ASHS 2015 Annual Conference

Production of southern highbush blueberries (SHB) in Florida requires soil amendments that decrease pH and increase organic matter; however, soil amendments increase production costs and are not environmentally sustainable. Vaccinium arboreum is a wild species that has potential as a rootstock for SHB, because it grows in sandy soils and tolerates high soil pH and low organic matter. The hypothesis tested in this research is that SHB plants grafted onto V. arboreum rootstocks exhibit increased soil adaptability compared with own-rooted SHB plants when cultivated on non-amended soil. The specific objectives are to evaluate the effects of two soils (pine-bark amended versus non-amended) and root systems (own-rooted vs grafted plants) on growth, yield, and fruit quality in two SHB cultivars (Farthing’ and ‘Meadowlark). Four rootstock-scion combinations (own-rooted ‘Farthing’ or ‘Meadowlark’; ‘Farthing’ or ‘Meadowlark’ grafted onto V. arboreum) were field planted in 2011 on either amended or non-amended soil. In the first three years, own-rooted ‘Farthing’ on amended soil had greater canopy volume than own-rooted ‘Farthing’ on non-amended soil or grafted ‘Farthing’ on either soil. In the fourth year, own-rooted and grafted ‘Farthing’ had the same canopy volume, while ‘Farthing’ on amended soil had greater canopy volume then those on non-amended soil. For ‘Meadowlark’, own-rooted plants on amended soil had greater canopy volume than own-rooted plants on non-amended soil or grafted plants on either soil in the first two years. In the third year, own-rooted ‘Meadowlark’ on amended soil or grafted ‘Meadowlark’ on either soil had greater canopy volume than own-rooted ‘Meadowlark’ on non-amended soil. In the fourth year, canopy volume was greater in ‘Meadowlark’ on amended versus non-amended soil and on grafted versus own-rooted plants. In 2013, own-rooted plants of both cultivars grown on amended soil had higher yields than own-rooted plants on non-amended soil or grafted plants on either soil. In 2014, regardless of the root system, plants on amended soil yielded more than plants on non-amended soil for both cultivars. Across soil types, grafted plants yielded more than own-rooted for ‘Meadowlark’, however, yields were the same for ‘Farthing’. Fruit quality (sugar:acid ratio) was not consistently different across treatments and years for either cultivar. These results indicate that grafting delayed plant growth, and consequently reduced yield during the first two years after planting. Fruit quality was not affected by grafting or soil treatments.