Gas damage and control in greenhouse vegetables
Ammonium Nitrate Phosphor,Ammonium Nitrate Phosphor 27-5-0,Ammonium Nitrate Phosphor 29-5-0,Ammonium Nitrate Phosphor 27-13-0 SHANXI HUAXIN FERTILIZER CORP. , https://www.sxhuaxingroup.com
In the cold season, plastic greenhouses are not ventilated, and the temperature inside is high, the humidity is high, and the vegetables that grow vigorously are easily damaged by harmful gases, which makes the plants grow and develop poorly, and can cause wilting and death in severe cases.
First, the type of harmful gas and harm
I. Ammonia and nitrous acid gas. Mainly from the application of soil nitrogen fertilizers and organic fertilizers, especially in the case of excessive fertilization and in the case of soil drought. When the fertilizer encounters high temperature in the shed, it will decompose and produce a large amount of ammonia in a short period of time (3-4 days after fertilization). When the concentration of ammonia exceeds 5×10-6, some sensitive vegetables such as cucumber and tomato will be damaged. The original leaves will be brown after being boiled, and become brown when dried. When the concentration of ammonia reaches 4%, vegetables The seedlings died within 24 hours. When the content of nitrous acid gas reaches 2×10-6-3×10-6 in air, it will cause damage to sensitive vegetables such as eggplant, tomato and pepper. The symptoms mainly occur on the leaves close to the ground, and rarely damage new leaves. At the beginning, it was also like being boiled by boiling water. Later, due to the acidification of nitrous acid, the veins gradually became white. In severe cases, only the veins were left, and the mesophyll was bleached and died. This situation occurs mostly 10-15 days after fertilization.
To test whether there is an excess of ammonia and nitrous acid in a plastic greenhouse (or greenhouse), the easiest and most common method is to determine the pH of the drops on the top of the greenhouse. Under normal circumstances, the pH of the water droplets is 7-7.2, which is neutral or slightly alkaline; if the water droplets are alkaline, it means that the ammonia is too much; if the water droplets are acidic, the nitrous acid gas is too much, and the pH is 5 Below .5, it will cause damage.
2. Carbon monoxide and sulfur dioxide gas. When the plastic greenhouse is heated by coal fire, a large amount of carbon monoxide and sulfur dioxide gas will be generated due to incomplete combustion or unclear flue. These two kinds of gases can be divided into three types: one is recessive poisoning, the vegetable itself has no visible visible damage, but the assimilation machine bear is reduced, the quality is worse, and the yield is not affected; the second is chronic poisoning, gas Intrusion from the stomata at the back of the blade, brown spots appear on the stomata and its surroundings, the surface is yellowed; the third is acute poisoning, which produces albino symptoms similar to nitrous acid gas.
3. A toxic gas emitted from a plastic film. Some plastic films produce volatile substances such as ethylene, chlorine, isobutyl ester, etc., and invade the interior of the plant, which significantly reduces photosynthesis and seriously affects the yield and quality of vegetables. When the amount of isobutyl ester dissolved in the water droplets of the shed film reaches 10×10-6-20×10-6, the water droplets will be seriously poisoned after being atomized or absorbed by the roots and leaves, and the chlorine gas in the air will occur. When the concentration reaches 0.1×10-6, most vegetables can be damaged by only touching for 4 hours. Initially, white or light brown irregular spots or blocky spots appear between the veins. In severe cases, the whole leaves become white or even fall off. When the concentration of ethylene gas in the protected area reaches 1×10-6, the leaf edge and vein of the vegetable can be yellowed, and then whitened until it dies. Ethylene can also droop the leaves of various vegetables and inhibit the tomato seedlings; in the concentration range of 0.1×10-6-3×10-6旷, flowers, buds and young fruits will appear in tomato and eggplant. And the leaves are abnormally falling off.
In the case of excessive use of aerosol-based pesticides in greenhouses (or greenhouses), it can also cause damage to vegetables. If the chlorothalonil fuming agent is used in excess, the top and edge tissues of the vegetables will die and die. Under high temperature and high humidity conditions, the damage will be more serious.
Second, the prevention and control measures
1. Scientific fertilization. Mainly based on high-quality soil and mixed fertilizers, appropriate application of phosphorus and potassium fertilizers, use of Nitrogen Fertilizer as little as possible, no application of cake fertilizer and human waste, and insist on supplementation with base fertilizer as the main fertilizer. Topdressing should be strictly in accordance with the principle of “small number of times†to prevent excessive fertilization. When applying urea, it is better to not exceed 0.6 kg per 10 square meters. The method of topdressing is to apply deep ditching. After application, the soil is flattened and watered in time to dilute the fertilizer.
2. Timely ventilation. When the temperature is high at noon, open the vents to circulate the air. Even on cloudy or snowy days, perform a short ventilation at noon.
3. Reduce the source of poison gas. When using coal fire to heat, the fuel should be fully burned, and the chimney should be installed to remove harmful gases out of the shed.
4. Use a non-toxic plastic film. A plastic film containing a large amount of plasticizer is not used as a film.
5. Remedy. When the greenhouse vegetables were found to be harmful to sulfur dioxide, timely spray strontium carbonate, stone, gray water, stone sulfur mixture or 0.5% synthetic washing solution. Cucumber suffers from ammonia gas, and sprays 1% vinegar solution on the opposite side of the leaf, which has obvious effect of reducing damage.
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