Large-scale river crab breeding method of rice-crab symbiotic system

Abstract

The invention relates to the technical field of crop planting and aquaculture, in particular to a large-scale river crab breeding method of a rice-crab symbiotic system. The breeding method comprises the steps that an outer circular groove is dug around the periphery of a rice field block, and an inner dam ridge is built between the outer circular groove and the rice field block and around the periphery of the rice field block; after the larval crabs and the outer circular grooves are sterilized, water is injected into the outer circular grooves, the larval crabs are stocked in the outer circular grooves, feeding is conducted every day, and water quality is regulated and controlled regularly; during ploughing, applying whole-course fertilizer to the rice field blocks, injecting water into the rice field blocks, sealing the weeding period, adjusting the inner dam ridges, shoveling a section of the inner dam ridges at certain intervals before rice transplanting, transplanting rice seedlings into the rice field, and harvesting adult crabs after the rice is mature. According to the method, through optimal configuration of the water area space of the crab breeding engineering in the crab breeding rice field, larval crabs are bred in advance, the growth period is prolonged by 2-3 months, the shelling frequency is increased by 1-2 times, and the weight and the size of adult crab individuals are increased by 50%-100%.

Description

Technical Field

[0001] The present invention relates to the technical field of crop planting and aquaculture, and more particularly to a method for breeding large-scale river crabs in a rice-crab symbiotic system. Background Art

[0002] In the practical implementation of integrated rice-crab farming, there has always been an irreconcilable conflict between early crab stocking and rice fertilization and herbicide application. In northern China, where irrigation water resources are abundant, crabs can begin to feed and grow normally in late March and early April, when water temperatures stabilize above 10°C. Early stocking can increase crab molting times, boost the yield of large crabs, and boost farmers' incomes. Conventional rice-crab farming in northern China involves constructing embankments around the paddies and digging crab trenches between them when establishing a rice-crab symbiosis. Because the use of chemical fertilizers and pesticides during rice growth significantly impacts crab production, crabs are typically stocked in paddies two weeks after rice fertilization and chemical weed control are completed, or one week after rice transplanting (early June). This severely limits the crab stocking timeframe, resulting in lower crab quality and underweight adult crabs. Summary of the Invention

[0003] In response to the above technical problems, the present invention provides a technical method for breeding large-scale river crabs based on a deep ditch and high ridge layout in the field under a rice-crab symbiosis model.

[0004] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0005] The first aspect of the present invention provides a rice-crab symbiotic breeding system, comprising a plurality of rice field blocks, an inner dam ridge being provided around the outer periphery of the rice field blocks, and an outer ring ditch being provided around the outer periphery of the inner dam ridge; after a closed period of applying fertilizers and spraying herbicides, the inner dam ridge is adjusted, and a portion of the height of the inner dam ridge is shoveled away at regular intervals.

[0006] In a preferred embodiment, the outer ring ditch has a width of 1.2 to 1.8 m, a depth of 0.6 to 0.8 m, and a slope of ≤30°.

[0007] In a preferred embodiment, before adjustment, the width of the inner dam bank is 30-40 cm and the height is 30-35 cm. After adjustment, the height of the adjusted portion of the inner dam bank is ≤15 cm.

[0008] In a preferred embodiment, anti-escape facilities are provided on the periphery of the outer ring ditch.

[0009] A second aspect of the present invention provides a method for breeding large crabs based on the above system, comprising the following steps:

[0010] An outer ring ditch is dug around the periphery of the rice field block, and an inner dam ridge is built around the periphery of the rice field block between the outer ring ditch and the rice field block; after the crabs and the outer ring ditch are sterilized, water is injected into the outer ring ditch, and the crabs are released into the outer ring ditch, fed every day, and the water quality is regularly adjusted; when cultivating the land, full-course fertilizer is applied to the rice field block, water is injected into the rice field block, and after the closed period of pesticide application, the inner dam ridge is adjusted, and part of the height of the inner dam ridge is shoveled away at a certain distance, and rice seedlings are transplanted into the rice field. After the rice is mature, the crabs are harvested.

[0011] Under the optimal solution, 2~6hm 2 For a breeding unit, the total area of ​​the outer ring ditch accounts for 6% to 8% of the breeding unit, and escape prevention facilities are installed on the outer periphery of the outer ring ditch.

[0012] Under the preferred plan, crabs are stocked starting from late March to early April, with a stocking density of 400 to 500 crabs per mu. Before mid-to-late August, crabs are fed once every evening. After late August, crabs are fed once in the morning and evening every day. The total crude protein content of the feed is ≥40%, and the crude fiber content is ≤15%; among them, animal protein accounts for more than 60% of the total crude protein, and plant protein accounts for less than 40%.

[0013] Under the preferred option, the harvested adult crabs are intensively fattened for about 2 to 3 weeks.

[0014] Under the optimal solution, when applying full-course fertilizer, apply the full-course fertilizer deeply into the 10-15 cm tillage layer of the rice field, and apply 40-50 kilograms per mu; before transplanting, cultivate rice seedlings in pots and trays in a greenhouse; when transplanting, use a special pot and tray seedling throwing machine for transplanting, and adopt a more open planting agronomic measure, with one ridge left empty for every 12 ridges of rice seedlings transplanted, and about 10,000 to 12,000 holes planted per mu, with 3 to 5 rice seedlings transplanted in each hole.

[0015] Beneficial effects of the present invention:

[0016] By optimizing rice field engineering and integrating agronomic management measures, the present invention solves the problem of crabs being harmed by the early release of river crabs into rice fields and the application of fertilizers and pesticides to rice. By optimizing the spatial configuration of the crab-raising rice field breeding project, a "deep ditch and high ridge" rice-crab farmland engineering layout is created, achieving the goal of releasing crabs into rice fields in mid-to-late March. By allocating high-quality river crab bait and scientifically feeding, the crabs are released early and intensively, ultimately extending the crab-raising period by 2 to 3 months, increasing the number of molting by 1 to 2 times, and achieving a 50% to 100% increase in the weight and volume of adult crabs. By integrating other agronomic management measures, a rice-crab symbiotic ecological breeding model of "deep ditch and high ridge, early release and intensive breeding, ecological pest control, and planting in the absence of air" is finally formed, providing technical support for promoting green ecological agriculture and increasing farmers' income. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the "deep ditch and high ridge" rice-crab farmland of the present invention;

[0018] Figure 2 This is the actual situation in the field of the dam ridge (deep ditch and high ridge) in the outer ring ditch of the present invention;

[0019] Figure 3 This is the actual situation in the field where part of the inner dam ridge is leveled by the present invention;

[0020] Figure 4 This is the actual situation of high-quality large-sized crab farming in the field in Example 1 of the present invention;

[0021] Figure 5 This is a comparison chart of the weight growth of the large-sized crabs of the present invention and conventional crabs;

[0022] Figure 6 This is an actual measurement diagram of a large-sized adult crab according to Example 1 of the present invention.

[0023] In the picture, 1-outer ring ditch; 2-inner dam ridge; 3-rice field. DETAILED DESCRIPTION

[0024] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0025] In the present invention, unless otherwise specified, the scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. The experimental methods in the examples are conventional methods unless otherwise specified. Where specific conditions are not specified in the examples, the experiments were carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, for which the manufacturer is not specified, are all commercially available conventional products.

[0026] Overview of the Invention

[0027] (1) Selection of rice-crab symbiotic fields

[0028] Choose fields with sufficient water sources, convenient irrigation and drainage, unpolluted water quality, and that meet fishery water quality standards, with convenient transportation and strong water retention capacity, especially the ridges must be solid and leak-proof.

[0029] (2) Construction of rice-crab symbiotic fields

[0030] The field project was rationally designed and scientifically constructed based on the ecological and environmental requirements of the rice-crab symbiosis and aquaculture techniques. The main project involved building a deep outer ring ditch for early crab release and rearing, and reinforcing the inner ridges (raised ridges) to isolate the crab ditch waters from the rice fields.

[0031] 1. Construction of outer ring ditch (deep ditch)

[0032] For fields with larger rice-crab breeding areas (≥1hm 2 ), a circular breeding ditch mode can be adopted, usually 2 to 6hm 2 For each paddy unit, a circular breeding ditch 1.2-1.8m wide and 0.6-0.8m deep relative to the paddy field is excavated around the paddy field. The outer ring ditch's total area accounts for 6-8% of the paddy unit's area, and the slope should be ≤30°. A steeper slope can easily cause crab burrows and collapse. The outer ring ditch needs to be re-maintained annually before harvest to ensure it meets crab farming requirements. It can also be constructed from natural ditches at the head of a field or from drainage channels in the paddy field.

[0033] 2. Construction and adjustment of inner dam embankment (high ridge)

[0034] While the outer ring ditch is being constructed, an inner embankment is built around the inner side of the outer ring ditch, close to the rice paddies. The inner embankment is 30-40 cm wide and 30-35 cm high. It serves primarily to isolate the waters within the ring ditch from the paddy fields during early crab farming, preventing damage to the crabs from fertilizer and pesticide spraying in the paddy fields. Furthermore, the inner embankment protects the topsoil of the paddy fields, especially during spring harrowing, by preventing mud from flowing into the ring ditch, thus reducing the amount of work required to repair the ring ditch the following year. When reinforcing the inner embankment, large clumps of soil must be crushed and compacted securely. No gaps should be left in the embankment, as this would cause water and fertilizer leakage from the paddy fields and allow crabs to escape. After applying fertilizer throughout the process and sealing treatment for weed control, the inner dam ridge is adjusted before transplanting rice seedlings. By leveling part of the inner dam ridge, the height of the inner dam ridge is reduced to less than 15 cm or to the same level as the rice field, so that the water area in the outer ring ditch is integrated with the water area of ​​the rice field, increasing the activity space for river crabs, and achieving true symbiosis between rice and river crabs, thereby solving the contradiction between early release and early raising of river crabs and fertilizing and weeding rice.

[0035] 3. Construction of water supply and drainage system

[0036] The inlet and outlet are installed within the outer ring ditch, with pipes installed at the inlet. The pipes are wrapped with mesh tape. The mesh size is determined based on the size of the crabs to prevent small water flows during inlet and outlet flow from escaping the crabs. For paddy field irrigation, separate inlet and outlet pipes are no longer required; paddy field flooding and irrigation are completed using the water from the outer ring ditch. When the outer ring ditch is full, an inlet is dug in a low-lying area of ​​the inner dam bank to divert water into the paddy fields. Once the water level reaches the required level, the inlet is then blocked.

[0037] 4. Construction of escape prevention facilities

[0038] Choose appropriate materials for escape prevention based on the specific conditions of your paddy fields and your own economic situation. Currently, calcium-plastic board and plastic film are commonly used in northern China. Calcium-plastic board has excellent escape prevention performance but is slightly more expensive, while agricultural plastic film escape prevention walls are inexpensive and easy to repair and reinforce.

[0039] (3) Large-scale river crab farming technology

[0040] 1. Crab selection

[0041] The crab species released into rice fields in the northern region is Chinese mitten crab. Large and healthy seedlings are selected, with uniform size, strong physique, active crawling, and no disease or injury. The size of the crabs is controlled at 50 to 70 per kilogram.

[0042] 2. Crab stocking and breeding

[0043] The optimal time for stocking crabs is from late March to early April, extending the adult crab growth period by approximately two months compared to conventional crab farming. Research on the interaction between adult crab stocking density and rice yield suggests a suitable field stocking density of 400-500 crabs per mu (approximately 1.5 acres). Once the outer ring ditch reaches a depth of 30-40 cm, transfer the crabs from the wintering pond to the outer ring ditch. Before stocking, thoroughly clean the outer ring ditch with quicklime and other chemicals. Then, soak the crabs in 4% salt water for 5-8 minutes to eliminate parasites and pathogens in the ditch and on the crabs. Feeding is based on feeding high-quality compound bait, with a total crude protein content of ≥40%, of which animal protein (fish meal, shrimp meal, silkworm pupa powder, etc.) accounts for more than 60%, and plant protein (soybean meal, peanut meal, etc.) accounts for less than 40%; crude fiber (wheat flour, corn flour, bran, etc.) content ≤15%; fat (fish oil, soybean oil, rapeseed oil, soybean lecithin, etc.) accounts for ≤6%; mineral (calcium, phosphorus, iron, zinc, potassium, etc.) element content ≤5%. Before mid-to-late August, feed the crabs once daily in the evening. Increase the amount of feed as they grow and consume more food. Observe the remaining bait on the shore to ensure the crabs have just enough to eat or have a little left over. After late August, feed the crabs twice daily: once in the morning and once in the evening. In mid-to-early September, as adult crabs gradually come ashore, harvesting and centralized fattening begin. This centralized fattening period should last for two to three weeks. Appropriately increase the proportion of animal protein and fat in the feed, such as increasing animal protein to 70%, reducing plant protein to 30%, and increasing fat to 8 to 10%. Alternatively, use specialized fattening feed, feeding the crabs once daily in the evening at a rate of 5 to 8% of their body weight, ideally ensuring they consume the food within two to three hours. After fattening, the crabs are ready for market, with the average adult size exceeding 118 grams.

[0044] 3. Water quantity control and water quality regulation

[0045] Maintain fresh water quality in the ditch and paddy fields through water exchanges. Biological agents are regularly used to regulate water quality and maintain adequate dissolved oxygen. Quicklime can also be applied regularly, generally once a month, at a rate of 8 to 10 kilograms per mu. To ensure the safe growth of river crabs, maintain a water level of 5 to 10 cm during the rice seedling stage, increase it to 15 to 20 cm during the tillering stage, and reduce irrigation to 5 to 10 cm during maturity. No drainage is allowed during the rice-crab symbiosis period. Once the crabs are captured, no irrigation is allowed, allowing the fields to dry naturally.

[0046] (4) Rice supporting cultivation measures

[0047] 1. Variety selection and transplanting

[0048] Select high-quality rice varieties with a long growth period, strong tillering ability, high yield, fertilizer tolerance, lodging resistance, disease and pest resistance, and waterlogging tolerance, with upright leaves and a compact plant shape, such as the Yanfeng and Yanjing series. Seedlings are cultivated in pots and trays in greenhouses and transplanted using a dedicated pot and tray transplanter. Agronomic practice of "empty planting" is employed: for every 12 rows of rice seedlings transplanted, one row is left empty. This increases the space for the rice seedlings to move and increases the marginal effect of rice growth. Generally, 10,000 to 12,000 holes are planted per mu, with 3 to 5 seedlings per hole.

[0049] 2. Safe fertilization measures

[0050] The optimal economic fertilizer rate is determined by combining soil testing recommendations with target yield fertilization. A stable fertilizer (N-P2O5-K2O, 26%-10%-12%) that is safe for crab farming and meets the nutrient requirements of rice is used as a full-season fertilizer, with a dosage of 40-50 kg per mu. This fertilizer should be applied deep into the 10-15 cm tillage layer during the tillage before transplanting, and topdressing should be avoided as much as possible. In special circumstances, such as yellowing of rice leaves during the heading period, urea (3-5 kg / mu) can be applied as a topdressing to stabilize rice yields, provided it does not affect crab growth.

[0051] 3. Safe weed control measures

[0052] And choose high-efficiency and low-toxic herbicides, ensure that the soil within the dam ridge in the field is sealed, and before transplanting rice five days later, wait until the efficacy of the herbicide is sharply reduced before removing part of the inner dam ridge to achieve rice-crab symbiosis.

[0053] Example 1

[0054] like Figure 1 As shown, a rice-crab symbiotic breeding method comprises the following steps:

[0055] Construction of rice-crab symbiotic breeding system:

[0056] Sa1. With 4hm 2For a planting and breeding unit, a circular ditch planting and breeding model is adopted. A circular breeding ditch is dug around the rice field, namely the outer ring ditch. The width of the outer ring ditch is 1.2-1.8m, the depth is 0.6-0.8m, and the slope is 25±5°. The total area of ​​the outer ring ditch accounts for 6%-8% of the planting and breeding unit area.

[0057] Sa2. Build an inner embankment between the outer ditch and the paddy field, surrounding the paddy field. The inner embankment should be 30-40 cm wide and 30-35 cm high. Once completed, compact the soil firmly to eliminate any gaps in the inner embankment.

[0058] Sa3. Set up water inlets and drainage outlets on the side walls of the inner and outer dam banks of the ring ditch, and install water inlet and drainage pipes in the water inlets and drainage outlets. Pour and compact the gap between the pipes and the inner dam bank with cement. Wrap mesh belts around the ends of the inlet and drainage pipes according to the size of river crabs, and set up plastic film escape prevention walls around the outer dam bank of the outer ring ditch.

[0059] Rice-crab symbiotic farming:

[0060] Sb1. In mid-April, use quicklime to disinfect the outer ditch to eliminate pathogenic bacteria in the ditch. After disinfection and sterilization, water is injected into the outer ditch. 500 large-sized crabs weighing 12±2g are selected and soaked in 4% salt water for 5-8 minutes to eliminate parasites and pathogenic bacteria in the ditch and on the crab bodies. After disinfection and sterilization, water is injected into the outer ditch and the crabs are released into the outer ditch. They are fed once a day in the evening and the water quality is adjusted regularly to keep the water fresh. High-quality bait is selected to feed the crabs. The total crude protein content of the high-quality bait is 50%-55%, the crude fiber content is 12%-14%, the fat content is 3%-5%, and the mineral element content is 2%-4%. Of the total crude protein, animal protein accounts for 60%-65% and plant protein accounts for 35%-40%.

[0061] In late Sb2.5, during rotary tillage, apply the full-process fertilizer for rice deeply into the tillage layer of the paddy field at one time, with a fertilizer rate of 40-50 kg per mu. Pour water into the paddy field. Before and after transplanting, flatten a section of the inner dam ridge at a certain interval to connect the outer ring ditch with the water area in the paddy field. Use a special pot tray transplanter to transplant the rice seedlings cultivated in the greenhouse into the paddy field. For each rice planting, plant 12 ridges of seedlings and leave one ridge empty. Plant about 10,000 to 12,000 holes per mu, with 3-5 seedlings in each hole. To ensure the safe growth of river crabs, keep the field water level at 5-10 cm during the rice seedling stage, increase it to 15-20 cm during the tillering stage, and reduce irrigation to 5-10 cm during the maturity stage. Do not drain water during the rice-crab symbiosis period. After the river crabs are caught, no more irrigation is done and the water is left dry naturally.

[0062] Sb3. After late August, increase the frequency of feeding crabs to twice a day, once in the morning and once in the evening. In mid-to-early September, when the adult crabs come ashore one after another, catch and harvest the crabs and concentrate on fattening them for 2 to 3 weeks.

[0063] Example 2

[0064] This embodiment is basically the same as embodiment 1, except that the size of the stocked crabs is large-sized crabs weighing 9±2g.

[0065] Example 3

[0066] This embodiment is basically the same as Example 1, except that the specification of the stocked crabs is regular crabs weighing 6±1g.

[0067] Example 4

[0068] This embodiment is basically the same as embodiment 1, except that the specification of the stocked crabs is regular crabs weighing 4±1g.

[0069] Comparative Example 1

[0070] This comparative study employed a traditional rice-crab farming model with 750 standard-sized crabs per mu (approximately 1.5 acres) stocked in early June and fed with standard feed (main nutrients such as 30%-35% protein, ≤5% fat, and 20%-30% crude fiber) until harvest. The farming model was referenced in (Chen Xiaoyun et al., Effects of Ecological Rice-Crab Farming on Soil Fertility and Production Efficiency. Soil Bulletin, 2021).

[0071] Table 1 Survey on reproductive indicators of crabs of different sizes

[0072]

[0073] Note: Treatment A involves the "outer ditch within embankment" farming model, with 500 large crabs per mu stocked in mid-April and fed with high-quality feed until harvest. Treatment B involves the "outer ditch within embankment" farming model, with 500 standard crabs per mu stocked in mid-April and fed with high-quality feed until harvest. Treatment C (CK) involves the "traditional rice-crab" farming model, with 750 standard crabs per mu stocked in early June and fed with standard feed until harvest. Surveys will be conducted on the 14th of each month in 2022 and the 20th of each month in 2023.

[0074] As shown in Table 1 and Figure 5 As shown, the experimental results show that the average weight of river crabs raised by the method specified in the present invention reaches more than 118 grams per crab, and the proportion of river crabs weighing more than 118 grams accounts for more than 65.73%. The specifications of river crabs produced by conventional rice-crab farming are increased by more than 50%, and the selling price and market competitiveness of river crabs are significantly improved.

[0075] The present invention solves the problem of damage to river crabs caused by chemical fertilizer application and pesticide weeding by creating a "deep ditch and high ridge" rice-crab farm field engineering layout, prolongs the field growth cycle of river crabs, increases the number of river crab molting times by at least one, and ensures that 70% of the output river crabs reach a specification of 115g or more.

[0076] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A rice-crab symbiotic breeding system, characterized in that: The method comprises a plurality of rice field blocks, wherein inner dam ridges are arranged around the four sides of the rice field planting area, and an outer ring ditch is arranged around the outer periphery of the inner dam ridges; before transplanting rice seedlings at the end of the closed period of applying full-course fertilizers, the inner dam ridges are adjusted to be basically connected with the field surface, and a section of the remaining inner dam ridges is shoveled away at a certain interval to select a part of the height of the channel to be leveled.

2. The rice-crab symbiotic breeding system according to claim 1, characterized in that: The width of the outer ring ditch is 1.2~1.8m, the depth is 0.6~0.8m, and the slope is ≤30°.

3. The rice-crab symbiotic breeding system according to claim 1, characterized in that: Before adjustment, the width of the inner dam ridge is 30-40 cm and the height is 30-35 cm. After adjustment, the height of the adjusted part of the inner dam ridge is ≤15 cm.

4. The rice-crab symbiotic breeding system according to claim 1, characterized in that: Anti-escape facilities are provided on the periphery of the outer ring ditch.

5. A method for breeding large-sized crabs based on the system according to any one of claims 1 to 4, characterized in that: The steps include: An outer ring ditch is dug around the periphery of the rice field block, and an inner dam ridge is built around the periphery of the rice field block between the outer ring ditch and the rice field block; after the crabs and the outer ring ditch are sterilized, water is poured into the outer ring ditch, and the crabs are released into the outer ring ditch, fed every day, and the water quality is regularly adjusted; when cultivating the land, full-process fertilizer is applied to the rice field block, water is poured into the rice field block, and after the full-process fertilizer is applied and the weeding period is closed, the inner dam ridge is adjusted before transplanting rice seedlings, and part of the height of the inner dam ridge is shoveled away at a certain interval, and the rice seedlings are transplanted into the rice field. After the rice is mature, the crabs are harvested.

6. The method according to claim 5, characterized in that Take 2~6 hm2 as a breeding unit, the total area of ​​the outer ring ditch accounts for 6%~8% of the breeding unit, and escape prevention facilities are installed around the outer ring ditch.

7. The method according to claim 5, characterized in that Crabs are stocked from late March to early April, with a density of 400 to 500 crabs per mu. Before mid-to-late August, they are fed once a day in the evening. After late August, they are fed once a day in the morning and evening. The total crude protein content of the feed is ≥40%, and the crude fiber content is ≤15%. Among them, animal protein accounts for more than 60% of the total crude protein, and plant protein accounts for less than 40%.

8. The method according to claim 5, characterized in that The harvested adult crabs are concentratedly fattened for about 2 to 3 weeks.

9. The method according to claim 5, characterized in that When applying fertilizer, apply the entire fertilizer deep into the 10-15cm tillage layer of the rice field, and apply 40-50 kg per mu; before transplanting, cultivate rice seedlings in pots and trays in a greenhouse; when transplanting, use a special pot and tray seedling throwing machine to transplant the seedlings, and adopt the agronomic measure of empty planting, that is, leave one ridge empty for every 12 ridges of rice seedlings transplanted, and plant about 10,000 to 12,000 holes per mu, with 3 to 5 rice seedlings transplanted in each hole.

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