Colloid biochar as well as preparation method and application thereof

Abstract

The invention discloses colloidal biochar as well as a preparation method and application thereof. The colloidal biochar disclosed by the invention is colloidal biochar with a particle size of 400 to 1000 nm. The colloidal biochar is prepared by the following method: mixing and stirring biochar and water, heating and emulsifying to obtain the colloidal biochar. The soil conditioner comprises the colloidal biochar and a fertilizer. The soil conditioner disclosed by the invention is applied to grassland. The particle size of the colloidal biochar reaches the colloidal level, the dosage of the colloidal biochar is reduced by 50% or above compared with that of large-particle biochar, and meanwhile the fertilizer efficiency is more remarkable.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural ecology, and specifically relates to colloidal biochar and a preparation method and application thereof. Background Art

[0002] Biochar-based fertilizer is a type of fertilizer made from biochar as the main raw material. It has attracted widespread attention because of its good soil improvement and crop yield-increasing effects in the soil. However, there are several problems in the current process of applying biochar-based fertilizer to improve soil: (1) Fertilization method: Traditional biochar-based fertilizers are applied on the surface and then mixed into the soil by plowing. This method is not only time-consuming and labor-intensive, but also increases water loss during plowing in drought conditions. In areas of soil erosion or wind erosion, the soil after plowing is in a loose state, which is prone to water erosion or wind erosion. At the same time, since grasslands and woodlands are usually not plowed, biochar-based fertilizers have poor fertilizer efficiency after being applied to grasslands and woodlands, and are prone to loss. (2) Texture problem: Traditional biochar-based fertilizers are light in texture. After being applied on the soil surface, they are easily blown away by the wind or flow with water, resulting in certain losses, thus affecting the application effect. (3) Application amount and cost problem: Traditional biochar-based fertilizers are applied in large amounts, mostly 1%-3% of the soil mass, and the cost is relatively high. Taking grassland as an example, in order to avoid damaging the grass root system, biochar is mostly applied to grassland soil by surface spreading. However, since there is no shelter on the grassland, traditional biochar-based fertilizers are easily blown away by the wind and cannot act on the lower soil, resulting in low utilization efficiency. Therefore, some improvements need to be made to biochar.

[0003] Colloidal biochar is obtained by decomposing, crushing or precipitating large-particle biochar. The particle size is at the colloidal level and has unique physical and chemical properties, including high porosity, high specific surface area and cation exchange capacity. Due to its small particles and more negative charges, colloidal biochar has good migration ability in the soil. When colloidal biochar is applied to the surface soil, it can migrate to the lower soil with water under the action of precipitation, irrigation, etc. to play a role. Based on these advantages, colloidal biochar particles are expected to become a very promising soil conditioner that can provide innovative solutions for agricultural production and environmental protection.

[0004] At present, colloidal biochar is mostly used in the study of environmental benefits, and colloidal biochar is rarely used in combination with other nutrients as fertilizers and soil conditioners, and applied to soils such as farmland and grassland. Therefore, the production of colloidal biochar through a simple, rapid, and large-scale preparation method, combined with other nutrients according to soil needs, provides a new fertilization idea for soil nutrient provision, improvement, and management. Summary of the invention

[0005] The purpose of the present invention is to provide a colloidal biochar with low addition amount for promoting growth and improving quality and its preparation method and application. The colloidal biochar raw materials of the present invention are widely available and low in cost, the preparation method is simple to operate, can be mass-produced and promoted, and no pollutants are generated during the preparation process.

[0006] The present invention provides a colloidal biochar, wherein the particle size of the colloidal biochar is 400-1000 nm.

[0007] In the present invention, the pH of the colloidal biochar is 9.94 and the conductivity is 2.55 mS / cm.

[0008] In the colloidal biochar mentioned above, the colloidal biochar is prepared by the following method: biochar and water are mixed and stirred, and heated and emulsified to obtain the colloidal biochar.

[0009] In the colloidal biochar mentioned above, the raw material of the biochar is selected from at least one of wheat straw, corn straw, rice straw, sawdust, branches and leaves, and bark; The mass ratio of the biochar of the colloidal biochar to the water may be 1:5-40; The temperature of the heating emulsification can be 85-95° C., and the time can be 30-120 min.

[0010] In the present invention, the stirring is carried out in an electrically heated emulsifying stirring tank.

[0011] The present invention also provides a method for preparing the colloidal biochar, comprising the following steps: mixing and stirring the biochar and water, and heating and emulsifying the mixture to obtain the colloidal biochar; In the above method, the mass ratio of the biochar to the water may be 1:5-40; The temperature of the heating emulsification can be 85-95° C., and the time can be 30-120 min.

[0012] In addition, the preparation method of the biochar in the present invention is as follows: collect biochar raw materials, dry the raw materials, and then oxygen-limited pyrolysis at 450° C. for 1 h, and after cooling, crush and sieve the biochar with a pulverizer to obtain the biochar.

[0013] The present invention also provides a soil conditioner, comprising the colloidal biochar and fertilizer.

[0014] The soil conditioner comprises the following components in parts by weight: 2 parts of colloidal biochar; 0.03-0.08 parts of diammonium phosphate fertilizer; and 0.03-0.08 parts of urea fertilizer.

[0015] In the present invention, the soil conditioner is specifically composed of the following components by mass: 2 parts of colloidal biochar; 0.066 parts of diammonium phosphate fertilizer; 0.066 parts of urea fertilizer The present invention further provides application of the above-mentioned soil conditioner in grassland.

[0016] In the above application, the grassland is soil for growing alfalfa.

[0017] In the above application, the total application amount of the soil conditioner is 2-5 g per kilogram of grassland soil.

[0018] In the above application, the application amount of the soil conditioner per kilogram of grassland soil is specifically 2 g of colloidal biochar; 0.066 g of diammonium phosphate fertilizer; and 0.066 g of urea fertilizer.

[0019] The present invention has the following advantages: 1. The colloidal biochar of the present invention has a particle size of colloidal level, and is distributed on the soil surface with water when applied, and is not easily blown away by wind. At the same time, it does not need to be turned into the soil through tillage, and can be migrated to the lower soil layer with rainfall or irrigation water.

[0020] 2. Since the colloidal biochar of the present invention has a high specific surface area, it can more effectively absorb nutrients and reduce nutrient loss. When used in combination with inorganic fertilizers, it can significantly increase the fresh weight and dry weight of the aboveground and underground parts of the plant, as well as the nitrogen and phosphorus content in the plant.

[0021] 3. The colloidal biochar of the present invention reduces the amount of biochar used by more than 50% compared with large-particle biochar, and has a more significant fertilizer effect.

[0022] 4. After being applied to the soil surface, the colloidal biochar of the present invention can enter the soil, help activate the available phosphorus in the soil, provide good nutrient conditions for plant growth, and promote carbon fixation in deep soil (30-40 cm).

[0023] 5. The colloidal biochar preparation method of the present invention is simple to operate, saves time and labor, and its raw materials are easy to obtain and the usage is low, which significantly reduces the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the particle size distribution range of colloidal biochar at different preparation times.

[0025] Figure 2 The effect of colloidal biochar and large particle biochar on NH4 + -N adsorption capacity comparison.

[0026] Figure 3 The growth of alfalfa seedlings in sand under different treatments.

[0027] Figure 4 Germination rate and relative chlorophyll content of alfalfa seedlings under different treatments.

[0028] Figure 5 Fresh weight and dry weight of aboveground and underground parts of alfalfa seedlings under different treatments.

[0029] Figure 6 The stem length and root length of alfalfa seedlings under different treatments.

[0030] Figure 7 Schematic diagram of the growth status of alfalfa under different treatments.

[0031] Figure 8 Fresh weight and dry weight of aboveground and underground parts of alfalfa under different treatments.

[0032] Fig. 9 Plant height and total root length of alfalfa under different treatments.

[0033] Fig.10 Nitrogen and phosphorus contents in the aboveground and underground parts of alfalfa under different treatments.

[0034] Fig.11 is the available phosphorus content in soil under different treatments.

[0035] Fig.12 Schematic diagram of the growth status of alfalfa under different treatments.

[0036] Fig.13 Fresh weight and dry weight of aboveground part of alfalfa under different treatments.

[0037] Fig.14 is the content of total organic carbon and soluble organic carbon in soil profile under different treatments. DETAILED DESCRIPTION

[0038] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0039] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0040] The present invention provides a method for preparing colloidal biochar, which has the advantages of simple preparation, small amount of biochar used, and low price, and comprises the following preparation steps: 1) Collect the biochar raw materials, wash and dry them, and then oxygen-limited pyrolysis them at 450℃ for 1 h. After cooling, use a pulverizer to crush the biochar through a 2 mm sieve to obtain large-particle biochar; 2) The prepared biochar and water were mixed at a ratio of 1:20 (w / w) and poured into an electric heating emulsification stirring tank (Wenzhou Qiangzhong Machinery Technology, Zhejiang Province). The mixture was heated and emulsified at 90 °C for 30 min to obtain colloidal biochar with a particle size of 400-1000 nm.

[0041] In the following examples, large particle biochar and colloidal biochar were prepared by the above method.

[0042] Example 1 The biochar raw material (wheat straw) was pyrolyzed at 450℃ for 1 h and then passed through a 2 mm sieve to obtain large-particle biochar. The biochar and water were mixed at a ratio of 1:20 (w / w) and poured into an electric heating emulsification stirring tank (Wenzhou Qiangzhong Machinery Technology, Zhejiang), and heated and emulsified at 90℃ for 30-120 min to obtain colloidal biochar.

[0043] Adsorption isotherm determination: The concentration of colloidal biochar and biochar was 1000 mg / L, and different concentration gradients of NH4 + -N (0.07-562 mg / L), after mixing, constant temperature oscillation was carried out at 25°C and 180 r / min for 24 hours, and the NH4 content of the solution was determined by flow analyzer after filtration. + The Langmuir model was used to fit the data.

[0044] like Figure 1 As shown in the figure, the preparation time in the electric heating emulsification stirring tank has little effect on the particle size of the colloidal biochar. The particle size distribution of the colloidal biochar within the preparation time of 30-120 min is between 400-1000 nm, and the average particle size is about 600-700 nm. Compared with large-particle biochar (particle size <2 mm), the colloidal biochar has a smaller particle size, which is conducive to its movement in the soil.

[0045] Figure 2 The results show that the colloidal biochar and large particle biochar have a great influence on the NH4 + -N adsorption capacity comparison, Table 1 lists the two biochars for NH4 + The results show that the Langmuir model can better fit the experimental data. With the increase of solution equilibrium concentration, the adsorption of NH4 + The adsorption of -N gradually increased and then stabilized. + The adsorption of -N was 49.51% higher than that of large-particle biochar, which indicates that colloidal biochar has a stronger adsorption effect on nutrients, can reduce the loss and migration of nutrients in the soil, and can play a role in slow-release of nutrients to better maintain soil fertility.

[0046] Compared with large-particle biochar, the colloidal biochar of the present invention carries more negative charge and has a more negative zeta potential (Table 1). This is related to the larger specific surface area and more exposed charge sites of the colloidal biochar. The colloidal biochar carries more negative charge, which helps to adsorb more nutrients and migrate downward in the soil, thereby exerting an effect on deeper soil layers.

[0047] Table 1 Zeta potential of colloidal biochar and large particle biochar and their NH4 + Fitting parameters of -N adsorption

[0048] Example 2 Sand column test: 150 g of sand was weighed and put into a transparent plastic cup. Fertilizer was applied according to the mass of the sand. The amount of colloidal biochar prepared in Example 1 of the present invention was 2 g / kg, the amount of diammonium phosphate was 0.066 g / kg, and the amount of urea was 0.066 g / kg. The specific treatment is shown in Table 2. Alfalfa seeds with full grains and uniform size were selected for sowing, the water content was adjusted within a certain range, the germination of the seeds was observed, and the seeds were harvested on the 10th day.

[0049] The experiments of Comparative Examples 1-3 were carried out according to the conditions in Example 2 of the present invention, and the fertilizers in the test treatments were replaced with the fertilizers shown in Table 2.

[0050] Table 2 Experimental treatments

[0051] Figure 3 The growth of alfalfa seedlings in sand under different treatments is demonstrated. Compared with the control group T1-3, the growth of alfalfa seedlings under the treatment of Example 2 (T02) was more significant, 1.19 times higher than that of T1 (Comparative Example 1). This may be attributed to the strong adsorption capacity of colloidal biochar for nutrients, which reduces the rapid migration of nutrients to the bottom with water, thereby achieving a slow-release effect of nutrients. At the same time, the nutrients in the colloidal biochar itself can be quickly released into the environment for absorption and utilization by the seedlings. Compared with the large-particle biochar in the control group T3, the colloidal biochar in Example 2 (T02) is easier to migrate downward, avoiding the biochar from acting only on the surface. The results of the sand column test provide technical support for the potential of colloidal biochar in soil applications. Example 3 Grassland soil was obtained from the Saibei Ranch in the Saibei Management District, Guyuan County, Zhangjiakou City, Hebei Province (115°51′29″E, 41°52′57″N). After air-drying, the soil was sieved through a 2 mm sieve to remove impurities such as stones and plant roots. The soil pH was 7.71, the conductivity was 78.3 µS / cm, and the texture was loam.

[0052] The test plant was alfalfa, the variety of which was Zhongmu No. 1, purchased from Jiuquan Daye Seed Co., Ltd.

[0053] The experimental steps are as follows: weigh 50 g of soil and put it into a culture dish, and fertilize according to the soil quality. The amount of colloidal biochar prepared in Example 1 of the present invention is 2 g / kg, and the amount of diammonium phosphate and urea is 0.066 g / kg. Each treatment has 3 replicates, and the specific treatments are shown in Table 3. The soil moisture content was adjusted to 60-70% of the field water holding capacity. After one day of pre-cultivation, alfalfa seeds with full grains and uniform size were selected, disinfected with 10% hydrogen peroxide for 5 minutes, and then rinsed with distilled water several times. The seeds were sown into the soil using a hole sowing method, and 16 seeds were sown in each culture dish to ensure uniform spacing between each seed, ensuring good contact with the soil and sufficient growth space.

[0054] During the germination period, add an equal amount of water every day, record the germination of seeds, and calculate the germination rate. Germination rate (%) = (number of germinated seeds / number of test seeds) × 100% After 14 days of cultivation, five alfalfa seedlings with uniform growth were selected from each culture dish, and their aboveground and underground fresh and dry weights, stem lengths, and root lengths were measured. At the same time, the chlorophyll content of the leaves was determined using a chlorophyll meter (SPAD-502Plus).

[0055] The experiments of Comparative Examples 4-6 were carried out according to the conditions in Example 3 of the present invention, and the fertilizers in the test treatments were replaced with the fertilizers shown in Table 3.

[0056] Table 3 Experimental treatments

[0057] Figure 4 The germination rate and relative content of chlorophyll of alfalfa seedlings under different treatments were shown. The results showed that under the T4 (Comparative Example 4) treatment, the germination rate and leaf chlorophyll content of alfalfa seedlings were the lowest. Compared with T5 (Comparative Example 5), the T6 (Comparative Example 6) and T03 (Example 3) treatments increased the germination rate and leaf SPAD value of alfalfa seedlings. This shows that the addition of biochar promotes the germination rate of alfalfa and the relative content of leaf chlorophyll. In particular, compared with T6 (Comparative Example 6), the application amount of biochar in T03 (Example 3) is lower, but the effect of promoting the germination rate of alfalfa seedlings and the chlorophyll content of leaves is better, which increased by 2.17% and 29.10%, respectively.

[0058] Figure 5The fresh weight and dry weight of the aboveground and underground parts of alfalfa seedlings are shown. Compared with the T4 (Comparative Example 4) treatment, the T5 (Comparative Example 5), T6 (Comparative Example 6) and T03 (Example 3) treatments all significantly promoted the fresh weight and dry weight of the aboveground and underground parts. The overall trend is T03>T6>T5>T4, among which the yield-increasing effect of the T03 (Example 3) treatment is the most significant. Specifically, the T03 treatment increased the fresh weight of the aboveground and underground parts by 10.77% and 34.74% respectively compared with T6 (Comparative Example 6), and the dry weight of the aboveground and underground parts increased by 11.82% and 5.33% respectively. This shows that the colloidal biochar prepared by the present invention can significantly increase the fresh weight and dry weight of alfalfa seedlings on the basis of reducing the amount of biochar used.

[0059] Figure 6 The stem length and root length of alfalfa seedlings are shown. Compared with the T4 (Comparative Example 4) treatment, the stem length of T5 (Comparative Example 5), T6 (Comparative Example 6) and T03 (Example 3) increased by 60.50%, 81.51% and 107.08%, respectively, and the root length increased by 127.93%, 162.16% and 170.27%, respectively. Among them, the T03 (Example 3) treatment has the most significant effect on improving the stem length and root length of alfalfa seedlings.

[0060] In general, the compounding of the colloidal biochar prepared by the present invention and the inorganic fertilizer significantly promoted the growth of alfalfa seedlings. Compared with the application of large-particle biochar, the colloidal biochar significantly increased the chlorophyll content, fresh weight, dry weight, stem length and root length of the seedlings while reducing the dosage.

[0061] Example 4 The test soil was the same as that in Example 3.

[0062] Alfalfa was selected as the test plant, and the variety was Nongmu 803. 500 g of soil was placed in a flower pot (13 cm in diameter and 11 cm in height), and fertilization was performed according to the soil quality. The amount of colloidal biochar prepared in Example 1 of the present invention was 2 g / kg, the amount of diammonium phosphate was 0.066 g / kg, and the amount of urea was 0.066 g / kg. Each treatment was repeated 5 times, and the specific treatment scheme is shown in Table 4. Alfalfa seeds of uniform size and full grains were selected, and 7 seeds were sown in each pot, with a sowing depth of about 1-2 cm. When the alfalfa seedlings grew to the three-leaf stage, thinning was performed, and 4 seedlings with consistent growth potential were retained in each pot. During potted cultivation, the soil moisture content was maintained at 60-70% of the field water holding capacity. After 3 months of cultivation, the fresh weight and dry weight of the aboveground and underground parts of alfalfa, the plant height and total root length, and the content of total nitrogen and total phosphorus were measured. Since the colloidal biochar of the present invention is applied on the soil surface, soil is taken in layers to determine the effective phosphorus content in the soil, and the depths of the soil layers are 0-3.5 cm and 3.5-7 cm, respectively.

[0063] The experiments of Comparative Examples 7-9 were carried out according to the conditions in Example 4 of the present invention, and the fertilizers in the test treatments were replaced with the fertilizers shown in Table 4.

[0064] Table 4 Experimental treatments

[0065] Figure 7 The growth of alfalfa after the cultivation was completed was shown. From the appearance, compared with the comparative examples T7, T8 and T9, the growth of Example T04 was significantly better, and the aboveground plants were significantly taller.

[0066] Figure 8 The fresh weight and dry weight data of the aboveground and underground parts of alfalfa are shown. The results show that the growth-promoting effect of Example T04 is the best. Compared with the comparative example T7, the aboveground fresh weight of T8, T9 and T04 increased by 21.41%, 24.37% and 36.81% respectively, and the underground fresh weight increased by 17.51%, 20.87% and 42.44% respectively. The change trend of alfalfa dry weight is similar to the fresh weight. Compared with the comparative example T7, the aboveground dry weight of T8, T9 and T04 increased by 18.56%, 21.65% and 37.63% respectively, and the underground dry weight increased by 22.54%, 30.48% and 41.90% respectively. These results show that the colloidal biochar prepared by the present invention significantly increases the fresh weight and dry weight of the aboveground and underground parts of alfalfa plants, which helps to increase plant yield.

[0067] Fig. 9 The plant height and total root length data of alfalfa are shown. The results show that Example T04 has a significant growth-promoting effect. Under different treatments, the average plant height of alfalfa was 18.13 cm (T7), 19.32 cm (T8), 21.81 cm (T9) and 23.26 cm (T04), respectively, which was 6.56%, 20.30% and 28.30% higher than that of the comparative examples T7, T8, T9 and T04, respectively. In addition, the average total root length of each alfalfa plant was 72.07 cm (T7), 76.58 cm (T8), 79.53 cm (T9) and 88.61 cm (T04) under different treatments, respectively, which was 6.26%, 10.35% and 22.95% higher than that of the comparative examples T7, T8, T9 and T04, respectively. These results show that the colloidal biochar prepared by the present invention has a good growth-promoting effect on both the stems and roots of alfalfa.

[0068] Fig.10The nitrogen and phosphorus contents in the aboveground and underground parts of alfalfa are shown. The results show that the nitrogen content in the aboveground and underground parts of the plants treated with comparative example T7 is the lowest, while the nitrogen content in other treatments increases to varying degrees. The nitrogen content in the aboveground and underground parts follows the trend of T04 (Example 4) > T9 > T8 > T7. This shows that T04 (Example 4) significantly promotes the utilization of nitrogen in the soil by the aboveground and underground parts of the plants. In terms of phosphorus utilization, the phosphorus content in the aboveground and underground parts follows the trend of T04 (Example 4) > T9 > T8 > T7. T04 (Example 4) also increases the absorption of phosphorus by the aboveground and underground parts of the plants. In general, the colloidal biochar prepared by the present invention significantly improves the nutrient content and quality of alfalfa plants.

[0069] Fig.11 The content of available phosphorus in the 0-3.5 cm and 3.5-7 cm soil layers after the potted plants were grown was shown. The results showed that Example T04 significantly increased the available phosphorus content in the 0-3.5 cm soil layer, which was increased by 127.50% compared with the comparative example T7. In the 3.5-7 cm soil layer, the T8 treatment reduced the available phosphorus content by 17.19% compared with the comparative example T7; while the T9 and T04 treatments increased it by 3.39% and 12.82%, respectively. In particular, the T04 treatment significantly increased the available phosphorus content in the 3.5-7 cm soil layer. Overall, the colloidal biochar prepared by the present invention helps to activate the available phosphorus in the soil, thereby promoting the absorption and utilization of phosphorus by plants.

[0070] In general, compared with other treatments, the colloidal biochar compounded with inorganic fertilizer treatment prepared by the present invention significantly increased the fresh weight and dry weight of the aboveground and underground parts of the plants, as well as the growth of stems and roots. This treatment helps to activate the available phosphorus in the soil, provides sufficient nutrient conditions for plant growth, and thus promotes the absorption of nitrogen and phosphorus by plants.

[0071] Example 5 The test soil and test plants were the same as those in Example 4.

[0072] A PVC tube (44 cm long, 11.4 cm radius) was selected, and the soil that had passed through a 2 mm sieve was filled into the PVC tube according to the actual field soil bulk density. According to the provisions of Table 5, the fertilizer was applied to the soil surface with water. The amount of colloidal biochar prepared in Example 1 of the present invention was 2 g / kg, the amount of diammonium phosphate was 0.066 g / kg, and the amount of urea was 0.066 g / kg. Inorganic fertilizer and colloidal biochar were added according to the mass of the 0-20 cm soil layer. The water content of the potted plants was maintained at 70% of the field water holding capacity. After the soil column was balanced for 7 days, sowing was carried out, and 10 seeds were sown per pot. After 3 months of planting, the fresh weight and dry weight of the aboveground part of the plant were measured, and the contents of total organic carbon (SOC) and soluble organic carbon (DOC) in the soil (0-10 cm, 10-20 cm, 20-30 cm and 30-40 cm) were measured.

[0073] The experiments of Comparative Examples 10-12 were carried out according to the conditions in Example 5 of the present invention, and the fertilizers in the test treatments were replaced with the fertilizers shown in Table 5.

[0074] Table 5 Experimental treatment

[0075] Fig.12 The growth conditions of the aboveground and underground parts of alfalfa are shown. Compared with the comparative example 10-12 (T10-12), the aboveground growth condition of Example 5 (T05) is better, and the fibrous roots under the root system are more vigorous.

[0076] Fig.13 The fresh weight and dry weight of the aboveground part of alfalfa 3 months after planting are shown. Under the treatment of T05 (Example 5), the growth condition of alfalfa is the best, and the overall fresh weight shows a trend of T05 (Example 5)>T11>T12>T10, while the dry weight shows a trend of T05 (Example 5)>T12>T11>T10. Compared with the comparative example T10-12, the fresh weight under the treatment of T05 (Example 5) increased by 26.05%, 13.17% and 21.85%, respectively, and the dry weight increased by 48.95%, 30.65% and 13.02%, respectively. The colloidal biochar prepared by the present invention significantly increases the yield of the aboveground part.

[0077] Fig.14The contents of soil total organic carbon and soluble organic carbon in different soil layers under different treatments are shown. Compared with comparative examples T10 and T11, T12 (Comparative Example 12) and T05 (Example 5) both increased the soil total organic carbon content in different soil layers, indicating that the addition of biochar can increase the organic carbon content in the soil profile. In particular, T05 (Example 5) increased the total organic carbon content by 3.14% in the 30-40 cm soil layer compared to T12 (Comparative Example 12). This shows that colloidal biochar is more conducive to carbon fixation in deep soil (30-40 cm) than large-particle biochar. This may be due to the mobility of the colloidal biochar itself or it promotes the migration of soluble organic matter in the soil to the 30-40 cm soil layer.

[0078] In general, the T05 (Example 5) treatment can significantly increase the fresh weight and dry weight of the aboveground part of the plant, promote the growth of fibrous roots, and is beneficial to carbon sequestration in deep soil (30-40 cm).

[0079] The colloidal biochar prepared by the present invention not only enhances the adsorption capacity of nutrients and reduces the loss of nutrients, but also improves the yield and quality of alfalfa after being used in combination with inorganic fertilizers, and helps to activate effective nutrients in the soil and fix carbon in deep soil (30-40 cm). In addition, the fertilizer preparation operation is simple, time-saving and labor-saving, and the raw materials of the colloidal biochar are easy to obtain and the dosage is low, which reduces the production cost, and provides a new improvement idea and technical preparation method for degraded grasslands.

[0080] The embodiments described above are part of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A colloidal biochar, characterized in that: The particle size of the colloidal biochar is 400-1000 nm.

2. The colloidal biochar according to any one of claims 1, characterized in that The colloidal biochar is prepared by the following method: biochar and water are mixed and stirred, and heated and emulsified to obtain the colloidal biochar.

3. The colloidal biochar according to claim 2, characterized in that The raw material of the biochar is selected from at least one of wheat straw, corn straw, rice straw, wood chips, branches and leaves, and bark; The mass ratio of the biochar to the water is 1:5-40; the temperature of the heating emulsification is 85-95° C., and the time is 30-120 min.

4. The method for preparing the colloidal biochar according to any one of claims 1 to 3, comprising the steps of: mixing and stirring the biochar and water, and heating and emulsifying to obtain the colloidal biochar.

5. The method according to claim 4, characterized in that The mass ratio of the biochar to the water is 1:5-40; the temperature of the heating emulsification is 85-95° C., and the time is 30-120 min.

6. A soil conditioner, characterized in that: The invention comprises the colloidal biochar and fertilizer according to any one of claims 1 to 3.

7. The soil conditioner according to claim 6, characterized in that The soil conditioner comprises the following components in parts by mass: 2 parts of colloidal biochar; 0.03-0.08 parts of diammonium phosphate fertilizer; and 0.03-0.08 parts of urea fertilizer.

8. Use of the soil conditioner according to claim 6 or 7 in grassland.

9. The use according to claim 8, characterized in that: The grassland is soil for growing alfalfa.

10. The use according to claim 8 or 9, characterized in that: The total application amount of the soil conditioner is 2-5 g per kilogram of grassland soil.

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