Temperature control of watermelon in greenhouse during the melon period

The greenhouse temperature is maintained at about 30 ~ during the day, 15 ~ 20℃ at night, and the temperature difference between day and night is 10 ~ 15℃. At this time, the air humidity in the shed should be 60%.

Four key points of watermelon expansion management in greenhouse;

First, topdressing swollen melon fertilizer

Potassium fertilizer should be applied again during the expansion period of melon, with appropriate amount of nitrogen fertilizer. Potassium dihydrogen phosphate (225kg/hm2), urea (175kg/hm2) or compound fertilizer (375-525kg/hm2) can be applied. When conditions permit, organic fertilizers such as decomposed oil cake, chicken manure and pig manure can be applied appropriately to improve the quality of watermelon. Fertilization can be selected as topdressing once or twice (fruit diameter is about 5cm).

Second, rational irrigation.

Watermelon needs enough water to grow during the melon growing period, but irrigation must be appropriate and even, usually once every 5-7 days to keep the soil dry and wet all the time. At this time, if the soil is dry first and then wet, it is easy to crack the melon, so irrigation with small amount of water should be used to keep the humidity uniform.

Third, proper ventilation.

We must master the ventilation time during the expansion period of melon. Generally speaking, ventilation starts when the greenhouse temperature is higher than 28℃ and ends when the greenhouse temperature is lower than 26℃. According to the growth of watermelon in the shed and the external weather, it can be judged that the ventilation time should be appropriately extended to control the growth of watermelon when the growth is strong, and shortened to promote the growth when the growth is weak. When the outdoor temperature is high and the light is strong, the ventilation time can be appropriately extended to avoid the indoor temperature being too high; When the outside temperature is low or rainy, the ventilation time should be shortened, or the ventilation method should be adopted for many times in a short time to avoid the indoor humidity being too high and the temperature being too low.

Fourth, prevent diseases.

Fusarium wilt, Fusarium wilt and anthracnose are the main diseases that harm watermelon during melon expansion. Before the disease occurs, it can be controlled by spraying 500-fold solution of Wanjia+600-fold solution of propineb+750-fold solution of Yiwei on the leaves every 10 day. The stem blight and anthracnose can be controlled by diazepam 3000 times solution, Horrick 3000 times solution or difenoconazole 1500 times solution after the onset. Water plant roots and their vicinity with 200 times solution of 10% shuangxiaoling water agent or 200 times solution of 5% zhiweiling water agent or 70% disong wettable powder of 1000- 1500 times solution to prevent and control Fusarium wilt.