A method for mitigating soil organic carbon loss under intense ultraviolet light exposure

Abstract

The application discloses a method for relieving loss of soil organic carbon under strong ultraviolet light, and belongs to the technical field of soil protection and agricultural environmental management. In the method, fulvic acid is applied to soil, carbon-fixing microorganisms are added, and a plastic film is covered on the surface of the soil to construct a triple protection system of biochemical stability-microbial carbon fixation-physical barrier, so that the protection capability of the soil carbon pool under strong ultraviolet environment is significantly enhanced. Microbial sequencing results show that the system reverses the relationship between microorganisms and particulate organic carbon (POC), and simultaneously strengthens the positive correlation between microorganisms and mineral-associated organic carbon (MAOC), and exhibits a more extensive and significant positive correlation effect. The mechanism effectively inhibits the decomposition and loss of MAOC and POC in the soil under strong ultraviolet radiation, and improves the stability of the carbon pool related to MAOC and POC. The method is suitable for farmland soil management in high-altitude and strong-sunlight areas.

Description

Technical Field

[0001] This invention relates to the field of soil protection and agricultural environmental management technology, specifically a method for mitigating soil organic carbon loss under strong ultraviolet radiation. Background Technology

[0002] High-altitude agricultural areas with strong ultraviolet radiation, such as the Qinghai-Tibet Plateau, face even stronger ultraviolet radiation exposure due to the thinner atmosphere and limited vegetation recovery capacity. Under strong ultraviolet radiation, soil organic matter is prone to photodegradation, leading to a significant loss of soil carbon pools and consequently, problems such as decreased soil fertility and structural degradation. Particulate organic carbon (POC), due to its relatively loose structure and high exposure, is easily degraded directly by ultraviolet light, resulting in rapid short-term carbon pool loss. While mineral-bound organic carbon (MAOC) is more tightly bound to soil minerals, strong ultraviolet radiation disrupts soil aggregate structure, indirectly causing MAOC desorption and decomposition, ultimately leading to the decline of soil carbon pool function and fertility. Studies have shown that ultraviolet radiation accelerates the mineralization process of soil organic carbon, especially in plateau, arid, and semi-arid regions where the intensity and duration of ultraviolet radiation are high, resulting in more significant soil carbon loss.

[0003] Common measures to mitigate soil carbon loss include adding organic materials; patent applications for mulching crop straw (a method for increasing soil organic carbon content by returning straw to the field: 202310402826.X[P]. 2023-12-26.) utilize straw return to the field to increase soil organic carbon content; patent applications for applying biochar (a method for promoting soil carbon sequestration with biochar: 202211385034.8[P]. 2023-03-07.) utilize renewable biomass to produce biochar and add it to the soil. However, these methods have limited effectiveness under strong ultraviolet (UV) conditions: organic materials themselves are easily decomposed by UV light, which not only fails to increase POC content but may also exacerbate carbon loss due to their own degradation; although straw mulching can block UV light to some extent, it degrades quickly and has a short duration of effectiveness, making it difficult to protect POC in the long term, and it does not directly promote the formation and stability of MAOC; although biochar has high stability, it is expensive and may inhibit soil microbial activity, thus affecting the conversion efficiency of POC to MAOC.

[0004] Therefore, developing an economical, efficient, easy-to-operate soil mineral-bound organic carbon (MAOC) and particulate organic carbon (POC) protection technology applicable to areas with strong ultraviolet radiation is of great ecological and economic significance. Summary of the Invention

[0005] To address the significant loss of both mineral-bound and particulate organic carbon in soil under strong ultraviolet (UV) radiation, this invention provides a method for mitigating soil organic carbon loss under UV radiation, the method specifically comprising the following steps: (1) The carbon-fixing microorganisms were cultured to obtain carbon-fixing microbial culture solution.

[0006] (2) Apply humic acid to the soil and spray carbon-fixing microbial liquid into the soil to alleviate the loss of soil organic carbon under strong ultraviolet light.

[0007] Preferably, the carbon-fixing microorganism in step (1) of the present invention is Rhodopseudomonas palustris.

[0008] Preferably, the process of culturing carbon-fixing microorganisms in step (1) of the present invention is as follows: the carbon-fixing microorganisms are inoculated into a liquid culture medium, and the microorganisms are cultured at 25~30℃ under anaerobic conditions, and continuously illuminated with a 40-watt tungsten filament lamp for 5~7 days.

[0009] Preferably, the components and contents of the liquid culture medium of the present invention are as follows: K2HPO4 1.0 g / L, MgSO4 0.5 g / L, yeast extract 10.0 g / L, distilled water as solvent, pH 7.0-7.2; the liquid culture medium is used after sterilization at 121℃ for 15 min.

[0010] Preferably, the OD600 of the carbon-fixing microbial liquid in step (1) of the present invention is 0.75-0.8.

[0011] Preferably, the humic acid in step (2) of the present invention is fulvic acid.

[0012] Preferably, the amount of humic acid applied in step (2) of the present invention is 0.3% to 0.5% of the dry weight of the soil.

[0013] Preferably, the amount of carbon-fixing microbial inoculum used in step (2) of the present invention is 0.002-0.02 mL / g. 干土 .

[0014] Preferably, the plastic film in step (2) of the present invention is a white ordinary plastic film.

[0015] Preferably, in step (2) of the present invention, humic acid and carbon-fixing microbial inoculum can be mixed with the topsoil at a depth of 5-10cm by tilling.

[0016] Preferably, the soil moisture content is 15wt%-20wt% throughout the process of mitigating soil organic carbon loss under strong ultraviolet light, which can provide the best activity environment for Rhodopseudomonas palustris, thereby achieving the best effect of mitigating organic carbon loss in synergy with humic acid and plastic film.

[0017] Preferably, the present invention covers the soil surface with a plastic film within 1-2 hours after spraying the bacterial solution to avoid prolonged exposure, thus preventing bacterial inactivation and locking in moisture, and ensuring the overall carbon fixation effect.

[0018] Mechanism of this invention: This invention achieves a synergistic effect of carbon pool stabilization and reduced carbon loss through the combined use of fulvic acid, carbon-fixing microorganisms, and mulch film. Specifically, mulch film first provides a physical barrier layer, effectively attenuating ultraviolet radiation flux and reducing its photochemical degradation effect on soil organic matter. Simultaneously, it creates a stable microenvironment for microbial activity. Based on this physical protection, fulvic acid, as a low-molecular-weight humic component, enhances the chemical stability of mineral-bound organic carbon on one hand, and as an easily degradable organic carbon source on the other, rapidly activating the metabolic activity of soil microbial communities. Under the dual conditions of physical barrier protection and sufficient nutrient substrate, the carbon-fixing microorganisms maximize their carbon-fixing efficiency. These microorganisms convert gaseous CO2 into organic carbon through photosynthesis or chemosynthesis, directly replenishing the particulate organic carbon pool. Simultaneously, by secreting extracellular polymers and other metabolites, they promote the formation of soil micro-aggregates, providing physical protection for particulate organic carbon and accelerating its conversion into mineral-bound organic carbon.

[0019] This invention significantly alters the soil carbon cycle pathway through the synergistic effect of three components. The reconstruction of the microbial community structure and function turns the correlation between microorganisms and particulate organic carbon from negative to positive, and significantly enhances the positive correlation with mineral-bound organic carbon. This reflects the functional transformation of the system from carbon depletion to carbon sequestration. Experimental data confirm that this combined treatment significantly increases the content of mineral-bound organic carbon and particulate organic carbon, and significantly enhances the stability of the carbon pool.

[0020] Compared with existing technologies, the present invention provides a method for mitigating soil organic carbon loss under strong ultraviolet radiation, which has the following beneficial effects: (1) This invention transforms the negative correlation between microorganisms and particulate organic carbon into a positive correlation by changing the structure of the microbial community, significantly enhancing the positive correlation with mineral-bound organic carbon, and promoting the transformation of soil carbon cycle from carbon depletion to carbon sequestration.

[0021] (2) This scheme technically achieves the coupling of multiple protection mechanisms. Mulch film effectively blocks ultraviolet radiation, reduces the photodegradation rate of soil organic carbon, and improves the soil microenvironment; fulvic acid enhances the stability of mineral-bound organic carbon through coordination with mineral surfaces and activates soil microbial communities as a carbon source available to microorganisms; carbon-fixing microorganisms fully exert their carbon-fixing function under suitable conditions, not only directly replenishing the particulate organic carbon pool, but also promoting aggregate formation by secreting extracellular polymers, accelerating the conversion of particulate organic carbon into mineral-bound organic carbon. The synergistic effect of the three significantly improves the stability and decomposition resistance of the soil carbon pool.

[0022] (3) The materials used in this invention are widely available and inexpensive. Fulvic acid can be obtained from industrial and agricultural by-products. Mulch film covering is easy to operate and readily accepted by farmers. Compared with biochar and other methods, this solution is more economical and is particularly suitable for promotion and application in areas with limited economic conditions and severe ultraviolet disasters.

[0023] (4) The present invention has produced significant agronomic benefits. The moisture retention and warming effect of mulch film combined with the water-holding capacity of humic acid creates more suitable hydrothermal conditions for crop growth, which helps to alleviate ultraviolet radiation stress. While protecting the soil carbon pool, it promotes crop growth and achieves the unity of ecological and agronomic benefits. Attached Figure Description

[0024] Figure 1 This is a comparison chart showing the effects of microorganisms treated with agricultural measures in Example 1 of the present invention and those not treated with agricultural measures in Comparative Example 4 on POC and MAOC. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The embodiments and comparative examples of this invention were all conducted in a specially designed microcosm device to simulate a specific ultraviolet radiation environment. The simulated ultraviolet radiation was provided by a UVA lamp (main peak wavelength 365nm), which served as the only ultraviolet light source in the system. To ensure the precise controllability of the illumination parameters, the outer walls of all experimental devices were completely covered with light-shielding black velvet to achieve physical isolation from the external environment.

[0027] The components and contents of the liquid culture medium used in the embodiments and comparative examples of this invention are as follows: K2HPO4 1.0 g / L, MgSO4 0.5 g / L, yeast extract 10.0 g / L, distilled water as solvent, pH 7.0-7.2; the liquid culture medium is used after sterilization at 121℃ for 15 min.

[0028] The white ordinary plastic film used in the embodiments and comparative examples of this invention has a light transmittance of 40%-60% and a thickness of 0.03mm-0.08mm. Example 1

[0029] A method for mitigating soil organic carbon loss under strong ultraviolet radiation includes the following steps: (1) Rhodopseudomonas swampis was inoculated into liquid culture medium and cultured at 25°C under anaerobic conditions. A 40-watt tungsten filament lamp was used for continuous illumination for 6 days to obtain carbon-fixing microbial culture (the OD600 of the culture was 0.78).

[0030] (2) Apply humic acid to the soil (the amount of humic acid applied is 0.4% of the soil weight), and spray carbon-fixing microbial inoculum into the soil (the amount of carbon-fixing microbial inoculum applied is 0.01 mL / g). 干土 One hour after spraying the bacterial solution, cover the soil surface with a white ordinary plastic film. The humic acid and carbon-fixing microbial solution are then mixed with the topsoil to a depth of 5-10 cm by tilling (the soil moisture content is 15wt%-20wt% throughout the process of mitigating the loss of soil organic carbon under strong ultraviolet light). Example 2

[0031] A method for mitigating soil organic carbon loss under strong ultraviolet radiation includes the following steps: (1) Rhodopseudomonas swampis was inoculated into liquid culture medium and cultured at 27°C under anaerobic conditions. A 40-watt tungsten filament lamp was used for continuous illumination for 7 days to obtain carbon-fixing microbial culture (the OD600 of the culture was 0.75).

[0032] (2) Apply humic acid to the soil (the amount of humic acid applied is 0.3% of the soil weight), and spray carbon-fixing microbial inoculum into the soil (the amount of carbon-fixing microbial inoculum applied is 0.002 mL / g). 干土 Within 1.5 hours after spraying the bacterial solution, cover the soil surface with a white ordinary plastic film. Mix the humic acid and carbon-fixing microbial solution with the topsoil to a depth of 5-10cm by tilling (the soil moisture is 15wt%-20wt% throughout the process of mitigating the loss of soil organic carbon under strong ultraviolet light).

[0033] The carbon fixation effect in this embodiment is similar to that in Embodiment 1. Example 3

[0034] A method for mitigating soil organic carbon loss under strong ultraviolet radiation includes the following steps: (1) Rhodopseudomonas swampis was inoculated into liquid culture medium and cultured at 30°C under anaerobic conditions. A 40-watt tungsten filament lamp was used for continuous illumination for 5 days to obtain carbon-fixing microbial culture (the OD600 of the culture was 0.80).

[0035] (2) Apply humic acid to the soil (the amount of humic acid applied is 0.5% of the soil weight), and spray carbon-fixing microbial inoculum into the soil (the amount of carbon-fixing microbial inoculum applied is 0.02 mL / g). 干土Two hours after spraying the bacterial solution, cover the soil surface with a white ordinary plastic film. The humic acid and carbon-fixing microbial solution are then mixed with the topsoil to a depth of 5-10 cm by tilling (the soil moisture content is 15wt%-20wt% throughout the process of mitigating the loss of soil organic carbon under strong ultraviolet light).

[0036] Comparative Example 1 The difference between this comparative example and Example 1 is that humic acid is not used, carbon-fixing microbial inoculum is not added, and white plastic film is not used for covering. The other conditions are the same as in Example 1, and the treatment is carried out under simulated strong ultraviolet light conditions.

[0037] In this comparative example, no humic acid, carbon-fixing microbial inoculum, or white plastic film covering was used. Under strong ultraviolet light, the organic carbon loss was relatively severe.

[0038] Comparative Example 2 The difference between this comparative example and Example 1 is that humic acid was used, no carbon-fixing microbial inoculum was added, and no white plastic film was used for covering. The other conditions were the same as in Example 1, and the samples were treated under simulated strong ultraviolet light conditions.

[0039] This comparative example only added humic acid, which was effective in increasing MAOC, but had limited effect on increasing POC, indicating a lack of microbial activity to transform and form new particulate organic carbon.

[0040] Comparative Example 3 The difference between this comparative example and Example 1 is that humic acid is not used, carbon-fixing microbial inoculum is not added, and a white plastic film is used for covering. The other conditions are the same as in Example 1, and the treatment is carried out under simulated strong ultraviolet light conditions.

[0041] This comparative example uses only white plastic film. In the absence of exogenous carbon (humic acid) and carbon-fixing microorganisms, film covering promotes the microbial decomposition (mineralization) of the original MAOC in the soil, resulting in a decrease in its net content.

[0042] Comparative Example 4 The difference between this comparative example and Example 1 is that humic acid is not used, carbon-fixing microbial inoculum is added, and white plastic film is not used for covering. The other conditions are the same as in Example 1, and the treatment is carried out under simulated strong ultraviolet light conditions.

[0043] In this comparative example, only carbon-fixing microbial inoculum was added. Under direct irradiation with strong ultraviolet light, the carbon-fixing microorganisms could not survive or were even killed. The death and decomposition of the carbon-fixing microorganisms stimulated the decomposition of the original organic carbon in the soil by the indigenous microorganisms, resulting in a net loss of carbon.

[0044] Comparative Example 5 The difference between this comparative example and Example 1 is that humic acid was used, no carbon-fixing microbial inoculum was added, and a white plastic film was used for covering. The other conditions were the same as in Example 1, and the samples were treated under simulated strong ultraviolet light conditions.

[0045] This comparative example uses humic acid and white plastic film. Under physical protection, fulvic acid, as a carbon source, can promote the activity of native microorganisms in the soil to a certain extent, thereby producing POC. However, it lacks dedicated carbon-fixing microorganisms, and its ability to further transform and stabilize carbon (form MAOC) is limited.

[0046] Comparative Example 6 The difference between this comparative example and Example 1 is that humic acid is not used, carbon-fixing microbial inoculum is added, and a white plastic film is used for covering. The other conditions are the same as in Example 1, and the treatment is carried out under simulated strong ultraviolet light conditions.

[0047] This comparative example used carbon-fixing microbial inoculum and a white plastic film. Although the film protected the microorganisms, the efficiency and survival competition of the carbon-fixing microorganisms were not ideal due to the lack of fulvic acid. The effect was only slightly better than the blank control group and far lower than the effect of Example 1, indicating that exogenous carbon is beneficial to stimulating the carbon-fixing ability of microorganisms.

[0048] Comparative Example 7 The difference between this comparative example and Example 1 is that humic acid was used, carbon-fixing microbial inoculum was added, and white plastic film was not used for covering. The other conditions were the same as in Example 1, and the samples were treated under simulated strong ultraviolet light conditions.

[0049] This comparative example uses humic acid and carbon-fixing microbial inoculum. Despite the presence of carbon source and inoculum, strong ultraviolet light still inhibits the formation and maintenance of POC activity by microorganisms (whether carbon-fixing bacteria or other beneficial bacteria).

[0050] On day 32, soil samples from Examples 1-3 and Comparative Examples 1-7 were collected to determine the MAOC and POC contents and to perform sequencing analysis on microorganisms. The MAOC and POC contents of the soil are shown in Table 1.

[0051] Table 1

[0052] Table 1 shows that applying humic acid alone (Comparative Example 2), adding carbon-fixing microbial inoculum alone (Comparative Example 4), covering with white plastic film alone (Comparative Example 3), or using a combination of these three treatments (Comparative Examples 5-7) did not significantly increase the combined content of soil mineral-bound organic carbon and particulate organic carbon under strong ultraviolet radiation. However, the combined effect of applying humic acid, carbon-fixing microorganisms, and covering with plastic film significantly increased the combined content of soil mineral-bound organic carbon and particulate organic carbon, with MAOC increasing by 16.31% and POC increasing by 46.39% compared to Comparative Example 1.

[0053] Based on soil microbial sequencing analysis, the relationship between agricultural-driven "sensitive" microorganisms and POC and MAOC in the combined application of humic acid, carbon-fixing microorganisms, and plastic film mulching on day 32 is as follows: Figure 1 As shown in the figure. Compared with the control group without agricultural treatment, after treatment with a combination of humic acid, carbon-fixing microorganisms, and plastic film covering, the effect sizes of all bacterial and fungal phyla in the POC (Proteinized Organic Carbon) group without agricultural treatment fluctuated around 0 and were significantly negatively correlated, indicating that the microbial phyla had no significant effect on POC without agricultural treatment. After adding agricultural treatment, some bacteria showed significant effects and positive correlations, indicating that agricultural treatment had a certain effect on increasing POC content. In terms of MAOC (Massively Active Organic Carbon), without agricultural treatment, only a few phyla had a weak and significant effect, and the effect sizes of most phyla fluctuated around 0, indicating that the overall effect of microorganisms on MAOC was not significant without agricultural treatment. After adding agricultural treatment, several phyla showed significant effects, and the effect sizes deviated from 0 to a greater extent, indicating that agricultural treatment significantly enhanced the regulatory effect of these microbial phyla on MAOC.

[0054] In summary, this invention, through the combined application of fulvic acid, carbon-fixing microorganisms, and ordinary white plastic film, can specifically address the core issues of POC photodegradation and MAOC desorption under strong ultraviolet light, thereby increasing and stabilizing the content of these two key carbon components. It is also economical and scalable, suitable for farmland soil management in high-altitude, high-sunlight areas, and is of great significance for maintaining soil carbon pool function and promoting sustainable agricultural development.

[0055] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for mitigating soil organic carbon loss under strong ultraviolet radiation, characterized in that, Specifically, the following steps are included: (1) The carbon-fixing microorganisms are cultured to obtain a carbon-fixing microbial culture; the carbon-fixing microorganism is Rhodopseudomonas palustris, and the OD600 of the carbon-fixing microbial culture is 0.75-0.8; (2) Apply fulvic acid to the soil and spray carbon-fixing microbial inoculum into the soil. Cover the soil surface with plastic film 1-2 hours after spraying the inoculum to alleviate the loss of soil organic carbon under strong ultraviolet light. The synergistic effect of carbon pool stabilization and carbon loss reduction is achieved by using fulvic acid, carbon-fixing microorganisms and plastic film mulching together. Specifically, plastic film mulching first provides a physical barrier layer, effectively attenuating the ultraviolet radiation flux and reducing its photochemical degradation effect on soil organic matter. At the same time, it creates a stable microenvironment for microbial activity. On the basis of this physical protection, fulvic acid, as a low molecular weight humic component, enhances the chemical stability of mineral-bound organic carbon on the one hand; on the other hand, as an easily degradable organic carbon source, it quickly activates the metabolic activity of soil microbial community. Carbon-fixing microorganisms maximize their carbon fixation efficiency under the dual conditions of physical barrier protection and sufficient nutrient matrix. Through the synergistic effect of the three components, the soil carbon cycle pathway is significantly altered. The reconstruction of the microbial community structure and function turns the correlation between microorganisms and particulate organic carbon from negative to positive and enhances the positive correlation with mineral-bound organic carbon. The plastic film is a white, ordinary plastic film; The application rate of fulvic acid is 0.3%-0.5% of the soil dry weight; the soil moisture content is 15wt%-20wt% throughout the process of mitigating soil organic carbon loss under strong ultraviolet light; the application rate of carbon-fixing microbial inoculant solution is 0.002-0.02 mL / g. 干土 ; The humic acid and carbon-fixing microbial inoculum are mixed with the topsoil at a depth of 5-10 cm by tilling.

2. The method for mitigating soil organic carbon loss under strong ultraviolet radiation according to claim 1, characterized in that, The specific steps for culturing carbon-fixing microorganisms in step (1) are as follows: the carbon-fixing microorganisms are inoculated into a liquid culture medium, and the microorganisms are cultured at 25-30℃ under anaerobic conditions, and continuously illuminated with a 40-watt tungsten filament lamp for 5-7 days.

3. The method for mitigating soil organic carbon loss under strong ultraviolet radiation according to claim 2, characterized in that, The components and contents of the liquid culture medium are as follows: K2HPO4 1.0 g / L, MgSO4 0.5 g / L, yeast extract 10.0 g / L, the liquid matrix is ​​distilled water, pH 7.0-7.2; the liquid culture medium is used after sterilization at 121℃ for 15 min.

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