Grafted blueberries: An option for mechanical harvest?

Profitability of the fresh market blueberry industry in the southeastern U.S. is limited due to high production costs, which include extensive soil inputs to increase organic matter and decrease pH, as well as costs for hand-harvesting. Mechanical harvesting systems decrease production costs; however, fruit losses occur due to the multi-caned architecture of the plants. Sparkleberry (V. arboreum) is a wild species adapted to higher pH, low organic matter soils, and exhibits a single-trunk growth habit. These characteristics raise the possibility that this species may be useful as a rootstock for commercial blueberry production, increasing soil adaptation and efficiency of mechanical harvest. The objectives of this research are to evaluate yield, pack out efficiency, and berry quality of two southern highbush blueberry cultivars, grown on pine-bark amended or non-amended soils, and either hand- or mechanically-harvested. Four “genotypes” (own-rooted or grafted onto V. arboreum ‘Farthing’, and own-rooted or grafted onto V. arboreum ‘Meadowlark’) were grown in non-amended and pine-bark amended soils. Data were collected during the 2012/2013 season. For both cultivars, own-rooted/hand-harvested plants grown in pine-bark amended soil had the greatest marketable yield compared with all other treatments. The yield reduction of mechanically compared with hand-harvested fruit was due to harvesting of unripe and damaged berries, and ground losses. Grafted plants reduced ground loss during harvest by ~45% compared with own-rooted plants. For both cultivars, hand-harvested berries or berries from own-rooted plants had superior firmness compared with mechanically-harvested berries or berries from grafted plants. In general, mechanically-harvested berries of both cultivars had a greater SSC/TTA ratio than hand-harvested berries. Even though mechanical harvesting reduced marketable yield compared with hand harvesting, the reduced costs associated with mechanical harvesting, combined with the reduction in ground losses in mechanically-harvested grafted compared with own-rooted plants, indicate that additional research into the use of grafted blueberry as a new mechanically-harvested production system is warranted.