Modified biochar, seed coating agent and seed coating method for wetland vegetation restoration

Abstract

The invention provides modified biochar, a seed coating agent and a seed coating method for wetland vegetation restoration, and belongs to the technical field of wetland vegetation restoration, the modified biochar for seed coating comprises biochar, a microbial agent, a plant growth regulator and chitosan oligosaccharide; the mass ratio of the biochar to the microbial agent to the plant growth regulator to the chitosan oligosaccharide is (10-25): (0.1-0.5): (1-3): (5-10). The invention also provides a seed coating agent for wetland vegetation restoration. The seed coating agent comprises the modified charcoal, a binder and a filler, the mass ratio of the modified charcoal to the binder to the filler is (20-40): (5-15): (50-80). Pelleted seeds prepared by the seed coating agent provided by the invention can overcome high-strength water and sand dynamic changes of wetlands, especially coastal wetlands, and the seed germination rate and the plant stress resistance are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wetland vegetation restoration, and particularly relates to a modified biochar, a seed coating agent, and a seed coating method for wetland vegetation restoration. BACKGROUND

[0002] Wetlands are ecosystems that are constantly or seasonally waterlogged, with unique hydrological and biological characteristics, and usually include marshes, peatlands, rivers, lakes, and coastal wetlands. As one of the most productive ecosystems on Earth, wetlands not only provide important habitats for a variety of organisms, particularly for aquatic plants, fish, amphibians, and birds, but also play a crucial role in maintaining global biodiversity. The ecological functions of wetlands are very broad, including climate regulation, water purification, flood mitigation, soil protection, and carbon sequestration. However, the wetland environment, especially coastal wetlands, due to its unique geographical location and dynamic water-sediment conditions, often presents complex hydrological changes. This complex water-sediment dynamics, which is usually manifested as the alternation of tides, wave action, and sediment deposition and erosion, not only increases the diversity of the wetland environment, but also poses challenges to plant growth, especially to wetland plants. As a key step in the life cycle of plants, seed colonization and germination are significantly affected by water-sediment conditions.

[0003] The expansion and propagation of vegetation seeds and propagules are the core steps in the process of wetland vegetation restoration, especially for annual plants commonly found in wetlands, it is particularly important to maintain the size of the population similar to the previous year. When wetland vegetation degrades, the local biological community often lacks sufficient seed sources and suitable soil environments to support the natural colonization of plant communities the following year. Therefore, it is necessary to restore vegetation by artificially supplementing seeds and seedlings. Common wetland vegetation restoration measures include seeding, plant variety selection, and transplanting, which promote the restoration of local vegetation communities by expanding and propagating plant seeds and propagules. However, in coastal wetlands, due to frequent tides and water level fluctuations, seeds are often washed away or buried before they germinate or take root, hindering the natural restoration and expansion of vegetation. This not only affects the structure and dynamics of the wetland plant community, but also weakens the ecological functions of the wetland, making it face more severe survival challenges. Therefore, there is an urgent need to design a coating technology that is more suitable for wetland vegetation restoration in response to the complex water-sediment dynamic process of wetlands.

[0004] Pellet seed technology refers to the process of coating small or irregularly shaped seeds with a protective layer of material to form regular pellets. The purpose of this technology is to increase the weight and volume of the seeds, improve their seeding performance, and is particularly suitable for mechanical seeding. The coating material for pelleting usually includes nutrients, moisturizers, fungicides, etc. to improve the germination rate, disease resistance, and survival rate of the seeds. Pellet seed technology is widely used in agriculture and ecological restoration, and can effectively promote the uniform distribution and planting of seeds, especially in environments with poor soil conditions. However, the addition of nutrients and fungicides in traditional pellet seeds increases the ecological and environmental risks of coating products, which is contrary to the purpose of wetland vegetation restoration. Therefore, it is necessary to improve the existing pelleting coating technology and use more environmentally friendly methods to produce seed coating products to better meet the actual needs of wetland vegetation restoration. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a modified biochar, a seed coating agent, and a seed coating method for wetland vegetation restoration. The pellet seed provided by the present application can overcome the high intensity of water and sand dynamic changes in wetlands, especially coastal wetlands, and improve seed germination rate and plant stress resistance. At the same time, the present application is based on modified biochar, with less addition of synthetic substances, reducing the negative environmental effects in the practice process.

[0006] The present application provides a modified biochar for seed coating, comprising biochar, microbial agent, plant growth regulator and chitosan oligosaccharide; the mass ratio of the biochar, microbial agent, plant growth regulator and chitosan oligosaccharide is 10-25:0.1-0.5:1-3:5-10.

[0007] Preferably, the microbial agent is Bacillus licheniformis or Trichoderma harzianum; the plant growth regulator is brassinolide.

[0008] The present application provides a preparation method of the modified biochar, characterized by comprising the following steps: 1) mixing biochar, microbial agent, plant growth regulator and chitosan oligosaccharide to obtain a biochar mixture; 2) mixing the biochar mixture with water, standing, and drying to obtain the modified biochar.

[0009] Preferably, the mass ratio of the biochar mixture to water is 1:(3-7), the standing temperature is 18-22℃, and the standing time is 20-30h.

[0010] The present application provides a seed coating agent for wetland vegetation restoration, comprising the modified biochar, a binder and a filler; the mass ratio of the modified biochar, the binder and the filler is 20-40:5-15:50-80.

[0011] Preferably, the filler comprises bentonite and clay, and the mass ratio of the bentonite and the clay is 10-20:20-50; the binder comprises chitosan and sodium carboxymethyl cellulose, and the mass ratio of the chitosan and the sodium carboxymethyl cellulose is 6-9:1-4.

[0012] Preferably, the filler further comprises calcium peroxide, and the mass ratio of the calcium peroxide, the bentonite and the clay is 0.1-5:10-20:20-50.

[0013] The application further provides a seed coating method for wetland vegetation restoration, comprising the following steps: a) spraying water on the surface of the seeds to wet them, and coating the seeds with the seed coating agent to obtain pelletized seeds; b) drying the coated pelletized seeds and sieving them.

[0014] Preferably, the seeds are wetland plant seeds with a diameter of ≦10 mm.

[0015] Preferably, when the diameter of the seeds is ≦3 mm, a single pelletized seed comprises multiple seeds.

[0016] Compared with the prior art, the application has the following beneficial effects: the modified biochar provided by the application for seed coating comprises biochar, microbial inoculum, plant growth regulator and chitooligosaccharide; on the basis of the biochar serving as a carrier to adsorb biochemical components, the porous structure of the modified biochar can improve the air permeability of the microenvironment and the composition of the plant rhizosphere microbial community; the microbial inoculum can secrete various plant hormones, promote the development of crop root systems and improve the stress resistance of plants; meanwhile, the microbial inoculum can increase the supply of nutrients and further promote the recycling of important elements such as carbon, nitrogen and phosphorus. The plant growth regulator can enhance the stress resistance of plants and help the plants maintain normal physiological functions in adverse environments; the chitooligosaccharide is a low-molecular-weight oligosaccharide with good water solubility, which can enhance the disease resistance and stress resistance of plants, and the residues can be gradually degraded by microorganisms, thereby being environmentally friendly.

[0017] The seed coating agent for wetland vegetation restoration provided by the application comprises the modified biochar, a binder and a filler; after the seed coating agent is used to coat the seeds, pelletized seeds are formed; the pelletized seeds can form microtopography on wetland beaches and reduce the disturbance to propagules when the water level changes rapidly; the addition of the filler in the pelletized seeds enhances the water absorption capacity of the pelletized seeds.

[0018] The materials of the seed coating agent are easy to obtain and low in cost, and the modified biochar can be quickly granulated after being prepared, thereby being convenient for storage and transportation.

[0019] The pellets provided by this invention are similar in size to grain crops such as corn and soybeans, requiring minimal modification to the sowing equipment and allowing for large-scale operations. Attached Figure Description

[0020] Figure 1 Image of pelleted seed sample; Figure 2 This is a diagram showing the germination results of pelleted seeds in Example 3. Detailed Implementation

[0021] This invention provides a modified biochar for seed coating, comprising biochar, microbial inoculant, plant growth regulator and chitosan oligosaccharide; wherein the mass ratio of biochar, microbial inoculant, plant growth regulator and chitosan oligosaccharide is 10~25:0.1~0.5:1~3:5~10.

[0022] In this invention, the modified biochar used for seed coating comprises biochar. This invention does not have a special limitation on the source of the biochar, and biochar from conventional sources in the art can be used. In this invention, the biochar is preferably crushed, ground, and sieved before use. This invention does not have a special limitation on the specific method of crushing and grinding, and conventional methods in the art can be used. In this invention, the sieve mesh size is preferably 200 mesh, and this invention preferably collects the undersize components.

[0023] In this invention, the modified biochar includes a microbial inoculant, preferably a Bacillus licheniformis inoculant or a Trichoderma harzianum inoculant. More preferably, when used for seed coating in ordinary wetlands, the microbial inoculant is preferably a Bacillus licheniformis inoculant. In this invention, Bacillus licheniformis can secrete various plant hormones such as plant growth hormones and gibberellins, promoting crop root development and improving plant stress resistance and yield. Bacillus licheniformis can decompose organic matter, increasing nutrient supply in the soil. The life activities of Bacillus licheniformis release gases such as carbon dioxide, improving soil structure and fertility, and further promoting the recycling of important elements such as carbon, nitrogen, and phosphorus. Bacillus licheniformis exhibits excellent adaptability under strong stress environments, helping plants enhance their resistance to drought, salinity, and other adverse conditions. When used for seed coating in saline-alkali wetlands, the microbial inoculant is preferably a Trichoderma harzianum inoculant. In this invention, the bacterial concentration of the Bacillus licheniformis inoculant is preferably 5 × 10⁻⁶. 10 ~1×10 12 cfu / g, further preferably (1~9)×10 11 cfu / g.

[0024] In this invention, the modified biochar includes plant growth regulators. Preferably, the plant growth regulator is brassinolide, a brassinosteroid plant endogenous hormone. Brassinolide can enhance plant resistance to environmental stresses such as drought, salinity, high temperature, and low temperature, helping plants maintain normal physiological functions in adverse environments. Furthermore, compared to traditional plant growth regulators, brassinolide has lower biotoxicity and is more environmentally friendly.

[0025] In this invention, the modified biochar includes chitosan oligosaccharide, which is a low-molecular-weight oligosaccharide with good water solubility. Chitosan oligosaccharide is a novel organic agricultural additive that enhances plant disease resistance and stress tolerance, while its residues are gradually degraded by microorganisms, making it environmentally friendly. This invention, through modification of biochar, provides a carbon source for microbial agents while achieving the slow release of nutrients.

[0026] In this invention, the mass ratio of biochar, microbial inoculant, plant growth regulator and chitosan oligosaccharide is 10~25:0.1~0.5:1~3:5~10, preferably 12~22:0.2~0.5:1.5~2.5:6~9, and more preferably 20:0.5:2:7.5.

[0027] The present invention also provides a method for preparing the modified biochar, characterized by comprising the following steps: 1) mixing biochar, microbial inoculant, plant growth regulator and chitosan oligosaccharide to obtain a biochar mixture; 2) mixing the biochar mixture with water, allowing it to stand, and air-drying it to obtain modified biochar.

[0028] In this invention, biochar, microbial inoculants, plant growth regulators, and chitosan oligosaccharides are mixed to obtain a biochar mixture. Preferably, the biochar is pulverized, ground, and sieved. This invention does not specifically limit the pulverization and grinding methods; conventional methods in the art can be used. Preferably, the sieve mesh size is 200 mesh, and the undersize components are collected. After mixing the above raw materials, a mixer is preferably used for stirring. The stirring power is preferably 400-600W, more preferably 450-550W, and even more preferably 500W. The stirring time is 8-12 minutes, more preferably 10 minutes.

[0029] In this invention, after obtaining a biochar mixture, the biochar mixture is mixed with water, allowed to stand, and then air-dried to obtain modified biochar. In this invention, the mass ratio of the biochar mixture to water is preferably 1:(3~7), more preferably 1:(4~6), and even more preferably 1:5; the water is preferably distilled water; the standing temperature is preferably 18~22℃, more preferably 19~21℃, and even more preferably 20℃, and the standing time is preferably 20~30h, more preferably 22~28h, and even more preferably 24~26h. After standing, the biochar is removed and air-dried to obtain modified biochar; the air-drying is preferably natural air-drying, the air-drying temperature is preferably 18~20℃, and the air-drying time is preferably 20~28h, and even more preferably 22~26h. Furthermore, the modified biochar obtained by this invention is preferably stored in a dry (humidity controlled below 30%) and low-temperature environment; the low-temperature storage temperature is preferably 3~5℃.

[0030] This invention provides a seed coating agent for wetland vegetation restoration, comprising the modified biochar, binder, and filler; the mass ratio of the modified biochar, binder, and filler is 20~40:5~15:50~80.

[0031] In this invention, the seed coating agent includes a binder comprising chitosan and sodium carboxymethyl cellulose. The preferred mass ratio of chitosan to sodium carboxymethyl cellulose is 6-9:1-4, more preferably 7-8:2-3. In this invention, chitosan serves as an auxiliary binder component. Chitosan is a natural polymer material with good biocompatibility, biodegradability, and bioactivity. As a natural binder, chitosan thickens and viscous the seeds, reducing the amount of sodium carboxymethyl cellulose required and enhancing seed mechanical properties. Chitosan also has a certain promoting effect on plant growth, improving soil structure, promoting soil microbial activity, regulating plant growth and development, and enhancing crop resistance. Chitosan can also serve as a coating agent, used for coating after seed pelleting to enhance mechanical properties. In this invention, sodium carboxymethyl cellulose is a carboxymethylated derivative of cellulose and is the most important ionic cellulose gum, capable of enhancing the mechanical properties of seed pellets and ensuring tight binding of the components in the coating agent.

[0032] In this invention, the seed coating agent further includes a filler comprising bentonite and clay. The preferred mass ratio of bentonite to clay is 10-20:20-50, more preferably 12-18:25-45, and even more preferably 15:30. In this invention, the bentonite has a particle size of 200 mesh. Bentonite is a natural clay mineral with montmorillonite as its main component. Bentonite possesses high water absorption, excellent ion exchange capacity, and good soil amendment effects. As a supplementary component to the filler, it enhances the water retention performance of the filler and, as a soil conditioner, appropriately alters the local soil permeability.

[0033] The clay used in this invention is preferably dried, pulverized, and sieved, with the fraction passing through a 100-mesh sieve. The clay can be selected from local in-situ soil or any wetland soil with similar natural conditions. This invention increases the weight of the pelleting coating by adding clay, enhancing its resistance to water flow disturbance. Furthermore, clay has a strong water retention capacity, enhancing the water retention ability of the pelleted seeds.

[0034] The present invention preferably obtains the filler by mixing and stirring bentonite and clay, and the stirring time is preferably 15-25 minutes. In the present invention, the filler preferably also includes calcium peroxide, and the mass ratio of calcium peroxide, bentonite and clay is 0.1-5:10-20:20-50, wherein the calcium peroxide is used as an oxygenating agent.

[0035] In this invention, the mass ratio of the modified biochar, binder, and filler is 20-40:5-15:50-80, preferably 25-35:8-12:55-70, and more preferably 30:10:60. Preferably, the modified biochar, binder, and filler are mixed in the specified mass ratio and then stirred to obtain the seed coating agent. The stirring is carried out in a mixer, and the stirring time is preferably 15-25 minutes.

[0036] The present invention also provides the seed coating method for wetland vegetation restoration, comprising the following steps: a) Moisten the seed surface with water, and coat the seeds with the seed coating agent to obtain pellet seeds; b) Dry the coated pellets and sieve them.

[0037] In this invention, the seed surface is moistened by spraying water, with a seed-to-water ratio of 10:1. The seed coating agent is then used to coat the seeds to obtain pelleted seeds. Specifically, the seeds are first placed on a turntable, preferably with the turntable speed set to 45-55 r / min. While the turntable is rotating, water is sprayed onto the seed surface, and then the seed coating agent is added in small amounts multiple times, with water sprayed simultaneously with the addition of the seed coating agent, at a coating agent-to-water ratio of 15:1. After the seed surface is evenly coated with a layer of seed coating agent, the speed is increased to 100 r / min and maintained for 15-30 minutes, preferably for 20-25 minutes.

[0038] In this invention, the coated seed pellets are dried and then sieved. Preferably, the sieving is done through a 10-mesh sieve, and the purpose of sieving is to remove clumps of coating agent particles that are not coated with seeds.

[0039] In this invention, the seeds are preferably wetland plant seeds with a diameter of ≤10mm, and more preferably seeds of Suaeda salsa, reeds or wild soybeans.

[0040] In this invention, when the seed diameter is ≤3mm, a single pellet seed includes multiple seeds.

[0041] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] Preparation of modified biochar

[0044] The selected microbial agent was Bacillus licheniformis (a commercially available product, purchased from Beihai Yeshengwang Biotechnology Co., Ltd., fully water-soluble Bacillus licheniformis), with a bacterial concentration of 1×10⁻⁶. 11 cfu / g.

[0045] The selected biochar (commercially available, reed biochar) was pulverized and ground (using a small medical blender, 550W power) for 10 minutes, then passed through a 200-mesh sieve, and the sieved components were selected for later use.

[0046] In this embodiment, biochar, brassinolide, Bacillus licheniformis inoculant, and chitosan oligosaccharide were mixed in a mass ratio of 20:0.5:2:7.5 and stirred for 10 minutes with a mixer (500W) until homogeneous to obtain a biochar mixture.

[0047] The biochar mixture was mixed with distilled water at a mass ratio of 1:5 and allowed to stand at 20°C for 24 hours.

[0048] The soaked biochar was then removed and naturally air-dried for 24 hours under ventilated conditions at 20°C to obtain modified biochar, which was then stored under dry conditions at 4°C.

[0049] Example 2

[0050] Preparation of seed coating agent

[0051] Filler preparation

[0052] Bentonite and clay are mixed at a mass ratio of 20:40 and stirred in a mixer for 20 minutes until uniform, thus obtaining the filler.

[0053] Adhesive preparation

[0054] Chitosan and sodium carboxymethyl cellulose were mixed at a mass ratio of 8:2 and stirred in a mixer for 10 minutes until homogeneous to obtain the adhesive.

[0055] The binder, filler, and modified biochar prepared in Example 1 were mixed at a mass ratio of 30:10:60 and stirred in a mixer for 20 minutes until uniformly mixed to obtain the seed coating agent.

[0056] Example 3

[0057] This embodiment uses wild soybean ( Glycine soja Siebold & Zucc. () as the proposed implementation target.

[0058] Pretreatment of experimental materials

[0059] After the collected wild soybean seeds are naturally dried, rinse them with distilled water for 1-2 minutes to remove the dust.

[0060] Rinse wild soybean seeds in saline soil with a 0.1% potassium permanganate solution for 3 minutes, then rinse three times with deionized water and soak in distilled water at 25°C for 24 hours to promote germination.

[0061] The clay collected from the site to be restored was dried in an oven at 180°C for 24 hours. After cooling to 25°C, it was crushed and ground for 15 minutes, passed through a 100-mesh sieve, and the sieve-underfilled components were retained. Filler preparation Bentonite and clay are mixed at a mass ratio of 20:40 and stirred in a mixer for 20 minutes until uniform, thus obtaining the filler.

[0062] Adhesive preparation

[0063] Chitosan and sodium carboxymethyl cellulose were mixed at a mass ratio of 8:2 and stirred in a mixer for 10 minutes until homogeneous to obtain the adhesive.

[0064] Preparation of pelleted seeds

[0065] In this embodiment, a variable speed turntable (the turntable is composed of a steel basin welded from an electric potter's wheel) is used for coating (20~300 r / min).

[0066] In this embodiment, the mass ratio of wild soybean seeds, modified biochar, binder, and filler is 30:30:10:60.

[0067] In this embodiment, the adhesive, filler, and modified biochar prepared in Example 1 are mixed in a mass ratio and stirred in a mixer for 20 minutes until uniform.

[0068] Place the seeds on a disc, adjust the rotation speed to 50 r / min, then spray a small amount of distilled water evenly on the seed surface. Add the mixed seed coating agent in small amounts several times while spraying water. Once the seed surface is evenly coated with a layer of seed coating agent, increase the rotation speed to 100 r / min.

[0069] After drying the coated seeds, pass them through a 10-mesh sieve to remove any clumps of coating agent that are not coated with the seeds.

[0070] The pellet seeds prepared in this embodiment are as follows: Figure 1 As shown.

[0071] Example 4

[0072] Germination experiment of pelleted seeds under salt stress; Wild soybean pellets prepared in Example 3 were used for the experiment. The experiment included three treatments: a control group (CK) of uncoated wild soybean seeds, and experimental groups of coated wild soybean seeds (Coated without Biochar) and Coated wild soybean seeds (Coated with Biochar), with five replicates per group. The experiment was conducted in a climate chamber at a temperature of 25℃±2℃ with uniform light throughout the day. Collected soil was allowed to air dry slightly before being filled into 9cm diameter seedling pots, with a soil layer thickness of 5-6cm. Fifty wild soybean seeds (approximately 15g) were coated according to the method in Example 3, and the prepared pellets were directly sprinkled into the seedling pots. Five replicates were set up for each group. Water the seeds with a certain amount of distilled water at 6:00 AM and 6:00 PM every day (six water volume gradients: 0ml, 5ml, 10ml, 15ml, 20ml, and 25ml). Record the number of germinations at 4:00 PM. Germination is considered to occur when the soybean seeds break through the seed coat. Continue this process for 15 days.

[0073] The results are as follows Figure 2 As shown, the experimental results indicate that: Under natural conditions, the seed germination rate increases with increasing moisture content and remains essentially unchanged under high moisture conditions. Pelleted seeds with added modified biochar can maintain a high germination rate even under low moisture conditions, while the germination rate of pelleted seeds without added modified biochar decreases to some extent.

[0074] As can be seen from the above embodiments, the pellet seeds provided by the present invention can overcome the high-intensity dynamic changes of water and sand in wetlands, especially coastal wetlands, and improve seed germination rate and plant stress resistance.

[0075] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A modified biochar for seed coating, characterized in that, The biochar, the microbial agent, the plant growth regulator and the chitosan oligosaccharide are mixed to obtain a biochar mixture.

2. The modified biochar of claim 1, wherein, The microbial agent is bacillus licheniformis or trichoderma harzianum.

3. The method of producing a modified biochar according to claim 1 or 2, characterized in that, The method comprises the following steps: 1) mixing biochar, microbial agent, plant growth regulator and chitosan oligosaccharide to obtain a biochar mixture; 2) mixing the biochar mixture with water, standing, and air-drying to obtain modified biochar.

4. The production method according to claim 3, characterized by, The mass ratio of the biochar mixture to water is 1: (3-7), the standing temperature is 18-22℃, and the standing time is 20-30h.

5. A seed coating agent for wetland vegetation restoration, characterized by, The modified biochar, the binder and the filler are mixed to obtain the seed coating agent.

6. The seed coating agent according to claim 5, characterized in that, The filler comprises bentonite and clay, and the mass ratio of the bentonite to the clay is 10-20:20-50.

7. The seed coating agent according to claim 6, characterized in that The binder comprises chitosan and sodium carboxymethyl cellulose, and the mass ratio of the chitosan to the sodium carboxymethyl cellulose is 6-9:1-4.

8. A method for seed coating for wetland vegetation restoration, characterized by, The filler further comprises calcium peroxide, and the mass ratio of the calcium peroxide to the bentonite to the clay is 0.1-5:10-20:20-50. The method comprises the following steps: a) spraying water on the surface of the seeds to wet them, and coating the seeds with the seed coating agent of claim 5 or 6 to obtain pelletized seeds; 9. The seed coating method according to claim 8, characterized in that, b) drying the obtained pelletized seeds and sieving them.

10. The method of coating seeds according to claim 8, characterized in that, The seeds are wetland plant seeds with a diameter of ≦10mm. When the diameter of the seeds is ≦3mm, a single pelletized seed comprises multiple seeds. The method comprises the following steps: 1) mixing biochar, microbial agent, plant growth regulator and chitosan oligosaccharide to obtain a biochar mixture; 2) mixing the biochar mixture with water, standing, and air-drying to obtain modified biochar. The mass ratio of the biochar mixture to water is 1: (3-7), the standing temperature is 18-22℃, and the standing time is 20-30h. The modified biochar, the binder and the filler are mixed to obtain the seed coating agent. The filler comprises bentonite and clay, and the mass ratio of the bentonite to the clay is 10-20:20-50. The binder comprises chitosan and sodium carboxymethyl cellulose, and the mass ratio of the chitosan to the sodium carboxymethyl cellulose is 6-9:1-4. The filler further comprises calcium peroxide, and the mass ratio of the calcium peroxide to the bentonite to the clay is 0.1-5:10-20:20-50. The method comprises the following steps: a) spraying water on the surface of the seeds to wet them, and coating the seeds with the seed coating agent of claim 5 or 6 to obtain pelletized seeds; b) drying the obtained pelletized seeds and sieving them. The seeds are wetland plant seeds with a diameter of ≦10mm. When the diameter of the seeds is ≦3mm, a single pelletized seed comprises multiple seeds.

Images