Adaptation of two citrus cultivars grafted on forner alcaide Nº 517 to super high-density system and evaluation of mechanized harvesting

Abstract

Adaptation of two citrus cultivars, Valencia Delta Seedless (VDS) and Valencia Late Frost (VLF) grafted on Forner Alcaide no 517, to super high-density groves with mechanical harvesting was evaluated in southwest of Spain. Regarding to crop development, both cultivars showed a similar behavior regard to tree growth, good affinity with the rootstock and chlorophyll content in leaf (SPAD units). However, differences were obtained in phenological development and internal quality of the fruit. So, VDS showed a more advanced phenology, while VLF obtained a better-quality juice: higher titratable acidity content with a lower maturity index. On the other hand, it was identified a great potential of the mechanical harvesting in both cultivars, with significant fruit detachment percentages (about 90% or more) and above 8 kg of fruit retention force (FRF). However, VDS obtained a better response to the harvesting equipment evaluated (New Holland BRAUD 9090X DUAL, over-row continuous canopy shaking harvester). So, VDS recorded higher fruit detachment percentages (95-100%) as well as lower levels of physiological and physical damage. Finally, the differences between cultivars, both efficiency of the fruit detachment and tree damage could respond to differences in the structure of the tree and rigidity of the branches.