Highbush Blueberry Cultivar Trial in Prince Edward Island, Canada

Abstract

A replicated trial of four cultivars was planted at the Harrington Research Farm, Prince Edward Island, Canada in 2002. Bushes were first harvested in 2004. After five harvest seasons, ‘Northland’ was the highest yielding cultivar, averaging 1752 kg/ha, and ‘Bluecrop’ had the largest berries, averaging 1.94 g per berry. Hand harvesting occurred from late July until early September. ‘Northland’, ‘Patriot’, and ‘Duke’ generally ripened first with ‘Bluecrop’ ripening 7–13 days later depending on the season. Overall, ‘Northland’ and ‘Bluecrop’ had the highest yield.

KEYWORDS:

• Vaccinium corymbosum
• yield
• fruit weight

INTRODUCTION

There is considerable interest in highbush blueberry (Vaccinium corymbosum L.) planting in Prince Edward Island (PEI). Blueberries perform best on acidic, well-drained soils with high organic-matter content and require a soil pH between 4.2 and 5.0 for optimum growth and production. Highbush blueberry bushes will start to produce a small crop after two years and will build up to full production in five to eight years (Anonymous, 2004). The recent interest in the viability of a commercial highbush blueberry industry prompted a look at cultivars suitable for production in PEI. PEI is located in plant hardiness zone 5b (Agriculture and Agri-Food Canada, 2000). Our report is on a trial to test the highbush blueberry cultivar productivity and identify those suitable for PEI.

MATERIALS AND METHODS

The experiment was established at the Agriculture and Agri-Food Canada (AAFC) Crops and Livestock Research Centre at Harrington (49°22’N, 63°14’W), PEI. The trial was initially planted in 2002, but was relocated in early spring 2003 to acquire a long-term research site. This new site was a long narrow field (east-west) with substantial hedgerow protection on the north and south. Soil at this site is classified as a Charlottetown soil, Orthic Humo-Ferric Podzol (Orthic Humo-Ferric Podzol System) with sandy loam to loamy sand textures. The climate in PEI is humid, with a cool boreal temperature regime and a relatively short rowing season that runs from May to October. Annual precipitation ranges from 800 to 1100 mm with approximately 50% being received during the growing season. The previous crop grown in this field was potatoes in 2002. Initial pH was 6.2.

The experimental design was a randomized complete block with four replicates of each cultivar. Planting stock was two-year-old plants obtained from a local nursery in the region. Each plot had six plants of each cultivar spaced 1.5 m apart with 3 m between the rows. Guard rows were established on both sides of the trial. At planting, Tiger S at 100 g per m² and peat moss at 0.1 m³ was mixed in the planting hole prior to planting. The four cultivars were ‘Patriot’, ‘Northland’, ‘Bluecrop’, and ‘Duke’. One month after planting, peat moss was reapplied at a rate of 0.04 m³ per plant and hoed in. Tiger S (0-0-0-90S) was applied in the spring with 75 g per plant in 2004 and 2007. The entire trial was fertilized with ammonium sulfate at 30 g per plant in late June of 2003, 2004, and 2005. From 2006 to 2008, ammonium sulfate was applied at bud break, petal fall, and early July at 48 to 86 g per plant. Application rate varied according to growth stage and age of plants (Anonymous, 2004). A permanent sod was established between the rows in 2003 and mown regularly. Weeds were controlled by handweeding, mowing, and occasionally spot sprayed with glyphosate or paraquat. In 2006, pyraclostrobin was applied to control Phomopsis stem canker. No insecticides were applied. All plants were pruned in the spring of each year to remove dead, damaged, or unwanted material. Plots were not irrigated.

From 2004, single-plant yields and 25-berry weights were collected at each harvest and used to calculate a total annual plant yield and mean berry weight. Data were analyzed annually and over years using the ANOVA directive of the statistical programming language of Genstat® (Release 11.0, Lawes Agricultural Trust, Rothamsted Experimental Station, 2008).

RESULTS

The annual and mean annual yields are given in Table 1. ‘Northland’ yielded the highest overall and in each year from 2006 to 2008. However, it consistently produced the smallest berries (Table 2). ‘Bluecrop’ had the largest fruit averaging 1.94 g per berry. After 7 years, plant survival ranged from 100% for ‘Duke’ to 71% for ‘Patriot’. ‘Northland’ and ‘Bluecrop’ had only 4% mortality. Hand harvesting occurred between late July and early September, with the majority of the fruit harvested in August. All cultivars had a similar harvest period in 2004 and 2005. For the remaining years, initial harvest varies from 7 to 13 days among cultivars with ‘Bluecrop’ consistently being the latest ripening (data not shown).

TABLE 1 Annual and Mean Annual Yield for Highbush Blueberry Cultivars Grown in PEI from 2002–2008

Cultivar	2004	2005	2006	2007	2008	Mean
	kg/ha
Northland	211	191	2297	2424	3639	1752
Bluecrop	84	72	1422	1884	2758	1244
Patriot	318	394	2443	565	1881	1120
Duke	172	301	2002	1079	1146	940
Grand Mean	196	239	2040	1488	2356	1264
SEM	45	71	277	345	425	196
Fprob	0.031	0.050	0.113	0.018	0.013	NS

TABLE 2 Annual and Overall Mean Berry Weight for Highbush Blueberry Cultivars Grown in PEI from 2002–2008

Cultivar	2004	2005	2006	2007	2008	Mean
	g/berry
Northland	1.27	1.24	1.26	1.06	1.16	1.20
Bluecrop	1.90	1.98	2.24	1.60	1.99	1.94
Patriot	2.18	2.12	1.96	1.38	1.82	1.89
Duke	2.02	1.94	1.82	1.57	1.80	1.83
Grand Mean	1.84	1.82	1.82	1.40	1.70	1.71
SEM	0.105	0.083	0.074	0.069	0.057	0.044
Fprob	<0.001	<0.001	<0.001	0.001	<0.001	<0.001

DISCUSSION

‘Northland’ outperformed the other cultivars evaluated. However, this plant produces a number of small shoots that will increase pruning costs and may be a deterrent for large-scale plantings. The berries are smaller and found more toward the center of the plant. This will increase the picking time for hand harvesting but should not impact mechanical harvest. Kaps and Odneal (1998) evaluated the performance of ‘Bluecrop’, ‘Bluejay’, ‘Blueray’, ‘Berkeley’, ‘Collins’, ‘Coville’, ‘Earliblue’, ‘Elliott’, ‘Lateblue’, ‘Northblue’, ‘Northland’, ‘Patriot’, ‘Pertic Blue’, and ‘Spartan’ on a site with an initially high soil pH (6.3). ‘Earliblue’ (early), ‘Berkeley’, ‘Bluecrop’, and ‘Northland’ (midseason), and ‘Coville and ‘Lateblue’ (late) were found to be best adapted. Dale and Hancock (2005) reported highbush blueberry yields ranging from 3.8 to 6.8 t/ha averaged over eight years of production. Yields in this trial are lower; however, this report represents only five years of data. Initial harvest dates varied from year to year, however ‘Bluecrop’ ripened on average ten days later than the other cultivars. Yields consistently increased for ‘Northland’ (p = 0.008) and ‘Bluecrop’ (p < 0.001), but ‘Patriot’ and ‘Duke’ appear to have reached maximum yield 4 to 5 years after initial harvest (Fig. 1). The mean yield for Northland over the 5 year period was significantly larger then ‘Bluecrop’, ‘Patriot’, and ‘Duke’ (p = 0.015).

FIGURE 1 Mean and response of yield across years for each cultivar.

CONCLUSIONS AND GROWER BENEFITS

Based on the result of this trial we have determined that highbush blueberries can be produced under our growing conditions. We recommend ‘Northland’ as a cultivar for a commercial-scale highbush blueberry planting in PEI. ‘Bluecrop’ produced well with large fruit and would also be a good choice especially for a “u-pick” enterprise with its large fruit size.

Notes

Anonymous. 2004. Fruit production recommendations 2004–2005. Publication 360. Ontario Ministry of Agriculture and Food. Guelph, Ontario, Canada.

Genstat® Committee 2008. Release 11.0, June 2008. Lawes Agricultural Trust. Rothamsted Experimental Station.