A Complete Analysis of the Key Points of the New Technology for Rice-Fish Engineering Aquaculture

I. Technical Introduction. Rice-field engineering fish culture technology is a new aquaculture technology gradually formed in recent years on the basis of traditional rice-field fish culture, through experimental research, technical development, refinement and improvement. This technology can effectively use the ecological conditions of rice fields to develop the aquaculture industry, and increase aquatic product output without competing with crop cultivation for land. Raising aquatic organisms in rice fields also has multiple functions such as saving land, saving water, saving fertilizer (less chemical fertilizer applied), eliminating insects, eliminating pests, loosening the soil, and improving the water storage, irrigation and drought resistance capacity of rice fields, making it an ecological agricultural production technology. Therefore, rice-fish engineering technology is playing an increasingly important role in adjusting the agricultural industrial structure and increasing farmers' incomes.
II. Key Operating Points
1. Rice-field engineering construction
(1) Construction of the fish pit (fish shelter): the fish pit accounts for about 5-8% of the total area. It can be built in the center of the field, at the field edge or at the field corner, dug into a square or round fish pit. The fish pit is 80 cm deep and connected to the center of the fish ditch. The fish pit can be dug 30-40 days before transplanting rice seedlings. After digging, reshape and repair it once every 10 days, for 3-4 consecutive times, so that the fish pit takes good shape.
(2) Construction of fish ditches: accounting for 3-5% of the total area. According to the size and shape of the field, dig them into a straight line shape, a cross shape, a well shape or a square shape. The ditch width is 40-60 cm and the depth is 30-40 cm, so that the horizontal ditches, vertical ditches and surrounding ditches are connected. For the central fish ditch, open a ditch along the long side of the field in the center of the field; for the surrounding fish ditch, dig it 1.5 m away from the field ridge.
(3) Raise and widen, and reinforce the field ridges. Raise and reinforce the field ridges before transplanting rice seedlings. The reinforced field ridges are generally 80-120 cm high and 60-80 cm wide, and are pounded solid to prevent the ridge from collapsing during heavy rain or water overflowing the ridge and allowing fish to escape.
(4) Open the inlet and outlet well and install fish-blocking screens: the inlet and outlet should be dug on the field ridges at two corresponding corners of the rice field so that water flow is unobstructed. The size of the outlet should be determined according to the size of the field and the amount of inflow during heavy rain, with the criterion being safety and no fish escape. Install fish-blocking screens at the inlet and outlet to prevent fish from escaping and to prevent enemies such as wild miscellaneous fish from entering the fish-culture rice field. The fish-blocking screens can be made of materials such as iron wire and bamboo strips. The length of the fish-blocking screen is 3 times that of the outlet, so that it forms an arc, and its height should exceed the field ridge by 10-20 cm, with the bottom inserted 30 cm into hard soil.
2. Selection of culture species, determination of stocking size, stocking quantity, etc. of fingerlings
(1) Fish culture in rice fields: per mu, 150 common carp fingerlings weighing 50 g each can be stocked, and 70 grass carp weighing 50 g each, or 600-800 one-inch fingerlings can be stocked. Stocking ratio: common carp 60%-80%, grass carp 20%, crucian carp 10%. Generally, after 8 months of culture, about 100 kg of marketable fish or about 80 kg of large-size fingerlings can be harvested.
(2) Crab culture in rice fields: if the planned yield of marketable crabs is more than 20 kg per mu, stock 4-5 kg of crab seed of 80-120 individuals/kg per mu; if the planned yield of marketable crabs is more than 30 kg per mu, stock 6-7 kg of crab seed of the above size. Mixed culture of fish and crabs can also be carried out, stocking 2.5-3 kg of crab seed of 80-120 individuals/kg per mu and 10-15 kg of large-size fingerlings.
(3) Freshwater shrimp culture in rice fields: usually stock 15,000-20,000 shrimp seed larger than 1.5 cm per mu, or 0.3-0.5 kg of egg-bearing parent shrimp, and appropriately stock a small amount of summer fry of silver carp and bighead carp to make full use of the water space of the rice field and regulate water quality.
3. Scientific feeding management. The daily feeding amount should be determined according to water temperature, water quality and season. Generally, the daily feeding amount accounts for 3-5% of the body weight of pond fish or 5-8% of the body weight of pond shrimp and crabs. Feed once each in the morning and afternoon every day. The type of feed fed is determined by the cultured species. River crabs and freshwater shrimp are omnivorous aquatic economic animals. They like both plant-based feed and animal-based feed, especially prefer animal-based feed, and have the habit of overeating. Therefore, in the combination and overall arrangement of feed for river crabs and freshwater shrimp, the principle of "matching meat and vegetables, combining refined and rough" should be adhered to. While making full use of the natural feed in the rice field, more green feed such as water grass, vegetable leaves and pumpkin should also be fed, supplemented by animal-based feed such as small miscellaneous fish and snails, implementing scientific feeding so that they eat enough and eat well and promoting growth.
4. Water quality regulation and management. The management of water level and water quality in fish-culture rice fields must not only serve the growth needs of fish but also conform to the dry-wet alternating environment required for rice growth. Therefore, the following points should be done well in water quality management: First, adjust the water level according to seasonal changes. At the beginning of stocking in April and May, in order to raise the water temperature, keeping the water depth in the ditch at 0.6-0.8 m is sufficient. As the temperature rises and the fish grow, the water depth can reach 1 m in July, and in August and September the water level can be raised to the maximum. Second, adjust the water level according to changes in weather and water quality. Usually from April to June, change the water once every 15-20 days, each time replacing 1/5-1/4 of the water. In the high-temperature season from July to September, change the water 1-2 times per week, each time replacing 1/3 of the water, and later as the temperature drops, gradually reduce the frequency and amount of water changes. Third, regulate the water level according to the requirements of rice field drying for pest control. When the rice field needs to be sun-dried, lower the water level until the field surface is just exposed. The sun-drying time should be short, and immediately after sun-drying ends, raise the water level back to the original level. If the rice needs to be sprayed with chemicals for pest control, spray on the leaf surface as much as possible, and replace with fresh water according to the situation to maintain a good ecological environment.
5. Daily management. The daily management of rice-field culture requires strictness, conscientiousness and perseverance. Patrol the field once in the morning and once in the evening every day, paying attention to checking changes in water level, fish feeding activity and the integrity of escape-prevention facilities, etc. When problems are found, promptly take corresponding technical measures, and do a good job in disease prevention and control.
III. Precautions
1. When constructing rice-field engineering and digging trenches by compartments, fish ditches should be dug according to water flow or in an east-west direction, so as to facilitate flood discharge, help ventilation and light transmission in the rice field, and increase rice yield.
2. The chemicals used for rice pest control must be appropriate. Pesticides such as trichlorfon and dichlorvos cannot be used. The use of other low-toxicity and high-efficiency pesticides must not harm fish, and the spray method should be adopted. After application, change the water in a timely manner.
New Model of Planting and Breeding in Low-lying Dual-purpose Fields
In recent years, the scale of aquaculture in low-lying dual-purpose fields in our province has become larger and larger, with a good development momentum. The broad masses have successively created many planting and breeding models according to their own conditions. Some are mainly based on planting, some mainly on breeding, and some combine planting and breeding. The benefits of various models vary. Two high-efficiency planting and breeding models are briefly introduced below.
(1) Key technical points of the lotus root-rice two-crop planting model
This model involves cultivating early-maturing lotus root in the first half of the year and planting late rice in the second half. Its advantage lies in two harvests a year, improving land utilization, giving consideration to both cash crops and grain, requiring relatively little input, and having relatively high economic benefits. This model is suitable for dual-purpose farmland with relatively high terrain, a plough layer of about 30 cm, and relatively small fields.
① Key points of lotus root cultivation. In this model, the key to lotus root cultivation lies in selecting good varieties, with the focus on early management to promote early development. For lotus root varieties, early-maturing varieties among shallow-water lotus roots, such as Elian No. 1, should be selected, and medium- and late-maturing varieties must be avoided. Plant in late March, with appropriate close planting, using 200 kg of seed per mu. The amount of base fertilizer applied is twice that for early rice. Management of the lotus root field should focus early on promoting early development. The amount of topdressing is basically the same as that for early rice. Scientifically control the water level, and strengthen pest and disease control. Tender lotus root can be harvested around Minor Heat, and harvesting is completed around Major Heat, with a yield of 1000 kg of fresh lotus root per mu.
② Key points of late rice planting. For late rice, high-quality late hybrid rice varieties that are medium-maturing or early-maturing should be selected. According to the requirements of transplanting around Major Heat and the characteristics of the varieties, transplant sparsely at the right time with strong seedlings, and appropriately increase the amount of seed used. The previous lotus root field has more fertilizer applied, so in this crop, topdressing must be avoided in excess to prevent pests, diseases and lodging, and potassium fertilizer should be applied appropriately. The yield of late rice can generally reach about 500 kg.
③ Economic benefits. In this model, the yield of fresh lotus root in the first half of the year is 1000 kg per mu. Because it is marketed early and the price is high, the output value per mu is about 2000 yuan. In the second half of the year, the yield of rice is 500 kg per mu, creating an output value of 620 yuan. The annual output value per mu can reach 2620 yuan. Generally, lotus root farmers keep their own lotus root seed, and the net income per mu is around 2000 yuan. The lotus root field uses a relatively large amount of fertilizer. If the soil is not fertile enough, sufficient fertilizer sources must be available. At the same time, digging lotus root coincides with the harvest of early rice, labor is relatively concentrated, and attention must also be paid to the sales market.
(2) Integrated culture of freshwater pearl mussels and ducks
This model involves raising meat ducks in pens beside dual-purpose fields and cultivating pearls and fish in the water; duck manure and residual feed fertilize the water to cultivate plankton for pearl mussels and filter-feeding fish to consume; the final products are pearls, meat ducks and by-product fish. Its advantage lies in integrated aquaculture on land and water, with its own stable fertilizer source, and feed is fully utilized at two levels, resulting in large output and significant economic benefits; however, input is relatively large and risk is also relatively high. This model is suitable for dual-purpose farmland with relatively low terrain and relatively deep water level, and is suitable for relatively long-term operation.
① Key points of meat duck raising. Ducklings (within 4 weeks of age) have relatively high requirements for raising conditions and should be raised in a separate centralized house; only young ducks are penned at the side. For duck breeds, lean-meat type French Muscovy ducks or Beijing ducks can be selected, but Beijing ducks are somewhat fatty. About 100 young ducks are raised per mu of water field. Duck houses, duck beaches and water enclosures are built at 8 ducks/sq m, 6 ducks/sq m and 1 duck/sq m respectively. The duck house is best facing south with its back to the north; if the water surface is relatively large, the house site can be selected separately. For duck feed, commercially available compound feed can be used, or mixed feed can be made according to meat duck feeding standards. Attention should be paid to prevention and control of duck diseases. Generally, one batch of marketable meat ducks can be produced every 2-3 months.
② Key points of pearl culture. For pearl mussels, the triangle sail mussel is selected, and the production type is sheet-like nucleated pearls. Earnestly ensure the quality of pearl implantation, and calculate the total hanging culture amount at 800 pearl-culturing mussels hung per mu of water surface. Duck manure should be strongly composted and fermented and must not be applied directly as fresh manure. The pond water transparency should be kept at 20-25 cm, and the water is required to be lively and refreshing. Earnestly do a good job in preventing mussel diseases. The cultivation of nucleated pearls generally has a production cycle of 1.5 years, with an average annual output of 2.6 kg of nucleated pearls per mu of water surface.
③ Key points of by-product fish culture. In order to make full use of the water body, this model can raise a small number of fish as an additional crop. Fish output is controlled at 100-150 kg according to water depth. The species should mainly be medium- and lower-layer feeding fish. In principle, no feed is put in; artificial feed is added depending on the situation. In dual-purpose field ponds, medication should take into account both river mussels and fish, and any drugs sensitive to mussels should be used with caution.
④ Economic benefits. Calculating on the basis of 3 batches of meat ducks produced each year in dual-purpose field ponds, 300 meat ducks are produced per mu of water surface per year, with an output value of about 8100 yuan. The average annual output of nucleated pearls per mu of water surface is 2.6 kg, with an output value of about 3300 yuan. The by-product fresh fish output is 125 kg per mu, with an output value of about 800 yuan. The two aquaculture projects together bring the annual output value per mu of water surface to 12200 yuan. Net income is around 2900 yuan.
(3) Feeding management and disease prevention and control. The feeding management and disease prevention and control methods of the aquaculture technology model for low-lying dual-purpose fields are the same as those for pond aquaculture technology, and are not described here.