Biochar-based slow-release fertilizer based on slow-release prediction model and preparation method thereof

Abstract

The invention relates to the technical field of slow-release fertilizers, in particular to a charcoal-based slow-release fertilizer based on a slow-release prediction model and a preparation method of the charcoal-based slow-release fertilizer. According to the preparation method, biochar-based slow-release fertilizer preparation tests under different co-pyrolysis preparation conditions are established, and on the basis of qualitative analysis, the co-pyrolysis preparation conditions are taken as independent variables, the phosphorus accumulative release rate is taken as a response value, and a relational expression between the independent variables and the response value is obtained, so that a slow-release prediction model of the biochar-based slow-release fertilizer is established. The slow-release prediction model is utilized to obtain customized co-pyrolysis preparation conditions, and the biochar-based slow-release fertilizer prepared according to the customized co-pyrolysis preparation conditions can meet nutrient requirements of different plants and plants in different growth periods, so that the effects of efficiently utilizing the fertilizer and promoting healthy growth and harvest of the plants are achieved; therefore, the technical problems that a conventional biochar-based slow release fertilizer is low in utilization rate and influences normal growth of plants are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of slow-release fertilizers, and particularly relates to a biochar-based slow-release fertilizer based on a slow-release prediction model and a preparation method thereof. Background Art

[0002] In modern agriculture, the efficient utilization and sustainability of fertilizers are crucial. Traditional fertilizers have problems such as excessive nutrient release and low utilization rate, which not only cause waste of resources but also may have a negative impact on the environment. With the development demand of sustainable agriculture, biochar-based phosphate fertilizers have gradually attracted attention.

[0003] Biochar has a rich pore structure and a large specific surface area. The biochar-based slow-release fertilizer prepared based on biochar can adsorb nutrients and release them slowly, improving the utilization rate of fertilizers. However, due to the differences in nutrient requirements of different plants and plants at different growth stages, even biochar-based fertilizers are difficult to meet the nutrient requirements of different plants at different growth stages, resulting in the problems of low utilization rate and affecting the normal growth of plants for conventional biochar-based fertilizers. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art, and provide a biochar-based slow-release fertilizer based on a slow-release prediction model and a preparation method thereof, solving the technical problems of low utilization rate and affecting the normal growth of plants existing in conventional biochar-based slow-release fertilizers.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: The present invention provides a preparation method of a biochar-based slow-release fertilizer based on a slow-release prediction model, including the following steps: Using apple wood biomass, bentonite, and a phosphorus source as raw materials, establishing a preparation experiment of biochar-based slow-release fertilizers under different co-pyrolysis preparation conditions to obtain a series of biochar-based slow-release fertilizers; measuring the phosphorus release amounts of the series of biochar-based slow-release fertilizers at different time periods, and calculating the phosphorus cumulative release rate; using the co-pyrolysis preparation conditions as independent variables and the phosphorus cumulative release rate as the response value to obtain the relationship between the independent variables and the response value, so as to establish a slow-release prediction model of the biochar-based slow-release fertilizer; obtaining the nutrient requirements of the plant to be fertilized at different growth stages, determining the phosphorus absorption rate of the plant during the entire period, the absorption rate corresponding to the phosphorus cumulative release rate, substituting the corresponding phosphorus cumulative release rate into the slow-release prediction model of the biochar-based slow-release fertilizer to obtain the customized co-pyrolysis preparation conditions; and preparing the biochar-based slow-release fertilizer under the customized co-pyrolysis preparation conditions.

[0006] Optionally, the co-pyrolysis preparation conditions include the pyrolysis temperature, the heating rate, and the mass percentage of the bentonite in the raw materials.

[0007] Specifically, the pyrolysis temperature is 400°C to 700°C, the heating rate is 5°C / min to 15°C / min, and the mass ratio of bentonite in the raw materials is 0% to 20%.

[0008] Furthermore, the mass ratio of apple wood biomass, bentonite, and phosphorus source is 6 - 8:1 - 3:1. Preferably, the phosphorus source is potassium phosphate.

[0009] Optionally, the slow-release prediction model of the biochar-based slow-release fertilizer is obtained by design using the Box-Behnken method.

[0010] Optionally, the preparation method of the series of biochar-based slow-release fertilizers includes the following steps: Crush apple wood to obtain apple wood biomass; using the uniformly mixed apple wood biomass, bentonite, and phosphorus source as raw materials, under a protective atmosphere, heat from room temperature to the pyrolysis temperature and then carry out co-pyrolysis treatment to prepare a biochar-based slow-release fertilizer with a hierarchical structure.

[0011] Optionally, the relationship between the independent variables and the response value is: Y = 172.03 - 0.337A + 1.049B - 2.222C - 0.00076AB + 0.00032AC - 0.033BC + 0.00031A 2 - 0.014B 2 + 0.129C 2 ; wherein, A represents the pyrolysis temperature, B represents the mass ratio of bentonite in the raw materials, and C represents the heating rate. A, B, and C are independent variables, and Y corresponds to the cumulative phosphorus release rate.

[0012] Optionally, the calculation formula for the cumulative phosphorus release rate is as follows: ; wherein, V S and V0 are respectively the displacement volume of deionized water and the total volume of the release medium, C i is the concentration of the release liquid during the i-th displacement sampling, m0 is the total mass of phosphorus elements contained in the biochar-based slow-release fertilizer, and n is the number of times of deionized water displacement sampling.

[0013] Optionally, it further includes the following steps: After applying the prepared biochar-based slow-release fertilizer, analyze the growth situation of plants, and verify and optimize the slow-release prediction model of the biochar-based slow-release fertilizer according to the results.

[0014] The present invention also provides a biochar-based slow-release fertilizer based on a slow-release prediction model, which is prepared by using the preparation method of the biochar-based slow-release fertilizer based on the slow-release prediction model as described above.

[0015] The beneficial effects of the present invention are as follows. Compared with the prior art, the preparation method of the present invention conducts experiments on the preparation of biochar-based slow-release fertilizers under different co-pyrolysis preparation conditions. On the basis of qualitative analysis, taking the co-pyrolysis preparation conditions as independent variables and the cumulative phosphorus release rate as the response value, the relationship between the independent variables and the response value is obtained to establish a slow-release prediction model for biochar-based slow-release fertilizers. And the customized co-pyrolysis preparation conditions are obtained by using this slow-release prediction model. The biochar-based slow-release fertilizers prepared according to the customized co-pyrolysis preparation conditions can meet the nutrient requirements of different plants and different growth periods of plants, thereby achieving the effects of efficient utilization of fertilizers, promoting the healthy growth and harvest of plants, and further solving the technical problems of low utilization rate and affecting the normal growth of plants existing in conventional biochar-based slow-release fertilizers. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a comparison chart of the phosphorus cumulative release rates of biochar-based slow-release fertilizers under different preparation conditions provided by the present invention. (a) is a line statistical chart of the phosphorus cumulative release rates of biochar-based slow-release fertilizers prepared under different pyrolysis temperature conditions, (b) is a bar chart of the phosphorus cumulative release rates and the initial phosphorus release rates of biochar-based slow-release fertilizers prepared under different pyrolysis temperature conditions, (c) is a line statistical chart of the phosphorus cumulative release rates of biochar-based slow-release fertilizers prepared under different mass ratios of bentonite in the raw materials, (d) is a bar chart of the phosphorus cumulative release rates and the initial phosphorus release rates of biochar-based slow-release fertilizers prepared under different mass ratios of bentonite in the raw materials, (e) is a line statistical chart of the phosphorus cumulative release rates of biochar-based slow-release fertilizers prepared under different heating rate conditions, (f) is a bar chart of the phosphorus cumulative release rates and the initial phosphorus release rates of biochar-based slow-release fertilizers prepared under different heating rate conditions.

[0017] Figure 2 It is a pore size distribution chart of biochar-based slow-release fertilizers prepared under different co-pyrolysis conditions provided by the present invention. (a) is a pore size distribution chart of biochar-based slow-release fertilizers prepared under different pyrolysis temperature conditions, (b) is a pore size distribution chart of biochar-based slow-release fertilizers prepared under different mass ratios of bentonite in the raw materials, (c) is a pore size distribution chart of biochar-based slow-release fertilizers prepared under different heating rate conditions.

[0018] Figure 3These are the scanning electron microscope images of the biochar-based slow-release fertilizers prepared under different co-pyrolysis conditions provided by the present invention. (a) is the scanning electron microscope image of the biochar-based slow-release fertilizer with the sample name 4A + 10B + P-10, (b) is the scanning electron microscope image of the biochar-based slow-release fertilizer with the sample name 5A + 10B + P-10, (c) is the scanning electron microscope image of the biochar-based slow-release fertilizer with the sample name 7A + 10B + P-10, (d) is the scanning electron microscope image of the biochar-based slow-release fertilizer with the sample name 5A + 20B + P-10, (e) is the scanning electron microscope image of the biochar-based slow-release fertilizer with the sample name 5A + 30B + P-10, (f) is the scanning electron microscope image of the biochar-based slow-release fertilizer with the sample name 5A + 10B + P-5, and (g) is the scanning electron microscope image of the biochar-based slow-release fertilizer with the sample name 5A + 10B + P-15.

[0019] Figure 4 These are the phosphorus species distribution maps of the biochar-based slow-release fertilizers prepared under different co-pyrolysis conditions provided by the present invention.

[0020] Figure 5 These are the statistical charts of the combined conditions of different biochar-based slow-release fertilizers provided by the present invention.

[0021] Figure 6 These are the slow-release prediction models of the biochar-based slow-release fertilizers provided by the present invention. (a), (c), and (e) are the three-dimensional views of the slow-release prediction models in different three-dimensional coordinate systems, and (b), (d), and (f) are the two-dimensional views of the slow-release prediction models in different two-dimensional coordinate systems. Detailed implementation manners

[0022] To solve the above technical problems, the present invention provides a biochar-based slow-release fertilizer based on a slow-release prediction model and its preparation method. Now, the technical solutions and embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0023] At present, the research on the influencing factors of the morphological transformation of phosphorus elements and the nutrient release law in biochar-based slow-release fertilizers is not sufficient.

[0024] The co-pyrolysis condition is one of the key factors affecting the performance of biochar-based slow-release fertilizers. Different co-pyrolysis conditions will lead to the differentiation of the fertilizer structure, and will also affect the change of the phosphorus element form, further affecting the slow-release effect of the fertilizer. Therefore, in-depth study of the influence of co-pyrolysis conditions on the fertilizer morphology structure and the morphological transformation of phosphorus elements is of great significance for optimizing the performance of biochar-based slow-release fertilizers.

[0025] In addition, the response surface curve model provides an effective method for studying the influence of multi-factor interactions on the target response. By establishing a response surface model, the nutrient release law of biochar-based slow-release fertilizers under different conditions can be predicted, or the corresponding co-pyrolysis conditions can be deduced according to the target through the model. Particularly importantly, the model can better meet the nutrient requirements of different growth stages of plants. In the initial stage of plant growth, the nutrient demand is relatively low, and the biochar-based slow-release fertilizer can slowly release an appropriate amount of nutrients to meet the basic growth needs of plants; while in the critical stages such as the vigorous growth stage and the fruiting stage, the nutrient demand of plants increases significantly. At this time, the biochar-based slow-release fertilizer can adjust the nutrient release rate according to the prediction of the response surface model to ensure that plants can obtain sufficient nutrient supply, thereby realizing the efficient utilization of fertilizers and promoting the healthy growth and harvest of plants.

[0026] A preparation method of a biochar-based slow-release fertilizer based on a slow-release prediction model provided by the present invention includes the following steps: (1) Using apple wood biomass, bentonite, and a phosphorus source as raw materials, a preparation experiment of biochar-based slow-release fertilizers under different co-pyrolysis preparation conditions is established to obtain a series of biochar-based slow-release fertilizers.

[0027] Specifically, the preparation method of the series of biochar-based slow-release fertilizers includes the following steps: Crush the apple wood to obtain apple wood biomass; use the uniformly mixed apple wood biomass, bentonite, and phosphorus source as raw materials, and under a protective atmosphere, heat from room temperature to the pyrolysis temperature and then carry out co-pyrolysis treatment to prepare a biochar-based slow-release fertilizer with a hierarchical structure.

[0028] Specifically, the co-pyrolysis preparation conditions include the pyrolysis temperature, the heating rate, and the mass percentage of bentonite in the raw materials. Among them, the pyrolysis temperature is 400°C to 700°C, the heating rate is 5°C / min to 15°C / min, and the mass percentage of bentonite in the raw materials is 0% to 20%. And the mass ratio of apple wood biomass, bentonite, and phosphorus source is 6 to 8:1 to 3:1. Preferably, the phosphorus source is potassium phosphate.

[0029] (2) Measure the phosphorus release amount of the series of biochar-based slow-release fertilizers at different time periods and calculate the phosphorus cumulative release rate.

[0030] Specifically, the calculation formula of the phosphorus cumulative release rate is as follows: ; where V S and V0 are respectively the replacement volume of deionized water and the total volume of the release medium, C i is the concentration of the release liquid during the i-th replacement sampling, m0 is the total mass of phosphorus elements contained in the biochar-based slow-release fertilizer, and n is the number of times of deionized water replacement sampling.

[0031] (3) Taking the co-pyrolysis preparation conditions as independent variables and the cumulative phosphorus release rate as the response value, obtain the relationship between the independent variables and the response value to establish a slow-release prediction model for the biochar-based slow-release fertilizer. Preferably, the slow-release prediction model of the biochar-based slow-release fertilizer is obtained by using the Box-Behnken method.

[0032] Specifically, the relationship between the independent variables and the response value is: Y = 172.03 - 0.337A + 1.049B - 2.222C - 0.00076AB + 0.00032AC - 0.033BC + 0.00031A 2 - 0.014B 2 + 0.129C 2 ; where A represents the pyrolysis temperature, B represents the mass percentage of bentonite in the raw material, and C represents the heating rate. A, B, and C are independent variables, and Y corresponds to the cumulative phosphorus release rate.

[0033] Specifically, in the qualitative analysis stage of a series of biochar-based slow-release fertilizers in the laboratory, the cumulative phosphorus release rate corresponding to Y is measured under static water conditions at 25°C.

[0034] (4) Obtain the nutrient requirements of the plants to be fertilized at different growth stages, determine the phosphorus absorption rate of the plants throughout the cycle, where the absorption rate corresponds to the cumulative phosphorus release rate, and substitute the corresponding cumulative phosphorus release rate into the slow-release prediction model of the biochar-based slow-release fertilizer to obtain the customized co-pyrolysis preparation conditions. Under the customized co-pyrolysis preparation conditions, the biochar-based slow-release fertilizer is prepared.

[0035] In practical applications, the plants to be fertilized can be different plants, and no specific variety types of plants are limited.

[0036] The present invention will be described in detail below through specific embodiments. The embodiments are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0037] Example 1 A method for constructing a slow-release prediction model of a biochar-based slow-release fertilizer, and the specific implementation steps are as follows: Step 1: Prepare a series of biochar-based slow-release fertilizers.

[0038] Weigh 20 g of apple wood biomass, 2.5 g of bentonite (mass ratio is 10%), and 2.5 g of potassium phosphate (the mass ratio is fixed at 10% in the following examples) after pre-treatment such as shearing, washing, drying, and crushing. After fully mixing, place them in a tubular furnace. Before starting the tubular furnace, nitrogen gas needs to be introduced for a period of time (about 15 minutes) to ensure that oxygen is completely exhausted, and the nitrogen gas flow rate is controlled at 150 - 200 mL / min. Pyrolyze three times in total. Set the program to rise from room temperature to the target temperature (400, 550, 700 °C) at a rate of 10 °C / min respectively, then keep the target temperature for 2 hours, cool down to room temperature, take out and store in a sealed bag, and mark the sample names as 4A + 10B + P - 10, 5A + 10B + P - 10, and 7A + 10B + P - 10. Among them, 4, 5, and 7 represent the pyrolysis temperatures of 400, 550, and 700 °C respectively, A represents the pyrolysis temperature; 10 is the mass ratio of bentonite in the raw material, B is the first letter of the English word for bentonite, representing bentonite; 10 is the heating rate.

[0039] Step 2: Calculate the cumulative phosphorus release rate.

[0040] Taking the cumulative nutrient release rate and the nutrient release period as the measurement indicators, optimize the co-pyrolysis preparation conditions by setting up a static water slow-release experiment to find the intermediate value of the independent variable factors for the establishment of the response surface curve model. Weigh 0.1 g of the biochar-based slow-release fertilizer and place it on a nylon cloth (400 mesh), with a size of about 4 cm * 4 cm. Tie the nylon cloth with a thin thread and immerse it in a conical flask containing 50 mL of deionized water. Leave a certain length of the thin thread outside the bottle to fix the position of the nylon bag in the water. Each group is repeated three times. The system is sealed with a plastic film to avoid water evaporation. The calculation of the cumulative phosphorus release rate is shown in formula (1).

[0041] (1).

[0042] (1) Explore the intermediate value of the pyrolysis temperature.

[0043] Place 20 g of apple wood biomass, 2.5 g of bentonite (mass ratio is 10%), and 2.5 g of potassium phosphate in three quartz boats respectively, and pyrolyze at 400 °C, 550 °C, and 700 °C for 2 hours, and mark the sample names (4A + 10B + P - 10 °C / min, 5A + 10B + P - 10 °C / min, and 7A + 10B + P - 10 °C / min). See Figure 1 in (a) and (b). According to the results of the single-factor experiment, when the pyrolysis temperature is 550 °C, the cumulative phosphorus release rate under this condition reaches 72.94% in 42 days, which is better than the biochar-based slow-release fertilizers prepared at 400 and 700 °C. This is because the biochar-based slow-release fertilizer (5A + 10B + P - 10 °C / min) has a relatively regular pore structure, a concentrated pore size distribution, and a good hierarchical structure, asFigure 2 and Figure 3 as shown

[0044] (2) Explore the intermediate value of the mixing ratio.

[0045] Weigh another 17.5 g of apple wood biomass, 5 g of bentonite (mass ratio is 20%), 2.5 g of potassium phosphate, as well as 15 g of apple wood biomass, 7.5 g of bentonite (mass ratio is 30%) and 2.5 g of potassium phosphate respectively, and place them in two quartz boats. Pyrolyze at 550 °C for 2 h, and mark the sample names (5A + 20B + P - 10 °C / min, 5A + 30B + P - 10 °C / min). Combining Figure 1 in (c) and (d), according to the results of the single-factor experiment, when the bentonite accounts for 10%, the cumulative release rate of phosphorus reaches 72.94% in 42 days under this condition, which is better than the biochar-based slow-release fertilizers prepared under the bentonite ratios of 20% and 30%.

[0046] (3) Explore the intermediate value of the heating rate.

[0047] Weigh another 20 g of apple wood biomass, 2.5 g of bentonite and 2.5 g of potassium phosphate, and heat them to 550 °C at the heating rates of 5 and 15 °C / min respectively, pyrolyze for 2 h, and mark the sample names (5A + 10B + P - 5 °C / min, 5A + 10B + P - 15 °C / min). As Figure 1 shown in (e) and (f), according to the results of the single-factor experiment, when the heating rate is 10 °C / min, the cumulative release rate of phosphorus reaches 72.94% in 42 days under this condition, which is better than the biochar-based slow-release fertilizers prepared under the heating rates of 5 and 15 °C / min.

[0048] (4) Morphological distribution and transformation of phosphorus in the co-pyrolyzed biochar-based slow-release fertilizer Weigh 0.1 g of the samples (biochar-based slow-release fertilizers prepared in steps (1), (2) and (3)) respectively, put them into a conical flask containing 50 mL of deionized water, and shake in a water bath constant temperature oscillator at 180 rpm for 16 h. Each group is repeated three times. After the reaction, filter the residue with quantitative filter paper, and the filtrate is used to measure the phosphorus content; digest with potassium persulfate at 120 °C for 30 min to convert polyphosphate and organic phosphate into orthophosphate; determine the concentration of orthophosphate by ammonium molybdate spectrophotometry. Then, the filter residue is successively shaken with 50 mL of 0.5 M NaHCO3 (pH = 8.5), 0.1 M NaOH and 1.0 M HCl at 25 °C for 16 h, and the measurement method and operation are the same as above. Finally, digest the obtained insoluble residue with concentrated nitric acid, perchloric acid and hydrofluoric acid at 180 °C to extract the stable total phosphorus (TP). The results are as Figure 4As shown, the temperature change during the co-pyrolysis process has a significant impact on the morphological distribution of phosphorus. The proportion of HCl-P in 4A + 10B + P - 10℃ / min is only 4%, while the proportion of HCl-P in 7A + 10B + P - 10℃ / min reaches 24%. Conversely, the proportion of H2O-P in 4A + 10B + P - 10℃ / min is as high as 43%, while the proportion of H2O-P in 7A + 10B + P - 10℃ / min decreases to 25%. Therefore, the higher the pyrolysis temperature, the higher the phosphorus content extracted by hydrochloric acid (7A + 10B + P - 10℃ / min), and the lower the H2O-P content in the biochar-based slow-release fertilizer. By adjusting the pyrolysis temperature, the content of slightly soluble or insoluble phosphorus is increased to promote or inhibit the hierarchical release of phosphorus in the biochar-based slow-release fertilizer with a hierarchical structure. The available phosphorus (components that can be absorbed by plants) in biomass can be immobilized in a more stable form during pyrolysis.

[0049] Step 3: Obtain the relationship formula and construct the response surface curve model.

[0050] First, the intermediate values of the independent variables of the response surface curve were determined through preliminary single-factor experiments. The pyrolysis temperature was 550℃, the bentonite mixing ratio was 10%, and the heating rate was 10℃ / min. Then, using Design-Expert 13 software, click Response Surface - Box-Behnken method in sequence, and input the independent variable names, units, and low / high values on the display interface (the low / high values of the pyrolysis temperature are 400 and 700℃ respectively, the low / high values of the bentonite mixing ratio are 0 and 20% respectively, and the low / high values of the heating rate are 5 and 15℃ / min respectively), and click "Next". Finally, input the name and unit of the dependent variable, and click "Finish" in the lower right corner.

[0051] After the above operations are completed, the system will combine the independent variables into 17 groups, as Figure 5 shown. Conduct actual experiments according to the designed plan. Prepare different biochar-based slow-release fertilizers according to 17 combined conditions, and measure the cumulative release rate of phosphorus within 42 days in still water. The slow-release experiment steps are the same as above, and each group is repeated three times. Input the experimental results in the last column to generate a three-dimensional model, that is, the slow-release prediction model, as Figure 6 shown. In addition, analyze the data to obtain the relationship equation between the cumulative release rate of phosphorus and the pyrolysis temperature, the mass proportion of bentonite in the raw material, and the heating rate from Design-Expert 13 software, as shown in formula (2):

[0052] Y = 172.03 - 0.337A + 1.049B - 2.222C - 0.00076AB + 0.00032AC - 0.033BC + 0.00031A 2 - 0.014B 2 + 0.129C2 (2); Among them, A represents the pyrolysis temperature, B represents the mass percentage of bentonite in the raw material, and C represents the heating rate. A, B, and C are independent variables, and Y corresponds to the cumulative phosphorus release rate of static water at 25°C.

[0053] Example 2 A method for applying a slow-release prediction model of a biochar-based slow-release fertilizer, and the specific implementation steps are as follows: First of all, the growth rates of Chinese cabbage in different growth periods are different, and the demand for nutrient elements is also different, mainly concentrated in the rosette stage and the heading stage. The growth rate of the rosette stage (about 20 days) accelerates significantly, and the phosphorus absorbed during this period accounts for 29.1% - 45.0% of the total phosphorus absorbed during the whole growth period; while in the heading stage (about 25 days), the phosphorus absorbed accounts for about 32% - 51% of the total phosphorus absorbed during the whole growth period. Therefore, it is required that the cumulative release rate of phosphorus in the fertilizer reaches 61.1% - 96% within 45 days, and then the preparation conditions of the biochar-based slow-release fertilizer that meet the requirements are deduced according to the slow-release prediction model.

[0054] Then, by consulting the literature, materials and according to the planting experience of local farmers, it is determined that 80 catties of compound fertilizer can be applied per mu of Chinese cabbage. A greenhouse is about 7 fen of land (470m 2 ), that is, 56 catties of compound fertilizer. However, in order to achieve the purpose of reducing the amount of fertilizer and increasing the efficiency, each greenhouse is fertilized according to 75% of the compound fertilizer dosage, that is, 42 catties.

[0055] Secondly, 4 treatment groups (four greenhouses) are set up, namely a blank control group without fertilization (CK), a commercial biochar group (BC), a biochar-based phosphate fertilizer group (BCP), and a biochar-based slow-release phosphate fertilizer group (BCBP) prepared according to the slow-release prediction model. During the entire growth period of the crop, soil and crops are sampled at fixed time intervals (once every two weeks) to measure the nutrient content in the soil and analyze the nutrient absorption of the crops. The results show that the Chinese cabbage treated with the biochar-based slow-release fertilizer grows well, and its fresh weight and dry weight are much higher than those of other treatment groups, and the contents of soluble sugar and soluble protein are significantly increased, and the phosphorus content in the Chinese cabbage leaves also increases.

[0056] The above description is only the preferred embodiment of the present invention, and the above specific embodiments are not limitations to the present invention. Within the scope of the technical idea of the present invention, various deformations and modifications can occur. Any modification, modification or equivalent replacement made by those of ordinary skill in the art according to the above description shall fall within the scope protected by the present invention.

Claims

1. A method for preparing a biochar-based slow-release fertilizer based on a slow-release prediction model, characterized in that: The following steps are involved: Using apple wood biomass, bentonite and phosphorus source as raw materials, a biochar-based slow-release fertilizer preparation experiment was established under different co-pyrolysis preparation conditions, and a series of biochar-based slow-release fertilizers were obtained. The phosphorus release of a series of biochar-based slow-release fertilizers at different time periods was measured, and the cumulative phosphorus release rate was calculated; The co-pyrolysis preparation conditions were used as independent variables, and the cumulative phosphorus release rate was used as the response value. The relationship between the independent variables and the response value was obtained to establish a slow-release prediction model for biochar-based slow-release fertilizer. Obtain the nutrient requirements of the plants to be fertilized in different growth cycles, determine the phosphorus absorption rate of the plants in the entire cycle, the absorption rate corresponds to the cumulative phosphorus release rate, substitute the corresponding cumulative phosphorus release rate into the slow-release prediction model of the biochar-based slow-release fertilizer, and obtain customized co-pyrolysis preparation conditions; Biochar-based slow-release fertilizer was prepared under customized co-pyrolysis preparation conditions.

2. The method for preparing a biochar-based slow-release fertilizer based on a slow-release prediction model according to claim 1, characterized in that: The co-pyrolysis preparation conditions include pyrolysis temperature, heating rate and the mass proportion of the bentonite in the raw materials.

3. The method for preparing a biochar-based slow-release fertilizer based on a slow-release prediction model according to claim 2, characterized in that: The pyrolysis temperature is 400° C. to 700° C., the heating rate is 5° C. / min to 15° C. / min, and the mass proportion of the bentonite in the raw material is 0% to 20%.

4. The method for preparing a biochar-based slow-release fertilizer based on a slow-release prediction model according to claim 3, characterized in that: The mass ratio of the apple wood biomass, bentonite and phosphorus source is 6-8:1-3:

1.

5. The method for preparing a biochar-based slow-release fertilizer based on a slow-release prediction model according to claim 1, characterized in that: The slow-release prediction model of the biochar-based slow-release fertilizer is designed and obtained by using the Box-Behnken method.

6. The method for preparing a biochar-based slow-release fertilizer based on a slow-release prediction model according to claim 2, characterized in that: The preparation method of the series of biochar-based slow-release fertilizers comprises the following steps: crushing the apple wood to obtain apple wood biomass; Using uniformly mixed apple wood biomass, bentonite and phosphorus source as raw materials, the temperature is raised from room temperature to pyrolysis temperature under a protective atmosphere and then co-pyrolysis treatment is performed to obtain a biochar-based slow-release fertilizer with a hierarchical structure.

7. The method for preparing a biochar-based slow-release fertilizer based on a slow-release prediction model according to claim 1, characterized in that: The relationship between the independent variable and the response value is: <h2 style=";text-align:left;direction:ltr">Y=172.03-0.337A+1.049B-2.222C-0.00076AB+0.00032AC-0.033BC+0.00031A<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> -0.014B<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +0.129C<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> ; Among them, A represents the pyrolysis temperature, B represents the mass proportion of bentonite in the raw material, C represents the heating rate, A, B and C are independent variables, and Y represents the cumulative release rate of phosphorus.

8. The method for preparing biochar-based slow-release fertilizer based on a slow-release prediction model according to claim 1, characterized in that: The calculation formula of phosphorus cumulative release rate is as follows: ； Among them, V S and V0 are the replacement amount of deionized water and the total volume of the release medium, respectively. i is the concentration of the released liquid at the i-th replacement sampling, m0 is the total mass of phosphorus contained in the biochar-based slow-release fertilizer, and n is the number of deionized water replacement samplings.

9. The method for preparing biochar-based slow-release fertilizer based on a slow-release prediction model according to claim 1, characterized in that: The following steps are also included: After the prepared biochar-based slow-release fertilizer is applied, the growth of the plants is analyzed, and the slow-release prediction model of the biochar-based slow-release fertilizer is verified and optimized based on the results.

10. A biochar-based slow-release fertilizer based on a slow-release prediction model, characterized in that: The biochar-based slow-release fertilizer is prepared by the method for preparing the biochar-based slow-release fertilizer based on the slow-release prediction model as described in any one of claims 1 to 9.

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