What are the fertilization characteristics for watermelon under plastic film mulching?

After plastic film mulching, watermelon generally yields about 30% more than in open fields, and the fertilizer application rate should be increased by 20% to 30% accordingly. For plots with a large yield increase, an appropriate additional amount of topdressing should be applied. The proportion of base fertilizer and the amount of nitrogen fertilizer in the base fertilizer should be appropriately reduced, while the number and proportion of topdressings should be increased accordingly. Topdressing can be applied 1 to 2 more times than for open-field watermelon. In addition to applying cake fertilizer and other organic fertilizers once during the early vine extension stage, compound fertilizer can also be applied 1 to 2 additional times, and potassium dihydrogen phosphate or urea can also be sprayed as foliar topdressing. It can also be applied with irrigation water; in the later stage of cultivation, the film can also be broken, and after hole application between plants, irrigation can be carried out.