This invention relates to the field of agricultural
fertilizer technology, and in particular to a slow-release
fertilizer formula suitable for the growth period of guava. By weight, the core layer comprises 30-40 parts
potassium sulfate, 5-8 parts
calcium nitrate, and 3-5 parts
magnesium sulfate; the middle layer comprises 15-20 parts
ammonium dihydrogen
phosphate, 1-2 parts
borax, and 0.5-1 parts
zinc sulfate; the outer layer comprises 20-25 parts
urea, 10-15 parts
potassium humate, and 3-5 parts
amino acid chelate
powder; and the
coating material comprises 2-4 parts bio-based
polyurethane and 0.5-2 parts modified paraffin. This invention employs a core layer, middle layer, and outer layer structure. The outer layer provides fast-acting nutrients that are rapidly released after fertilization, meeting the
nitrogen requirements of guava during its
budding and
shoot-growing stage. The middle layer releases nutrients in large quantities 45-60 days after fertilization, matching the
phosphorus,
boron, and
zinc requirements during the flowering and fruit-setting stage. The core layer provides long-acting, slow-release nutrients that are gradually released during the fruit enlargement stage, meeting the high
potassium,
calcium, and
magnesium requirements. This invention achieves a high degree of consistency between the
nutrient release curve and the physiological
nutrient requirement curves of guava during
shoot growth, flowering, and fruit enlargement.