Method for improving stability of organic carbon reservoir of reclamation soil in mining area

Abstract

The invention belongs to the technical field of mining area land reclamation, and particularly relates to a method for improving the stability of an organic carbon reservoir of mining area reclamation soil. The method comprises the following steps: reclamation treatment: planting food crops in reclamation soil of the mining area from the end of April to the beginning of May every year, and carrying out fertilization treatment before the food crops are planted; after the food crops are mature, the food crops are harvested; removing fruits of the harvested grain crops, crushing the grain crops, and turning and pressing the grain crops into the reclamation soil of the mining area; the fertilization treatment method comprises the following steps: mixing an organic fertilizer and an inorganic fertilizer, and applying the mixture to the reclamation soil of the mining area around the grain crops; wherein the inorganic fertilizer comprises a nitrogenous fertilizer, a phosphatic fertilizer and a potash fertilizer. According to the method for improving the stability of the organic carbon reservoir of the reclamation soil in the mining area, the content of the organic carbon in the reclamation soil in the mining area is remarkably improved, the accumulation mineralization rate of the organic carbon in the soil is not increased, and the method is an effective measure for improving the stability of the organic carbon reservoir of the reclamation soil in the mining area.

Description

Technical Field

[0001] The invention belongs to the technical field of land reclamation in mining areas, and in particular relates to a method for improving the stability of an organic carbon pool in reclaimed soil in mining areas. Background Art

[0002] The soil organic carbon pool is the largest carbon pool in the terrestrial biosphere, more than twice the carbon stored in vegetation biomass and the atmosphere. Soil organic carbon, abbreviated as SOC in English, is considered a key factor in evaluating soil fertility. It is essential to improving soil physical, chemical and biological properties, and can significantly increase crop yields. Increasing soil organic carbon sequestration is considered a win-win strategy for enhancing food security and mitigating global climate change.

[0003] The study found that changes in the stability of the soil organic carbon pool are closely related to the activities of soil microorganisms and the physical protection of soil aggregates. Soil microorganisms act as "carbon pumps" in the soil. They can act as "decomposers" to catalyze the decomposition of soil organic substrates through extracellular enzymes, and they can also ingest and utilize organic matter to synthesize their own biomass. Through the life history of microorganisms, they transport microbial organic carbon to the soil in the form of microbial residues, thereby increasing soil organic carbon sequestration.

[0004] Mine area reclamation refers to a comprehensive project that takes remediation measures on the land damaged during the development of coal and other mineral resources in the mining area, restores its economic value, makes it available for use and improves the surrounding environment. The damaged land that needs to be reclaimed in the coal mining area includes: abandoned mining areas of open-pit mines, internal spoil dumps, external spoil dumps, waste rock mountains, collapsed land, etc. Before reclamation, the reclaimed soil in these mining areas has the characteristics of poor soil physical properties, poor nutrients, poor biological activity, and large spatial variation of nutrients, which leads to uneven crop growth and low crop yields. At present, in order to solve the above-mentioned problems of reclaimed soil in mining areas, soil reclamation in mining areas is an effective measure.

[0005] Soil reclamation in mining areas is to promote the maturation process of barren soil through measures such as land leveling, crop cultivation, and fertilization management, gradually restore the physical, chemical, and biological properties of the soil, and achieve a nutritional cycle balance between plant growth and soil microbial metabolism. Although the existing methods of soil reclamation in mining areas can quickly improve the fertility of reclaimed soil in mining areas and improve the productivity of reclaimed soil in mining areas in a short period of time. However, in the process of quickly improving the fertility of reclaimed soil in mining areas, these methods do not significantly increase the organic carbon content in the reclaimed soil in mining areas, and thus it is not easy to improve the stability of the organic carbon pool in the reclaimed soil in mining areas. Summary of the invention

[0006] In order to solve the problem that in the prior art, in the process of rapidly improving the fertility of the reclaimed soil in the mining area, the degree of improvement of the organic carbon content in the reclaimed soil in the mining area is not obvious, and thus it is difficult to improve the stability of the organic carbon pool in the reclaimed soil in the mining area, the present invention provides a method for improving the stability of the organic carbon pool in the reclaimed soil in the mining area, which significantly improves the organic carbon content in the reclaimed soil in the mining area without increasing the cumulative mineralization rate of soil organic carbon, thereby improving the stability of the organic carbon pool in the reclaimed soil in the mining area.

[0007] To achieve the above purpose, the present invention adopts the following technical solution.

[0008] The present invention provides a method for improving the stability of the organic carbon pool in the reclaimed soil of a mining area, comprising the following steps:

[0009] Reclamation: Plant food crops in the reclaimed soil of the mining area from the end of April to the beginning of May each year, and apply fertilizer before planting food crops. Harvest food crops in autumn each year after they mature; remove the fruits of the harvested food crops, crush them, and then turn them over to the reclaimed soil of the mining area, waiting for the planting of food crops the next year.

[0010] At the end of April or early May of the second year, repeat the above reclamation treatment, and the repetition cycle is 9 to 11 years.

[0011] Planting food crops and harvesting food crops on the reclaimed soil in the mining area every year can repair the reclaimed soil in the mining area. In particular, fertilization before planting food crops has the effect of fertilizing the soil. In addition, the above-mentioned fertilization, planting food crops and harvesting food crops in the reclaimed soil in the mining area have been repeated for 9 to 11 years. Such long-term soil fertilization has the effect of increasing the organic carbon content of the reclaimed soil, increasing the activity of sucrase and / or urease in the reclaimed soil in the mining area, and then promoting the accumulation of fungal and / or bacterial residue carbon and the increase of the unprotected active organic carbon content in large aggregates, and will not increase the soil organic carbon accumulation mineralization rate, thereby improving the stability of the organic carbon pool in the reclaimed soil in the mining area.

[0012] The method of fertilization treatment is: organic fertilizer and inorganic fertilizer are mixed and applied to the reclaimed soil in the mining area around the food crops; the mass ratio of the organic fertilizer and the inorganic fertilizer is 24 to 42:1. When fertilizing the reclaimed soil in the mining area around the food crops, the organic fertilizer and the inorganic fertilizer are mixed according to the above mass ratio and then spread around the soil. The mixed organic fertilizer and inorganic fertilizer can promote the growth of food crops planted in the reclaimed soil in the mining area, enhance the restoration effect of the reclaimed soil in the mining area, increase the organic carbon content of the reclaimed soil in the mining area, and will not increase the cumulative mineralization rate of soil organic carbon.

[0013] The inorganic fertilizer includes nitrogen fertilizer, phosphate fertilizer and potash fertilizer; the mass ratio of N in the nitrogen fertilizer is 42% to 50%, the mass ratio of P2O5 in the phosphate fertilizer is 10% to 14%, and the mass ratio of K2O in the potash fertilizer is 40% to 70%; the application amount of the nitrogen fertilizer is 90kg·hm -2 ~105kg·hm -2 , is based on the mass of N in nitrogen fertilizer; the application rate of phosphate fertilizer is 40kg·hm -2 ~98kg·hm -2 , is based on the mass of P2O5 in the phosphate fertilizer; the application rate of the potash fertilizer is 45kg·hm -2 ~105kg·hm -2 , which is measured by the mass of K2O in potash fertilizer. Nitrogen fertilizer, phosphorus fertilizer and potash fertilizer can promote the growth of food crops and make the reclaimed soil in mining areas have a good repair effect.

[0014] The application amount of the organic fertilizer is 5000kg·hm -2 ~13000kg·hm -2 .

[0015] The organic matter content of the organic fertilizer is 14.97% to 17.07%, and the nitrogen, phosphorus and potassium contents of the organic fertilizer are 0.84% ​​to 1.68%, 0.54% to 1.54% and 0.82% to 1.56% respectively. The organic fertilizer has the function of expanding the capacity and increasing the storage, so that the reclaimed soil in the mining area can restore the carbon sink function as soon as possible.

[0016] Before reclamation, the organic carbon content in the reclaimed soil of the mining area was 4.09 g kg -1 ~4.20g·kg -1 , the total nitrogen content is 0.34g·kg -1 ~0.50g·kg -1 The content of available phosphorus is 2.01 mg kg -1 ~3.03mg·kg -1 , the content of fast-acting potassium is 102.17 mg kg -1 ~106.85mg·kg -1 , pH is 8.30~8.46.

[0017] After reclamation, the organic carbon content in the reclaimed soil of the mining area was 9.10 g kg -1 ~12.74g·kg -1 , the total nitrogen content is 0.71g·kg -1 ~1.30g·kg -1 The content of available phosphorus is 14.96 mg kg -1 ~30.68mg·kg -1, the content of fast-acting potassium is 232.08 mg kg -1 ~417.87mg·kg -1 .

[0018] Before and after reclamation, the organic carbon content in the reclaimed soil of the mining area increased from 4.09 g·kg -1 ~4.20g·kg -1 Increased to 9.10 g kg -1 ~12.74g·kg -1 .

[0019] The method for improving the stability of the organic carbon pool in the reclaimed soil of a mining area provided by the present invention increases the yield of grain crops through the application of organic and inorganic fertilizers, thereby increasing the activity of sucrase and / or urease, promoting the accumulation of carbon in fungal and / or bacterial residues and the increase in the content of unprotected active organic carbon in large aggregates, and will not increase the soil organic carbon accumulation mineralization rate, thereby improving the stability of the organic carbon pool in the reclaimed soil of the mining area.

[0020] Preferably, the application amount of the nitrogen fertilizer is 95 kg·hm -2 ~100.8kg·hm -2 The application amount of the phosphate fertilizer is 45 kg·hm -2 ~92.4kg·hm -2 The application amount of potash fertilizer is 49.2 kg·hm -2 ~100kg·hm -2 .

[0021] The application amount of the organic fertilizer is 6000kg·hm -2 ~12000kg·hm -2 .

[0022] Preferably, the nitrogen fertilizer comprises any one or more of urea, ammonium sulfate, ammonium bicarbonate chloride, diammonium phosphate potassium nitrate and calcium nitrate. Urea, ammonium sulfate, ammonium bicarbonate chloride, diammonium phosphate potassium nitrate and calcium nitrate all have the advantages / effects / functions of carbon retention and nitrogen increase, can provide sufficient enzymatic substrates, thereby increasing the activity of sucrase and / or urease, increasing the organic carbon sequestration of the reclaimed soil in the mining area, thereby increasing the organic carbon content of the reclaimed soil in the mining area, and will not increase the cumulative mineralization rate of soil organic carbon.

[0023] Preferably, the nitrogen fertilizer is urea, and the mass ratio of N in the urea is 45% to 47%.

[0024] Preferably, the phosphate fertilizer includes any one or more of superphosphate, double superphosphate, enriched superphosphate and diammonium phosphate. Superphosphate, double superphosphate, enriched superphosphate and diammonium phosphate all have the effect of fertilizing the soil, can provide sufficient enzymatic substrates for the soil, thereby increasing the activity of sucrase and / or urease, increasing the organic carbon sequestration of the reclaimed soil in the mining area, and thus increasing the organic carbon content of the reclaimed soil in the mining area, and will not increase the cumulative mineralization rate of soil organic carbon.

[0025] Preferably, the phosphate fertilizer is superphosphate, and the mass ratio of P2O5 in the superphosphate is 11% to 13%.

[0026] Preferably, the potash fertilizer includes any one or more of potassium chloride, potassium sulfate, potassium nitrate and potassium dihydrogen phosphate. Potassium chloride, potassium sulfate, potassium nitrate and potassium dihydrogen phosphate all have the advantages of promoting plant growth and development and improving soil structure, and can provide sufficient enzymatic substrates for the soil, thereby increasing the activity of sucrase and / or urease, increasing the organic carbon sequestration of the reclaimed soil in the mining area, and thus increasing the organic carbon content of the reclaimed soil in the mining area, and will not increase the cumulative mineralization rate of soil organic carbon.

[0027] Preferably, the potash fertilizer is potassium chloride, and the mass ratio of K2O in the potassium chloride is 59% to 61%.

[0028] Preferably, the organic fertilizer is fully decomposed chicken manure. Fully decomposed chicken manure has the functions of improving soil fertility, optimizing soil structure and improving soil properties, and can increase soil carbon sequestration, thereby increasing the organic carbon content of the reclaimed soil in the mining area, and will not increase the cumulative mineralization rate of soil organic carbon.

[0029] Preferably, the food crops include spring corn or soybeans.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The present invention provides a method for improving the stability of the organic carbon pool in the reclaimed soil of a mining area. The method provided by the present invention repeatedly reclaims the reclaimed soil of a mining area by planting and harvesting food crops in the reclaimed soil of a mining area for 9 to 11 consecutive years, especially by fertilizing the soil before planting food crops. The accumulation of such long-term fertilization increases the fertility of the reclaimed soil of a mining area over the years, and has the effect of increasing the organic carbon content of the reclaimed soil. When the present invention performs fertilization, organic fertilizer and inorganic fertilizer are mixed and applied to the reclaimed soil of a mining area around the food crops, and the organic fertilizer and inorganic fertilizer are spread in the reclaimed soil of a mining area around the food crops at a specific mass ratio, which not only promotes the growth of food crops planted in the reclaimed soil of a mining area, but also enhances the repair effect of the reclaimed soil of a mining area, and increases the organic carbon content of the reclaimed soil of a mining area, and does not increase the cumulative mineralization rate of soil organic carbon. The method provided by the present invention significantly improves the organic carbon content of the reclaimed soil in the mining area through the growth of food crops and fertilization treatment, and repeats for 9 to 11 consecutive years, and does not increase the cumulative mineralization rate of soil organic carbon, which is an effective measure to improve the stability of the organic carbon pool in the reclaimed soil in the mining area. In addition, the method promotes the accumulation of fungal and / or bacterial residue carbon and the increase of the unprotected active organic carbon content in large aggregates by increasing the activity of sucrase and / or urease, thereby increasing the organic carbon sequestration in the reclaimed soil in the mining area.

[0032] 2. The method provided by the present invention relies on the typical long-term positioning reclamation test site (10 years) in Shanxi Province - the Gujiao test site where the gangue dump area has been reclaimed by covering the soil and the Xiangyuan test site where the coal mining subsidence area has been reclaimed by mixing and pushing. Combined with indoor cultivation, double pool index model, wet screening of aggregates and density grouping, etc., the mineralization and stability characteristics of organic carbon pool in the reclamation soil of the mining area, the changes in soil microbial carbon and enzyme activity, the changes in aggregates and their physical components under different long-term fertilization measures such as no fertilization (CK), chemical fertilizer application (NPK), single application of organic fertilizer (M) and combination of organic and inorganic fertilizers (MNPK) are analyzed to clarify the stability mechanism of the organic carbon pool in the reclamation soil of the mining area. The research results of the present invention show that the combination of organic and inorganic fertilizers significantly increases the organic carbon content of the reclamation soil in the mining area, and does not increase the cumulative mineralization rate of soil organic carbon, which is an effective measure to improve the stability of the organic carbon pool in the reclamation soil of the mining area. However, the soil organic carbon sequestration mechanisms of the two reclamation test sites are not the same. In the Gujiao test site, the application of organic and inorganic fertilizers promoted the accumulation of bacterial residue carbon and the increase of the content of unprotected fine-grained organic carbon (M-fPOC) in large aggregates by increasing the activity of soil urease, thereby increasing the organic carbon sequestration in the reclaimed soil of the mining area; in the Xiangyuan test site, the application of organic and inorganic fertilizers promoted the accumulation of fungal residue carbon and the increase of the content of unprotected coarse-grained organic carbon (M-cPOC) in large aggregates by increasing the activity of sucrase, thereby increasing the organic carbon sequestration in the reclaimed soil of the mining area and the organic carbon content in the reclaimed soil of the mining area, without increasing the soil organic carbon accumulation mineralization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is the organic carbon and total nitrogen content of the reclaimed soil under different fertilization measures in the present invention; wherein, Figure 1 (1) is the organic carbon content of reclaimed soil under different fertilization measures; Figure 1 (2) in the figure is the total nitrogen content of reclaimed soil under different fertilization measures; lowercase letters (a, b, c, d) indicate significant differences among different treatments in the same reclamation test site (P<0.05); uppercase letters (A, B, C, D) indicate significant differences among different reclamation test sites under the same treatment (P<0.05).

[0034] Figure 2 is the mineralization rate of organic carbon in the reclaimed soil under different fertilization measures during the cultivation period of the present invention, wherein, Figure 2 (1) is the mineralization rate of organic carbon in the reclaimed soil of Gujiao experimental site under different fertilization measures; Figure 2 (2) in the figure is the mineralization rate of organic carbon in the reclaimed soil of the Xiangyuan experimental site under different fertilization measures.

[0035] Figure 3 is the cumulative mineralization of organic carbon in reclaimed soil under different fertilization measures in the present invention; wherein, Figure 3(1) is the cumulative mineralization of organic carbon in the reclaimed soil of the Gujiao experimental site under different fertilization measures; Figure 3 (2) in the figure is the cumulative mineralization of organic carbon in the reclaimed soil of the Xiangyuan experimental site under different fertilization measures.

[0036] Figure 4 It is the cumulative mineralization rate of organic carbon in reclaimed soil under different fertilization measures in the present invention.

[0037] Figure 5 is the amino sugar content of the reclaimed soil under different fertilization measures in the present invention; wherein, Figure 5 (1) is the amino mannose content in reclaimed soil under different fertilization measures; Figure 5 (2) is the galactosamine content in the reclaimed soil under different fertilization measures; Figure 5 (3) is the glucosamine content in reclaimed soil under different fertilization measures; Figure 5 (4) is the content of cell wall acid in reclaimed soil under different fertilization measures; Figure 5 (5) in the figure is the total amino sugar content in reclaimed soil under different fertilization measures.

[0038] Figure 6 is the carbon content of fungal and bacterial residues in the reclaimed soil under different fertilization measures in the present invention; wherein, Figure 6 (1) is the carbon content of fungal residues in reclaimed soil under different fertilization measures; Figure 6 (2) in the figure is the carbon content of bacterial residues in reclaimed soil under different fertilization measures.

[0039] Figure 7 It is the content of microbial residue carbon in reclaimed soil under different fertilization measures in the present invention and the contribution of fungal and bacterial residue carbon to microbial residue carbon; wherein, Figure 7 (1) is the carbon content of microbial residues in reclaimed soil under different fertilization measures; Figure 7 (2) in the figure is the contribution of fungal and bacterial residue carbon to microbial residue carbon in reclaimed soil under different fertilization measures.

[0040] Figure 8 It is the contribution of microbial residue carbon in reclaimed soil to soil organic carbon under different fertilization measures in the present invention.

[0041] Fig. 9 It is the activity of β-glucosidase, amylase and sucrase in the reclaimed soil under different fertilization measures in the present invention; wherein, Fig. 9 (1) is the β-glucosidase activity of reclaimed soil under different fertilization measures; Fig. 9 (2) is the amylase activity of reclaimed soil under different fertilization measures; Fig. 9 (3) in the figure is the sucrase activity in reclaimed soil under different fertilization measures.

[0042] Fig.10 It is the activities of catalase, polyphenol oxidase and peroxidase in the reclaimed soil under different fertilization measures in the present invention; wherein, Fig.10 (1) is the catalase activity of reclaimed soil under different fertilization measures; Fig.10 (2) is the polyphenol oxidase activity in reclaimed soil under different fertilization measures; Fig.10 (3) in the figure is the peroxidase activity in reclaimed soil under different fertilization measures.

[0043] Fig.11 is the urease and protease activities of the reclaimed soil under different fertilization measures in the present invention; wherein, Fig.11 (1) is the urease activity of reclaimed soil under different fertilization measures; Fig.11 (2) in the figure is the protease activity in reclaimed soil under different fertilization measures.

[0044] Fig.12 It is the ecological multifunctionality of reclaimed soil under different fertilization measures in the present invention.

[0045] Fig.13 It is a redundancy analysis ranking diagram of soil enzyme activity, organic carbon mineralization and microbial residue carbon in the present invention; wherein, Fig.13 (1) is the redundancy analysis ordination diagram of soil enzyme activity, organic carbon mineralization and microbial residue carbon in the reclaimed soil of Gujiao experimental site; Fig.13 (2) is a redundancy analysis ranking diagram of soil enzyme activity, organic carbon mineralization and microbial residue carbon in the Xiangyuan experimental site. In the figure, the hollow arrow lines represent soil enzyme activity, and the solid arrow lines represent related indicators of soil organic carbon mineralization and microbial residue carbon content. BG, β-glucosidase activity; SA, sucrase activity; AA, amylase activity; CA, catalase activity; UA, urease activity; PA, protease activity; PPO, polyphenol oxidase activity; Perox, peroxidase activity; C a , active organic carbon pool content; C s , slow-release organic carbon pool content; C r , inert organic carbon pool content; K a , decomposition rate of active organic carbon pool; K s , decomposition rate of slow-release organic carbon pool; CO2-C, cumulative mineralization of soil organic carbon; CRR, cumulative mineralization rate of soil organic carbon; MNC, soil microbial residue carbon content; BNC, soil bacterial residue carbon content; FNC, soil fungal residue carbon content; MNC / SOC, contribution of soil microbial residue carbon to soil organic carbon. DETAILED DESCRIPTION

[0046] The present invention is described in detail below in conjunction with the accompanying drawings and specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources.

[0047] Example 1

[0048] 1. Overview of the test site

[0049] Gujiao Reclamation Experimental Site: The test site is located in the coal gangue discharge area of ​​Tunlan Mine, Gujiao City, Shanxi Province (37°53'15″N, 112°6'42″E). Gangue was discharged into natural gullies starting in 2002. After the coal mine gangue discharge was completed in 2012, soil was taken nearby near the gangue field for filling. After two years of natural recovery, it was reclaimed as farmland. The area has a warm temperate semi-arid continental monsoon climate with an average annual precipitation of 450 mm and an average annual temperature of 9.5°C. The test soil type is new soil, and the parent material is loess. The basic physical and chemical properties of the 0-20 cm soil layer at the beginning of the experiment (2012) are shown in Table 1, and the basic physical and chemical properties of the 0-20 cm soil layer 10 years after reclamation (2021) are shown in Table 2.

[0050] Xiangyuan Reclamation Experimental Site: The test site is located in Wuyang Coal Mine of Lu'an Group, Xiangyuan County, Changzhi City, Shanxi Province (36°28′11.95″N, 113°00′52.57″E). Coal mining has caused ground subsidence and serious decline in land productivity. In 2008, mixed push reclamation was adopted, using topsoil stripping, deep digging and shallow padding, and on-site leveling for reclamation. The area has a warm temperate semi-humid continental monsoon climate, with an average annual precipitation of 550 mm and an average annual temperature of 9.5°C. The test soil is calcareous brown soil. The basic physical and chemical properties of the 0-20 cm soil layer at the beginning of the test (2008) are shown in Table 1, and the basic physical and chemical properties of the 0-20 cm soil layer 10 years after reclamation (2017) are shown in Table 2.

[0051] Table 1 Basic physical and chemical properties of initial soil in the test site (0-20 cm)

[0052]

[0053]

[0054] Table 2 Basic physical and chemical properties of soil under different fertilization treatments after 10 years of reclamation (0-20 cm)

[0055]

[0056] Note: Lowercase letters (a, b, c, d) indicate significant differences (P<0.05) among different treatments in the same reclamation test plot; uppercase letters (A,

[0057] B, C, D) indicate that there were significant differences among different reclamation test plots under the same treatment (P<0.05).

[0058] 2. Experimental Design

[0059] Gujiao reclamation test site: The food crop planted in the test site is spring corn (Xianyu 335), which was sown in early April and harvested at the end of September. There are 4 treatments in the experiment, namely no fertilizer (CK), chemical fertilizer (NPK), organic fertilizer alone (M) and organic and inorganic fertilizer combination (MNPK). The chemical fertilizers used in the experiment are urea (containing N 46%), superphosphate (containing P2O512%) and potassium chloride (containing K2O50%), while the organic fertilizer is fully decomposed chicken manure, which contains 29.43% organic matter, and the contents of nitrogen, phosphorus and potassium are 0.84%, 0.54% and 1.56% respectively. Each treatment was repeated 3 times and arranged in random blocks. The area of ​​the plot is 5m×2.5m=12.5m 2 Specific fertilizer application rates are shown in Table 3. Among them, no fertilizer (CK) is comparative example 1, chemical fertilizer (NPK) is comparative example 2, organic fertilizer (M) is comparative example 3, and organic and inorganic fertilizers (MNPK) are combined for example 1.

[0060] Xiangyuan Reclamation Experimental Site: The experimental site planted spring corn (Dafeng No. 30), which was sown in early April and harvested at the end of September. The harvested corn stalks were crushed and turned over and returned to the field. The experiment set up 4 treatments, namely no fertilizer (CK), chemical fertilizer (NPK), organic fertilizer alone (M) and organic and inorganic fertilizer combination (MNPK). Chemical fertilizers used were urea (containing 46% N), superphosphate (containing P2O512%) and potassium chloride (containing K2O 60%). Organic fertilizer used was fully decomposed chicken manure, which contained 14.97% organic carbon, and 1.68%, 1.54% and 0.82% nitrogen, phosphorus and potassium respectively. Each treatment was repeated 3 times, and the arrangement was completely random. The area of ​​the plot was 10m×5m=50m 2 The specific fertilizer application amount is shown in Table 3. Among them, no fertilizer (CK) is comparative example 4, chemical fertilizer (NPK) is comparative example 5, organic fertilizer (M) is comparative example 6, and organic and inorganic fertilizers (MNPK) are combined for example 2.

[0061] Table 3 Fertilizer application rates for different fertilization treatments

[0062]

[0063] Note: The N application amount in the table refers to the application amount of nitrogen fertilizer, which is measured by the mass of N in the nitrogen fertilizer; the P2O application amount refers to the application amount of phosphate fertilizer, which is measured by the mass of P2O5 in the phosphate fertilizer; K2O refers to the application amount of potassium fertilizer, which is measured by the mass of K2O in the potassium fertilizer; the application amount of organic fertilizer is recorded by the weight of the fertilizer.

[0064] 1. Methods

[0065] 1. Sample collection and analysis

[0066] Before the spring corn harvest (Example 1 and Comparative Examples 1 to 3 set in the Gujiao test site on October 19, 2021; Example 2 and Comparative Examples 4 to 6 set in the Xiangyuan test site on September 28, 2017), a custom-made ring knife (10 cm high, 10 cm in diameter) was used to collect 0 to 20 cm of undisturbed soil in each test plot using a five-point sampling method, and the soil was mixed and placed in a prepared plastic box for storage to avoid squeezing during transportation. After the sample was brought back to the laboratory, the soil sample was carefully broken into small pieces according to the natural structure and gaps of the soil, and passed through an 8 mm sieve, and impurities such as root stubble and pebbles were removed during the process, and then air-dried in a cool place for standby use to obtain an air-dried soil sample.

[0067] 2. Measurement items and methods

[0068] 2.1 Determination and calculation of soil organic carbon mineralization characteristics and related indicators

[0069] The soil organic carbon content was determined by potassium dichromate-volumetric method, the total nitrogen content was determined by semi-micro Kelvin method, and the soil inert organic carbon was determined by HCl hydrolysis method.

[0070] The characteristics of soil organic carbon mineralization were determined by indoor constant temperature culture and alkali solution absorption method. The specific steps were as follows: 100 g of air-dried soil sample passed through a 2 mm sieve was evenly placed in a 500 mL mineralization bottle, and the soil moisture was adjusted to 70% of the maximum field water holding capacity with distilled water. 10 mL of 1 mol·L -1 NaOH solution absorbs CO2 (use small plastic bottles to store and hang in mineralization bottles). Mineralization bottles are sealed and incubated at a constant temperature of 25°C in the dark. Plastic bottles are replaced on days 1, 2, 3, 5, 7, 10, 14, 21, 28, 36, 51, 71, 101, 161, and 251, and the amount of NaOH consumed in the plastic bottles is measured (0.5 mol·L -1 HCl titration). The soil moisture content was controlled gravimetrically during the incubation process.

[0071] Among them, the calculation formula for the mineralization of soil organic carbon during the cultivation period is:

[0072] CO2–C=(V0-V i )×c×6 (1);

[0073] Where CO2–C is the mineralization amount of soil organic carbon during the incubation period, in mg kg -1 , V0 and V irepresents the volume of HCl consumed by the blank and soil samples in titrating the NaOH solution, in mL, and c is the concentration of HCl, 0.5 mol·L -1 , 6 is the equivalent of C, the unit of C is mg kg -1 .

[0074] Cumulative mineralization rate of soil organic carbon = cumulative mineralization amount of soil organic carbon ÷ soil organic carbon content × 100 (2);

[0075] In the formula, the unit of soil organic carbon cumulative mineralization rate is %, and the unit of soil organic carbon cumulative mineralization is g·kg -1 , the unit of soil organic carbon content is g·kg -1 .

[0076] The soil active carbon pool (Ca) and slow-release carbon pool (Cs) contents and their corresponding mineralization rates were fitted using a double pool index model, and the fitting equation was:

[0077] C t =C a (1-e -kat )+C s (1-e -kst ) (3);

[0078] In the formula, C t is the cumulative amount of CO2 released at time t, in mg kg -1 ; C a and k a Respectively represent the content of active organic carbon pool, the unit is mg kg -1 and its degradation rate (day -1 );C s and k s Respectively represent the content of slow-release organic carbon pool, unit is mg·kg -1 and its degradation rate (day -1 );C a and C s The sum represents the potential mineralizable organic carbon content in the soil.

[0079] 2.2 Determination and calculation of related indicators of microbial residue carbon and plant residue carbon

[0080] The soil amino sugar content was determined according to the gas chromatography method proposed by Zhang (Zhang X, Amelung W. Gas chromatographic determination of muramic acid, glucosamine, mannosamine, and galactosamine insoils[J]. Soil Biology and Biochemistry, 1996, 28(9): 1201-1206.) and Amelung (

[103] Meng X, Zhang X, Li Y, et al. Nitrogen fertilizer builds soil organic carbon under straw return mainly via microbial necromass formation[J]. Soil Biology and Biochemistry, 2024, 188: 109223.).

[0081] Glucosamine (GluN) and muramic acid (MurN) were selected as representatives from the detected amino sugars to estimate the accumulation of fungal and bacterial residual carbon. Assuming that MurN and GluN are present in bacterial cells at a ratio of 1:2, fungal residual carbon was determined by subtracting bacterial GluN from total GluN. The calculation method is as follows:

[0082] Fungal necromass C=(GluN-2×MurN×179.2g mol -1 ×9 (4);

[0083] In the above formula, the unit of fungal necromass C is mg g -1 The unit of soil and GluN is mmol·g - 1 The unit of soil MurN is mmol g -1 soil.

[0084] Bacterial necromass C=MurN×45 (5);

[0085] In the above formula, the unit of Bacterial necromass C is mg g -1 The unit of soil and MurN is mg g - 1 soil.

[0086] The molecular weight of glucosamine (GluN) is 179.2; the coefficient 2 is set based on the molar ratio of glucosamine to muramic acid in bacterial cells of 2:1. The conversion coefficient of glucosamine to fungal residual carbon content is 9, and the conversion coefficient of muramic acid to bacterial residual carbon content is 45. The sum of the fungal residual carbon content and the bacterial residual carbon content is the total microbial residual carbon content.

[0087] According to the carbon content of microbial residues, the contribution of soil microbial residue carbon to soil organic carbon is calculated:

[0088] Contribution of microbial residue carbon to soil organic carbon = total microbial residue carbon content / SOC content × 100 (6);

[0089] In the above formula, the unit of contribution of microbial residue carbon to soil organic carbon is %, and the unit of total microbial residue carbon content is g·kg -1 , the unit of SOC content is g·kg -1 .

[0090] 2.3 Methods for determining soil enzyme activity and calculating soil ecological multi-activity

[0091] The β-glucosidase activity was determined by nitrobenzene colorimetry (Wang X, Lu Q. Beta-glucosidase activity in paddy soils of the Taihu Lake region, China [J]. Pedosphere, 2006, 16 (1): 118-124.), the sucrase and amylase activities were determined by 3,5-dinitrosalicylic acid colorimetry (Guan Songyin. Soil enzymes and their research methods [M]. Beijing: Agricultural Press, 1986.), the catalase activity was determined by potassium permanganate titration (Guan Songyin. Soil enzymes and their research methods [M]. Beijing: Agricultural Press, 1986.), and the polyphenol oxidase and peroxidase activities were determined by microplate colorimetry (DeForest J L. The influence of time, storage temperature, and substrate age on potential soil enzyme activity in acidic forest soils using MUB-linked substrates and L-DOPA [J]. Soil Biology and Biochemistry, 2009, 41(6): 1180-1186.), urease activity was determined by sodium phenol-sodium hypochlorite colorimetric method (Guan Songyin. Soil enzymes and their research methods [M]. Beijing: Agricultural Press, 1986.), and protease activity was determined by ninhydrin colorimetric method (Guan Songyin. Soil enzymes and their research methods [M]. Beijing: Agricultural Press, 1986.).

[0092] The present invention uses seven kinds of soil enzyme activities (BG, SA, AA, CA, UA, PA, PPO and Perox) to characterize the multifunctionality of the soil ecosystem (Soil ecosystem multifunctionality, EMF) (Jia R, Zhou J, Chu J, et al. Insights into the associations between soil quality and ecosystem multifunctionality driven by fertilization management: A case study from the North China Plain [J]. Journal of Cleaner Production, 2022, 362: 132265.) ~ (Li Qisheng, Yang Kai, Wang Zhipeng, et al. Effect of organic substitution on soil extracellular enzyme activity and multifunctionality under rice-oil rotation [J]. Journal of Soil and Water Conservation, 2021, 35 (02): 345-352 + 360.). The average method is used to calculate EMF, specifically: first standardize the data of each enzyme activity index, and the formula is as follows:

[0093] Z-score=(X-mean i )÷SD i (7);

[0094] In the above formula, Z-score is the normalized value of the activity index of enzyme i, X is the measured enzyme activity, mean is the mean value of enzyme i, and SD is the standard deviation of enzyme i. EMF is the average value of the normalized values ​​of the seven soil enzyme activities.

[0095] 3. Data processing and statistical analysis

[0096] DPS statistical analysis software was used for one-way ANOVA. When the results of ANOVA were significant, the LSD method was used for multiple comparisons. SPSS25.0 software was used for regression analysis and double-library index model fitting. Canoco 5 software was used for redundancy analysis and RDA ordination diagram was drawn. Excel 2016 and Origin 2022 were used for data processing and drawing.

[0097] 2. Results

[0098] 1. Differences in stability of organic carbon pool in reclaimed soil under different fertilization

[0099] 1.1 Effects of different fertilizations on organic carbon and total nitrogen content in reclaimed soil

[0100] Depend on Figure 1It can be seen that the organic carbon and total nitrogen contents of the reclaimed soils in Gujiao and Xiangyuan were different under different long-term fertilization treatments. The organic carbon content of the soil in the Gujiao test site was generally higher than that in the Xiangyuan test site, especially in the treatment of applying organic fertilizer (M and MNPK), but the total nitrogen content of the soil in the Xiangyuan test site was generally higher than that in the Gujiao test site.

[0101] Compared with the CK treatment, the application of chemical fertilizer (NPK) significantly increased the organic carbon content of the reclaimed soil in Xiangyuan by 11.23%, but had no significant effect on the organic carbon content of the reclaimed soil in Gujiao. Both the M and MNPK treatments significantly increased the organic carbon content of the reclaimed soil in Gujiao and Xiangyuan, with increases of 42.57%-82.25% and 21.75%-45.61%, respectively, and the effect of the MNPK treatment was the most significant.

[0102] The change trend of soil total nitrogen content was similar to that of organic carbon. Compared with the CK treatment, the NPK treatment only significantly increased the total nitrogen content of the reclaimed soil in Xiangyuan, with an increase of 11.80%. Both the M and MNPK treatments significantly increased the total nitrogen content of the reclaimed soil in the two experimental plots, with increases of 34.98%-52.47% (Gujiao) and 51.12%-55.06% (Xiangyuan), respectively.

[0103] 1.2 Effects of different fertilizations on the mineralization rate of organic carbon in reclaimed soil

[0104] The mineralization rate of soil organic carbon in Xiangyuan test site was generally higher than that in Gujiao test site ( Figure 2 ), but the change trends of soil organic carbon mineralization rates in Gujiao and Xiangyuan test sites were basically the same, and both could be divided into three stages: the first stage was the initial stage of cultivation, which lasted for about 1d to 7d, and the soil organic carbon mineralization rate reached the maximum on the first day, which was 4.68mg kg -1 d -1 ~6.33mgkg -1 d -1 (Gujiao) and 5.73 mg kg -1 d -1 ~9.84mg kg -1 d -1(Xiangyuan), and then the mineralization rate dropped sharply. Compared with the first day, the mineralization rate on the 7th day decreased by 59.80%~67.29% (Gujiao) and 59.38%~64.46% (Xiangyuan). In this stage, soil organic carbon decomposed in a large amount in a short time, and the mineralization rate was high. It was a rapid mineralization stage of soil organic carbon; the second stage was the middle incubation period, that is, 8d~51d, and the soil organic carbon mineralization rate was still slowing down, but the change range was smaller than that in the first stage. Compared with the seventh day, the soil organic carbon mineralization rate on the 51st day decreased by 62.66%~64.27% (Gujiao) and 64.57%~67.83% (Xiangyuan). This stage was a stage of slow mineralization of soil organic carbon; the third stage was the late incubation period, that is, 51d~251d. This stage lasted the longest, the soil organic carbon mineralization rate changed the least, and basically tended to be stable. This stage is called the relatively stable stage of soil organic carbon decomposition. During the cultivation period, the mineralization rates of organic fertilizer treatments (M and MNPK) in Gujiao and Xiangyuan were higher than those in NPK and CK. The changes in the mineralization rates of organic carbon in each treatment in the two experimental sites with the cultivation time were in accordance with the logarithmic function relationship, and the correlations reached a significant level (Table 4).

[0105] Table 4 Regression equations for mineralization rate of organic carbon in reclaimed soil under different fertilization measures

[0106]

[0107] Note: ** indicates a significance level of P < 0.01.

[0108] 1.3 Effects of different fertilizations on the cumulative mineralization of organic carbon in reclaimed soils

[0109] With the extension of the cultivation time, the cumulative mineralization of the Gujiao and Xiangyuan test sites showed a gradual increase trend ( Figure 3 ). The cumulative mineralization of organic carbon in the reclaimed soil of the Xiangyuan test site was significantly higher than that of the Gujiao test site (except for the NPK treatment). The cumulative mineralization of organic carbon in the soil of the Gujiao test site was only 80.89% to 86.23% of that in the Xiangyuan test site. Compared with the CK treatment, the NPK treatment had no significant effect on the cumulative mineralization of organic carbon in the reclaimed soil of the two test sites. The application of organic fertilizers (M and MNPK treatments) significantly increased the cumulative mineralization of organic carbon in the reclaimed soil, with increases of 38.77% to 41.92% (Gujiao) and 46.14 to 47.92% (Xiangyuan), respectively.

[0110] In addition, by analyzing the cumulative mineralization rate of soil organic carbon, it was found that ( Figure 4), the cumulative mineralization rate of organic carbon in the reclaimed soil in the Xiangyuan test site was significantly higher than that in the Gujiao test site (except for the NPK treatment), and the effects of long-term fertilization on the cumulative mineralization rate of soil organic carbon in the two test sites were different. In the Gujiao test site, compared with the CK treatment, the NPK treatment significantly increased the cumulative mineralization rate of organic carbon in the reclaimed soil, with an increase of 22.45%, while the MNPK treatment significantly reduced the cumulative mineralization rate of organic carbon in the reclaimed soil, with a decrease of 21.84%; in the Xiangyuan test site, compared with the CK treatment, the NPK treatment significantly reduced the cumulative mineralization rate of organic carbon in the reclaimed soil, with a decrease of 16.00%, while the M treatment significantly increased the cumulative mineralization rate of organic carbon in the reclaimed soil, with an increase of 21.49%.

[0111] 1.4 Effects of different fertilizations on the organic carbon pool in reclaimed soil

[0112] The double-pool index model was used for curve fitting to simulate the kinetic characteristics of organic carbon mineralization in reclaimed soil (Table 5). The double-pool index model divides the potential mineralizable organic carbon into active organic carbon pool (C a ) and slow-release organic carbon pool (C s ), and estimated the corresponding mineralization rate constant K a and K s The R values ​​of each treatment in Gujiao and Xiangyuan test sites 2 The value range is 0.990~0.995, indicating that the dual-pool index model can well simulate the mineralization characteristics of the organic carbon pool in the reclaimed soil. At the same time, the inert organic carbon content measured by the acid hydrolysis method is used to characterize the soil inert organic carbon pool (C r ) changes.

[0113] In both experimental plots, C r The highest content (3972.20 mg kg -1 ~9927.43mg·kg -1 ), followed by C s (119.96mg·kg -1 ~173.18mg kg -1 ), Ca content was the lowest (6.52 mg kg -1 ~16.21mgkg -1 ). C of Xiangyuan test site under each treatment a The content of C in the Xiangyuan test site was significantly higher than that in the Gujiao test site, with an increase of 38.38% to 66.65%. s The contents of C r In terms of the content, under NPK treatment, the content of C in Xiangyuan test site was significantly higher than that in Gujiao test site, with an increase of 60.36%. However, under MNPK treatment, the content of C in Xiangyuan test site was significantly higher than that in Gujiao test site, with an increase of 60.36%. rThe content of active organic carbon pool in Xiangyuan test site under MNPK treatment was significantly lower than that in Gujiao test site, with a decrease of 18.26%. a / (C a +C s )) was significantly higher than that of Gujiao experimental site, with an increase of 46.77%.

[0114] The responses of organic carbon pools in the two experimental sites to different fertilization measures were slightly different (Table 5). a , C s and C r The content of C r The increase was the largest. In the Xiangyuan test site, compared with the CK treatment, the NPK treatment significantly reduced the s The content of C r The content of C a , C s and C r The content of C a The improvement was the largest, and K s and C a / (C a +C s ), with increases of 60.11% to 60.88% and 35.09% to 42.96% respectively.

[0115] Table 5 Carbon mineralization parameters of reclaimed soil under different fertilization measures

[0116]

[0117] Note: Lowercase letters (a, b, c, d) indicate significant differences (P<0.05) between different treatments in the same reclamation test plot; uppercase letters (A, B, C, D) indicate significant differences (P<0.05) between different reclamation test plots under the same treatment, the same below. a , active organic carbon pool; C s , slow-release organic carbon pool; C r , inert organic carbon pool; K a , decomposition rate of active organic carbon pool; K s , decomposition rate of slow-release organic carbon pool; C a +C sPotential mineralizable carbon pool; C a / (C a +C s ), the ratio of active organic carbon pool to potential mineralizable carbon pool.

[0118] 2. Effects of different fertilizations on reclaimed soil microorganisms, plant-derived carbon, and key enzyme activities of carbon cycle

[0119] 2.1 Effects of different fertilizations on the amino sugar content in reclaimed soil

[0120] By analyzing the contents of four amino sugars - mannose (ManN), galactose (GalN), glucosamine (GluN) and muramic acid (MurN) in the Gujiao and Xiangyuan reclamation test sites, it was found that ( Figure 5 ), the amino sugar content of soil in Xiangyuan test site was generally higher than that in Gujiao test site. In the two reclamation test sites, the GluN content was the highest in each treatment, which was 95.28 mg kg -1 ~208.62mg·kg -1 , accounting for 63.04% to 71.92% of the total amino sugar (TAS) content in the soil, followed by GalN, with a content range of 40.43 mg kg -1 ~73.41mg·kg -1 , accounting for 22.74% to 29.80% of the soil TAS content; all fertilization treatments had no significant effect on MurN content.

[0121] The influence trend of fertilization on the amino sugar content of soil in different experimental plots was inconsistent. In the Gujiao experimental plot, compared with the CK treatment, the NPK, M and MNPK treatments all significantly reduced the TAS and GalN contents of the reclaimed soil, with a decrease of 9.56% to 31.11% and 23.62% to 29.37%, respectively; the NPK and MNPK treatments also significantly reduced the GluN content of the reclaimed soil, with a decrease of 34.38% and 22.35%, respectively; in addition, the MNPK treatment also significantly increased the ManN content of the reclaimed soil, with an increase of 147.79%. In the Xiangyuan experimental plot, compared with the CK treatment, only the NPK and MNPK treatments significantly reduced the ManN content of the reclaimed soil, with a decrease of 52.28% and 44.20%, respectively; the M and MNPK treatments significantly increased the GluN content of the reclaimed soil, with an increase of 17.93% and 46.11%, respectively; and the MNPK treatment also significantly increased the TAS content of the reclaimed soil, with an increase of 30.71%.

[0122] 2.2 Effects of different fertilizations on carbon content of fungal and bacterial residues in reclaimed soil

[0123] Based on the specificity of glucosamine (GluN) and muramic acid (MurN) sources, the carbon content of fungal residues in reclaimed soil was estimated. It was found that under NPK and MNPK treatments, the carbon content of fungal residues in Xiangyuan test site was significantly higher than that in Gujiao test site, with an increase of 51.13% to 90.71% ( Figure 6 (1)). The carbon content of fungal residues in the two reclaimed test plots also responded differently to different fertilization treatments. Compared with the CK treatment, the NPK and MNPK treatments significantly reduced the carbon content of fungal residues in the reclaimed soil of the Gujiao test plot, with decreases of 35.49% and 24.80%, respectively. The M and MNPK treatments significantly increased the carbon content of fungal residues in the reclaimed soil of the Xiangyuan test plot, with increases of 20.01% and 52.96%, respectively.

[0124] Based on the specificity of muramic acid (MurN) sources, the carbon content of bacterial residues in reclaimed soil was estimated. Figure 6 In (2)), under each treatment, the carbon content of bacterial residues in the reclaimed soil of Xiangyuan test site was significantly higher than that of Gujiao test site (except MNPK treatment), with an increase of 20.82% to 125.07%. All fertilization treatments had no significant effect on the carbon content of bacterial residues in the reclaimed soil of Xiangyuan test site. However, the carbon content of bacterial residues in the reclaimed soil of Gujiao test site was significantly increased by MNPK treatment compared with CK treatment, with an increase of 22.83%.

[0125] In summary, MNPK treatment significantly reduced the carbon content of fungal residues in the reclaimed soil of Gujiao experimental site, while significantly increased the carbon content of bacterial residues in the reclaimed soil of Gujiao experimental site and the carbon content of fungal residues in the reclaimed soil of Xiangyuan experimental site.

[0126] .2.3 Effects of different fertilizations on the carbon content of microbial residues in reclaimed soil

[0127] The carbon content of microbial residues in the reclaimed soil of the Xiangyuan test site was generally higher than that of the Gujiao test site, especially in the NPK and MNPK treatments ( Figure 7 (1)). In each treatment of the two experimental sites, the carbon content of fungal residues was higher than that of bacterial residues, and it was the main component of microbial residue carbon in reclaimed soils, accounting for 76.45% to 84.07% (Gujiao) and 72.63% to 83.62% (Xiangyuan) of the total microbial residue carbon content. Figure 7 (2) in the figure.

[0128] Fertilization had different effects on the carbon content of soil microbial residues in the two reclaimed test plots. Compared with the CK treatment, the NPK and MNPK treatments significantly reduced the carbon content of soil microbial residues in the Gujiao test plot, with a decrease of 32.05% and 17.21%, respectively. The organic fertilizer treatments (M and MNPK) significantly increased the carbon content of soil microbial residues in the Xiangyuan test plot, with increases of 14.13% and 33.57%, respectively.

[0129] In conclusion, MNPK treatment significantly reduced the carbon content of microbial residues in the reclaimed soil of Gujiao experimental site, but significantly increased the carbon content of microbial residues in the reclaimed soil of Xiangyuan experimental site.

[0130] 2.4 Contribution of microbial residue carbon to reclaimed soil organic carbon under different fertilization conditions

[0131] By analyzing the contribution of microbial residue carbon in reclaimed soil to SOC, it was found that ( Figure 8 ), the contribution of microbial residue carbon in the reclaimed soil of Gujiao experimental site to SOC was 10.30%-22.63%, and the contribution of microbial residue carbon in the reclaimed soil of Xiangyuan experimental site to SOC was 23.18%-25.27%. Under the fertilization treatment (NPK, M and MNPK), the contribution of microbial residue carbon in the reclaimed soil of Xiangyuan experimental site to SOC was significantly higher than that of Gujiao experimental site, with an increase of 39.22%, 54.98% and 125.05% respectively, while fertilization did not affect the contribution of microbial residue carbon in the reclaimed soil of Xiangyuan experimental site to SOC.

[0132] Fertilization significantly affected the contribution of microbial residue carbon to SOC in the reclaimed soil of the Gujiao experimental site. Compared with the CK treatment, the NPK, M and MNPK treatments all significantly reduced the contribution of microbial residue carbon to SOC in the reclaimed soil, with decreases of 24.64%, 32.43% and 54.49% respectively.

[0133] 2.5 Effects of different fertilizations on the activities of key hydrolytic enzymes in the carbon cycle of reclaimed soils

[0134] β-Glucosidase, amylase and sucrase are key hydrolytic enzymes affecting soil carbon cycle. Long-term fertilization significantly affected the activities of β-glucosidase, amylase and sucrase in reclaimed soil ( Fig. 9 (1)). The activities of β-glucosidase and amylase in Gujiao were significantly lower than those in Xiangyuan, with decreases of 99.04% to 198.16% and 152.52% to 245.96%, respectively. However, the activity of sucrase was significantly higher than that in Xiangyuan, with an increase of 64.04% to 65.94%. Compared with the CK treatment, the NPK, M and MNPK treatments all significantly increased the activities of soil β-glucosidase, amylase and sucrase in the Xiangyuan test site, with increases of 32.70%-97.44%, 97.14%-195.76% and 14.98%-58.95%, respectively, with the MNPK treatment having the largest increase. In the Gujiao test site, the NPK treatment significantly increased the amylase activity by 52.42%, the M treatment significantly increased the β-glucosidase and sucrase activities by 86.76% and 70.17%, respectively, and the MNPK treatment significantly increased the amylase and sucrase activities by 139.77% and 79.03%, respectively.

[0135] 2.6 Effects of different fertilizations on the activities of key oxidoreductases in the carbon cycle of reclaimed soils

[0136] Catalase, polyphenol oxidase and peroxidase are key oxidoreductases in soil carbon cycle. Long-term fertilization also significantly affected the activities of catalase, polyphenol oxidase and peroxidase in reclaimed soil ( Fig.10 (1)). The activities of catalase, polyphenol oxidase and peroxidase in Gujiao test site were significantly lower than those in Xiangyuan test site, with decreases of 3795.38% to 4722.08%, 245.32% to 757.24% and 132.03% to 670.92% respectively.

[0137] Compared with CK treatment, in Gujiao test site, NPK and M treatments significantly reduced polyphenol oxidase and peroxidase activities, with a decrease of 46.15% to 48.38% and 39.56% to 49.12%, respectively. MNPK treatment significantly increased catalase activity, with an increase of 11.54%, but significantly reduced polyphenol oxidase and peroxidase activities, with a decrease of 76.64% and 64.28%, respectively. In Xiangyuan test site, NPK treatment significantly reduced catalase activity, with a decrease of 8.54%, M treatment significantly reduced catalase activity, with a decrease of 6.38%, but significantly increased peroxidase activity, with an increase of 15.54%, MNPK treatment significantly reduced catalase activity, with a decrease of 9.90%, but significantly increased peroxidase activity, with an increase of 18.69%.

[0138] 2.7 Effects of different fertilizations on the activities of key enzymes in the nitrogen cycle of reclaimed soil

[0139] Soil urease and protease are related to soil nitrogen cycle. The activities of soil urease and protease in Gujiao test site were significantly higher than those in Xiangyuan test site, with increases of 69.19% to 76.41% and 75.65% to 80.35% ( Fig.11 ). In the Gujiao test site, compared with the CK treatment, the M and MNPK treatments significantly increased the urease activity by 59.26% and 78.49%, respectively. The MNPK treatment also significantly increased the protease activity by 206.09%. In the Xiangyuan test site, the NPK treatment significantly increased the urease activity by 19.46%, and the M and MNPK treatments significantly increased the urease and protease activities by 32.93% to 36.63% and 60.00% to 192.00%, respectively.

[0140] 2.8 Effects of different fertilizations on ecological multifunctionality of reclaimed soil

[0141] Under each fertilization treatment, the soil ecological multifunctionality of Xiangyuan test site was generally higher than that of Gujiao test site ( Fig.12). Long-term fertilization improved the ecological multifunctionality of reclaimed soil. Compared with the CK treatment, the application of organic fertilizers (M and MNPK) significantly improved the ecological multifunctionality of soil in the Gujiao test site, with increases of 119.56% and 244.99%, respectively; NPK, M and MNPK treatments all significantly improved the ecological multifunctionality of soil in the Xiangyuan test site, with increases of 67.79%, 131.85% and 200.35%, respectively. In both test sites, the MNPK treatment had the most significant effect on improving soil ecological multifunctionality.

[0142] 2.9 Relationship between soil enzyme activity and soil organic carbon mineralization and microbial residue carbon accumulation in reclaimed soil

[0143] In the redundancy analysis diagram of Gujiao test site ( Fig.13 In (1)), the first axis explains 47.83% of the change in organic carbon mineralization and microbial residue carbon, and the second axis explains 26.59%. That is, the first two axes cumulatively explain 74.42% of the change in organic carbon mineralization and microbial residue carbon, indicating that the first two axes can better reflect the relationship between the enzyme activity of reclaimed soil and the mineralization of organic carbon and the accumulation of microbial residue carbon. As shown in Table 6, urease, polyphenol oxidase and protease are the main enzymes affecting the organic carbon transformation in the Gujiao test site (P<0.05), and their contribution rates are 47.70%, 25.80% and 8.90%, respectively. Among them, urease activity is significantly correlated with the content of active organic carbon pool (C a ), slow-release organic carbon pool content (C s ), inert organic carbon pool content (C r ), decomposition rate of slow-release organic carbon pool (K s ), soil organic carbon accumulation mineralization (CO2-C) and bacterial residual carbon content (BNC) were positively correlated.

[0144] In the redundancy analysis diagram of Xiangyuan test site ( Fig.13 In (2)), the first axis explains 61.93% of the changes in soil organic carbon mineralization and microbial residue carbon, and the second axis explains 10.55%. That is, the first two axes cumulatively explain 72.48% of the changes in soil organic carbon mineralization and microbial residue carbon, indicating that the first two axes can better reflect the relationship between the enzyme activity of reclaimed soil and organic carbon mineralization and microbial residue carbon accumulation. As shown in Table 6, sucrase and β-glucosidase are the main enzymes affecting the transformation of soil organic carbon in the Xiangyuan test site (P<0.05), with contribution rates of 65.70% and 10.80%, respectively. Among them, sucrase activity is significantly correlated with the content of active organic carbon pool (C a ), slow-release organic carbon pool content (C s ), inert organic carbon pool content (C r ), decomposition rate of slow-release organic carbon pool (K s), soil organic carbon cumulative mineralization (CO2-C), soil organic carbon cumulative mineralization rate (CRR), fungal residue carbon content (FNC) and microbial residue carbon content (MNC) were positively correlated.

[0145] Table 6 Explanation rate of soil enzyme activity for organic carbon mineralization and microbial residue carbon changes in RDA analysis

[0146]

[0147]

[0148] In summary, the method for improving the stability of the organic carbon pool in the reclaimed soil of a mining area provided by the present invention significantly improves the organic carbon content of the reclaimed soil, and does not increase the cumulative mineralization rate of soil organic carbon, which is an effective measure to improve the stability of the organic carbon pool in the reclaimed soil. In addition, the method promotes the accumulation of fungal residue carbon and the increase of M-cPOC content by increasing the activity of sucrase, thereby increasing the organic carbon sequestration in the reclaimed soil of the mining area. At the same time, the method promotes the accumulation of bacterial residue carbon and the increase of the content of unprotected fine particulate organic carbon (M-fPOC) in large aggregates by increasing the activity of soil urease, thereby increasing the organic carbon sequestration in the reclaimed soil of the mining area.

[0149] It should be noted that when the claims of the present invention involve numerical ranges, it should be understood that the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. In order to avoid redundancy, the present invention describes a preferred embodiment.

[0150] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0151] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for improving the stability of organic carbon pool in reclaimed soil in mining areas, characterized in that: The steps include: Reclamation treatment: Planting food crops in the reclaimed soil of the mining area from the end of April to the beginning of May each year, and applying fertilizers before planting the food crops; harvesting the food crops after they mature; removing the fruits of the harvested food crops, crushing them, and then turning them over and pressing them into the reclaimed soil of the mining area; At the end of April or early May of the second year, the above reclamation treatment is repeated, and the repetition cycle is 9 to 11 years; The fertilization method is: mixing organic fertilizer and inorganic fertilizer and applying them to the reclaimed soil in the mining area around the food crops; the mass ratio of the organic fertilizer to the inorganic fertilizer is 24-42:1; The inorganic fertilizer includes nitrogen fertilizer, phosphate fertilizer and potash fertilizer; the mass ratio of N in the nitrogen fertilizer is 42% to 50%, the mass ratio of P2O5 in the phosphate fertilizer is 10% to 14%, and the mass ratio of K2O in the potash fertilizer is 40% to 70%; the application amount of the nitrogen fertilizer is 90kg·hm -2 ~105kg·hm -2 , is based on the mass of N in nitrogen fertilizer; the application rate of phosphate fertilizer is 40kg·hm -2 ~98kg·hm -2 , is based on the mass of P2O5 in the phosphate fertilizer; the application rate of the potash fertilizer is 45kg·hm -2 ~105kg·hm -2 , is based on the mass of K2O in potash fertilizer; The application amount of the organic fertilizer is 5000kg·hm -2 ~13000kg·hm -2 ; The organic matter content of the organic fertilizer is 14.97% to 17.07%, and the nitrogen, phosphorus and potassium contents of the organic fertilizer are 0.84% ​​to 1.68%, 0.54% to 1.54% and 0.82% to 1.56% respectively; Before and after reclamation, the organic carbon content in the reclaimed soil of the mining area increased from 4.09 g·kg -1 ~4.20g·kg -1 Increased to 9.10 g kg -1 ~12.74g·kg -1 .

2. A method for improving the stability of the organic carbon pool in the reclaimed soil of a mining area according to claim 1, characterized in that: The nitrogen fertilizer application rate is 95 kg·hm -2 ~100.8kg·hm -2 The application amount of the phosphate fertilizer is 45 kg·hm -2 ~92.4kg·hm -2 The application amount of potash fertilizer is 49.2 kg·hm -2 ~100kg·hm -2 ; The application amount of the organic fertilizer is 6000kg·hm -2 ~12000kg·hm -2 .

3. A method for improving the stability of the organic carbon pool in the reclaimed soil of a mining area according to claim 1, characterized in that: The nitrogen fertilizer includes any one or more of urea, ammonium sulfate, ammonium bicarbonate, diammonium phosphate potassium nitrate and calcium nitrate.

4. A method for improving the stability of the organic carbon pool in the reclaimed soil of a mining area according to claim 3, characterized in that: The nitrogen fertilizer is urea, and the mass ratio of N in the urea is 45% to 47%.

5. The method for improving the stability of the organic carbon pool in the reclaimed soil of a mining area according to claim 1, characterized in that: The phosphate fertilizer includes any one or more of superphosphate, double superphosphate, enriched superphosphate and diammonium phosphate.

6. A method for improving the stability of the organic carbon pool in the reclaimed soil of a mining area according to claim 5, characterized in that: The phosphate fertilizer is superphosphate, and the mass ratio of P2O5 contained in the superphosphate is 11% to 13%.

7. A method for improving the stability of the organic carbon pool in the reclaimed soil of a mining area according to claim 1, characterized in that: The potash fertilizer includes any one or more of potassium chloride, potassium sulfate, potassium nitrate and potassium dihydrogen phosphate.

8. A method for improving the stability of the organic carbon pool in the reclaimed soil of a mining area according to claim 7, characterized in that: The potash fertilizer is potassium chloride, and the mass ratio of K2O in the potassium chloride is 59% to 61%.

9. The method for improving the stability of the organic carbon pool in the reclaimed soil of a mining area according to claim 1, characterized in that: The organic fertilizer is completely decomposed chicken manure.

10. The method for improving the stability of the organic carbon pool in the reclaimed soil of a mining area according to claim 1, characterized in that: The food crops include spring corn or soybeans.

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