Cultivation method for promoting solid storage of organic carbon and inorganic carbon in rice field soil

Abstract

The invention discloses a cultivation method for promoting solid storage of organic carbon and inorganic carbon in rice field soil. According to the cultivation method, the contents of organic carbon and inorganic carbon in 0-30 cm rice field soil are increased by combining treatment such as field weed control, field steeping and stubble pressing and applying the fertilizer to the soil with the depth of 10-15 cm, and the cultivation method for promoting organic carbon and inorganic carbon immobilization in the rice field soil is provided. The method provided by the invention not only can improve the solid storage of organic carbon and inorganic carbon in the rice field soil, but also can improve the nitrogen content, so that the use of fertilizers such as nitrogen fertilizers can be reduced. According to the invention, the loss of organic carbon in soil can be effectively reduced, the immobilization of inorganic carbon is increased, the fertility and structural stability of rice field soil are enhanced, the yield and quality of crops are ensured, the agricultural production cost can be reduced, the emission of greenhouse gases is reduced, and the sustainable development of agriculture is promoted.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of agricultural ecological engineering and environmental management. More specifically, it relates to a cultivation method for promoting the sequestration of organic and inorganic carbon in paddy soil. BACKGROUND

[0002] Carbon sequestration refers to the process of increasing the carbon content in carbon pools other than the atmosphere (such as soil, vegetation) through technical measures, including the sequestration of organic and inorganic carbon. Paddy soil, as an important carbon sink in the agricultural ecosystem, its carbon sequestration potential is significantly affected by tillage methods, management techniques and soil environment. Soil carbon mainly includes organic carbon (such as humus, microbial biomass carbon) and inorganic carbon (such as calcium carbonate and other carbonates). Traditional paddy cultivation methods usually use plowing and land preparation, although these methods help to improve crop yields in the short term, but will lead to the loss of soil organic carbon, soil structure damage. At the same time, traditional tillage methods (such as frequent plowing) and unreasonable water and fertilizer management often lead to soil acidification, accelerate the dissolution of carbonates and the loss of inorganic carbon (Lal, R. Soil carbon sequestration impacts on global climate change and food security. Science, 2004, 304(5677):1623-1627).

[0003] Existing research has found that no-till or straw mulching treatment on upland fields can maintain or improve soil organic carbon, but due to the complexity of soil types and tillage techniques itself, such treatment methods are not effective at all times and do not have universality. And no-till or straw mulching treatment mainly improves the organic carbon content of the surface layer (0-10 cm) soil, but the carbon content of the subsurface or deeper layer (10-30 cm) soil may actually decrease.

[0004] Rice field soil is a completely different soil type from upland soil, and there are significant differences between the two soil environments (Qi J, Chen B, Gao J, et al. Responses of soil bacterial community structure and function to dry–wet cycles more stable in paddy than in dryland agricultural ecosystems. Global Ecology and Biogeography, 2022, 31(2):362-377.). Rice field soil is in a long-term flooded state, with insufficient oxygen, which limits the movement and transformation of organic matter to the lower layer of soil, which not only affects the dynamic changes of carbon in the soil, but also makes some effective carbon sequestration measures in upland difficult to achieve the expected effect in rice fields (Chen X, Hu Y, Xia Y, et al. Contrasting pathways of carbon sequestration in paddy and upland soils Global change biology, 2021, 27(11):2478-2490.; Sousa, R.O.d., Carlos F S, Silva L S D, et al. No-tillage for flooded rice in Brazilian subtropical paddy fields: history, challenges, advances and perspectives. 2021.). For example, in the rice field environment, due to the particularity of water management, soil structure and biological activity, straw mulching and other technologies have not fully demonstrated their potential in subsoil carbon sequestration, and even due to the enrichment of straw in the surface layer, subsoil carbon sequestration shows a negative effect (Xue, J. F., Pu, C., Liu, S. L., Chen, Z.D., Chen, F., Xiao, X. P., Lal, R., Zhang, H. L., 2015. Effects of tillage systems on soil organic carbon and total nitrogen in a double paddy cropping system in Southern China.).For inorganic carbon, there are still few studies on the inorganic carbon sequestration in paddy soil, and the management measures optimized for the water chemical environment and soil microenvironment are lacking, which limits the long-term sequestration potential of inorganic carbon in paddy soil.

[0005] Although there are reports on increasing the organic carbon content of the 0-20 cm soil layer in paddy soil by adjusting the ratio of straw to nitrogen fertilizer application, this method is complex to operate, and the carbon sequestration potential of the subsoil (including organic carbon and inorganic carbon) is not fully considered. The subsoil (10-30 cm) has a huge carbon storage potential, and its carbon storage is much higher than that of the surface soil, which significantly contributes to global soil carbon sink. However, existing research and technology mainly focus on the management of organic matter in the surface soil, and the sequestration of organic carbon and inorganic carbon in the subsoil is not paid enough attention to. In summary, there is still a lack of simple and efficient cultivation methods for the sequestration of organic carbon and inorganic carbon in paddy soil, especially in the subsoil, and it is urgent to develop cultivation methods that can consider the sequestration of both forms of carbon. SUMMARY

[0006] The present application provides a cultivation method for promoting the sequestration of organic carbon and inorganic carbon in paddy soil.

[0007] The above-mentioned object of the present application is achieved by the following technical solutions: The present application provides a cultivation method for promoting the sequestration of organic carbon and inorganic carbon in paddy soil, which integrates the above-mentioned treatment methods. The sequestration of inorganic carbon in paddy soil is mainly achieved through the formation and stabilization of carbonate. The present application reduces soil disturbance through no-tillage and stubble pressing, maintains soil microenvironment pH, and promotes the combination of calcium and magnesium ions with dissolved CO2 to form carbonate. Deep fertilization (10-15 cm) optimizes soil microbial activity (increased K00031 and K00175 gene abundance), enhances the ability of chemoautotrophic microorganisms to fix CO2, and further stabilizes inorganic carbon. The coordinated water management (S2 and S4) slows down the dissolution of carbonate and prolongs its sequestration time. The method described in the present application can not only increase the sequestration of organic carbon and inorganic carbon in paddy soil, but also increase the nitrogen content, which is beneficial to optimizing soil structure, ensuring crop yield and quality, reducing the use of nitrogen fertilizer and other fertilizers, and reducing environmental pollution while reducing agricultural production costs. Therefore, the present application claims protection for the cultivation method.

[0008] The present application provides a cultivation method for promoting the sequestration of organic carbon and inorganic carbon in paddy soil, which includes the following steps: S1. Field grass control; remove weeds in the paddy field and retain rice stubble; S2. Soaking and stubble pressing; soaking the rice field with a water layer of 3-5 cm in height for 3-5 days, then carrying out land leveling and stubble pressing, and soaking the rice field with a water layer of 1-2 cm in height after stubble pressing; S3. Transplanting and fertilization; transplanting the seedlings into the rice field, applying the fertilizer into the soil of 10-15 cm in depth at the transplanting site as base fertilizer, and the application amount is 30-40 kg / mu; S4. Field management; carrying out water management during cultivation, and applying the fertilizer as topdressing at the tillering stage of the rice, and the fertilizer used is the same as that in S3, and the application amount is 20-30 kg / mu; S5. Harvesting.

[0009] Specifically, in S1, the weeds are killed by using pesticides, so as to realize the cleaning of the weeds. Optionally, the pesticide is Roundup 41% water agent herbicide.

[0010] Specifically, in S1, the height of the rice stubble is 10-20 cm.

[0011] Specifically, in S1, the variety of the rice stubble is not limited.

[0012] Specifically, in S2, the land leveling and stubble pressing are carried out by using a laser land leveler or by installing a metal crossbar in front of a transplanter.

[0013] Specifically, in S3, the seedlings are transplanted by using a pot seedling transplanter or a blanket seedling transplanter.

[0014] Specifically, in S3, when the seedlings are transplanted, the rows of the seedlings are staggered with the rows of the weeds, and the seedlings are planted by avoiding the rows.

[0015] Specifically, in S3, the mass ratio of nitrogen, phosphorus and potassium in the fertilizer is 14-16:3-5:4-6.

[0016] More specifically, in S3, the mass ratio of nitrogen, phosphorus and potassium in the fertilizer is 15:4:6.

[0017] Specifically, in S3, the application amount of the fertilizer is 35-40 kg / mu.

[0018] More specifically, in S3, the application amount of the fertilizer is 40 kg / mu.

[0019] Specifically, in S4, the application amount of the fertilizer is 20-25 kg / mu.

[0020] More specifically, in S4, the application amount of the fertilizer is 20 kg / mu.

[0021] Specifically, in S4, the fertilizer is scattered on the surface of the soil of the rice field, and does not need to be applied deeply.

[0022] Specifically, the method of the present application is to promote carbon sequestration in the soil of a rice field at a depth of 0-30 cm.

[0023] More specifically, the method of the present application is to promote carbon sequestration and nitrogen content in the soil of a rice field at a depth of 0-30 cm.

[0024] Specifically, the method is for cultivating aromatic rice.

[0025] In a specific embodiment of the present application, the aromatic rice variety is Qingxiangyou 19.

[0026] The present application has the following beneficial effects: The present application provides a cultivation method for promoting the sequestration of organic and inorganic carbon in the soil of a rice field, which can increase the content of organic and inorganic carbon in the soil of a rice field at a depth of 0-30 cm. In addition, the cultivation method of the present application can also increase the nitrogen content in the soil of a rice field, thereby reducing the use of fertilizers such as nitrogen fertilizer. The present application can effectively reduce the loss of soil organic carbon, increase the sequestration of inorganic carbon, and is conducive to enhancing the fertility and structural stability of the soil of a rice field, ensuring crop yield and quality, while also reducing agricultural production costs, reducing greenhouse gas emissions, and promoting sustainable agricultural development. DETAILED DESCRIPTION

[0027] The present application will be further described below in conjunction with specific examples, but the examples do not limit the present application in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present application are conventional reagents, methods, and equipment in the technical field.

[0028] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0029] Example 1: Effect of rice cultivation method on organic carbon and total nitrogen content in different depths of rice field soil In this embodiment, aromatic rice variety (Qingxiangyou 19) was used as the test rice, and two different rice cultivation methods (experimental group and control group, respectively) were used for cultivation. The rice cultivation method used in the experimental group includes the following steps: S1. Field grass control; before irrigating the rice field, complete the grass control management of the rice field to ensure that the field weeds are effectively eliminated, and the rice stubble is retained (the height of the rice stubble is about 15 cm); In this embodiment, the field grass control method is as follows: 3 weeks before transplanting, when the surface soil is dry, spray "Roundup" 41% aqueous herbicide, 2 bottles (200 ml / bottle) per mu to control weeds, and keep the surface dry for at least 5 days (usually 5-7 days) after spraying to ensure that the weeds are effectively eliminated; S2. Leveling and stubble crushing; water the field to a depth of 3-4 cm, keep the water for 4 days, then use a laser land leveler to level and crush the stubble once; if there is no laser land leveler, a metal crossbar can be installed in front of the rice transplanter to crush the stubble; keep a shallow water layer of 1-2 cm on the field surface until the rice seedlings are transplanted; S3. Transplanting and fertilization; the pot seedling technique is used in this embodiment, and a pot seedling transplanter (in addition, a blanket seedling transplanter can also be used) is used to transplant the cultivated seedlings; the rows of transplanted seedlings are staggered with the rows of weeds, and the planting is avoided, so as to improve the field management efficiency; at the same time, the fertilizer is applied to the soil at a depth of 10-15 cm as base fertilizer at the place where the seedlings are transplanted, and the fertilizer used is a special fertilizer for fragrant rice (the mass ratio of N, P and K in the fertilizer is 15:4:6, which is purchased from Dongguan Futai Biotechnology Co., Ltd.), and the application amount is 40 kg / mu.

[0030] S4. Field management; field management is performed during cultivation, and topdressing is applied during the tillering period of rice; the fertilizer used for topdressing is the same as above, and the application amount is 20 kg / mu.

[0031] S5. Harvesting.

[0032] Another piece of rice field soil at the same site is also provided with a control group in this embodiment, and the difference between the rice cultivation method used in the control group and that in the experimental group is that: in S2, instead of leveling and crushing the stubble, the soil is plowed twice, and the plowing depth is about 15 cm; and in S3, the fertilization method is to spread the fertilizer on the surface of the rice field.

[0033] After the rice is harvested in July, the rice field soil is sampled, and the organic carbon (C) and total nitrogen (N) contents (%) in the rice field soil at different depths (0-10 cm, 10-20 cm and 20-30 cm) are determined by using an element analyzer (Vario EL Cube, Germany). The C and N contents in the rice field soil of the experimental group (integrated technology) and the control group are shown in Table 1.

[0034] Table 1 Organic carbon and total nitrogen contents in the rice field soil of the experimental group and the control group

[0035] Note: Different letters represent significant differences P <0.05).

[0036] As shown in Table 1, compared with the control, the cultivation method described in this embodiment can significantly increase the organic carbon and total nitrogen contents in the rice field soil, and can be used to increase the carbon sequestration of the rice field soil.

[0037] Example 2 Analysis of carbon sequestration gene abundance in rice field soil In soil ecosystems, microorganisms fix CO2 through photoautotrophy or chemoautotrophy, thereby affecting the accumulation and carbon sequestration capacity of soil organic carbon. Carbon sequestration gene abundance refers to the relative content or expression level of functional genes related to the carbon sequestration process in the soil microbial community. These genes encode enzymes involved in the biological process of converting carbon dioxide (CO2) into organic carbon compounds, such as the common carbon sequestration pathways like the Calvin cycle. In this invention, the abundance of the two genes "K00031" and "K00175" was analyzed for the rice field soil samples collected in Example 1 by a commissioned company, in order to evaluate the impact of the cultivation method described in this invention on the carbon sequestration activities of microorganisms. "K00031" and "K00175" are specific carbon sequestration-related gene numbers in the KEGG database, which are closely related to carbon metabolism and energy production, particularly catalyzing two important reactions in the TCA cycle in sequence.

[0038] The results of the abundance analysis of K00031 and K00175 carbon sequestration genes in rice field soil are shown in Table 2. As shown in Table 2, compared with the control, the rice cultivation method described in Example 1 can improve the carbon sequestration activities of sub-surface microorganisms and promote carbon sequestration in rice field soil.

[0039] Table 2 Abundance analysis of K00031 and K00175 carbon sequestration genes in rice field soil

[0040] Example 3 Effect of rice cultivation method on organic carbon and total nitrogen content in rice field soil at different depths The difference between this example and Example 1 is the planting time of rice. In Example 1, the rice was planted in March, while in this example, the rice was planted in July of the same year. After the rice was harvested, rice field soil at different depths was collected, and the organic carbon and total nitrogen content in the rice field soil at different depths was analyzed and determined using the same method as in Example 1.

[0041] After analysis and determination, the organic carbon and total nitrogen content in the rice field soil of the experimental group and the control group of this example is shown in Table 3.

[0042] Table 3 Organic carbon and total nitrogen content in rice field soil of experimental group and control group

[0043] Note: Different letters indicate significant differences P <0.05).

[0044] As shown in Table 3, compared with the control, the cultivation method described in this example can significantly increase the organic carbon and total nitrogen content in the rice field soil, and can be used to improve carbon sequestration in rice field soil.

[0045] Example 4 Effect of different rice cultivation methods on carbon sequestration in paddy soil The present application further provides different rice cultivation methods. The same rice variety Qiangxiangyou 19 is cultivated in the same area using the different cultivation methods. After the rice is harvested, paddy soil samples at different depths are collected from each group, and the C content is determined and compared.

[0046] The different rice cultivation methods (divided into different groups) are as follows: Group 1: same as the experimental group in Example 1; Group 2: different from Group 1 only in that instead of land leveling and stubble pressing, rotary tillage is performed once; Group 3: different from Group 1 only in that instead of land leveling and stubble pressing, rotary tillage is performed twice; Group 4: same as the control group in Example 1.

[0047] The organic carbon content in the paddy soil samples at different depths in each group is determined using the same method as in Example 1, and the results are shown in Table 4. As shown in Table 4, the data of Group 2 and Group 3 are significantly different from those of Group 1, and not significantly different from those of the control group (Group 4), indicating that without stubble pressing, only deep application of fertilizer cannot promote carbon sequestration in paddy soil, i.e., there is a synergistic effect between stubble pressing and deep application of fertilizer, and the combination of the two can significantly improve carbon sequestration.

[0048] Table 4 Organic carbon content in paddy soil in different groups

[0049] Note: different letters indicate significant differences (P<0.05). P <0.05).

[0050] In addition to determining the organic carbon content, the inorganic carbon (IC) content in the paddy soil samples at different depths in each group is also determined. The inorganic carbon content in soil is determined using the acidification and non-acidification soil combined combustion method. The air-dried soil sample is passed through a 2 mm sieve, and the non-acidification sample is directly measured for total carbon (TC); the acidification sample is washed to neutral after removing carbonates with 1 mol / L HCl, and then measured for organic carbon (OC). TC and OC are determined using an elemental analyzer (Vario EL Cube) at high temperature combustion, and IC is calculated by the formula IC=TC-OC, with the unit of mg / kg. Each sample is repeated three times, and standard material calibration is performed to ensure accuracy. The inorganic carbon content in the paddy soil samples at different depths in each group is shown in Table 5. As shown in Table 5, compared with Group 1, the data of Group 2 and Group 3 are significantly different, indicating that the no-tillage treatment significantly increases the effect of inorganic carbon sequestration in the 0-30 cm soil profile.

[0051] Table 5 Inorganic carbon content in paddy soil in different groups

[0052] Note: different letters represent significant differences P <0.05).

[0053] In addition, the pH of the soil samples at different depths in each group was detected, and the results are shown in Table 6. As shown in Table 6, the method of the present application can improve the pH of the 0-20 cm soil layer. The acidification of deep soil may be affected by rhizosphere exudates. Since the present application adopts the no-tillage method, there are a large number of rice roots in the soil, and the rhizosphere effect is obvious, but it has little effect on carbon sequestration.

[0054] Table 6 pH of soil in different groups of rice fields

[0055] Example 5 Soluble inorganic carbon content detection The present application adopts the same cultivation method as groups 1-4 in example 4, and since 2016, a long-term positioning test has been conducted, and soil samples of the surface 0-10 cm of the rice field were collected before and after rice planting in October 2022 and March 2023, and the soluble inorganic carbon content in the soil samples was detected.

[0056] The determination of soil soluble inorganic carbon (DIC) is mainly completed by extraction and instrument analysis. First, weigh fresh or dried soil (10 g), add deionized water at a ratio of 1 (g):5 (mL), extract at 25℃ for 1 hour, centrifuge and filter with a 0.45μm filter membrane, collect the filtrate and store at 4℃, and complete the detection within 24 hours. The total organic carbon analyzer (TOC) is used to detect the total carbon content, and after the sample (filtrate) is acidified to remove inorganic carbon, the soluble carbon is converted to CO2 by high-temperature catalytic oxidation or wet oxidation, and the CO2 content is measured by a non-dispersive infrared detector (NDIR), to obtain the soluble organic carbon (DOC) content, which is calibrated with a standard solution of potassium hydrogen phthalate, and the DIC content is calculated by the formula DIC=TOC-DOC.

[0057] The results of the detection of the soluble organic carbon content in the soil of different groups of rice fields are shown in Table 7. As shown in Table 7, the method of the present application can significantly improve carbon sequestration.

[0058] Table 7 Soluble inorganic carbon content in soil of different groups of rice fields

[0059] Note: different letters represent significant differences P <0.05).

[0060] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications, etc. made without departing from the spirit and principles of the present application should be equivalent replacement manners and should be included in the protection scope of the present application.

Claims

1. A cultivation method for promoting organic carbon and inorganic carbon sequestration in paddy soil, characterized by, The method comprises the following steps: S1. Controlling weeds in the field; removing weeds in the rice field, and leaving rice stubble; S2. Soaking the field and crushing the stubble; soaking the rice field with a water layer of 3-5 cm in height for 3-5 days, then flattening the field and crushing the stubble, and soaking the field with a water layer of 1-2 cm in height after crushing the stubble until rice seedlings are transplanted; S3. Transplanting seedlings and applying fertilizer; transplanting seedlings into the rice field, applying fertilizer into the soil at a depth of 10-15 cm at the transplanting site as base fertilizer, and the application amount is 30-40 kg per mu; S4. Field management; performing water management during cultivation, and applying topdressing during the tillering stage of rice, and the fertilizer used is the same as that in S3, and the application amount is 20-30 kg per mu; S5. Harvesting.

2. The method of claim 1, wherein In S1, the height of the rice stubble is 10-20 cm.

3. The method of claim 1, wherein, In S2, a laser land leveler is used to flatten the field and crush the stubble, or a metal crossbar is installed in front of a rice transplanter to flatten the field and crush the stubble.

4. The method of claim 1, wherein, In S3, a pot seedling transplanter or a blanket seedling transplanter is used to transplant seedlings.

5. The method of claim 1, wherein In S3, the mass ratio of nitrogen, phosphorus and potassium in the fertilizer used is 14-16:3-5:4-6, and the application amount of the fertilizer is 35-40 kg per mu.

6. The method of claim 1, wherein In S4, the application amount of the fertilizer is 20-25 kg per mu.

7. The method of claim 5, wherein In S3, the mass ratio of nitrogen, phosphorus and potassium in the fertilizer used is 15:4:6, and the application amount of the fertilizer is 40 kg per mu.

8. The method of claim 6, wherein In S4, the application amount of the fertilizer is 20 kg per mu.

9. The method according to any one of claims 1 to 8, characterized in that, The method is to promote the sequestration of organic carbon and inorganic carbon in the soil of the rice field with a depth of 0-30 cm.

10. The method of any one of claims 1 to 8, wherein, The method is used for cultivating fragrant rice.

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