Self-pruning in lime (Citrus aurantifolia Swingle) after treatments with ichiphon, abscisic acid and nitrogen, phosphorus, and potassium fertilizers

Self-pruning can lower production costs, especially in the case of annual crops such as citrus. The study aimed to determine self-pruning of lime treated with growth regulators and a fertilizer. Self-pruning was applied on a one-year-old of Citrus aurantifolia from February 2020 to April 2022 in Bogor, Indonesia. The treatments used NPK at three levels: 22.5:7.5:2.5 g/tree, 32.5:17.5:12.5 g/tree, and 42.5:27.5:22.5 g/tree, and growth regulators: 500 ppm ichiphon + 100 µM ABA, 750 ppm ichiphon + 50 µM ABA, and 1000 ppm ichiphon. Initial symptoms of self-pruning, namely leaf fall, which correlated with the ethylene concentration in the leaves, occurred in all treatment applications. The combination of the NPK fertilizer 32.5:17.5:12.5 g/tree with 750 ppm ichiphon + 50 M ABA gave the highest ethylene concentration. The highest concentration of ABA was found on the first day after the treatment with the NPK fertilizer 42.5: 27:5: 22.5 g/tree and growth regulators 500 ppm ichiphon + 100 M ABA; however, it did not differ from the treatment with the NPK fertilizer 42.5: 27.5:22.5 g/tree and the 1000 ppm ichiphon growth regulator on the fourth and twelfth days. The percentage of secondary, tertiary, and deciduous branches did not differ between the treatments. Self-pruning that occurs as a result of induction by ichiphon, abscisic acid, and NPK fertilizers, can be an alternative to mechanical pruning.