Blueberry Production Research at the NWREC – Highlights

Bernadine Strik (Project Leader), Emily Vollmer and Gil Buller (Research Assistants) and Denise Nemeth (Ph.D. graduate student) in the Berry Crops Research program at the NWREC are working on several blueberry projects that are briefly highlighted here. More information on these projects will be presented at meetings throughout the winter.

Organic Trial

The long-term goal of this project is to develop organic production systems that maximize plant growth, yield and fruit quality, facilitate weed, water and nutrient management and provide economic benefit to growers. This one-acre trial was in its fifth growing season in 2011. We don’t have results on treatment effects for this year yet, because of the very late fruiting season. Cumulative yield from years two-four (2008-10) was 48 percent greater on raised beds than flat ground, corresponding to improved plant growth. So far, yields for the best treatments have been similar to what is expected for well managed conventional fields. Plants fertilized with the high rate of feather meal or the low rate of fish emulsion had the greatest yield. Plants mulched with yard debris compost topped with sawdust or those grown with landscape fabric (weed mat) produced greater yield than those mulched with sawdust.

Long-term Impact of N Fertilization and Sawdust Use in Elliott

We are studying the long-term impact of pre-plant incorporation of sawdust and surface sawdust mulch and nitrogen fertilizer rate on yield, fruit size, fruit firmness, soil nutrient status and soil microbiology in Elliott. Nitrogen rates have been increased proportionately as the planting has aged with rates of 50, 150 and 240 lb. N/acre used in 2010 and 2011 (years seven and eight). Machine-harvested yield was 10 tons/acre in 2010. We have found no significant effect of N fertilization rate, sawdust incorporation before planting or sawdust mulch on yield in any year of the study! However, plants fertilized with the high rate of N have had smaller fruit size. Higher N rates have also reduced soil pH and soil Ca over time and use of sawdust is affecting soil organic matter and nutrient status. Denise Nemeth is working with Drs. Strik, Lambrinos and Yang to study the amount of carbon sequestration in this mature field and the impact of use of organic matter and N rate on mycorrhizal infestation.

Fruit Set and Berry Development in Blueberry Cultivars

We are working with Duke, Liberty, Bluecrop, Bluejay, Legacy, Draper, Reka, Aurora, Ozarkblue and Bluegold. Percentage of fruit buds on one-year-old laterals ranged from 38 percent (Ozarkblue) to 54 percent (Bluegold) and has varied from year to year. Flower number per bud has been relatively consistent within cultivars ranging from six to seven (e.g. Duke, Draper and Legacy) to more than eight (e.g. Aurora, Bluegold and Ozarkblue). Percent fruit set has been high (89 to 95 percent), but averaged about five percent lower in wet springs than dry ones. Fruit firmness has been greatest for Draper and lowest for Ozarkblue and Aurora, to date. Although there has been as much as a three-week difference between cultivars in date of full bloom, this has not been correlated with date of first harvest. The number of growing degree days required from bloom to full blue fruit ranged from 550 in Duke to 1,300-1,400 in Aurora. We are studying the relationship between seed number and berry weight in these cultivars.

The Impact of Hand Harvest Frequency on Yield and Fruit Quality

In 2010 we started a two-year study to compare bushes that are harvested at a low, medium and high frequency (number of days between hand harvests) for the impact on bush yield and fruit quality (berry size, firmness, brix and total acidity) in several commercial cultivars. In the bushes that are picked at a high frequency, fruit are picked when they first turn fully blue. In contrast, fruit harvested at a low frequency are left to hang on the bush longer. We have not analyzed our data for this year yet.

We thank our advisory board members and the organizations that have provided funding for these projects: The Oregon Blueberry Commission, the Northwest Center for Small Fruits Research, the Washington Blueberry Commission, the NIFA-OREI grant and industry contributors.


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Oregon Blueberry Commission • P.O. Box 3366 • Salem, Oregon 97302
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