May be short of phosphorus and boron. Spraying 0.3% potassium dihydrogen phosphate on the leaves at ordinary times and adding some borax at bud stage can improve the fruit setting rate.

First, fertilization. Young pineapples should be fertilized once a month or every other month, mainly with farmyard manure. Apply less or no chemical fertilizer to make fruit trees grow rough, grow fast and bear fruit early. 　　

Second, promote early flowering and fruiting. Grafted pineapple generally begins to bear fruit 5 years after planting. It takes 8 ~10 years for the seedlings to bear fruit. In order to promote early flowering and fruiting and inhibit vegetative growth, when the main stem of pineapple is 30 cm thick, several knives are lightly cut around the tree body to inhibit vegetative growth and make it bear fruit early and yield high. After picking fruit once a year, you will cut down trees once, so that you can bear early and have high yield. 　

Third, fertilization of hanging fruit trees. The pineapple with fruit is fertilized for the first time when it sprouts in early spring. Apply the second fertilizer when the buds are pulled out in large quantities. When the fruit expands rapidly, apply fertilizer for the third time. Farmhouse manure should be the main fertilizer for each fertilization, and nitrogen, phosphorus and potassium compound fertilizer should be applied appropriately. The amount of fertilization depends on the growth, age and tree potential of pineapple, and the fatness of the land.