Improved rooting of softwood cuttings of dwarfing rootstock for persimmon under fog irrigation

Softwood cuttings of FDR-1, a dwarfing rootstock for persimmon (Diospyros kaki Thunb.), show very low rooting percentages when planted under mist irrigation. We therefore examined the possible use of a fog system in commercial softwood cutting propagation of FDR-1. Leaf-bud cuttings collected from FDR-1 hedges rooted better under the fog system, which maintained a relative humidity of approximately 100% compared to the mist system, in which humidity often dropped to less than 50% at midday. The amount of water used was lower in the fog system than in the mist system (0.18 vs. 0.89 L/h m2), thereby affecting leaf SPAD readings. Cuttings planted in early June rooted better than those planted in early July and August, and quick-dip treatment with 6000 mg L−1 IBA improved rooting compared with 3000 mg L−1 IBA. Cuttings collected from FDR-1 root-suckers rooted better than those from hedges, and almost all rooted cuttings, planted in June, sprouted in April of the following year. Under the fog system a practical rooting percentage of 80% was obtained when cuttings were collected from root-suckers, planted in early June, and quick-dipped in 6000 mg L−1 IBA, making it a practicable irrigation system for propagation of FDR-1 leaf-bud cuttings.