The Impact of Organic Blueberry Production Systems on Performance of Cultivars and Yield Components

The objectives of this project are to 1) determine the effect of cultivar and year on: fruit bud set; flowers/ bud; percent fruit set; berry weight; berry firmness, and seed number per berry; 2) determine the effect production system (mulching & incorporation) and plant age on yield per plant for standard and newer cultivars; and 3) determine whether there is a relationship between seed number per berry (an indicator of pollination/fertilization success) and berry weight and cultivar effects on this relationship.

We are using plants that were established in October 2006 in the guard rows of the one-acre organic blueberry research planting at the NWREC. Treatments are as follows.


Duke; Liberty; Bluecrop; Bluejay; Legacy; Draper; Reka; Aurora; Ozarkblue; and Bluegold

Soil management 

  1. "Organic mulch": incorporation: ½"-1" of compost + 2" of fir sawdust incorporated before planting; Mulch: ½"-1" of compost topped with 3" of sawdust (replenished, as needed).
  2. "Weed mat": no pre-plant incorporation; Mulch: 3" of sawdust topped with weed mat. Weed mat was replaced Dec. 2010 with "zippered" system, but no replenishment of sawdust was necessary (still had ~ 2 to 3 inches).

Results to date

Cumulative yield (2008-2011) averaged 41% higher for plants grown on weed mat than those on sawdust mulch, ranging from 0% (no difference) to 96%, depending on cultivar. Mulch did not affect any other variable measured, except for plants with weed mat had softer fruit in 2009. Cultivar affected all variables, except percent fruit set, in all years. Yield increased from 2009-2011 in the cultivars Duke, Bluecrop, Legacy, Ozarkblue, and Aurora. Yield was similar from 2010 to 2011 in 'Reka', 'Draper', 'Bluegold', and 'Bluejay', but declined in 'Liberty'. 'Bluegold', 'Draper', and 'Liberty' were affected by Blueberry shock virus that reduced yield. In 2011, yield ranged from 1.5 ('Bluegold') to 6.5 kg per plant ('Legacy').

Percentage of fruit buds on one-year-old laterals ranged from 24 ('Bluecrop') to 55% ('Bluegold'). Some cultivars had variable fruit bud set over the three years (e.g. 'Liberty', 'Legacy', and 'Aurora'), whereas others were relatively consistent among years (e.g. 'Duke', 'Bluegold', and 'Ozarkblue'). For each cultivar, the number of flowers per cluster was similar for 2009 and 2010, but was higher in 2011, except in 'Aurora' and 'Bluejay'. Cultivars with the fewest number of flowers per bud (6-8) included Duke, Draper, Bluegold, and Legacy, whereas the highest number of flowers per cluster (8-11) occurred in Reka, Bluecrop, Aurora, Liberty, and Ozarkblue.

Fruit set was high (83 to 100%) and depended on cultivar and year. Average berry weight ranged from 1.3 ('Liberty') to 2.7 g ('Aurora' and 'Draper'), percent soluble solids from 13 ('Bluegold', 'Ozarkblue, and Aurora') to 16% ('Liberty' and 'Bluejay'), and firmness from 144 ('Aurora') to 230 g per mm deflection ('Draper') and varied by year.


Bernadine C. Strik, Professor, Dept. Horticulture & Berry Crops Research Leader, NWREC
Chad E. Finn, USDA-ARS, HCRU, Corvallis


We thank the following individuals for their significant contributions to this project: Emily Vollmer (Research Assist., Dept. Hort., OSU); Gil Buller (Senior Research Assist., NWREC

We greatly appreciate the financial, research grant support and in-kind contributions from: Oregon Blueberry Commission; Eric Pond (AgriCare), Fall Creek Farm & Nursery, Wilbur Ellis, Marrone BioInnovations (GreenMatch), and Oregon Tilth