In the cold winter and spring seasons, fruit trees grown in greenhouses are often exposed to harmful gas due to high temperature, high humidity, and poor ventilation, which results in poor growth and development of fruit trees and serious fruit drop and fruit drop. The method for controlling the air pollution in fruit trees is introduced as follows.
First, ammonia. The ammonia gas in the fruit tree plastic shed is mainly derived from unfaded animal manure such as chicken and duck dung, fresh pig manure, horse manure, and cake manure. These fertilizers produce large amounts of ammonia after high-temperature fermentation. Because the plastic greenhouse is relatively closed, ammonia gas will accumulate. In addition, the application of ammonium bicarbonate in large quantities will also produce ammonia gas. When the ammonia concentration reaches 5 to 10 mg/L, it will have a toxic effect on fruit trees. Adjustment method: 1 In order to reduce the toxicity of ammonia gas, fertilizer should be applied to fruit trees in greenhouses. After fully decomposing organic fertilizers should be applied, phosphorus and potassium fertilizers should be added appropriately. As far as possible, no ammonium bicarbonate, no cake and human waste shall be applied, and adherence shall be Basal fertilizer is mainly based on top dressing. Topdressing must strictly follow the principle of “a small number of times†to prevent excessive fertilization. Plastic sheds should be applied with fully decomposed organic fertilizers. As far as possible, no ammonium bicarbonate should be used. When the temperature permits, open the vents and adjust the ventilation. 2In the production process, if there is ammonia accumulation in the test chamber, a simple pH test method can be used. Before sunrise in the morning (before venting), the water droplets in the plastic shed film were added dropwise to the pH test paper. The alkaline reaction confirmed the accumulation of ammonia gas.
Second, sulfur dioxide. General fuels (especially coal) contain sulphur, and when fruit trees are heated by coal fire, sulphur dioxide is produced after combustion. Generally from the stomata on the back of the leaves invade the cells, destroy the chloroplast tissue, resulting in dehydration, white spots and dryness of the affected leaves; when severe, the leaves of the whole plant turn into a green mesh, and the veins become dry brown. Preventive measures: (1) When the crop is found to be exposed to sulfur dioxide, spray it with barium carbonate, lime water, lime sulfur or 0.5% synthetic detergent. 2 Clean the leaves of the fruit with clean water.
Third, carbon monoxide. When the fruit tree shed is warmed, a large amount of carbon monoxide is easily generated due to incomplete combustion or poor ventilation, which may cause damage to some herbaceous flowers. The victim leaves fade, and the leaf veins on the surface of the leaf first become water-stained, then turn white and turn yellow, and eventually become irregular necrotic lesions. Preventive measures: When coal-fired heating is applied to the sheds, fuel should be burned as much as possible, and chimneys should be installed on the stoves to export harmful gases out of the fruit shed.
Fourth, nitrous acid gas. The nitrite gas in the fruit tree plastic shed is mainly derived from the unreasonable application of nitrogen fertilizer. Continuous application of a large amount of nitrogen fertilizer in the soil will lead to the accumulation of nitrous acid in the soil, which will cause the damage of nitrous acid gas after volatilization. To prevent nitrous acid gas hazards: 1 to apply topdressing nitrogen fertilizers, not a large number of topdressing nitrogen fertilizers. 2 To ventilate and ventilate in time. In the case of not affecting the temperature, extend the ventilation and ventilation time as much as possible to exclude toxic and harmful gases in the shed and exchange fresh air so that the gas composition in the shed is close to the gas composition outside the shed. In the winter, the air is usually opened at 8 to 9 in the morning. With the rise of temperature in spring, the ventilation time is gradually extended. When the temperature is high at noon, ventilation is carried out on cloudy days. Even in the rain and snow, it is necessary to conduct ventilation for a short time at noon in order to reduce harmful gases in the shed as much as possible. 3 If it is determined that nitrous acid gas is present and harmful, the soil in the greenhouse can be properly applied to lime.
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