CATDOLL : CATDOLL: How to cultivate crabs in rice fields and what should we pay attention to?

How to cultivate crabs in rice fields and what should we pay attention to?

In addition to the basic infrastructure engineering of crab farming in rice fields, the following technical keys should also be grasped:

(1) Field cleaning and disinfection

After the field is repaired, 30-35 kg of quicklime per mu is soaked into an emulsion and sprinkled over the field to kill pests and bacteria and replenish calcium. If the field is saline-alkali land, bleaching powder should be used for disinfection to make the concentration of bleaching powder in the field water 20ppm.

(2) Planting rice

For crab-raising rice fields, it is advisable to select high-yield single-season rice varieties with strong fertilizer tolerance, hard straw, not easy to fall over, and strong disease resistance. It is best to use the no-tillage direct seeding method to reduce the amount of floating mud in the field. For transplanting, wide rows and dense plants should be planted, and the planting density around the ditch should be appropriately increased to give full play to its marginal advantages, increase yields, and prevent ditch wall collapse.

(3) Stocking large crab species at the right time

For rice sown by direct seeding, after the three-leaf stage, and for rice planted by transplanting, 7 to 10 days after transplanting, select large crabs of uniform size and weighing 20 to 30 grams, and release 300 to 500 crabs per mu.

(4) Rice cultivation management

① Fertilization

Organic fertilizers are mainly used. On the premise of applying sufficient base fertilizer, cake residue is usually the best topdressing fertilizer. Reduce the number of topdressing as much as possible, especially the number and amount of chemical fertilizers. When it is determined that chemical fertilizers are needed as topdressing, urea should be used instead of ammonium carbonate, and the amount per mu should be controlled within 7.5 to 10 kilograms each time.

② Water slurry management

For crab-raising rice fields, the field surface must always be kept 3 to 5 cm deep in water, and the water level should not be changed arbitrarily or the field should be dehydrated and baked. If it is necessary to bake the field, the water level can only be lowered until there is no water on the field surface. It can also be baked lightly in batches to prevent the water body from being too small and affecting the growth of river crabs.

③ Take precautions

River crabs are more sensitive to the toxicity of pesticides than fish, so the use of pesticides that are highly toxic to river crabs must be strictly controlled when raising crabs in rice fields. If it is necessary to use pesticides, low-toxic pesticides must be selected; the time and pattern of rice pests and diseases must be accurately understood, and the right medicine must be prescribed; the method of application should be spraying to minimize the amount of pesticides scattered on the surface of the water; before applying the pesticide, the water level should be lowered to allow the crabs to enter the crab ditch and crab sluice, and the water should be changed after applying the pesticide to reduce the concentration of pesticides in the field water; spraying should be done in batches every other day to reduce the harm of pesticides to river crabs.

We'd better apply enough basal fertilizer to the rice field before transplanting the seedlings. For the choice of basal fertilizer, we can use organic fertilizer, preferably cake fertilizer, which has very good timeliness and effect. In terms of rice construction, we need to raise and reinforce the ridges around the rice field. The ridge height should be about 66cm, and the soil should be very solid to avoid leakage and crab escape. Clean the field and disinfect the seedlings. About a month before stocking, drain the water in the Fudui River and the crab ditch. After exposure, add 5~10cm of water. For rice fields used to cultivate young crabs, the water should be fertilized before the crab seedlings are released. After the release, feed soy milk or egg yolk once or twice a day, and sprinkle evenly. After seven days, you can start to slowly feed paste feed, such as sweet potato paste, wheat bran paste, pumpkin paste, bean cake paste, vegetable cake paste, wheat bran paste and some paste made from animal offal, and feed sufficient aquatic plants. It is best to add some molting hormones to the feed when the crabs molt.

It is important to ensure the fertility of the soil, and also pay attention to choosing high-quality water sources. The density of crabs must be controlled, and crabs must never be allowed to damage the rice fields.

To raise it, you need to find a pond of suitable size, make good inlet and outlet, then clean and disinfect the pond, build a mound inside, and plant aquatic plants. Generally, it is fed with animal concentrate and aquatic plants. It is necessary to do it at a fixed time, place, quality and quantity. At the same time, the water should be changed frequently to keep the water clean and hygienic.

How to use rice fields to cultivate high-quality crab species?

Using rice fields to cultivate crab seeds can achieve the goal of rice and crab symbiosis and mutual promotion, and is an optimal model for the combination of ecologically efficient planting and breeding.

(1) Rice field preparation

① Rice field selection: The crab seed breeding rice field must have a quiet environment, convenient transportation, irrigation and drainage, strong water and fertilizer retention capacity, and clay or loam soil is preferred. In particular, it is required that the water source is sufficient, the water quality is good, and it is not polluted. The rice field should be rectangular and east-west, which is conducive to increasing the light time and convenient for management. The crab seed breeding rice field is best concentrated and contiguous, with a certain scale, and the field area is not limited, 2 to 10 mu.

② Excavation of ring ditches: For crab breeding fields, ring ditches should be excavated around the inner side 2 to 3 meters away from the ridges. The ditch width is 1.5 to 2 meters and the depth is 0.5 to 0.8 meters. For larger fields, inter-field ditches should be dug, which should be appropriately widened and deepened based on the high-yield ditches in rice fields, in the shape of a "cross" or "well". The excavated area accounts for 5% to 10% of the total area of ​​the rice fields. The excavated soil is used to raise and reinforce the ridges. The ridges are required to be 0.8 to 1 meter high and more than 1 meter wide at the top. They must be compacted and rammed firmly during construction.

③ Water system support: The water used in crab breeding paddies should be separated from other farmlands, and a separate water inlet channel should be built. It can be built with cement culverts with a diameter of about 40 cm, or bricks, stones and other materials. The drainage can be used in the original paddy field drainage channel. The inlet and outlet should be sealed with dense wire mesh or plastic mesh to prevent crabs from escaping and enemies from entering with water.

④ Anti-escape facilities: Anti-escape is the key to the success of crab breeding in rice fields. It is best to use double-layer anti-escape. The outer anti-escape wall is buried around the middle of the rice field ridge. It is required to be 50-60 cm high and buried 10-20 cm in the soil. It is made of cement boards, asbestos tiles and other materials, supported and fixed by wood and bamboo piles, and tied with thin iron wire. The joints of the two boards should be tight without gaps, and the four corners should be built in an arc shape. The inner anti-escape wall is built on the inner side of the ridge, surrounded by mesh and inverted eaves or calcium plastic boards, and is about 40 cm high.

(2) Crab seedlings stocking

①Preparation before stocking: The stocking time is generally in mid-May. 20 days before stocking, remove the silt in the ring ditch and field ditch, then add 10 cm of water to the rice field, use 150 kg of quicklime per mu, dissolve it in water and sprinkle it while it is hot to kill harmful organisms. After the medicinal properties disappear, prepare some water peanuts as attachments.

② Selection of crab seedlings: Choose crab seedlings bred in earthen ponds with parent crabs from the Yangtze River system. The number of crab seedlings should be around 160,000 per kilogram. After more than 5 days of dilution treatment, the salinity should be below 3 when out of the pond. The crab seedlings should be strong, of uniform size, pure color, and active in swimming and crawling.

③Transportation of crab seedlings: Use crab seedling boxes to transport the seedlings in air-conditioned vehicles. Each box contains 0.5-1 kg of seedlings. Five crab seedling boxes form a group, with a wooden cover on the top. When loading the seedlings, the layers of each group of crab boxes should be tightly and firmly connected, without leaving gaps or unevenness to prevent the crab seedlings from crawling out of the gaps and escaping. During transportation, the crab seedlings should be protected from wind, sun, rain and bumps.

④ Stocking crab seedlings: The crab seedlings are first cultivated in the ring ditch for about one month. The stocking amount is generally 1.5 to 2 kilograms per mu of rice field. After the crab seedlings are transported to the edge of the field, the crab seedling box is first placed in the ring ditch water for 1 to 2 minutes, and then lifted up. This process is repeated 2 to 3 times to allow the crab seedlings to adapt to the water temperature and quality of the ring ditch.

(3) Feeding and management

① Crab fry cultivation: After the crab seedlings are put in, water peanut attachments can be evenly spread and feed can be started at the same time. Egg yolks can be fed to the megalopause stage, and the feeding should be done once every 2 to 3 hours. After entering the first stage of juvenile crabs, fish paste with bean cakes and bran can be fed instead. Special starter bait for river crabs can also be fed. The feeding rate can be reduced from 100% to 5% to 7%, and the crabs can be fed 4 to 6 times a day.

② Release into the field: This is usually done after the rice seedlings are planted. At this time, the size and quantity of the crab fry in the ditch can be measured. If the number is just suitable for field breeding, the fence of the breeding pond can be removed to let the crab fry crawl into the field on their own. If the number is insufficient or excessive, adjustments must be made.

③ Feeding: After the crablets enter the field, in addition to using natural bait in the rice fields, they can be fed with aquatic plants, wheat, corn, bean cakes, snails, clams, mussel meat and other baits. A combination of fixed-point feeding and appropriate scattering is adopted to ensure that all crabs can eat feed. During the breeding period, promotion and control measures are taken according to the growth of the crablets to prevent the crablets from being too large or too small, and the weight is controlled to be between 160 and 240 per kilogram at the time of harvest.

④ Water quality control: Since the water level in crab breeding rice fields is relatively shallow, especially in the hot summer, the water quality of the rice fields must be kept fresh and the dissolved oxygen is sufficient. When the water level is too shallow, water should be added in time; when the water quality is too concentrated, new water should be replaced in time. When changing water, the water intake speed should not be too fast or too fast. The method of drainage and irrigation can be adopted to keep the water level relatively stable.

⑤ Daily management: Patrol the fields once in the morning and evening to check the water quality, crab feeding, the amount of aquatic plants and natural bait, and the integrity of escape prevention facilities. Check at any time during windy and rainy weather to prevent crabs from escaping. In particular, beware of attacks by rats, frogs, birds and other predators. Sprinkle quicklime water once every 15 to 20 days during the growth period, using 5 kg of quicklime per mu.

(4) Rice cultivation management

Select rice varieties with strong fertilizer tolerance, hard stems, low lodging resistance, few diseases and insect pests, and high yield. The seedlings are first grown into large seedlings in the seedling bed and then transplanted into the field. 2 to 3 days before transplanting, apply high-efficiency pesticides to the seedlings. Apply 5 kg of superphosphate or compound fertilizer per mu before planting in crab rice fields, and apply urea twice during the rice growth period, 1 kg per mu each time. Except for manually pulling out barnyard grass, crab rice fields generally do not use pesticides and herbicides, and the fields are not left idle.

(5) Crab harvesting

After rice harvest, water is released to introduce crab seeds into the ring ditch and let them overwinter naturally. Generally, crab seeds are collected in February or March of the following year. The method is: take out the water peanuts in the ring ditch and pile them evenly on the open space beside the ditch. The ring ditch is filled with water at night, and the crab seeds are caught under the water peanuts the next morning. More than 90% can be caught after two consecutive times, and the rest can be caught by hand by digging holes.