Primocane Yield of 'Prime-Ark® 45' and 'Prime-Jan®' Blackberries Grown Using USDA National Organic Program Practices in Kentucky

Abstract

Primocane-fruiting blackberries have the potential to produce a niche-market crop for growers from late summer until autumn frost on primocanes, and again as floricanes the following season. 'Prime-Ark ^®45' was recently released by the University of Arkansas and this cultivar may be suitable for commercial production in Kentucky and surrounding areas; however, this selection has not been tested in a multi-year study in this climate and associated disease pressures of this region. The objective of this study was to determine if 'Prime-Ark ^®45' was superior to 'Prime-Jan ^®' in terms of yield and berry size in Kentucky growing conditions and when maintained using National Organic Program standards. In April 2010, a blackberry cultivar trial was established at Kentucky State University (KSU). Plants of the commercially available primocane-fruiting, thorny erect cultivars 'Prime-Jan ^®' and 'Prime-Ark ^®45' were planted on certified organic land and managed with organic practices following the National Organic Program standards at the KSU Research and Demonstration Farm, in Frankfort, KY. The planting was managed for primocane production only. 'Prime-Ark ^®45' out-yielded 'Prime-Jan ^®' by a three-to four-fold margin in all three years of the study. Berry weight ranged from 25% to 70% heavier for 'Prime-Ark ^®45' in each year of the study. In 2011 and 2012, high summer temperatures likely reduced drupelet set and subsequent fruit size and yield. In 2013, summer temperatures were mild and both cultivars had higher yield and larger fruit size compared to 2011 and 2012.