With the gradual lowering of temperature, many vegetable farmers are less and less ventilated to greenhouse vegetables. The harmful gases in the shed will gradually accumulate. Some vegetable farmers reflect the stench in the shed, and the roots and leaves are also seriously damaged. The roots absorb nutrients. Difficulties, the leaves are yellow and dry, and even dead trees appear. Analysis of the reasons, mainly caused by harmful gases such as ammonia in the shed.
Most of the gas hazards that occur in late autumn and winter are fertilizers with high nitrogen content such as manure or urea. The ammonia gas generated during fermentation or conversion process volatilizes, accumulates in the air, and causes problems such as dryness of yellow leaves. Overwintering cucumbers and other cucumbers are concentrated in October, and early spring vegetables are planted in December. Many vegetable farmers used to use manure as a base fertilizer before changing. Commonly used dried chicken manure, rice husk, fresh chicken manure, etc. If it is not fully decomposed or decomposed, it will slowly accumulate and fertilize after being applied to the soil, and ammonia accumulation may occur. When manure is used more often, gas damage may still occur in the last two months.
In addition, if the topdressing nitrogen content is too high, gas damage may also occur. If the humidity in the shed is small, the ground temperature is high, and a large amount of ammonia gas may be decomposed after 3 to 4 days after topdressing. Ammonia gas is usually judged by the smell, and ammonia gas is usually accompanied by a noticeable odor, which can be smelled in the shed. When the ammonia concentration in the shed exceeds 5 mg/L, some sensitive vegetables, such as cucumber and tomato, will be damaged. The original leaves are like hot water, and become brown after drying.
After about half a month of topdressing, if you use more fertilizer at one time, especially if potassium nitrate or calcium nitrate is used too much at one time, nitrite gas may appear, and the phenomenon of gradually bleaching between veins may occur. In addition, the use of smoke agents is not appropriate, there may be gas damage problems, need to pay attention.
Solution: Improve the ratio of base fertilizer + reasonable response to cloudy days.
1. Improve the ratio of base fertilizer. Adjusting fertilizer is the basis for reducing the generation of harmful gases such as ammonia. After the wintering and early spring vegetables are planted, it is the lowest temperature in the whole year and the least ventilation period. In the use of base fertilizer, we must choose the type with high safety and adopt the principle of “less and fineâ€. Rice husk and dry chicken manure cannot be used in large quantities, and fresh chicken manure should be banned. It is recommended to use fermented chicken manure, soybean meal and organic fertilizer instead. Topdressing should also avoid excessive use of one-time fertilizer, generally 5 to 10 kg per mu.
2. A reasonable response to cloudy days. Gas damage usually occurs when the temperature is low on a cloudy day and it is difficult to ventilate. At this time, attention should be paid to short-term interval ventilation to achieve both temperature and ventilation, and ventilation should be avoided as much as possible to avoid accumulation of harmful gases.
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