Method for promoting growth of vegetables by using biochar modified hydrogel slow-release fertilizer
By optimizing the hydrogel formulation and using biochar modification, biochar-modified hydrogel slow-release fertilizer was prepared, which solved the problems of low fertilizer utilization efficiency and unstable hydrogel performance in existing fertilization methods, and achieved long-term stable release of nutrients and increased vegetable yield.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-04
- Publication Date
- 2026-04-07
AI Technical Summary
Existing fertilization methods result in low fertilizer utilization efficiency and serious resource waste. Furthermore, hydrogel slow-release fertilizers are unstable in performance under external interference and are difficult to match with crop growth cycles.
By optimizing the hydrogel preparation formula and using biochar modification, biochar-modified hydrogel slow-release fertilizer was prepared. Combined with freeze-thaw cycle treatment, its slow-release performance and water retention capacity were improved.
It achieves long-term stable release of nutrients, reduces fertilizer loss, increases vegetable yield, and lowers resource input costs.
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of slow-release fertilizer, and particularly relates to a method for promoting growth of vegetables by using biochar modified hydrogel slow-release fertilizer. BACKGROUND
[0002] With the development of social economy, people's living standards are improved, and the demand for fresh vegetables is increasing. Although various planting modes including water culture expand the source of fresh vegetables, the soil cultivation mode is still the main way of vegetable production. During the beginning and process of vegetable planting, fertilizers need to be applied to meet the nutritional needs of vegetable growth. However, the existing fertilization mode leads to low fertilizer utilization efficiency, only about 20% of nutrients can be absorbed and utilized, and the remaining nutrients are lost with water flow, microbial activity, etc., which not only causes waste of resources, but also easily causes environmental problems such as water body eutrophication and greenhouse effect. Therefore, it is urgent to develop a new fertilization mode to promote the growth of vegetables while reducing resource input.
[0003] Hydrogel fertilizer is concerned because it can reduce water loss and achieve slow release of nutrients, which helps to optimize resource input. However, the practical application of hydrogel slow-release fertilizer is disturbed by external factors such as pH fluctuation, high temperature and mechanical stress, which destroys its slow-release and stability performance, leading to poor effect. In addition, it is still a major challenge to match the release period of nutrients loaded by hydrogel with the growth period of different crops. Therefore, strategies are needed to improve the application performance of hydrogel slow-release fertilizer.
[0004] Biochar is recognized for its significant advantages in soil remediation, including improving soil fertility, improving soil structure, and enhancing water retention capacity. In addition, biochar also has the characteristics of high porosity, large specific surface area and as an electron donor-acceptor carrier. Interestingly, by forming a nanoscale organic coating on its surface, biochar not only can fix nutrients, but also can stimulate microbial activity. Therefore, based on the theory of binary complementary materials, by engineering the nanoscale organic coating-biochar heterojunction to synthesize modified hydrogel, a promising way is provided to improve water retention capacity and reduce fertilizer loss. SUMMARY
[0005] The present application aims at the deficiencies of the current vegetable planting mode and the technical defects of hydrogel slow-release fertilizer. By optimizing the preparation formula of hydrogel and using biochar modification to strengthen its performance, a biochar modified hydrogel slow-release fertilizer is prepared. The preparation method of the slow-release fertilizer has the advantages of simple process, convenient operation, cheap and easily available raw materials, and low cost. The biochar modified hydrogel slow-release fertilizer prepared by the method has the advantages of good slow-release performance, strong water retention capacity and environmental stability, which is of great significance for improving the yield of vegetables.
[0006] The application adopts the technical scheme as follows: A method for promoting the growth of vegetables by using biochar modified hydrogel slow-release fertilizer, the method comprising mixing the biochar modified hydrogel slow-release fertilizer with tilled soil, irrigating to make the soil moist and sowing, harvesting after the vegetables grow for a certain period of time, and irrigating regularly during the period; The biochar modified hydrogel slow-release fertilizer is obtained by freeze-thaw cycle treatment of a solution containing biochar, nutrients and polymers.
[0007] In some embodiments, the preparation method of the biochar modified hydrogel slow-release fertilizer comprises the following steps: S1, heating and stirring to dissolve polyvinyl alcohol, gelatin and quaternized chitosan respectively, then mixing and stirring according to different proportions to prepare a polymer mixed solution; S2, adding nutrients and biochar to the polymer mixed solution, heating and stirring, adding a crosslinking agent, and continuing to heat and stir to obtain a mixed biochar gel solution; S3, after ultrasonic treatment of the mixed biochar gel solution, three "freeze-thaw cycle" treatments are performed to obtain the biochar modified hydrogel slow-release fertilizer.
[0008] In some embodiments, the biochar is biochar obtained by anaerobic pyrolysis of agricultural and forestry biomass waste, such as sorghum straw biochar. Preferably, the preparation method of the sorghum straw biochar comprises the following steps: first, washing and drying the sorghum straw, then crushing and sieving to obtain sorghum straw powder; then, pyrolyzing the sorghum straw powder, and after pyrolysis is completed, grinding and sieving to obtain sorghum straw biochar. Further preferably, the pyrolysis conditions are pyrolysis at 750℃ for 1 hour with a heating rate of 5 ℃ / min. Preferably, the addition amount of the biochar is 25-100 wt% of the dry matter mass in the polymer mixed solution.
[0009] In some embodiments, the nutrients are at least one of different forms of nitrogen, phosphorus and potassium nutrients, such as ammonium nitrate, sodium nitrate, potassium nitrate, ammonium chloride, ammonium dihydrogen phosphate, potassium dihydrogen phosphate, sodium dihydrogen phosphate, potassium chloride and urea. Preferably, the amount of the nutrients is 5-25 wt% of the dry matter mass in the polymer mixed solution.
[0010] In some embodiments, the concentrations of polyvinyl alcohol, gelatin and quaternized chitosan in the polymer mixed solution are 3.3 wt%, 4.4 wt% and 4.4 wt%, respectively.
[0011] In some embodiments, the crosslinking agent is genipin or glutaraldehyde. Preferably, the concentration of the crosslinking agent in the mixed biochar gel solution is 0.05~0.1 wt%.
[0012] In some embodiments, in step S1, polyvinyl alcohol 1799 is added to water and heated and stirred at 80-95°C for 0.5-2 hours to obtain a polyvinyl alcohol solution. Gelatin powder is added to water and heated and stirred at 45-50°C for 0.5-1 hour to obtain a gelatin solution. Add quaternized chitosan powder to water and heat and stir at 50-70 ℃ for 1-3 hours to obtain quaternized chitosan solution; The polyvinyl alcohol solution, the gelatin solution, and the quaternized chitosan solution are mixed, and then heated and stirred at 50-70°C for 0.5-1.5 hours.
[0013] In some embodiments, in step S2, the nutrients are dissolved in water and then added to the polymer mixture; the mixture is then heated and stirred at 40–60°C for 15–60 minutes.
[0014] In some embodiments, in step S3, the ultrasonic treatment time is 5 to 15 minutes; the freeze-thaw conditions are freezing at -40°C to -10°C for 8 to 16 hours, thawing at 4°C to 30°C for 8 to 16 hours, and repeating 3 times.
[0015] In some embodiments, the soil tillage depth is 10-20 cm; the amount of biochar-modified hydrogel slow-release fertilizer is 0.5-2 wt% of dried biochar-modified hydrogel slow-release fertilizer per acre of cultivated land relative to the usable soil mass (calculated at a depth of 20 cm); the vegetables are one or more of lettuce, rapeseed, spinach, and romaine lettuce; the planting time is 1-3 months; and the irrigation frequency is 1-2 times per week.
[0016] In some embodiments, the planting includes the following steps: (1) Site selection and land preparation: Select a plot of land with good drainage, ventilation and light, and deep plow the plot before planting. Apply biochar modified hydrogel slow-release fertilizer according to the available soil quality of the plot, and water until the soil is completely moist. (2) Sowing: 2 to 3 days after the soil in step (1) has been watered, select vegetable seeds that are free from pests and diseases and have a high germination rate and sow them directly in the soil; (3) Seedling management: thinning, fixing, water management and weeding of vegetables; (4) Field management: Irrigation management, pest and disease control, and weeding throughout the entire growth cycle of vegetables; (5) Harvesting: When the vegetable plants grow to 15-30 cm in height, they can be harvested.
[0017] Compared with the prior art, the advantages of the present invention are as follows: This invention provides a method for promoting vegetable production using biochar-modified hydrogel slow-release fertilizer. Compared with hydrogels prepared from other materials, the preferred polyvinyl alcohol, gelatin, and quaternized chitosan of this invention have superior nutrient loading capacity. The quaternized functional groups of quaternized chitosan can combine with nitrate and phosphate groups through electrostatic interaction, and the ammonium groups can combine with the deprotonated carboxyl groups of gelatin through electrostatic interaction, thus enabling nutrients to be loaded onto the hydrogel.
[0018] In this invention, the amount of biochar added is 25% to 100% of the dry matter mass of the polymer in the hydrogel. By optimizing the content of biochar in the hydrogel material, a uniform linear matrix of biochar is formed within the pore wall matrix of the hydrogel, which helps to improve the performance of biochar-modified hydrogel slow-release fertilizer. At the same time, the electron shuttle properties of biochar can enhance the electronic interaction between nutrients and polymer monomers, promote the binding of nutrients with the hydrogel, and reduce the release rate of nutrients. Therefore, it is possible to achieve a long-term and stable supply of nutrients to vegetables from the hydrogel.
[0019] This invention provides a method for promoting vegetable production using biochar-modified hydrogel slow-release fertilizer. The biochar-modified hydrogel slow-release fertilizer has advantages such as good nutrient slow-release effect, strong water retention capacity and environmental stability. It can be widely used in the cultivation of edible leafy vegetables (such as lettuce, rapeseed, spinach and romaine lettuce). Therefore, when biochar-modified hydrogel slow-release fertilizer is used in vegetable cultivation, it can significantly increase vegetable yield while reducing fertilizer and irrigation water consumption. It has the advantages of low cost, low resource input and high vegetable yield, with excellent economic benefits and excellent application prospects. Detailed Implementation
[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0021] In this embodiment of the invention, all raw materials and instruments used are commercially available. Unless otherwise specified, the process used is a conventional process, the equipment used is conventional equipment, and the data obtained are all average values from three or more repeated experiments.
[0022] Example 1
[0023] A method for promoting vegetable growth using biochar-modified hydrogel slow-release fertilizer, specifically involving the use of biochar-modified hydrogel slow-release fertilizer as fertilizer for growing lettuce, includes the following steps: Take 1.8 g of nutrient-rich biochar-modified hydrogel slow-release fertilizer (named GQP@50BC) and add it to 180 g of soil. Mix well and water the soil thoroughly with ultrapure water. On the second day, 8 lettuce seeds were sown in the soil and placed under environmental conditions for planting; After the seeds germinate, thin the seedlings when they have 2-3 true leaves, and then thin them to 4 seedlings when they have 4-5 true leaves. After that, water them regularly and weed them once a week. During the growth cycle, water management, pest and disease control, and weeding should be carried out as required. Harvesting begins when the plants grow to 15 cm in height.
[0024] In this embodiment, the preparation method of the biochar-modified hydrogel slow-release fertilizer (GQP@50BC) includes the following steps: (1) After washing and drying the sorghum stalks, crush them and pass them through a 100-mesh sieve. Then, put the stalk powder into a porcelain boat and pyrolyze it at 750°C for one hour in a tube furnace at a heating rate of 5°C / min. The resulting product is ground in an agate mortar and passed through a 100-mesh sieve to obtain sorghum stalk biochar.
[0025] (2) Add 5 g of polyvinyl alcohol 1799 to 45 mL of ultrapure water and stir at 85°C for 1 hour to obtain a polyvinyl alcohol solution; add 5 g of gelatin to 45 mL of ultrapure water and stir at 50°C for 1 hour to obtain a gelatin solution; add 5 g of quaternized chitosan to 45 mL of ultrapure water and stir at 60°C for 1 hour to obtain a quaternized chitosan solution; (3) Mix the three polymer solutions obtained in step (2) so that the dry matter mass concentrations of the three polymers are 3.3 wt%, 4.4 wt% and 4.4 wt%, respectively. Then add potassium nitrate and ammonium dihydrogen phosphate solutions and biochar at 50% relative to the dry mass of the polymers. Continue stirring at 60°C for 1 hour to obtain a mixed biochar gel solution. (4) Add 5 mL of genipin solution to the above mixed biochar gel solution to make its concentration 0.1%, and stir at 45°C for 0.5 hours; (5) After sonicating the solution in step (4) for 5 minutes, freeze it in a -20℃ freezer for 16 hours, and then thaw it at room temperature for 8 hours. Repeat this cycle 3 times to obtain the biochar-modified hydrogel slow-release fertilizer, named GQP@50BC. The nutrient content in the biochar-modified hydrogel slow-release fertilizer is 12.2% of the gel mass.
[0026] Example 2
[0027] A method for promoting vegetable growth using biochar-modified hydrogel slow-release fertilizer, specifically using biochar-modified hydrogel slow-release fertilizer as a fertilizer source to grow lettuce, includes the following steps: Take 1.0 g of nutrient-rich biochar-modified hydrogel slow-release fertilizer (named GQP@100BC) and add it to 200 g of soil. Mix well and water the soil thoroughly with ultrapure water. On the second day, 10 rapeseed seeds were sown in the soil and placed under environmental conditions for planting. After the seeds germinated, the seedlings were thinned when they had 2-3 true leaves, and then the seedlings were fixed when they had 4-5 true leaves, leaving 4 seedlings. After that, the seedlings were watered regularly and weeded and cultivated once a week. During the growth cycle, water management, pest and disease control, and weeding should be carried out as required. Harvesting begins when the plants grow to 15 cm in height.
[0028] In this embodiment, the preparation method of the biochar-modified hydrogel slow-release fertilizer (GQP@100BC) includes the following steps: (1) After washing and drying the sorghum stalks, crush them and pass them through a 100-mesh sieve. Then, put the stalk powder into a porcelain boat and pyrolyze it at 750°C for one hour in a tube furnace at a heating rate of 5°C / min. The resulting product is ground in an agate mortar and passed through a 100-mesh sieve to obtain sorghum stalk biochar.
[0029] (2) Add 5 g of polyvinyl alcohol 1799 to 45 mL of ultrapure water and stir at 85°C for 1 hour to obtain a polyvinyl alcohol solution; add 5 g of gelatin to 45 mL of ultrapure water and stir at 50°C for 1 hour to obtain a gelatin solution; add 5 g of quaternized chitosan to 45 mL of ultrapure water and stir at 60°C for 1 hour to obtain a quaternized chitosan solution; (3) Mix the three polymer solutions obtained in step (1) so that the dry matter mass concentrations of the three polymers are 3.3 wt%, 4.4 wt% and 4.4 wt%, respectively. Then add potassium nitrate and ammonium dihydrogen phosphate solutions and biochar at 100% relative to the dry mass of the polymers. Continue stirring at 60°C for 1 hour to obtain a mixed biochar gel solution. (4) Add 5 mL of genipin solution to the above mixed biochar gel solution to make its concentration 0.07%, and stir at 45°C for 0.5 hours; (5) After sonicating the solution in step (4) for 5 minutes, freeze it in a -20℃ freezer for 16 hours, and then thaw it at room temperature for 8 hours. Repeat this cycle 3 times to obtain the biochar-modified hydrogel slow-release fertilizer, named GQP@100BC. The nutrient content in the biochar-modified hydrogel slow-release fertilizer is 24.4% of the gel mass.
[0030] Example 3
[0031] A method for promoting vegetable growth using biochar-modified hydrogel slow-release fertilizer, specifically using biochar-modified hydrogel slow-release fertilizer as a fertilizer source to grow lettuce, includes the following steps: Add 4.0 g of nutrient-rich biochar-modified hydrogel slow-release fertilizer (named GQP@25BC) to 200 g of soil, mix well, and water the soil thoroughly with ultrapure water. On the second day, 10 spinach seeds were sown in the soil and placed under environmental conditions for planting; After the seeds germinate, thin the seedlings when they have 2-3 true leaves, and then thin them to 4 seedlings when they have 4-5 true leaves. After that, water them regularly and weed them once a week. During the growth cycle, water management, pest and disease control, and weeding should be carried out as required. Harvesting begins when the plants grow to 20 cm in height.
[0032] In this embodiment, the preparation method of the biochar-modified hydrogel slow-release fertilizer (GQP@25BC) includes the following steps: (1) After washing and drying the sorghum stalks, crush them and pass them through a 100-mesh sieve. Then, put the stalk powder into a porcelain boat and pyrolyze it at 750°C for one hour in a tube furnace at a heating rate of 5°C / min. The resulting product is ground in an agate mortar and passed through a 100-mesh sieve to obtain sorghum stalk biochar.
[0033] (2) Add 5 g of polyvinyl alcohol 1799 to 45 mL of ultrapure water and stir at 85°C for 1 hour to obtain a polyvinyl alcohol solution; add 5 g of gelatin to 45 mL of ultrapure water and stir at 50°C for 1 hour to obtain a gelatin solution; add 5 g of quaternized chitosan to 45 mL of ultrapure water and stir at 60°C for 1 hour to obtain a quaternized chitosan solution; (3) Mix the three polymer solutions obtained in step (1) so that the dry matter mass concentrations of the three polymers are 3.3 wt%, 4.4 wt% and 4.4 wt%, respectively. Then add potassium nitrate and ammonium dihydrogen phosphate solutions and biochar at 25% relative to the dry mass of the polymers. Continue stirring at 60°C for 1 hour to obtain a mixed biochar gel solution. (4) Add 5 mL of genipin solution to the above mixed biochar gel solution to make its concentration 0.1%, and stir at 45°C for 0.5 hours; (5) After sonicating the solution in step (4) for 5 minutes, freeze it in a -20℃ freezer for 16 hours, and then thaw it at room temperature for 8 hours. Repeat this cycle 3 times to obtain the biochar-modified hydrogel slow-release fertilizer, named GQP@25BC. The nutrient content in the biochar-modified hydrogel slow-release fertilizer is 6.1% of the gel mass.
[0034] Example 4
[0035] A method for promoting vegetable growth using biochar-modified hydrogel slow-release fertilizer, specifically using biochar-modified hydrogel slow-release fertilizer as a fertilizer source to grow lettuce, includes the following steps: Take 4.0 g of nutrient-rich biochar-modified hydrogel slow-release fertilizer (GQP@50BC, the same as in Example 1) and add it to 200 g of soil. Mix well and water the soil thoroughly with ultrapure water. On the second day, 10 lettuce seeds were sown in the soil and placed under environmental conditions for planting; After the seeds germinate, thin the seedlings when they have 2-3 true leaves, and then thin them to 4 seedlings when they have 4-5 true leaves. After that, water them regularly and weed them once a week. During the growth cycle, water management, pest and disease control, and weeding should be carried out as required. Harvesting begins when the plants grow to 15 cm in height.
[0036] Test Examples
[0037] To investigate the promoting effect of the biochar-modified hydrogel slow-release fertilizer of this invention on vegetable growth, potassium nitrate and ammonium dihydrogen phosphate were used to simulate the application of chemical fertilizers for comparison. Three fertilizer groups were set up, and vegetables were planted using the same method as in Examples 1-4 above. Among them, the nutrient content of the fertilizers applied to fertilizer groups 1, 2 and 3 was kept the same as in Examples 1-3.
[0038] In addition, in order to investigate the effects of the biochar-modified hydrogel slow-release fertilizer of the present invention on vegetable growth compared with unmodified hydrogel slow-release fertilizer and other biochar-modified hydrogel slow-release fertilizers, control groups 1-7 were set up. Vegetables were planted using the same method as in Examples 1-4 above. Among them, control groups 1, 2 and 3 used unmodified hydrogel slow-release fertilizer, and the nutrient content of the applied fertilizer was kept the same as in Examples 1-3.
[0039] Control groups 4 and 5 used biochar-modified calcium ion crosslinked alginate hydrogel slow-release fertilizer, the preparation method of which is as follows: Biochar was placed in a 0.1 mol / L calcium chloride solution and magnetically stirred for 30 min. After filtration, sodium alginate (3 wt%), potassium nitrate, and ammonium dihydrogen phosphate solution were added, and the mixture was allowed to stand for 30 min before being filtered again. The biochar composite hydrogel obtained after the second filtration was placed in a 0.8 mol / L calcium chloride solution, allowed to stand for 5 min, filtered, and washed to obtain the biomodified alginate hydrogel slow-release fertilizer.
[0040] The amounts of biochar and nutrients added in control groups 4 and 5 were the same as those in Examples 1 and 2, respectively.
[0041] Control groups 6 and 7 used biochar-modified polyacrylic acid hydrogel slow-release fertilizer, which was prepared as follows: Potassium nitrate and ammonium dihydrogen phosphate were mixed in a certain proportion and a salt solution was prepared using water as a solvent. Biochar was then added to the solution and stirred for 24 hours, followed by aging for 24 hours to obtain a biochar-based material containing nutrients. To prepare neutralized acrylic acid, 5.0 mL of acrylic acid solution was mixed with 10 mL of water at 0°C and stirred until homogeneous. Sodium hydroxide solution was then slowly added dropwise until 70% of the carboxyl groups in the acrylic acid were neutralized. The solution was then refrigerated for later use. A certain mass of biochar was added to water and stirred until homogeneous. The mixture was heated to 60°C, and 0.1050 g of ammonium persulfate was added until completely dissolved. The temperature was then raised to 85°C, and 10 mL of an acrylic acid solution with a neutralization degree of 70% and 0.0350 g of N,N-methylenebisacrylamide were added and stirred until homogeneous. The product was allowed to gel, and the temperature was maintained for 90 minutes. The resulting product was cooled, washed with water and ethanol, dried, and finally ground and sieved to obtain the material.
[0042] The amounts of biochar and nutrients added in control groups 6 and 7 were the same as in Examples 1 and 2, respectively.
[0043] After the vegetables were harvested (four plants per group), the fresh weight and dry weight of the edible parts were measured, and the results are shown in Table 1.
[0044] Table 1 Vegetable yield of each treatment group
[0045] As shown in Table 1, compared with the application of traditional chemical fertilizers, unmodified hydrogel slow-release fertilizers, and other biochar-modified hydrogel slow-release fertilizers, the application of the biochar-modified hydrogel slow-release fertilizer described in this patent significantly promotes the increase of fresh weight and dry weight of vegetables, which is beneficial to the increase of vegetable yield.
[0046] Specifically, comparing Example 1, fertilizer group 1, control group 1, control group 4, and control group 6, it can be seen that the application of the biochar-modified hydrogel slow-release fertilizer proposed in this invention increased the fresh weight of lettuce by 81.93%, 29.34%, 20.71%, and 16.27% compared to the application of traditional chemical fertilizers, unmodified biochar hydrogel slow-release fertilizers, and other biochar-modified hydrogel slow-release fertilizers, respectively; and increased the dry weight by 82.35%, 29.17%, 17.72%, and 13.41%, respectively. Comparing Example 2, fertilizer group 2, control group 2, control group 5, and control group 7, it can be seen that the application of the biochar-modified hydrogel slow-release fertilizer proposed in this invention increased the fresh weight of rapeseed by 106.76%, 21.43%, 7.94%, and 9.87% compared to the application of traditional chemical fertilizers, unmodified biochar hydrogel slow-release fertilizers, and biochar-modified hydrogel slow-release fertilizers prepared with other formulations; and increased the dry weight by 123.33%, 24.07%, 13.56%, and 9.84%, respectively. Comparing Example 3, Fertilizer Group 3, and Control Group 3, it can be seen that applying the biochar-modified hydrogel slow-release fertilizer proposed in this invention increases the fresh weight of spinach by 101.76% and 26.97% respectively compared to applying traditional chemical fertilizer and not using biochar-modified hydrogel slow-release fertilizer, and increases the dry weight by 89.47% and 28.57% respectively.
[0047] Furthermore, as shown in Examples 1 and 4, with the increase of the proportion of biochar-modified hydrogel slow-release fertilizer applied to the soil, its promoting effect on vegetable growth is further enhanced, with fresh weight and dry weight increasing by 29.46% and 35.48%, respectively.
[0048] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for promoting vegetable growth using biochar-modified hydrogel slow-release fertilizer, the method comprising mixing the biochar-modified hydrogel slow-release fertilizer with tilled soil, irrigating to moisten the soil and sowing seeds, harvesting the vegetables after a certain period of growth, and irrigating regularly during the period; The biochar-modified hydrogel slow-release fertilizer is obtained by freeze-thaw cycle treatment of a solution containing biochar, nutrients and polymers.
2. The method according to claim 1, wherein, The preparation method of the biochar-modified hydrogel slow-release fertilizer includes the following steps: S1. Polyvinyl alcohol, gelatin and quaternized chitosan are heated and stirred to dissolve separately, and then mixed and stirred in different proportions to prepare a polymer mixed solution; S2. Add nutrients and biochar to the polymer mixture, heat and stir, add crosslinking agent, continue heating and stirring to obtain a mixed biochar gel solution; S3. The mixed biochar gel solution is subjected to ultrasonic treatment and then subjected to three "freeze-thaw cycles" to obtain the biochar-modified hydrogel slow-release fertilizer.
3. The method according to claim 2, wherein, The method for preparing the biochar includes the following steps: First, the sorghum stalks are washed, dried, crushed, and sieved to obtain sorghum stalk powder. Then, the sorghum straw powder is pyrolyzed. After pyrolysis, it is ground and sieved to obtain sorghum straw biochar.
4. The method according to claim 2, wherein, The nutrients are nitrogen, phosphorus, and potassium nutrients in different forms, including at least one of ammonium nitrate, sodium nitrate, potassium nitrate, ammonium chloride, ammonium dihydrogen phosphate, potassium dihydrogen phosphate, sodium dihydrogen phosphate, potassium chloride, and urea.
5. The method according to claim 2, wherein, In the polymer mixture solution, the concentrations of polyvinyl alcohol, gelatin, and quaternized chitosan are 3.3 wt%, 4.4 wt%, and 4.4 wt%, respectively.
6. The method according to claim 2, wherein, The crosslinking agent is genipin or glutaraldehyde; in the mixed biochar gel solution, the concentration of the crosslinking agent is 0.05~0.1 wt%.
7. The method according to claim 2, wherein, In step S1, polyvinyl alcohol 1799 is added to water and heated and stirred at 80-95°C for 0.5-2 hours to obtain a polyvinyl alcohol solution. Gelatin powder is added to water and heated and stirred at 45-50°C for 0.5-1 hour to obtain a gelatin solution. Add quaternized chitosan powder to water and heat and stir at 50-70 ℃ for 1-3 hours to obtain quaternized chitosan solution; The polyvinyl alcohol solution, the gelatin solution, and the quaternized chitosan solution are mixed, and then heated and stirred at 50–70 °C for 0.5–1.5 hours.
8. The method according to claim 2, wherein, In step S3, the ultrasonic treatment time is 5 to 15 minutes; the freeze-thaw conditions are freezing at -40℃ to -10℃ for 8 to 16 hours, thawing at 4℃ to 30℃ for 8 to 16 hours, and repeating 3 times.
9. The method according to claim 1, wherein, The soil tillage depth is 10-20 cm; the amount of biochar-modified hydrogel slow-release fertilizer is calculated as follows: 0.5-2 wt% of dried biochar-modified hydrogel slow-release fertilizer per mu of cultivated land, based on a depth of 20 cm; the vegetables are one or more of lettuce, rapeseed, spinach, and romaine lettuce; the planting time is 1-3 months; the irrigation frequency is 1-2 times per week.
10. The method according to claim 9, wherein, The planting process includes the following steps: (1) Site selection and land preparation: Select a plot of land with good drainage, ventilation and light, and deep plow the plot before planting. Apply biochar modified hydrogel slow-release fertilizer according to the available soil quality of the plot, and water until the soil is completely moist. (2) Sowing: 2 to 3 days after the soil in step (1) has been watered, select vegetable seeds that are free from pests and diseases and have a high germination rate and sow them directly in the soil; (3) Seedling management: thinning, fixing, water management and weeding of vegetables; (4) Field management: Irrigation management, pest and disease control, and weeding throughout the entire growth cycle of vegetables; (5) Harvesting: When the vegetable plants grow to 15-30 cm in height, they can be harvested.