First, the chemical induction method. When cucumbers have 1 to 3 true leaves, the flower buds of leaves 2 to 21 begin to differentiate, but it's not yet clear whether they will become female or male flowers. This is the optimal time to apply ethephon. The typical concentration used is between 100-200 ppm. If the concentration is too low, there will be no noticeable effect, while a higher concentration may inhibit further flower bud development, leading to empty nodes. Spraying twice at 200 ppm yields good results, and spraying three times at 100 ppm can also be effective. Usually, 1 to 2 applications are sufficient. When applying, spray both the upper and lower surfaces of the leaves on a sunny day around 4 o'clock. After spraying, it’s important to water the plants thoroughly. Also, ensure adequate fertilization and proper irrigation. During the mid to late growth stages, it's recommended to spray 3-5 times with a 0.3% potassium dihydrogen phosphate solution mixed with an 802 dilution (3000-4000 times).
Second, light control through shading. Cucumbers are short-day plants, so reducing the length of daylight can increase the number of female flowers. Before the flowering stage, cover the beds with black shade nets that have a low shading rate, such as black SZW-10, during the summer months. This reduces the average daily temperature of the planting beds by 1.4°C and the temperature at 5 cm depth by 2.1°C, while also decreasing light intensity by about 66.2%. Limiting sunlight exposure to no more than 9 hours per day helps promote female flower formation. If shade nets are unavailable, materials like black paper or temporary shades can be placed on the trellis to achieve similar results.
Third, increasing moisture and nitrogen fertilizer. Cucumbers grown in soil with 80% humidity produce significantly more fruit compared to those in 40% humidity. It’s essential to maintain consistent watering throughout the growing period to keep the soil moist. During the early growth phase, ensuring an adequate supply of nitrogen fertilizer can also enhance the formation of female flowers. After applying ethephon, it's important to provide additional nutrients to support plant health and prevent any negative effects. Strengthen pest and disease management practices to ensure overall plant vigor and productivity.
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