A study of seasonal leaf nitrogen in southern highbush blueberry grown as an evergreen crop in Australia

The production of blueberry as an evergreen crop, using southern highbush cultivars, is increasing in warm temperate climates. In Australia, cultivars are selected that flower and fruit through winter and spring but their nutritional requirements in this system are little understood. In this study, we aimed to evaluate the suitability of summer as the annual sampling period for the monitoring of plant nitrogen (N) status, and to compare these values, and those for other nutrients, to the current standards based on North American data. We selected an early fruiting cultivar (Vaccinium corymbosum ‘11-11’) and sampled leaves approximately monthly from autumn through to summer from an experimental crop grown in substrate, and from four commercial crops, three in soil and another in substrate. A similar pattern of mature leaf N concentration occurred among the crops with a peak just prior to harvest and levels declining to a minimum towards early summer. Leaf sampling during summer appears to be appropriate as leaf N is stable but responsive to applied fertiliser. Further work is required to determine the N requirement for this evergreen crop and to understand the allocation of nutrients and biomass to organs at different phenological stages.