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1. Ammonia Ammonia is a harmful gas that often occurs in strawberry cultivation. Mainly from the Chicken manure without compost, pig manure, horse manure, cake fat and so on. In a closed greenhouse, these organic fertilizers produce large amounts of ammonia by high-temperature fermentation. In addition, the excessive application of ammonia carbonate and surface application of urea can also produce large amounts of ammonia. When the ammonia content of the greenhouse reaches 5 to 10 μl/l, it will poison the strawberries. Ammonia invades through strawberry stomata and damages young tissues. For example, flowers, fruits, young leaf margins and other damaged tissues first turn brown, then turn white, and wilting when severe. The ammonia poisoning and high-temperature hazards are often mixed in production, and attention should be paid to the difference. To detect ammonia accumulation in the shed, a pH test paper method can be used to test the pH of the water droplets on the shed film with a pH test paper before sunrise in the morning. Normally, the water droplets in the shed film are neutral. If alkaline reaction is observed, ammonia gas accumulates. The greater the alkalinity is, the higher the concentration of ammonia gas must be. Control measures: 1 The organic fertilizer applied in the greenhouse shall be fully decomposed; 2 Minimal application or non-application of ammonium bicarbonate shall be adopted; when applying urea, furrow application or hole application shall be adopted; 3 In the case of ensuring the temperature requirements, the ventilation openings shall be opened in time. Ventilation.
2. Nitrous gas Nitrite gas mainly comes from unreasonable fertilization. In the soil, especially in sandy soils, a large amount of nitrogen fertilizer such as ammonium nitrate is continuously applied, and the conversion of nitrous acid to nitric acid is blocked, but ammonium The conversion to nitrous acid can be carried out normally. This leads to the accumulation of large amounts of nitrous acid in the soil. When the concentration in the greenhouse exceeds 2 to 3 μl/l after evaporation, nitric acid poisoning occurs. Poisoning occurs in about one month after fertilization. The nitrous acid gas invades the mesophyll tissue through the stomata of the leaf, which firstly damages the cells near the stomata, and then spreads to the spongy tissue and the palisade tissue, causing the chloroplast structure to be destroyed and fade, and gray spots appear. If the concentration is too high, the veins turn white. For the detection of nitrous acid gas, pH test paper can also be used. Contrary to ammonia gas, if the pH value of the water droplets of the greenhouse membrane is acidic, it indicates the accumulation of nitric acid gas. Control measures: First, when topdressing nitrogen fertilizer, it should be applied in batches in accordance with the principle of “a small number of timesâ€, mixed with soil, and timely watered with soil after application; second, ventilation and air exchange are often used in the management of greenhouses; The third is to apply appropriate amount of lime neutralization, generally about 667 square meters Shi 100 grams, in order to increase the pH of the soil to prevent the nitrite gasification.
3. Carbon Monoxide and Sulphur Dioxide Carbon monoxide and sulphur dioxide are mainly produced during the warming process due to insufficient fuel combustion or poor fuel quality. This is a frequent occurrence of harmful gases in greenhouses. In addition, organic fertilizers such as people, animals, feces, and oil cakes, which have not been cooked, can also be used to release sulfur dioxide during decomposition and fermentation. Carbon monoxide is mainly a hazard to operation managers. Sulfur dioxide is harmful to humans and strawberries. When the concentration of sulphur dioxide is around 3 μl/l and stays for more than 1 hour, the strawberries will suffer. Sulfur dioxide damages the functional leaves, and old leaves and new leaves are lighter after being damaged. The symptom of the victim is to first appear spots in the places where the leaves have many pores, and then fade. When the concentration is high, the whole leaves are like hot water. In addition, when the humidity in the air in the shed is high, the sulfur dioxide will be in contact with water to form sulfurous acid, which will fall on the leaves and can directly damage the chloroplast and cause damage to the leaves. To prevent the production of carbon monoxide and sulfur dioxide gas in the shed, in addition to the application of adequately decomposed organic fertilizer and frequent ventilation, the greenhouse should also be selected with high quality fuel, and the combustion should be complete, try not to use direct heating stove heating, stove The flue should be wiped tightly so that no smoke or cigarettes are left.
4. Ethylene and Chlorine Ethylene and chlorine are mainly derived from polyvinyl chloride film. When the temperature in the greenhouse exceeds 30°C, the polyvinyl chloride film will volatilize ethylene and chlorine. When the concentration reaches 1 μl/l or more, It will affect the growth and development of strawberries and cause symptoms of damage. Ethylene is mainly to accelerate the aging of strawberries. Leaves aging, resulting in the separation layer, resulting in the loss of flowers, fruits, leaves, or the fruit did not grow to the proper size and premature maturation and soften, reduce production and economic benefits. Chlorine can make the leaves of strawberry yellow, white and wilting. Control measures: 1 Try to use a safe, reliable, low-temperature, anti-aging special greenhouse membrane; 2 to strictly control the temperature of the greenhouse below 30 °C; 3 If you find ethylene or chlorine harm in the greenhouse, you should immediately replace the film. If it cannot be replaced, vents should be opened during the day to open doors and windows to increase ventilation. 4 Avoid storing stale films and plastic products in the shed to prevent harmful gases from escaping at high temperatures.
5. The plastic shed film or other plastic products produced by using diisobutyl phthalate with diisobutyl phthalate as a plasticizer are exposed to high temperatures in the shed, and the diisobutyl ester will continue to develop. Released and accumulated to a certain degree, it will cause harm to strawberries. Symptoms are the tenderness of new leaves and tip color fade, gradually yellowing, whitening, and severely litter. Control measures: First of all, do not choose plastic shed films made of diisobutyl phthalate as a plasticizer; secondly, avoid high temperatures in the sheds; in addition, ventilate frequently to vent harmful gases.
In greenhouse strawberry cultivation, due to various reasons, a variety of harmful gases often occur in the greenhouse. When the harmful gas reaches a certain concentration, it will cause varying degrees of harm to the strawberry and the management personnel. Therefore, we must take appropriate measures to prevent and control.