc.), non-metallic inorganic substances (such as nitrate, nitrite, phosphate, perchlorate, etc.), halogenated organic substances (such as trichloroethylene, polychlorinated biphenyl, bromomethane, etc.), nitrogen-containing organic substances (such as azo dyes, nitroaromatic compounds, etc.), radioactive substances (such as uranium, technetium, etc.), and pesticides.

[0005] Zero-valent nano-iron has strong adsorption and can reduce carbon and nitrogen loss and improve the nutrient content of the compost product when used in composting. However, since zero-valent nano-iron has a certain cytotoxicity to the microorganisms in the compost, it will affect the metabolism of the microorganisms and is not conducive to the fermentation of the compost, so it is rarely used in agricultural substrates. SUMMARY

[0006] Therefore, the purpose of the present application is to provide a preparation method of an agricultural substrate, which can produce an agricultural substrate with good quality.

[0007] The technical solution adopted by the present application to solve the technical problems is as follows:

[0008] A preparation method of an agricultural substrate, comprising the following steps:

[0009] (1) Bioacidification: A predetermined proportion of mushroom stem (residue) powder or poultry manure, bran, nitrogen-containing wastewater is added to the branch powder to prepare an initial material with a carbon-nitrogen ratio of 29-32:1. Part of the initial material is sealed for fermentation, allowing the initial material to hydrolyze and acidify under anaerobic conditions. The initial material has a moisture content of 90-94%, the acidification temperature is 15-35°C, the sealed fermentation time is 4-8 days, and the acidified material has a pH of 4.5-5.5.

[0010] (2) Aerobic composting fermentation: The acidified material prepared in step (1) is mixed with the remaining initial material, modified biochar, and a maturation accelerator to form a composting material. The composting material has a carbon-nitrogen ratio of 25-30:1 and a moisture content of 60-70%. The initial temperature is 30-55°C, and the composting fermentation time is 21-28 days. The final composting fermentation produces the agricultural substrate. The modified biochar is nano-iron-chitosan modified biochar or nano-iron-carboxymethyl cellulose modified biochar. The nano-iron-chitosan modified biochar or nano-iron-carboxymethyl cellulose modified biochar promotes the metabolic activity of composting microorganisms, allowing the composting material to rapidly mature and accelerating the composting process.

[0011] Preferably, in step (1), the mass ratio of branch powder to mushroom stem (residue) powder is 11-22:1, the bran accounts for 1-2% of the total mass of branch powder and mushroom stem (residue) powder, and the nitrogen-containing wastewater is 15-20 times the total mass of branch powder and mushroom stem (residue) powder.

[0012] Preferably, in step (1), the mass ratio of branch powder to poultry manure is 1:1-5, the bran accounts for 1-2% of the total mass of branch powder and poultry manure, and the nitrogen-containing wastewater is 2.5-5 times the total mass of branch powder and poultry manure.

[0013] Preferably, in step (1), the nitrogen-containing wastewater is one of yellow slurry water, manure water, or nitrogen-containing liquid.

[0014] Preferably, in step (1), the initial material has a carbon-nitrogen ratio of 31:1, a moisture content of 92%, an acidification temperature of 35°C, and an acidification time of 4 days. In step (2), the composting material has a carbon-nitrogen ratio of 25:1, a moisture content of 60%, an initial temperature of 30°C, and a composting time of 21 days.

[0015] Preferably, in step (2), the modified biochar accounts for 1-3% of the total mass of the composting material, and the maturation accelerator is a mixture of a bacterial agent and an enzyme preparation. The bacterial agent accounts for 0.5-1% of the total mass of the composting material, and the enzyme preparation accounts for 0.5-1% of the total mass of the composting material.

[0016] Preferably, in step (2), the preparation process of the nano-iron-chitosan modified biochar or nano-iron-carboxymethyl cellulose modified biochar is as follows:

[0017] (1) The branch is crushed to a particle size of 0.5 mm, heated under nitrogen at 400-500°C with a heating rate of 5-10°C / min, and pyrolysis time of 20-24 hours to obtain biochar;

[0018] (2) Chitosan or carboxymethyl cellulose sodium is dissolved in deionized water at a mass / volume ratio (m / v) of 1:25 to prepare a 40 g / L chitosan solution or carboxymethyl cellulose sodium solution;

[0019] (3) Zero-valent iron powder is added to NaOH solution and stirred until the zero-valent iron is completely dissolved to prepare a 20 g / L zero-valent iron solution;

[0020] (4) The zero-valent iron solution is mixed with the chitosan solution or carboxymethyl cellulose sodium solution at a volume ratio of 1:2.5 to obtain a mixed solution, and biochar is added to the mixed solution, which should be added slowly and stirred during the process. The mass ratio of the mixed solution to the biochar is 4.5:1;

[0021] (5) The mixture is sequentially subjected to ultrasonic treatment for 30 min, constant temperature oscillation for 2 hours, vacuum filtration and drying, and the dried material is placed in a vacuum furnace and heated at 700°C under nitrogen for 2 hours, then cooled to room temperature under nitrogen and kept for another 2 hours. The modified biochar is sequentially washed with clean water and deionized water until the pH value is neutral, and then dried in an oven for standby use.

[0022] Compared with the prior art, the application has the beneficial effects that: (1) by adding nano-iron-chitosan modified biochar or nano-iron-carboxymethyl cellulose modified biochar during composting, the cytotoxicity of nano-iron to the compost microorganisms is effectively reduced, so that the metabolic activity of the compost microorganisms is improved, the compost fermentation is facilitated, and the nano-iron-chitosan modified biochar or the nano-iron-carboxymethyl cellulose modified biochar has more adsorption sites than the biochar alone, so that the adsorption of volatile gases such as ammonia and volatile organic acids is improved, the material is quickly composted, the carbon and nitrogen loss of the compost is reduced, the composting process is accelerated, and the quality of the compost product is improved; on the other hand, the agricultural substrate containing the nano-iron-chitosan modified biochar or the nano-iron-carboxymethyl cellulose modified biochar is applied to the soil or used for crop cultivation, so that the soil or the cultivation environment is regulated, the plant root growth environment is improved, and the crop growth is facilitated; (2) by adding acidizing materials during composting, the problem of the increase of the pH value of the aerobic compost material caused by the addition of the strong alkaline biochar is well solved, no other exogenous pH regulator needs to be added, the production cost of the agricultural substrate is reduced, and the composting process has the advantages of fast temperature rise, high temperature peak in the high temperature period, fast composting, high composting degree and the like, the composting process is accelerated, and the high temperature generated during the composting of the material can be directly used to kill bacteria, insect eggs and the like in the raw material; the method is economical and environmentally friendly, convenient for factory production, and the agricultural substrate prepared has good quality. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the influence of different temperatures on the pH value of the acidizing material.

[0024] Figure 2 is the influence of different additives on the composting temperature. DETAILED DESCRIPTION

[0025] The technical solutions and technical effects of the embodiments of the application are further described in detail.

[0026] The application provides a method for preparing an agricultural substrate, which comprises the following steps:

[0027] (1) biological acidification: a predetermined proportion of mushroom stick (residue) powder or poultry manure, bran and nitrogen-containing wastewater is added to the branch powder to prepare initial material with a carbon-nitrogen ratio of 29-32:1, part of the initial material is sealed for fermentation, the initial material is hydrolyzed and acidified under anaerobic conditions, the water content of the initial material is 90%-94%, the acidification temperature is 15-35 DEG C, the sealed fermentation time is 4-8 days, and the acidification ends to obtain acidizing material with a pH value of 4.5-5.5;

[0028] (2) aerobic composting fermentation: the acidified material prepared in step (1) is mixed with the remaining initial material, modified biochar and composting accelerator to form a composting material, and the composting material is subjected to aerobic composting fermentation, wherein the carbon-nitrogen ratio of the composting material is 25-30:1, the water content is 60%-70%, the initial temperature is 30-55 DEG C, the composting fermentation time is 21-28 days, and the composting fermentation is completed to obtain the agricultural substrate; wherein the modified biochar is nano-iron-chitosan modified biochar or nano-iron-carboxymethyl cellulose modified biochar, and the nano-iron-chitosan modified biochar or nano-iron-carboxymethyl cellulose modified biochar is used to promote the metabolic activity of composting microorganisms, so that the material is rapidly composted, thereby accelerating the composting process.

[0029] In the prior art, when zero-valent nano-iron is used for composting, its strong adsorption property can reduce carbon and nitrogen loss and improve the nutrient content of composting products. However, excessive intake of divalent iron (Fe(II)) by cells can cause cell oxidative damage, i.e. through the redox reaction of iron and the generation of active oxygen in the body, which can cause cell aging, cell death and acute poisoning. Therefore, zero-valent nano-iron has a certain cytotoxicity to composting microorganisms, which is not conducive to composting fermentation. Chitosan and carboxymethyl cellulose are natural cationic polymers, which have excellent biodegradability and biocompatibility, and also have important biological activity, such as free radical scavenging. When chitosan and carboxymethyl cellulose are used as free radical scavengers, they can compete with bacteria for oxidants, reduce the generation of hydroxyl radicals, and thus reduce the cytotoxicity of nano-iron. Therefore, chitosan or carboxymethyl cellulose can be used to modify nano-iron to reduce the cytotoxicity of nano-iron to composting microorganisms. Nano-iron-chitosan or nano-iron-carboxymethyl cellulose obtained after modification can be used to modify biochar, which can increase the adsorption sites on the surface of biochar to improve the composting structure through chelation. In the present application, nano-iron-chitosan modified biochar or nano-iron-carboxymethyl cellulose modified biochar is added during composting to reduce the cytotoxicity of nano-iron alone to composting microorganisms, which is conducive to improving the metabolic activity of composting microorganisms. Compared with biochar alone, nano-iron-chitosan modified biochar or nano-iron-carboxymethyl cellulose modified biochar has more adsorption sites, which improves its adsorption of volatile gases such as ammonia and volatile organic acids, so that the material is rapidly composted, the carbon and nitrogen loss during composting is reduced, the composting process is accelerated, and the quality of the composting product is improved. On the other hand, the agricultural substrate containing nano-iron-chitosan modified biochar or nano-iron-carboxymethyl cellulose modified biochar can be applied to soil or used for crop cultivation, which can regulate the soil or cultivation environment, improve the growth environment of plant roots, and thus promote crop growth.

[0030] Further, since the biochar is a strong alkaline substance, adding the biochar will cause the pH of the compost material to increase. Therefore, in the present application, by subjecting the initial material to biological acidification treatment, i.e. through microbial hydrolysis and acidification, the material generates a large amount of small molecule fatty acids such as acetic acid, butyric acid, propionic acid, isobutyric acid, etc., to generate acidic acidified material; by adding the acidified material to the compost, the problem of increased pH of the aerobic compost material caused by the addition of alkaline biochar can be better improved, without the need to add other exogenous pH conditioners, reducing the production cost of the agricultural substrate; and the addition of the acidified material makes the composting process have the advantages of fast temperature rise, high temperature peak in the high temperature period, rapid composting, high composting degree, etc., speeding up the composting process, and the high temperature generated during the stacking of the compost material can be directly used to kill bacteria, insect eggs, etc. in the raw material. The method is economical, environmentally friendly and convenient for factory production, and the agricultural substrate produced has good quality.

[0031] Specifically, in step (1), the mass ratio of the branch powder to the mushroom stick (residue) powder is 11-22:1, the bran accounts for 1-2% of the total mass of the branch powder and the mushroom stick (residue) powder, the modified biochar accounts for 1-3% of the total mass of the branch powder and the mushroom stick (residue) powder, and the nitrogen-containing wastewater is 15-20 times the total mass of the branch powder and the mushroom stick (residue) powder.

[0032] Specifically, in step (1), the mass ratio of the branch powder to the poultry manure is 1:1-5, the bran accounts for 1-2% of the total mass of the branch powder and the poultry manure, the modified biochar accounts for 1-3% of the total mass of the branch powder and the poultry manure, and the nitrogen-containing wastewater is 2.5-5 times the total mass of the branch powder and the poultry manure.

[0033] Specifically, in step (1), the carbon-nitrogen ratio of the initial material is 31:1, the water content is 92%, the acidification temperature is 35℃, and the acidification time is 4 days; in step (2), the carbon-nitrogen ratio of the compost material is 25:1, the water content is 60%, the initial temperature is 30℃, and the composting time is 21 days.

[0034] Specifically, in step (2), the modified biochar accounts for 1-3% of the total mass of the compost material, and the composting accelerator is a mixture of a microbial agent and an enzyme preparation, wherein the microbial agent accounts for 0.5-1% of the total mass of the compost material, and the enzyme preparation accounts for 0.5-1% of the total mass of the compost material.

[0035] Specifically, the nitrogen-containing wastewater is one of yellow slurry water, fecal water, or nitrogen-containing liquid.

[0036] Specifically, the preparation process of the nano-iron-chitosan modified biochar or the nano-iron-carboxymethyl cellulose modified biochar is as follows:

[0037] (1) Crush the branches to a particle size of 0.5 mm, heat them at 400-500℃ under nitrogen atmosphere, at a heating rate of 5-10℃ / min, and at a pyrolysis time of 20-24 hours to obtain biochar;

[0038] (2) Dissolve chitosan or sodium carboxymethyl cellulose in deionized water at a mass / volume ratio (m / v) of 1:25 to ensure complete dissolution and prepare a 40 g / L chitosan solution or sodium carboxymethyl cellulose solution.

[0039] (3) Add zero-valent iron powder to NaOH solution and stir until the zero-valent iron is completely dissolved to prepare a 20 g / L zero-valent iron solution;

[0040] (4) Mix the zero-valent iron solution with the chitosan solution or the sodium carboxymethyl cellulose solution at a volume ratio of 1:2.5 to obtain a mixture. Add biochar to the mixture slowly and while stirring. The mass ratio of the mixture to the biochar is 4.5:1.

[0041] (5) The mixture was subjected to ultrasonic treatment for 30 minutes, constant temperature oscillation for 2 hours, vacuum filtration and drying. The dried material was placed in a vacuum furnace and heated at 700°C for 2 hours under nitrogen conditions. It was then cooled to room temperature under nitrogen conditions and kept for 2 hours to obtain modified biochar. The modified biochar was washed with water and deionized water until the pH value was neutral. It was then placed in an oven to dry for later use.

[0042] The present invention will now be described in detail with reference to the embodiments.

[0043] In the following examples, the poultry and livestock manure used is cow manure, and the nitrogen-containing wastewater is yellow slurry. The physicochemical properties of each component of the biological material are shown in Table 1.

[0044] Table 1 Basic Properties of Fermentation Materials

[0045]

[0046] The microbial agent contains microorganisms that promote the degradation of fibrous materials, such as cellulose-degrading bacteria and lignin-degrading bacteria.

[0047] The enzyme preparation contains cellulase, laccase, pectinase, and other enzymes that promote the degradation of waste.

[0048] 1. Preparation of acidified materials

[0049] The branch powder, mushroom stick (residue) powder, bran, and yellow slurry water were mixed as acid production raw materials, so that the carbon-nitrogen ratio was 22:1, 25:1, 28:1, 31:1, and 34:1, respectively. The acid production raw materials were loaded into airtight fermentation bottles, so that the water content of the acid production raw materials reached 92%, and the bottles were sealed with sealing film to prevent air leakage. The fermentation bottles were placed in a thermostat at 15°C, 25°C, and 35°C, respectively, for anaerobic fermentation. Each treatment had three replicates. Samples were taken every 24 hours, and the pH value of the fermentation liquor was detected to draw the pH value dynamic change curve of the fermentation liquor, so as to determine the optimal carbon-nitrogen ratio and environmental temperature condition.

[0050] The results are shown in Figure 1 The pH value of the material in each treatment showed a change rule of rapid decrease and then slow increase with the anaerobic fermentation time. The carbon-nitrogen ratio of the material was related to the change of the pH value of the material, and there was an optimal carbon-nitrogen ratio of 31:1. Higher or lower than the optimal carbon-nitrogen ratio was not conducive to the acidification of the material. Within the test range, the pH value decrease rate of the material was proportional to the temperature, that is, the higher the temperature, the faster the pH value of the material decreased. When the carbon-nitrogen ratio was 31:1, the acidification peak values reached in the 15°C, 25°C, and 35°C treatment groups were 5.40, 5.29, and 5.12, respectively, and the required anaerobic fermentation times were 8, 6, and 4 days, respectively. In summary, when the carbon-nitrogen ratio of the organic waste was 31:1, the acidification temperature was 35°C, and the acidification time was 4 days, the acid-base value of the prepared acidified material was the lowest. In practical production, the material properties and environmental conditions can be adjusted, such as in early winter or spring, when the environmental temperature is relatively low, and the acidification device is not heated, the material acidification time can be extended until the pH value of the material reaches the minimum level.

[0051] 2. Effect of acidified material and modified biochar on composting

[0052] The branch powder was mixed with the mushroom stick (residue) powder and the acidified material, and the acidified material and modified biochar prepared under the optimal conditions were added, and the carbon-nitrogen ratio of the compost material was adjusted to 25:1 to obtain compost material with a water content of 60%. The effect of the acidified material and modified biochar on composting was studied. The initial material without adding acidified material and modified biochar was used as a control group. The test was set as shown in Table 2.

[0053] Table 2 Test design

[0054]

[0055] Referring to Figure 2The results of the effect of different additives on the temperature of the compost showed that, compared with the unmodified biochar (T1), the addition of the modified biochar (T2) made the compost material enter the high-temperature period 4 days earlier, and the peak value of the compost temperature increased by 0.5℃. Compared with the addition of the modified biochar (T2) or the acidified material (T3) alone, when the modified biochar and the acidified material were added together (T4), the compost entered the high-temperature period on the second day, and the temperature reached 65.2℃, which was 4.6℃ and 7.8℃ higher than that of T2 and T3, respectively. During the composting process, the peak value of the compost temperature of T4 was 67.2℃, which was 0.5-1.2℃ higher than that of the other treatments (T1-T3). This indicated that the modified biochar and the acidified material had a synergistic effect, which promoted the increase of the compost temperature and thus helped to speed up the composting process.

[0056] Referring to Table 3, the pH value, electrical conductivity, total nitrogen and total carbon during the composting process were detected. The results showed that, at the end of the composting, the pH value of the compost of T4 was the lowest, which was 8.15, and was 0.85%-2.86% lower than that of the other treatments. When the modified biochar was not added (T1), the electrical conductivity of the compost product only decreased by 0.74%, while after the addition of the modified biochar (T2), the electrical conductivity of the compost product decreased by 4.55%, and after the addition of the modified biochar, the acidified material and the composting accelerator together (T4), the electrical conductivity of the compost product decreased by 17.64%. The measurement of the electrical conductivity can reflect the salt content, and the above results showed that, under the synergistic effect of the modified biochar, the acidified material and the composting accelerator, the salt content of the compost product was significantly reduced, which was conducive to reducing the risk of salt damage caused by the application of organic fertilizer. When the modified biochar was not added (T1), the carbon and nitrogen losses of the compost were 56.71% and 28.63%, respectively. After the addition of the modified biochar (T2), the carbon and nitrogen losses of the compost decreased to 48.14% and 29.44%, respectively. This indicated that the addition of the modified biochar promoted the material conversion of the compost and reduced the carbon and nitrogen losses. When the modified biochar and the acidified material were added together (T4), the carbon and nitrogen losses of the compost were the least, which were 45.54% and 21.34%, respectively.

[0057] Table 3 Composting parameters

[0058]

[0059] Referring to Table 4, the available nutrients of the compost product at the end of composting were detected. Compared with T1, the addition of modified biochar (T2) increased the available nitrogen, available phosphorus and available potassium contents of the compost product by 8.06%, 6.15% and 9.50%, respectively. After the addition of modified biochar, acidified material and composting accelerator (T4), the available nitrogen content was higher than that of other treatments (T1-T3) by 4.52%-20.06%, the available phosphorus content was higher than that of other treatments (T1-T3) by 2.18%-30.63%, and the available potassium content was higher than that of other treatments (T1-T3) by 4.89%-19.00%. This indicates that the modified biochar and acidified material have a synergistic effect, which increases the urease, sucrose and catalase activities of the compost material, thereby promoting the nutrient conversion.

[0060] Table 4 Available nutrient contents of compost products of different treatments

[0061]

[0062] The maturity level of compost can be determined by the biological effect on plants after application, and the seed germination index comprehensively reflects the phytotoxicity of compost, which is the most sensitive and reliable evaluation index of compost maturity. Referring to Table 5, the seed germination inhibition of the material changes with the degree of maturity. After fermentation to the maturity period, the material of each treatment has reached the maturity standard, and the seed germination index of each treatment is 83.07%-89.86%. After the addition of acidified material (T3 and T4), the composting time is shortened by 7-14 days compared with the group without acidified material (T1 and T2), which indicates that the acidified material can accelerate the composting. Among them, compared with the addition of only modified biochar (T2) or only acidified material (T3), the addition of modified biochar, acidified material and composting accelerator (T4) has the highest seed germination index of the compost product, which is 89.86%, and the shortest composting time, which is shortened to 21 days. The reason is that the modified biochar and acidified material have a synergistic effect, which accelerates the material maturity.

[0063] Table 5 Composting time and seed germination index of different treatments

[0064]

[0065] 3. Effect of agricultural substrate on seedling raising

[0066] The product of aerobic compost fermentation is mixed with vermiculite in a certain proportion, and two treatments are set, with a commercial substrate as a control (A1) and the mixed substrate as an agricultural substrate (A2). Full and uniform cucumber seeds are selected, soaked in warm water at 55 DEG C for 20 minutes, cleaned, transferred to moist gauze, and placed in a 30 DEG C dark incubator. Appropriate water is sprayed on the gauze every day to keep the seeds moist. After 75% of the seeds germinate, the seeds with similar growth are sown in the seedling plug trays of different formulations. Clean water is used for irrigation from the start of sowing to the end of seedling, and the test period is 30 days.

[0067] Referring to Table 6, the height, stem diameter, germination rate, and seedling index of the cucumber seedlings grown in the seedling substrate are detected. The results show that the germination rate of the cucumber seedlings of the A2 treatment is higher, 1.34% higher than that of the A1. The height, stem diameter, and seedling index of the agricultural substrate (A2) are all higher than those of the commercial substrate, 24.83%, 43.48%, and 27.78% higher, respectively. The above results show that the agricultural substrate obtained by the method of the application can promote the growth of cucumber seedlings, and the cucumber seedlings are of good quality, better than the commercial substrate.

[0068] Table 6 Seedling effect

[0069]

[0070] The above only discloses the preferred embodiments of the application, and of course cannot limit the scope of the rights of the application. Those skilled in the art can understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the application still belong to the scope covered by the application.

Claims

1. A method of making an agricultural substrate, characterized by: The method comprises the following steps: (1) Bio-acidification: adding mushroom stem residue or mushroom stem powder or poultry manure, bran, and nitrogen-containing wastewater in a predetermined proportion to the branch powder to prepare initial materials with a carbon-nitrogen ratio of 29-32:1, taking part of the initial materials for sealed fermentation, and allowing the initial materials to hydrolyze and acidify under anaerobic conditions, wherein the moisture content of the initial materials is 90%-94%, the acidification temperature is 15-35 DEG C, the sealed fermentation time is 4-8 days, and the acidification ends to obtain acidified materials with a pH value of 4.5-5.5; (2) Aerobic compost fermentation: mixing the acidified materials prepared in step (1) with the remaining initial materials, modified biochar, and rot maturity accelerator to perform aerobic compost fermentation as compost materials, wherein the addition of the acidified materials can improve the problem of increased pH value of the aerobic compost materials caused by the addition of alkaline biochar, the carbon-nitrogen ratio of the compost materials is 25-30:1, the moisture content is 60%-70%, the initial temperature is 30-55 DEG C, the compost fermentation time is 21-28 days, and the compost fermentation ends to obtain the agricultural substrate; wherein the modified biochar is nano-iron-chitosan modified biochar or nano-iron-carboxymethyl cellulose modified biochar, the nano-iron-chitosan modified biochar or nano-iron-carboxymethyl cellulose modified biochar is used to promote the metabolic activity of compost microorganisms, and the addition of the acidified materials allows the compost process to have a fast temperature rise and a high temperature peak in the high-temperature period, so that the compost materials are rapidly matured, thereby accelerating the compost process.

2. The method of manufacturing an agricultural substrate according to claim 1, characterized in that: In step (1), the mass ratio of the branch powder to the mushroom stem residue or mushroom stem powder is 11-22:1, the bran accounts for 1%-2% of the total mass of the branch powder and the mushroom stem residue or mushroom stem powder, and the nitrogen-containing wastewater is 15-20 times the total mass of the branch powder and the mushroom stem residue or mushroom stem powder.

3. The method of manufacturing an agricultural substrate according to claim 1, characterized in that: In step (1), the mass ratio of the branch powder to the poultry manure is 1:1-5, the bran accounts for 1%-2% of the total mass of the branch powder and the poultry manure, and the nitrogen-containing wastewater is 2.5-5 times the total mass of the branch powder and the poultry manure.

4. The method of manufacturing an agricultural substrate according to claim 1, characterized in that: In step (1), the nitrogen-containing wastewater is one of yellow slurry water, manure water, and nitrogen-containing liquid.

5. The method of manufacturing an agricultural substrate according to claim 1, characterized in that: In step (1), the carbon-nitrogen ratio of the initial materials is 31:1, the moisture content is 92%, the acidification temperature is 35 DEG C, and the acidification time is 4 days; in step (2), the carbon-nitrogen ratio of the compost materials is 25:1, the moisture content is 60%, the initial temperature is 30 DEG C, and the compost time is 21 days.

6. The method of manufacturing an agricultural substrate according to claim 1, wherein: In step (2), the modified biochar accounts for 1%-3% of the total mass of the compost materials, and the rot maturity accelerator is a mixture of a microbial agent and an enzyme preparation, wherein the microbial agent accounts for 0.5%-1% of the total mass of the compost materials, and the enzyme preparation accounts for 0.5%-1% of the total mass of the compost materials.

7. The method of manufacturing an agricultural substrate according to claim 1, wherein: In step (2), the nano-iron-chitosan modified biochar or nano-iron-carboxymethyl cellulose modified biochar is prepared as follows: (1) crushing the branch powder to a particle size of 0.5 mm, heating under nitrogen gas at 400-500 DEG C at a heating rate of 5-10 DEG C / min, and pyrolyzing for 20-24 hours to obtain biochar; (2) Dissolve chitosan or sodium carboxymethyl cellulose in deionized water at a mass / volume ratio of 1:25 to prepare a 40 g / L chitosan solution or sodium carboxymethyl cellulose solution; (3) Add zero-valent iron powder to the NaOH solution and stir until the zero-valent iron is completely dissolved to prepare a 20 g / L zero-valent iron solution; (4) Mix the zero-valent iron solution with the chitosan solution or sodium carboxymethyl cellulose solution at a volume ratio of 1:2.5 to obtain a mixed solution, and add biochar to the mixed solution, which should be added slowly and stirred during the process. The mass ratio of the mixed solution to biochar is 4.5:1; (5) The mixture is sequentially subjected to ultrasonic treatment for 30 min, constant temperature oscillation for 2 hours, vacuum filtration and drying. The dried material is placed in a vacuum furnace, heated at 700℃ for 2 hours under nitrogen atmosphere, and then cooled to room temperature under nitrogen atmosphere for another 2 hours. The modified biochar is obtained. The modified biochar is sequentially washed with clean water and deionized water until the pH value is neutral, and then dried in an oven for standby use.

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