Carbon dioxide is a raw material for photosynthesis of green plants, and its concentration directly affects the photosynthetic rate. Experiments have shown that cucumber, tomato, pepper and other fruits and vegetables have an average yield increase of 20%~30% compared with no fertilization , and can increase fruit number and fruit weight, improve quality; leafy vegetables and radish and other root vegetables have a greater yield-increasing effect.
1 reasonable time and concentration of fertilization
Applying carbon dioxide fertilizer at the seedling stage is beneficial to shortening the seedling age, cultivating strong seedlings, early flower bud differentiation, and improving early yield. Fertilization at the seedling stage should be carried out as early as possible. Fruits and vegetables are generally not fertilized after planting until flowering, and fertilization is started after flowering and fruit setting, mainly to prevent overnutrition and plant growth; leafy vegetables are fertilized immediately after planting.
During the day, the time of carbon dioxide fertilization should be arranged according to the law of carbon dioxide changes in the facility environment and the photosynthetic characteristics of the plants. The solar greenhouse in our county can be arranged after 0.5 hours in the morning . The temperature in the greenhouse is rising at noon. If ventilation is needed, it should be finished 0.5 hours before ventilation . If it is not ventilated, release it for 3~4 hours. .
The concentration of carbon dioxide applied in different vegetables should be different. Tomato, cucumber, zucchini, and pumpkin are suitable for 750~1000 mg / L, and eggplant, pepper and strawberry are suitable for 550~750 mg/L. Do not fertilize on rainy days.
2 fertilization method
2.1 Organic fermentation method. Human, animal manure, crop straw, weed stems and leaves, etc. produce carbon dioxide during fermentation, which is simple and easy, low cost, but difficult to adjust.
2.2 Liquid carbon dioxide fertilization method. The sources of liquid carbon dioxide are mainly brewing industry, chemical industry by-products, air separation, underground storage and so on. The liquid carbon dioxide gas source is relatively pure, does not contain harmful substances, is convenient to apply, safe and reliable in use, but high in cost.
2.3 combustion method. Carbon dioxide is produced by burning a liquefied petroleum gas, propane gas, natural gas, white kerosene, etc. by a carbon dioxide generator. This method is convenient to apply and easy to control. This method is often used in facility cultivation in Europe and the United States.
2.4 Chemical reaction method. Carbon dioxide is produced by the reaction of a strong acid (sulfuric acid, hydrochloric acid) and a carbonate. Sulfuric acid - ammonium bicarbonate is currently the most widely used type. In recent years, China has successively developed a variety of complete carbon dioxide fertilization devices. The main structures include acid storage irrigation, reaction barrels, carbon dioxide purification absorption tanks and air guiding tubes. The amount of carbon dioxide produced by sulfuric acid supply is simple, safe and effective. it is good. Using 2.5 kg of ammonium bicarbonate per standard mu of greenhouse ( volume of about 1300 cubic meters ) can achieve a carbon dioxide concentration of about 900 mg / liter.
2.5 Application of granular organic biogas fertilizer method. The granular organic biogas fertilizer is evenly applied to the plant rows at a certain interval, and the application depth is 3 cm, and the soil in the acupoint soil is kept to have a relative humidity of about 80% , and carbon dioxide is generated by the soil microbial fermentation. This method is convenient and safe to use, but the storage conditions are extremely strict. The speed of releasing carbon dioxide is affected by temperature and humidity, which is difficult to control by humans.
3 other environmental factors regulation and precautions 　　
3.1 Large temperature difference management system can improve the effect of carbon dioxide fertilization. Adding carbon dioxide at higher temperatures and strong light during the morning is conducive to photosynthesis to produce organic matter, while ventilation is increased in the afternoon, and there is lower temperature at night. Increasing the temperature difference is beneficial to the operation of photosynthetic products, thereby accelerating crop growth and photosynthesis. The accumulation of organic matter.
3.2 Strengthen the management of fertilizer and water, and rationally arrange the amount of fertilizer. At the same time as carbon dioxide fertilization, the supply of water and nutrients must be increased to meet the physiological and metabolic needs of crops. The application of nitrogen fertilizer should be emphasized, and the photosynthetic function of the leaves should be improved by adding nitrogen fertilizer. In addition, long-term, high-concentration use of carbon dioxide can also have harmful effects on crops, such as aging plants, leaf rewinding, chlorophyll decline, etc., so in practice the application concentration should be slightly lower than the optimum concentration, and appropriate reduction in application frequency.
3.3 Efficient use of fertilizer sources to reduce waste. Since carbon dioxide is heavier than air, in order to uniformly apply the added carbon dioxide to the functional leaves of the crop, the carbon dioxide generating device or the gas pipeline should be placed at the height of the canopy of the plant population, and multiple points should be applied or increased on the application tube. The number of holes is used to ensure uniformity and the carbon dioxide to be applied is fully utilized. During the application of carbon dioxide, the shed should be kept relatively closed to prevent carbon dioxide gas from escaping outside the shed to increase carbon dioxide utilization and reduce production costs.
3.4 Pay attention to operational safety. The sulfuric acid used in the chemical reaction is highly corrosive. Therefore, attention should be paid to the safety of use. When diluting sulfuric acid, the sulfuric acid should be poured into the water along the wall to strengthen the mixing. The container should not use metal materials. Wear protective gloves and glasses when handling. Prevent the operator's skin and clothing from being burnt; when the reaction is completely terminated, the residual liquid is fully diluted and reused to prevent the residual acid from harming the crop.
Guangzhou Jointair Co., Ltd. , https://www.jointair.cn