Three misunderstandings and Solutions of Fertilizer and Water in the process of raising Shrimp in Aquaculture

Fertilizer and water is very important in the culture of Penaeus vannamei, but there are some misunderstandings at present, resulting in unnecessary loss and waste.

1. Excessive fertilization before seedling release

Fertilization before seedling release, do not know the specific conditions of the water quality and sediment of the pond, blindly use inorganic fertilizer, organic fertilizer or some microecological agents to fertilize aquatic products, happen to get water and fertilizer up, if the fertilizer does not rise, it is considered that the amount of fertilizer is not enough, continue to increase the amount. In this way, the water not only does not get fat, but also causes unnecessary waste and leads to the deterioration of sediment and water quality.

1.1 the harm of excessive fertilization

Excessive inorganic fertilizer will speed up the alkalization of the pond bottom and is easy to harden.

Excessive organic fertilizer, such as the complex composition of chicken manure, the insoluble nutrients in chicken manure take a long time to decompose and use, the chicken manure particles sunk into the bottom of the pond are easy to form mud, float to the surface at high temperature to worsen the water quality, and the ammonia nitrogen and nitrite in the water exceed the standard, laying hidden dangers for breeding. In addition, the nutrients of large particles in chicken manure can only be used by zooplankton, but not algae, thus shortening the duration of algae peak. Among them, the fermentation is not good, mixed with a large number of ciliates, Escherichia coli, spirochetes and so on can easily cause Gill, intestinal infection and the outbreak of various diseases.

If the amount of biological fertilizer (fertilizer containing microecological agents) is appropriate, living bacteria can fully decompose the organic matter in water and sediment, turning it into algae-available nutrients to achieve the purpose of fertilizing water; excessive use, live bacteria will over-degrade organic matter, so that the nutrients in the water are reduced, but the water can not be fertilized.

1.2 solution

According to the above situation to find out the indicators of water quality and bottom quality, and deal with the specific situation. Generally speaking, muddy and sandy ponds, and for old ponds, inorganic fertilizers can be used directly with microecological agents or microecological agents alone; sandy ponds, high ponds and new ponds can be used with organic fertilizers with microecological agents. Organic fertilizer must be fully fermented, or it can be fermented together with microecological agents. According to the body method: per cubic meter of chicken manure with microecological preparation 10kg, compound fertilizer 2kg, mix evenly, choose a sunny place to accumulate, seal with Shuo cloth for 5 days for 10 days. Different water sources have different methods: if the composition of groundwater is complex, such as acid or alkali, nitrite is high, it should be tested and adjusted to fertilize the water, and if necessary, it can be connected with algae species; the aboveground water can be directly fertilized after filtration with 80 mesh; the old ponds with thick mud can also use fertilizer and water bacteria only.

two。 Fertilizer and water about 10 days before seedling release

2.1 the harm of fertilizing and watering late

Some shrimp farmers begin to fertilize and water about 10 days before releasing their seedlings, and after 7 days of fertilizing and watering, they can see that there are zooplankton in the water about 7 days later, and then test the seedlings. After the trial is successful, the seedlings are released. As a result, the shrimp seedlings often grow slowly, have poor disease resistance, and even get sick.

2.2 solution

The seedlings were released after about 20 days of fertilizer and water, because many physical and chemical factors in the pond in the process of fertilizer and water were changing violently, the most obvious of which was the change of pH value, which showed the law of "∧". In the early stage, the pH value increased all the time, sometimes reaching about 10; after 15 days, it decreased gradually, and the pH value could be stabilized at about 8.5 after 20 days, which was suitable for shrimp growth. At this time, the water color, transparency and zooplankton are in the best condition, the most suitable for seedling release. Therefore, the best fertilization time should be about 20 days before seedling release.

3. There is no need for fertilizer and water in the middle and later stages of culture.

3.1 the harm of not being fat and water in the middle and later period

In the middle and later period, the transparency of the pond water is low, and some shrimp farmers think that the water is already very fat, and it is not necessary to fertilize the water, or even counterproductive.

In fact, in the middle and later stages of culture, the transparency of the pond water is low, the water color surface looks thick, and the possibility of water and fertilizer cannot be ruled out. at the same time, there is another situation, at this time, the water contains plankton, various substances dissolved or suspended in the water, such as residual bait, feces, organic debris, dead algae, etc., after refraction of light, it is not the true color of beneficial algae, but there are very few algae in the exponential growth period. The transparency of water color is also very low, creating a false impression of water and fertilizer. When the algae phase is destroyed, the balance of the water environment is destroyed, the water quality gradually deteriorates, the harmful substances exceed the standard, and the water quality is unstable, which naturally affects the health of shrimp.

3.2 solution

If so, according to the characteristics of the water quality in the middle and later stages, some microecological agents containing nitrifying bacteria, phosphorus-solubilizing bacteria, potassium bacteria and nitrogen-fixing bacteria should be put in at this time, and the nitrogen elements should be nitrified by nitrifying bacteria to transform nitrogen into algae-fed nutrients; phosphorus-solubilizing bacteria decompose a large number of long-chain phosphorus in water that can not be directly used by algae into short-chain phosphorus, which is convenient for algae absorption and utilization. Potassium bacteria can decompose potassium from silicic acid minerals and release phosphorus from apatite; nitrogen-fixing bacteria convert molecular nitrogen that can not be used by plants into ammonia nitrogen that can be used by plants through the activity of a special catalytic nitrogenase in their bodies. In this way, it not only plays the role of inorganic fertilizer and organic fertilizer, but also avoids their shortcomings, saves energy and adjusts the micro-ecological balance. Beneficial algae propagated, the algae phase balanced, and at the same time inhibited the excessive reproduction of harmful algae. When algae grew and propagated, they absorbed nitrogen, sulfur, phosphorus and other elements in the water, adjusted the balance of substances in the water, avoided the increase of harmful substances such as ammonia nitrogen, hydrogen sulfide and nitrite, and made the culture water "fertile, lively, tender, cool and stable". The environment is good, and the shrimp seedlings are naturally healthy, thus it can be seen that fertilizer and water are equally important in the middle and later stages.