Grassland nitrogen fixation and carbon promotion method

Abstract

A grassland nitrogen fixation and carbon promotion method relates to the field of grassland carbon sequestration, and is characterized in that based on the ecological characteristics of grassland, perennial leguminous plants white clover and medicago sativa are selected, and are sown in the grassland in cooperation with an annual leguminous plant sweet potato. The perennial leguminous plants are long in service life, litters can be provided for multiple times, turnover of plant carbon to soil carbon is promoted, and the sweet potato can effectively improve rhizosphere microflora, promote growth and reproduction of nitrogen-fixing bacteria and improve nitrogen fixation efficiency. The matching mode can play a role in mutual complementation and mutual promotion. Meanwhile, the three plants are also plants with excellent nitrogen fixation effect, and can quickly supplement available nitrogen required by soil and provide nutrients required by plant growth, so that the grassland plant production is improved, and the purposes of improving the soil carbon reserve and enhancing the grassland soil carbon sink are achieved. The method is simple to operate and low in cost, and has better popularization value.

Description

Technical Field

[0001] The present invention relates to the field of grassland carbon sink, and in particular to a method for nitrogen fixation and carbon promotion in grassland. Background Art

[0002] In recent decades, the global average annual temperature and carbon dioxide concentration have continued to rise, and global climate change has become a focus of common concern for governments, the public and the scientific community. In March 2023, the United Nations Intergovernmental Panel on Climate Change (IPCC) released the sixth assessment report "Climate Change 2023", which pointed out that human activities, mainly through the emission of greenhouse gases, have undoubtedly caused global warming: from 2011 to 2020, the global average surface temperature was 1.1°C higher than that from 1850 to 1900. Extensive and rapid changes have taken place in the atmosphere, oceans, cryosphere and biosphere, and human-induced climate change has affected many extreme weather and climate events in every region of the world. The increase in global temperature rise will bring more severe heat waves, more intense rainfall and other extreme events, further increasing the risks to human health and ecosystems. Against the background of rising global temperatures and frequent extreme climate events, the research and development of soil nitrogen fixation and carbon promotion technology is of great significance in responding to global climate change and mitigating the greenhouse effect, and it also poses a huge challenge to how to enhance the soil carbon sink function.

[0003] Terrestrial ecosystems play an important role in the global carbon balance. Using terrestrial ecosystems to fix carbon can, to a certain extent, slow down global carbon emissions. Grassland is an important component of terrestrial ecosystems. From the perspective of plant ecology, grassland refers to communities dominated by herbaceous plants, mainly including natural vegetation such as grasslands, meadows, herbaceous swamps, herbaceous tundra, and grass, as well as cultivated communities dominated by herbaceous plants in addition to crops. my country has extremely rich grassland resources, which are mainly distributed in the western and northern regions, including Tibet, Inner Mongolia, Xinjiang, Qinghai and other provinces, accounting for about 30.5% of the country's land area. Grassland ecosystems store a large amount of carbon and are important carbon pools with great potential to increase carbon sink functions. Therefore, improving the carbon sequestration capacity of grasslands and maintaining the stability of grassland carbon sinks are of great significance to mitigating global climate change and promoting the implementation of the dual carbon policy.

[0004] At present, there are few reports on the technology of nitrogen fixation and carbon promotion in grassland water and fertilizer management in China. Considering the current situation of global climate change and my country's emphasis on carbon sequestration in forestry and grassland, how to improve the carbon sequestration function of grassland soil and increase soil carbon storage while maintaining the function of grassland ecosystem, protecting biodiversity, improving grassland productivity and grassland vegetation coverage is an urgent problem to be solved. Summary of the invention

[0005] The purpose of the present invention is to provide a method for fixing nitrogen and promoting carbon in grassland, which is simple and quick to operate, can effectively improve the nitrogen fixation effect of grassland, thereby enhancing the carbon sink function of soil, and has good promotion value.

[0006] The embodiment of the present invention is achieved as follows:

[0007] A method for fixing nitrogen and promoting carbon in grassland, characterized by comprising:

[0008] Plant white clover, lucerne and glossy-leaved vetch in the grassland.

[0009] The beneficial effects of the embodiments of the present invention are:

[0010] The present invention provides a method for promoting carbon fixation in grasslands. Based on the ecological characteristics of the grassland itself, perennial legumes white clover and Medicago sativa L. are selected, and the annual legumes light-leaved purple flower vetch are sown in the grassland. Perennial legumes have a long life span and can provide litter for many times, promoting the turnover of plant carbon to soil carbon. Light-leaved purple flower vetch can effectively improve the rhizosphere microbial community, promote the growth and reproduction of nitrogen-fixing bacteria, and improve nitrogen fixation efficiency. This combination can complement and promote each other. At the same time, these three plants are also plants with excellent nitrogen fixation effects, which can quickly replenish the effective nitrogen required by the soil and provide the nutrients required for plant growth, thereby increasing the production of grassland plants, and then achieving the purpose of increasing soil carbon reserves and enhancing grassland soil carbon sinks. The method is simple to operate, low cost, and has good promotion value. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0012] The following is a detailed description of a method for nitrogen fixation and carbon promotion in grassland according to an embodiment of the present invention.

[0013] The embodiment of the present invention provides a method for fixing nitrogen and promoting carbon in grassland, which comprises:

[0014] Plant white clover, lucerne and glossy-leaved vetch in the grassland.

[0015] There have been many studies on increasing the organic carbon content in the soil by planting green manure in the existing technology. However, traditional green manure planting usually adopts the practice of in-situ harvesting and plowing to return the field. There are problems such as low carbon sequestration efficiency, high economic and labor costs, and being unfavorable to improving soil fertility in terms of grassland soil carbon sequestration and sink. At the same time, the practice of in-situ harvesting and plowing to return the field will destroy the soil structure, which is not conducive to the formation of soil aggregates, and will hinder grassland soil carbon sequestration and emission reduction.

[0016] Nitrogen is an important component of chlorophyll, and chlorophyll is a key molecule of photosynthesis. With enough nitrogen, plants can synthesize more chlorophyll, thereby improving the efficiency of photosynthesis and increasing the fixation of carbon. Therefore, plant nitrogen fixation can improve the availability of nitrogen, promote the assimilation accumulation of photosynthesis and carbon, and play an important role in plant growth and ecosystem carbon cycle. The raw white clover, alfalfa and light-leaf purple flower vetch adopted by the present invention all belong to leguminous plants, have good nitrogen fixation ability, can establish a symbiotic relationship with nitrogen-fixing bacteria, fix atmospheric nitrogen to ammonia available to plants, and convert it into amino acids, proteins and other nitrogen-containing organic matter, providing nitrogen nutrients required for plant growth. Secondly, plants can also be allowed to synthesize more chlorophyll, improve the efficiency of photosynthesis, thereby fix carbon to a greater extent, and improve the carbon fixation efficiency of grassland.

[0017] Furthermore, the present invention has been comprehensively considered, combined with soil conditions, climate, topography, economic costs and other factors, and specially selected perennial legume white clover and perennial legume alfalfa to match annual legume Vetch. Perennial legumes have a long lifespan, can provide litter for many times, and promote the turnover of plant carbon to soil carbon. Vetch can effectively improve the rhizosphere microbial community, promote the growth and reproduction of nitrogen-fixing bacteria, and improve nitrogen fixation efficiency. This matching method can complement and promote each other. These three plants are all excellent forage grasses, with strong universality, a wide range of growth, can grow under harsh soil conditions, have strong vitality, can ensure a high emergence rate and survival rate, have strong adaptability to climate, and can adapt well to the hot and humid climate conditions in the south.

[0018] Forests and grasslands are both the most common terrestrial ecosystems, but the two are essentially different. In contrast, there are huge differences in the vertical structure of forest vegetation, with a small number of understory species and relatively weak species competition. In contrast, the grassland environment has a large number of local species, and species competition is relatively strong, which is not conducive to the growth of green manure. The white clover and glossy-leaved purple flower vetch used in the present invention are not local species. The inventors have planted the above two plants in a forest environment and achieved better results, but the same planting conditions are difficult to implement in a grassland environment due to species competition problems. Especially for glossy-leaved purple flower vetch, its thick seed coat makes it have strong cold resistance, but it also causes the adverse effects of slightly harsh germination conditions and long germination time, resulting in glossy-leaved purple flower vetch being easily affected in the competition with native species, which is specifically manifested in a significant reduction in the emergence rate, which affects the nitrogen fixation and carbon promotion effect. However, the root microbial community structure of Vitis glabra is conducive to the growth and reproduction of nitrogen-fixing bacteria, and its nitrogen fixation efficiency ranks among the top in legumes. It has a high nitrogen fixation effect and plays an irreplaceable role in the present invention. The inventors have screened a large number of legumes, but have not been able to find a plant that can completely replace the effect of Vitis glabra.

[0019] In view of the above problems, the inventor introduced a third legume, the perennial legume alfalfa, after a lot of attempts. Although alfalfa is not a native species, it is more suitable for grassland environment than light-leaved purple flower vetch. The alfalfa seeds are small, the seed coat is thin, the germination time is short, and the germination conditions are easy to meet. It belongs to a common fine forage variety. According to research, its root secretions have a significant impact on the soil environment, can regulate the rhizosphere ecological environment, improve the soil microbial community structure, promote the growth of nitrogen-fixing bacteria, induce nitrogen-fixing bacteria to reproduce, and help improve nitrogen fixation and carbon efficiency. The root secretions of alfalfa can not only effectively help alfalfa resist native species, but also promote the growth of alfalfa in harsh environments. At the same time, its root secretions can also regulate the soil environment, help white clover and light-leaved purple flower vetch resist species competition, and play an auxiliary role in the growth of white clover and light-leaved purple flower vetch. Mixing these three plants can achieve mutual benefit and promote the effect of growth.

[0020] Optionally, the method for fixing nitrogen and promoting carbon in grassland is characterized in that the sowing ratio of white clover, Medicago sativa, and Vicia glabra is 1:0.3-0.6:0.3-0.6. Under this ratio, the synergistic effect of the three plants is better, the emergence rate of Vicia glabra can be increased, and the carbon fixation effect is greatly improved.

[0021] Furthermore, the planting density of white clover is 10-15 g / m 2 The planting density of purple lucerne and purple vetch is 5-8g / m 2Within this sowing rate range, the planting density of white clover, Medicago truncatula, and Vetch glabra is appropriate, which not only has a higher carbon fixation efficiency but also can better ensure the survival rate.

[0022] Optionally, the sowing time of white clover, alfalfa and glossy purple vetch is from October to November each year. During this period, the native grassland species are in the period of withering and falling. Planting during this period can provide sufficient planting space and soil nutrients for white clover, alfalfa and glossy purple vetch, and try to avoid the impact of species competition on the growth and development of green manure.

[0023] When sowing, choose areas in the grassland with fertile soil, sufficient sunlight, good water retention, and smooth drainage to avoid waterlogging; before sowing, maintain the pH of the sowing area at 5.5-7.0. It can be regulated by applying chemical substances such as lime. On the one hand, regulation can provide suitable soil physical and chemical factors such as pH for the growth of green manure, and is beneficial to improve soil structure, promote the formation of soil aggregates, and protect soil organic carbon; on the other hand, this pH range is conducive to microbial activity, which can promote rapid nitrogen fixation by nitrogen-fixing bacteria, achieving the effect of nitrogen fixation and carbon promotion.

[0024] White clover, Medicago truncatula and Vetch are sown by broadcasting, with a sowing depth of 0.5 to 2 cm. The no-till broadcast sowing method adopted by the present invention can effectively prevent soil disturbance, damage to soil structure and the formation of soil aggregates, so as to ensure the soil carbon fixation effect and achieve the purpose of carbon sink. After sowing, the sowing area can be lightly compacted by foot or light roller to ensure that the seeds are in full contact with the soil; especially for plants with larger seeds such as Vetch, special attention should be paid to ensure that they have good contact with the soil to avoid affecting their germination.

[0025] Furthermore, before sowing, the seeds of white clover, Medicago truncatula and Vetch glabra are pretreated by soaking in warm water, which can break the dormancy period of the seeds and promote germination. During soaking, the water temperature is 25-30°C and the soaking time is 6-8 hours. Under this condition, the germination rate of the seeds is relatively high.

[0026] In addition, the present invention further comprises uniformly mixing the pretreated seeds with a liquid inoculum of nitrogen-fixing bacteria. Optionally, the nitrogen-fixing bacteria is rhizobium; after mixing, ensure that the surface of each seed is covered with the liquid inoculum of rhizobium, and after inoculation, take out the seeds and dry them in the shade until the seeds are no longer adhered to each other.

[0027] Water continuously every day within 1 to 2 weeks after sowing to ensure that the soil is adequately hydrated and remains moist, providing a material basis for seed germination. Subsequently, water regularly for 6 to 9 days to keep the soil moisture content at 50% to 70%. Under this condition, on the one hand, it can promote the growth and development of green manure plants and increase plant production; on the other hand, it can help increase soil organic carbon by increasing soil moisture content, which is a limiting factor for soil organic carbon, and reduce soil carbon emissions in the form of CO2, further promoting soil carbon sequestration capacity, increasing grassland soil carbon sequestration, and enhancing soil carbon sink function.

[0028] During the growth of white clover, lucerne and glossy vetch, it is necessary to regularly check the growth of grass seeds in the sowing area and record the data, monitor the health of the plants, and deal with diseases and pests in time if any to avoid affecting the growth of the plants.

[0029] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0030] Example 1

[0031] This embodiment provides a method for fixing nitrogen and promoting carbon in grassland, which comprises:

[0032] S1. Selection of nitrogen-fixing plants:

[0033] We purchase certified white clover, alfalfa and glossy vetch seeds, which are of excellent variety and high purity, ensuring that the seed germination rate is over 90%.

[0034] S2. Soil preparation:

[0035] Choose an area in the grassland with fertile soil, plenty of sunlight, good water retention, and smooth drainage to avoid waterlogging for sowing; water the soil appropriately before sowing to keep it moist, and maintain the pH between 5.5 and 7.0 by applying chemicals such as lime.

[0036] S3. Seed weighing and pretreatment:

[0037] According to the size of the grassland, weigh 10g / m of white clover seeds. 2 , Alfalfa seeds 5g / m 2 , Vetch seeds 5g / m 2 . Soak the seeds in 30℃ warm water for 7 hours before sowing to break the seed dormancy and promote germination.

[0038] S4. Inoculation of nitrogen-fixing bacteria:

[0039] Take out the pretreated seeds, mix them with the purchased rhizobium liquid inoculant, gently stir the seeds to ensure that the surface of each seed is covered with the rhizobium inoculant, take out the seeds 5 minutes after inoculation, and dry the seeds in the shade until they are no longer sticky to each other.

[0040] S5. Seed sowing:

[0041] The inoculated seeds were sown within 24 hours. The seeds were sown in the evening of early November using the no-till broadcast method to ensure that the seeds were evenly spread over the sowing area, with a sowing depth of about 1 cm. After sowing, the sowing area was lightly compacted by foot to ensure that the seeds were in full contact with the soil.

[0042] S6. Moisture management:

[0043] After sowing the seeds, water the grass in the evening for a week to ensure that the soil is adequately hydrated and remains moist. After that, according to the weather conditions, consider the germination of seeds and the growth needs of plants, plan not to water in the rainy season, but to water in the dry season. The watering interval is once every 7 days, and the amount of water used should ensure that the soil moisture content is 50% to 70%.

[0044] S7. Evaluation and maintenance:

[0045] Regularly check the growth of green manure plants in the sowing area, monitor the health of the plants, and promptly deal with any diseases and pests. Regularly record the plant height, coverage, and density of white clover, alfalfa, and glossy purple vetch, as well as the soil moisture content and pH. If the emergence rate and survival rate of white clover, alfalfa, and glossy purple vetch are low, reseeding should be carried out at the appropriate time.

[0046] Example 2

[0047] This embodiment provides a method for fixing nitrogen and promoting carbon in grassland, which comprises:

[0048] S1. Selection of nitrogen-fixing plants:

[0049] We purchase certified white clover, alfalfa and glossy vetch seeds, which are of excellent variety and high purity, ensuring that the seed germination rate is over 90%.

[0050] S2. Soil preparation:

[0051] Choose an area in the grassland with fertile soil, plenty of sunlight, good water retention, and smooth drainage to avoid waterlogging for sowing; water the soil appropriately before sowing to keep it moist, and maintain the pH between 5.5 and 7.0 by applying chemicals such as lime.

[0052] S3. Seed weighing and pretreatment:

[0053] According to the size of the grassland, weigh 15g / m of white clover seeds. 2 , Alfalfa seeds 8g / m 2 , Vicia glabra seeds 6g / m 2. Soak the seeds in 25℃ warm water for 8 hours before sowing to break the seed dormancy and promote germination.

[0054] S4. Inoculation of nitrogen-fixing bacteria:

[0055] Take out the pretreated seeds, mix them with the purchased rhizobium liquid inoculant, gently stir the seeds to ensure that the surface of each seed is covered with the rhizobium inoculant, take out the seeds 5 minutes after inoculation, and dry the seeds in the shade until they are no longer sticky to each other.

[0056] S5. Seed sowing:

[0057] The inoculated seeds are sown within 24 hours. The seeds are sown in the evening of late October using the no-till broadcast method to ensure that the seeds are evenly spread over the sowing area, with a sowing depth of about 1.5 cm. After sowing, the sowing area is lightly compacted by foot to ensure that the seeds are in full contact with the soil.

[0058] S6. Moisture management:

[0059] After sowing the seeds, water the grass in the evening for a week to ensure that the soil is adequately hydrated and remains moist. After that, according to the weather conditions, consider the germination of seeds and the growth needs of plants, plan not to water in the rainy season, but to water in the dry season. The watering interval is once every 8 days, and the amount of water used ensures that the soil moisture content is 50% to 70%.

[0060] S7. Evaluation and maintenance:

[0061] Regularly check the growth of green manure plants in the sowing area, monitor the health of the plants, and promptly deal with any diseases and pests. Regularly record the plant height, coverage, and density of white clover, alfalfa, and glossy purple vetch, as well as the soil moisture content and pH. If the emergence rate and survival rate of white clover, alfalfa, and glossy purple vetch are low, reseeding should be carried out at the appropriate time.

[0062] Example 3

[0063] This embodiment provides a method for fixing nitrogen and promoting carbon in grassland, which comprises:

[0064] S1. Selection of nitrogen-fixing plants:

[0065] We purchase certified white clover, alfalfa and glossy vetch seeds, which are of excellent variety and high purity, ensuring that the seed germination rate is over 90%.

[0066] S2. Soil preparation:

[0067] Choose an area in the grassland with fertile soil, plenty of sunlight, good water retention, and smooth drainage to avoid waterlogging for sowing; water the soil appropriately before sowing to keep it moist, and maintain the pH between 5.5 and 7.0 by applying chemicals such as lime.

[0068] S3. Seed weighing and pretreatment:

[0069] According to the size of the grassland, weigh 10g / m of white clover seeds. 2 , Alfalfa seeds 5g / m 2 , Vetch seeds 8g / m 2 . Soak the seeds in 30℃ warm water for 6 hours before sowing to break the seed dormancy and promote germination.

[0070] S4. Inoculation of nitrogen-fixing bacteria:

[0071] Take out the pretreated seeds, mix them with the purchased rhizobium liquid inoculant, gently stir the seeds to ensure that the surface of each seed is covered with the rhizobium inoculant, take out the seeds 5 minutes after inoculation, and dry the seeds in the shade until they are no longer sticky to each other.

[0072] S5. Seed sowing:

[0073] The inoculated seeds were sown within 24 hours. The seeds were sown in the evening of early November using the no-till broadcast method to ensure that the seeds were evenly spread over the sowing area, with a sowing depth of about 1 cm. After sowing, the sowing area was lightly compacted by foot to ensure that the seeds were in full contact with the soil.

[0074] S6. Moisture management:

[0075] After sowing the seeds, water the grass in the evening for a week to ensure that the soil is adequately hydrated and remains moist. After that, according to the weather conditions, consider the germination of seeds and the growth needs of plants, plan not to water in the rainy season, but to water in the dry season. The watering interval is once every 6 days, and the amount of water used ensures that the soil moisture content is 50% to 70%.

[0076] S7. Evaluation and maintenance:

[0077] Regularly check the growth of green manure plants in the sowing area, monitor the health of the plants, and promptly deal with any diseases and pests. Regularly record the plant height, coverage, and density of white clover, alfalfa, and glossy purple vetch, as well as the soil moisture content and pH. If the emergence rate and survival rate of white clover, alfalfa, and glossy purple vetch are low, reseeding should be carried out at the appropriate time.

[0078] Comparative Example 1

[0079] This comparative example provides a method for fixing nitrogen and promoting carbon in grassland, and the specific method is basically the same as that in Example 1, except that Medicago truncatula and Vetch glabra are not sown, and only Trifolium repens is sown, but the total sowing amount of seeds is kept unchanged.

[0080] Comparative Example 2

[0081] This comparative example provides a method for fixing nitrogen and promoting carbon in grassland, and the specific method is basically the same as that in Example 1, except that white clover and alfalfa are not sown, and only glossy purple vetch is sown, but the total sowing amount of seeds is kept unchanged.

[0082] Comparative Example 3

[0083] This comparative example provides a method for fixing nitrogen and promoting carbon in grassland, and the specific method is basically the same as that in Example 1, except that white clover and glossy vetch are not sown, and only alfalfa is sown, but the total sowing amount of seeds is kept unchanged.

[0084] Comparative Example 4

[0085] This comparative example provides a method for fixing nitrogen and promoting carbon in grassland, and the specific method is basically the same as that in Example 1, except that alfalfa is not sown, and only white clover and glossy purple vetch are sown, but the total sowing amount of seeds is kept unchanged.

[0086] Comparative Example 5

[0087] This comparative example provides a method for fixing nitrogen and promoting carbon in grassland, and the specific method is basically the same as that in Example 1, except that white clover and alfalfa are not sown, but the total sowing amount of seeds is kept unchanged.

[0088] Comparative Example 6

[0089] This comparative example provides a method for fixing nitrogen and promoting carbon in grassland, and the specific method is basically the same as that in Example 1, except that white clover is not sown, and only alfalfa and glossy purple vetch are sown, but the total sowing amount of seeds is kept unchanged.

[0090] Comparative Example 7

[0091] This comparative example provides a method for fixing nitrogen and promoting carbon in grassland, and the specific method is basically the same as that in Example 1, except that no water management is applied except for watering for one week after sowing.

[0092] Comparative Example 8

[0093] This comparative example provides a method for fixing nitrogen and promoting carbon in grassland, and the specific method is basically the same as that in Example 1, except that the sowing amount of white clover, Medicago sativa, and Vetch is twice as much as the original amount.

[0094] Comparative Example 9

[0095] This comparative example provides a method for fixing nitrogen and promoting carbon in grassland, and the specific method is basically the same as that in Example 1, except that the sowing amount of white clover, Medicago sativa, and Vetch is half of the original amount.

[0096] Test example

[0097] The methods for nitrogen fixation and carbon promotion in grassland provided in Examples 1 to 3 and Comparative Examples 1 to 9 were adopted to carry out sowing in respective experimental plots, and the experimental plots without planting green manure were used as blank examples. After one year of planting and cultivation, the surface soil of the experimental plots was sampled, and data of the samples were measured to evaluate the annual nitrogen and carbon fixation effects. The measurement results are shown in Table 1.

[0098] Table 1 Comparison of nitrogen fixation and carbon promotion effects of grassland water and fertilizer management

[0099]

[0100] As can be seen from Table 1, after adopting the methods of Examples 1 to 3 of the present invention, the total nitrogen in the soil increased from 1.23 g / kg to 1.42 to 4.62 g / kg. In comparison, the total nitrogen showed a significant upward trend. At the same time, the soil organic carbon increased from 38.5 g / kg to 43.4 to 76.0 g / kg. This shows that the nitrogen fixation and carbon promotion effects are significant, and the carbon sink function of grassland soil can be significantly enhanced.

[0101] In contrast, Comparative Examples 1, 2, and 3 planted white clover, purple vetch, and alfalfa, respectively, and only sowed one plant. The total nitrogen and soil organic carbon content did show a significant improvement compared to before the application of this technology, but there is still a lot of room for improvement compared to Example 1, and the overall effect of nitrogen fixation and carbon promotion is relatively general. Among them, it can be seen from Comparative Example 2 that the emergence rate of purple vetch is low due to species competition. However, when the emergence rate is low, its nitrogen and carbon fixation capacity exceeds that of white clover and alfalfa, proving its irreplaceable value.

[0102] Comparative Examples 4 to 6 tried two kinds of green manure mixed sowing respectively. First of all, it can be seen that mixed sowing has a significant improvement in nitrogen fixation and carbon fixation capacity compared with single green manure planting. The total nitrogen in the soil rose to 3.72-3.98g / kg, and the soil organic carbon increased to 55.3-60.8g / kg. In Comparative Example 4, the green manure combination of white clover + light-leaf purple flower vetch was adopted, and the seed emergence rate was still low. Both green manures were affected by species competition, but they still showed relatively good nitrogen and carbon fixation effects in the case of low emergence rate, indicating that this combination has great development potential. Comparative Examples 5 and 6 used purple alfalfa to mix with white clover and light-leaf purple flower vetch respectively. It can be seen that the seed emergence rate problem has been significantly improved. The seed emergence rate of the two combinations reached more than 93%, which led to the increase of total nitrogen and soil organic carbon. Based on this, the present invention mixes three green manures, namely white clover, glossy purple vetch and purple alfalfa, and utilizes the regulating effect of purple alfalfa root secretions on the soil microenvironment to improve the seed germination rate, so as to achieve the best effect of Examples 1 to 3 of the present application.

[0103] Comparative Example 7 does not perform water management on the basis of Example 1. It can be seen that under the condition of water shortage, the total nitrogen and soil organic carbon content both decrease to a certain extent. Comparative Examples 8-9 increase and decrease the seed sowing amount respectively. Low or high planting density will significantly affect the nitrogen fixation and carbon promotion effect. At the same time, considering the economic cost and the nitrogen fixation and carbon promotion effect, the planting density used in Examples 1-3 of the present invention is the best.

[0104] In summary, the present invention provides a method for promoting carbon fixation in grasslands. Based on the ecological characteristics of the grassland itself, perennial legumes white clover and Medicago sativa were selected, and the annual legume Vetch is sown in the grassland. Perennial legumes have a long life span and can provide litter for many times, promoting the turnover of plant carbon to soil carbon. Vetch can effectively improve the rhizosphere microbial community, promote the growth and reproduction of nitrogen-fixing bacteria, and improve nitrogen fixation efficiency. This combination can complement and promote each other. At the same time, these three plants are also plants with excellent nitrogen fixation effects, which can quickly replenish the effective nitrogen required by the soil and provide the nutrients required for plant growth, thereby increasing the production of grassland plants, and then achieving the purpose of increasing soil carbon reserves and enhancing grassland soil carbon sinks. The method is simple to operate, low cost, and has good promotion value.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for fixing nitrogen and promoting carbon in grassland, characterized in that: include: Plant white clover, lucerne and glossy-leaved vetch in the grassland.

2. The method for nitrogen fixation and carbon promotion in grassland according to claim 1, characterized in that: The sowing rate ratio of the white clover, the purple clover and the glossy purple vetch is 1:0.3-0.6:0.3-0.

6.

3. The method for nitrogen fixation and carbon promotion in grassland according to claim 2, characterized in that: The planting density of the white clover is 10-15 g / m 2 .

4. The method for nitrogen fixation and carbon promotion in grassland according to claim 2, characterized in that: The planting density of the purple lucerne and the light-leaved purple vetch is 5 to 8 g / m 2 .

5. The method for nitrogen fixation and carbon promotion in grassland according to claim 3, characterized in that: The sowing time of the white clover, the purple lucerne and the glossy purple vetch is from October to November every year.

6. The method for nitrogen fixation and carbon promotion in grassland according to claim 1, characterized in that: Select an area in the grassland with fertile soil, sufficient sunlight, good water retention, and smooth drainage to avoid waterlogging for sowing; before sowing, maintain the pH of the sowing area at 5.5-7.

0.

7. The method for nitrogen fixation and carbon promotion in grassland according to claim 1, characterized in that: The white clover, the purple lucerne and the glossy-leaved purple vetch are sown in a broadcasting manner, with a sowing depth of 0.5 to 2 cm.

8. The method for fixing nitrogen and promoting carbon in grassland according to claim 1, characterized in that: Before sowing, the seeds of the white clover, the purple lucerne and the glossy-leaved purple vetch are pretreated by soaking them in warm water; during the soaking, the water temperature is 25-30° C. and the soaking time is 6-8 hours.

9. The method for fixing nitrogen and promoting carbon in grassland according to claim 8, characterized in that: The pretreated seeds are uniformly mixed with a liquid inoculum of nitrogen-fixing bacteria.

10. The method for nitrogen fixation and carbon promotion in grassland according to claim 1, characterized in that: Water continuously every day for 1 to 2 weeks after sowing. Then, water regularly every 6 to 9 days to keep the soil moisture content at 50% to 70%.

Images