In winter, watering greenhouse vegetables should be scheduled on sunny days, preferably with several consecutive sunny days following irrigation. It’s best to choose the morning for irrigation as there’s minimal temperature difference between the water and soil, and the soil temperature can recover quickly.
Avoid watering at noon when high temperatures may affect the physiological functions of the roots. Similarly, avoid watering in the evening or during snowy weather to prevent excessive humidity in the greenhouse, which can lead to increased vegetable diseases.
When greenhouse vegetables suffer from severe water shortage, the plants wilt, and the leaves become scorched. Conversely, excessive water can lead to oxygen deficiency in the soil, causing root suffocation and rot, resulting in yellowing or even death of stems and leaves. During winter, with low irrigation temperatures and minimal ventilation, water consumption is reduced.
Therefore, it’s advisable to irrigate sparingly. When the temperature inside the greenhouse is low, the amount of water should be small, and the intervals between watering should be long to avoid overwatering and root rot caused by low temperatures and high humidity.
For winter greenhouse irrigation, it’s preferable to use groundwater directly for irrigation. If using cold surface water, the water temperature should not be lower than 2°C to 3°C. Ideally, the water temperature for irrigation should be as close as possible to the soil temperature at the time of watering.
Micro-irrigation is recommended for greenhouse vegetable irrigation, especially in winter. Micro-irrigation plays a significant role in improving the growth environment for crops, balancing the water, fertilizer, air, and heat needed for crop growth, particularly in the early to mid-stages of growth.
It promotes root growth, regulates greenhouse humidity, and reduces the occurrence of pests and diseases. Micro-irrigation also effectively controls water usage, reduces deep percolation and fertilizer loss, improves soil structure, and enhances crop growth and vegetable quality.
On the day of watering, to quickly restore soil temperature, it’s advisable to seal the greenhouse to raise the temperature rapidly, using air temperature to promote soil temperature. Once the soil temperature rises, promptly ventilate to reduce the temperature to the appropriate range, especially for plants that prefer a monotonous air environment.
Watering during the seedling stage is mainly to increase temperature and moisture retention and often involves cultivation. After the seedlings grow, cultivation is usually discontinued to avoid root damage.