Cultivation techniques of out-of-season watermelon

I. planting density

Watermelons grown in solar greenhouses are generally yellow gift watermelons and seedless watermelons. The planting value density should be determined according to the maturity of the variety, the number of vines per plant and soil fertility. Early-maturing varieties 1500-1800 plants per mu (double vines pruning), middle-maturing varieties 1500 plants, late-maturing varieties 1200 plants.

Second, temperature management

The temperature should be regulated according to the different growth and development stages of watermelon. The daytime temperature is generally controlled at 30 ℃-36 ℃, the night temperature should not be lower than 15 ℃, and the night temperature should not be lower than 18 ℃ during fruit setting and fruit development. The ground temperature should be kept above 18 ℃.

III. Water and fertilizer management

The suitable soil moisture for watermelon is 65% of the maximum field capacity, and drought will occur when the soil moisture is less than 48%. The requirement of soil moisture for watermelon is high in germination stage, less in seedling stage and appropriate in vine stage. As a result, water demand is at its peak in the middle stage, full irrigation is needed, and irrigation should be reduced in the later stage.

The fertilization of watermelon should be based on the application of sufficient base fertilizer and topdressing, applying 30kg potassium sulfate and 30kg diammonium per mu during the fruit expansion period. Before and after the melon is fixed, the mixture of 0.2% urea and 0.2% potassium dihydrogen phosphate can be sprayed on the leaves if possible. To observe whether the watermelon lacks fertilizer, it depends on the color of the leaves, if the basal leaves are dark green, the middle leaves are green, and the top leaves are light green, indicating normal growth; if the whole plant is yellowish green from top to bottom, it indicates lack of fertilizer; if the leaf color of the plant is dark green from top to bottom, it indicates that excessive nitrogen fertilizer will occur, and attention should be paid to control.

4. Pruning

Watermelons in solar greenhouse are pruned by double vines, the main vines are used as fruit vines to climb the ground, and the auxiliary vines are used as nutritive vines to grow upward. Pruning begins when the vine is 50-60 cm long, and the lateral branches before the node position should be removed in time, and more vines or non-pruning can be left for weak varieties.

Fruit setting and pollination

The position of remaining melon has a direct effect on the size and yield of fruit. The second and third female flowers should be left on the main vine. When the fruit grows to the size of an egg, the fruit can be selected. Choose and retain the young melons with enlarged ovary, normal shape, fresh and shiny color. The rest are eliminated. Due to the less activity of insects in the solar greenhouse, artificial pollination is needed to ensure fruit setting. After 9 o'clock every morning, female flowers open and male flowers disperse pollination. In order to make the yellow-skinned watermelon receive light evenly and the peel yellow is consistent, the melon should be turned about 20 days after flowering to make the bottom peel bright and beautiful. Turning melons should be carried out when the sun is to the west.