Method for detecting carbon sequestration amount of soil biochar

Abstract

The invention provides a method for detecting the carbon sequestration amount of soil biochar, which specifically comprises the following steps: averagely distributing sample soil to obtain a plurality of groups of group soil; applying biochar and bacterial fertilizer to each group of soil to obtain experimental soil; respectively taking out corresponding unplanted sample soil from each piece of experimental soil; plants are planted in each group of experimental soil meeting the plant planting requirements; taking out planting sample soil from each group of experimental soil every preset sampling period; performing carbon content and element content detection on a plurality of unplanted sample soils and a plurality of planted sample soils corresponding to each group of experimental soils to obtain a total carbon content, an organic carbon content and an element content corresponding to each group of experimental soils so as to determine the charcoal carbon sequestration amount of the sample soils, the optimal biochar addition amount is determined, appropriate crop varieties are selected, matched cultivation management measures are formulated, and scientific guidance is provided for efficient improvement and sustainable utilization of desertification soil.

Description

Technical Field

[0001] This invention relates to the field of soil carbon sequestration capacity testing, and in particular to a method for testing the carbon sequestration capacity of soil biochar. Background Technology

[0002] Biomass is the fourth largest energy source after coal, oil, and natural gas, and the only renewable energy source among them. It is a low-carbon, zero-carbon, or even negative-carbon material. Statistics show that the average carbon emission intensity of various power sources is only 18 grams of CO2 per kilowatt-hour, equivalent to 1.8%, 2.1%, and 3.8% of that of coal, oil, and gas, respectively. Therefore, biomass is considered to have significant potential for negative-carbon applications. However, currently, the vast majority of agricultural and forestry biomass is underutilized. Biochar is primarily used as a soil conditioner in soil improvement, and secondarily as a biochar fertilizer in agriculture, mainly as a soil conditioner and fertilizer carrier.

[0003] With traditional desertification control methods facing bottlenecks such as high costs and low efficiency, biochar technology has emerged as an innovative direction for desertification control due to its unique advantages. Biochar is a product of biomass pyrolysis under anaerobic conditions. Its porous structure can significantly improve soil water retention capacity (30% higher than undisturbed soil) and nutrient adsorption efficiency (50% increase in ammonium nitrogen adsorption). More importantly, biochar is stable in soil for hundreds of years, and its carbon sequestration efficiency is 3-5 times that of traditional vegetation restoration.

[0004] Current methods for detecting the carbon sequestration capacity of soil biochar face problems such as insufficient data, complex mechanisms, and high economic costs. Moreover, existing methods often focus on a single mechanism while neglecting the interaction effects of biochar. Therefore, there is a need to propose a method for detecting the carbon sequestration capacity of soil biochar that can comprehensively assess the carbon sequestration efficiency and total changes of biochar. Summary of the Invention

[0005] To address the aforementioned technical problems, the technical solution adopted by this invention is as follows: According to one aspect of this application, a method for detecting the carbon sequestration capacity of soil biochar is provided, comprising: Step S100: Obtain sample soil by sampling soil from several preset locations; the soil sampling points are located in the same geographical area; the sample soil is soil used for biochar carbon sequestration detection. Step S200: Distribute the sample soil evenly to obtain several groups of soil; the weight of each group of soil is equal. Step S300: According to the preset fertilizer addition ratio for each group of soil, apply the corresponding proportion of biochar and microbial fertilizer to each group of soil to obtain several groups of experimental soil. Step S400: Divide each group of experimental soil into equal parts to obtain the first and second experimental soils corresponding to each group of experimental soils. Step S500: Take out a preset weight of experimental soil from the first and second experimental soils corresponding to each group of experimental soils, and determine the taken-out experimental soil as unplanted sample soil. Step S600: Plant the same number and type of plants in the first and second experimental soils corresponding to each group of experimental soils that meet the requirements for plant planting, and place the first and second experimental soils corresponding to each group of experimental soils in the same cultivation environment. Step S700: Every preset sampling period, take out a preset weight of experimental soil from the first and second experimental soils corresponding to each group of experimental soils, and determine the taken-out experimental soil as planting sample soil, until the number of sampling periods meets the preset period threshold. Step S800: Detect the carbon content and element content of several unplanted soil samples and several planted soil samples corresponding to each group of experimental soils, so as to obtain the total carbon content, organic carbon content and element content of each group of experimental soils. Step S900: Analyze the trends of total carbon content, organic carbon content, and elemental content in several groups of experimental soils to determine the biochar carbon sequestration capacity of the sample soil.

[0006] The present invention has at least the following beneficial effects: The method for detecting soil biochar carbon sequestration of the present invention firstly divides the sample soil into several groups. Based on the fertilizer addition ratio corresponding to each group, a corresponding ratio of biochar and microbial fertilizer is applied to each group to obtain several experimental soil groups. Each experimental soil group is then divided equally to obtain a first experimental soil and a second experimental soil corresponding to each group. A predetermined weight of experimental soil is taken from each of the first and second experimental soil groups, and the taken experimental soil is designated as unplanted sample soil. The first experimental soil corresponding to each group of experimental soils that meets the requirements for plant cultivation is then... The same number and type of plants were planted in both the first and second experimental soils. The first and second experimental soils corresponding to each group of experimental soils were placed in the same cultivation environment. At each preset sampling period, a preset weight of experimental soil was taken from the first and second experimental soils corresponding to each group of experimental soils. The taken experimental soil was determined as the planting sample soil. The carbon content and element content of several unplanted sample soils and several planted sample soils corresponding to each group of experimental soils were tested to obtain the total carbon content, organic carbon content and element content of each group of experimental soils, and to determine the biochar carbon sequestration of the sample soils. The obtained data were compared to analyze the carbon sequestration capacity of different experimental soil groups by comparing the total carbon increment, organic carbon content increment, and carbon sequestration rate. The impact of biochar on carbon pool stability was analyzed, and correlation analysis was conducted to explore the correlation between biochar addition amount and soil pH, crop growth status, and crop yield. The effect of biochar in desert soil improvement was systematically evaluated, which can determine the optimal biochar addition amount, select suitable crop varieties, and formulate supporting cultivation and management measures, providing scientific guidance for the efficient improvement and sustainable utilization of desertified soils. Attached Figure Description

[0007] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0008] Figure 1 A flowchart of a method for detecting carbon sequestration in soil biochar provided in an embodiment of the present invention. Detailed Implementation

[0009] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0010] Current methods for predicting the carbon fixation time of soil biochar rely on thermal oxidation experiments and the construction of Arrhenius models. Thermal oxidation experiments are a core approach to studying the oxidation behavior of materials (such as metals, polymers, and biochar) under high-temperature aerobic conditions. By controlling conditions such as temperature and oxygen concentration, the rate, products, and mechanisms of the oxidation process can be quantified. The Arrhenius model is a classic kinetic model describing the relationship between chemical reaction rate and temperature, suitable for activation energy-controlled reaction processes such as thermal oxidation. Its core principle is to obtain the activation energy (E) of the reaction through fitting experimental data. a This method uses the activation energy half-life of biochar to reveal the quantitative effect of temperature on reaction rate and pre-exponential factor (A), assesses the carbon sequestration capacity of biochar by distinguishing carbon components, and is suitable for long-term carbon sequestration prediction. However, this method requires specialized thermal analysis equipment, which is costly, and the impact of biochar on soil microbial communities is bidirectional: on the one hand, its porous structure provides habitat for microorganisms, promoting the growth of carbon-fixing bacteria; on the other hand, the addition of biochar may accelerate the decomposition of existing organic carbon in the soil through an "activation effect." For example, the activation effect mechanisms of pyrolytic biochar and hydrothermal biochar are different, and the available C / N stoichiometric ratio is a key regulatory factor. Furthermore, existing models have not fully integrated the coupling relationship between microbial metabolic dynamics and carbon cycling, resulting in significant deviations between predicted results and actual carbon sequestration.

[0011] Current methods for measuring soil carbon sequestration employ isotope tracing, which tracks the input, transformation, fixation, and turnover of carbon in soil based on the natural abundance differences or artificial labeling of carbon isotopes. This allows for a quantitative assessment of soil carbon sequestration capacity. The core of this method is to utilize the specificity of isotope signals to distinguish between "new carbon," such as exogenously added biochar and plant litter, and "existing carbon." It also quantifies the retention rate and sequestration form of new carbon in the soil, integrates dimensional data, predicts differences in carbon sequestration under different environmental conditions, and monitors carbon content and microbial abundance in real time. This method accurately distinguishes between new and existing carbon, avoids interference from fluctuations in the natural carbon pool, and is suitable for laboratory microscale cultivation, field mesoscale observation, and ecosystem model validation. It allows for real-time monitoring of carbon migration and transformation pathways between different components, revealing carbon sequestration mechanisms. However, although this method (such as 13C labeling) can accurately track carbon sources, it is costly and requires specialized equipment and long-term monitoring, making it difficult to popularize in field trials. Furthermore, the migration and transformation cycle of labeled carbon in soil is long, and short-term experiments cannot reflect long-term carbon sequestration dynamics. The spatiotemporal variation of stable isotope composition in soil water is significant, which leads to insufficient representativeness of sampling points.

[0012] Current methods for phosphoric acid-enhanced biochar carbon sequestration employ Boehm titration (total acid-base titration) and BET analysis (specific surface area testing). By introducing phosphorus (mainly in the form of phosphoric acid or phosphate) during biochar preparation (e.g., before or after pyrolysis), and utilizing the chemical interactions between phosphorus and carbon (such as forming stable phosphorus-containing carbon structures and enhancing mineral binding capacity), the carbon sequestration efficiency and long-term stability of biochar are improved, thereby reducing carbon mineralization loss in the soil and achieving efficient carbon sequestration. The core lies in optimizing the surface functional groups, pore structure, and chemical activity of biochar through phosphorus modification, making it a multifunctional material with both carbon sequestration and phosphorus regulation capabilities. Through a dual chemical and physical mechanism, it significantly improves carbon stability in the soil, offering multiple benefits such as carbon sequestration, slow-release phosphate fertilizer, and soil structure improvement, meeting the needs of sustainable agricultural development. The carbon sequestration capacity is assessed based on surface functional group content and CO2 adsorption capacity. However, this method using phosphoric acid-modified biochar in acidic soils easily releases phosphates, potentially leading to eutrophication of water bodies. The concentration of phosphoric acid impregnation, pyrolysis temperature, and time need to be precisely controlled. For example, pyrolysis above 500℃ may lead to phosphorus volatilization loss, while low-temperature pyrolysis, although retaining more functional groups, results in insufficient carbon fixation stability. In addition, raw material pretreatment can improve the uniformity of phosphorus distribution, but its industrial-scale application is easily limited by excessive energy consumption, and it also lacks long-term effect uncertainty and microbial feedback.

[0013] Therefore, analysis of the existing technologies reveals that methods for predicting biochar carbon sequestration time, calculating soil carbon sequestration, and using phosphate-enhanced biochar for carbon sequestration all face common problems such as insufficient data, complex mechanisms, and high economic costs. Soil carbon sequestration is the result of the synergistic effects of physical protection (aggregate encapsulation), chemical stabilization (mineral binding), and biotransformation (microbial residues). Existing methods often focus on a single mechanism, neglecting the interactive effects of biochar. Consequently, the accuracy of the obtained results regarding soil biochar carbon sequestration capacity is low. Therefore, this invention proposes a method for detecting soil biochar carbon sequestration.

[0014] A method for detecting carbon sequestration capacity of soil biochar, such as Figure 1 As shown, it includes the following steps: Step S100: Obtain sample soil by sampling soil from several preset locations; Several soil sampling points are located in the same geographical area (e.g., in the same desertification area); the sample soil is soil used for biochar carbon sequestration testing.

[0015] Furthermore, step S100 includes steps S110-S140: Step S110: Remove the topsoil at a preset depth at each preset location soil sampling point; The distance between any two adjacent soil sampling points meets the requirements of the preset sampling distance range.

[0016] Step S120: Collect the same weight of soil samples from each soil sampling point; Step S130: Mix several soil samples to obtain mixed soil; Step S140: Filter the mixed soil through a sieve with a preset mesh size to obtain the sample soil after sieve filtration.

[0017] As a feasible embodiment of step S100, a random sampling method is adopted to determine multiple soil sampling points in the soil sampling area. The distribution of soil sampling points should be uniform to avoid concentration in a certain local area. Then, using tools such as shovels and hoes, surface debris such as fallen leaves and stones are removed at each soil sampling point, and the topsoil (such as about 10cm deep) is dug up. Then, appropriate amounts of soil samples are taken from soil sampling points at different locations and mixed together to form a mixed soil sample (i.e., sample soil). It is ensured that the amount of soil taken from each soil sampling point should be approximately the same, and the sampling depth, location, time and other information are noted. Then, the soil is passed through a 10-mesh sieve to remove large particles of impurities such as stones and root remnants, while retaining the basic structure and larger pores of the soil.

[0018] Step S200: Distribute the sample soil evenly to obtain several groups of soil groups; The soil in each group had the same weight.

[0019] Step S300: According to the preset fertilizer addition ratio for each group of soil, apply the corresponding proportion of biochar and microbial fertilizer to each group of soil to obtain several groups of experimental soil. As a feasible example, the proportions of biochar and microbial fertilizer in several experimental soil samples are as follows: No biochar and microbial fertilizer were applied to the first group of soil samples to obtain the first group of experimental soil samples. In the second group of soil samples, 3 grams of biochar were added per 100 grams of soil to obtain the second group of experimental soil. In the third group of soil samples, 3 grams of biochar were added per 100 grams of soil to obtain the third group of experimental soil. In the fourth group of soil, 0.5 grams of microbial fertilizer was applied per 100 grams of soil to obtain the fourth group of experimental soil. In the fifth group of soil, 3 grams of biochar and 0.5 grams of microbial fertilizer were applied per 100 grams of soil to obtain the fifth group of experimental soil. In the sixth group of soil, 3 grams of biochar and 1 gram of microbial fertilizer were applied per 100 grams of soil to obtain the sixth group of experimental soil. In the seventh group of soil, 5 grams of biochar and 0.5 grams of microbial fertilizer were applied per 100 grams of soil to obtain the seventh group of experimental soil. In the eighth group of soil, 5 grams of biochar and 1 gram of microbial fertilizer were applied per 100 grams of soil to obtain the eighth group of experimental soil. In the ninth group of soil, 10 grams of biochar and 0.5 grams of microbial fertilizer were applied per 100 grams of soil to obtain the ninth group of experimental soil. In the tenth group of soil, 10 grams of biochar and 1 gram of microbial fertilizer were applied per 100 grams of soil to obtain the tenth group of experimental soil. In this study, the planting conditions of the soils in the first, third to tenth groups were set to meet the requirements for plant cultivation (i.e., planted with plants), while the planting conditions of the soils in the second group were set to not meet the requirements for plant cultivation (i.e., no plants were planted). The effect of not planting plants on the biochar content of the soil was obtained by analyzing the biochar content of the second group of experimental soils.

[0020] The first and second groups of experimental soil were control samples, while the third to tenth groups of experimental soil were experimental samples.

[0021] According to the experimental design, the required biochar content can be weighed using a gram scale with an accuracy of 0.1 grams. When potting the soil for each group of experiments, take the corresponding soil and fertilizer (microbial fertilizer) according to the predetermined ratio, mix the fertilizer and soil evenly, mix at least 4 times, and then fill the pot with soil. When filling the pot, first fill it with 1 / 2 of the soil weight, flatten and compact it, and then fill it with the other half. Make sure that the compaction of each pot is consistent. The soil compaction should not be too tight or too loose, and ensure that the soil surface is 1-2 cm away from the rim of the pot so that the plants can be watered later.

[0022] Step S400: Divide each group of experimental soil into equal parts to obtain the first and second experimental soils corresponding to each group of experimental soils. In this experiment, each of the ten groups of experimental soils includes a first experimental soil and a second experimental soil. The first and second experimental soils are combined to form the same group of experimental soils, in order to improve the accuracy of the carbon content results in subsequent tests and reduce the detection error.

[0023] Step S500: Take out a preset weight of experimental soil from the first and second experimental soils corresponding to each group of experimental soils, and determine the taken-out experimental soil as unplanted sample soil. Furthermore, step S500 includes steps S510-S530: Step S510: Determine the first or second experimental soil corresponding to any group of experimental soils as the soil to be sampled; Step S520: Collect experimental soil samples at a preset depth and volume at the four vertices and the center of the soil to be sampled. Step S530: Mix several experimental soil samples collected from the soil to be sampled to obtain the unplanted sample soil corresponding to the soil to be sampled.

[0024] After dividing each group of experimental soil into corresponding first and second experimental soils, several first and second experimental soils were placed in pots, and the corresponding experimental soil group number was marked on the pots for identification. During sampling, a five-point sampling method was used for each potted plant. Each potted plant was regarded as a small research area. Five points were determined on the surface of the potted soil, namely the four corners and the center of the pot. Soil was collected from these five points with a small spoon at a depth of about 10 cm. The soil collected from the five points was then mixed evenly and used as the soil sample for that potted plant (this method was used for both unplanted and planted soil samples). The soil samples were sealed and stored, and the experimental group and time information were marked.

[0025] Each set of experimental soils has a corresponding unplanted sample soil (i.e., the sample soil when no plants were planted).

[0026] Step S600: Plant the same number and type of plants in the first and second experimental soils corresponding to each group of experimental soils that meet the requirements for plant planting, and place the first and second experimental soils corresponding to each group of experimental soils in the same cultivation environment. As a feasible implementation, artificial cultivation boxes were used for planting. LED plant growth lights were used inside the cultivation boxes to ensure that the spectral range covered the spectrum required for plant photosynthesis, simulating natural light conditions. The temperature range of the first and second experimental soils placed in the cultivation environment was 23 to 27 degrees Celsius, the relative humidity range was 60% to 70%, the carbon dioxide concentration was atmospheric concentration (approximately 400 ppm), and the light intensity was 4000 illuminance. The day-night cycle was simulated, with a light cycle of 12 hours of light and 12 hours of darkness per day. The watering frequency was once every 2 to 3 days, keeping the soil moist but not overwatered. The amount of water was controlled by weighing, and each watering was carried out to 60% to 70% of the soil's water holding capacity.

[0027] Step S610: After planting plants in the first and second experimental soils corresponding to each group of experimental soils for the first preset number of days, obtain the number of germinated seeds of the plants planted in the first and second experimental soils corresponding to each group of experimental soils. Step S620: Determine the percentage of the ratio of the number of germinated seeds of plants planted in the first or second experimental soil corresponding to each group of experimental soil to the number of plant seeds planted in the first or second experimental soil as the seed germination rate of the first or second experimental soil. Step S630: On the second preset number of days after planting plants in the first and second experimental soils corresponding to each group of experimental soils, obtain the number of seedlings of the plants planted in the first and second experimental soils corresponding to each group of experimental soils. The second preset number of days is greater than the first preset number of days.

[0028] Step S640: Determine the seed germination rate of the first or second experimental soil as the percentage of the number of germinating seeds of plants planted in the first or second experimental soil corresponding to each group of experimental soils to the number of plant seeds planted in the first or second experimental soil.

[0029] The first preset number of days can be five days, and the second preset number of days can be ten days. That is, on the fifth day after planting plants in each of the first or second experimental soils, the seed germination rate of the plants in the corresponding pots of each of the first and second experimental soils is measured. On the tenth day after planting plants in each of the first or second experimental soils, the seed emergence rate of the plants in the corresponding pots of each of the first and second experimental soils is measured. By measuring the seed germination rate and seed emergence rate of the plants planted in each group of experimental soils, the growth trend of the soil after the ratio of biochar and microbial fertilizer in each group of experimental soils can be determined, so as to judge the growth effect of each group of experimental soils on plants (the specific judgment method can adopt the existing soil plant growth judgment method).

[0030] In addition, after measuring the seed germination rate, thinning is performed on the potted plants. Excess seedlings are cut or pulled from the soil using tweezers. During thinning, the process should proceed from the edge of the pot to the center or from one end to the other, ensuring even thinning and maintaining 3 to 4 seedlings per pot. After thinning, water the potted plants appropriately to ensure close contact between the soil and the roots of the remaining seedlings, which also helps the seedlings better adapt to the environmental changes after thinning.

[0031] Furthermore, during plant growth, the effect of each experimental soil on plant growth can be further determined by measuring plant height and stem diameter. Specifically, align the zero mark of a ruler with the base of the plant stem, then extend the ruler upwards along the central axis of the plant stem until the top of the ruler aligns with the highest point of the plant. Read the scale value corresponding to the highest point on the ruler; this is the plant height. Record the data. To measure the stem diameter using vernier calipers, first open the two clamping feet of the vernier calipers and gently clamp them onto both sides of the plant stem, ensuring close contact between the clamping feet and the stem surface. However, do not squeeze the stem excessively to avoid damage or measurement errors. Then read the scale value on the vernier calipers and record the measurement data.

[0032] Step S700: Every preset sampling period, take out a preset weight of experimental soil from the first and second experimental soils corresponding to each group of experimental soils, and determine the taken-out experimental soil as planting sample soil, until the number of sampling periods meets the preset period threshold. The sampling period can be set to ten days, that is, every ten days during the experiment, samples are taken according to the above steps and the samples are preserved for subsequent measurements. Each experimental period can be thirty to forty days.

[0033] Soil pH can serve as an important indicator for subsequent research on soil samples. Therefore, it is necessary to test the pH of the soil samples. When testing the pH of the soil samples, steps S710-S720 are performed: Step S710: Determine the target sample soil from several planting soil samples obtained in the last sampling cycle. Step S720: Take 5 grams of soil from each target soil sample and each unplanted soil sample, and place them in 25 ml containers. Add 12.5 ml of distilled water to each container, seal them, and shake continuously at 150 rpm for 2 minutes. After removal, let stand for 30 minutes, and use a pH meter to detect the upper suspension of each target soil sample and each unplanted soil sample to obtain the corresponding pH of each target soil sample and each unplanted soil sample.

[0034] Furthermore, after the number of sampling cycles meets the preset cycle threshold (i.e., the first experimental cycle is completed), a second experimental cycle is required to further improve the accuracy of the soil carbon sequestration capacity test results. The specific method includes steps S701-S702: Step S701: After the number of sampling cycles meets the preset cycle threshold, remove all plants planted in the experimental soil. Step S702: According to the preset fertilizer addition ratio corresponding to each group of experimental soils, apply the corresponding proportions of biochar and microbial fertilizer to the second experimental soil corresponding to each group of experimental soils, and then execute step S500.

[0035] The preset fertilizer addition ratio, namely the ratio of biochar and microbial fertilizer in step S300, is applied only to the second experimental soil corresponding to each group of experimental soils. The first experimental soil is not treated. Therefore, in the second experimental cycle, the first experimental soil of each group of experimental soils is the control group, and the second experimental soil is the experimental group. This is used to further sample the planted soil, the unplanted soil sample, and the planted soil sample. The total carbon content, organic carbon content, and element content of the sampled soil are then tested to illustrate the effect of each group of experimental soils on plant growth.

[0036] In addition, after the number of sampling cycles meets the preset cycle threshold, one plant is randomly selected from several plants planted in the first and second experimental soils corresponding to each group of experimental soils. The plant is washed, the underground part is cut off, the water is absorbed with filter paper, and the plant is weighed to obtain the fresh weight of the plant. Then, the plant is placed in an environment of 105 degrees Celsius for blanching, and then placed in an environment of 65 degrees Celsius for drying to constant weight. The dried plant is weighed to obtain the dry weight of the plant. By detecting the fresh weight and dry weight of the plants in each group of experimental soils, the effect of the corresponding experimental soil on plant growth can be obtained.

[0037] Step S800: Detect the carbon content and element content of several unplanted soil samples and several planted soil samples corresponding to each group of experimental soils, so as to obtain the total carbon content, organic carbon content and element content of each group of experimental soils. Specifically, step S800 includes steps S810-S870: Step S810: Grind several unplanted soil samples and several planted soil samples corresponding to each group of experimental soils, filter them through a 100-mesh sieve, and measure the total carbon content of each unplanted soil sample and each planted soil sample after filtration using an elemental analyzer. Step S820: Determine the average total carbon content of several unplanted soil samples or several planted soil samples corresponding to any group of experimental soils as the total carbon content corresponding to that group of experimental soils. Specifically, a feasible embodiment of the total carbon content detection method is as follows: Soil samples (unplanted or planted) are ground and filtered through a 100-mesh sieve. The carbon content of the sample is measured using an elemental analyzer. Under each experimental condition, a bypass test with an empty tin capsule and two sets of 1-2 mg BBOT (2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene) is performed as a pre-experimental baseline. The elemental analyzer is heated, its airtightness is checked, and ventilation is performed. The sample weight is measured to be 10-20 mg using a scale with an accuracy of 0.00001 g. The sample is then placed in an empty tin capsule, sealed, and placed in the elemental analyzer for testing. Under the action of a composite catalyst, the sample undergoes high-temperature oxidation and combustion to generate nitrogen, nitrogen oxides, carbon dioxide, sulfur dioxide, and water, which, propelled by a carrier gas, enter the separation and detection unit. After non-nitrogen compounds are adsorbed and retained in the adsorption column, nitrogen oxides are reduced to nitrogen gas and then measured by the detector. They are then separated and measured in the order of carbon, hydrogen, and sulfur to obtain the total carbon content of each experimental soil group.

[0038] After determining the total carbon content of each group of experimental soils, in order to further analyze the trend of carbon content change in the experimental soils, the change in carbon content of each group of experimental soils can be calculated. The change in carbon content is the difference between the total carbon content of the next group of soils for any planting sample and the total carbon content of the previous group of soils for that planting sample. By analyzing the change in carbon content, the trend of carbon content change in the corresponding experimental soils can be obtained.

[0039] Step S830: Take 0.5 g of sieved soil sample from each group of experimental soil samples, including unplanted and planted soil samples, and air-dry them. Place the air-dried sieved soil sample into a digestion tube, add potassium dichromate sulfuric acid solution to the digestion tube, shake well, and then place the digestion tube into a high-temperature digestion furnace. Digest at 180 to 190 degrees Celsius for 30 minutes to oxidize the organic carbon in the sieved soil sample. After digestion, remove the digestion tube, cool it, add water, add an indicator, titrate with ferrous sulfate standard solution, and calculate the organic carbon content in the sieved soil sample based on the volume of ferrous sulfate standard solution consumed. Step S840: The average organic carbon content in the sieved soil samples of several unplanted soil samples or several planted soil samples corresponding to any group of experimental soils is determined as the organic carbon content corresponding to that group of experimental soils. Specifically, a feasible embodiment of the method for detecting organic carbon content is as follows: The contents of organic carbon, ammonium nitrogen, available phosphorus, and available potassium are analyzed using a soil analyzer. The collected soil sample is air-dried naturally, impurities are removed, and the sample is ground and passed through a 100-mesh sieve. 0.5 grams of the sieved soil sample is accurately weighed and placed in a digestion tube. A certain amount of potassium dichromate-sulfuric acid solution is added to the digestion tube, and the mixture is shaken well. The digestion tube is then placed in a high-temperature digestion furnace and digested at 180 to 190 degrees Celsius for approximately 30 minutes to oxidize the organic carbon in the soil. After digestion, the digestion tube is removed and cooled. Then, an appropriate amount of water is added, an indicator is added, and titration is performed using a ferrous sulfate standard solution. The soil organic carbon content is calculated based on the volume of ferrous sulfate standard solution consumed (the method for calculating the soil organic carbon content based on the volume of ferrous sulfate standard solution consumed adopts existing organic carbon calculation methods).

[0040] In addition, the trend of organic carbon content in the experimental soil can be analyzed by calculating the change in organic carbon content. The change in organic carbon content in the experimental group (i.e., the increase in organic carbon) is the difference between the organic carbon content of the experimental group and the corresponding organic carbon content of the control group. The change in organic carbon content in the control group is the difference between the organic carbon content of the experimental group corresponding to the control group and the initial organic carbon content of the soil in the control group.

[0041] Step S850: Take 5 grams of soil sample from each of the unplanted and planted soil samples corresponding to each group of experimental soils. Place each soil sample into a centrifuge tube and add 2 mol / L potassium chloride solution to each centrifuge tube. Shake and extract for 30 minutes. After centrifugation or filtration, obtain the soil extract corresponding to each soil sample. Put the preset volume of extract into a colorimetric tube, add Nessler's reagent and shake well. Place in the dark for 10 to 15 minutes to allow ammonium nitrogen to react with Nessler's reagent to form a yellow or brown complex. Then, use a spectrophotometer to measure the absorbance of the yellow or brown complex solution at a wavelength of 420 nm. Calculate the ammonium nitrogen content in each soil sample according to the standard curve (the method for calculating the soil ammonium nitrogen content according to the absorbance standard curve adopts the existing method for calculating ammonium nitrogen). Step S860: Take 5 grams of soil sample from each of the unplanted and planted soil samples corresponding to each group of experimental soils, and air-dry them naturally. Add sodium bicarbonate extraction solution with a pH of 8.5 to each air-dried soil sample, shake and extract for 30 minutes, filter to obtain the available phosphorus extract for each soil sample, put the preset volume of available phosphorus extract into a colorimetric tube, add molybdenum antimony reagent mixed colorimetric reagent in sequence, shake well and let stand at room temperature for 30 minutes to allow phosphorus to react with molybdenum antimony reagent to form a blue complex, then use a spectrophotometer to measure the absorbance of the blue complex solution at a wavelength of 700 nm, and calculate the available phosphorus content in each soil sample according to the standard curve (the method for calculating the available phosphorus content of soil according to the absorbance standard curve adopts the existing method for calculating available phosphorus). Step S870: Take 5 grams of soil sample from each of the unplanted and planted soil samples corresponding to each group of experimental soils, and air dry them naturally. Add 1 mol / L ammonium acetate solution to each air-dried soil sample, shake and extract for 30 minutes, and then filter to obtain the available potassium extract for each soil sample. Place each available potassium extract in a flame photometer to measure the characteristic spectral intensity of potassium ion emission, and calculate the available potassium content in each soil sample according to the standard curve (the method for calculating the available potassium content in soil according to the standard curve of characteristic spectral intensity adopts the existing method for calculating available potassium).

[0042] Step S900: Analyze the trends of total carbon content, organic carbon content, and elemental content in several groups of experimental soils to determine the biochar carbon sequestration capacity of the sample soil.

[0043] The analysis methods for the changing trends of total carbon content, organic carbon content, and elemental content in several groups of experimental soils are existing elemental content analysis methods, user-defined elemental content analysis methods, or preset rules for determining biochar carbon sequestration.

[0044] The experimental data were compared to analyze the effects of different treatment groups on soil carbon sequestration capacity, including total carbon increment, organic carbon content increment, and carbon sequestration rate. The impact of biochar on carbon pool stability was analyzed, and correlation analysis was conducted to explore the correlation between biochar addition amount and soil pH, crop growth status, and crop yield.

[0045] This invention presents a short-term indoor incubator experiment involving the application of biochar to desertified soils. The experiment measured soil nutrient content, organic carbon content, crop characterization, and crop yield. It proposes an experimental method for measuring the carbon sequestration capacity of biochar fertilizer in typical desert soils, accurately determining changes in the content of macroelements such as carbon, nitrogen, phosphorus, and potassium after biochar application. This study aims to understand whether biochar can increase soil nutrient content and the extent to which different biochar application amounts improve nutrient levels, providing a basis for rational fertilization and soil improvement. The carbon sequestration effect of biochar application is quantified by precisely measuring changes in soil organic carbon content, clarifying the short-term carbon sequestration capacity of biochar in desert soils. By comparing the organic carbon content of different treatment groups, the relationship between biochar application amount and carbon sequestration is determined, evaluating the feasibility and potential of biochar as a carbon sequestration method in desert soil improvement. Comparison of crop characterization in different experimental groups analyzes the growth status of crops treated with biochar, observing and measuring morphological indicators such as plant height and stem diameter, providing a comprehensive understanding of the impact of biochar on crop growth and development. This study aims to clarify whether biochar can promote crop growth and improve crop conditions, providing a reference for screening crop varieties suitable for growth in desertified soils and responding well to biochar. It also aims to determine the role of biochar in improving agricultural productivity in desertified soils, providing yield-related data for promoting biochar application in desertified areas. Furthermore, by optimizing improvement programs and comprehensively considering data from soil nutrient content, organic carbon content, and crop characteristics, the study can systematically evaluate the effectiveness of biochar in desertified soil improvement. Based on experimental results, the optimal biochar addition amount can be determined, suitable crop varieties can be selected, and corresponding cultivation and management measures can be formulated, providing scientific guidance for the efficient improvement and sustainable utilization of desertified soils.

[0046] Desert soils are generally characterized by low organic carbon content, high mineral content, and strong alkalinity. Existing technologies are mostly based on the carbon sequestration mechanisms of conventional soils, but research on biochar-mineral carbon interactions and carbon sequestration pathways under extreme drought conditions in desert soils is insufficient. This invention utilizes a short-term incubator planting experiment to simulate outdoor conditions, controlling a single variable to evaluate the carbon sequestration capacity of biochar applied to desert soils. The incubator can precisely control environmental parameters such as temperature, humidity, photoperiod, and aeration, specifically simulating typical characteristics of desert soils such as drought, large diurnal temperature variations, and low organic matter content. This avoids interference from complex field environments and ensures that the observation of biochar carbon sequestration effects is only affected by preset variables. While the carbon cycle rate in desert soils is slow, this invention can accelerate the reaction process through optimized conditions, obtaining dynamic data such as soil organic carbon content, soil nutrient content, and crop-characterized carbon mineralization rates in a short period. This allows for rapid assessment of biochar carbon sequestration potential, avoiding the time cost of long-term field monitoring.

[0047] As a high-carbon material, biochar's net increase in total soil carbon after addition directly reflects its actual carbon retention effect. By comparing changes in total soil carbon content before and after cultivation, and combining different biochar addition amounts, carbon sequestration efficiency and other results can be calculated, avoiding errors caused by natural carbon fluctuations. Inorganic carbon accounts for 10% to 30% of desert soils, directly affecting the accuracy of carbon sequestration assessments. By measuring total carbon and organic carbon separately, the true organic carbon sequestration brought by biochar can be separated, avoiding interference from inorganic carbon dynamics in the results.

[0048] Changes in soil organic carbon content are the core carrier of biochar carbon sequestration. It is mainly retained in the soil to form a carbon pool through passive and active sequestration. Passive sequestration refers to the direct retention of the inert carbon structure of biochar itself, such as aromatic rings and graphitized carbon, in the soil, forming a stable carbon pool, which is mainly reflected by the increase in the total amount of organic carbon. Active sequestration refers to the improvement of soil structure, adsorption protection or inhibition of microbial decomposition, changes in pH and nutrient environment, reduction of the mineralization of the original organic carbon, and indirect improvement of carbon stability. In the incubator experiment, the dynamic changes of total carbon and organic carbon content can be measured periodically to compare and analyze the dynamic balance of carbon input-sequestration-loss.

[0049] In summary, this invention comprehensively evaluates the carbon sequestration efficiency and total carbon content changes of biochar, as well as the stability and forms of carbon in the soil, by focusing on a comparative analysis of total carbon content and organic carbon content. An elemental analyzer is used to measure total carbon content to address the question of how much carbon biochar adds, while a soil nutrient analyzer is used to measure soil organic carbon content to address the question of the stable form of this carbon. The combination of these two methods allows for a comprehensive assessment of the carbon sequestration efficiency and total carbon content changes of biochar, as well as the stability and forms of carbon in the soil. The elemental analyzer accurately measures the increase in total carbon in the soil before and after biochar addition using a combustion method, clarifying the total carbon contribution of biochar. The soil nutrient analyzer, combined with the potassium dichromate oxidation method, quantifies the proportion and stability of organic carbon. By coupling total carbon content and form data, the occurrence state of biochar carbon in the soil (such as the proportion stably existing in the form of inert carbon) can be determined, avoiding the "overestimation of carbon sequestration efficiency" caused by a single total carbon analysis. For example, if the incremental carbon exists primarily in an active form, it is easily decomposed by microorganisms, resulting in limited actual carbon sequestration. Conversely, if the total carbon content increases significantly but the increase in organic carbon content is small, it may indicate that some carbon in the biochar exists in an inorganic form rather than as effectively sequestered organic carbon. The two complement each other under controlled laboratory conditions, providing a scientific basis for evaluating the effectiveness of biochar carbon sequestration, studying its mechanisms, and optimizing its applications. This is particularly suitable for monitoring carbon dynamics in desert soils with low organic carbon and high inorganic carbon. Simultaneously, observing and measuring morphological indicators such as crop height and stem diameter provides a comprehensive understanding of the impact of biochar on crop growth and development. Clarifying whether biochar can promote crop growth and improve crop conditions provides a reference for screening crop varieties suitable for growth in desertified soils and responding well to biochar. Assessing the role of biochar in improving agricultural productivity in desertified soils provides yield-related data for promoting biochar application in desertified areas.

[0050] Analysis of the first round of experiments (first experimental cycle) showed that the retention rate of biochar in the soil was approximately 70%-95% of the initial applied amount. The increased active carbon pool (MBC / DOC) in the normal fertilization group (second experimental soil in the second experimental cycle) in the second round of experiments (second experimental cycle) revealed a positive chain of nutrient input → plant growth → root carbon secretion → microbial activity, verifying the coupling effect of "fertilization-carbon input-microbial turnover". The decomposition potential of residual microorganisms in the microbial fertilizer group (first experimental soil in the second experimental cycle) on the original soil carbon (inhibited by biochar adsorption) highlighted the interaction mechanism between functional microbial communities and biochar. For example, the activity of carbon-decomposing bacteria is constrained by the surface characteristics of biochar, providing a target for designing microbial formulations that "promote carbon fixation and inhibit decomposition". The stability of soil organic carbon (TOC) in the normal fertilization group stemmed from the continuous presence of inert carbon in biochar and the dynamic replenishment of active carbon in the roots. In contrast, the fertilization-stopped group relied on the "carbon stock maintenance" of biochar. This provided a database of parameters for the soil carbon stability assessment model. The soil organic carbon (TOC) could still be maintained under fertilization-stopped conditions, which provided experimental evidence for the "carbon anchoring" mechanism of biochar.

[0051] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for detecting the carbon sequestration capacity of soil biochar, characterized in that, include: Step S100: Obtain sample soil by sampling soil from several preset locations; Several soil sampling points are located within the same desertification area; the sampled soil is used for biochar carbon sequestration testing. Step S200: The sample soil is evenly distributed to obtain several groups of soil; the weight of each group of soil is equal. Step S300: According to the preset fertilizer addition ratio corresponding to each group of soil, apply the corresponding ratio of biochar and microbial fertilizer to each group of soil to obtain several groups of experimental soil. Step S400: Divide each group of experimental soils into equal parts to obtain the first and second experimental soils corresponding to each group of experimental soils. Step S500: Take out a preset weight of experimental soil from the first and second experimental soils corresponding to each group of experimental soils, and determine the taken-out experimental soil as unplanted sample soil. Step S600: Plant the same number and type of plants in the first and second experimental soils corresponding to each group of experimental soils that meet the plant planting requirements, and place the first and second experimental soils corresponding to each group of experimental soils in the same cultivation environment. Step S700: Every preset sampling period, take out a preset weight of experimental soil from the first and second experimental soils corresponding to each group of experimental soils, and determine the taken-out experimental soil as planting sample soil, until the number of sampling periods meets the preset period threshold. Step S701: After the number of sampling cycles meets the preset cycle threshold, remove all plants planted in the experimental soil. Step S702: According to the preset fertilizer addition ratio corresponding to each group of experimental soils, apply the corresponding proportions of biochar and microbial fertilizer to the second experimental soil corresponding to each group of experimental soils, and execute step S500. Step S800: Detect the carbon content and element content of several unplanted soil samples and several planted soil samples corresponding to each group of experimental soils to obtain the total carbon content, organic carbon content, and element content of each group of experimental soils. Step S900: Analyze the trends of total carbon content, organic carbon content, and elemental content of the experimental soils in several groups to determine the biochar carbon sequestration of the sample soils. Wherein, step S800 includes steps S810-S870: Step S810: Grind several unplanted soil samples and several planted soil samples corresponding to each group of experimental soils, filter them through a 100-mesh sieve, and measure the total carbon content of each unplanted soil sample and each planted soil sample after filtration using an elemental analyzer. Step S820: The average of several total carbon contents of several unplanted soil samples or several planted soil samples corresponding to any group of experimental soils is determined as the total carbon content corresponding to that group of experimental soils. Step S830: Take 0.5 g of sieved soil sample from each of the unplanted soil samples and planted soil samples corresponding to each group of experimental soils, and air dry them naturally. Place the air-dried sieved soil sample into a digestion tube, add potassium dichromate sulfuric acid solution to the digestion tube, shake well, and then place the digestion tube into a high-temperature digestion furnace. Digest at 180 to 190 degrees Celsius for 30 minutes to oxidize the organic carbon in the sieved soil sample. After digestion, remove the digestion tube, cool it, add water, add an indicator, titrate with ferrous sulfate standard solution, and calculate the organic carbon content in the sieved soil sample based on the volume of ferrous sulfate standard solution consumed. Step S840: The average organic carbon content in the sieved soil samples of several unplanted soil samples or several planted soil samples corresponding to any group of experimental soils is determined as the organic carbon content corresponding to that group of experimental soils. Step S850: Take 5 grams of soil sample from each of the unplanted soil samples and the planted soil samples corresponding to each group of experimental soils. Place each soil sample into a centrifuge tube and add 2 mol / L potassium chloride solution to each centrifuge tube. Shake and extract for 30 minutes. After centrifugation or filtration, obtain the soil extract corresponding to each soil sample. Put the preset volume of extract into a colorimetric tube, add Nessler's reagent and shake well. Place in the dark for 10 to 15 minutes to allow ammonium nitrogen to react with Nessler's reagent to generate a yellow or brown complex. Then, use a spectrophotometer to measure the absorbance of the yellow or brown complex solution at a wavelength of 420 nm and calculate the content of ammonium nitrogen in each soil sample according to the standard curve. Step S860: Take 5 grams of soil sample from each of the unplanted soil samples and the planted soil samples corresponding to each group of experimental soils, and air dry them naturally. Add sodium bicarbonate extraction solution with a pH of 8.5 to each air-dried soil sample, shake and extract for 30 minutes, filter to obtain the available phosphorus extract corresponding to each soil sample, put the preset volume of available phosphorus extract into a colorimetric tube, add molybdenum antimony reagent mixed colorimetric reagent in sequence, shake well and place at room temperature for 30 minutes to allow phosphorus to react with molybdenum antimony reagent to form a blue complex, then use a spectrophotometer to measure the absorbance of the blue complex solution at a wavelength of 700 nm, and calculate the available phosphorus content in each soil sample according to the standard curve. Step S870: Take 5 grams of soil sample from each of the unplanted soil samples and the planted soil samples corresponding to each group of experimental soils, and air dry them naturally. Add 1 mol / L ammonium acetate solution to each air-dried soil sample, shake and extract for 30 minutes, and then filter to obtain the available potassium extract corresponding to each soil sample. Place each available potassium extract in a flame photometer to measure the characteristic spectral intensity of potassium ion emission, and calculate the available potassium content in each soil sample according to the standard curve.

2. The method according to claim 1, characterized in that, Step S100 includes: Step S110: Remove the topsoil at a preset depth at each preset location soil sampling point; the distance between any two adjacent soil sampling points meets the requirements of a preset sampling distance range; Step S120: Collect the same weight of soil samples from each of the soil sampling points; Step S130: Mix several soil samples to obtain mixed soil; Step S140: Filter the mixed soil through a sieve with a preset mesh size to obtain a sample soil that has been filtered through the sieve.

3. The method according to claim 2, characterized in that, Step S300 includes: Step S310: No biochar and microbial fertilizer are applied to the first group of grouped soils to obtain the first group of experimental soils; In the second group of soil samples, 3 grams of biochar were applied per 100 grams of soil to obtain the second group of experimental soils. In the third group of soil samples, 3 grams of biochar were applied per 100 grams of soil to obtain the third group of experimental soil. In the fourth group of soil samples, 0.5 grams of microbial fertilizer were applied per 100 grams of soil to obtain the fourth group of experimental soil. In the fifth group of soil samples, 3 grams of biochar and 0.5 grams of microbial fertilizer were applied per 100 grams of soil to obtain the fifth group of experimental soil. In the group of soils described in the sixth group, 3 grams of biochar and 1 gram of microbial fertilizer were applied per 100 grams of soil to obtain the experimental soil of the sixth group. In the seventh group of soils, 5 grams of biochar and 0.5 grams of microbial fertilizer were applied per 100 grams of soil to obtain the seventh group of experimental soils. In the eighth group of soils, 5 grams of biochar and 1 gram of microbial fertilizer were applied per 100 grams of soil to obtain the eighth group of experimental soils. In the grouped soils described in the ninth group, 10 grams of biochar and 0.5 grams of microbial fertilizer were applied per 100 grams of soil to obtain the ninth group of experimental soils. In the tenth group of soils, 10 grams of biochar and 1 gram of microbial fertilizer were applied per 100 grams of soil to obtain the tenth group of experimental soils. Specifically, the soil groups in the first, third to tenth groups are set to meet the requirements for plant cultivation, while the soil groups in the second group are set to not meet the requirements for plant cultivation.

4. The method according to claim 3, characterized in that, Step S500 includes: Step S510: Determine the first or second experimental soil corresponding to any group of experimental soils as the soil to be sampled; Step S520: Collect experimental soil samples at a preset depth and volume at the four apex and center positions of the soil to be sampled. Step S530: Mix several experimental soil samples of the collected soil to be sampled to obtain unplanted sample soil corresponding to the soil to be sampled.

5. The method according to claim 4, characterized in that, The temperature range of the first and second experimental soils corresponding to the experimental soils was 23 degrees Celsius to 27 degrees Celsius, the relative humidity range was 60% to 70%, the carbon dioxide concentration was the atmospheric concentration, the light intensity was 4000 illuminance, the light cycle was 12 hours of light and 12 hours of darkness per day, and the watering frequency was once every 2 to 3 days.

6. The method according to claim 5, characterized in that, After step S600, the method further includes: Step S610: After planting plants in the first and second experimental soils corresponding to each group of experimental soils for the first preset number of days, obtain the number of germinated seeds of the plants planted in the first and second experimental soils corresponding to each group of experimental soils. Step S620: Determine the percentage of the ratio of the number of germinated seeds of plants planted in the first or second experimental soil corresponding to each group of experimental soils to the number of plant seeds planted in the first or second experimental soil as the seed germination rate of the first or second experimental soil. Step S630: After planting plants in the first and second experimental soils corresponding to each group of experimental soils for a second preset number of days, obtain the number of germinating seeds of the plants planted in the first and second experimental soils corresponding to each group of experimental soils; the second preset number of days is greater than the first preset number of days. Step S640: Determine the seed germination rate of the first or second experimental soil as the percentage of the number of germinating seeds of plants planted in the first or second experimental soil corresponding to each group of experimental soils.

7. The method according to claim 6, characterized in that, After step S700, the method further includes: Step S710: Determine the target sample soil from several planting soil samples obtained in the last sampling cycle. Step S720: Take 5 grams of soil from each of the target soil samples and each of the unplanted soil samples, and place them in 25 ml containers. Add 12.5 ml of distilled water to each container, seal them, and shake continuously at 150 rpm for 2 minutes. After removal, let them stand for 30 minutes, and use a pH meter to detect the upper suspension of each of the target soil samples and each of the unplanted soil samples to obtain the corresponding pH of each of the target soil samples and each of the unplanted soil samples.

8. The method according to claim 7, characterized in that, After the number of sampling cycles meets the preset cycle threshold, one plant is randomly selected from several plants planted in the first and second experimental soils corresponding to each group of experimental soils. The plant is washed, the underground part is cut off, the water is absorbed with filter paper, and the plant is weighed to obtain the fresh weight of the plant. Then, the plant is placed in an environment of 105 degrees Celsius for blanching, and then placed in an environment of 65 degrees Celsius for drying to constant weight. The dried plant is weighed to obtain the dry weight of the plant.

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