Key Points of Winter Field Management Methods for Greenhouse Strawberries
Moisture retention In northern regions, film covering for insulation begins from late September to early October. In addition to double-layer insulation covering with large greenhouses and small arched sheds, winter strawberries can also be protected with measures such as leaf covering.
Temperature and humidity management: In the early stage after planting, maintain 25°C-30°C during the day, and 12°C-17°C at night is suitable, which helps early flowering and fruiting. During the fruiting period, the daytime greenhouse temperature should not exceed 20°C-25°C, and the nighttime temperature should not be lower than 5°C (the temperature regulation target is 10°C). The relative humidity should be around 50%, and humidity is regulated by ventilation.
Topdressing: Follow the principle of light fertilizer applied frequently. Generally, 0.5% compound fertilizer is used for irrigation application. After planting and establishment, apply one light fertilizer, and then apply topdressing once more about 20 days before harvest. Foliar topdressing can also be done with 0.2% potassium dihydrogen phosphate plus 0.4% urea.
Artificial pollination: In winter, there are no insects in the greenhouse to pollinate, so artificial pollination is needed to avoid malformed fruit. Every day from 8-9 a.m., use a brush or cotton ball to apply pollen to the flowers. This has a significant effect on increasing yield and the rate of good fruit.
Pest and disease control: Gray mold is likely to occur in low-temperature and humid weather. Spraying with 50% procymidone powder at 1000-1500 times dilution is effective. You can also use Yixunling No. 1 (chlorothalonil smoke agent) and Yixunling No. 2 (procymidone smoke agent) for fumigation, or use chlorothalonil, carbendazim, and others for control, which also works well.
Gibberellin spraying: When the first heart leaf unfolds, and when 2-3 true leaves and 4-5 true leaves have grown, spray 10 ml/kg gibberellin each time. This can greatly increase yield and improve fruit quality.
Supplementary lighting: During flowering and fruiting, use light bulbs for supplementary lighting and extend the light period by 2 hours per day, which is beneficial for early flowering and early fruiting (large greenhouse with small shed inside; place one 45-60 watt bulb about every 1 m inside the small shed). While supplementing light, the minimum temperature in the small shed can be maintained at about 5°C, so the temperature changes gently, and the harvest period can also be advanced by about 20 days.