How to Grow Watermelons with Soilless Cultivation? Detailed Introduction to the Key Technical Points

Watermelon is one of the most popular fruits in summer, full of juice and sweet flesh, and it tastes even more refreshing when made into chilled watermelon juice. Watermelon has diuretic and heat-clearing effects, and eating watermelon is no longer limited to summer now; it can generally be enjoyed all year round. The common cultivation methods for watermelon are open-field planting and greenhouse planting, so can it be grown with soilless cultivation? What are the key technical points?

1. Methods used for soilless cultivation

The method commonly used for soilless cultivation of watermelon is the gravel hydroponic method, that is, growing in a cultivation pool, using gravel and stones as the growing substrate, and supplying nutrient solution at set times.

2. Substrate selection and disinfection measures

For soilless cultivation of watermelon, the commonly used substrates include tree bark, wood shavings, sugarcane bagasse, rice husks, and so on. They can be used alone or combined together. The specific choice should be adjusted according to the specific conditions of the growing area.

The substrate must be properly disinfected. If no fruit or vegetable of any variety has been grown in that area, the fresh substrate selected does not need to be disinfected.

In April and May, when sunshine is relatively long, the amount of ammonium nitrogen used can be appropriately increased, so that when watermelon lacks nitrogen or iron, it will fade to green or yellow. If nitrogen is lacking, the fruit generally becomes relatively small, turns yellow, and the whole plant develops abnormally. If iron is lacking, chlorosis appears between the leaf veins.

The methods commonly used for substrate disinfection are solar disinfection and steam disinfection.

For solar disinfection, in the hot summer, pile the substrate to a certain height, spray water on top of the substrate so that its moisture content exceeds 80 percent, then cover it with plastic film, place it in a greenhouse, seal it, and expose it to sunlight for half a month, which can achieve a relatively good disinfection effect. Generally, the sterilized substrate is filled into the cultivation bed one week before cultivation, at a thickness of about 10 cm.

Steam disinfection mainly achieves a sterilization effect. The substrate can be placed in a sterilization room for disinfection, and the specific length and width should be determined according to the terrain and quantity of planting. This type of disinfection method has a very good effect, but the cost is relatively high.

3. Key points for planting

At different growth stages of watermelon, the supply of nutrient solution needs to be adjusted accordingly based on its growth condition, season, and so on. For example, during the fruiting period, the phosphorus and potassium components should be appropriately increased.

Regardless of which soilless cultivation method is used, the nutrient solution is directly related to the growth of the watermelon root system and the absorption of mineral nutrients. In spring greenhouse soilless cultivation, low temperatures are prone to occur, and at this time the nutrient solution should be heated.

In soilless cultivation of watermelon, a lack of carbon dioxide will seriously affect the growth of watermelon, so carbon dioxide fertilizer should be applied. The commonly used methods include ventilation, compost fermentation, using dry ice or compressed carbon dioxide, and using gas generators to supplement carbon dioxide.