Method for reducing soil planting obstacles and methane emission in rice-shrimp field

Abstract

The present application relates to the field of ecological planting and breeding technology in rice field, in particular to a method for reducing soil planting obstacles and methane (CH4) emission in rice-shrimp field. The method provided by the present application separates and reduces the winter ponding area and time through the breeding of crayfish, increases the ventilation and oxygen content of the rice field, prolongs the decomposition time of the good nutrients of straw, and reduces the degree of gleying and improves the soil quality of the rice field; the next year, the rice is directly sowed to delay the rice flooding time, reduce the total ponding time during the rice growth period, increase the decomposition of the organic materials such as straw feed which is not used by crayfish, reduce the anaerobic decomposition of methanogens, effectively reduce the CH4 emission while ensuring the income of farmers.

Description

Technical Field

[0001] This invention relates to the field of rice-shrimp ecological farming technology, and in particular to a method for reducing soil planting obstacles and methane emissions in rice-shrimp fields. Background Technology

[0002] Rice-crayfish farming in paddy fields is a novel ecological agricultural model that effectively combines crop cultivation and aquaculture. The growth of rice provides food and shelter for the crayfish, while the crayfish's activity, in turn, increases dissolved oxygen in the soil and water, preys on pests, and promotes nutrient cycling in the paddy field soil. Furthermore, the rice-crayfish model utilizes water resources in paddy fields or surrounding ditches, improving the utilization rate of agricultural and natural resources such as water, soil, light, and heat, and yielding high economic benefits. However, traditional rice-crayfish rotation systems involve prolonged waterlogging of paddy fields during winter, keeping the soil in a reducing state for extended periods, exacerbating soil gleying and increasing the risk of greenhouse gas emissions. Additionally, traditional rice-crayfish rotation requires ditching, occupying paddy field area; the total area of ​​circular ditches and field ditches typically accounts for 8%–12% of the total paddy field area. The coexistence of adult crayfish and larvae in paddy fields and ditches leads to slower crayfish growth, smaller crayfish size, increased disease, and reduced yields, severely impacting the economic benefits of both rice and crayfish farming.

[0003] Paddy fields are a major source of the potent greenhouse gas CH4, accounting for 8.7% of total anthropogenic CH4 emissions. In rice-crayfish rotation systems, farmers often provide crayfish with excessive amounts of high-carbon straw and feed to increase crayfish yield. However, uneaten feed, crayfish molts, excrement, and dead crayfish accumulate, increasing the active carbon content in the soil. Under prolonged flooding conditions, these substances ferment and decompose in anaerobic environments. The following year, after rice planting, the elevated temperatures favor methanogenic bacteria utilizing these carbon sources to produce CH4. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for reducing soil planting obstacles and CH4 emissions in rice-shrimp paddy fields. The method provided by this invention can reduce the degree of gleying in paddy fields and improve soil quality, while reducing CH4 emissions from paddy fields and ensuring farmers' income.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for reducing soil planting obstacles and methane emissions in rice-shrimp paddy fields, comprising the following steps:

[0007] 1) After the mid-season rice harvest, the paddy fields are divided into shrimp larvae breeding areas and adult shrimp farming areas;

[0008] 2) Harvest the rice straw in the shrimp larvae breeding area, leaving a stubble of 30-50cm. After crushing the harvested rice straw, pile it up in the shrimp larvae breeding area at intervals of 5-10m. Shrimp larvae are then bred in the shrimp larvae breeding area. All the rice straw in the adult shrimp farming area is crushed and rotary tilled into the paddy field of the adult shrimp farming area.

[0009] 3) In March of the following year, water was poured and aquatic plants were planted in the adult shrimp farming area, and the shrimp larvae in the shrimp larvae breeding area were transferred to the adult shrimp farming area for cultivation; in June and July, after all the crayfish and shrimp larvae in the paddy field were harvested, rice was directly sown in the entire paddy field.

[0010] 5) After direct seeding of rice until the 3-leaf stage, when cracks appear in the paddy field, irrigate with a small amount of water, with the upper limit of irrigation being that there is no standing water in the paddy field; during the seedling stage to the early tillering stage, irrigate with a thin layer of water of 2-3 cm, and when the field water holding capacity of the paddy field is less than 80%, irrigate with another thin layer of water of 2-3 cm the next day; when the number of tillers per mu reaches 230,000 to 270,000 during the peak tillering stage, completely dry the field for 7-10 days; use intermittent irrigation from the jointing stage to the decomposition stage;

[0011] 6) Repeat steps 2) to 5) after rice harvest.

[0012] Preferably, the area ratio of the shrimp larvae breeding area to the adult shrimp farming area is 1:4 to 6.

[0013] Preferably, the method of separation includes setting up field ridges or digging a ring ditch around the shrimp larvae breeding area.

[0014] Preferably, when breeding shrimp larvae, 35-40 kg of parent shrimp are stocked per acre, with a female-to-male ratio of 3-5:1.

[0015] Preferably, the row spacing of the aquatic plants is 5-10m, and the plant spacing is 5-10m.

[0016] Preferably, the aquatic plants include one or more of the following: *Hydrilla verticillata*, *Ceratophyllum demersum*, *Eichhornia crassipes*, and *Lemna minor*.

[0017] Preferably, the shrimp larvae density in the adult shrimp farming area is 14,000 to 15,000 per mu (approximately 0.067 hectares).

[0018] Preferably, when direct-seeded rice is planted before mid-June, rice varieties with a growth period of less than 135 days should be selected; when direct-seeded rice is planted after mid-to-late June, rice varieties with a growth period of less than 120 days should be selected.

[0019] Preferably, the intermittent irrigation method includes: irrigating a paddy field with a water layer of 3-4 cm once, followed by dehydration for 1-3 days, and repeating the single irrigation and dehydration process.

[0020] Preferably, the rice fields are dried off and exposed to sunlight 7-10 days before harvest.

[0021] Beneficial effects:

[0022] The method provided by this invention reduces the area and duration of paddy fields flooded in winter by separating crayfish breeding and rearing, increases the aeration and oxygen content of paddy fields, prolongs the time for the organic decomposition of straw, and at the same time reduces the degree of paddy field gleying and improves soil quality. In the following year, direct seeding of rice delays the time of rice flooding, reduces the total flooding time of rice growing season, increases the organic decomposition of unused straw feed and other organic materials by crayfish, reduces the anaerobic decomposition of methanogenic bacteria, effectively reduces CH4 emissions while ensuring farmers' income. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0024] Figure 1 This study examines CH4 emissions from paddy fields after traditional rice transplanting and rice direct seeding using a combination of breeding and rearing separation, following rice-shrimp rotation. Detailed Implementation

[0025] This invention provides a method for reducing soil planting obstacles and methane emissions in rice-shrimp paddy fields, comprising the following steps:

[0026] 1) After the mid-season rice harvest, the paddy fields are divided into shrimp larvae breeding areas and adult shrimp farming areas;

[0027] 2) Harvest the rice straw in the shrimp larvae breeding area, leaving a stubble of 30-50cm. After crushing the harvested rice straw, pile it up in the shrimp larvae breeding area at intervals of 5-10m. Shrimp larvae are then bred in the shrimp larvae breeding area. All the rice straw in the adult shrimp farming area is crushed and rotary tilled into the paddy field of the adult shrimp farming area.

[0028] 3) In March of the following year, water was poured and aquatic plants were planted in the adult shrimp farming area, and the shrimp larvae in the shrimp larvae breeding area were transferred to the adult shrimp farming area for cultivation; in June and July, after all the crayfish and shrimp larvae in the paddy field were harvested, rice was directly sown in the entire paddy field.

[0029] 5) After direct seeding of rice until the 3-leaf stage, when cracks appear in the paddy field, irrigate with a small amount of water until there is no standing water in the paddy field; during the seedling stage to the early tillering stage, irrigate with a thin layer of water of 2-3 cm; when the field water holding capacity of the paddy field is less than 80%, irrigate with a thin layer of water of 2-3 cm again the next day; when the number of tillers per mu reaches 230,000 to 270,000 during the peak tillering stage, completely dry the field for 7-10 days; use intermittent irrigation from the jointing stage to the decomposition stage.

[0030] 6) Repeat steps 1) to 5) after rice harvest.

[0031] This invention preferably selects paddy fields with abundant, unpolluted water sources, flat terrain, convenient irrigation and drainage, and convenient transportation for transformation. After the mid-season rice harvest, the paddy fields are divided into shrimp larvae breeding areas and adult shrimp farming areas. In this invention, the mid-season rice harvest time is preferably October to November; the area ratio of the shrimp larvae breeding area to the adult shrimp farming area is preferably 1:4 to 6, more preferably 1:5; the separation method preferably includes setting up field ridges or digging a ring ditch around the shrimp larvae breeding area; the field ridges are preferably 0.8 to 1.2 m higher than the field surface, more preferably 1 m; the width of the field ridges is preferably 1.5 m, and the slope ratio is preferably 1:1 to 1.5, more preferably 1:1.5; the opening width of the ring ditch is preferably 4 to 5 m, more preferably 4.5 m; the bottom width of the ditch is preferably 1.5 m, the depth is preferably 1.5 m, and the slope ratio is preferably 1:1.5.

[0032] In this invention, the shrimp larvae breeding area is preferably not dug with deep trenches, but isolated from the adult shrimp farming area by raising the field ridges with soil. If soil is inconvenient to purchase or too expensive, a ring-shaped trench can be dug around the shrimp larvae breeding area according to the actual situation. It is preferable to set up an escape-proof net around the shrimp larvae breeding area. The escape-proof net is preferably 60cm high and preferably embedded 13-1cm in the soil. The corners around the perimeter are preferably constructed in an arc shape. The shrimp larvae breeding area and the adult shrimp farming area are preferably constructed with separate irrigation and drainage systems. The inlet and outlet are preferably equipped with double-layer dense nets to prevent crayfish from escaping and to facilitate the farming needs of crayfish at different stages.

[0033] After the mid-season rice harvest and field improvements are completed, the rice straw in the shrimp larvae breeding area is harvested, leaving a stubble height of 30-50 cm. The harvested rice straw is then crushed and piled up in the shrimp larvae breeding area at intervals of 5-10 m. In this invention, the preferred stubble height of the rice straw in the shrimp larvae breeding area is 40 cm; the preferred spacing between piles is 7 m; and the preferred length of the crushed rice straw in the shrimp larvae breeding area is 8-12 cm, more preferably 10 cm. By leaving a high stubble of rice straw in the shrimp larvae breeding area and piling the crushed rice straw at appropriate intervals, this invention can reduce the degree of straw decay and prevent the water quality from deteriorating too quickly.

[0034] After the rice straw in the shrimp larvae breeding area is piled up, disinfection and irrigation are preferably carried out sequentially in the shrimp larvae breeding area. In this invention, the disinfection reagent preferably includes quicklime; the amount of quicklime used is preferably 100 kg / mu; the disinfection time is preferably 7 to 10 days, more preferably 10 days; the water depth for irrigation is preferably 40 to 50 cm, more preferably 45 cm.

[0035] This invention preferably involves releasing broodstock shrimp for crayfish larvae propagation after irrigation of the shrimp larvae. In this invention, the broodstock shrimp are preferably weighing >30g / shrimp; the preferred stocking density is 35-40kg per acre, more preferably 40kg; the preferred female-to-male ratio is 3-5:1, more preferably 4:1; in winter, the water level is preferably raised to 60-70cm, with increased patrols and timely ice breaking to prevent crayfish from dying due to lack of oxygen.

[0036] After the mid-season rice harvest and field improvement are completed, this invention involves pulverizing all the rice straw in the shrimp farming area and rotary tilling it into the paddy fields. In this invention, the preferred length of the pulverized rice straw in the shrimp farming area is 4-6 cm; rotary tilling is preferably performed in a dry state in the paddy fields of the shrimp farming area (ensuring the machine doesn't get stuck); after rotary tilling, green manure is preferably sown; the preferred varieties of green manure are milkvetch and / or rapeseed, and 2-4 kg of urea is preferably applied per mu (approximately 0.067 hectares); drainage ditches are preferably dug in the field to prevent waterlogging. This invention, by pulverizing the rice straw in the shrimp farming area and rotary tilling it into the paddy fields, can increase the biodecomposition of the straw, prevent large-scale CH4 emissions in the following year, and planting green manure not only provides food and suitable habitat for crayfish in the following year but also increases the biodecomposition of the previous season's straw.

[0037] In March of the following year, the present invention irrigated the adult shrimp farming area and planted aquatic plants, transferring the shrimp larvae from the shrimp larvae breeding area to the adult shrimp farming area for further cultivation. In this invention, the irrigation is preferably carried out 2-3 days before the shrimp larvae transfer, which is beneficial for the crayfish to forage and grow normally; the irrigation depth is preferably 30-40 cm, more preferably 35 cm; when the air temperature rises to 20-25℃, the water depth is preferably increased to 60-80 cm; the row spacing of the aquatic plants is preferably 5-10 m, more preferably 7 m; the plant spacing is preferably 5-10 m, more preferably 7 m; the aquatic plants preferably include one or more of *Hydrilla verticillata*, *Ceratophyllum demersum*, *Eichhornia crassipes*, and *Lemna minor*, more preferably *Hydrilla verticillata*. This invention increases dissolved oxygen and provides food for crayfish by planting aquatic plants.

[0038] After the aquatic plants are planted, this invention preferably involves harvesting shrimp larvae in batches from the shrimp larvae breeding area to the adult shrimp farming area. Harvesting is preferably completed before 12:00 noon on the same day, and larvae of different sizes are preferably released separately to ensure that the size of the shrimp larvae in the crayfish farming area remains relatively uniform. The shrimp larvae density in the adult shrimp farming area is preferably 14,000–15,000 larvae / acre. The weight of the harvested shrimp larvae is preferably 4–7g / larvae; shrimp larvae that do not meet these requirements are still farmed in the breeding area.

[0039] After the shrimp larvae are transferred, this invention preferably involves feeding the adult shrimp farming area at fixed times and locations. In March, the daily feed amount is preferably 2%–5% of the shrimp's body weight, more preferably 3%; in April, it is preferably 4%–7% of the shrimp's body weight, more preferably 5%. Feeding is preferably done twice a day, morning and evening, with the evening feeding being the primary feeding. The specific amount is adjusted according to weather and feeding conditions. After April, when the temperature rises to 20–25℃, the water depth in the farming area is preferably increased to 60–80 cm. Adult shrimp are preferably harvested from the adult shrimp farming area for market in April and May, following the principle of replenishing larger shrimp and leaving smaller ones. After the adult shrimp harvest is completed, shrimp larvae are preferably harvested from the shrimp larvae breeding area and released into the adult shrimp farming area, preferably at a stocking density of 4000 larvae / acre with a size of 200 larvae / kg. Feeding continues in the adult shrimp farming area according to the above method, and all crayfish are preferably harvested for market in June and July. All crayfish are preferably harvested from the shrimp larvae breeding area for market in June and July.

[0040] After all the crayfish have been harvested in June or July, the present invention preferably involves draining the water.

[0041] After draining the paddy field to a depth of 1 cm, the present invention preferably applies fertilizer and then performs rotary tillage, further preferably ensuring that the elevation difference across the entire field is no more than one inch; the fertilizer preferably includes a combination or compound fertilizer of urea, superphosphate, and potassium chloride; the nitrogen, phosphorus, and potassium content of the compound fertilizer is 15:15:15; the application rate of the compound fertilizer is preferably 30-40 kg / mu, more preferably 35 kg / mu; the application rate of the urea is preferably 10-14 kg / mu, more preferably 12 kg / mu; the application rate of the superphosphate is preferably 20-25 kg / mu, more preferably 23 kg / mu; the application rate of the potassium chloride is preferably 10-14 kg / mu, more preferably 12 kg / mu.

[0042] After rotary tillage, the rice seeds are preferably sown directly after settling for 1-2 days. The soil moisture content for direct sowing is preferably 40%-50% of the maximum field capacity, more preferably 45%. Low-lying areas should ideally be free of standing water, and irrigation is preferably not performed after sowing. The method for rice seed germination is not particularly important in this invention; any method well-known to those skilled in the art can be used.

[0043] In this invention, when direct-seeding rice before mid-June, rice varieties with a growth period of less than 135 days are preferred, including Jingliangyou 534 or Tailiangyou 5187. When direct-seeding rice after mid-to-late June, rice varieties with a growth period of less than 120 days are preferred, including Fengyou 9 or Jiuliangyou Huanghuazhan. The preferred amount of rice seeds is 3-4 catties / mu. If there is still significant water accumulation in the paddy field before sowing, it is preferable to drain the water into ditches for temporary storage. Two to three days after sowing, before the rice seedlings emerge, it is preferable to apply pesticides for pre-emergence treatment. If it rains more than 10 mm within one day after spraying, it is preferable to apply pesticides again. The pesticides preferred include one or more of pendimethalin, terbufos, and pretilachlor. It is preferable to spray pesticides at the 3-4 leaf stage for secondary pre-emergence control. If weeds are still present 50 days after sowing, it is preferable to select appropriate pesticides for spot control based on the type of weed. When the rice reaches the two-leaf-one-heart stage, it is preferable to apply 6-7 kg of urea. When the rice reaches the jointing stage, it is preferable to apply 6-7 kg of urea and 10-15 kg of 60% potassium chloride per mu.

[0044] Water management during direct-seeded rice: From direct seeding to the 3-leaf stage, it is best to avoid frequent irrigation in the paddy field. This promotes deep root development and increases the decomposition of straw, feed, and crayfish remains, reducing CH4 emission flux. If obvious cracks appear in the paddy field, it is best to irrigate a small amount of water in the early morning or evening, with the upper limit of irrigation being that there is no obvious water accumulation in the paddy field. During the seedling stage to the early tillering stage, irrigate with a thin layer of water 2-3 cm deep. After there is no obvious water accumulation on the field surface, irrigate again the next day. More preferably, irrigate only after the soil moisture content drops to 80% of field capacity to ensure normal tillering of rice and maintain soil aerobic conditions. When the number of tillers per mu reaches 230,000-270,000 during the peak tillering stage, it is best to completely dry the field for 7-10 days. Intermittent irrigation is used from the jointing stage to the ripening stage to prevent increased CH4 emissions. The preferred method of intermittent irrigation includes: irrigating with a 3-4 cm water layer, followed by dehydration of the paddy field for 1-3 days, and repeating the single irrigation and dehydration. It is recommended to dry the rice fields 7 days before harvest to prevent the rice from lodging due to premature water shortage.

[0045] After the rice harvest, the present invention repeats the above-described technical solution to continue rice-shrimp rotation breeding and separation and direct rice seeding.

[0046] This invention provides a method that combines rice-crayfish rotation with direct rice seeding to achieve soil obstacle reduction and synergistic CH4 emission reduction. By separating breeding and raising, the method allows for rational planning of water and field conditions during the crayfish farming season, reducing the area and duration of winter paddy field flooding, increasing aeration and oxygen content in the paddy fields, reducing secondary gleying and planting obstacles in rice, improving soil quality, and effectively reducing farmers' farming risks. Direct rice seeding during the rice season increases the biodecomposition of unused organic materials such as straw feed from crayfish, reducing anaerobic decomposition by methanogens, and effectively reducing CH4 emissions. For crayfish, this reduces farming risks and increases farmers' income. For rice, it increases rice planting area, thereby increasing rice yield and reducing labor input. Regarding CH4, reducing winter paddy field flooding promotes the biodecomposition of rice straw, and direct seeding the following year increases the biodecomposition of feed and crayfish excrement, reducing CH4 emission risks.

[0047] To further illustrate the present invention, the following detailed description, in conjunction with the accompanying drawings and embodiments, describes a method for reducing soil planting obstacles and CH4 emissions in rice-shrimp paddy fields provided by the present invention, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0048] Example 1

[0049] A method for reducing soil planting obstacles and methane emissions in rice-shrimp paddy fields comprises the following steps:

[0050] Step 1: Transformation of Separate Breeding and Aquaculture Areas. Select paddy fields with abundant, unpolluted water sources, flat terrain, convenient irrigation and drainage, and easy access. Transformation will be carried out after the mid-season rice harvest in October or November. The paddy fields will be divided into a shrimp larvae breeding area and an adult shrimp farming area, with an area ratio of 1:5. The shrimp larvae breeding area will not have deep ditches dug; instead, it will be separated from the adult shrimp farming area by raised earthen embankments. These embankments will be 1m above the paddy surface, 1.5m wide, and have a slope ratio of 1:1.5. Escape-prevention nets will be installed around the shrimp larvae breeding area, with a height of 60cm and a depth of approximately 15cm in the soil. The bends at the edges will be constructed in an arc shape. A separate irrigation and drainage system will be constructed for the shrimp larvae breeding area, with double-layered dense netting at the inlet and outlet to prevent shrimp escape. The adult shrimp farming area will not require deep ditches; a separate irrigation and drainage system and escape-prevention nets will be installed.

[0051] Step Two: Winter Straw and Water Management in Different Breeding and Separation Areas: After the mid-season rice harvest and field improvements are completed, rice straw in the shrimp larvae breeding area should be left with a 40cm high stubble, and the remaining straw should be shredded to about 10cm and piled evenly at 7m intervals in the shrimp larvae breeding area. Disinfect and remove impurities with 100kg of quicklime per mu (approximately 0.067 hectares). After disinfection, slowly irrigate, maintaining a water layer of 40cm. After irrigation for shrimp larvae breeding, stock broodstock shrimp for crayfish larvae breeding. Stock 35kg of broodstock shrimp (30g / tail or larger) per mu, with a female-to-male ratio of 4:1. In winter, raise the water level to 60cm, increase patrols, and promptly break ice to prevent crayfish from dying due to lack of oxygen. In the shrimp larvae breeding area, after rice harvest, wait until the soil moisture content drops to 25%–30% (to avoid trapping machinery), then shred weeds, rice stubble, and all straw (shredded to a length of 5cm) and incorporate them into the paddy field. Appropriate sowing of purple clover is possible, along with an appropriate application of about 3kg of urea per mu. Drainage ditches should be dug in the fields to prevent waterlogging.

[0052] Step 3: Spring Crayfish Farming and Water Management: In March of the following year, the crayfish farming area will be irrigated to a depth of 40m, with *Hydrilla verticillata* planted at 10m intervals. At this time, crayfish larvae will be harvested from the breeding area and transferred to the farming area in batches, with harvesting completed before 12 noon each day. They should be released separately according to different sizes to ensure a relatively uniform size of the larvae in the farming area. The final density of crayfish in the farming area will be approximately 14,000 larvae per acre (about 5g each). Larvae that do not meet the requirements will remain in the breeding area. After the larvae transfer is complete, feed will be provided to the farming area at fixed times and locations. In March, the daily feed amount will be 3% of the crayfish's body weight, increasing to 6% in April. Feeding will be done twice a day, morning and evening, with the evening feeding being the primary feeding. The specific amount will be adjusted according to weather and feeding conditions. After April, once the temperature rises to 22℃, the water depth in the farming area can be increased to 80cm. Adult crayfish will be harvested and marketed from the farming area in April and May, with the principle of harvesting larger crayfish and leaving smaller ones. After the adult shrimp harvest in the aquaculture area is completed, shrimp larvae will be harvested from the breeding area and released into the aquaculture area at a stocking density of 4,000 larvae per acre (200 larvae per kg). Feed will continue to be provided to the aquaculture area using the same method described above. All crayfish will be harvested and marketed in June or July. Similarly, all crayfish from the breeding area will be harvested and marketed in June or July.

[0053] Step 4: Direct-seeding rice fertilization, sowing, and pesticide management; After all crayfish are harvested in June and July, drain the water and directly sow rice. The soil moisture content should be 50% of the maximum field capacity, and there should be no standing water in low-lying areas. Do not irrigate after sowing. If directing before mid-June, choose varieties with a growth period of less than 135 days; if directing after mid-to-late June, choose varieties with a growth period of less than 120 days. After draining the paddy field to a depth of 1 cm, apply 40 kg of compound fertilizer with a nitrogen-phosphorus-potassium content of 15-15-15 per mu (approximately 0.067 hectares) and rotary till the paddy field, ensuring that the height difference across the entire field is no more than one inch. After tilling, allow the soil to settle for 1-2 days, then select treated and germinated seeds for sowing, using 4 jin (approximately 2 catties) of seeds per mu (approximately 0.067 hectares). If there is still significant standing water in the paddy field before sowing, drain it into ditches for temporary storage. 2-3 days after sowing, before the rice seedlings emerge, apply a suitable herbal remedy for pre-emergence treatment. If it rains more than 10 mm within one day after application, re-apply the herbal remedy. Spray pesticides at the 3-4 leaf stage for a second round of weed control. If weeds are still present 50 days after sowing, select appropriate pesticides for spot control based on the type of weed. When the rice reaches the two-leaf-one-heart stage, apply 7 kg of urea per mu. When the rice reaches the jointing stage, apply 7 kg of urea and 12 kg of 60% potassium chloride per mu.

[0054] Step 5: Water Management During Direct Seeding of Rice; From direct seeding to the 3-leaf stage, avoid frequent irrigation of the paddy field. If obvious cracks appear, irrigate a small amount of water in the early morning or evening, ensuring there is no significant standing water. During the seedling stage to the early tillering stage, irrigate with a thin layer of water (2-3 cm). Irrigate again the next day after there is no significant standing water. When the tillering peak reaches approximately 250,000 tillers per acre, completely dry the field for 7 days. From the jointing stage to the ripening stage, use intermittent irrigation. The intermittent irrigation rule is: alternate between a thin water layer and dry water, irrigating with a 3-4 cm water layer each time, followed by 3 days of wetting and dehydration of the paddy field, and repeating this cycle. Dry the field 7 days before harvest, avoiding premature watering to prevent lodging of the rice.

[0055] Example 2

[0056] A method similar to Example 1, except that the isolation method in step one is as follows: dig a circular ditch around the shrimp larvae breeding area, with the opening of the circular ditch being 4-5m wide, the bottom of the ditch being 1.5m wide, the depth being 1.5m, and the slope ratio being 1:1.5.

[0057] Comparative Example 1

[0058] A conventional rice-crayfish rotation system and its operational methods are as follows: The rice-crayfish field is surrounded by a ring ditch, which occupies 20% of the total field area. After the mid-season rice harvest in October or November, the straw is left with a 40cm high stubble, and the remaining straw is shredded and spread into the field. Two weeks after rice harvest, the water level is raised to 30cm, and crayfish fry are introduced for breeding (if there are sufficient crayfish fry in the ditches, no additional fry are introduced). Feed is introduced into the rice-crayfish field starting in March, and the irrigation depth is increased. After all crayfish have been harvested in May or June, the water level is drained, maintaining a surface water depth of 3cm. Two days before rice transplanting, fertilizer is applied to the field with a thin layer of water (same as in Example 1), and the field is rotary tilled. Continuous irrigation is maintained during the rice growing season. Except for mid-season drying and drying one week before harvest, the field maintains a distinct water layer.

[0059] Test Example 1

[0060] On October 15, 2021, in Qianjiang, Hubei Province, rice-shrimp rotation was implemented using the methods of Example 1 (rice-shrimp breeding and rearing separation) and Comparative Example 1 (traditional rice-shrimp rotation). The rice variety planted was Jiuliangyou Huanghuazhan. Soil gleying index content in both topsoil and non-topsoil layers was determined using the potassium dichromate oxidation method, o-phenanthroline titration method, potassium permanganate oxidation method, and ORP instrument. The results are shown in Table 1. The CH4 emission rate (methane emission flux) and cumulative CH4 emission during the rice season (total methane emission) were measured at different time points using the static chamber method. The results are shown in Table 1. Figure 1 .

[0061] Table 1. Soil gleying index content in the topsoil and non-topsoil layers of traditional rice-crayfish rotation and rice-crayfish breeding areas.

[0062]

[0063] As shown in Table 1, this method can reduce the degree of soil gleying, particularly in the topsoil, by reducing the levels of reducing substances, active reducing substances, and Fe. 2+ They can reduce [reductions] by 45%, 76%, and 83% respectively, and Eh can be increased by 385.3 mv. Non-tilled layer reducing substances, active reducing substances, and Fe [are involved]. 2+ They can reduce by 69%, 93%, and 95% respectively, and Eh can increase by 344mv.

[0064] Depend on Figure 1 It can be seen that, compared with the traditional rice-shrimp system, the cumulative CH4 emissions can be reduced by 49% after separating breeding and rearing and direct seeding of rice. The largest reduction was observed during the greening and jointing stage, at 84%. The reduction was 26% during the jointing to booting stage and 66% during the milk stage to maturity stage.

[0065] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for reducing soil planting obstacles and methane emission in rice-shrimp field, characterized in that, It consists of the following steps: 1) After rice harvest, the rice field is divided into a prawn fry breeding area and a prawn breeding area; the area ratio of the prawn fry breeding area to the prawn breeding area is 1:5; the prawn fry breeding area is not dug with deep ditches, and is isolated from the prawn breeding area by raising the earth embankment; 2) The rice straws in the prawn fry breeding area are harvested, leaving stubble 30-50 cm high, the harvested rice straws are crushed and then piled up in the prawn fry breeding area at intervals of 5-10 m, and prawn fries are bred in the prawn fry breeding area; all the rice straws in the prawn breeding area are crushed and then rotary plowed into the rice field in the prawn breeding area; 3) In March of the next year, the prawn fries in the prawn fry breeding area are transferred to the prawn breeding area for breeding after the prawn breeding area is irrigated and waterweeds are planted; after all the crayfish and prawn fries in the rice field are caught in June-July, rice is directly sown in the whole rice field; the row spacing of the waterweeds is 5-10 m, and the plant spacing is 5-10 m; the density of the prawn fries in the prawn breeding area is 14,000-15,000 per mu; 4) After the rice is directly sown, when cracks appear in the rice field, a small amount of water is irrigated, and the upper limit of the irrigation is that there is no water accumulation in the rice field; 2-3 cm of thin water is irrigated during the rice seedling stage to the early tillering stage, and 2-3 cm of thin water is irrigated again the next day when the water holding capacity of the rice field is <80%; when the number of tillers per mu reaches 230-270 million during the tillering stage, the rice field is completely dried for 7-10 days; intermittent irrigation is adopted during the jointing stage to the maturity stage; 5) After the rice is harvested, steps 1)-4) are repeated; When breeding prawn fries, 35-40 kg of parent prawns are raised per mu, and the ratio of females to males is 4:

1.

2. The method of claim 1, wherein, The waterweeds include one or more of Hydrilla verticillata, Ceratophyllum demersum, Eichhornia crassipes, and Lemna.

3. The method of claim 1, wherein, When the rice is directly sown before mid-June, a rice variety with a growth period <135 days is selected; when the rice is directly sown after mid-June, a rice variety with a growth period <120 days is selected.

4. The method of claim 1, wherein, The method of intermittent irrigation includes that after a single irrigation of 3-4 cm of water layer, the rice field is dehydrated for 1-3 days, and the single irrigation and dehydration are repeated.

5. The method of claim 1, wherein, The rice field is dried for 7-10 days before the rice is harvested.

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