Detailed Explanation of Key Techniques for Planting Grafted Watermelon Seedlings
AbstractThe grafted watermelon seedlings have relatively high growth and fruit-setting rates. The bed can be prepared into a large bed with a bed width of 2cm and a ditch width of 45cm. When the grafted scion grows 3-4 true leaves, it can be transplanted into the middle of the large bed at a plant spacing of 140cm, with about 200 plants planted per mu. During the growth process, an appropriate amount of urea, biogas slurry, and potassium sulfate compound fertilizer can be applied. Watering should follow the principles of not watering on cloudy days but watering on sunny days, not watering in the afternoon but watering in the morning, delaying watering when the vines are vigorous and the melons are small, and watering early when the melons are large and the vines are weak.
I. Grafting Steps and Methods
1. Grafting Tools
The grafting tools can be a blade and a bamboo skewer. The blade should be sharp and durable. For the insertion hole, a bamboo skewer can be used, with a length of 6-7 cm. One end is whittled into an elliptical slanted surface 0.5-0.7 cm long, similar to the slanted cut surface of the scion stem, and then lightly burned over fire to make the front end of the bamboo skewer hard and smooth.
2. Grafting Techniques
(1) Grafting can be carried out when the scion seeds grow cotyledons. The weather during grafting needs to be clear and fine, with a temperature of about 18-25 °C. Grafting should not be carried out in cloudy and rainy weather.
(2) The commonly used method is top insertion grafting. About 3-5 days before grafting, the rootstock seedlings can be properly pinched before the 2nd true leaf grows. The grafting work needs to be carried out in a plastic greenhouse. If the light is too strong, a straw mat can be covered over the plastic greenhouse to avoid direct sunlight.
(3) Then use a flat bamboo skewer with a thickness of 0.1cm, a width of 0.2cm, and a length of 12cm, insert it diagonally between the 2 cotyledons of the rootstock, then pull out the bamboo skewer, and insert the whittled scion into the rootstock.
3. Management of Grafted Seedlings
(1) It takes about 10 days for watermelon seedlings to survive from grafting. Under good conditions of humidity, temperature, shading, and pest and disease control, it is helpful to ensure the planting effect. Generally, the temperature inside the greenhouse needs to be stabilized at 20-35 °C, and the humidity inside the greenhouse needs to be stabilized above 85%. If the humidity is insufficient, a sprayer can be used to supplement it.
(2) Within 2 days after watermelon grafting, sealed shading measures need to be taken. Starting from the 3rd day, 30 minutes of light can be given every morning and evening, and the 2 ends of the plastic film can be opened for 1 ventilation. Later, the light time can be appropriately extended and the number of ventilations increased.
(3) After waiting for 1 day, when the grafted seedlings have basically survived, the covering can be removed for routine management. Later, seedling damping-off disease should be controlled in time.
II. Planting Techniques for Grafted Watermelon Seedlings
1. Large Beds and Sparse Planting
(1) The grafted watermelon seedlings have relatively high growth and fruit-setting rates. After the 2nd fruit setting, the single fruit weight can reach about 6 kg. During this period, the land preparation method of "deep ditch turtle-back type high bed" can be adopted, preparing the bed into a large bed with a bed width of 2cm and a ditch width of 45cm.
(2) When the grafted scion grows to 3-4 true leaves, it can be transplanted into the middle of the large bed at a plant spacing of about 140cm. Generally, the planting density per mu is about 200 plants. When more side branches appear in the later growth stage, vine training work should be carried out in time.
2. Water and Fertilizer Management
(1) In early May, choose a sunny day to water once, and apply 5-7 kg of urea per mu. During the flowering period, watering and fertilizing should not be done. When the watermelon grows to the size of an egg, watering and fertilizing can be carried out according to weather conditions, applying 20 kg of 17:17:17 potassium sulfate compound fertilizer per mu, or 500 kg of biogas slurry.
(2) After fruit setting, watering should be carried out according to the growth conditions of the watermelon and weather conditions, following the principles of not watering on cloudy days but watering on sunny days, not watering in the afternoon but watering in the morning, delaying watering when the vines are vigorous and the melons are small, and watering early when the melons are large and the vines are weak. During the watermelon expansion period, watering and fertilizing can be done heavily once. In the later stage, fertilizing should be carried out with each watering. One week before the watermelon matures, watering and fertilizing should be stopped.
(3) During the watermelon expansion period, the daytime temperature needs to be controlled at 25-35°C, and the nighttime temperature needs to be controlled at 15-20°C. In the later stage, the temperature difference can be appropriately widened. Foliar topdressing mainly applies 0.2% potassium dihydrogen phosphate, or 1:12-15 biogas slurry.
3. Pest and Disease Control
Common diseases during the watermelon growth period include anthracnose, powdery mildew, leaf blight, etc. Generally, a combination of biological control and agricultural control can be adopted. The common pest is aphids, which can be controlled with 25% imidacloprid wettable powder during this period.