What are the main reasons for the lack of flesh of watermelon?

What are the main reasons for the lack of watermelon flesh? How to prevent it?

First, there is an insufficient supply of fertilizer and water during the expansion period of watermelon. The process of watermelon expansion is a process in which the tissue cells of watermelon peel and pulp continue to increase and increase, especially the pulp part of watermelon, except for seeds and connected vascular bundles, are all composed of parenchyma cells. If the supply of fertilizer and water is insufficient, the cells can not get enough water and nutrition, and the cell wall breaks, a cavity is formed.

Second, the temperature of watermelon in setting stage and fruit expansion period is too low or too high. The development of watermelon is mainly vertical growth in the early stage and horizontal growth in the later stage. The temperature in the early stage of watermelon development in arch shed is lower (less than 20 ℃), and the longitudinal growth of watermelon will be weakened or even stopped prematurely under low temperature or drought or lack of light. In the later stage of development, when the temperature in arch shed is higher (higher than 35 ℃) and the light is strong, the lateral development of watermelon will be very rapid. In this way, the internal growth of watermelon is uneven and it is easy to produce hollow melon.

Third, improper fertilization and excessive application of nitrogen fertilizer in watermelon setting stage and expansion stage. The proportion of N, P and K absorbed by watermelon during the whole growth period was about 3:1:4. During the spreading period and flowering stage before setting melon, the absorption of nitrogen and phosphorus is more, and after fruit setting, it is mainly the absorption of potassium. At this stage, if too much nitrogen fertilizer is applied, the plant will grow too long, the long vine will not grow melon, and the photosynthate of watermelon is not nutritious. It is easy to cause hollow.

Preventive measures: first of all, rational watering and fertilization should be taken to avoid drastic changes in soil moisture. Watering during the growth period of watermelon should be gradually increased from less to more. Secondly, it is necessary to control the amount of nitrogen fertilizer and increase the application of potassium fertilizer. When the young fruit eggs are big, apply expanded fruit fertilizer, and use 5-10 kg potassium sulfate or potassium dihydrogen phosphate per mu. Finally, it is necessary to regulate the temperature of watermelon setting stage and fruit expansion period. When the temperature was low in the early stage, the temperature was controlled at 22-25 ℃ in seedling stage and 25-28 ℃ in vine stage when the temperature was low. After entering the fruiting period, measures such as covering the sunshade net and throwing mud should be taken to reduce the temperature of the arch shed to 28-32 ℃.