Correct Methods for Watering Greenhouse Vegetables in Winter

Watering greenhouse vegetables in winter refers to the routine farming operation of managing moisture for various vegetables in greenhouses or plastic tunnels during the low-temperature season. Because winter brings low temperatures, weak sunlight, high humidity inside the greenhouse, and slow water evaporation, vegetables need noticeably less water than in other seasons, and improper watering can easily lead to root rot, yellowing leaves, and frequent disease outbreaks.

The first principle of watering is to watch the weather, the soil, and the plants. Generally, watering is done in the morning on a sunny day, when the temperature difference between the water and the soil is small and there is still time afterward to raise the temperature and vent moisture; watering is usually avoided on cloudy days, rainy or snowy days, or before a cold wave arrives. When the soil surface turns white and the plants wilt slightly at noon, it indicates a lack of water and they can be watered; if the soil is still moist, watering should be postponed.

As for methods, drip irrigation under plastic film or concealed irrigation under film is recommended, following the practice of frequent light watering and watering the furrows without flooding the ridges, so as to avoid flood irrigation causing a sudden drop in soil temperature and a sharp rise in humidity. Growers with the means can use pre-warmed water, or store water in advance inside the greenhouse to raise the water temperature, reducing the shock to the root system from cold water.

Management after watering is equally important. After watering, the greenhouse can be closed briefly to raise the temperature, then promptly ventilated to remove moisture, shortening the time dew remains on the leaves and reducing the occurrence of high-humidity diseases such as gray mold and downy mildew. Combined with intertillage and loosening of the soil, this can also preserve soil moisture and promote root respiration.

In general, the key to watering greenhouse vegetables in winter is doing it at the right time and in the right amount, preferring dry over waterlogged, and combining moisture management with heat preservation and ventilation, so as to help vegetables overwinter safely and grow normally.