After entering the winter, experts often recommend applying “gas and fertilizer” to greenhouses and greenhouse vegetables. Therefore, many farmers have asked questions recently: What is “gas and fertilizer”? How to properly apply "gas fertilizer"? In this issue, experts are invited to answer some of these questions for reference by farmers. --editor
Q: What is "gas fertilizer"? Where is the main use?

A: "Gas and fat" is carbon dioxide gas (CO2), because carbon dioxide exists in the form of gas under normal temperature conditions and as an integral part of the air. “Gas and fertilizers” are mainly used in greenhouses or greenhouse crops that are closed and managed in cold winters, especially those with sufficient light but prolonged nitrogen application.

Q: Is there carbon dioxide in the air, is it still to be applied? What does it do for crop growth?

A: You must have heard of photosynthesis. Photosynthesis is the chlorophyll of plants. With light as energy, carbon dioxide and water are converted into organic matter and oxygen such as sugar, which forms the biochemical process of crop products. It can be seen that “gas fertilizer” is also an important raw material for production, just like mineral fertilizer. It has been determined that for every 1 gram of organic matter synthesized by green plants, 1.6 grams of carbon dioxide is required to be absorbed, and 90% of the dry matter accumulated in plants is derived from photosynthesis. Under normal circumstances, carbon dioxide in the air can meet crop needs and does not need to be applied as a fertilizer. However, in greenhouses and greenhouses that are closedly managed in winter, the air is not circulated, and the carbon dioxide consumed by photosynthesis is not replenished. The lack of carbon dioxide becomes a limiting factor for crop growth, so it is necessary to apply “gas fertilizer”.

Special emphasis is placed on the fact that both carbon and nitrogen are essential nutrients for crops, not only incapable of being lacking, but also that they need to be coordinated. For example, when the greenhouse lacks carbon dioxide, if it does not apply "gas fertilizer", instead of applying or increasing nitrogen fertilizer, it will increase the carbon and nitrogen nutrient imbalance of the plant and play a "snowening" effect.

Q: How to apply "gas fertilizer" in the greenhouse? A: In order to correct the lack of carbon in crops, chemical and biological methods can usually be used to generate carbon dioxide or carbon dioxide fertilizer. There are three main forms of commercial carbon dioxide fertilizer:

Solid fertilizer. It can be dry ice (solid carbon dioxide) or granules, and dry ice becomes carbon dioxide gas at room temperature for crop absorption and utilization. In particular, people should not be in direct contact with dry ice to prevent cold damage; granules can be directly sprinkled on the ground or buried in the soil, and carbon dioxide gas is produced after water absorption. The dosage is about 40 kg per mu, which can be continuously released within 40 days. .

Liquid fertilizer. When in use, the cylinder containing the liquid carbon dioxide is placed in the protective ground, and the carbon dioxide gas is transported through the pressure reducing valve to the portion where the crop can be fully utilized. A hole is made every 3 mm on the hose, and the diameter of the cylinder is gradually increased from near to far. The cylinder outlet pressure is 1~1.2 kg per square centimeter and is released for 6~12 minutes per day.

Gaseous fertilizer. Double micro carbon dioxide gas is a biological product in which particles contain a large amount of microorganisms and produce carbon dioxide by fermentation. Apply 1 capsule per square meter, the depth is about 3 cm, and the application rate per acre is not less than 6.7 kg. The soil is required to maintain a suitable humidity and temperature and can be continuously released for more than 30 days in a single use.

Simple chemical methods, organic combustion methods and straw bioreactor technology can also be used. The chemical method mainly uses dilute sulfuric acid and ammonium bicarbonate to form carbon dioxide. It is necessary to add sulfuric acid slowly to the water according to the requirements of chemical safety operation. The bioreactor technology is to ditch the straw under the greenhouse or under the planting line. After mixing and fermenting the composite fungicide, it is buried, and the carbon dioxide released by the decomposition of the organic matter is used as a fertilizer.

Q: Some people have doubts about "gas and fat" because it is not used properly, or is it really not obvious? What issues should I pay attention to when using?

A: There are doubts about “gas and fertilizer” mainly because of insufficient understanding and improper application methods. The so-called lack of understanding, first, carbon dioxide is mainly used for vegetables under the conditions of facilities, unlike nitrogen, phosphorus, potassium fertilizer, almost every field, each crop is widely applied; second, it is not recognized that carbon is also an essential nutrient and plant It is necessary to maintain a suitable carbon to nitrogen ratio in the body. If there is too much nitrogen and carbon deficiency, not only the plants are thin and long, but also susceptible to pests and diseases. The problem of the application method is mainly that it is not applied at the most needed place and at a suitable time, so that the application effect is not obvious.

According to this, the application of "gas fertilizer" must pay attention to the following points: First, "gas fertilizer" is mainly used in winter, especially in the early spring before the shed and the long-term crops with more nitrogen fertilizer. Among them, the strong seedling effect applied at the seedling stage is better, and the economic benefit is the highest in the middle and late application of melon vegetables and leaf vegetables in winter; the second is to improve the light conditions of the greenhouse, so that the carbon dioxide can be fully utilized by the crop; Fertilizer must be based on the rational management of nitrogen, phosphorus and potassium fertilizers, especially the rational application of phosphorus and potassium fertilizers and other supporting measures. Fourth, the greenhouse or greenhouse should be closed for a period of time after the application of “gas fertilizer”. In order to increase the concentration of carbon dioxide in the air; fifth, the commercial carbon dioxide fertilizer should be strictly in accordance with the requirements of the product specification, so as not to cause harm to people and crops due to improper application methods.

Q: It is known that the application of “gas fertilizer” in greenhouse vegetables is effective. Can rice, corn, wheat and other field crops also be applied with “gas fertilizer”?

A: Most of the field crops are planted in the open air, and there is generally no shortage of carbon dioxide. However, some experiments have been carried out at home and abroad. The results show that after the application of "gas fertilizer", corn and wheat have increased production in different degrees, but rice does not increase production or even reduce production.

Q: Can you recommend the equipment for producing "gas and fertilizer" for farmers' reference?

A: The development and application of carbon dioxide is earlier in developed countries in the West, but China has developed rapidly in recent years. At present, many manufacturers are producing carbon dioxide fertilizer application equipment, such as carbon dioxide generators, greenhouse intelligent "gas fertilizer" multipliers. There are three main ways in which carbon dioxide occurs: burning organic matter, chemical reaction between sulfuric acid and ammonium bicarbonate, and biological fermentation of organic matter. The so-called intelligent efficiency is the automatic control of the gas generation process through the computer module. Manufacturers or merchants often overstate the product when they sell their products. It is recommended that farmers' friends should consider the effectiveness, quality, price and safety and reliability of the equipment according to their own needs.
Professor of China Agricultural University Wang Xingren Public Daily
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