How to fertilize an apple orchard after it enters the full fruit-bearing period
1. Base fertilizer
The best time to apply base fertilizer is from mid-September to mid-October, and organic fertilizer should be the main type. For trees in the full fruit-bearing period, calculated at a yield of 2000-3000 kg per mu, the amount of organic fertilizer applied per mu should reach 3000-4000 kg. At the same time, an appropriate amount of quick-acting chemical fertilizer should be applied, with 6-10 kg of pure nitrogen, 6-14 kg of P2O5, and 2-4 kg of k20 per mu.
2. Topdressing
(1) Fertilization before bud break (mid-to-late March). Apply 8-15 kg of pure nitrogen, 2-5 kg of P2O5, and 8-15 kg of k20 per mu. Function: to provide nutrients for bud break, flowering, young fruit development, and new shoot growth. (2) Fruit-setting fertilizer (apply in late May for early-maturing varieties, and in early-to-mid June for late-maturing varieties). Apply 6-10 kg of pure nitrogen, 2-5 kg of P2O5, and 8-15 kg of k20 per mu. Function: to enhance leaf function, promote flower bud differentiation, increase fruit size, and improve fruit quality. (3) Second fruit swelling fertilizer for late-maturing varieties (apply in early-to-mid August). Apply 3-4 kg of k20 per mu, a small amount of phosphate fertilizer, and generally no nitrogen fertilizer (it may be appropriately topdressed if the tree vigor is weak).
3. Foliar spraying fertilizer
(1) Before bud break. Spray 1%-5% urea 2-3 times. (2) After bud break until before mid-July. Spray once every 7 days, applying in a ratio of 2 times urea to 1 time potassium dihydrogen phosphate, at a concentration of 0.3%-0.5%; after mid-July until leaf fall. Spray in a ratio of 2 times potassium dihydrogen phosphate to 1 time urea, at a concentration of 0.3%-0.5%. (3) Before flowering. Spray 2-3 times borax at a concentration of 0.3%-0.5%. (4) Before fruit bagging. Spray 0.2%-0.4% calcium nitrate 3 times. (5) Deficiency symptoms. Carry out corresponding control measures: for iron deficiency, spray 0.3%-0.5% iron fulvate; for zinc deficiency, spray 0.3%-0.5% zinc sulfate; for calcium deficiency, spray 0.3%-0.5% amino acid calcium.