What should we pay attention to when adding fertilizer in aquaculture pond? Why fertilize the fish pond?

Generally, the purpose of applying fertilizer to aquatic ponds is to increase the quantity and quality of fish bait, at the same time, it can also provide nutrition to algae in fish ponds and maintain water quality and water quality. Because the fertilizer itself will affect the environment of fish ponds, there are many precautions and taboos in applying fertilizer to fish ponds. Only by selecting the appropriate types and methods of fertilizer can we ensure the effect of fertilizer and improve the quality of fish in the pond.

First, why should fertilization be carried out in pond culture

1. Plankton propagated through fertilization can be filtered by fish, increasing the yield of filter-fed fish such as silver carp, and suitable opening bait for propagated plankton such as rotifers and other fish fry.

2. Through fertilization, we can provide sufficient nutrient elements for algae growth, maintain appropriate algae abundance, and provide sufficient dissolved oxygen for the pond by photosynthesis.

3. To maintain the stability of pond water quality through fertilization, organic fertilizer has a certain chelating effect, which can reduce the harm of heavy metal ions to fish, such as amino acid fertilizer and water series.

4. Maintaining a certain degree of fertility of the water body through fertilizer and water can prevent the spread of aquatic plants and benthic filamentous algae, and reduce the sediment content in the water body, which is beneficial to the healthy growth of fish.

5. Through fertilization, the water body can keep a good water color, and the fish have strong anti-stress ability in the suitable water color water body, such as sense of security.

2. Types of fertilizers

1. Organic fertilizer: organic fertilizer mainly includes manure, green manure, barnyard manure, compost and so on. These fertilizers contain a variety of inorganic salts such as nitrogen, phosphorus and potassium, and organic substances such as proteins, fats and sugars. The fertilizer effect is good and long-lasting, but the effect is slow after application, so it is also called "late-acting fertilizer". However, organic fertilizer will decay and decompose in water, consume oxygen in water, and release toxic gases (dihydrogen sulfide, ammonia, carbon dioxide, etc.), which will have a certain impact on the growth of fish. when applied, it is not suitable to apply a large amount of fresh organic fertilizer directly into the fish pond. instead, it should be closed and fermented in advance and then applied.

2. Inorganic fertilizer is also called chemical fertilizer. The characteristic of this kind of fertilizer is that it contains relatively single nutrients, and most of them are chemical fertilizers that contain only one or two kinds of fertilizer. When applied in water, it is easy to decompose and take effect quickly, so it is also called "quick-acting fertilizer". Including nitrogen fertilizer, phosphate fertilizer, potash fertilizer and calcium fertilizer and so on.

3. At present, most of the fertilizers on sale on the market are amino acid fertilizer or water paste, or biological fertilizer composed of inorganic fertilizer, organic fertilizer and probiotics.

Matters needing attention in fertilization

The main results are as follows: 1. In the early stage of culture, organic fertilizer is mainly used as base fertilizer, and the fertilizer effect is long-lasting. In the later stage, it is mainly inorganic fertilizer, because of a large amount of bait in the later stage, the feces of fish is a good organic fertilizer. The application of inorganic fertilizer has the advantages of light water pollution and fast fertilizer effect.

The use of fertilizer should be dissolved in the water and sprinkled in the whole pool, based on the principle of a small number of times, according to the suitable control of fat and thin ponds, it should be carried out on a sunny morning. Fertilization is not suitable when the water temperature is too high. The ratio of nitrogen to phosphorus is controlled at about 3:1. Organic fertilizer is prohibited in high temperature period to reduce oxygen consumption factor.

2. The main factors affecting fertilizer efficiency are water temperature, PH value, dissolved oxygen, sediment, weather and other factors, which should be adjusted according to the specific conditions. For example, fertilizer and water below 20 ℃ is slower, fertilizer efficiency is the best at PH7-8.5, fertilizer efficiency is good when dissolved oxygen is sufficient, loam soil is easier to fertilizer and water than sandy soil, it is easier to fertilizer and water in sunny days, and no fertilizer is applied in muggy and rainy days. No fertilization is applied when fish disease occurs; no additional fertilization can be applied in intensive culture ponds.

From July to August, when the water color becomes thicker, stop using nitrogen fertilizer and use phosphate fertilizer alone. In ponds with thinner water quality and higher ammonia nitrogen content, phosphate fertilizer should be applied to promote the growth of phytoplankton and absorb ammonia nitrogen in ponds.

4. The outbreak of nitrogen-fixing cyanobacteria can be effectively controlled when the ratio of nitrogen to phosphorus is close to or equal to 16: 1 by changing the ratio of nitrogen to phosphorus. After killing cyanobacteria, a small amount of phosphate fertilizer can also reduce the outbreak of cyanobacteria), the application of silicate fertilizer can promote the reproduction of beneficial algae such as diatoms and inhibit the outbreak of harmful algae such as blue-green algae.

5. the aging of the water body should be fertilized in time, restore the vitality of algae, and properly supplement the insufficient carbon source of the water body to promote the reproduction of beneficial fungi, so as to promote the fertilizer efficiency of the water body. The transparency of the water body is maintained at 20-40cm.

6. Calcium fertilizer was applied to shrimp and crab ponds to promote shelling growth.

7. Mastering the time and sequence of plankton reproduction peak after fertilization has important guiding significance for aquaculture production. The general order is as follows: phytoplankton (4-5 days)-protozoa-rotifers (4-7 days), nauplius-Cladocera (6-24 days)-copepods (7-32 days). According to the peak of plankton, the fish fry can go into the pond at the right time and have sufficient opening bait to increase the survival rate and save feed.

Four, Ten taboos of fertilization

1. Fertilize in rainy days. In rainy days, the photosynthesis of phytoplankton is not strong, the absorption capacity of nitrogen, phosphorus and other elements is poor; in rainy days, the amount of water is large, the effective concentration of fertilization will be reduced; in flood, fertilizer loss is large.

2. Fertilizing in muggy days. When the weather is muggy, the dissolved oxygen in the water is low, and the oxygen consumption of organic matter in the water increases after fertilization, which is very easy to cause fish floating head and flooding pond due to hypoxia.

3. Fertilization in high temperature season. Fertilization in fish ponds should be carried out at noon on a sunny day with a water temperature of 25 ℃ ~ 30 ℃ every year from April to October. If the water temperature exceeds 30 ℃, fertilizer should be stopped and less fertilizer should be applied.

4. Fertilizing with muddy water. The excessive turbidity of the water body indicates that there are too many clay mineral particles in the water body, and some ions of fertilizer are easily absorbed and fixed and precipitated by clay particles, so that the fertilizer effect can not be released for a long time.

5. Fertilize when the food intake of fish is not prosperous or when there is an outbreak of epidemic disease. When the fish food intake is not prosperous, a large number of plankton cultivated by fertilizer can not be used by the fish in time, which is easy to destroy the water quality; when the epidemic disease breaks out, the fish body resistance is weakened, if more ammonium nitrogen fertilizer is applied, the fish is easy to be poisoned.

6. Dry application of solid fertilizer. Dry application of nitrogen and phosphate fertilizer is granular, stay on the water surface for a short time, easy to sink to the bottom of the water, affecting the fertilizer efficiency. Generally speaking, when applying solid nitrogen and phosphate fertilizer, it should be dissolved and sprinkled with water all over the pool.

7. Single application of chemical fertilizer. The main purpose of fertilization is to cultivate digestible plankton in fish, and plankton generally requires the ratio of nitrogen, phosphorus and potassium to 4 ∶ 4 ∶ 2. If a certain chemical fertilizer is applied alone, it will restrict the full play of fertilizer efficiency.

8. Mix blindly. Not any two or more fertilizers can be mixed, such as the application of quicklime, it is best to wait 10-15 days before applying superphosphate, so as to avoid chemical reactions between the two, resulting in the loss of fertilizer effect.

9. Apply too much fertilizer at one time. Excessive application of ammonium nitrogen fertilizer at one time will lead to excessive accumulation of ammonia in the water body, resulting in fish poisoning; excessive application of organic fertilizer at one time will increase the oxygen consumption of organic matter in the water body, resulting in anoxic flooding of fish, so do not apply too much fertilizer at one time. Fertilization is generally required to be applied every 3 to 5 days.

10. Release the surface water after fertilization. After fertilizer is applied into the water body, it usually takes a series of physical and chemical reactions for 3 days before it can be fully utilized by plankton. The population of plankton is generally evenly distributed in the depth of 1-2cm on the surface of the water body. If the fertilizer is released from the surface water after fertilization, the fertilizer efficiency will be reduced.

5. Three methods of fertilization in fish ponds

1. The method of applying organic fertilizer. Organic fertilizer includes all kinds of human and animal manure, 100 kg per mu each time, once every 7-10 days, and can be stacked in small piles and spread throughout the pond. The method of building frame fertilizer can also be adopted. That is, a wooden pole is used as a support. Use wicker foil as the chassis, build several shelves in the deep water area of the pool, put the manure on the shelf, let it close to the water surface, and make the fertilizer decompose and spread in the middle and upper layer of the water. You can also hang the bag, that is, put the fertilizer in a rot-resistant bag and hang it on a wooden post in the deep water area of the pond close to the water surface to allow it to decompose and spread by itself. The method of shelf and bag fertilizer application can speed up the decomposition rate of fertilizer and make it spread evenly to the whole fishing pond, especially the rotten decomposition of special fertilizer in the water layer of the pond, so that although the fertilizer decomposes quickly, it will not cause hypoxia and make the fish float.

two。 The method of chemical fertilizer application. The chemical fertilizer used in fish ponds was mainly nitrogen and phosphorus, and the application ratio was 1:2. Under normal circumstances, 2.5 kg per mu of vegetarian urine and 5 kg of phosphate fertilizer should be dissolved in water first, and then sprinkled evenly over the whole pool, once every 5-7 days.

3. Green manure topdressing method. Green manure includes all kinds of dry land grass, sunburned to semi-dry, then mixed with a certain amount of manure, piled in the corner of the pool, pressed with stones or soil, and then turned every 3-5 days to rot and decompose. In the liquid diffusion pool, it can be decomposed in 7-9 days in autumn, and then the coarse and hard-to-rot rhizomes will be fished out and new materials will be added, applying 100 kg of green manure per mu.