What are the technical measures for rice-fish rotation?

@#@233@#@Before starting, preparatory work must be done well; first, the field ridges must be heightened and reinforced. In conjunction with planting the early rice seedlings or preparing the field, first heighten and widen the field ridges as a foundation for later heightening and widening; after the early rice is harvested and the late rice is transplanted out, promptly heighten the ridges to more than 1.5 m, with a ridge surface width of about 1.2 m. Second, a holding pond must be prepared well. The holding pond is dug at one corner of the main field, with an area of 15%-20% of the rice field. The holding pond is about 1 m deep. Finally, a drainage ditch should be opened at a convenient end of the field to prevent floodwater from rushing into the pond and causing the fish to escape with the water. A fish-blocking device must be properly built at the pond drainage outlet; the fish-blocking device is generally made by nailing synthetic mesh cloth onto a wooden frame.

If silver carp, bighead carp, and grass carp are stocked, each fish is required to reach 200-300 g, because if the size is too small it will affect their food value. Fish such as silver carp, bighead carp, grass carp, black carp, common carp, and bream can be stocked, either polycultured or monocultured, with a stocking size of 0.8-1 cun. The polyculture density should be determined according to the depth of the pond water, the size at harvest, and the level of management. Generally, fish fingerlings are 8,000-10,000 per mu; for monoculture of Nile tilapia, 3,000-4,000 are suitable; for polyculture of silver carp, common carp, bighead carp, grass carp, black carp, and others, about 300 per mu can be stocked. For the polyculture ratio, silver carp at 50%, bighead carp at 10%, grass carp at 20%, bream at 15%, and common carp at 5% is suitable.

For rotation fish ponds, management must be especially strengthened. The fertilization method is: after the early rice is harvested for grain, leave the rice straw in the field to be submerged and rotted as base fertilizer. During the fish-rearing cycle, apply various green manures and animal manures to fertilize the pond water to a tea-brown or yellow-green color. Apply green manure 2-3 times per month, 250-300 kg per mu each time; the amount of animal manure applied depends on the water color. The feeding method is: grind various leftover grains, wheat bran, and the like into powder and feed 1-2 times daily; for every 10,000 fish, feed 1-2 kg each time in the early stage and about 3 kg each time in the later stage. For monoculture of grass carp, increase the above amount by one times. Where conditions permit, feeding duckweed is the most effective way to increase the yield of grass carp and bream; when feeding duckweed, be careful not to cover the entire pond, otherwise the fish will die from lack of oxygen. In addition, fish ponds should also be cleared of weeds. In rice-field fish culture, the water depth is limited and there is much mud in the field, so various aquatic plants tend to grow; the fish cannot use them all at once, and their presence in the pond affects the clarity of the pond water. Therefore, they must be pulled out completely and piled in one corner to rot and serve as fertilizer; otherwise, it will affect the growth of the fry. Rice-field fish culture should also pay attention to preventing and treating fish diseases; the method is to manage feeding well and enhance the disease resistance of the fish. Quicklime can also be applied 2-3 times per month, 15-20 kg per mu each time. In this way, it can both prevent and treat fish diseases and improve water quality, enhance the reproductive capacity of plankton, promote the healthy growth of fry, and achieve a bumper fish harvest.