Influence of deficit irrigation in phase III of fruit growth on fruit quality in ‘lane late’ sweet orange

The aim of this work was to apply one strategy of deficit irrigation (DI) to improve the final fruit quality in 10-year-old ‘Lane late’ sweet orange grafted on Carrizo citrange (Citrus sinensis L. Osb. × Poncirus trifoliata L.). The experiment was carried out over 2 years in an experimental orchard located in Torre Pacheco (Murcia, south-east Spain). The deficit irrigation treatment consisted of the stopping of irrigation in phase III of fruit growth (1st October-28th February). The irrigation cut-off in phase III reduced the midday stem water potential (Ψ_md), the plant water status being heavily influenced by rainfall. In both years, the DI treatment did not alter fruit yield although mean fruit weight was slightly reduced. The main effects of DI on the final fruit quality were increases of total soluble solids (TSS) and titratable acidity (TA) and a decrease of juice percentage without altering the final maturity index. Plant water-stress integral (S_Ψ) was correlated positively with TSS and TA and negatively with juice percentage. In conclusion, a DI strategy could be useful for improving the final content of TSS and the TA, therefore allowing the harvest to be delayed.