Key Technical Points for Greenhouse Management of Muskmelon After Transplanting

1. Greenhouse temperature regulation

After transplanting, in the early stage, in order to raise the greenhouse temperature and promote seedling recovery, the greenhouse film should be fastened tightly, and the straw mats should be uncovered and covered in a timely manner; before flowering and fruit setting, the daytime greenhouse temperature should be maintained at 25-28°C, and at night at 16-18°C. When the greenhouse temperature exceeds 28°C, the greenhouse film should be opened for ventilation. As the plants grow and the outside air temperature rises, the ventilation openings should gradually go from small to large, and the ventilation volume from less to more; after fruit setting, the daytime greenhouse temperature should be 28-32°C, not exceeding 35°C, and at night around 15-18°C, maintaining a temperature difference of above 13°C. At the same time, sufficient light is required to facilitate sugar accumulation and improve fruit quality.

2. Pruning and trellising

In greenhouse cultivation of muskmelon, pruning should be carried out strictly, and vertical trellis cultivation should be adopted in all cases. Pruning can be done as single-vine pruning or double-vine pruning according to variety characteristics and cultivation needs. Taking the Zhuangyuan muskmelon as an example, double-vine pruning is the main method, and single-vine pruning is supplementary. When carrying out single-vine pruning with a secondary vine as the main vine, pinch out the growing point when the seedling grows to 4-5 true leaves, retain the robust secondary vine for growth, and remove all the other secondary vines. When carrying out double-vine pruning, after the lateral vines emerge, select and retain 2 secondary vines growing in parallel, so as to make the fruit uniform and attractive and improve the fruit's marketability. Weak seedlings can adopt the single-vine pruning method to facilitate coordinated plant growth and increase the fruit-setting rate. For trellising, nylon rope or hemp rope can be used to guide and hang the vines, and white nylon rope that is resistant to high temperatures is best for trellising. One end of the rope is fixed at the root crown of the plant, and the other end is tied with a slip knot to the horizontal wire pulled across the top of the greenhouse. As the stem vine extends, wind the vine onto the rope, and cut off the tendrils on the melon vine at intervals to reduce nutrient loss and promote faster plant growth.

3. Pollination, fruit retention, and fruit hanging

For pollination, artificial pollination or bee pollination can be used. Artificial pollination is carried out when the female flowers at the reserved nodes on the plant open, at 8:30-10:30 in the morning, using male flowers that open on the same day, removing the petals, and gently smearing the pollen from the stamens onto the stigma of the pistil. After fruit setting, leave 2 leaves and pinch out the growing point; a writing brush can also be used to collect pollen from the male flower and gently smear it onto the stigma of the female flower. After pollination, the pollination date should be marked to facilitate harvesting. For bee pollination, 1 box of bees should be placed in each greenhouse 2 days before flowering. Using bees for pollination can significantly increase the fruit-setting rate, reduce the occurrence of deformed fruit, and improve fruit quality and flavor. For fruit retention, when the young fruit grows to the size of an egg, the melons should be selected and retained. There are 2 fruit retention methods: single-layer fruit retention and double-layer fruit retention. For single-layer fruit retention, the fruit-bearing node is at the 9th-12th node of the main vine; for double-layer fruit retention, 1 layer of fruit is retained at the 9th-12th node and another at the 17th-21st node of the main vine. If the plant's vegetative growth is good, the fruit-setting node can be lowered; otherwise, it should be raised appropriately. Generally, small-fruit varieties can retain 2 melons per plant per layer, while large-fruit varieties retain only 1 melon per plant per layer. The principle for retaining fruit is to select those with proper fruit shape and conforming to the variety's characteristics, and to select fruit of the same size that grew quickly and were pollinated later; the fruit-bearing node should be moderate, and for double-layer fruit retention, the lower layer fruit should appropriately retain a higher node, while the upper layer fruit should appropriately retain a lower node. Practice has shown that under conditions of early sowing and relatively strong plant growth vigor, double-layer fruit retention can increase yield by 50%. For fruit hanging, when the young melon grows to 0.5 kg, it should be hung in a timely manner. Tie the rope with a slip knot to the fruit stalk near the fruit, and hang the melon to a position level with the fruit-bearing node.

4. Fertilizer and water management

Watering should follow the requirement of “cold tail and warm head”, and be carried out in the morning on sunny days, so that the ground temperature rises rapidly after watering. Generally, do not water on cloudy days or in the evening. After transplanting, water once 5-7 days later for seedling recovery, but because the melon seedlings have low water demand and ground evaporation is also low, the amount of watering should be controlled. Too much water will affect the increase in ground temperature and seedling growth. At the vine extension stage, apply 1 application of nitrogen fertilizer as appropriate, appropriately combined with phosphorus and potassium fertilizers, applying 10-15 kg of urea and 15 kg of diammonium phosphate per 667 sq m, and water immediately after fertilization. Within 1 week after flowering, water should be controlled to prevent excessive vegetative growth and affect fruit setting. The melon swelling stage is the period when the plant has the greatest demand for fertilizer and water. Apply 15 kg of potassium sulfate and 20 kg of diammonium phosphate per 667 sq m, applied with irrigation water. After 7-10 days, water again, depending on soil moisture conditions. When retaining fruit in double layers, a third fertilizer application can be made during the swelling stage of the upper layer fruit, applying 10-20 kg of potassium sulfate and 10-15 kg of diammonium phosphate per 667 sq m. In addition to applying quick-acting chemical fertilizers, decomposed chicken manure, soybean cake, and other materials can also be applied with irrigation water during the melon swelling stage, at 250 kg per 667 sq m. During the growth period, foliar fertilizers such as potassium dihydrogen phosphate and compound micronutrient fertilizers can be sprayed on the leaves 2-3 times to promote plant growth and development. About 10 days before maturity, watering should be strictly controlled; otherwise, it will affect the fruit's quality and flavor.