Corrosion-promoting and carbon-retaining agent as well as preparation method, application and verification method thereof

Abstract

The invention discloses a decay-promoting and carbon-retaining agent and a preparation method, application and a verification method thereof. The decay-promoting and carbon-retaining agent comprises a complex microbial inoculant and a nutrient preparation, the complex microbial inoculant comprises the following substances in parts by weight: 2 parts of aspergillus oryzae, 4 parts of saccharomyces cerevisiae, 3 parts of bacillus subtilis, 2 parts of lactic acid bacteria, 4 parts of Koxime saccharomycetes, 3 parts of acetobacter aceti, 4 parts of aspergillus candidus, 1 part of deuteromycetes and 1 part of arthrobacter; the nutrient preparation comprises the following substances in parts by weight: 5 parts of urea, 2 parts of diammonium phosphate and 1.3 parts of potassium sulfate. According to the method, the method for verifying the effect of mixed application of the straw and the decay-promoting and carbon-retaining agent to the soil is constructed, and the 13C isotope tracing technology is combined to verify the SOC immobilization effect of the decay-promoting and carbon-retaining agent on the soil with different textures, so that the situation that the decay-promoting and carbon-retaining agent with different components can achieve more effective SOC immobilization on the soil with the different textures is obtained, and straw resources are fully utilized.

Description

Technical Field

[0001] The present invention belongs to the field of decay-promoting carbon-preserving agents, and specifically relates to a decay-promoting carbon-preserving agent, a preparation method, an application method, and a verification method thereof. Background Art

[0002] As a by-product in the process of agricultural production, crop straw is rich in active carbon and various medium and trace elements, and has potential reuse value. However, in traditional agricultural practices, a large amount of crop straw is directly burned or discarded as agricultural waste, resulting in serious waste of resources and environmental pollution; scientifically and reasonably using crop straw, such as returning crop straw to the field, can effectively improve soil fertility and optimize soil nutrient status, thus ensuring the yield of food crops. However, the main problems faced in this process are the relatively low decomposition rate of straw and its carbon sequestration efficiency, especially in sandy soils with a clay and silt content of less than 15%; due to the inherent defects of sandy soils such as loose structure, easy leakage of water and fertilizer, and low nutrient levels, the decomposition of returned straw is more difficult, which has become an important obstacle restricting the sustainable development of agriculture. Traditional application of compound microbial agents can promote the effective decomposition of straw by increasing the number of microorganisms; however, a large amount of nutrients are required for microorganisms to decompose straw, which requires the supplementation of corresponding nutrient preparations in actual operation to maintain the nutritional conditions required for microbial activities; therefore, the present invention proposes an innovative strategy, that is, combining compound microbial agents with suitable nutrient preparations to develop a new type of decay-promoting carbon-preserving agent, and maximizing the role of straw through scientific and effective methods, in order to achieve long-term stable storage of soil organic carbon and improve the overall productivity of the soil. To sum up, the present invention aims to provide an efficient and environmentally friendly solution to solve the problems existing in the prior art, that is, how to effectively utilize crop straw, especially under sandy soil conditions, to achieve the best soil fertility improvement effect and environmental protection goal. Summary of the Invention

[0003] The present invention provides a decay-promoting carbon-preserving agent, a preparation method, an application method, and a verification method thereof to solve the defects in the prior art.

[0004] The present invention is realized through the following technical solutions:

[0005] A decay-promoting carbon-preserving agent, comprising a compound microbial agent and a nutrient preparation;

[0006] The compound microbial agent comprises the following substances in parts by weight: 2 parts of Aspergillus oryzae, 4 parts of Saccharomyces cerevisiae, 3 parts of Bacillus subtilis, 2 parts of lactic acid bacteria, 4 parts of Candida kefyr, 3 parts of Acetobacter, 4 parts of Aspergillus candidus, 1 part of Deuteromycetes, 1 part of Arthrobacter;

[0007] The nutrient preparation comprises the following substances in parts by weight: 5 parts of urea, 2 parts of diammonium phosphate, 1.3 parts of potassium sulfate.

[0008] A preparation method of a carbon-promoting and decay-accelerating agent, comprising the following steps:

[0009] Step 1: Weigh aspergillus oryzae, saccharomyces cerevisiae, bacillus subtilis, lactic acid bacteria, candida kefyr, acetobacter, aspergillus candidus, deuteromycetes and arthrobacter according to the ratio, mix them and send them into a ball mill to be pulverized at 25 °C for 10 min, and then pass through a 100-mesh sieve for packaging to obtain a compound bacterial agent;

[0010] Step 2: Weigh urea, diammonium phosphate and potassium sulfate according to the ratio, mix and pulverize them, and then pass through a 100-mesh sieve for packaging to obtain a nutrient preparation.

[0011] An application of a carbon-promoting and decay-accelerating agent, wherein the compound bacterial agent, the nutrient preparation and straw are mixed together and applied to the soil to increase the soil organic carbon content; the addition amount of the compound bacterial agent is 5% of the straw weight, the addition amount of the nutrient preparation is 0.83% of the straw weight, and the addition amount of the straw applied to the soil is 1.2% of the total soil weight.

[0012] For the application of a carbon-promoting and decay-accelerating agent as described above, the soil is loess soil and aeolian sandy soil.

[0013] A verification method of a carbon-promoting and decay-accelerating agent, comprising the following steps:

[0014] Step 1: Soil sample collection;

[0015] Step 2: 13 14C-labeled straw;

[0016] Step 3: Indoor cultivation;

[0017] Step 4: Soil detection and analysis;

[0018] Step 5: Calculate relevant data and conduct statistical analysis.

[0019] For the verification method of a carbon-promoting and decay-accelerating agent as described above, the specific operation for obtaining straw in Step 2 is: The 13 14C-labeled corn straw used in this study is obtained through 13 a 14C pulse labeling experiment. When the corn plants grow to the jointing stage, they are subjected to 13 14CO 2 pulse labeling; by reacting H 2 2SO 4 (0.5 M) with Na 2 13 214CO 3 (99% atom% 13 14C, Sigma-Aldrich) to generate 13 14CO 2 gas, and 13 14CO2 Gas was injected into the marking chamber, and the fan was turned on to fully mix the gas in the marking chamber, and marking began. The marking lasted for about 7 hours. The corn plants were harvested at maturity and rinsed, withered at 105°C for 30 minutes, and dried at 60°C to constant weight. Subsequently, the root stubble and stems were separated with scissors, cut into small pieces, and crushed with a straw crusher, and then passed through a 2mm sieve for later use. In addition, a small amount of the crushed residue was taken and crushed with a hybrid grinder (Retsch MM 200, Germany) to determine its basic physical and chemical properties. The physical and chemical properties of the tested corn straw are shown in Table 1.

[0020] The verification method of the above-mentioned corrosion-promoting carbon-retaining agent, the specific operation of the indoor cultivation in the step 3 is: the test group weighs 200g of soil sample into a 250mL sealed plastic jar, adds deionized water to adjust to 50% of the field water holding capacity, and pre-cultivates at 25°C for 7 days to stabilize the activity of soil microorganisms; after the pre-cultivation, according to the treatment content 13 C-labeled straw and decay-promoting carbon-retaining agents were added to soil samples according to the ratio and mixed quickly. Then, the soil moisture content was adjusted to 70% of the water holding capacity with deionized water and cultured at 25°C in the dark for 90 days. At the same time, a control group and a blank group were set up. Only the same weight of straw was added to the soil samples of the control group, while no substance was added to the soil samples of the blank group. The remaining operations of the control group and the blank group were the same as those of the experimental group.

[0021] In the verification method of the above-mentioned corrosion-promoting carbon-retaining agent, the soil detection and analysis in step 4 includes: soil carbon dioxide (CO 2 ) detection, soil organic carbon (SOC) detection, soil mineral nitrogen detection, soil total nitrogen detection, soil total phosphorus detection, soil available phosphorus detection, soil microbial biomass carbon detection, soil microbial biomass nitrogen detection, soil extracellular enzyme activity detection and soil PLFA detection.

[0022] The soil CO 2 The specific operation of collection and analysis is as follows: a sealed plastic jar containing soil samples is placed with a 50 mL beaker containing 20 mL of 1 M NaOH solution to capture the released CO 2 On the 1st, 2nd, 3rd, 4th, 6th, 8th, 11th, 14th, 18th, 22nd, 28th, 35th, 42nd, 49th, 59th, 75th, and 90th day of culture, the NaOH-Na 2 CO 3 The solution was removed from the beaker and replaced with fresh NaOH solution; 2 CO 3 Add excess 0.5M BaCl 2The solution is precipitated, titrated with 0.5 M HCl solution using phenolphthalein as an indicator to quantitatively determine NaOH and thus obtain the CO 2 content; collect all BaCO 3 precipitates and repeatedly rinse with deionized water, and obtain clean BaCO 3 by centrifuging at 5000 r / min, dry it at 50 °C, grind and weigh it into a tin boat, and measure its δ 13 C value on an isotope ratio mass spectrometer (DELTA V Advantage, Thermo Fisher Scientific, Germany); at the same time, each time the NaOH solution is changed, it is necessary to ventilate for 30 min to maintain aerobic conditions.

[0023] The detection of soil organic carbon described above adopts the external heating method with potassium dichromate; use an isotope ratio mass spectrometer to determine soil carbon isotope;

[0024] The detection of total nitrogen in the soil described above is determined by the Kjeldahl method;

[0025] The detection of mineral nitrogen in the soil described above is determined using a continuous flow analyzer for NH 4 + -N and NO 3- -N after extraction with 1 M KCl (soil:solution = 1:10), and calculate soil mineral nitrogen as the sum of the two;

[0026] The detection of total phosphorus in the soil described above adopts the HClO 4 -H 2 SO 4 method for determination;

[0027] The detection of available phosphorus in the soil described above is extracted with 0.5 M NaHCO 3 and then determined by using a continuous flow analyzer;

[0028] The detection of soil microbial biomass carbon described above is carried out by the chloroform fumigation extraction method. Weigh 10 g each of the fumigated and non-fumigated soil samples, and extract with 0.5 M K 2 SO4 (soil:solution = 1:10); determine its organic carbon content with a total organic carbon analyzer; quantify with the total organic carbon measured in the K 2 SO 4 extract of the non-fumigated soil sample; calculate soil microbial biomass carbon as the extractable C difference between the fumigated and corresponding non-fumigated soil samples and correct it with a correction factor, and the correction factor k EC = 0.45;

[0029] The detection of soil microbial biomass nitrogen described above is carried out by the chloroform fumigation extraction method. Weigh 10 g each of the fumigated and non-fumigated soil samples, and extract with 0.5 M K 2SO4 extraction (soil:solution = 1:10); determine its nitrogen content using a flow analyzer; soil microbial biomass nitrogen is calculated as the difference in extractable N between fumigated and corresponding non-fumigated soil samples, and is corrected by a correction factor, the correction factor k EN = 0.54;

[0030] The specific operation for detecting the extracellular enzyme activity of the soil is as follows: Weigh 1 g of fresh soil into 125 ml of ultrapure water, and shake it at 220 rpm for 30 min to make a soil slurry; then place the sample, enzyme substrate, reference standard, and buffer in a specific well plate; that is, transfer 150 μL of the soil slurry and 50 μL of the 200 μM enzyme substrate into a 96-well microplate. Add 150 μL of the soil slurry and 50 μL of ultrapure water to the blank well, and add 150 μL of the soil slurry and 50 μL of the standard substrate of 4-methylumbelliferone or 7-amino-4-methylcoumarin (10 μM) to the quenching well. At the same time, appropriately set negative wells and reference wells in the microplate. Then incubate the microplate in the dark at 25 °C for 4 h, and terminate the reaction with NaOH solution; measure the fluorescence intensity with a microplate reader (Spark, TECAN, China) at an excitation wavelength of 365 nm and an emission wavelength of 450 nm. The enzyme activity unit is expressed in nmol g -1 soil h -1 represented;

[0031] The specific operation for detecting soil PLFA is as follows: Weigh 2 g of fresh soil stored at -80 °C, add chloroform-methanol-citrate buffer (20 mL, volume ratio 1:2:0.8, pH 4.0) for extraction to extract lipids; separate the total lipid extract on a silica column. After gentle alkaline methanolysis, phospholipids are methylated into their fatty acid methyl esters; use a gas chromatograph equipped with a MIDI Sherlock microbial identification system to separate and identify FAMEs, and use methyl nonadecanoate fatty acid as an internal standard to quantify the phospholipid concentration; the following PLFAs are used as markers for bacteria and fungi: Firmicutes (i14:0, i15:0, i16:0, i17:0, i18, a15:0, a16:0, a17:0, a18:0, a19:0), Actinomycetes (10Me16:0, 10Me17:0, and 10Me18:0), the sum of Firmicutes and Actinomycetes is used as Gram-positive bacteria (G + ), Gram-negative bacteria (G -: cy17: 0, cy19: 0, 16: 1ω7, 16: 1ω9, 17: 1ω8, and 18: 1ω7); Arbuscular mycorrhizal fungi (AMF: 16: 1ω5c), saprophytic fungi (18: 1ω9c), Ascomycota and Basidiomycota (18: 2ω6c), non-specific PLFAs (14: 0, 15: 0, 16: 0, 17: 0, 18: 0, 20: 0, 20: 4ω6,9,12,15); Bacterial biomarkers are calculated as the sum of G + and G - ; Fungal biomarkers are calculated as the sum of AMF, saprophytic fungi, and non-specific fungi (18: 3ω6,9,12); PLFA content is used to estimate soil microbial abundance.

[0032] A verification method for a carbon-promoting and decay-preserving agent as described above. The relevant data calculated in step five include: CO 2 content calculation, distinguishing the source of CO 2 , priming effect (PE) calculation, SOC content calculation, and quantification of net C sequestration;

[0033] The calculation of the CO 2 content is as follows:

[0034]

[0035] In the formula, CO 2 is the amount of SOC mineralized and released during the incubation period (mg C g -1 ); V 0 is the volume of standard hydrochloric acid consumed during blank calibration (mL); V is the volume of standard hydrochloric acid consumed during sample titration (mL); c HCl is the concentration of standard hydrochloric acid (mol L -1 ); m is the soil mass (g); a% is the soil water content;

[0036] The specific operation for distinguishing the source of CO 2 is as follows: Calculate the amount of CO 2 from straw and the amount of CO 2 from the original soil organic matter using the mass balance equation. The specific calculation formulas are as follows:

[0037]

[0038] CO 2 SOC = CO 2 total - CO 2 straw (3)

[0039] Among them, CO 2straw , CO 2SOCand CO 2total respectively refer to the amount of CO from the straw source in straw treatment, 2 the amount of CO from the original soil organic carbon source, 2 and the total CO amount; δ 2 CO 13 CO 2total and δ 13 CO 2 soil respectively refer to the δ 2 C values of the total CO amount in the treatment with added straw and the corresponding treatment without added straw; δ 13 C 13 C straw refers to the δ 13 C value of the added straw itself; the cumulative amount of CO from the straw source and the cumulative amount of CO from the original soil organic carbon source 2 are respectively the sum of the release amounts of the CO amount from the straw source and the CO amount from the original soil organic carbon source within each sampling interval; 2 2 2 2 SOC The calculation of the priming effect induced after adding straw is as follows:

[0040]

[0041] PE = CO 2 SOC - CO 2 soil (4)

[0042] where CO 2soil refers to the total CO amount in the treatment without added straw; 2 amount;

[0043] The calculation of the SOC content is as follows:

[0044]

[0045] where V 0 refers to the volume of ferrous sulfate used in titrating the blank (mL). V refers to the volume of ferrous sulfate used in titrating the sample (mL). N refers to the concentration of standard ferrous sulfate (mol L -1 -1). 3 refers to the molar mass of 1 / 4 carbon atom (g mo1 -1 -1).

[0046] The calculation formula for the SOC content of the straw source after adding straw is as follows:

[0047]

[0048] where SOC straw and SOC total respectively refer to the SOC content of the straw source and the total SOC content in the treatment with added straw; δ13 C total and δ 13 C soil respectively refer to the δ 13 C values of the total SOC in the treatments with and without straw addition; δ 13 C straw refers to the δ 13 C value of the added straw itself;

[0049] The net C sequestration in the soil mentioned above is the difference between the residual straw-derived SOC (SOC straw ) after straw addition and the amount of carbon lost due to PE, and the calculation formula is as follows:

[0050] Net C change = SOC straw - PE (7)

[0051] After the above calculations, two-way ANOVA is used to determine the main effects and interaction effects of soil type and carbon-promoting and carbon-preserving agents on total CO 2 emission, CO 2 from different sources, PE, net SOC balance, SOC content, and soil / microbial properties; LSD test is used to compare the means to estimate whether the differences are significant, and the significance level is p < 0.05; if the effects of both soil type and carbon-promoting and carbon-preserving agents are significant, then η 2 is calculated as a parameter to represent the contribution of each factor to the total effect size, and the specific calculation formula is as follows:

[0052] η 2 = SS A / SS total (8)

[0053] where SS A is the variance between treatments of factor A, and SS total is the total sum of squares; all the above statistical analyses are performed using IBM SPSS version 19.0.

[0054] The advantages of the present invention are as follows: By constructing a method for verifying the effect of mixing straw and carbon-promoting and carbon-preserving agents applied to the soil, combined with 13 the C isotope labeling technique, the present invention verifies the effect of carbon-promoting and carbon-preserving agents on SOC sequestration in soils with different textures, thereby obtaining which types of soils with different textures can be more effectively sequestered by carbon-promoting and carbon-preserving agents containing different components, and realizing the full utilization of straw resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0056] Figure 1 It is a schematic diagram of the sampling locations and morphologies of two soils in the verification test of the present invention;

[0057] Table 1 shows the initial properties of two soils in the verification test of the present invention;

[0058] Figure 2 Figure (a) shows the total CO2 content of Lou soil and Aeolian sandy soil during the entire cultivation period in the verification test of the present invention. 2 Schematic diagram of release rate; Figure (b) is the total CO release rate of Lou soil and windy sandy soil during the entire culture period in the verification test of the present invention. 2 Schematic diagram of the cumulative release; Figure (c) is a bar graph of the straw-source CO2 release in the Lou soil and the wind-blown sandy soil during the entire cultivation period in the verification test of the present invention. 2 Schematic diagram of release rate; Figure (d) is a diagram of straw-derived CO2 release rate in Lou soil and sandy soil during the entire cultivation period in the verification test of the present invention. 2 Schematic diagram of the cumulative release; Figure (e) is a bar graph of the straw-source CO2 release in the Lou soil and sandy soil during the entire cultivation period in the verification test of the present invention. 2 Schematic diagram of release rate; Figure (f) is a diagram of straw-derived CO release rate in Lou soil and sandy soil during the entire culture period in the verification test of the present invention. 2 Schematic diagram of the cumulative release amount;

[0059] Figure 3 It is a bar diagram showing the cumulative release of PE from Lou soil and wind-blown sand during the entire culture period in the verification test of the present invention;

[0060] Figure 4 It is a columnar schematic diagram of the fate of straw carbon in Lou soil and Aeolian sandy soil after 90 days of cultivation in the verification test of the present invention;

[0061] Figure 5 The middle figure (a) is a column diagram of the net SOC fixation of Lou soil and aeolian sandy soil after 90 days of cultivation in the verification test of the present invention; Figure (b) is a column diagram of the total SOC content of Lou soil and aeolian sandy soil after 90 days of cultivation in the verification test of the present invention;

[0062] Table 2 shows the changes in TN, Min-N, TP, AP, MBC and MBN contents of Lou soil and aeolian sandy soil after 90 days of cultivation in the verification test of the present invention;

[0063] Figure 6Figure (a) is a schematic diagram of the C cycle hydrolase activity of Lou soil and sandy soil after 90 days of cultivation in the verification test of the present invention; Figure (b) is a schematic diagram of the N cycle hydrolase activity of Lou soil and sandy soil after 90 days of cultivation in the verification test of the present invention; Figure (c) is a schematic diagram of the P cycle hydrolase activity of Lou soil and sandy soil after 90 days of cultivation in the verification test of the present invention;

[0064] Figure 7 The middle figure (a) is a bar diagram showing the total PLFA abundance of Lou soil and aeolian sandy soil after 90 days of cultivation in the verification test of the present invention; the figure (b) is a bar diagram showing the total abundance of the main microbial groups in Lou soil and aeolian sandy soil after 90 days of cultivation in the verification test of the present invention;

[0065] Figure 8 This is a schematic diagram of the main microorganisms in Lou soil and Aeolian sandy soil after 90 days of cultivation in the verification test of the present invention. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. 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.

[0067] Example

[0068] Step 1: according to the proportion of 2 parts of Aspergillus oryzae, 4 parts of Saccharomyces cerevisiae, 3 parts of Bacillus subtilis, 2 parts of lactic acid bacteria, 4 parts of Saccharomyces cerevisiae, 3 parts of Acetobacter, 4 parts of Aspergillus kawachii, 1 part of Fungi Deuteromyces, and 1 part of Arthrobacter, the mixture is weighed and sent into a ball mill for crushing at 25° C. for 10 minutes, and then sieved through a 100-mesh sieve to obtain a composite bacterial agent;

[0069] Step 2: Weigh urea, diammonium phosphate and potassium sulfate in the ratio of 5 parts of urea, 2 parts of diammonium phosphate and 1.3 parts of potassium sulfate, mix and grind, then pass through a 100-mesh sieve and pack to obtain a nutrient preparation.

[0070] Verification test

[0071] 1. Soil Sample Collection

[0072] We collected the Lou soil and aeolian sandy soil required for the experiment in June 2021. The Lou soil was collected from the long-term positioning experiment without straw returning treatment at the Institute of Agricultural Water Saving in Arid Areas, Northwest A&F University, Shaanxi Province (34°17′38″N, 108°04′02″E). The altitude of this area is 525 m, belonging to the continental monsoon semi-humid climate. The annual average temperature is 13 °C, and the annual average precipitation is 635 mm. Moreover, 60% of the annual precipitation is concentrated in July - September, and the annual evaporation is 990 mm. The soil type is calcareous soil mat dry cultivated anthropogenic soil; the aeolian sandy soil was collected from Yulin City, Shaanxi Province (38°22'50″N, 109°45'27″E). The altitude of this area is 1090 m, belonging to the temperate semi-arid continental monsoon climate. The annual average temperature is 10.7 °C, the annual average precipitation is 412.4 mm, the annual evaporation is 1200 - 2000 mm, and the annual frost-free period is 150 d. According to the Chinese soil classification system, the soil type is aeolian sandy soil of the primary soil order; according to the American system, the soil type is sandy soil of the newly formed quartz sandy soil class FAO. Both the Lou soil and aeolian sandy soil were collected from the 0 - 20 cm surface soil. After transporting the fresh soil back to the laboratory, carefully remove plant residues, roots, and identifiable gravel and debris, homogenize and sieve (<2 mm), and then air-dry for the incubation experiment; the basic properties of the two soils are shown in Table 1, and the sampling locations and morphologies of the two soils are as Figure 1 shown.

[0073] 2. 13 13C-labeled corn straw

[0074] The 13 13C-labeled corn straw used in this study was obtained through 13 a 13C pulse labeling experiment. When the corn plants grew to the jointing stage, they were 13 13CO 2 pulse labeled; through H 2 2SO 4 (0.5 M) reacting with Na 2 13 13CO 3 (99% atom% 13 13C, Sigma - Aldrich) to produce 13 13CO 2 gas, and 13 13CO 2Inject gas into the labeling chamber, start the fan to fully mix the gas in the labeling chamber, and start labeling. The labeling duration is about 7 h. Harvest corn plants at the maturity stage and rinse them clean. Blanch at 105 °C for 30 min and dry to a constant weight at 60 °C. Subsequently, separate the root stubble and stems and leaves with scissors, cut them into small pieces, crush them with a straw crusher, and sieve through a 2-mm sieve for later use. In addition, take a small amount of the crushed residue and further crush and grind it with a mixer mill (Retsch MM200, Germany) to determine its basic physical and chemical properties. The physical and chemical properties of the tested corn straw are shown in Table 1.

[0075] Table 1 Basic properties of the tested soil and corn straw

[0076]

[0077] 3. Experimental design and laboratory incubation experiment

[0078] This invention adopts a laboratory constant-temperature incubation experiment with two soil types (Lou soil vs. aeolian sandy soil) and ways of adding carbon-promoting and decay-preserving agents (only adding 13 ¹³C-labeled straw, i.e., M; 13 ¹³C-labeled straw + carbon-promoting and decay-preserving agent, i.e., MA), with a total of 4 treatments, repeated 3 times. In addition, a control (CK) without adding straw and carbon-promoting and decay-preserving agent is set; the addition amount of straw is 12 g·kg -1 ⁻¹ soil, equivalent to applying 15000 kg·ha -1 ⁻¹ straw in the field experiment; carbon-promoting and decay-preserving agent: the addition amount of the compound microbial agent is 5% of the straw weight, and the addition amount of the nutrient preparation is 0.83% of the straw weight.

[0079] The specific operation is as follows: Weigh 200 g of soil samples into 250-mL sealed plastic jars, add deionized water to adjust to 50% of the field water holding capacity, and pre-incubate at 25 °C for 7 d to stabilize the soil microbial activity; after the pre-incubation, add straw and nutrient preparations to Lou soil and aeolian sandy soil respectively according to the treatment content, adjust the soil water content to 70% of the water holding capacity with deionized water, and at the same time directly adjust the soil water content to 70% of the field water holding capacity with deionized water in the treatments without adding nutrient preparations (CK, M), and incubate for 90 d under dark conditions at 25 °C.

[0080] 4. Soil CO 2 Collection and analysis

[0081] A 50-mL small beaker is placed in the sealed plastic jar containing soil samples, and 20 mL of 1 M NaOH solution is added to capture the released CO 2 ₂. Take out the NaOH-Na2 CO 3 beaker of the solution and replace with fresh NaOH solution; in the collected NaOH-Na 2 CO 3 solution, add an excess of 0.5 M BaCl 2 solution for precipitation, use phenolphthalein as an indicator, titrate with 0.5 M HCl solution to quantify NaOH and thus quantify CO 2 content; collect all BaCO 3 precipitate and repeatedly rinse with deionized water, centrifuge at 5000 r / min to obtain clean BaCO 3 and dry at 50 °C, grind and weigh into a tin boat, and measure its δ 13 C value on an isotope ratio mass spectrometer (DELTA V Advantage, Thermo Fisher Scientific, Germany). It should be noted that each time the NaOH solution is replaced, it is necessary to aerate for 30 min to maintain aerobic conditions.

[0082] 5. Soil analysis

[0083] After the incubation, destructive sampling is carried out for each treatment. Part of the soil is stored in a -80 °C refrigerator for soil microbial analysis, part is stored at 4 °C, and the remaining soil samples are air-dried for subsequent determination and analysis. The determination of soil organic carbon (SOC) is by the external heating method with potassium dichromate; the soil carbon isotope (δ 13 C) is measured using an isotope ratio mass spectrometer (DELTA V Advantage, Thermo Fisher Scientific, Germany); total soil nitrogen (TN) is determined by the semi-micro Kjeldahl method; NH 4 + -N and NO 3- -N after 1 M KCl extraction (soil:solution = 1:10) are determined using a continuous flow analyzer (AA3, SEAL, Germany), and mineral nitrogen is calculated as the sum of the two; total soil phosphorus (TP) is determined by the HClO 4 -H 2 SO 4 method; available phosphorus (AP) in the soil is extracted with 0.5 M NaHCO 3 and then determined using a continuous flow analyzer (AA3, SEAL, Germany); soil microbial biomass C (MBC) and microbial biomass N (MBN) are determined using the chloroform fumigation extraction method; weigh 10 g each of the fumigated and non-fumigated soil samples, and use 0.5 M K 2SO4 extraction (soil:solution = 1:10); the organic carbon content was determined using a total organic carbon analyzer (vario MACRO cube, elementar, Germany), and the nitrogen content was determined using a flow analyzer; MBC or MBN was calculated as the difference in extractable C or N between fumigated and corresponding non-fumigated soil samples and corrected by a correction factor (k EC = 0.45, k EN = 0.54).

[0084] 6. Analysis of soil extracellular enzyme activity

[0085] Soil extracellular enzyme activity usually indirectly characterizes microbial activity and can also provide evidence for soil C and nutrient transformation mechanisms; therefore, after the incubation experiment, the activities of 6 hydrolytic enzymes were measured according to the methods of [reference methods], namely the enzymes involved in the C cycle, β-Glucosidase (BG), Cellubiosidase (CBH), Xylosidase (XYL), the N cycle enzymes Glucosaminidase (NAG), Aminopeptidase (LAP), and the P cycle enzyme Phosphatase (PHO); all soil extracellular enzyme activities were measured in 96-well microplates; the standard substrates for BG, CBH, XYL, NAG, and PHO were 4-methylumbelliferone, and the standard substrate for LAP was 7-amino-4-methylcoumarin; specifically, 1 g of fresh soil was weighed into 125 ml of ultrapure water and shaken at 220 rpm for 30 min to prepare a soil slurry; then the samples, enzyme substrates, reference standards, and buffers were placed in specific microplates; that is, 150 μL of soil slurry and 50 μL of 200 μM enzyme substrate were transferred into a 96-well microplate, 150 μL of soil slurry and 50 μL of ultrapure water were added to the blank wells, and 150 μL of soil slurry and 50 μL of the standard substrate of 4-methylumbelliferone or 7-amino-4-methylcoumarin (10 μM) were added to the quenching wells. At the same time, negative wells and reference wells were appropriately set in the microplate. Then the microplate was incubated in the dark at 25 °C for 4 h, and the reaction was terminated with NaOH solution; the fluorescence was measured using a microplate reader (Spark, TECAN, China) at an excitation wavelength of 365 nm and an emission wavelength of 450 nm, and the enzyme activity unit was expressed as nmol g -1 soil h -1 is expressed as.

[0086] 7. Determination of soil PLFA

[0087] After the incubation, the phospholipid fatty acid (PLFA) method described by Bardgett et al. and Yuan et al. was used to extract, isolate, and purify soil microbial PLFAs to evaluate the soil microbial community composition. Briefly, 2 g of fresh soil stored at -80 °C was weighed and extracted with chloroform-methanol-citrate buffer (20 mL, volume ratio 1:2:0.8, pH 4.0) to extract lipids; the total lipid extract was separated on a silica column, and after mild alkaline methanolysis, the phospholipids were methylated to their fatty acid methyl esters (FAMEs). FAMEs were separated and identified using a gas chromatograph (N6890, 0. Agilent, Santa Clara, CA, USA) equipped with a MIDI Sherlock microbial identification system (version 4.5; MIDI, Newark, DE, USA). The phospholipid concentration was quantified using methyl nonadecanoate fatty acid (19:0) as an internal standard; the following PLFAs were used as markers for bacteria and fungi: Firmicutes (i14:0, i15:0, i16:0, i17:0, i18, a15:0, a16:0, a17:0, a18:0, a19:0), Actinobacteria (10Me16:0, 10Me17:0, and 10Me18:0), and the sum of Firmicutes and Actinobacteria was used as Gram-positive bacteria (G + ), Gram-negative bacteria (G - : cy17:0, cy19:0, 16:1ω7, 16:1ω9, 17:1ω8, and 18:1ω7); arbuscular mycorrhizal fungi (AMF: 16:1ω5c), saprophytic fungi (18:1ω9c), Ascomycota and Basidiomycota (18:2ω6c), non-specific PLFAs (14:0, 15:0, 16:0, 17:0, 18:0, 20:0, 20:4ω6,9,12,15); bacterial biomarkers were calculated as the sum of G + and G - ; fungal biomarkers were calculated as the sum of AMF, saprophytic fungi, and non-specific fungi (18:3ω6,9,12); PLFA content was used to estimate soil microbial abundance.

[0088] 8. Calculation

[0089] 8.1 Distinguish the sources of CO 2 and calculate PE

[0090] (1) The content of the described CO 2 was calculated as follows:

[0091]

[0092] In the formula, CO 2 is the mineralization release amount of SOC during incubation (mg C g -1);V 0 is the volume of standard hydrochloric acid consumed during blank calibration (mL); V is the volume of standard hydrochloric acid consumed during sample titration (mL); c HCl is the concentration of standard hydrochloric acid (mol L -1 ); m is the soil mass (g); a% is the soil water content;

[0093] (2) We use the mass balance equation to calculate the amount of CO 2 emitted from the straw source (CO 2straw ) and the amount of CO 2 emitted from the original soil organic matter source (CO 2SOM ):

[0094]

[0095] CO 2 SOC = CO 2 total - CO 2 straw (3)

[0096] Among them, CO 2straw , CO 2SOC and CO 2total refer to the amount of CO 2 emitted from the straw source, the amount of CO 2 emitted from the original soil organic carbon source, and the total amount of CO 2 respectively; δ 13 CO 2total and δ 13 CO 2 soil refer to the δ 2 C values of the total amount of CO 13 in the straw-added treatment and the corresponding straw-free treatment respectively; δ 13 C straw refers to the δ 13 C value of the added straw itself; The cumulative amount of CO 2 emitted from the straw source and the cumulative amount of CO 2 emitted from the original soil organic carbon source are the sum of the amounts of CO 2 emitted from the straw source and the amounts of CO 2 emitted from the original soil organic carbon source within each sampling interval;

[0097] (3) Calculate the induced PE after adding straw according to the following equation:

[0098] PE = CO 2 SOC - CO 2 soil (4)

[0099] Among them, CO2soil Refers to the total CO without straw treatment 2 amount;

[0100] 8.2 Distinguish the sources of SOC and quantify the net soil C balance

[0101] (1) The SOC content is calculated as follows:

[0102]

[0103] Where, V 0 refers to the volume of ferrous sulfate used in titrating the blank (mL). V refers to the volume of ferrous sulfate used in titrating the sample (mL). N refers to the concentration of standard ferrous sulfate (mol L -1 ) 3 refers to the molar mass of 1 / 4 carbon atom (g mo1 -1 )

[0104] (2) The formula for calculating the SOC content of the straw source after adding straw is as follows:

[0105]

[0106] Where, SOC straw and SOC total respectively refer to the SOC content of the straw source and the total SOC content in the straw addition treatment; δ 13 C total and δ 13 C soil respectively refer to the δ 13 C values of the total SOC amounts of adding straw and the corresponding treatment without adding straw; δ 13 C straw refers to the δ 13 C value of the added straw itself;

[0107] (3) The net C sequestration in the soil is the difference between the residual straw-source SOC (SOC straw ) after adding straw and the amount of carbon lost from SOC caused by PE, and the calculation formula is as follows:

[0108] Net C change = SOC straw -PE (7)

[0109] 8. Statistical analysis

[0110] Two-way ANOVA is used to determine the effects of soil type and carbon-promoting and carbon-preserving agents on the total CO 2 emission, CO from different sources 2, the main and interactive effects of PE, net SOC balance, SOC content, and soil / microbial properties; the least significant difference (LSD) test was used to compare the means to estimate whether the differences were significant, with a significance level of p < 0.05; if the effects of both soil type and the carbon-promoting and decay-retarding agent were significant, then η 2 was calculated as a parameter to represent the contribution of each factor to the total effect size, and the specific calculation formula is as follows:

[0111] η 2 = SS A / SS total

[0112] where SS A is the variance between treatments of factor A, and SS total is the total sum of squares; all of the above statistical analyses were performed using IBM SPSS version 19.0.

[0113] Verification test analysis and conclusions

[0114] 1 Changes in the cumulative release amounts of soil total CO 2 , straw-derived CO 2 , and original SOM-derived CO 2 After 90 days of incubation, compared with the control, the cumulative release amounts of total CO

[0115] in Lou soil and Aeolian sandy soil increased by 278.36 - 284.32 mg C g 2 SOC and 383.53 - 390.93 mg C g -1 SOC, respectively; regardless of the soil type, compared with adding straw alone, the combination with the carbon-promoting and decay-retarding agent increased the cumulative release amount of soil total CO -1 2 by 1.62% and 1.61%, respectively; meanwhile, Aeolian sandy soil released more total CO 2 2 (as shown in Figures (a) and (b) below, where the error bars on the bar charts represent the standard error of the mean (n = 4); different lowercase letters within the same group indicate significant differences between different treatments of the same soil; different uppercase letters indicate significant differences between the two soil types; p < 0.05; CK, no straw and carbon-promoting and decay-retarding agent added; M: only straw added; MA: straw + carbon-promoting and decay-retarding agent added). Figure 2 The carbon-promoting and decay-retarding agent improved the decomposition ability of straw in Lou soil and Aeolian sandy soil by 8.08% and 9.83%, respectively; the ability of straw to be degraded into CO

[0116] in Aeolian sandy soil was 47.34% higher than that in Lou soil (as shown in 2 Figure 2 ​As shown in Figures (c) and (d) of the middle figure, compared with adding only straw, the combination of straw and the carbon-promoting and decay-preserving agent weakened the mineralization of the original SOM, reducing it by 6.06% and 12.56% respectively. In addition, the cumulative mineralization of the original SOM in Lou soil was slightly higher than that in Aeolian sandy soil by 2.45% (as Figure 2 shown in Figures (e) and (f) of the middle figure).

[0117] 2 Soil priming effect

[0118] During the 90-day incubation period, whether adding only straw or the combination of straw and the carbon-promoting and decay-preserving agent had a positive priming effect on both Lou soil and Aeolian sandy soil (as Figure 3 shown in Figure (a) of the middle figure); the carbon-promoting and decay-preserving agent reduced the PE induced by straw in Lou soil and Aeolian sandy soil by 8.98% and 43.98% respectively; meanwhile, the induced PE in Aeolian sandy soil was higher than that in Lou soil (as Figure 3 shown, where different lowercase letters within the same group indicate significant differences among different treatments of the same soil, and different uppercase letters indicate significant differences between the two soil types; p < 0.05; CK, no straw and carbon-promoting and decay-preserving agent added; M: only straw added; MA: straw + carbon-promoting and decay-preserving agent added).

[0119] 3 Straw fate and net SOC balance

[0120] Straw carbon mineralization, straw-derived SOC formation, and the proportion of residual undecomposed straw (as Figure 4 shown), where the mineralization of corn straw in Aeolian sandy soil was higher than that in Lou soil, and the formation of straw-derived SOC was lower than that in Lou soil. At the same time, 32% - 35% and 32% - 36% of the undecomposed components of straw remained in Lou soil and Aeolian sandy soil respectively; however, the presence of the carbon-promoting and decay-preserving agent increased the straw carbon mineralization in both soils, thus enhancing the transformation and decomposition of straw in both soils and reducing the residual amount of undecomposed straw.

[0121] Adding only straw or applying the carbon-promoting and decay-preserving agent in combination both resulted in net SOC sequestration; compared with adding only straw, the combination of the carbon-promoting and decay-preserving agent further increased the net SOC sequestration in Lou soil and Aeolian sandy soil, being more conducive to soil carbon sequestration. This gain phenomenon was mainly caused by reducing the SOC loss (PE) in Lou soil and Aeolian sandy soil (the increase effect of straw-derived SOC was not significant); it should be noted that the carbon sequestration effect of the carbon-promoting and decay-preserving agent on Aeolian sandy soil was much better than that on Lou soil, with the net SOC sequestration being 6 times higher than that of adding only straw (as Figure 5 shown in Figure (a) of the middle figure). Therefore, compared with adding only straw, the combination of straw and the carbon-promoting and decay-preserving agent significantly increased the SOC content in Lou soil and Aeolian sandy soil by 0.17 g kg -1 and 0.41 g kg -1 (as Figure 5 shown in Figure (b) of the middle figure); 4 Soil nutrients

[0122] Compared with adding only straw, the combined use of a straw decomposition and carbon preservation agent significantly increased the available nutrient content in Lou soil and aeolian sandy soil (p < 0.05). Among them, the available nutrient content in aeolian sandy soil was significantly higher than that in Lou soil (Table 2, where M: adding only straw; MA: adding straw + straw decomposition and carbon preservation agent). The soil microbial biomass (MBC, MBN) in aeolian sandy soil was significantly lower than that in Lou soil (Table 2); compared with adding only straw, the combined use of a straw decomposition and carbon preservation agent significantly increased MBC and MBN in Lou soil and aeolian sandy soil (p < 0.05) (Table 2);

[0123] Table 2 Total nitrogen, mineral nitrogen, total phosphorus, available phosphorus, microbial biomass carbon and microbial biomass nitrogen contents in Lou soil and aeolian sandy soil after 90 days of incubation and two-way ANOVA

[0124]

[0125]

[0126] Note: Two-way ANOVA was used to evaluate the differences between these variables (ns: not significant; *, **, and *** indicate p < 0.05, p < 0.01, and p < 0.001, respectively).

[0127] 5 Soil hydrolase activity

[0128] Overall, the hydrolase activity in Lou soil was higher than that in aeolian sandy soil (as shown in Figures (a), (b), and (c) below, where CK: no straw and decomposer added; M: adding only straw; MA: adding straw + straw decomposition and carbon preservation agent); under the condition of adding straw, the straw decomposition and carbon preservation agent significantly increased the activity of carbon cycle hydrolases in Lou soil ( Figure 6 a), but had no significant effect on the activity of nitrogen cycle hydrolases, while the opposite phenomenon occurred in aeolian sandy soil ( Figure 6 b); at the same time, the compound microbial agent increased the phosphatase activity in Lou soil but decreased the phosphatase activity in aeolian sandy soil ( Figure 6 c). Figure 6 c).

[0129] 6 Soil total PLFAs

[0130] Regarding the change in the total PLFA content, in the presence of straw, the straw decomposition and carbon preservation agent increased the PLFA contents of bacteria and fungi in both Lou soil and aeolian sandy soil; at the same time, the PLFA contents of bacteria and fungi in aeolian sandy soil were significantly lower than those in Lou soil; in addition, bacteria had an advantage over fungi in PLFA in all treatments (Lou soil: 74.64 nmol g -1 vs. 20.65 nmol g -1 ; aeolian sandy soil: 31.50 nmol g -1 vs. 9.39 nmol g -1 )(asFigure 7 As shown in Figures (a) and (b) in the middle, where CK: no straw and decomposer added; M: only straw added; MA: straw + carbon-preserving decomposing agent added; G+: Gram-positive bacteria, G-: Gram-negative bacteria); among them, the presence of the carbon-preserving decomposing agent significantly increased the contents of Firmicutes, Ascomycota and Basidiomycota in the Lou soil, but only significantly increased the content of Ascomycota and Basidiomycota in the aeolian sandy soil (as Figure 8 shown, where different lowercase letters within the same group indicate significant differences among different treatments under the total distribution of each microorganism; M: only straw added (Lou soil); MA: straw + carbon-preserving decomposing agent added).

[0131] 7 Conclusions

[0132] In this invention, aeolian sandy soil and Lou soil with the same parent material of soil formation in the Loess Plateau region but different textures and physical and chemical properties are selected. Intending to use the well-textured Lou soil as a comparison, the potential of SOC sequestration in aeolian sandy soil is improved through organic materials combined with a carbon-preserving decomposing agent, providing empirical evidence for formulating scientific and reasonable management strategies in arid and semi-arid regions of the world, especially in agricultural areas mainly composed of sandy soil. Compared with only adding straw, the combination of straw and a carbon-preserving decomposing agent significantly improved the decomposition and mineralization ability of the returned straw in both soils (as Figure 4 shown), which indicates that the carbon-preserving decomposing agent plays an important role in the decomposition process of exogenous organic materials. Functional microorganisms such as yeast and Bacillus subtilis introduced by the carbon-preserving decomposing agent release a large amount of hydrolases that can degrade cellulose and lignin, which can control the rate and degree of straw decomposition, release and convert elements such as N and P in the straw into available forms, thereby increasing the content of soil mineral nutrients, alleviating the nutrient demand of soil microorganisms, and slowing down the mineralization and decomposition of the original SOC by microorganisms (the lower PE generated after the combination of straw and the carbon-preserving decomposing agent shown in the invention, as shown in Figure (a) in Figure 3 ). Soil net C sequestration is regulated by the mineralization of the original SOC (PE) and the accumulation of new SOC (straw-derived SOC); in this invention, net SOC sequestration occurred whether or not the carbon-preserving decomposing agent was added, which means that the increase in straw-derived SOC exceeded the loss of the original soil SOC; among them, compared with only adding straw, the combination of straw and the carbon-preserving decomposing agent increased the net SOC sequestration in Lou soil and aeolian sandy soil by 22.1% and 641% respectively (as shown in Figure (a) in Figure 4 ). The above results emphasize the importance of the combination of organic materials and the carbon-preserving decomposing agent in this invention. Especially in sandy soils with a rough texture, it can increase the decomposition and utilization of organic materials and alleviate the mineralization of the original SOC, thereby optimizing the carbon sequestration efficiency and improving SOC sequestration.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A corrosion-promoting and carbon-retaining agent, characterized in that: Including compound bacterial agents and nutrient preparations; The composite bacterial agent comprises the following substances in parts by weight: 2 parts of Aspergillus oryzae, 4 parts of Saccharomyces cerevisiae, 3 parts of Bacillus subtilis, 2 parts of lactic acid bacteria, 4 parts of Saccharomyces cerevisiae, 3 parts of Acetobacter, 4 parts of Aspergillus kawachii, 1 part of Fungi Deuteromyces, and 1 part of Arthrobacter; The nutrient preparation comprises the following substances in parts by weight: 5 parts of urea, 2 parts of diammonium phosphate, and 1.3 parts of potassium sulfate.

2. The method for preparing a corrosion-promoting carbon-retaining agent according to claim 1, characterized in that: The steps include: Step 1: Weigh Aspergillus oryzae, Saccharomyces cerevisiae, Bacillus subtilis, lactic acid bacteria, Saccharomyces cerevisiae, Acetobacter, Aspergillus kawachii, Fungi aspergillus and Arthrobacter according to the ratio, mix them, put them into a ball mill, grind them at 25° C. for 10 minutes, and then pass through a 100-mesh sieve to obtain a composite bacterial agent; Step 2: Weigh urea, diammonium phosphate and potassium sulfate according to the ratio, mix and grind, then pass through a 100-mesh sieve and pack to obtain the nutrient preparation.

3. The use of a corrosion promoting and carbon retaining agent according to claim 1, characterized in that: The composite bacterial agent, nutrient preparation and straw are mixed together and applied to the soil to increase the soil organic carbon content; the addition amount of the composite bacterial agent is 5% of the weight of the straw, the addition amount of the nutrient preparation is 0.83% of the weight of the straw, and the addition amount of the straw applied to the soil is 1.2% of the total weight of the soil.

4. The use of a corrosion promoting and carbon retaining agent according to claim 1, characterized in that: The soil is Lou soil and aeolian sandy soil.

5. The verification method of a corrosion-promoting carbon-retaining agent according to claim 1, characterized in that: The steps include: Step 1: Soil sample collection; Step 2: 13 C marks the straw; Step 3: Indoor cultivation; Step 4: Soil testing and analysis; Step 5: Calculate relevant data and conduct statistical analysis.

6. The verification method of a corrosion-promoting carbon-retaining agent according to claim 5, characterized in that: This study used 13 C-marked corn stover is 13 C pulse labeling experiment was performed. 13 CO2 pulse labeling; H2SO4 (0.5M) and Na2 13 CO3(99%atim% 13 C, Sigma-Aldrich) 13 CO2 gas, 13 CO2 gas was injected into the marking chamber, and the fan was turned on to mix the gas in the marking chamber thoroughly. The marking began and the marking lasted for about 7 hours. The corn plants were harvested at maturity and rinsed, withered at 105°C for 30 minutes, and dried at 60°C to constant weight. Subsequently, the root stubble and stems were separated with scissors, cut into small pieces, and crushed with a straw crusher, and then passed through a 2mm sieve for later use. In addition, a small amount of the crushed residue was taken and crushed with a hybrid grinder (Retsch MM 200, Germany) to determine its basic physical and chemical properties. The physical and chemical properties of the tested corn straw are shown in Table 1.

7. The verification method of a corrosion-promoting carbon-retaining agent according to claim 5, characterized in that: The specific operation of the indoor cultivation in step 3 is as follows: the test group weighed 200g of soil sample into a 250mL sealed plastic jar, added deionized water to adjust to 50% of the field water holding capacity, and pre-cultured at 25°C for 7 days to stabilize the activity of soil microorganisms; after the pre-culture, the soil samples were treated according to the content. 13 C-labeled straw and decay-promoting carbon-retaining agents were added to soil samples according to the ratio and mixed quickly. Then, the soil moisture content was adjusted to 70% of the water holding capacity with deionized water and cultured at 25°C in the dark for 90 days. At the same time, a control group and a blank group were set up. Only the same weight of straw was added to the soil samples of the control group, while no substance was added to the soil samples of the blank group. The remaining operations of the control group and the blank group were the same as those of the experimental group.

8. The verification method of a corrosion-promoting carbon-retaining agent according to claim 5, characterized in that: The soil detection and analysis in step 4 includes: soil carbon dioxide (CO2) detection, soil organic carbon (SOC) detection, soil mineral nitrogen (mineral nitrogen) detection, soil total nitrogen detection, soil total phosphorus detection, soil available phosphorus detection, soil microbial biomass carbon detection, soil microbial biomass nitrogen detection, soil extracellular enzyme activity detection and soil PLFA detection.

9. The verification method of a corrosion-promoting carbon-retaining agent according to claim 8, characterized in that: The specific operation of soil CO2 collection and analysis is as follows: a 50mL small beaker containing 20mL 1M NaOH solution is placed in a sealed plastic jar containing soil samples to capture released CO2; the beaker containing NaOH-Na2CO3 solution is taken out and replaced with fresh NaOH solution on the 1st, 2nd, 3rd, 4th, 6th, 8th, 11th, 14th, 18th, 22nd, 28th, 35th, 42nd, 49th, 59th, 75th, and 90th day of cultivation; an excess of 0.5M BaCl2 solution is added to the collected NaOH-Na2CO3 solution for precipitation; phenolphthalein is used as an indicator and titrated with 0.5M HCl solution to quantify NaOH and thereby obtain the CO2 content; all BaCO3 precipitates are collected and repeatedly rinsed with deionized water, clean BaCO3 is obtained under centrifugation at 5000r / min and dried at 50°C, ground and weighed into a tin boat, and measured on an isotope ratio mass spectrometer (DELTAVvantage, Thermo Fisher Scientific, Inc., New York, NY) Scientific, Germany) to determine its δ 13 C value; at the same time, ventilation for 30 minutes is required each time the NaOH solution is replaced to maintain aerobic conditions. The soil organic carbon detection adopts potassium dichromate external heating method; Soil carbon isotopes were measured using isotope ratio mass spectrometry; The soil total nitrogen detection is determined using the Kjeldahl method; The soil mineral nitrogen test uses a continuous flow analyzer to measure the ammonium nitrogen (NH4 + -N) and nitrate nitrogen (NO3 - -N), and soil mineral nitrogen was calculated as the sum of the two; The soil total phosphorus detection is determined by HClO4-H2SO4 method; The soil available phosphorus test was extracted with 0.5M NaHCO3 and then measured by a continuous flow analyzer; The soil microbial biomass carbon detection is carried out by chloroform fumigation extraction method. 10 g of fumigated and unfumigated soil samples are weighed and extracted with 0.5 M K2SO4. The organic carbon content is determined by a total organic carbon analyzer. The total organic carbon measured in the K2SO4 extract of the unfumigated soil sample is used for quantification. The soil microbial biomass carbon is calculated as the extractable C difference between the fumigated and corresponding non-fumigated soil samples, and is corrected by a correction factor, the correction factor k EC =0.45; The soil microbial biomass nitrogen detection is carried out by chloroform fumigation extraction method. 10 g of fumigated and unfumigated soil samples are weighed and extracted with 0.5 M K2SO4 (soil: solution = 1: 10). The nitrogen content is determined by flow analyzer. The soil microbial biomass nitrogen is calculated as the difference in extractable N between the fumigated and corresponding non-fumigated soil samples, and is corrected by a correction factor, the correction factor k EN =0.54; The specific operation of the soil extracellular enzyme activity detection is as follows: weigh 1g of fresh soil in 125ml of ultrapure water, shake at 220rpm for 30min to make soil slurry; then place the sample, enzyme substrate, reference standard and buffer in a specific well plate; that is, 150μL of soil slurry and 50μL of 200μM enzyme substrate are transferred into a 96-well microplate, 150μL of soil slurry and 50μL of ultrapure water are added to the blank well, 150μL of soil slurry and 50μL of 4-methylumbelliferone or 7-amino-4-methylcoumarin (10μM) standard substrate are added to the quenching well, and negative wells and reference wells are appropriately set in the microplate. Then, the microplate is incubated at 25℃ in the dark for 4h, and the reaction is terminated with NaOH solution; the fluorescence is measured with an ELISA reader (Spark, TECAN, China) at 365nm excitation and 450nm emission, and the enzyme activity unit is nmol g -1 soil -1 express; The specific operation of soil PLFA detection is as follows: weigh 2g of fresh soil stored at -80°C, add chloroform-methanol-citrate buffer (20mL, volume ratio 1:2:0.8, pH 4.0) was used to extract lipids; the total lipid extract was separated on a silica column, and after mild alkaline methanolysis, the phospholipids were methylated to their fatty acid methyl esters; FAMEs were separated and identified using a gas chromatograph equipped with a MIDISherlock microbial identification system, and the phospholipid concentration was quantified using nonadecanoic acid methyl ester fatty acid as an internal standard; the following PLFAs were used as markers for bacteria and fungi: Firmicutes (i14: 0, i15: 0, i16: 0, i17: 0, i18, a15: 0, a16: 0, a17: 0, a18: 0, a19: 0), Actinomycetes (10Me16: 0, 10Me17: 0 and 10Me18: 0), and the sum of Firmicutes and Actinomycetes as Gram-positive bacteria (G + ), Gram-negative bacteria (G - :cy17:0,cy19:0,16:1ω7,16:1ω9,17:1ω8 and 18:1ω7); arbuscular mycorrhiza (AMF: 16:1ω5c), saprophytic fungi (18:1ω9c), ascomycetes and basidiomycetes (18:2ω6c), non-specific PLFA (14:0,15:0,16:0,17:0,18:0,20:0,20:4ω6,9,12,15); bacterial biomarkers were calculated as G + , G - The fungal biomarkers were calculated as the sum of AMF, saprophytic fungi and non-specific fungi (18:3ω6,9,12); PLFA content was used to estimate soil microbial abundance.

10. The verification method of a corrosion-promoting and carbon-retaining agent according to claim 5, characterized in that: The relevant data calculated in step 5 include: CO2 content calculation, differentiation of CO2 sources, PE calculation, SOC content calculation, and quantification of net C fixation; The CO2 content is calculated as follows: Where CO2 is the mineralization release of SOC during the culture period (mg C g -1 ); V0 is the volume of standard hydrochloric acid consumed during blank calibration (mL); V is the volume of standard hydrochloric acid consumed during sample titration (mL); c HCl is the standard hydrochloric acid concentration (mol L -1 ); m is soil mass (g); a% is soil water content; The specific operation of distinguishing the source of CO2 is to use the mass balance equation to calculate the amount of CO2 from straw and the amount of CO2 from original soil organic matter. The specific calculation formula is as follows: WHAT 2SOC =WHAT 2total -WHAT 2straw (3) Among them, CO 2straw , CO 2SOC and CO 2total They refer to the amount of CO2 from straw in the straw addition treatment, the amount of CO2 from the original soil organic carbon source, and the total amount of CO2; δ 13 CO 2total and δ 13 CO 2soil The total CO2 content of the treatment with straw addition and the treatment without straw addition is δ 13 C value; δ 13 C straw Refers to the added straw itself 13 C value; the cumulative amount of CO2 from straw and the cumulative amount of CO2 from original soil organic carbon are the sum of the release amounts of CO2 from straw and CO2 from original soil organic carbon in each sampling interval; The calculation of the excitation effect induced by adding straw is as follows: PE=CO 2SOC -CO 2soil (4) Among them, CO 2soil Refers to the total CO2 amount without adding straw; The SOC content is calculated as follows: Where V0 refers to the volume of ferrous sulfate used in the blank titration (mL). V refers to the volume of ferrous sulfate used in the sample titration (mL). N refers to the standard ferrous sulfate concentration (mol L -1 )3 refers to the molar mass of 1 / 4 carbon atom (g mo1 -1 ) The calculation formula of the SOC content of the straw source after adding straw is as follows: Among them, SOC straw and SOC total They refer to the straw source SOC content and total SOC content in the straw addition treatment; δ 13 C total and δ 13 C soil refers to the δ of the total SOC of the treatment with straw addition and the corresponding treatment without straw addition. 13 C value; δ 13 C straw Refers to the added straw itself 13 C value; The net soil C fixation is the residual straw source SOC (SOC straw ) and the difference between the amount of carbon lost by PE and the SOC loss, calculated as follows: Net C change=SOC straw -OR (7) After completing the above calculations, two-way ANOVA was used to determine the main and interactive effects of soil type and carbon-promoting agents on total CO2 release, CO2 from different sources, PE, net SOC balance, SOC content, and soil / microbial properties; LSD test was used to compare means to estimate whether the differences were significant, with a significance level of p < 0.05; if the effects of soil type and carbon-promoting agents were both significant, η was calculated. 2 As a parameter to represent the contribution of each factor to the total effect size, the specific calculation formula is as follows: η 2 =SS A / SS total (8) Among them, SS A is the variance between treatments of factor A, SS total is the total sum of squares.

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