How to raise fish in winter fallow rice paddies? Key technical points explained

Using winter fallow rice paddies to raise fish can both improve the utilization rate of the paddy fields and increase farmers' economic income, reduce pests and diseases of rice seedlings, and reduce pesticide and fertilizer expenses for the coming year. In addition, when planting rice seedlings in spring, no-tillage can be used, saving labor, and a double harvest of rice and fish can be obtained. Through paddy field engineering renovation, scientific stocking and management, the yield of marketable fish can reach 150-200 kg per mu, and the net profit per mu can reach about 800 yuan. The input-output ratio is 1:2, which can achieve good economic and ecological benefits. The techniques for raising fish in winter fallow rice paddies are introduced below.
(1) Selection of paddy field. Choose paddy fields with sufficient water sources, fresh and pollution-free water quality, and convenient irrigation and drainage.
(2) Paddy field engineering construction. After the rice harvest, return the rice straw to the field for use as fish feed and fertilizer. Use the soil around the original field to raise the field ridges by 1 m, making the ridge base 50 cm wide and the top 30 cm wide, with a 15 cm diameter PVC pipe at the water inlet, and set up a flood discharge outlet at the water outlet with a steel mesh smaller than the fish fingerlings as a fish-blocking screen. Disinfect by splashing with 75 kg of quicklime water per mu of field. Apply 150-250 kg of decomposed manure per mu of paddy field as base fertilizer.
(3) Fish fingerling stocking.
① Before stocking fish fingerlings, use a small amount of quicklime or bleaching powder to clear wild and miscellaneous fish from the field, then fill with water to 50 cm. When filling with water, tie a 40-mesh mesh bag onto the plastic pipe at the water inlet to filter the water, so as to prevent wild fish from entering the field.
② Before releasing fish fingerlings, soak them in 2-3% salt water for 10 minutes. The stocking rate is 300 fish per mu, including 90 grass carp weighing 100 g each, 10 silver carp weighing SD g each, and 180 common carp 10 cm in body length. The fingerlings should be strong in physique, with complete scales, and free of disease and injury.
③ Stocking time: The stocking time for fish fingerlings is from early October to mid-October, about 5 days after the paddy field is filled with water (after the disinfectant effect has dissipated, it can be carried out).
(4) Planting of ryegrass. Plant ryegrass on the field ridges and vacant land beside the field. The grass planting area is 10-15% of the paddy field area, and the grass yield is 5 tons, for feeding the stocked grass carp. For each mu of fish-raising paddy field, prepare enough land of 0.6 mu for planting grass. At the end of September or the beginning of October, choose suitable weather to sow annual ryegrass, using 2-3 kg of seed per mu. Fertilize the ryegrass 3 days before harvesting it, which can shorten the interval between two harvests and increase grass yield.
(5) Feeding management. In the first week after stocking fish fingerlings, feed is generally not given. Common carp can eat plankton, organic debris, and fallen rice grains in the field, and grass carp can eat rice leaves. After one week, feed cornmeal and formula feed daily at 5% of the grass carp's body weight, and feed green vegetable leaves at 40% of the grass carp's body weight. After ryegrass can be harvested in November, grass carp are mainly fed ryegrass. From November to December, feed 2% pellet feed daily. From January to February, as water temperature gradually rises, fish food intake gradually increases. Feed 5% pellet feed daily, with the principle that no feed remains by the next morning.
(6) Daily management. When fish fingerlings are first stocked, fill with water to 30 cm so that rice stubble can sprout and grow for grass carp to eat. According to the growth of ratoon rice and the feeding situation of the fish, gradually deepen the water level. In November, deepen the water level to more than 60 cm. The daily feeding amount is 3-4% of fish body weight, divided into one feeding in the morning and one in the afternoon. After entering December, as the weather gradually turns colder, feeding is changed to once every 8 days, carried out at noon each day, and the principle remains that the feed should be eaten up with nothing left. The daily feeding amount is 1-2% of fish body weight. After entering winter, feed may not be given. However, green grass still needs to be fed every day to maintain a relatively stable appetite in grass carp. After the Beginning of Spring in February, as the weather gradually warms, the amount of green grass fed gradually increases. After March, compound feed can be appropriately added, with a daily feeding amount of 1-3%. After the end of March, fish enter a period of rapid growth. At this time, the feeding amount for grass carp needs to be appropriately controlled, with the degree being that grass carp can eat until 80% full. Excessive feeding will cause fish diseases such as grass carp enteritis. Every day at morning and evening, check the field edge to observe fish activity, so as to avoid fish dying from floating head due to oxygen deficiency and to promptly discover fish diseases and apply the right medicine.
(7) Fish disease prevention and control. During the culture period of fish raised in winter fallow rice paddies, the low-temperature period is relatively long and there are fewer diseases. In early November, use disinfectants such as bleaching powder and nitrogen dioxide for preventive disinfection, and regularly mix or soak drugs such as garlic, rhubarb, and oxytetracycline into pellet feed and grass to achieve the purpose of comprehensive disease prevention.
(8) Harvest. Before transplanting the first-season late rice, harvest the fish for market. Each mu of paddy field can obtain a net yield of about 200 kg. After harvesting is completed, the paddy field does not need plowing and can be directly planted with first-season late rice.