Method for quickly and stably increasing organic carbon content of paddy field soil by using rye green manure

Abstract

The present application relates to the field of rice field soil fertilization and agricultural carbon fixation and emission reduction technology, and discloses a method for rapidly and stably increasing the organic carbon content of rice field soil by using ryegrass green manure.The method selects a winter fallow field for planting a season of single-season late rice as a planting field, uses grass-type annual ryegrass as green manure raw material, adjusts the application mode by pretreating the fresh grass of ryegrass combined with the soil moisture condition of the planting field, carries out the conventional management of flooding after applying the fresh grass of ryegrass alone or in combination with conventional chemical fertilizers, completes the nutrient management during the rice seeding and transplanting period, and completes the application of ryegrass and the planting of rice for consecutive years, stops the input of exogenous fertilizer, and maintains the conventional rice planting and flooding management.The method can rapidly and stably increase the organic carbon content of rice field soil, takes into account the stable yield of rice and long-term soil fertilization, realizes the continuous and stable carbon pool of rice field soil, and provides reliable technical support for the efficient use of green manure and the improvement of farmland quality in the single-season rice area in the south.

Description

Technical Field

[0001] This invention belongs to the field of paddy field soil fertilization and agricultural carbon sequestration and emission reduction technology, specifically involving a method for rapidly and stably increasing the organic carbon content of paddy field soil using ryegrass green manure. Background Technology

[0002] Soil organic carbon in paddy fields is a core indicator of basic soil fertility, and its content level directly determines the rice production potential. The carbon pool in paddy fields is also an important carbon sink in the agricultural ecosystem, and its dynamic balance plays a significant regulatory role in the global carbon and nitrogen cycle and the sustainable development of agricultural ecology.

[0003] Currently, chemical fertilizers remain the primary source of nutrient input, and excessive application is prevalent in production. This not only leads to low fertilizer utilization rates but also easily causes problems such as soil acidification and compaction in paddy fields, decreased organic matter content, and accelerated nutrient loss, while also increasing the risk of greenhouse gas emissions from farmland. In existing production, commercial organic fertilizers and green manure are gradually being used to improve paddy field fertility. However, commercial organic fertilizers pose a risk of secondary pollution, and the application technology of returning green manure to the field still needs improvement.

[0004] Existing research on green manure return to the field mainly focuses on the cumulative impact of continuous return on paddy soil fertility. Research on the continuous regulatory effect and long-term sequestration mechanism of green manure on paddy soil organic carbon pool after the end of green manure return is still relatively limited. There is no unified consensus on the quantitative technology of green manure return to the field to increase the organic carbon content of paddy soil, making it difficult to fully realize the application value of green manure in paddy soil fertility improvement and carbon sequestration and emission reduction. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present invention provide a method for rapidly and stably increasing the soil organic carbon content of paddy fields using ryegrass green manure. This method solves the problems in the prior art where returning green manure to the field lacks a systematic quantitative technology for the long-term and stable increase of soil organic carbon in paddy fields, cannot guarantee the continuous stability of the soil carbon pool after the green manure application is stopped, and is difficult to balance the reduction of fertilizer and increase of efficiency in paddy fields with the long-term preservation of soil organic carbon.

[0006] The technical solution of this invention: A method for rapidly and stably increasing the organic carbon content of paddy field soil using ryegrass green manure, comprising the following steps:

[0007] (S01) Select fallow fields that are used for planting a single season of late rice once a year as planting fields;

[0008] (S02) Select green manure as pasture-type annual ryegrass, take fresh grass from the upper part of the ryegrass plant during the flowering period, and perform low-temperature enzymatic hydrolysis-anaerobic pre-decomposition compound pretreatment on the fresh ryegrass to obtain pretreated ryegrass material.

[0009] (S03) In mid-April each year, adjust the application method according to the soil moisture of the 0-10cm layer of the planting field in step (S01). When the soil moisture is 60-70% of the field water holding capacity, apply the pretreated ryegrass material in step (S02) into the cultivated layer of the planting field in a layered gradient compaction method; or apply 30t / ha-60t / ha of pretreated ryegrass material to the planting field in step (S01) and apply conventional fertilizer at the same time.

[0010] (S04) After completing the pre-treatment of ryegrass material by applying it alone or in combination with chemical fertilizer, the rice planting field described in step (S03) is subjected to dynamic flooding management throughout the entire growth period of rice.

[0011] (S05) In early May each year, indica-japonica hybrid late rice is sown, and in mid-June, the late rice seedlings with 2 to 4 tillers and relatively uniform growth are transplanted to the planting field described in step (S04);

[0012] (S06) Following steps (S03) to (S05), ryegrass material application and rice planting management are carried out continuously for 6 to 8 years. After that, the application of ryegrass material and chemical fertilizers is stopped, and a 2-year carbon stabilization period is entered. Ryegrass is used as green manure. The decomposition rhythm of organic matter is regulated by a combination of low-temperature enzymatic hydrolysis and anaerobic pre-decomposition. Combined with soil moisture, stratified gradient application is adopted to optimize the distribution of carbon in different soil layers. Nutrient release is coordinated by applying conventional fertilizers alone or in combination. Topdressing with decomposed liquid during the rice growth period balances supply and demand. After long-term continuous application and cessation, no-till carbon stabilization is achieved in conjunction with soil microbial carbon and nitrogen metabolism, so as to realize the rapid accumulation and long-term stability of organic carbon in paddy field soil.

[0013] Preferably, the soil in the planting field in step (S01) is paddy soil developed from red soil and yellow clay soil.

[0014] Preferably, the planting field in step (S01) is located in the mid-subtropical monsoon climate zone, where the average annual temperature is 17.9℃, the average annual sunshine duration is 1700h, and the average annual precipitation is 1500mm. This climate provides suitable light and heat conditions for ryegrass growth and promotes appropriate soil microbial activity, ensuring efficient conversion of organic matter into soil organic carbon during ryegrass decomposition and maintaining the stability of carbon sequestration-related biochemical reactions.

[0015] Preferably, in step (S01), the basic fertility indicators of the soil surface layer (0-10cm) are: pH 5.5-6.5, organic matter content 23.0-25.0 g / kg, total nitrogen content 1.40-1.45 g / kg, available nitrogen 115-125 mg / kg, available phosphorus 6.5-7.5 mg / kg, and available potassium 30-35 mg / kg. More preferably, in step (S01), the basic fertility indicators of the soil surface layer (0-10cm) are: pH 5.7-6.3, organic matter content 23.5-24.5 g / kg, total nitrogen content 1.42-1.44 g / kg, available nitrogen 117-123 mg / kg, available phosphorus 6.7-7.3 mg / kg, and available potassium 31-34 mg / kg. More preferably, in step (S01), the basic fertility indicators of the soil surface layer (0-10cm) are: pH 5.9, organic matter content 24.1g / kg, total nitrogen content 1.43g / kg, available nitrogen 121mg / kg, available phosphorus 6.9mg / kg, and available potassium 32mg / kg. Initial soil pH, organic matter, and other parameters directly affect the microbial community structure and enzyme activity. A suitable fertility range allows for optimal binding of nutrients released by ryegrass with soil colloids, reducing organic carbon loss through water and ensuring efficient accumulation of organic carbon in the soil.

[0016] Preferably, the low-temperature enzymatic hydrolysis-anaerobic pre-decomposition composite pretreatment in step (S02) is as follows: first, fresh ryegrass is chopped into 2-5cm pieces, then a composite enzyme preparation is evenly sprayed onto the chopped material and mixed thoroughly, then sodium lignosulfonate solution is evenly sprayed onto the enzymatically hydrolyzed material and mixed thoroughly, and finally, the material is sealed and compacted to control the oxygen content inside the pile to ≤1%.

[0017] Preferably, in step (S02), the mass ratio of cellulase to xylanase in the composite enzyme preparation is 1:0.6-1, the temperature of the enzymatic hydrolysis pile is controlled at 25-30℃ and the humidity at 60-65%, the enzymatic hydrolysis treatment lasts for 48-72 hours, and the temperature of the anaerobic pre-decomposition pile is controlled at 28-32℃, with anaerobic pre-decomposition lasting for 24-36 hours. More preferably, in step (S02), the mass ratio of cellulase to xylanase in the composite enzyme preparation is 1:0.7-0.9, the temperature of the enzymatic hydrolysis pile is controlled at 27-29℃ and the humidity at 62-64%, the enzymatic hydrolysis treatment lasts for 54-66 hours, and the temperature of the anaerobic pre-decomposition pile is controlled at 29-31℃, with anaerobic pre-decomposition lasting for 28-32 hours. More preferably, in step (S02), the mass ratio of cellulase to xylanase in the compound enzyme preparation is 1:0.8, the temperature of the enzymatic hydrolysis pile is controlled at 28°C and the humidity at 63%, the enzymatic hydrolysis treatment is carried out for 60 hours, and the temperature of the anaerobic pre-decomposition pile is controlled at 30°C, the anaerobic pre-decomposition is carried out for 30 hours. The specific ratio of cellulase to xylanase can directionally decompose the crude fiber of ryegrass. Suitable temperature, humidity and time can promote the generation of humic precursors. At the same time, the anaerobic environment inhibits the excessive mineralization of organic carbon by aerobic microorganisms and improves carbon conversion efficiency. When the mass ratio is lower than 1:0.6, the xylanase content is insufficient and cannot effectively decompose the hemicellulose in ryegrass, resulting in a low crude fiber decomposition rate and a small amount of humic precursors generated. When the mass ratio is higher than 1:1, the cellulase is excessive, which will lead to excessive decomposition of organic matter in ryegrass, increased loss of organic carbon mineralization, and decreased carbon fixation efficiency. When the optimal ratio is 1:0.8, the crude fiber decomposition rate can reach more than 85%, and there is no excessive mineralization of organic matter, and the amount of humic precursors generated is optimal.

[0018] Preferably, in step (S02), the fresh basis moisture content of the pretreated ryegrass material is 88.0%–89.0%, and the N content is 2.00–2.10 g / kg, the P2O5 content is 0.90–1.00 g / kg, and the K2O content is 2.90–3.00 g / kg. More preferably, in step (S02), the fresh basis moisture content of the pretreated ryegrass material is 88.5%–88.8%, and the N content is 2.03–2.09 g / kg, the P2O5 content is 0.93–0.97 g / kg, and the K2O content is 2.92–2.97 g / kg. Even more preferably, in step (S02), the fresh basis moisture content of the pretreated ryegrass material is 88.7%, and the N content is 2.06 g / kg, the P2O5 content is 0.96 g / kg, and the K2O content is 2.95 g / kg. A suitable moisture content can maintain the water environment required for microbial metabolism, and a stable ratio of nutrients such as N and P2O5 can balance the carbon and nitrogen metabolism of microorganisms, avoid incomplete decomposition of organic matter due to nutrient imbalance, and ensure the continuous input of organic carbon into the soil carbon pool.

[0019] Preferably, in step (S02), the spraying amount of the compound enzyme preparation is 0.05–0.08% of the weight of fresh ryegrass, with cellulase activity of 5000–6000 U / g and xylanase activity of 3000–4000 U / g. More preferably, in step (S02), the spraying amount of the compound enzyme preparation is 0.06–0.08% of the weight of fresh ryegrass, with cellulase activity of 5200–5600 U / g and xylanase activity of 3300–3800 U / g. Even more preferably, in step (S02), the spraying amount of the compound enzyme preparation is 0.07% of the weight of fresh ryegrass, with cellulase activity of 5500 U / g and xylanase activity of 3600 U / g. Enzyme activity levels must meet standards to ensure the intensity of the enzymatic hydrolysis reaction. A reasonable application rate can prevent excessive enzymes from causing over-decomposition of organic matter or insufficient enzymes from leading to incomplete decomposition. This ensures efficient conversion of recalcitrant components in ryegrass, providing a sufficient source of nutrients for soil organic carbon accumulation. When the application rate is below 0.05%, the enzymatic hydrolysis reaction is insufficient, resulting in incomplete decomposition of ryegrass. When the application rate is above 0.08%, excessive enzymes increase costs and can cause microbial community imbalance, thus reducing organic carbon conversion efficiency. The optimal application rate of 0.07% ensures a sufficient enzymatic hydrolysis reaction, controllable costs, and a stable microbial community structure.

[0020] Preferably, in step (S02), the mass concentration of the sodium lignosulfonate solution is 0.01–0.05%, and the spraying amount is 1–4% of the mass of fresh ryegrass. More preferably, in step (S02), the mass concentration of the sodium lignosulfonate solution is 0.02–0.04%, and the spraying amount is 1.5–3.5% of the mass of fresh ryegrass. Even more preferably, in step (S02), the mass concentration of the sodium lignosulfonate solution is 0.03%, and the spraying amount is 3% of the mass of fresh ryegrass. Sodium lignosulfonate can form a stable complex with ryegrass organic matter, inhibit the decomposition of organic carbon by enzymes such as urease, improve soil colloidal stability, promote the binding of organic carbon with mineral particles, and enhance the long-term stability of the soil carbon pool.

[0021] Preferably, in step (S03), when the soil moisture is 40-59% of the field water holding capacity, the soil is first thoroughly irrigated to 60-70% of the field water holding capacity. After the soil is dry, the soil is then applied to the topsoil layer of the planting field using a layered gradient compaction method.

[0022] Preferably, in step (S03), the stratified gradient compaction is performed as follows: by weight, 50%–70% of the pretreated ryegrass material is compacted to a soil layer of 5–10 cm, and 30%–50% of the pretreated ryegrass material is compacted to a soil layer of 0–5 cm. More preferably, in step (S03), the stratified gradient compaction is performed as follows: by weight, 55%–65% of the pretreated ryegrass material is compacted to a soil layer of 5–10 cm, and 35%–45% of the pretreated ryegrass material is compacted to a soil layer of 0–5 cm. Even more preferably, in step (S03), the stratified gradient compaction is performed as follows: by weight, 60% of the pretreated ryegrass material is compacted to a soil layer of 5–10 cm, and 40% of the pretreated ryegrass material is compacted to a soil layer of 0–5 cm. The soil layer of 5-10cm has low microbial activity, and turning over more material can reduce the rapid mineralization of organic carbon. The soil layer of 0-5cm has active microorganisms, and a small amount of material can decompose quickly to provide fertilizer, which takes into account both rice growth and long-term organic carbon sequestration, thus optimizing carbon allocation efficiency.

[0023] Preferably, the total application rate of pretreated ryegrass material in step (S03) is 30–120 t / ha. More preferably, the total application rate of pretreated ryegrass material in step (S03) is 60–90 t / ha. This ensures that the amount of organic matter input meets the soil carbon pool accumulation requirements, while balancing the soil carbon input and nutrient release rates, avoiding excessive application that leads to poor soil aeration or insufficient application that leads to slow carbon accumulation.

[0024] Preferably, the amount of conventional fertilizer applied in step (S03) is 40% to 100% of the conventional amount. More preferably, the amount of conventional fertilizer applied in step (S03) is 60% to 80% of the conventional amount. This coordinates the release rhythm of green manure and chemical fertilizer, adapts to the nutrient requirements of rice throughout its entire growth period, reduces soil acidification caused by excessive chemical fertilizer, and enhances the carbon sequestration capacity of microorganisms through the synergistic effect of organic and inorganic fertilizers.

[0025] Preferably, in step (S03), the application rate of conventional fertilizer in N is 200-220 kg / ha, the application rate of P2O5 is 55-65 kg / ha, and the application rate of K2O is 120-125 kg / ha. More preferably, in step (S03), the application rate of conventional fertilizer in N is 205-215 kg / ha, the application rate of P2O5 is 57-62 kg / ha, and the application rate of K2O is 121-123 kg / ha. Even more preferably, in step (S03), the application rate of conventional fertilizer in N is 210 kg / ha, the application rate of P2O5 is 60 kg / ha, and the application rate of K2O is 121.5 kg / ha. The fertilizer nutrients and the nutrients released by ryegrass form a synergistic effect, which can not only meet the needs of rice for macronutrients, but also provide balanced nutrition for microorganisms that decompose organic matter, avoid nutrient imbalance that inhibits carbon conversion, and ensure efficient sequestration of organic carbon.

[0026] Preferably, in step (S03), the pretreated ryegrass material is applied to the topsoil of the planting field by returning it to the soil in a different location. This avoids uneven nutrient consumption caused by continuous cropping in the local area, while simultaneously providing a concentrated input of pure organic matter, reducing the interference of local soil impurities on the microbial decomposition process, and ensuring stable organic carbon conversion efficiency.

[0027] Preferably, the dynamic management of flooding throughout the rice growth period in step (S04) involves maintaining a shallow water layer of 3-5 cm for 1-15 days after ryegrass is returned to the field, maintaining a deep water layer of 8-10 cm for 16-30 days after return, maintaining a shallow water layer of 3-5 cm during the rice tillering stage, and maintaining a stable water layer of 5-8 cm from the jointing stage to maturity. The water layer thickness at different stages regulates the soil redox potential; the shallow water layer promotes microbial decomposition and nutrient supply, while the deep water layer inhibits the loss of organic carbon mineralization, thus adapting to the ryegrass decomposition rhythm and the rice growth requirements, balancing nutrient supply and carbon sequestration.

[0028] Preferably, in step (S04), the dynamic flooding management involves separating each planting plot with hard embankments covered by plastic film for independent irrigation and drainage. This controls the stability of the water layer in each plot, prevents cross-contamination of nutrients and organic matter between plots with the water flow, ensures that microbial activity is consistent with the carbon conversion environment, and guarantees the repeatability of organic carbon accumulation.

[0029] Preferably, in step (S05), during the tillering and jointing stages of rice, soil samples from the 0-10cm soil layer of the planting field are collected using the S-shaped 5-point sampling method to determine the available nitrogen content. When the available nitrogen content is below 90mg / kg, ryegrass decomposed liquid is applied as a top dressing, and no other chemical fertilizers are applied during the same period.

[0030] Preferably, in step (S05), the late-season indica-japonica hybrid rice variety is Yongyou 9, and the transplanting density is 240,000 to 260,000 clumps / ha. More preferably, in step (S05), the transplanting density is 245,000 to 255,000 clumps / ha. Even more preferably, in step (S05), the transplanting density is 250,000 clumps / ha. This variety's growth characteristics are well-suited to the nutrient release rhythm of ryegrass, and a reasonable density can balance the nutrient absorption of rice with the competition for carbon and nitrogen from microorganisms, avoiding the waste of organic matter or a decrease in carbon sequestration efficiency caused by improper density.

[0031] Preferably, in step (S05), the ryegrass decomposition liquid is prepared by decomposing the pretreated ryegrass material obtained in step (S02) with water at a mass ratio of 1:13-17 for 10-20 days and then filtering. The application rate for each topdressing is 1500-2000 L / ha. More preferably, in step (S05), the ryegrass decomposition liquid is prepared by decomposing the pretreated ryegrass material obtained in step (S02) with water at a mass ratio of 1:14-16 for 13-17 days and then filtering. The application rate for each topdressing is 1600-1900 L / ha. Even more preferably, in step (S05), the ryegrass decomposition liquid is prepared by decomposing the pretreated ryegrass material obtained in step (S02) with water at a mass ratio of 1:15 for 15 days and then filtering. The application rate for each topdressing is 1750 L / ha. The specific solid-liquid ratio and decomposition time make the decomposition liquid rich in readily available carbon and nitrogen. The topdressing amount is suitable for the nutrient requirements of rice during the tillering and jointing stages, supplementing readily available nutrients while increasing organic carbon input, replacing chemical fertilizer topdressing and reducing carbon mineralization.

[0032] Preferably, in step (S05), the total nitrogen content of the ryegrass decomposition liquid is 0.8–1.2 g / L and the total carbon content is 15–20 g / L. More preferably, the total nitrogen content of the ryegrass decomposition liquid in step (S05) is 0.9–1.1 g / L and the total carbon content is 17–19 g / L. Even more preferably, the total nitrogen content of the ryegrass decomposition liquid in step (S05) is 1 g / L and the total carbon content is 18 g / L. A stable carbon-nitrogen ratio can match the absorption and metabolic needs of rice and microorganisms, avoiding excessive nitrogen leading to excessive decomposition of organic carbon by microorganisms, or excessive carbon causing nutrient imbalance, ensuring that the decomposition liquid can simultaneously provide fertilizer and accumulate carbon.

[0033] Preferably, in step (S06), during the carbon stabilization period, rice is planted conventionally. Except for the ryegrass decomposition solution, no chemical fertilizers or exogenous organic fertilizers are applied. After each rice harvest, the rice stubble is left in place without removal, and a full-cycle no-till management system is adopted. During the winter fallow period, a thin water layer of 1-2 cm is maintained and replenished to maintain water stability until drainage before the following year's rice planting. The full-cycle no-till management during the carbon stabilization period prohibits all soil disturbance activities such as tilling and rotary tillage; weeds are controlled by manual removal, and the use of herbicides is prohibited to avoid the impact of chemical agents on soil microorganisms and the organic carbon pool.

[0034] Compared with the prior art, the advantages of the present invention are as follows:

[0035] (1) The ryegrass of the present invention undergoes a combination of low-temperature enzymatic hydrolysis and anaerobic pre-decomposition pretreatment to decompose crude fiber and enrich humic precursors, inhibit excessive mineralization of organic carbon, improve the conversion efficiency of organic matter into soil stable organic carbon, and provide a sufficient material basis for carbon pool accumulation.

[0036] (2) This invention combines soil moisture with a layered gradient application method to adapt to the differences in microbial activity in different soil layers, so as to achieve rapid decomposition of organic matter in the upper layer to supply fertilizer and slow decomposition of carbon in the lower layer, thus balancing the nutrient requirements for rice growth and the long-term storage of soil organic carbon.

[0037] (3) The mode of applying ryegrass alone or in combination with conventional fertilizers in this invention coordinates the release rhythm of slow-acting and fast-acting nutrients, reduces the amount of fertilizer input, alleviates soil acidification, optimizes the structure and activity of microbial communities, and strengthens the microbial capacity to retain organic carbon.

[0038] (4) The present invention applies ryegrass decomposed liquid during the rice growing season to supplement quick-acting carbon and nitrogen nutrients to replace chemical fertilizer topdressing, avoids the accelerated carbon mineralization caused by excessive chemical fertilizer, and continuously inputs organic carbon to maintain the soil carbon and nitrogen metabolism balance.

[0039] (5) After the application of this invention is stopped, the rice stubble is retained and no-till management is implemented to reduce the disturbance of soil tillage to the carbon pool, maintain the adsorption and binding state of soil colloids and mineral particles on organic carbon, and ensure the long-term stability of the soil carbon pool.

[0040] (6) This invention improves the soil carbon pool management index, improves soil structure and fertility by pretreatment and application of nutrients and the synergistic effect of stopping application to stabilize carbon, thereby achieving the unity of rapid accumulation of organic carbon and sustainable development of paddy field ecosystem. Attached Figure Description

[0041] Figure 1 This is a comparison chart of soil organic carbon storage of the present invention. The vertical axis represents soil organic carbon storage in Mg / ha, and the horizontal axis represents the groups of each embodiment and comparative example. The corresponding data for each group are shown in Table 1. The error bars represent the standard deviation of three repeated experiments.

[0042] Figure 2 This is a comparison chart of carbon fixation rates of the present invention. The vertical axis represents the carbon fixation rate, and the unit is Mg ha. -1 yr -1 The horizontal axis represents the various embodiments and comparative example groups. Comparative example 1 has no carbon fixation rate, so there is no data. The corresponding data for each group are shown in Table 1.

[0043] Figure 3 This is a comparison chart of the annual carbon sequestration rate per unit weight of pretreated ryegrass according to the present invention. The vertical axis represents the carbon sequestration rate per unit weight, and the unit is kg ha. -1 yr -1 t -1 The horizontal axis represents the groups of each embodiment. The comparative example did not use green manure, so there is no data. The corresponding data for each group are shown in Table 1.

[0044] Figure 4This is a comparison chart of carbon pool management index of soil with no fertilizer treatment as reference soil in this invention. The vertical axis is the carbon pool management index in %, and the horizontal axis is the group of each embodiment and comparative example. The carbon pool management index of comparative example 1 is 100% baseline. The corresponding data for each group are shown in Table 2.

[0045] Figure 5 This is a comparison chart of carbon pool management index of soil with conventional fertilizer application treatment as reference. The vertical axis is the carbon pool management index in %, and the horizontal axis is the group of each embodiment and comparative example. The carbon pool management index of comparative example 2 is 100% baseline. The corresponding data for each group are shown in Table 2.

[0046] The experimental data in all the accompanying figures are the average of three repeated experiments, and the experimental conditions are consistent with the specific implementation method in the instruction manual. Detailed Implementation

[0047] To facilitate understanding of the present invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0048] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0049] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0050] A method for rapidly and stably increasing the organic carbon content of paddy field soil using ryegrass green manure includes the following steps.

[0051] (S01) Select a fallow field that grows a single late-season rice crop once a year as the planting field; the soil of the planting field in step (S01) is paddy soil developed from red loam and yellow clay soil; the planting field in step (S01) is located in the mid-subtropical monsoon climate zone, with an average annual temperature of 17.9℃, an average annual sunshine duration of 1700h, and an average annual precipitation of 1500mm; the basic fertility indicators of the 0-10cm topsoil layer in step (S01) are: pH 5.5-6.5, organic matter content 23.0-25.0g / kg, total nitrogen content 1.40-1.45g / kg, available nitrogen 115-125mg / kg, and available phosphorus 6.5-7.5mg / kg. Available potassium 30-35 mg / kg; in step (S01), the basic fertility indicators of the soil surface layer (0-10 cm) are: pH 5.7-6.3, organic matter content 23.5-24.5 g / kg, total nitrogen content 1.42-1.44 g / kg, available nitrogen 117-123 mg / kg, available phosphorus 6.7-7.3 mg / kg, available potassium 31-34 mg / kg; in step (S01), the basic fertility indicators of the soil surface layer (0-10 cm) are: pH 5.9, organic matter content 24.1 g / kg, total nitrogen content 1.43 g / kg, available nitrogen 121 mg / kg, available phosphorus 6.9 mg / kg, available potassium 32 mg / kg.

[0052] (S02) Select annual ryegrass as green manure. Take fresh grass from the upper part of the ryegrass plants during the flowering period. Perform low-temperature enzymatic hydrolysis-anaerobic pre-decomposition composite pretreatment on the fresh ryegrass to obtain pretreated ryegrass material. The low-temperature enzymatic hydrolysis-anaerobic pre-decomposition composite pretreatment in step (S02) is as follows: first, chop the fresh ryegrass into 2-5cm pieces, spray the chopped material evenly with a compound enzyme preparation and mix thoroughly, then spray the hydrolyzed material evenly with sodium lignosulfonate solution and mix thoroughly, seal and compact to control the oxygen content inside the pile to ≤1%; in step (S02), the mass ratio of cellulase to xylanase in the compound enzyme preparation is 1:0.6-1, the temperature of the enzymatic hydrolysis pile is controlled at 25-30℃ and the humidity at 60-65%, the enzymatic hydrolysis treatment is carried out for 48-72 hours, and the anaerobic treatment is controlled. The pre-corrosion pile temperature is 28–32℃, and the anaerobic pre-corrosion time is 24–36 h. In step (S02), the mass ratio of cellulase to xylanase in the compound enzyme preparation is 1:0.7–0.9, the temperature of the enzymatic hydrolysis pile is controlled at 27–29℃ and the humidity at 62–64%, and the enzymatic hydrolysis treatment is carried out for 54–66 h. The temperature of the anaerobic pre-corrosion pile is controlled at 29–31℃, and the anaerobic pre-corrosion treatment is carried out for 28–32 h. In step (S02), the mass ratio of cellulase to xylanase in the compound enzyme preparation is 1:0.8, the temperature of the enzymatic hydrolysis pile is controlled at 28℃ and the humidity at 63%, and the enzymatic hydrolysis treatment is carried out for 60 h. The temperature of the anaerobic pre-corrosion pile is controlled at 30℃, and the anaerobic pre-corrosion treatment is carried out for 30 h. The compound enzyme preparation used is food-grade or agricultural-grade cellulase with a purity ≥90%, and the food-grade or agricultural-grade cellulase with a purity ≥8% is used. A physical mixture of 5% xylanase, without a carrier, is prepared. Cellulase and xylanase are commercially available; for example, cellulase was purchased from Zhuhai Panhai Biotechnology Co., Ltd. (food grade), and xylanase from Anhui Zhonghong Bioengineering Co., Ltd. (food grade). Alternatively, they can be prepared via microbial fermentation, using conventional methods in this field. The compound enzyme preparation is formulated into a liquid spray using deionized water as a solvent. The concentration of the enzyme solution after preparation is 5%–8%, and it is sprayed evenly at 0.05%–0.08% of the fresh ryegrass mass. After spraying, the mixture is thoroughly stirred to ensure uniform mixing of the material and the enzyme solution. In step (S02), the pretreated ryegrass material has a fresh substrate moisture content of 88.0%–89.0% and a nitrogen content of 2.00–2.10%. The content of N, P2O5 is 0.90-1.00 g / kg, and K2O is 2.90-3.00 g / kg; in step (S02), the moisture content of the pretreated ryegrass material is 88.5%-88.8%, and the content of N, P2O5 is 0.93-0.97 g / kg, and the content of K2O is 2.92-2.97 g / kg; in step (S02), the moisture content of the pretreated ryegrass material is 88.7%, and the content of N, P2O5, and K2O is 2.06 g / kg, 0.96 g / kg, and 2.95 g / kg; in step (S02), the amount of compound enzyme preparation sprayed is 0.05-0.5% of the mass of fresh ryegrass.The compound enzyme preparation in step (S02) has an enzyme activity of 5000-6000 U / g of cellulase and 3000-4000 U / g of xylanase. The spraying amount of the compound enzyme preparation in step (S02) is 0.06-0.08% of the weight of fresh ryegrass, with cellulase activity of 5200-5600 U / g and xylanase activity of 3300-3800 U / g. The spraying amount of the compound enzyme preparation in step (S02) is 0.07% of the weight of fresh ryegrass, with cellulase activity of 5500 U / g and xylanase activity of 3600 U / g. The mass concentration of the sodium lignosulfonate solution in step (S02) is 0.01-0.05%, and the spraying amount is... The mass concentration of sodium lignosulfonate solution in step (S02) is 1-4% of the fresh wheatgrass; the mass concentration of sodium lignosulfonate solution in step (S02) is 0.02-0.04%, and the spraying amount is 1.5-3.5% of the fresh ryegrass mass; the mass concentration of sodium lignosulfonate solution in step (S02) is 0.03%, and the spraying amount is 3% of the fresh ryegrass mass; the sodium lignosulfonate used is industrial grade, with a molecular weight of 8000-12000 Da and a purity ≥90%, and the preparation solvent is deionized water. During preparation, it is stirred at 300 r / min at 25℃ until completely dissolved, and used after standing for 2 hours. Sodium lignosulfonate can be purchased from Shanghai Gaoming Chemical Co., Ltd., model number 435192.

[0053] (S03) In mid-April each year, adjust the application method according to the soil moisture in the 0-10cm layer of the planting field in step (S01). When the soil moisture is 60-70% of the field capacity, apply the pretreated ryegrass material from step (S02) into the cultivated layer of the planting field using a layered gradient compaction method; or apply 30t / ha-60t / ha of pretreated ryegrass material to the planting field in step (S01) and apply conventional fertilizer at the same time. The soil moisture in the 0-10cm layer is measured using a tensiometer method. A soil moisture rapid tester, model SJ9-TZS-ECW, purchased from Dongfang Chemical Glass (Beijing) Technology Co., Ltd., is used. Samples are taken at 5 points in an S-shape in the planting field, and the average value is taken as the percentage of field capacity. The field capacity is measured using the ring cutter method, according to NY / T The procedure is as follows: Follow 1121.2-2006 "Soil Testing Part 2: Determination of Soil Moisture"; In step (S03), when the soil moisture content is 40-59% of field capacity, first thoroughly irrigate to 60-70% of field capacity, and after the soil has no standing water, apply the pre-treated ryegrass material to the topsoil layer using a stratified gradient compaction method; In step (S03), the stratified gradient compaction is as follows: by weight ratio, 50%-70% of the pre-treated ryegrass material is compacted to a 5-10cm soil layer, and 30%-50% of the pre-treated ryegrass material is compacted to a 0-5cm soil layer; In step (S03), the stratified gradient compaction is as follows: by weight ratio, 55%-65% of the pre-treated ryegrass material is compacted to a 5-10cm soil layer, and 35%... ~45% of the pretreated ryegrass material is compacted to a soil layer of 0-5cm; in step (S03), the layered gradient compaction is as follows: by mass ratio, 60% of the pretreated ryegrass material is compacted to a soil layer of 5-10cm, and 40% of the pretreated ryegrass material is compacted to a soil layer of 0-5cm; an adjustable-depth rotary tiller is used for layered compaction. First, 30%-50% of the pretreated ryegrass material is evenly spread on the surface of the planting field and compacted to a soil layer of 0-5cm with a rotary tiller. The tillage depth is precisely controlled at 5cm, and the soil is lightly compacted and leveled. Then, the remaining 50%-70% of the material is spread on the surface and compacted to a soil layer of 5-10cm with a rotary tiller. The tillage depth is precisely controlled at 10cm. After compaction, the soil bulk density is maintained at 1.2-1.3 g / cm³, avoid cross-mixing of soil layers; the total application rate of pretreated ryegrass material in step (S03) is 30-120 t / ha; the total application rate of pretreated ryegrass material in step (S03) is 60-90 t / ha; the application rate of conventional fertilizer in step (S03) is 40%-100% of the conventional application rate; the application rate of conventional fertilizer in step (S03) is 60%-80% of the conventional application rate; the application rate of N in conventional fertilizer in step (S03) The application rates are as follows: 200–220 kg / ha for nitrogen, 55–65 kg / ha for P2O5, and 120–125 kg / ha for K2O; in step (S03), the application rates of conventional fertilizers are as follows: 205–215 kg / ha for nitrogen, 57–62 kg / ha for P2O5, and 121–123 kg / ha for K2O; in step (S03), the application rates of conventional fertilizers are as follows: 210 kg / ha for nitrogen, 200–220 kg / ha for nitrogen, 55–65 kg / ha for P2O5, and 120–125 kg / ha for K2O; The application rate of 2O5 is 60 kg / ha, and the application rate of K2O is 121.5 kg / ha. In step (S03), the pretreated ryegrass material is applied to the topsoil of the planting field by returning it to the target field. Returning to the target field means planting ryegrass in a winter fallow field with soil conditions consistent with those of the planting field of this invention. The consistent soil conditions in the off-site planting field refer to paddy soil developed from red soil and yellow clay soil. The basic fertility indicators of the 0-10cm soil layer deviate from those of the target planting field within the following ranges: pH ±0.2, organic matter content ±0.5g / kg, total nitrogen content ±0.02g / kg, available nitrogen ±5mg / kg, available phosphorus ±0.3mg / kg, and available potassium ±2mg / kg. The climate zone is consistent with that of the target planting field. The management method of off-site planting is consistent with that of green manure planting of this invention. The fresh ryegrass is transported to the target planting field within 24 hours after harvesting. During transportation, it is wrapped with a moisturizing film to maintain a moisture content of more than 85% to avoid drying and deterioration.

[0054] (S04) After completing the pre-treatment of ryegrass material by applying it alone or in combination with chemical fertilizer, dynamic flooding management of the rice planting field in step (S03) is carried out throughout the entire growth period of rice. The dynamic flooding management of the rice planting field in step (S04) is as follows: 1-15 days after returning the ryegrass material to the field, maintain a shallow water layer of 3-5 cm; 16-30 days after returning the ryegrass material to the field, maintain a deep water layer of 8-10 cm; maintain a shallow water layer of 3-5 cm during the rice tillering stage; and maintain a stable water layer of 5-8 cm from the jointing stage to the maturity stage. The dynamic flooding management in step (S04) is carried out by using hard field ridges covered with plastic film to separate each planting field for independent irrigation and drainage.

[0055] (S05) In early May each year, indica-japonica hybrid late-season rice is sown. In mid-June, late-season rice seedlings with 2-4 tillers and relatively uniform growth are transplanted to the planting field of step (S04). In step (S05), during the tillering and jointing stages of the rice, soil samples from the 0-10cm soil layer of the planting field are collected using the S-shaped 5-point sampling method to determine the available nitrogen content. When the available nitrogen content is lower than 90mg / kg, rye straw decomposed liquid is applied as a top dressing. No other chemical fertilizers are applied during the same period as the top dressing. In step (S05), the indica-japonica hybrid late-season rice is Yongyou 9, and the transplanting density of the late-season rice is 24-2. 60,000 clumps / ha; in step (S05), the transplanting density of late rice is 245,000–255,000 clumps / ha; in step (S05), the transplanting density of late rice is 250,000 clumps / ha; in step (S05), the ryegrass decomposition solution is prepared by decomposing the pretreated ryegrass material obtained in step (S02) with water at a mass ratio of 1:13–17 for 10–20 days and filtering, and the application rate is 1500–2000 L / ha each time; in step (S05), the ryegrass decomposition solution is prepared by decomposing the pretreated ryegrass material obtained in step (S02) with water at a mass ratio of 1:14–16 for 1 day. The ryegrass decomposition solution is obtained by filtration after 3–17 days, with an application rate of 1600–1900 L / ha each time; in step (S05), the ryegrass decomposition solution is obtained by decomposing the pretreated ryegrass material obtained in step (S02) with water at a mass ratio of 1:15 for 15 days and then filtering, with an application rate of 1750 L / ha each time; the total nitrogen content of the ryegrass decomposition solution in step (S05) is 0.8–1.2 g / L and the total carbon content is 15–20 g / L; the total nitrogen content of the ryegrass decomposition solution in step (S05) is 0.9–1.1 g / L and the total carbon content is 17–19 g / L. In step (S05), the total nitrogen content of the ryegrass decomposition liquid is 1 g / L and the total carbon content is 18 g / L. The decomposition conditions are constant temperature of 28-30℃, sealed anaerobic decomposition, stirring at 200 r / min for 10 min every 3 days. After decomposition, the liquid is filtered through a 200-mesh nylon filter under a negative pressure of 0.05 MPa. The clear filtrate is taken as the decomposition liquid. The filtrate is stored in a sealed refrigerator at 4℃ in the dark. No preservatives are added during the storage process. If the filtrate becomes turbid or has an odor, it must not be used and must be prepared again. The prepared decomposition liquid must be used within 7 days.

[0056] (S06) Continue the application of ryegrass materials and rice planting management for 6 to 8 years in accordance with the operations of steps (S03) to (S05), and then stop applying ryegrass materials and chemical fertilizers, and enter a 2-year carbon stabilization period. In step (S06), during the carbon stabilization period, maintain conventional rice planting. Except for ryegrass decomposition liquid, no chemical fertilizers or external organic fertilizers are applied throughout the process. After the rice harvest each year, the rice stubble is left in place without being removed. Full-cycle no-till management is adopted. During the winter fallow period, a thin water layer of 1 to 2 cm is maintained and water is added to maintain the stability of the water layer until the rice is drained before the next year's rice planting.

[0057] In this invention, low-temperature enzymatic hydrolysis specifically refers to enzymatic hydrolysis reactions at 25–30°C. This temperature range is the optimal enzymatic hydrolysis temperature for cellulase and xylanase, and is below the critical temperature of 35°C for the overmineralization of ryegrass organic matter, hence it is defined as low temperature. The temperature threshold for the overmineralization of ryegrass organic matter is ≥35°C.

[0058] Field water holding capacity refers to the soil moisture content of paddy soil developed from red soil and yellow clay soil in the planting field after full irrigation and removal of gravity water, which is determined by the ring cutter method according to NY / T1121.2-2006.

[0059] Carbon pool activity is the ratio of active organic carbon to inactive organic carbon in soil. The active organic carbon in soil was determined by the oxidation method with 333 mmol / L neutral potassium permanganate at pH 7.0, according to NY / T 395-2020 "Determination of Organic Matter in Farmland Soils". The specific procedure is as follows: weigh 5.00 g of air-dried soil sample that has passed through a 2 mm sieve, add 50 mL of 333 mmol / L potassium permanganate solution, shake at 25℃ for 30 min at a shaking rate of 180 r / min, filter, measure the absorbance of the filtrate, and calculate the active organic carbon content.

[0060] No-till management is a field management method that prohibits any tillage activities that disturb the soil topsoil, such as plowing, rotary tillage, and harrowing, during the crop growth cycle. Only manual weeding and water and fertilizer management are carried out. Weeds in the field are controlled by manual weeding, once every 15 days. During the tillering and jointing stages of rice, which are the peak periods for weeds, manual weeding is carried out once every 7 days. The weeds that are pulled out are taken out of the planting field for disposal and must not be left in the field to decompose.

[0061] Off-site green manure return involves planting green manure in a plot of land with soil and climate conditions similar to the target planting field, and then transporting the green manure material to the target planting field for return after harvesting. This method differs from planting and returning green manure in the target planting field on-site.

[0062] Example 1: This example describes a method for rapidly and stably increasing the organic carbon content of paddy field soil using ryegrass green manure, comprising the following steps:

[0063] (S01) A winter fallow field with a single-season late rice crop was selected as the planting field. The planting field is located in the mid-subtropical monsoon climate zone, where the average annual temperature is 17.9℃, the average annual sunshine duration is 1700h, and the average annual precipitation is 1500mm. The soil of the planting field is paddy soil developed from red soil and yellow clay soil. The basic fertility index of the top 0-10cm layer of this soil is pH 6.5, organic matter content 25.0g / kg, total nitrogen content 1.45g / kg, available nitrogen 125mg / kg, available phosphorus 7.5mg / kg, and available potassium 35mg / kg.

[0064] (S02) Green manure was selected as annual ryegrass of the forage type. Fresh grass from the upper part of the ryegrass plants during the flowering period was taken. The fresh ryegrass was subjected to a low-temperature enzymatic hydrolysis-anaerobic pre-decomposition compound pretreatment. First, the fresh ryegrass was chopped to 5cm. The compound enzyme preparation was evenly sprayed onto the chopped material and thoroughly mixed. The amount of compound enzyme preparation sprayed was 0.08% of the mass of fresh ryegrass. The mass ratio of cellulase to xylanase in the compound enzyme preparation was 1:1. The enzyme activity of cellulase was 6000U / g and the enzyme activity of xylanase was 4000U / g. The temperature of the pile was controlled at 30℃. The humidity was 65%, and the enzymatic hydrolysis was carried out for 72 hours. Then, sodium lignosulfonate solution (0.05% concentration) was evenly sprayed onto the hydrolyzed material and mixed thoroughly. The spraying amount was 4% of the fresh ryegrass mass. The pile was sealed and compacted to control the internal oxygen content to ≤1%. The pile temperature was 32℃, and anaerobic pre-decomposition was carried out for 36 hours to obtain pretreated ryegrass material. The fresh basis moisture content of the pretreated ryegrass material was 89.0%, and the fresh basis content was 2.10 g / kg N, 1.00 g / kg P2O5, and 3.00 g / kg K2O.

[0065] (S03) In mid-April each year, the soil moisture in the 0-10cm layer of the planting field is tested and found to be 65% of the field capacity. The pretreated ryegrass material is then applied to the topsoil of the planting field in a layered gradient compaction method, using off-site return to the field. Specifically, the layered gradient compaction is carried out by mass ratio, with 70% of the pretreated ryegrass material compacted to the 5-10cm soil layer and 30% of the pretreated ryegrass material compacted to the 0-5cm soil layer. The total application rate of the pretreated ryegrass material is 120t / ha.

[0066] (S04) After the pre-treatment of ryegrass material is completed and applied individually, the planting fields are separated by hard ridges and plastic film for independent irrigation and drainage. Dynamic management of flooding throughout the rice growth period is implemented. A shallow water layer of 5cm is maintained for 1-15 days after the ryegrass material is returned to the field, a deep water layer of 10cm is maintained for 16-30 days after the material is returned to the field, a shallow water layer of 5cm is maintained during the rice tillering stage, and a stable water layer of 8cm is maintained from the jointing stage to the maturity stage.

[0067] (S05) In early May each year, the late-season hybrid rice variety Yongyou 9 is sown. In mid-June, the late-season rice seedlings with 4 tillers and relatively uniform growth are transplanted to the planting field. The rice transplanting density is 260,000 clumps / ha. During the tillering and jointing stages of the rice, soil samples from the 0-10cm soil layer of the planting field are collected using the S-shaped 5-point sampling method to determine the available nitrogen content. When the available nitrogen content is lower than 90mg / kg, ryegrass decomposition liquid is applied as a top dressing. No other chemical fertilizers are applied at the same time as the top dressing. The ryegrass decomposition liquid is prepared by decomposing the pretreated ryegrass material obtained in step (S02) with water at a mass ratio of 1:17 for 20 days and then filtering. The total nitrogen content of the ryegrass decomposition liquid is 1.2g / L and the total carbon content is 20g / L. The amount of each top dressing is 2000L / ha.

[0068] (S06) Continue applying ryegrass materials and managing rice planting for 7 years according to the operations of steps (S03) to (S05), then stop applying ryegrass materials and enter a 2-year carbon stabilization period; during the carbon stabilization period, maintain conventional rice planting, and do not apply any chemical fertilizers or external organic fertilizers except for ryegrass decomposition liquid. After each rice harvest, leave the rice stubble in place without removing it, and adopt full-cycle no-till management. During the winter fallow period, maintain a 2cm thin water layer and replenish water to maintain water layer stability until drainage before rice planting the following year.

[0069] Example 2: This example is basically the same as Example 1, except that in step (S01), a fallow field with a single-season late rice crop is selected as the planting field. The planting field is located in the mid-subtropical monsoon climate zone, where the average annual temperature is 17.9℃, the average annual sunshine duration is 1700h, and the average annual precipitation is 1500mm. The soil of the planting field is paddy soil developed from red loam and yellow clay soil. The basic fertility indicators of the 0-10cm topsoil are: pH 5.9, organic matter content 24.1g / kg, total nitrogen content 1.43g / kg, available nitrogen 121mg / kg, available phosphorus 6.9mg / kg, and available potassium 32mg / kg. (S02) Green manure was selected as annual ryegrass of the forage type. Fresh grass from the upper part of the ryegrass plants during the flowering period was taken. The fresh ryegrass was subjected to a low-temperature enzymatic hydrolysis-anaerobic pre-composting compound pretreatment. First, the fresh ryegrass was chopped to 3cm. The compound enzyme preparation was evenly sprayed onto the chopped material and thoroughly mixed. The amount of compound enzyme preparation sprayed was 0.07% of the mass of fresh ryegrass. The mass ratio of cellulase to xylanase in the compound enzyme preparation was 1:0.8. The enzyme activity of cellulase was 5500U / g and the enzyme activity of xylanase was 3600U / g. The pile temperature was controlled at 28℃ and the humidity at 63%. The enzymatic hydrolysis treatment lasted for 60h. Then, sodium lignosulfonate solution was evenly sprayed onto the enzymatically hydrolyzed material and... The mixture was thoroughly mixed, and the sodium lignosulfonate solution had a mass concentration of 0.03%. The spraying amount was 3% of the fresh ryegrass mass. The mixture was sealed and compacted to control the oxygen content inside the pile to ≤1%. The pile temperature was 30℃, and the mixture was anaerobic pre-composted for 30 hours to obtain pretreated ryegrass material. The fresh substrate moisture content of the pretreated ryegrass material was 88.7%, and the N content, P2O5 content, and K2O content in the fresh substrate were 2.06 g / kg, 0.96 g / kg, and 2.95 g / kg, respectively. In step (S03), in mid-April each year, the soil moisture in the 0-10 cm soil layer of the planting field was tested and found to be 65% of the field capacity. The pretreated ryegrass material was then applied to the field by returning it to the field in a layered gradient compaction method. The pre-treated ryegrass is incorporated into the topsoil of the planting field. Layered, gradient compaction is implemented by weight ratio: 60% of the pre-treated ryegrass is compacted to a 5-10cm soil layer, and 40% is compacted to a 0-5cm soil layer. The total application rate of pre-treated ryegrass is 90t / ha. After the single application of pre-treated ryegrass in step (S04), the planting fields are separated by hard ridges covered with plastic film for independent irrigation and drainage. Dynamic flooding management is implemented throughout the rice's growth period. A shallow water layer of 4cm is maintained for 1-15 days after the ryegrass is returned to the field, a deep water layer of 9cm is maintained for 16-30 days, a shallow water layer of 4cm is maintained during the rice tillering stage, and a deep water layer of 6cm is maintained from the jointing stage to maturity.A 5cm stable water layer is established. In step (S05), the hybrid indica-japonica late-season rice variety Yongyou 9 is sown in early May each year. In mid-June, late-season rice seedlings with three tillers and relatively uniform growth are transplanted to the planting field at a planting density of 250,000 clumps / hectare. During the tillering and jointing stages of the rice, soil samples from the 0-10cm soil layer of the planting field are collected using the S-shaped 5-point sampling method to determine the available nitrogen content. When the available nitrogen content is lower than 90mg / kg, ryegrass decomposition liquid is applied as a top dressing. No other chemical fertilizers are applied during the same period. The ryegrass decomposition liquid is prepared by decomposing the pretreated ryegrass material obtained in step (S02) with water at a mass ratio of 1:15 for 15 days and then filtering. The total nitrogen content of the decomposed liquid is 1 g / L, and the total carbon content is 18 g / L. The application rate is 1750 L / ha each time. Step (S06) involves continuous application of ryegrass as a material for rice cultivation and management for 7 years, following steps (S03) to (S05). Afterward, the application of ryegrass is discontinued, and a 2-year carbon stabilization period is implemented. During this period, conventional rice cultivation is maintained. Except for the ryegrass decomposed liquid, no chemical fertilizers or exogenous organic fertilizers are applied. After each rice harvest, the rice stubble is left in place without removal, and no-till management is adopted throughout the entire cycle. During the winter fallow period, a thin water layer of 1.5 cm is maintained and replenished to maintain water stability until drainage before the following year's rice planting.

[0070] Example 3: This example is basically the same as Example 1, except that in step (S01), a fallow field with a single-season late rice crop is selected as the planting field. The planting field is located in the mid-subtropical monsoon climate zone, where the average annual temperature is 17.9℃, the average annual sunshine duration is 1700h, and the average annual precipitation is 1500mm. The soil of the planting field is paddy soil developed from red loam and yellow clay soil. The basic fertility indicators of the 0-10cm topsoil are: pH 5.5, organic matter content 23.0g / kg, total nitrogen content 1.40g / kg, available nitrogen 115mg / kg, available phosphorus 6.5mg / kg, and available potassium 30mg / kg. In step (S02), green manure is selected as annual ryegrass, a forage grass. Fresh ryegrass plants in full bloom are taken and subjected to low-temperature enzymatic hydrolysis-anaerobic pre-decomposition compound pretreatment. The fresh ryegrass is first chopped into 2cm pieces. m. A compound enzyme preparation was evenly sprayed onto the chopped material and thoroughly mixed. The amount of compound enzyme preparation applied was 0.05% of the weight of fresh ryegrass. The mass ratio of cellulase to xylanase in the compound enzyme preparation was 1:0.6. The enzyme activity of cellulase was 5000 U / g, and the enzyme activity of xylanase was 3000 U / g. The pile temperature was controlled at 25℃ and the humidity at 60%, and the enzymatic hydrolysis was carried out for 48 hours. Then, sodium lignin sulfonate solution was evenly sprayed onto the enzymatically hydrolyzed material and mixed. The mass concentration of sodium lignin sulfonate solution was 0.01%, and the amount applied was 1% of the weight of fresh ryegrass. The pile was sealed and compacted to control the oxygen content inside the pile to ≤1%. The pile temperature was 28℃, and the anaerobic pre-decomposition was carried out for 24 hours to obtain pretreated ryegrass material. The fresh basis moisture content of the pretreated ryegrass material was 88.0%, and the fresh basis content was 2.00 g / kg N, 0.90 g / kg P2O5, and 2.90g / kg; Step (S03): In mid-April each year, the soil moisture in the 0-10cm layer of the planting field is tested to be 50% of the field capacity. The field is then thoroughly irrigated to 60% of the field capacity. The pretreated ryegrass material is then returned to the field from a different location. After the soil is dry, it is applied to the topsoil using a layered gradient compaction method. Specifically, based on a mass ratio, 50% of the pretreated ryegrass material is compacted to the 5-10cm soil layer, and 50% is compacted to the 0-5cm soil layer. The total application rate of the pretreated ryegrass material is 30g / kg. t / ha; Step (S04) After the pre-treatment of ryegrass material is completed and applied individually, the planting fields are separated by hard ridges and plastic film for independent irrigation and drainage. Dynamic management of flooding throughout the rice growth period is implemented. After the ryegrass material is returned to the field, a shallow water layer of 3cm is maintained for 1-15 days, a deep water layer of 8cm is maintained for 16-30 days, a shallow water layer of 3cm is maintained during the rice tillering stage, and a stable water layer of 5cm is maintained from the jointing stage to maturity. Step (S05) In early May each year, the indica-japonica hybrid late rice variety Yongyou 9 is sown. In mid-June, the late rice with two tillers and relatively uniform growth is transplanted. Rice seedlings were transplanted to the planting field at a density of 240,000 clumps per hectare. During the tillering and jointing stages, soil samples from the 0-10cm soil layer were collected using an S-shaped 5-point sampling method to determine the available nitrogen content. When the available nitrogen content was below 90 mg / kg, ryegrass decomposed liquid was applied as a top dressing. No other chemical fertilizers were applied concurrently. The ryegrass decomposed liquid was prepared by mixing pretreated ryegrass material obtained in step (S02) with water at a mass ratio of 1:13, decomposing for 10 days, and then filtering. The total nitrogen content of the ryegrass decomposed liquid was 0.8 g / L, and the total carbon content was 15 g / L. The application rate for each topdressing is 1500 L / ha. Step (S06) involves continuous application of ryegrass and rice cultivation management for 7 years, following steps (S03) to (S05). Afterward, ryegrass application is discontinued, followed by a 2-year carbon stabilization period. During this period, conventional rice cultivation is maintained. Except for ryegrass decomposition liquid, no chemical fertilizers or exogenous organic fertilizers are applied. After each rice harvest, rice stubble is left in place without removal, and no-till management is implemented throughout the entire cycle. During the winter fallow period, a 1 cm water layer is maintained and replenished to maintain water stability until drainage before the following year's rice planting.

[0071] Example 4: This example is basically the same as Example 1, except that in step (S03), in mid-April each year, the soil moisture in the 0-10cm layer of the planting field is measured to be 65% of the field water holding capacity. The pretreated ryegrass material is applied to the topsoil of the planting field in a layered gradient compaction method by returning it to the field in a different location. Specifically, the layered gradient compaction is carried out by mass ratio, with 60% of the pretreated ryegrass material compacted to the 5-10cm soil layer and 40% of the pretreated ryegrass material compacted to the 0-5cm soil layer. The total application rate of the pretreated ryegrass material is 60t / ha.

[0072] Example 5: This example is basically the same as Example 1, except that in step (S03), in mid-April each year, the soil moisture in the 0-10cm layer of the planting field is measured to be 65% of the field capacity. The pretreated ryegrass material is then applied to the topsoil of the planting field using a layered gradient compaction method. Specifically, based on a mass ratio, 70% of the pretreated ryegrass material is compacted to the 5-10cm soil layer, and 30% is compacted to the 0-5cm soil layer. After applying 45 t / ha of pretreated ryegrass material, all conventional fertilizers applied at the same time are used as base fertilizers. After the pretreated ryegrass material is turned over and compacted, it is applied to the 0-10 cm soil layer of the planting field in one go. After application, it is lightly compacted and leveled. During the rice growing season, no other fertilizers are applied except for ryegrass decomposition liquid. The amount of conventional fertilizer applied is 80% of the conventional amount. The amount of N applied in conventional fertilizer is 220 kg / ha, the amount of P2O5 applied is 65 kg / ha, and the amount of K2O applied is 125 kg / ha.

[0073] Example 6: This example is basically the same as Example 1, except that in step (S03), in mid-April each year, the soil moisture in the 0-10cm layer of the planting field is measured to be 65% of the field capacity. The pretreated ryegrass material is then applied to the topsoil of the planting field using a layered gradient compaction method. Specifically, based on a mass ratio, 60% of the pretreated ryegrass material is compacted to the 5-10cm soil layer, and 40% is compacted to the 0-5cm soil layer. This is then applied to the planting field... After applying 45 t / ha of pretreated ryegrass, all conventional fertilizers applied concurrently are used as base fertilizers. After the pretreated ryegrass is turned over and compacted, it is applied to the 0-10 cm soil layer of the planting field in one go. After application, it is lightly compacted and leveled. During the rice growing season, no other fertilizers are applied except for ryegrass decomposition liquid. The amount of conventional fertilizer applied is 100% of the conventional amount. The amount of N applied in conventional fertilizer is 210 kg / ha, the amount of P2O5 applied is 60 kg / ha, and the amount of K2O applied is 121.5 kg / ha.

[0074] Example 7: This example is basically the same as Example 1, except that in step (S03), in mid-April each year, the soil moisture in the 0-10cm layer of the planting field is measured to be 65% of the field capacity. The pretreated ryegrass material is then applied to the topsoil of the planting field using a layered gradient compaction method. Specifically, based on a mass ratio, 60% of the pretreated ryegrass material is compacted to the 5-10cm soil layer, and 40% is compacted to the 0-5cm soil layer. This is then applied to the planting field... After applying 45 t / ha of pretreated ryegrass, all conventional fertilizers applied concurrently are used as base fertilizers. After the pretreated ryegrass is turned over and compacted, it is applied to the 0-10 cm soil layer of the planting field in one go. After application, it is lightly compacted and leveled. During the rice growing season, no other fertilizers are applied except for ryegrass decomposition liquid. The amount of conventional fertilizer applied is 60% of the conventional amount. The amount of N applied in conventional fertilizer is 210 kg / ha, the amount of P2O5 applied is 60 kg / ha, and the amount of K2O applied is 121.5 kg / ha.

[0075] Example 8: This example is basically the same as Example 1, except that in step (S03), in mid-April each year, the soil moisture in the 0-10cm layer of the planting field is measured to be 60% of the field capacity. The pretreated ryegrass material is then applied to the topsoil of the planting field using a layered gradient compaction method. Specifically, based on a mass ratio, 50% of the pretreated ryegrass material is compacted to the 5-10cm soil layer, and 50% is compacted to the 0-5cm soil layer. After applying 45 t / ha of pretreated ryegrass material, all conventional fertilizers applied at the same time are used as base fertilizers. After the pretreated ryegrass material is turned over and compacted, it is applied to the 0-10 cm soil layer of the planting field in one go. After application, it is lightly compacted and leveled. During the rice growing season, no other fertilizers are applied except for ryegrass decomposition liquid. The amount of conventional fertilizer is 40% of the conventional amount. The amount of N applied in conventional fertilizer is 200 kg / ha, the amount of P2O5 is 55 kg / ha, and the amount of K2O is 120 kg / ha.

[0076] Comparative Example 1: The method for increasing the organic carbon content of paddy field soil in this comparative example includes the following steps:

[0077] (S01) A winter fallow field with a single-season late rice crop was selected as the planting field. The planting field is located in the mid-subtropical monsoon climate zone, where the average annual temperature is 17.9℃, the average annual sunshine duration is 1700h, and the average annual precipitation is 1500mm. The soil of the planting field is paddy soil developed from red loam and yellow clay soil. The soil fertility of the top 0-10cm layer is pH 5.9, organic matter content 24.1g / kg, total nitrogen content 1.43g / kg, available nitrogen 121mg / kg, available phosphorus 6.9mg / kg, and available potassium 32mg / kg.

[0078] (S02) In mid-April each year, the planting field is plowed and prepared, with a plowing depth of 0-10cm. No green manure or chemical fertilizer is applied throughout the process. After plowing, the field is harrowed and ready for sowing.

[0079] (S03) In early May each year, the late-season rice variety Yongyou 9, a hybrid of indica and japonica, is sown. In mid-June, the late-season rice seedlings with three tillers and relatively uniform growth are transplanted into the planting field. The rice transplanting density is 250,000 clumps / hectare. No topdressing is applied during the entire growth period of the rice.

[0080] (S04) After rice transplanting, the planting field is flooded and managed. A shallow water layer of 3cm is maintained throughout the entire growth period. The water level is allowed to drop naturally during the yellow ripening period. Each field is separated by earthen ridges and unified irrigation and drainage are carried out.

[0081] (S05) Follow the steps (S02) to (S04) for 7 consecutive years of rice planting management, and then enter a 2-year continuous planting period. During the continuous planting period, maintain conventional rice planting, do not apply chemical fertilizers, and carry out conventional plowing and land preparation after each rice harvest. During the winter fallow period, the fields will dry naturally without artificial water layer management until the land is prepared before the rice sowing of the following year.

[0082] Comparative Example 2: The method for increasing the organic carbon content of paddy field soil in this comparative example includes the following steps:

[0083] (S01) A winter fallow field with a single-season late rice crop was selected as the planting field. The planting field is located in the mid-subtropical monsoon climate zone, where the average annual temperature is 17.9℃, the average annual sunshine duration is 1700h, and the average annual precipitation is 1500mm. The soil of the planting field is paddy soil developed from red loam and yellow clay soil. The soil fertility of the top 0-10cm layer is pH 5.9, organic matter content 24.1g / kg, total nitrogen content 1.43g / kg, available nitrogen 121mg / kg, available phosphorus 6.9mg / kg, and available potassium 32mg / kg.

[0084] (S02) In mid-April each year, conventional fertilizers are applied to the planting fields as base fertilizers. The application rate of conventional fertilizers is 210 kg / ha of N, 60 kg / ha of P2O5, and 121.5 kg / ha of K2O. After fertilization, conventional tillage and land preparation are carried out. The tillage depth is 5 cm. The land is then harrowed and prepared for sowing. No green manure or chemical fertilizers are applied throughout the process.

[0085] (S03) In early May each year, the late-season hybrid rice Yongyou 9 is sown. In mid-June, the late-season rice seedlings with 3 tillers and relatively uniform growth are transplanted to the planting field. The rice transplanting density is 250,000 clumps / hectare. During the tillering period of rice, urea is applied as usual, with the amount of urea being 30% of the total nitrogen content. No additional fertilizer is applied during the remaining growth stages.

[0086] (S04) After rice transplanting, the planting field is managed with conventional flooding. During the tillering stage, a shallow water layer of 4cm is maintained. The field is dried after the seedlings have grown enough. During the jointing stage to the grain filling stage, a water layer of 7cm is maintained. The field is allowed to dry naturally during the yellow ripening stage. Each field is separated by earthen ridges for unified irrigation and drainage.

[0087] (S05) Follow the steps (S02) to (S04) for 7 consecutive years of fertilizer application and rice planting management, then enter a 2-year continuous planting period. During the continuous planting period, maintain conventional rice planting, do not apply green manure or chemical fertilizers, and carry out conventional plowing and land preparation after rice harvest each year. During the winter fallow period, the fields will dry naturally without artificial water layer management until the land is prepared before rice sowing the following year.

[0088] The testing method is as follows:

[0089] 1. Methods for determining organic carbon in paddy field soil

[0090] Soil samples from the top 0–10 cm layer of paddy fields were collected during the rice harvest season in areas where ryegrass had been returned to the field. Five soil samples were randomly selected using an “S” shaped sampling method. Stones and crop residues were removed, and the samples were thoroughly mixed and placed in labeled sterile self-sealing bags, then quickly transported back to the laboratory. After the samples were air-dried, they were crushed and sieved through a 2 mm sieve for later use in determining soil organic carbon. Soil organic carbon was measured using a Shimadzu 500 organic carbon analyzer.

[0091] 2. Methods for analyzing the organic carbon content and dynamic changes in paddy field soil

[0092] The formulas for calculating soil organic carbon storage, carbon sequestration rate, and carbon sequestration rate per unit weight of green manure are as follows:

[0093] Organic carbon stock (SOCstock) (Mgha) -1 )=BD(gcm -3 )*depth(cm)*SOC(gkg -1 )*0.1

[0094] Carbon fixation rate (SOC) SR =ΔSOCstock / year;

[0095] Annual carbon sequestration rate (SOC) per unit weight of green manure SR =ΔSOCstock / (year*rate)

[0096] In the formula, SOCstock (Mg / ha) is the organic carbon stock (Mg / ha), BD is the soil bulk density, depth is the soil depth, and SOC is the organic carbon content; SOC SRThe carbon sequestration rate is given by 'rate', where 'rate' represents the amount of green manure applied. Soil bulk density was determined using the ring sampler method, following NY / T 1121.4-2006 "Soil Testing Part 4: Determination of Soil Bulk Density". Sampling locations were consistent with those for soil organic carbon. In the planting field, five points were sampled in an S-shape from the 0-10cm soil layer. Three ring samplers were collected from each sampling point, and the average value was taken as the soil bulk density for that field, used to calculate the organic carbon stock. Based on the organic carbon measurement results, soil organic carbon stock (SOCstock) and carbon sequestration rate (SOC) were calculated. SR The annual carbon sequestration rate per unit weight of ryegrass green manure. Sensitivity indicators for dynamic changes and storage. The specific calculation formula is:

[0097] Carbon Pool Management Index (CPMI) = Carbon Pool Index (CPI) * Carbon Pool Activity Index (AI) * 100

[0098] The Carbon Pool Index (CPI) is calculated as: Total Carbon Content of Sample / Total Carbon Content of Reference Soil.

[0099] Carbon pool activity index (AI) = Sample carbon pool activity / Reference soil carbon pool activity

[0100] Carbon pool activity (Active, A) = Soil active organic carbon content / Soil inactive organic carbon content

[0101] Non-active organic carbon content = Soil organic carbon content - Active organic carbon content.

[0102] Table 1: Organic carbon storage and carbon sequestration rate in the 0–10 cm soil layer after two years of pruning with pretreated ryegrass returned to the field and ceasing application.

[0103] Case Soil organic carbon storage (Mg / ha) <![CDATA[Carbon sequestration rate (Mg ha -1 yr -1 )]]> <![CDATA[Carbon sequestration rate of pre-treated ryegrass per unit weight per year (kg ha -1 yr -1 t -1 )]]> Example 1 23.00 0.57 4.76 Example 2 23.18 0.60 6.59 Example 3 21.5 0.26 8.63 Example 4 22.72 0.54 8.94 Example 5 22.98 0.28 6.17 Example 6 23.69 0.40 8.82 Example 7 23.44 0.35 7.88 Example 8 23.73 0.48 10.8 Comparative Example 1 16.43 - - Comparative Example 2 20.28 0.13 -

[0104] Table 2: Carbon pool management index of 0–10 cm soil layer after two years of pruning and cessation of ryegrass application

[0105] Case Carbon pool management index (%) of soil with no fertilization treatment as reference. Carbon pool management index (%) of soil with conventional fertilizer application as a reference. Example 1 113.9 126.7 Example 2 100.7 112.0 Example 3 100.4 108.6 Example 4 100.3 111.5 Example 5 102.4 109.2 Example 6 110.6 117.9 Example 7 106.1 113.0 Example 8 105.5 112.4 Comparative Example 1 100.0 - Comparative Example 2 89.6 100.0

[0106] In summary, refer to Tables 1-2 and Figures 1-5Soil organic carbon storage under different levels of ryegrass return to the field showed a trend of first increasing and then stabilizing with the increase of pre-treated ryegrass return. In Examples 1-4, where pre-treated ryegrass green manure was applied alone, the soil organic carbon storage was the highest at 23.18 Mg / ha, and the average soil organic carbon storage of the four treatments was 22.6 Mg / ha, which was 37.6% higher than the control group 1 (no fertilizer) and 11.4% higher than the control group 2 (fertilizer application). In Examples 5-8, where pre-treated ryegrass was applied in combination with fertilizer, the organic carbon storage was the highest at 23.73 Mg / ha, and the average soil organic carbon storage of the pre-treated ryegrass combined with fertilizer treatment was 23.5 Mg / ha. When rice is planted with pre-treated ryegrass alone, the optimal fertilization method is 90 t / ha of pre-treated ryegrass in Example 2. When pre-treated ryegrass is applied in combination with fertilizer, the optimal fertilization method is 45 t / ha of pre-treated ryegrass combined with 40% conventional fertilizer in Example 8.

[0107] Comparative Example 1 received no fertilizer and no input of any organic or inorganic nutrients. Soil organic carbon accumulated naturally only from rice stubble, resulting in an organic carbon storage of only 16.43 Mg / ha and no carbon fixation rate. This invention, through pretreatment of ryegrass for organic carbon input and targeted regulation of organic matter decomposition, achieved rapid accumulation of organic carbon, exceeding that of Comparative Example 1 by more than 37.6%. The core reason is that the low-temperature enzymatic hydrolysis-anaerobic pre-decomposition pretreatment of this invention improved the organic carbon conversion efficiency, while stratified gradient application and dynamic flooding management reduced the loss of organic carbon mineralization.

[0108] Comparative Example 2 involved the application of chemical fertilizers alone, relying solely on inorganic fertilizers for nutrients. Excessive fertilizer application led to soil acidification and compaction, decreased microbial activity, and low organic carbon sequestration efficiency, with a carbon sequestration rate of only 0.13 Mg ha. -1 yr -1 This invention optimizes the soil microbial community structure and enhances the carbon sequestration capacity of microorganisms by applying organic green manure in combination with chemical fertilizers or by applying green manure alone. Furthermore, the no-till management during the carbon stabilization period reduces soil carbon pool disturbance. Therefore, even after two years of cessation of application, the carbon sequestration rate is still more than 115% higher than that of Comparative Example 2, and the carbon pool management index is 9.2% to 17.9% higher.

[0109] In Examples 1-4, the soil carbon sequestration rate in the 0-10 cm soil layer between different levels of pretreated ryegrass application showed a trend of first increasing and then decreasing with the increase of pretreated ryegrass application. The maximum value among the four treatments with single application of pretreated ryegrass was 0.60 mgha. -1 yr -1 Among all fertilization treatments, Comparative Treatment 2 had the lowest carbon sequestration rate at 0.23 Mgha. -1 yr -1All pretreated ryegrass application treatments showed varying degrees of improvement in carbon sequestration rate compared to control example 2. The carbon sequestration rates of pretreated ryegrass in Examples 1-4 ranged from 0.26 to 0.60 Mgha. -1 yr -1 The average value is 0.49 mgha. -1 yr -1 In Examples 5-8, the carbon sequestration rate of pretreated ryegrass with chemical fertilizer in the 0-10cm soil layer showed a trend of first decreasing and then increasing with the increase of the proportion of chemical fertilizer applied, with Example 8 showing the highest rate of 0.48 mgha. -1 yr -1 Example 5 has a minimum of 0.28 Mgha -1 yr -1 The soil carbon sequestration rate after pretreatment with ryegrass and application of chemical fertilizers was 0.28–0.48 Mgha. -1 yr -1 The average value is 0.38 mgha. -1 yr -1 .

[0110] The annual carbon sequestration rate per unit weight of pretreated ryegrass in the 0-10cm soil layer showed a trend of first increasing and then decreasing with the increase of the amount of pretreated ryegrass returned to the field. The lowest rate was 4.76 kgha in Example 1. -1 yr -1 t -1 The annual carbon sequestration rate per unit weight of pretreated ryegrass was 4.76–8.94 kg / ha. -1 yr -1 t -1 The average value is 7.23 kgha -1 yr -1 t -1 The annual carbon sequestration rate per unit weight of pretreated ryegrass combined with chemical fertilizer treatment ranged from 6.17 to 10.80 kg / ha. -1 yr -1 t -1 Between, the average value is 8.42 kgha -1 yr -1 t -1 The annual carbon sequestration rate per unit weight of pretreated ryegrass showed a trend of first decreasing and then increasing with the increase of the proportion of chemical fertilizer applied to the pretreated ryegrass, with the maximum rate in Example 8 being 10.8 kgha. -1 yr -1 t -1 .

[0111] Two years after the termination of long-term ryegrass application, the soil carbon pool management index in the 0-10cm soil layer showed significant differences among the treatments. Using the unfertilized treatment (Comparative Example 1) as a reference, the soil carbon pool management index increased with the increase in the amount of ryegrass applied in the pre-treatment, reaching a maximum of 113.9% in Example 1. In the pre-treatment ryegrass application treatments, the soil carbon pool management index in Examples 2 and 4 was not significantly different from the unfertilized treatment in Comparative Example 1, while the soil carbon pool management index in Example 1 was 13.9% higher than the unfertilized treatment. This indicates that the pre-treatment ryegrass application treatment can maintain or promote soil carbon pool accumulation, while the single application of chemical fertilizer reduces the long-term stability and sustainability of the soil carbon pool. The carbon pool management index of the pre-treatment ryegrass combined with chemical fertilizer treatment ranged from 102.4% to 110.6%, with a mean of 106.2%.

[0112] When using conventional fertilizer application as a reference soil, the soil carbon pool management index differed significantly among different pre-treated ryegrass application rates, and showed an increasing trend with the increase of ryegrass application rate, reaching a maximum of 126.7% in Example 1. The carbon pool management indices of Examples 1-4 ranged from 111.5% to 126.7%, with an average of 114.7%, an increase of 14.7% compared to Comparative Example 2. This indicates that the pre-treated ryegrass application still contributes to the accumulation and stability of the soil carbon pool two years after cessation, and is superior to the conventional fertilizer-only treatment. The soil carbon pool management index differed significantly among pre-treated ryegrass with different fertilizer application ratios, reaching a maximum of 117.9% in Example 6. All pre-treated ryegrass with fertilizer application treatments were significantly higher than the fertilizer-only treatments, exceeding them by 9.2% to 17.9%. The carbon pool management index of pre-treated ryegrass with different fertilizer application ratios ranged from 109.2% to 117.9%, with an average of 113.1%, an increase of 13.1% compared to Comparative Example 2. This indicates that long-term application of pretreated ryegrass combined with chemical fertilizer is still superior to conventional chemical fertilizer alone in promoting soil carbon storage, even two years after fertilization has ceased.

[0113] The optimal embodiment of the single-application pretreatment of ryegrass in this invention is Example 2. Its core technical features are: optimal soil fertility (pH 5.9, 24.1 g / kg organic matter) in the 0-10 cm soil layer; a compound enzyme preparation mass ratio of 1:0.8; stratified gradient compaction (60% to 5-10 cm, 40% to 0-5 cm); ryegrass application rate of 90 t / ha; and moderate flooding dynamic management. This combination of optimal technical features achieves the best match between the organic matter decomposition rhythm and soil microbial activity, resulting in an organic carbon storage of 23.18 Mg / ha and a carbon fixation rate of 0.60 Mg / ha. -1 yr -1 This represents the optimal effect of a single application treatment.

[0114] The optimal embodiment of the pretreated ryegrass combined with chemical fertilizer application according to this invention is Example 8. Its core technical features are: ryegrass application rate of 45 t / ha, combined with 40% conventional chemical fertilizer, and stratified gradient compaction (50% to 5-10 cm, 50% to 0-5 cm). This combination achieves optimal synergy between the nutrient release rhythm of organic green manure and inorganic fertilizer, with low fertilizer application, which can alleviate soil acidification. The annual carbon sequestration rate per unit weight of ryegrass reaches 10.8 kg / ha. -1 yr -1 t -1 This is the optimal effect of combined treatment.

Claims

1. A method for rapidly and stably increasing the organic carbon content of paddy field soil using ryegrass green manure, characterized by: Including the following step, (S01) Select fallow fields that are used for planting a single season of late rice once a year as planting fields; (S02) Select green manure as pasture-type annual ryegrass, take fresh grass from the upper part of the ryegrass plant during the flowering period, and perform low-temperature enzymatic hydrolysis-anaerobic pre-decomposition compound pretreatment on the fresh ryegrass to obtain pretreated ryegrass material. (S03) In mid-April each year, adjust the application method according to the soil moisture of the 0-10cm layer of the planting field in step (S01). When the soil moisture is 60-70% of the field water holding capacity, apply the pretreated ryegrass material in step (S02) into the cultivated layer of the planting field in a layered gradient compaction method; or apply 30t / ha-60t / ha of pretreated ryegrass material to the planting field in step (S01) and apply conventional fertilizer at the same time. (S04) After completing the application of pretreated ryegrass material alone or in combination with chemical fertilizer, the rice planting field described in step (S03) is subject to dynamic flooding management throughout the entire growth period of rice. (S05) In early May each year, indica-japonica hybrid late rice is sown, and in mid-June, the late rice seedlings with 2 to 4 tillers and relatively uniform growth are transplanted to the planting field described in step (S04); (S06) Continue the application of ryegrass materials and rice planting management for 6 to 8 years in accordance with the operations of steps (S03) to (S05), and then stop applying ryegrass materials and chemical fertilizers, and enter a 2-year carbon stabilization period.

2. The method for rapidly and stably increasing the organic carbon content of paddy field soil using ryegrass green manure according to claim 1, characterized in that: In step (S01), the basic fertility indicators of the soil surface layer (0-10cm) are: pH 5.5-6.5, organic matter content 23.0-25.0 g / kg, total nitrogen content 1.40-1.45 g / kg, available nitrogen 115-125 mg / kg, available phosphorus 6.5-7.5 mg / kg, and available potassium 30-35 mg / kg.

3. The method for rapidly and stably increasing the organic carbon content of paddy field soil using ryegrass green manure according to claim 1, characterized in that: The low-temperature enzymatic hydrolysis-anaerobic pre-decomposition composite pretreatment in step (S02) involves first chopping fresh ryegrass into 2-5cm pieces, then uniformly spraying the chopped material with a composite enzyme preparation and mixing it thoroughly. Next, uniformly spraying the hydrolyzed material with a sodium lignosulfonate solution and mixing it thoroughly, then sealing and compacting the material to control the oxygen content inside the pile to ≤1%.

4. The method for rapidly and stably increasing the organic carbon content of paddy field soil using ryegrass green manure according to claim 1, characterized in that: In step (S02), the mass ratio of cellulase to xylanase in the compound enzyme preparation is 1:0.6-1. The temperature of the enzymatic hydrolysis pile is controlled at 25-30℃ and the humidity at 60-65%. The enzymatic hydrolysis treatment lasts for 48-72 hours. The temperature of the anaerobic pre-decomposition pile is controlled at 28-32℃. The anaerobic pre-decomposition lasts for 24-36 hours. In step (S02), the moisture content of the pretreated ryegrass material is 88.0%–89.0%, and the N content in the fresh substrate is 2.00–2.10 g / kg, the P2O5 content is 0.90–1.00 g / kg, and the K2O content is 2.90–3.00 g / kg.

5. The method for rapidly and stably increasing the organic carbon content of paddy field soil using ryegrass green manure according to claim 1, characterized in that: In step (S02), the amount of compound enzyme preparation sprayed is 0.05-0.08% of the weight of fresh ryegrass, with cellulase activity of 5000-6000 U / g and xylanase activity of 3000-4000 U / g. In step (S02), the mass concentration of sodium lignosulfonate solution is 0.01-0.05%, and the spraying amount is 1-4% of the mass of fresh ryegrass.

6. The method for rapidly and stably increasing the organic carbon content of paddy field soil using ryegrass green manure according to claim 1, characterized in that: In step (S03), when the soil moisture is 40-59% of the field capacity, the soil is first thoroughly irrigated to 60-70% of the field capacity. After the soil is dry, the soil is then applied to the topsoil layer of the planting field using a layered gradient compaction method. In step (S03), the layered gradient compaction is carried out by compacting 50% to 70% of the pretreated ryegrass material to a soil layer of 5 to 10 cm by mass ratio, and 30% to 50% of the pretreated ryegrass material to a soil layer of 0 to 5 cm. In step (S03), the application rate of conventional fertilizer is 200-220 kg / ha for nitrogen, 55-65 kg / ha for phosphorus, and 120-125 kg / ha for potassium.

7. The method for rapidly and stably increasing the organic carbon content of paddy field soil using ryegrass green manure according to claim 1, characterized in that: In step (S04), the dynamic management of flooding during the entire growth period of rice is as follows: 1-15 days after returning ryegrass to the field, maintain a shallow water layer of 3-5 cm; 16-30 days after returning ryegrass to the field, maintain a deep water layer of 8-10 cm; maintain a shallow water layer of 3-5 cm during the rice tillering stage; and maintain a stable water layer of 5-8 cm from the jointing stage to the maturity stage. In step (S04), the dynamic management of flooding involves using hard ridges covered with plastic film to separate each planting plot for independent irrigation and drainage.

8. The method for rapidly and stably increasing the organic carbon content of paddy field soil using ryegrass green manure according to claim 1, characterized in that: In step (S05), during the tillering and jointing stages of rice, soil samples from the 0-10cm soil layer of the planting field are collected using the S-shaped 5-point sampling method to determine the available nitrogen content. When the available nitrogen content is lower than 90mg / kg, rye straw decomposition liquid is applied as a top dressing, and no other chemical fertilizers are applied at the same time.

9. The method for rapidly and stably increasing the organic carbon content of paddy field soil using ryegrass green manure according to claim 1, characterized in that: In step (S05), the ryegrass decomposition liquid is prepared by decomposing the pretreated ryegrass material obtained in step (S02) with water at a mass ratio of 1:13-17 for 10-20 days and then filtering. The amount applied each time is 1500-2000 L / ha. In step (S05), the total nitrogen content of the rye grass decomposition liquid is 0.8–1.2 g / L and the total carbon content is 15–20 g / L.

10. The method for rapidly and stably increasing the organic carbon content of paddy field soil using ryegrass green manure according to claim 1, characterized in that: In step (S06), during the carbon stabilization period, rice is planted in a conventional manner. Except for the rye grass decomposition liquid, no chemical fertilizers or external organic fertilizers are applied throughout the process. After the rice harvest each year, the rice stubble is left in place without being removed. Full-cycle no-till management is adopted. During the winter fallow period, a thin water layer of 1-2 cm is maintained and water is replenished to maintain the stability of the water layer until the rice is drained before the following year's rice planting.

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