Rootstock-specific responses of ‘Rojo Brillante’ persimmon grafted onto Diospyros lotus and Diospyros virginiana to irrigation dose and planting layout, with implications for water status, fruit abscission and irrigation water productivity

The ‘Rojo Brillante’ persimmon (Diospyros kaki) is gaining relevance as an alternative to citrus in Mediterranean semiarid regions. This study evaluated the effects of irrigation dose (100% and 115% of a baseline irrigation dose, BID), planting layout (2.5 × 5 m and 3.5 × 5 m), and rootstock (Diospyros lotus and Diospyros virginiana) on midday stem water potential (ΨS, a plant-based indicator of tree water status), yield, vegetative growth, irrigation water productivity (IWP), and fruit abscission during the juvenile to mature transition (4 to 7-year-old trees) in southeast Spain. Across 2012–2014, ΨS in 100% and 115% treatments generally remained above − 1.30 MPa, whereas dense spacing under 100% BID caused transient severe summer stress (ΨS < -1.30 MPa) in trees, coinciding with reduced productivity in D. lotus. Yield was largely unaffected by increasing irrigation dose, and D. virginiana induced greater vigour than D. lotus without a consistent yield advantage, partly associated with lower crop load and greater physiological fruit drop. At the hectare scale, the denser layout tended to improve productivity. To optimise irrigation for D. virginiana, a 2015 study compared two irrigation strategies, 110% BID and sustained deficit irrigation at 70% BID, against a D. lotus control receiving 100% BID, all under the standard 3.5 × 5 m planting layout. SDI reduced abscission relative to flowering by about 14%, maintained yield, and maximised IWP. Fruit quality was not assessed. Overall, the results support rootstock-specific irrigation scheduling and identify deficit-based strategies as promising for improving water productivity without compromising yield.