Small reservoirs are reservoirs with a total reservoir capacity of between 10 and 10 million cubic meters. Small-scale reservoir fish farming has higher requirements for fertilization techniques, and fertilizing fish is one of the important measures for small reservoirs to increase fish production. First, fertilization time. The use of fertilizers by phytoplankton in the water and the utilization of phytoplankton by fish and zooplankton should be determined. When the transparency of the water body drops below 40 cm, fertilization begins when the water temperature rises above 15°C, and 20-30°C is the key period for fertilization. Fertilization should be suitable when the water is delaminated before noon, so that the time for the fertilizer to stay on the surface can be prolonged. Second, fertilization location. Should be concentrated in the shallow water area (less than 3 meters) and the reservoir bank zone. Shallow water can not be delaminated and can be circulated vertically. Oxygen is sent to the bottom layer to promote organic mineralization and transfer to the surface of the water. If the water exchange volume in the flood season is large, the emphasis should be placed on fertilizing in the water-stagnation area to prevent the loss of fertilizer, and small reservoirs with large water surface can be fertilized in the upper and middle reaches. Third, fertilization types. It is necessary to combine long-acting fertilizer with quick-acting fertilizer, complete nutrient fertilizer and single fertilizer. Due to the large amount of water exchange in small reservoirs, quick-acting fertilizers should be used as the main fertilizer. Organic fertilizers can be added before the early spring flood season, and inorganic fertilizers should be applied during the flood season and the higher water temperatures from June to September. Inorganic fertilizers are mainly ammonium bicarbonate and water-soluble phosphate superphosphate and heavy superphosphate. Manure can be used as organic manure, green manure, manure, compost, etc. It should be based on local fertilizer sources and economic benefits. Fourth, the amount of fertilization. The proportion of available nitrogen and available phosphorus in the water can reach (6-7):1 by fertilizing, and waste is caused by improper proportion. When the effective nitrogen concentration is less than 0.3 mg/l, fertilization should be carried out. Generally, 2.5-3.5 kg of ammonium bicarbonate or 1.3-1.4 kg of urea and 2-2.5 kg of superphosphate are applied per acre, and the amount of phytoplankton reaches a peak 6-8 days after fertilization. Fifth, fertilization methods. The fertilizer is dissolved in water and sprayed with the pump. When nitrogen and phosphorus are applied at the same time, the phosphate fertilizer is dissolved first, then nitrogen fertilizer is added. The fertilizer can be loaded into the release device, the upper layer is loaded with nitrogen fertilizer, the lower layer is loaded with phosphate fertilizer, and the second fertilizer is applied. The interval is 10-15 days. Organic manure can be combined with compost and fertilizer, composted at low temperatures, spilled at the shore of the entire reservoir at temperatures above 20°C, and the amount and interval of the manure depend on the color, transparency and other fertilizers. 6. Other Precautions (1) Fertilizer shall be stopped when flooding in flood season and water quality are turbid. (2) After lime is applied, fertiliser should be applied after 15 days. (3) Fertilizing fish should be dominated by filter-feeding fish carp, carp, and silver carp, and carp and carp should be no less than 2:1.
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