How to Prevent Low-Temperature Damage in Overwintering Tomatoes? A Full Breakdown of Management Points
As the deep winter season arrives, temperatures gradually drop, and overwintering tomatoes grown in greenhouses face the test of low temperatures. So how should overwintering tomatoes be managed? Experts advise that low-temperature damage must be prevented!
1. Overwintering tomatoes must be protected against low-temperature damage
Tomato is a warmth-loving crop, and during winter and spring cultivation it is easily damaged when exposed to low temperatures or frost. If the greenhouse temperature remains at 5-10°C for a long time, the plant leaves will turn dark green or take on a water-soaked appearance; if kept for a long time in a low-temperature environment below 5°C, the leaves will lose their green color due to cold damage and become whitened.
To prevent low-temperature damage in tomatoes, on the basis of selecting cold-resistant varieties tolerant of low temperatures and weak light, greenhouse insulation should be strengthened, such as thickening earth walls, increasing the density of straw mats, and adding small arched tunnels. When a sudden temperature drop occurs, temporary heating measures such as burning coal stoves should be taken. When necessary, a mixed solution of brown sugar and potassium dihydrogen phosphate can be sprayed.
2. Good disinfection for overwintering tomatoes
For overwintering tomatoes, the low temperature and weak light of winter cause excessive humidity inside the greenhouse, creating an extremely favorable environment for the occurrence of various diseases. Under such conditions, in order to reduce disease occurrence in winter, disinfection work before overwintering is especially important. One main goal is to lower the pathogen base and strengthen the plants' ability to resist pests and diseases, so as to do a good job of prevention at the root and achieve the purpose of reducing disease occurrence.
3. Fertilizer management for overwintering tomatoes
Overwintering tomatoes have a long growth period, and vegetable growers often apply very large amounts of fertilizer. In many greenhouses, after 2—3 years, green moss appears on the soil surface, which is soil salinization. If management is not strengthened, the soil will deteriorate further, and yields will decline year by year; after 6—7 years the entire greenhouse will be ruined. Therefore, balanced fertilization should be emphasized in fertilizer use. The specific measures are as follows:
When applying base fertilizer before planting, organic fertilizer and inorganic fertilizer must be used in combination. For newly built greenhouses, use decomposed chicken manure plus cow manure as organic fertilizer, and the inorganic fertilizer per mu should be diammonium phosphate, potassium sulfate 5, medium and trace element fertilizer, and calcium fertilizer, then add microbial bacterial fertilizer. Note that 3/4 of the inorganic fertilizer should be broadcast and 1/4 applied in furrows to ensure fertilizer efficiency. For topdressing, at the first truss fruit stage, 10 kg per mu of a macroelement water-soluble flush fertilizer with medium nitrogen, low phosphorus, and high potassium, Dalipu, can be selected to promote fruit enlargement before the cold. When fertilizing in the severe cold season, a rooting, root-nourishing, cold-resistant seaweed acid chitin flush fertilizer can be selected together with the plant awakening agent Danengshou. After the Beginning of Spring, potassium nitrate flush fertilizer with a potassium content above 40% can be selected at 15 kg/mu. After that, apply fertilizer once every other watering as appropriate, and stop topdressing when the last truss fruit reaches egg size. Note that fertilizers should be selected from formal manufacturers.
For foliar fertilization, boron fertilizer should be sprayed regularly throughout the flowering period to promote flower organ development. After fruit set, especially during the peak fruiting period, calcium fertilizer can be sprayed to prevent blossom-end rot. In the late growth stage, potassium dihydrogen phosphate solution can be sprayed to prevent premature aging.
4. Use smoke agents and dust agents to prevent pests and diseases
Most diseases that occur in overwintering tomatoes during consecutive cloudy and rainy days are caused by high humidity and low temperature, so the premise of prevention is not to increase indoor humidity. Using smoke agents and dust agents to control pests and diseases has a good effect and at the same time will not increase the humidity inside the greenhouse.
5. Reasonable watering
After overwintering tomatoes are watered at planting, the seedling recovery water should be given 2—3 days later. If the seedling recovery water is given too late, there will be no time for hoeing, and the seedlings will grow tall and large, making it difficult to cover with film. The first fruit-forcing water is the most critical watering. If given too early, the plants will grow excessively and the first truss fruits will not grow large; if given too late, the plants will be checked in growth, the upper stems will be thin and weak, and in severe cases premature aging will occur, that is, an imbalance between vegetative growth and reproductive growth. Therefore, the watering time should be controlled when 80% of the first truss fruits are at ping-pong ball or egg size. In the severe cold season, watering is generally not done. If watering is needed, choose several consecutive sunny days and use small furrow irrigation.