Watermelon is the main fruit vegetable in China, with large planting area and high yield. In recent years, the quality of watermelons has obviously declined, and it is a problem that the majority of consumers and producers are increasingly concerned about. Reasonable fertilization has a great impact on the quality and yield of watermelons. The following five issues should be of concern:

First, determine the reasonable ratio of nutrient input and key periods of fertilization

Watermelon absorbed potassium most during the whole growth period, followed by nitrogen and phosphorus. For every 1,000 kg of watermelon produced in the middle level, nitrogen (N) 2.5-3.3 kg, phosphorus (P2O5) 0.8-1.3 kg, potassium (K2O) 2.9-3.7 kg, N:P2O5 should be absorbed: K2O is 1:0.36:1.44. The proportions of nitrogen, phosphorus and potassium applied in the soil with high soil available phosphorus content can be 1:0.5:1, and in the soil with low soil available phosphorus content can be 1:1:1; in the low potassium area, Properly increase the proportion of potassium application, such as 1:0.5:1.2.

The whole growth period of watermelon is 80-120 days, which can be divided into germination period, seedling period, pumping period and flowering period. From the end of flowering to the swell period of the swell period, it is the peak period of absorption of nutrients. Therefore, on the basis of sufficient base fertilizer, the seedlings should be steadily followed by vine manure, and the swelled manure should be replenished, and the foliar fertilizer must be recovered.

Second, we must promptly adjust and meet the different growth and development of nitrogen, phosphorus, potassium balance requirements

The proportion of nitrogen, phosphorus and potassium absorbed during different growth and development periods varies greatly. Before pumping vines, 1:0.21:0.83 absorbed the most nitrogen and phosphorus was the least. In the six or seven days of fruit hair removal, it was 1:0.8:0.87, and the ratio of phosphorus absorption increased significantly. The fruit enlargement period was 1:0.3:1:13, the ratio of phosphorus absorption decreased, and the proportion of potassium absorption increased. The maturation period is 1:0.26:1.22. Nitrogen, potassium, and phosphorus were less required during the entire growth period, and nitrogen and potassium were more in the middle and later stages. Therefore, ensuring the supply of nitrogen nutrients in the early stage of watermelon growth, together with appropriate phosphorus and potassium, promote the vegetative growth of plants, and ensuring the nutrient of nitrogen and potassium after sitting on melon is very important to improve the yield and quality of watermelon.

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