Beware of Harmful Gas Damage to Greenhouse Vegetables in Winter

Greenhouse vegetables often suffer from gas damage and wind damage in winter, and vegetable growers are reminded to pay attention to this.

I. The Harm and Prevention of Gas Damage

Gas damage can often scorch vegetables in a relatively short time, causing large reductions in yield and serious declines in quality.

1. Ammonia. When large amounts of organic fertilizers such as inadequately decomposed chicken manure, human excrement and urine, and cake fertilizer, as well as fertilizers such as urea, are applied in a greenhouse, under high-temperature conditions they can ferment and decompose within 3 to 4 days to produce large amounts of ammonia. Ammonia enters through the stomata of the leaves, and the damaged parts are mainly the leaves, showing water-soaked lesions, with the leaf color becoming lighter, whitening, or turning light purple, and the leaf margins appearing scorched. Damage often occurs throughout the whole greenhouse, and the upper leaves of the plants are more severely affected; in serious cases, the plants can die. Cucumber, tomato, pepper, and celery are the most sensitive to ammonia and suffer the most severe damage.

2. Nitrous acid gas. After a large amount of organic fertilizer and ammonium nitrate is applied at one time in the greenhouse, when the soil changes from alkaline to acidic, a large amount of nitrous acid gas is released from the soil. Affected leaves develop water-soaked irregular chlorotic white spots or brown spots, and in severe cases the mesophyll tissue all turns white and dies; when the concentration reaches 10 mg/kg, the leaf veins also turn white and die. Vegetables such as tomato, eggplant, lettuce, and pepper are relatively sensitive to nitrous acid gas.

Preventive measures: First, fertilize reasonably. Do not apply large amounts of inadequately decomposed organic fertilizers such as chicken manure, cake fertilizer, and human excrement and urine, or chemical fertilizers such as urea and diammonium phosphate, at one time in the greenhouse. Compost fermented with enzyme bacteria or fully decomposed organic fertilizer can be used, and formula fertilization should be adopted to reduce the amount of chemical fertilizer used. At the same time, pay attention to choosing reasonable fertilization methods. When topdressing chemical fertilizers such as urea and diammonium phosphate, they should be applied by burying and then watered, so as to avoid the volatilization of harmful gases as much as possible. Second, ventilate and exchange air. In the management of greenhouse vegetables, attention should be paid to frequent ventilation to reduce the accumulation of harmful gases in the greenhouse. After topdressing, ventilation and air exchange should be strengthened around noon when the temperature is relatively high, to speed up the release of harmful gases.

II. The Harm and Prevention of Wind Damage

Draft wind is the rapid convection of cold air caused by the door or ventilation opening of a greenhouse not being closed tightly in winter. This kind of wind has a very large impact on vegetable growth. After a burst of cold wind strikes, vegetables may at best grow poorly, and at worst their leaves may wilt and flowers and fruits may drop. Although its destructive power is smaller than that of gas damage, it often gives vegetable growers severe headaches. The most effective measure to prevent draft wind is to install wind-blocking film at the door and ventilation openings to buffer the direct blowing of draft wind on vegetables. Especially at the door, in addition to installing wind-blocking film, it is best to hang a cotton door curtain on the greenhouse door, which both preserves heat and blocks wind, and can effectively block the entry of draft wind. For vegetables harmed by draft wind, foliar fertilizer or plant growth regulators should be sprayed on the leaves in a timely manner to promote their recovery as quickly as possible.

Xinji Plant Protection Station Chen Shuqiao