How to Do High-Temperature Greenhouse Sealing and Disinfection in Summer? A Detailed Guide to Practical Methods
During the season when greenhouse vegetables are rotated, that is, in the high-temperature season of July, August and September, adopting high-temperature greenhouse sealing technology can not only mature the soil, increase organic matter content and improve soil structure, but also eliminate pathogenic bacteria and underground pests caused by continuous cropping, and it is easy to operate with remarkable results.
The high-temperature greenhouse sealing disinfection method involves sealing the greenhouse in summer and using the high temperature of solar heat and chemical fumigation to disinfect the interior of the greenhouse. It is generally carried out from early July to late August. This method has low cost, little pollution, simple operation and good results, and is easily accepted by the public.
?I. Specific Methods of High-Temperature Greenhouse Sealing
Land preparation and fertilization: The land should be leveled and finely prepared, and fertilization should be combined with land preparation to kill pathogens in the organic fertilizer. Apply organic fertilizer, such as chicken manure, pig manure, cow manure, etc., or use plant straw such as corn stalks and rice straw (cut into small pieces 3~5 cm long), plus calcium cyanamide. The amount of organic fertilizer is generally 3000~5000 kg per mu, and calcium cyanamide is 60~100 kg per mu. Spread evenly on the soil surface, then deep plow 25~30 cm. Organic fertilizers such as chicken manure and dry cow manure help raise the ground temperature and maintain it, making the sterilization effect better. After the land is prepared, form ridges or make high and low beds according to the planting method of the crop, so that a small space can be formed between the plastic film and the ground, which helps increase the ground temperature.
Irrigation: Build dams around the greenhouse and irrigate. The water surface should preferably be 3~5 cm above the ground. If conditions permit, cover with old film. Close the greenhouse vents properly and cover the greenhouse film well to prevent rainwater from entering, strictly maintaining the airtightness of the greenhouse, so that the temperature at 10 cm below the surface reaches above 70°C and the soil temperature at 20 cm reaches above 45°C, achieving the effect of sterilization and pest killing. The soil moisture content is closely related to the sterilization effect. If the soil moisture content is too high, it is unfavorable for raising the ground temperature; if the soil moisture content is too low, a good sterilization effect cannot be achieved. Practice has proved that when the soil moisture content reaches 60% of the field maximum water-holding capacity, the effect is best.
Chemical treatment: Use chloropicrin for soil disinfection under plastic film coverage to kill pathogens in the soil. The method is to inject chloropicrin into the bed, digging one hole every 50 sq cm, with a depth of 10~15 cm and 4 ml per hole. In addition, before sealing the greenhouse, spray the inner surface of the greenhouse once with fungicide and insecticide to kill pathogens and pests hiding in the wall cracks.
Sealing the greenhouse: Use greenhouse film and ground film for double-layer covering, strictly maintaining the airtightness of the greenhouse. Under such conditions, the maximum ground temperature at 10 cm below the surface can reach 70°C, and the soil temperature at 20 cm can reach above 45°C. Such a high ground temperature can achieve a sterilization rate of more than 80%.
Disinfection time: The vast majority of pathogens cannot tolerate high temperatures and can be killed after a very short period of heat treatment (about 10 days), such as some damping-off pathogens, cucumber sclerotinia pathogens, cucumber phytophthora blight pathogens, eggplant verticillium wilt pathogens, etc. However, some pathogens are particularly heat-tolerant, such as root rot pathogens, clubroot pathogens and fusarium wilt pathogens and other deep-rooted soil-borne pathogens. Because of their deep distribution in the soil layer, they must be treated for 30~50 days to achieve a better effect. Therefore, when carrying out soil disinfection, the disinfection time should be determined according to the crop planted in the greenhouse and the heat resistance of the corresponding pathogens.
Post-disinfection treatment:
1. After high-temperature greenhouse sealing, biological bacterial fertilizer must be added. If biological bacterial fertilizer is not added, then if the vegetables are attacked by pathogens after planting, there will be no beneficial bacteria to buffer or control the development of the disease, and the vegetables are very likely to suffer large-scale disease, especially root diseases. Before planting vegetables, apply biological bacterial fertilizer evenly into the planting holes at a rate of 80~120 kg per mu to protect the rhizosphere environment and enhance the disease resistance of the plants.
2. Solar heat disinfection has the best effect on soil no deeper than 15 cm, and a poorer disinfection effect on soil deeper than 20 cm. Therefore, after soil disinfection, it is best not to plow again; even if plowing, it should be limited to a depth of 10 cm. Otherwise, pathogens in the lower soil will be turned back up, causing recontamination. Although the solar heat disinfection method cannot thoroughly sterilize the greenhouse, it can greatly reduce the density of pathogens in the field and greatly reduce the chance of crop disease. Its disinfection effect can last for 2 years, so the greenhouse can be disinfected once every 2 years.
II. Effects After High-Temperature Greenhouse Sealing
1. Significantly reduce more than 10 kinds of diseases caused by continuous cropping, such as fusarium wilt, root rot, verticillium wilt, phytophthora blight, gray mold, stem base rot, viral disease, etc.
2. Significantly reduce the damage of root-knot nematode disease. For greenhouses with severe continuous cropping obstacles, strict treatment can basically restore the vegetable yield and quality level to that of a newly built greenhouse.
3. High-temperature greenhouse sealing rapidly composts organic fertilizer, enriches the nutrients in the soil needed by vegetables, degrades toxic and harmful components in the soil, especially pesticide residues in the soil, and creates favorable conditions for achieving pollution-free production.
4. Reasonable application of calcium cyanamide can significantly reduce the nitrate content in agricultural products, alleviate soil acidification and regulate soil pH.