Carbon dioxide concentration problems easily ignored in smart greenhouse greenhouse planting

Why are the vegetables, melons, and flavors of the crops planted in the greenhouse not fragrant, sweet, and tasteless? Why are there many diseases and poor disease resistance of plants in greenhouses? Why can't the yield be greatly increased with sufficient water and fertilizer? These problems are basically due to a phenomenon that the low concentration of carbon dioxide in the air of the greenhouse causes the crops to have a carbon dioxide "hunger", which cannot meet the needs of crop photosynthesis.
1. Current situation of carbon dioxide planting and application
At present, there are more than 50 million mu of greenhouse in China, with an annual output value of about 500 billion yuan, and 80% of the output value comes from winter, spring and autumn. Because of the high output value of vegetables in these three seasons, the greenhouse has been restricted from ventilation for nearly five months, and the carbon dioxide concentration is insufficient, which seriously restricts the output of vegetables. Plants contain more than 95% carbon and water, and less than 5% nitrogen, phosphorus and potassium. Over the past few decades, crops have increased by more than 50% through the application of nitrogen, phosphorus and potassium fertilizers. In the dry matter of plants, organic matter accounts for about 90%, while carbon accounts for about 40% of organic matter, which is a kind of element with more content in plants. The carbon comes from CO2. Therefore, CO2 is of great significance to the biological world.
2. Importance of carbon dioxide
As the main material raw material for plant growth, carbon dioxide is one of the key factors affecting plant growth, development and function. It is not only the substrate of photosynthesis, but also the regulator of primary metabolic process, distribution and growth of photosynthates. It participates in a series of biochemical reactions in plants and has a direct impact on plant growth. The increase of carbon dioxide concentration can not only significantly improve the photosynthesis efficiency of plants, but also promote the photosynthesis of plants by expanding the utilization range of light sources. The concentration of carbon dioxide in the air is relatively stable, with little change, generally 0.03% - -- 0.04%. When the concentration is below 25 ℃, with the increase of temperature, photosynthesis is enhanced, and the organic matter created is increased, and the crops show a vigorous growth state; When the temperature exceeds 30 ℃, the organic matter created by photosynthesis is the same as that consumed by crop respiration, or even less than that consumed by respiration, and the crop stops growing.
3. Reasons for lack of carbon dioxide:
For the need of heat preservation, greenhouse vegetable production in winter often keeps the greenhouse in a closed state, resulting in a relative barrier between the air inside the greenhouse and the outside air, and carbon dioxide can not be timely supplemented. After sunrise, with the acceleration of vegetable photosynthesis, the carbon dioxide concentration in the shed drops sharply, sometimes falling below the carbon dioxide compensation point (0.008% - 0.01%). Vegetable crops can hardly conduct normal photosynthesis, affecting the growth and development of vegetables, causing disease and yield reduction. According to the measurement, the normal concentration of carbon dioxide in the air is 300-500PPM, and plants absorb carbon dioxide in the atmosphere at any time when they are cut in the open air. However, in the closed greenhouse in winter, in order to maintain a certain greenhouse temperature, there is no large amount of ventilation and air exchange outside the greenhouse. It is difficult for crops to absorb carbon dioxide. As a result, the concentration of carbon dioxide in the greenhouse drops to a critical value, which makes it difficult for crops to have physiological reactions and normal photosynthesis. Crops cannot grow normally. Especially when the crops need to conduct photosynthesis after the sun comes out in the daytime, although the light intensity reaches 1000-3000x, they begin to absorb a large amount of carbon dioxide in this period. If the carbon dioxide cannot be replenished in time, the plants will weaken or stop photosynthesis due to lack of carbon dioxide for a long time, which will inevitably affect the yield and quality of crops.
4. Countermeasures
At present, many modern greenhouse greenhouses will be installed with carbon dioxide monitoring points, and manual intervention measures can be taken when the carbon dioxide concentration is too low. It has been proved that the lack of carbon dioxide has become one of the important limiting factors in the production of vegetable in greenhouse. Artificial supplement of carbon dioxide is an important measure to achieve high and stable yield in greenhouse production. At present, there are carbon dioxide generator devices, filling finished carbon dioxide, etc.