Flower watering methods for the four seasons and tips for preventing harmful gas damage in greenhouses

Flowers in plastic tunnels and greenhouses often grow under closed conditions in the depths of winter. Because the temperature inside is relatively high, the humidity is relatively high, and ventilation is poor, flowers in the growing period are very easily harmed by harmful gases, causing poor plant growth and development, and in severe cases, after a period of time, they wither and die. Therefore, special attention should be paid to the occurrence and prevention of harmful gases in plastic tunnels and greenhouses. Several common types of gas damage

1. Ammonia poisoning: Applying unrotted livestock manure, cake fertilizer, or excessive urea, ammonium bicarbonate, and other fertilizers in the tunnel produces a large amount of ammonia gas during fermentation and decomposition. When the ammonia concentration is greater than 5 ppm, ammonia gas invades cells through leaf stomata, destroys chlorophyll, causes water-soaked spots at the tips of the affected leaves, and turns the leaf margins yellow and brown, and then the leaves dry up. Ammonia damage mostly occurs on the outer leaves of the plant, and new leaves are especially severely affected.

2. Nitrous acid gas poisoning: Applying too much ammonium nitrate in the tunnel hinders soil nitrification, causing large accumulations of nitrous acid gas. When the concentration reaches 2 ppm, poisoning symptoms appear. It often occurs on the middle leaves of the plant; the affected leaves develop irregular greenish-white spots, and when the concentration is too high, the entire plant dies.

3. Sulfur dioxide poisoning: Sulfur dioxide gas produced during heating generally invades through the stomata on the underside of the leaves, destroys chloroplasts, causes tissue dehydration, and forms white spots on the affected parts, which then dry up. In severe cases, the leaves of the entire plant become a green net-like pattern, and the leaf veins also dry up quickly.

4. Carbon monoxide poisoning: When coal fire heating is used in the tunnel, incomplete combustion or poor ventilation produces a large amount of harmful carbon monoxide. When the concentration reaches 2 to 3 ppm, it causes harm to some herbaceous flowers. On the affected leaves, the leaf surface and vein tissues first become water-soaked, then turn white and yellow, and finally become irregular necrotic spots.

5. Sulfurous acid poisoning: Applying large amounts of ammonium sulfate, potassium sulfate, and unrotted cake fertilizer in the tunnel produces sulfur dioxide gas through decomposition. When this gas encounters water droplets, it forms sulfurous acid, which directly destroys the chlorophyll in the leaves. After the cells near the stomata of the poisoned leaves die, round or diamond-shaped white "smoke spots" appear, and the leaves gradually wither and fall off.

6. Plastic film toxic gas poisoning: Plastic films using diisobutyl phthalate or n-butyl phthalate as plasticizers easily volatilize toxic and harmful gases such as ethylene, propane, trichloropropane, and tetraamylene alcohol at high temperatures. When these accumulate to a certain concentration, they can poison some flowers, causing the leaves to lose green and become yellow, turn white, dry up, and shrivel.

Comprehensive prevention and control of common gas damage

1. Rational fertilization: Fertilizing flowers in greenhouses should be based mainly on high-quality soil and miscellaneous fertilizers, appropriately increase the application of phosphorus and potassium fertilizers, and apply nitrogen fertilizer as little as possible. Nitrogen fertilizer should be applied mainly as base fertilizer, with topdressing as a supplement. Do not apply cake fertilizer or human excrement and urine, and especially do not apply chemical fertilizers containing nitrogen and sulfur compounds. When fertilization is needed, it should be carried out strictly according to the topdressing principle of "small amounts, many times." For seedlings raised in the tunnel, as long as the seedlings grow normally, no topdressing is needed. If the seedlings are weak, foliar spraying should be done at 11 a.m. on sunny days in winter, and in spring it should be sprayed after ventilation.

2. Timely ventilation and air exchange: Without affecting the temperature, increase the time for ventilation and air exchange as much as possible to expel toxic and harmful gases and make the gas composition inside the tunnel close to that outside. In winter, generally open the door for ventilation at 8 to 9 a.m. In spring, the ventilation time gradually lengthens; especially at noon, do not forget to open the door for ventilation. On cloudy days, ventilate as much as possible at noon. Even on rainy and snowy days, carry out short periods of ventilation and air exchange at noon to minimize toxic gases in the tunnel and reduce air humidity.

3. Careful management to reduce toxic sources: When coal fire heating is used in the tunnel, special attention should be paid to ensuring full combustion of the fuel, and a chimney should be installed on the stove to conduct harmful gases outside the tunnel. At the same time, pay attention to ventilation and air exchange to prevent harm caused by carbon monoxide and carbon dioxide.

4. Choose non-toxic plastic films: Try not to use toxic plastic films to which plasticizers or stabilizers have been added. Ethylene synthetic resin plastic films can be chosen to reduce toxic sources and prevent harm.