Method for promoting accumulation of organic matter based on soil food web level and application thereof

Abstract

The application discloses a method for promoting organic matter accumulation based on a soil food web level and application thereof, and belongs to the technical field of soil ecological restoration and organic matter management. It is found for the first time that by simultaneously supplementing crushed crop straw, predatory nematodes and bacterivorous nematodes into soil, the release of the easily-decomposable carbon pool can be significantly accelerated, the decomposition rate of organic matter can be improved, the accumulation of mineral-associated organic matter (MAOC) can be promoted, and the long-term fixation of soil organic matter is beneficial; the method for promoting the accumulation of soil organic matter is simple in operation, high in environmental compatibility, suitable for various soil types, and has a wide application prospect, can effectively improve soil quality, improve soil productivity and cultivation environment, and promote sustainable development of agriculture.

Description

Technical Field

[0001] This invention relates to the field of soil improvement and sustainable agricultural development technology, and in particular to a method for promoting organic matter accumulation based on the soil food web level and its application. Background Technology

[0002] Soil organic matter, broadly speaking, refers to all carbon-containing organic matter existing in soil in various forms, including various animal and plant residues, microorganisms, and the various organic matter they decompose and synthesize. It is a core component of soil, playing a vital role in maintaining soil fertility, improving soil structure, promoting plant growth, and regulating the global carbon cycle. Increasing soil organic matter content is one of the core goals of sustainable agricultural development. However, due to long-term unhealthy farming practices and factors such as climate change, soil organic matter content has generally declined globally, leading to problems such as soil degradation, decreased productivity, and environmental deterioration.

[0003] Traditional soil organic matter management methods (such as applying organic fertilizers, returning straw to the field, and planting green manure) can increase the input of soil organic matter, but the conversion efficiency of organic matter is limited by factors such as the activity of soil microorganisms, soil texture, and climatic conditions. Furthermore, traditional methods often require large quantities of organic materials, leading to resource constraints and high transportation costs. Scientific evaluation of soil organic matter dynamics requires multi-dimensional indicators: by measuring dissolved organic carbon (DOC), particulate organic carbon (POC), mineral-bound organic carbon (MAOC), and total soil organic carbon (SOC), the stability and retention capacity of organic matter can be systematically analyzed, providing a precise basis for management strategies.

[0004] In recent years, the role of the soil food web in soil organic matter transformation has received increasing attention. The soil food web is a complex network composed of various soil organisms, including bacteria, fungi, protozoa, nematodes, and arthropods. These organisms interact through predation, decomposition, and symbiosis, influencing the decomposition, transformation, and stability of soil organic matter.

[0005] Therefore, regulating soil food web structure, optimizing soil carbon cycling pathways, and enhancing soil carbon sequestration capacity represent a promising new approach to increasing soil organic matter content. However, current research on how to utilize soil food webs to promote soil organic matter accumulation is relatively lacking, especially effective methods based on specific food web structures. Summary of the Invention

[0006] The purpose of this invention is to provide a method and its application for promoting organic matter accumulation based on the soil food web level, in order to solve the problems of low conversion efficiency, resource constraints and high costs of traditional soil organic matter management methods, and to provide evidence to support the exploration of using the soil food web to increase soil organic matter content.

[0007] To achieve the above objectives, the present invention provides a method for promoting organic matter accumulation based on the soil food web level by adding organic matter and nematodes to cultivated soil.

[0008] Preferably, the organic matter is crop straw; the crop straw is chopped to 1-2 cm and then mixed into the soil.

[0009] Preferably, the inoculation amount of the nematodes is 10-20 nematodes / g soil.

[0010] Preferably, the nematodes are omnivorous nematodes and bacterivorous nematodes; the inoculation ratio of omnivorous nematodes to bacterivorous nematodes is 1:1.

[0011] Preferably, the omnivorous nematode is a nematode of the genus *Rhizophora*. P. quartusdecimus .

[0012] Preferably, the bacteriophage nematode is a nematode of the family Pleuronectiidae. D. veechi Nematodes of the genus *Pelvichorus* Panagrolaimus sp.

[0013] Preferably, the nematode of the family Brachiidae D. veechi : Pelvic pharynx nematodes Panagrolaimus The ratio of entries added for sp. is 1:1.

[0014] Application of a method for promoting organic matter accumulation based on the soil food web level, as described above, in degraded soil remediation or farmland carbon sequestration.

[0015] Therefore, the present invention provides a method for promoting organic matter accumulation based on the soil food web level and its application, the specific technical effects of which are as follows:

[0016] (1) This invention is the first to discover that by simultaneously supplementing the soil with crushed crop straw, omnivorous nematodes and bacteriophageal nematodes, the release of easily decomposable carbon pools in the soil can be significantly accelerated, the decomposition rate of organic matter can be increased, and the accumulation of mineral-bound organic matter (MAOC) can be promoted, which is conducive to the long-term retention of soil organic matter.

[0017] (2) The method for promoting soil organic matter accumulation provided by the present invention is simple to operate, has strong environmental compatibility, is applicable to a variety of soil types, has broad application prospects, can effectively improve soil quality, improve soil productivity and farming environment, and promote sustainable agricultural development. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a statistical result of the physicochemical properties of the soil in each treatment on day 60 of greenhouse cultivation in Example 1 of the present invention; where a is the statistical result of the organic carbon content of the soil in each treatment; b is the statistical result of the soluble organic carbon content of the soil in each treatment; c is the statistical result of the particulate organic carbon content of the soil in each treatment; d is the statistical result of the mineral-bound organic carbon content of the soil in each treatment; asterisks ( The sign represents the significance level, i.e. P The range of values, express P <0.05; express P <0.01; express P <0.001; express P <0.0001;

[0020] Figure 2 This is the statistical result of the ratio of soil mineral-bound organic carbon to soil particulate organic carbon in each treatment on day 60 of greenhouse cultivation in Example 1 of this invention; where asterisks ( The sign represents the significance level, i.e. P The range of values, express P <0.05; express P <0.001;

[0021] Figure 3 This is a statistical result of the relative abundance values ​​of carbon isotopes for each treatment on day 60 of greenhouse cultivation in Example 1 of this invention; where asterisks ( The sign represents the significance level, i.e. P The range of values, express P <0.05; express P <0.01; express P <0.001. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] To make the objectives, technical solutions, and advantages of this application clearer, more thorough, and more complete, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. The following detailed descriptions are all illustrations of embodiments, intended to provide further detailed explanation of the present invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0024] All instruments, equipment, and reagents used in the examples were obtained commercially; all methods and steps not described in detail are conventional techniques in the field; all nematodes used in the examples were isolated, identified, and propagated by the inventors themselves, and the methods are described in Xie Wangliang's 2024 Master's thesis at Nanjing Agricultural University, entitled "Study on the Main Controlling Factors of Soil Bacterial Traits Affecting Nematode Body Size".

[0025] The culture media used in these examples are all conventional biological culture media, and their component information is as follows:

[0026] LB liquid culture medium: 10g trypsin powder, 5g yeast powder, 10g sodium chloride, 1L deionized water, autoclaved at 121°C for 20min;

[0027] NA liquid culture medium: 10g glucose, 3g beef extract, 5g peptone, 0.5g yeast powder, 1L deionized water, autoclaved at 115°C for 30min.

[0028] NGM solid medium: 2.5g peptone, 3.0g sodium chloride, 17.0g agar, 1L deionized water. Autoclave at 121°C for 20min. When the temperature drops to 65°C, add 25mL K3PO4 buffer (3.56g K2HPO4, 10.83g KH2PO4, 100mL deionized water), 1mL magnesium sulfate (1mol / L) solution, 1mL calcium chloride (1mol / L) solution, and 1mL cholesterol ethanol (5mg / mL) solution. Mix well and pour into a 60mm petri dish.

[0029] Example 1

[0030] A method for promoting organic matter accumulation based on the soil food web level, comprising the following steps:

[0031] S1. Nematode indoor culture and inoculation, the specific steps are as follows:

[0032] A: E. coli Escherichia coliOP50 was inoculated into LB liquid medium and cultured in a shaker at 200 rpm and 37°C until the logarithmic growth phase. 100 μL of Escherichia coli OP50 culture in the logarithmic growth phase was evenly spread on the surface of NGM solid medium and incubated at 37°C until colonies formed.

[0033] B: Separately, the nematodes of the genus *Rhizophora* (… P. quartusdecimus ), small stalk family ( D.veechi Nematodes and pelvic pharynx ( Panagrolaimus (sp.) Nematodes were inoculated into the colonies that grew in A, and cultured at 37°C. On the 6th day of culture, nematodes of the genus *Rhizophora* were surgically removed using a scalpel. P. quartusdecimus ), small stalk family ( D.veechi Nematodes and pelvic pharynx ( Panagrolaimus (sp.) The culture medium of nematodes was cut into pieces approximately 5cm in size. 2 Small pieces, with the back side down, are inoculated into the colonies that grow in A. Repeat this process every 5 days, cutting approximately 5cm pieces. 2 The step of inoculating small pieces into the colonies that grow in A will yield a large number of nematodes after 15 days.

[0034] C: Rinse the nematodes from step B into a 50mL centrifuge tube, wash with water 3 times, and prepare a nematode suspension with water.

[0035] S2. Soil samples were randomly collected from the topsoil (surface and within 30cm below) of cornfields in Lishu County, Siping City, Jilin Province, China. The surface covering was removed during sampling. The collected soil was passed through a 6mm sieve, and visible stones, crop roots, and straw were removed with tweezers. The soil was then mixed evenly and divided into two portions. One portion of unsterilized natural soil was randomly selected, and the other portion of soil was sterilized by high-pressure steam at 128°C for 2 hours 3-4 times, with an interval of 1-2 days between each sterilization, to obtain sterilized soil.

[0036] S3. The preparation method of soil bacterial suspension is as follows:

[0037] A: Take 20g of fresh natural soil and mix it with 100mL of sterile water. Shake it in a shaker at 200r / min and 30°C for 2 hours, then remove it and let it stand for 1 hour to obtain the soil supernatant.

[0038] B: Centrifuge the soil supernatant in a 450g centrifuge for 15 minutes and retain the supernatant after centrifugation.

[0039] C: The supernatant after centrifugation is filtered through a 1-micron filter membrane (PTFE membrane) to remove soil animals (such as nematodes and protozoa) but retain soil microorganisms, thus obtaining a soil microbial suspension.

[0040] S4, Preparation13 C stable isotope labeled corn stalks. 13 The C stable isotope-labeled corn stalks were provided by Thermotech (Shanghai) Co., Ltd. 13 The C abundance was 4.69%. 13 C60-stable isotope-labeled corn stalks were uniformly chopped to 1-2 cm and sterilized at 121°C for 20 min. The application rate of straw in the field was determined based on the following: (100% straw addition was 7500 kg·hm²). -2 That is, 0.075 g·cm -2 This is converted to the amount of straw required for the cultivation experiment, i.e., 0.18g should be added to each treatment. 13 C stable isotope labeling of straw.

[0041] S5. Set up 4 treatments, each repeated 6 times. The pot diameter is 7cm and the height is 9cm. Fill with 100g of sterilized soil and add according to step S4. 13 C stable isotope labeled straw, mixed evenly. Soil bacterial suspension and nematodes were added by irrigation method, that is, the soil bacterial suspension obtained in step S3C was inoculated into the soil sterilized in S2 at a ratio of 20 mL of soil bacterial suspension per 100 g soil, and then the nematode suspension from step S1C was inoculated into the corresponding treatment of sterilized soil in S2 at a ratio of 15 nematodes / g soil, *P. rascuari* nematodes. quartusdecimus ): Small-stemmed family (D.) veechi Nematodes: *Pelvicopharynx* ( Panagrolaimus The ratio of nematode numbers (sp.) was 1:0.5:0.5. Regular management continued until the nematodes were fully adapted to the soil environment.

[0042] CK group: Soil bacterial suspension (20 mL) was inoculated into the mixed soil using a watering method. 13 In sterilized soil containing C stable isotope-labeled straw, regular watering is carried out to maintain the soil moisture content at 60% of field capacity for soil management.

[0043] Group N1: Soil bacterial suspension (20 mL) was inoculated into the mixed soil using a watering method. 13 In sterilized soil containing C stable isotope-labeled straw, edible bacteria of the family Micrococcus (D) will be present. veechi Nematodes and pelvic pharynx ( Panagrolaimus (sp.) Nematodes were inoculated into the soil one week after planting using soil bacterial suspension at a ratio of 15 nematodes / g of soil (750 nematodes of each species, for a total of 1500 nematodes). The soil was then regularly watered to maintain the soil moisture content at 60% of field capacity.

[0044] Group N2: Soil bacterial suspension (20 mL) was inoculated into the mixed soil using a watering method. 13In sterilized soil containing C stable isotope-labeled straw, the genus *Pteranodon* (a type of omnivorous argan) will be present. P. quartusdecimus Nematodes, Bacteriophages ( D. veechi Nematodes and pelvic pharynx ( Panagrolaimus (sp.) Nematodes were inoculated into the soil at a ratio of 15 nematodes / g soil (750 nematodes of the genus *Pteris*, 375 nematodes of each of the other two nematode species, for a total of 1500 nematodes). The soil was then regularly watered to maintain the soil moisture content at 60% of field capacity. Soil management was carried out.

[0045] All treatments were placed in a greenhouse (25°C, 60% humidity) (day 1 of the experiment was recorded). On day 60 of the experiment, destructive sampling was performed. After removing all straw from the soil of each treatment using tweezers, the physicochemical properties and relative abundance values ​​of carbon isotopes of the soil samples were determined, including:

[0046] ① Soil organic carbon (SOC): The total organic carbon content of the soil was determined using an elemental analyzer, and its content was further determined using an isotope ratio mass spectrometer (IRMS). 13 C isotope relative abundance (δ) 13 C).

[0047] ② Soil soluble organic carbon (DOC): The soluble organic carbon content was determined using the water extraction-TOC analysis method, and the extract was analyzed using IRMS. 13 C isotope relative abundance (δ) 13 C).

[0048] ③ Soil particulate organic carbon (POC): determined by potassium permanganate oxidation method, and the extract was analyzed by IRMS. 13 C isotope relative abundance (δ) 13 C).

[0049] ④ Mineral-bound organic carbon (MAOC) in soil: MAOC was separated using a density separation-chemical oxidation method, then the MAOC carbon content was determined using an elemental analyzer, and its concentration was determined using IRMS. 13 C isotope relative abundance (δ) 13 C).

[0050] The ratio of the relative abundance of soil mineral-bound organic carbon to the relative abundance of soil particulate organic carbon (MAOC / POC) is a key indicator for measuring carbon stability and can effectively characterize the distribution pattern and stabilization efficiency of exogenous new carbon (straw) in different soil carbon pools.

[0051] The results of soil organic carbon (SOC) measurement are as follows: Figure 1 As shown in part a, compared to the blank control group (CK), inoculation with bacteria of the family Microcephala ( D. veechi Nematodes and pelvic pharynx ( Panagrolaimussp.) nematodes (N1) and inoculated omnivorous raspberries ( P. quartusdecimus Nematodes, Bacteriophages ( D.veechi Nematodes and the genus *Pelvicopharynx* Panagrolaimus The soil organic matter content of the sp. nematode (N2) is relatively high.

[0052] The results of the determination of water-soluble organic carbon (DOC) and particulate organic carbon (POC) are as follows: Figure 1 As shown in sections b and c, the DOC and POC contents of N1 and N2 in the nematode-inoculated groups were lower than those in the blank control group (CK), and the contents of N1 and N2 inoculated with nematodes were also lower than those in the control group (CK). P.quartusdecimus Nematodes, Bacteriophages ( D.veechi Nematodes and the genus *Pelvicopharynx* Panagrolaimus The DOC and POC contents of sp. nematodes (N2) were significantly the lowest. The presence of nematodes reduced the contents of water-soluble organic carbon and particulate organic carbon in the soil active carbon pool, indicating that nematodes promoted the degradation and turnover of the soil active carbon pool.

[0053] The results of the determination of mineral-bound organic carbon (MAOC) are as follows: Figure 1 As shown in section d, the MAOC content of N1 and N2 in the nematode-inoculated group was significantly higher than that in the blank control group (CK), and the content of MAOC in the nematode-inoculated group was significantly higher than that in the control group (CK). P. quartusdecimus Nematodes, Bacteriophages ( D. veechi Nematodes and the genus *Pelvicopharynx* Panagrolaimus The MAOC content was significantly highest in nematodes (N2) sp. . MAOC is key to stabilizing the carbon pool, and the presence of nematodes significantly increased the content of mineral-bound organic carbon in the soil stable carbon pool, indicating that nematodes promote the accumulation of soil stable carbon pool.

[0054] The results of soil organic carbon transformation pathways in soil are as follows: Figure 2 and Figure 3 As shown, the MAOC / POC and δ of N1 and N2 in the nematode-inoculated groups are... 13 C MAOC / POC were significantly higher than those in the blank control group (CK), and the inoculation with *C. fasciatus* (*C. fasciatus*) was also significantly higher. P. quartusdecimus Nematodes, Bacteriophages ( D. veechi Nematodes and the genus *Pelvicopharynx* Panagrolaimus sp.) MAOC / POC and δ 13 C MAOC / POC was significantly higher. This indicates that exogenous organic matter ( 13 C-labeled straw is being efficiently assimilated and transformed by soil organisms, and is adsorbed onto mineral surfaces in the form of residues (such as dead bacteria) to form stable MAOCs. N2 most effectively pumps straw carbon into stable carbon pools (MAOCs), which is a positive flow process from active pools to stable pools.

[0055] The results showed that under the influence of nematodes, the decomposition rate of soil organic matter accelerated, the pools of readily decomposable carbon and active carbon gradually decreased, while the accumulation of mineral-bound organic matter increased. Isotope tracing results further indicated that nematode activity promoted... 13 The conversion of carbon from straw (C-labeled) to MAOC directly demonstrates that the method provided by this invention can efficiently convert exogenous active organic carbon (straw) into stable mineral-bound organic carbon, greatly improving the sequestration efficiency and stability of exogenous carbon, and providing a precise and efficient means of regulation for achieving agricultural carbon sequestration and enhancement.

[0056] Therefore, this invention is the first to discover that simultaneously supplementing the soil with crushed crop straw, omnivorous nematodes, and bacteriophageal nematodes can significantly accelerate the release of readily decomposable carbon pools and increase the decomposition rate of organic matter; promote the accumulation of mineral-bound organic matter (MAOC), which is beneficial for the long-term retention of soil organic matter; the provided method for promoting soil organic matter accumulation is simple to operate, has strong environmental compatibility, is applicable to various soil types, has broad application prospects, can effectively improve soil quality, improve soil productivity and the farming environment, and promote sustainable agricultural development.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for promoting organic matter accumulation based on the soil food web level, characterized in that: The promotion of organic matter accumulation refers to promoting the accumulation of mineral-bound organic carbon in the soil; adding organic matter and nematodes to the cultivated soil; the nematodes are omnivorous nematodes and bacteriophages; the omnivorous nematodes are nematodes of the genus *Rhizophora*. P. quartusdecimus The bacteriophage nematode mentioned is a nematode of the family Microstemidae. D.veechi Nematodes of the genus *Pelvichorus* Panagrolaimus sp.; The organic matter is crop straw; the crop straw is crushed and mixed into the soil. The inoculation amount of the nematodes is 10-20 nematodes / g of soil; Predatory nematodes: The inoculation ratio of bacteriophages to nematodes was 1:1; The nematode family of small rods D.veechi : Pelvic pharynx nematodes Panagrolaimus The ratio of entries added for sp. is 1:

1.

2. The application of the method for promoting organic matter accumulation based on the soil food web level as described in claim 1 in the remediation of degraded soils or carbon sequestration in farmland.

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