Amanda J. Vance

Northern Highbush Blueberry Cultivars Differed in Yield and Fruit Quality in Two Organic Production Systems from Planting to Maturity

Northern highbush blueberry (Vaccinium corymbosum L.) cultivars were evaluated from planting (Oct. 2006) through 2014 in a certified organic research site in Aurora, OR. The treatments included cultivar (Duke, Bluecrop, Reka, Bluejay, Bluegold, Draper, Legacy, Liberty,Ozarkblue, andAurora), amendment-mulch [‘‘compost+ sawdust’’ (includedpreplant amendment and a surfacemulch of either an agricultural on-farm cropwaste compost or yarddebris compost and sawdust), and ‘‘weed mat’’ (no preplant amendments but with a sawdust mulch toppedwith weedmat)]. Adding on-farm compost as a preplant amendment and as part of the mulching program increased soil pH from 4.9 to 6.9, organic matter content (OM), and calcium (Ca), magnesium (Mg), and potassium (K) levels compared with the weed mat treatment. The reduced plant growth and yield in some cultivars grown in the compost + sawdust treatmentwas likely due to the higher soil pH. ‘Bluegold’ and ‘Draper’were among the cultivars with consistently high flower bud set (40% to 57%), whereas others had consistently lowvalues (e.g., 22%to45%in ‘Bluecrop’). Thenumber of flowersperbudwas affectedonly by cultivar. There was no effect of year or amendment-mulch treatment on percent fruit set which averaged 93%during the study; however, ‘Ozarkblue’ had a significantly lower fruit set (88%) than only ‘Aurora’ (96%). Berry weight was affected by year (plant age), cultivar, and amendment-mulch treatment. ‘Ozarkblue’ produced the largest berries. Type of amendmentmulch had little effect on berry weight, except in ‘Ozarkblue’, ‘Aurora’, and ‘Reka’ where plants grown with weed mat produced larger fruit than those grown with compost + sawdust. On average, ‘Bluejay’, ‘Draper’, and ‘Liberty’ fruit had the highest percent soluble solids (TSS) and ‘Ozarkblue’ the lowest. Fruit harvested fromplants grownwithweedmatwere firmer than when compost + sawdust was used. ‘Draper’ fruit were much firmer than those of the other cultivars in all years of the study.Thenumberof flowerbudsperplantmultipliedby thenumber of flowers/bud and berry weight (cultivar specific) and average fruit set was a good predictor of yield in young plants. Yield per plant increased from the second through seventh growing seasons as plantsmatured in all cultivars except for ‘Duke’ which had the greatest yield in 2014. Cumulative yield was highest in ‘Legacy’ and lowest in ‘Bluejay’ and in ‘Draper’, which had relatively low yield when plants were young.Most cultivars had greater yield when grownwith weed mat, whereas ‘Bluegold’ and ‘Liberty’ were unaffected by amendment-mulch treatment. Because weeds weremanaged in all plots, the cultivar response to amendment-mulchwas likely a reflection of sensitivity to preplant amendmentwith on-farmcompost and the resulting higher soil pH. It is possible that the cultivars differed in their adaptability to the various fertility regimes caused by the amendment-mulch treatments and fertilizers used in our study. The Pacific northwestern United States is an important region for production of cultivated blueberry (Vaccinium spp.) (U.S. Department of Agriculture, 2014). The proportion of total U.S. blueberry production grown on certified organic and exempt organic (less than

Foliar Calcium Applications Do Not Improve Quality or Shelf Life of Strawberry, Raspberry, Blackberry, or Blueberry Fruit

5000/year gross income and not requiring certification) farms was relatively small (3%) in 2008 (U.S. Department of Agriculture, 2010). However, the Pacific northwestern region accounted for 49% of the total blueberry organic area planted in the United States in 2008, when the last survey was conducted. The certified organic area has grown considerably since the last survey, increasing to an estimated 915 ha in Oregon and Washington in 2011, 55% of total U.S. organic blueberry area (Strik, 2014). By 2014, the organic blueberry area in Oregon and Washington accounted for about 20% of total blueberry area planted. Growth in organic production continues as consumer demand for organic products remains strong, and this region offers substantial advantages for organic production (DeVetter et al., 2015; Strik, 2016; Strik et al., 2016; Strik and Yarborough, 2005). Awide range of cultivars are grown in this region for the fresh and processed markets, offering a range in fruiting seasons from the earliest (‘Duke’) to the latest (‘Aurora’) (Strik et al., 2014). The development of yield and fruit quality of the range of cultivars grown has not been compared in research studies, likely because of the relatively long time from planting to maturity (about 8 years). Differences in the performance of cultivars have been found in organic production of ‘Duke’ and ‘Liberty’ blueberry (Larco et al., 2013a, 2013b; Strik, 2016; Strik et al., 2016) and various blackberry cultivars (Fernandez-Salvador et al., 2015). Blueberry plants are adapted to soils with low pH (4.5–5.5) and high OM (>4%) (Hart et al., 2006). Organic and conventional growers are interested in using composts because of hypothesized OM, nutrient, and microbiological benefits (e.g., Forge et al., 2003) on soil properties and nutrients. Because organic sources of nitrogen (N) are expensive and often laborious to apply, the potential benefit from a slow-release N from compost is also of great interest to growers. However, use of plantand animal-based composts as a preplant amendment may be problematic in this crop as these materials have a high pH and often a high salt content (animal-based) (Sullivan et al., 2014). Our objective was to characterize yield and associated plant and fruit quality traits of important highbush blueberry cultivars in the region from planting to maturity and evaluate their adaptation to common organic amendments and mulches used in certified organic production. Materials and Methods Study site. The study was established in Oct. 2006 at Oregon State University’s North Willamette Research and Extension Center, Aurora, OR (NWREC; lat. 45 28# N, long. 122 76# W). Weather data for this site are available from an AgriMet weather station (U.S. Deptartment Interior, 2014). The planting was certified as meeting the USDA organic criteria before the first fruit harvest year (2008) by a USDA-accredited agency (Oregon Tilth, Corvallis, OR). The soil at the site is aWillamette silt loam (fine-silty mixed superactive mesic Pachic Ultic Argixeroll) and had a pH of 4.9 and 3.7% OM. Details on Received for publication 27 Mar. 2017. Accepted for publication 28 Apr. 2017. The authors appreciate the valuable assistance of Gil Buller, former Senior Faculty Research Assistant and Emily Vollmer, former Faculty Research Assistant at the North Willamette Research and Extension Center, OSU. We appreciate the funding support provided by the Oregon Blueberry Commission. Professor. Faculty Research Assistant. Research Geneticist. Corresponding author. E-mail: bernadine.strik@ oregonstate.edu. 844 HORTSCIENCE VOL. 52(6) JUNE 2017 preplant site preparation can be found in Larco et al. (2013a). After adding any preplant amendments, if used (see below), raised beds were constructed using a bed shaper; beds were 0.3-m high and 0.4-m wide at the top and 1.5-m wide at the base when established, but settled to a height of 0.25 m by Autumn 2007. Plants were irrigated using a single line of polyethylene drip tubing (Netafim, Fresno, CA) with 2 L·h pressure-compensating, inline emitters spaced every 0.3 m. The line was located along the row near the base of plants, under the mulch. Irrigation was controlled by electric solenoid valves and an automatic timer set weekly and scheduled to maintain a soil water content suitable for highbush blueberry production [25% to 30% soil water content from the soil surface to 0.3 m, based on time domain reflectometry measurements (SoilMoisture Equip. Corp., Santa Barbara, CA)] (L. Valenzuela-Estrada, unpublished data). Amendment and mulch. Two preplant amendment-mulch treatments were evaluated. The ‘‘compost + sawdust’’ treatment included a preplant amendment and a mulch of compost and sawdust. Commercially available agricultural crop waste compost (Wilt Farms, Corvallis, OR) made on farm ( 2-cm deep centered on the row; 76 m·ha) and fresh douglas fir sawdust (Pseudotsuga menziesiiM.; 5-cm deep; 200m·ha) were incorporated before forming the raised beds in Sept.–Oct. 2006. The on-farm compost consisted of well-composted rye grass clippings and other agricultural crop waste products and had lime (107 kg·t dry weight) added during the composting process based on the carbonate content of the raw material (note Ca content in Table 1). Immediately after planting, the beds were mulched with additional on-farm compost ( 2-cm deep; 76m·ha), and then, the compost was topped with sawdust ( 7.5-cm deep; 300 m·ha) with a goal of creating a barrier to weed establishment. The mulches were spread mechanically in 0.75 m wide strips under and on each side of the plant rows. Onfarm compost was used when the mulch needed replenishing in Autumn 2007, but in Jan.–Feb. 2011 and 2013, compost made with municipal yard waste clippings was used (Rexius, Eugene, OR). The composts and sawdust were analyzed by Soil Control Laboratory (Watsonville, CA) and total nutrient application was calculated (Table 1). The second amendment-mulch treatment, ‘‘weed mat,’’ involved no preplant amendments, but included a mulch of fresh douglas fir sawdust ( 7.5-cm deep; 300 m·ha) topped with black, woven polyethylene groundcover (water flow rate of 6.8 L·h·m and a density of 0.11 kg·m as measured by the manufacturer; TenCate Protective Fabrics, OBCNorthwest, Canby, OR).Weed mat was placed over a sawdust mulch layer, not currently a commercial practice, with a goal of offsetting the reduction in soil OM observed under weed mat mulch in long-lived perennial crops such as apple (Malus ·domestica Borkh.) (Choi et al., 2011). The weed mat was 1.5-m wide and was centered over the planting beds before securing it in place with landscape staples. A 20-cm diameter hole was cut in the weed mat for each plant and the are

Seasonal Variation in Mineral Nutrient Concentration of Primocane and Floricane Leaves in Trailing, Erect, and Semierect Blackberry Cultivars

Foliar calcium (Ca) products are applied by many berry growers to enhance fruit quality and shelf life without evidence that these applications increase fruit Ca or impact fruit characteristics when applied at rates recommended on the product label. The objectives of this study were to determine if fruit or leaf Ca increases when several formulations of liquid Ca products are applied to developing fruit, and to assess any resulting changes in freshmarket quality of berries. Products were applied in strawberry (Fragaria 3ananassa L., ‘Hood’ and ‘Albion’), raspberry (Rubus idaeus L., ‘Tulameen’ and ‘Vintage’), blackberry (Rubus L. subgenus Rubus, Watson, ‘Obsidian’ and ‘Triple Crown’), and blueberry (Vaccinium corymbosum L., ‘Spartan’, ‘Liberty’, ‘Draper’, and ‘Legacy’). Calcium formulations tested were Ca chloride (CaCl2), CaCl2 + boron, Ca silicate, Ca chelate, and Ca acetate, which were compared with a water-only control. The rates used for each product were within ranges specified on the label and supplied equal amounts of Ca per ha for each treatment; the Ca concentration varied from 0.05% to 0.3% depending on the cultivar and the volume of water required for good coverage. All products were applied with a backpack sprayer, except in a separate trial where a backpack and electrostatic sprayer were compared in ‘Draper’ and ‘Legacy’. Treatment applications were started at the early green fruit stage and were repeated three or four times, depending on duration of berry development and cultivar. Fruit were harvested into commercial clamshells 4 days to’4 weeks after the final application of Ca from an early harvest at commercial ripeness. Data collected included berry weight, rating of fruit appearance and flavor, firmness, skin toughness, total soluble solids (TSS), and weight loss and nesting (collapse of fruit) during storage (evaluated at ’5-, 10-, 15-, and 20-days postharvest). Fruit and leaves were sampled at harvest to determine Ca concentration. There was no evidence of spotting or off-flavors due to Ca applications. Compared with the control, none of the Ca treatments or method of application changed leaf or fruit Ca concentration, fruit quality, firmness, or shelf life in any crop or cultivar tested. The Pacific Northwest region of the United States is an important growing region for the production of blueberry (V. corymbosum L.), blackberry (Rubus L. subgenus Rubus, Watson), raspberry (R. idaeus L.), and strawberry (Fragaria ·ananassa L.) (USDA National Agricultural Statistics Service, 2015). Production of high-value fruit for the fresh market is increasing in many of these crops. Growers need to produce high-quality fruit that has the maximum possible storage or shelf life to be competitive in the market place. Calcium is often applied to fruit crops before harvest at the recommendation of some crop consultants in an effort to increase postharvest fruit quality. Fruit Ca has been found to be related to fruit firmness by strengthening the cell wall, which, in turn, improves shelf life (Van-Buren, 1979). Blueberry (Strik and Vance, 2015) and blackberry (Harkins et al., 2014) cultivars have been found to differ in fruit Ca concentration. When soil Ca levels are sufficient, localized Ca deficiency such as in leaves or fruit may still become a problem in fruit crops. Calcium-related disorders include bitter pit in apple fruit (Malus domestica, Borkh.), blossom-end rot in tomato (Solanum lycopersicum L.) fruit, and tipburn in leaves of vegetables (Saure, 2005). These deficiencies in Ca may occur as a result of competition between vigorously growing shoots and fruit. Strik and Vance (2015) speculated that ‘Draper’ blueberry may have particularly low fruit Ca concentration due to the presence of many competing shoot tips during the fruit development period. Since Ca is translocated in the xylem and not the phloem, Ca is relatively immobile in the plant and tends to move predominantly to leaves, which have a high transpiration rate. Penetration of Ca into fruit likely occurs through the stomata on the fruit surface. Penetration rates, however, have been shown to vary with cultivar, application method, and formulation of Ca used (Saure, 2005). The number of possible interactions that can affect Ca uptake and distribution in the plant is so complex that cultural management practices are not likely to increase fruit Ca, without a direct application of Ca to the developing (Bangerth, 1979) or harvested (Hanson et al., 1993) fruit. Postharvest dips with CaCl2 increased firmness and shelf life of raspberries and blueberries, but resulted in an unacceptable salty taste (Hanson et al., 1993; Montealegre and Valdes, 1993); washing or dipping fruit also removes the desirable, waxy bloom coating on blueberry fruit and decreases shelf life in blackberry, raspberry, and strawberry. Foliar Ca applied to strawberries has been shown to delay fruit harvest, reduce incidence of fruit rot and improve fruit firmness (Cheour et al., 1990; Singh et al., 2007; W ojcik and Lewandowski, 2003). In blackberries, preharvest Ca applications did not impact initial fruit firmness following machine harvest, but had a positive effect during storage (Morris et al., 1980). Hanson (1995) applied CaCl2 to blueberry plants with minimal impact on fruit quality. The objectives of this study were to test several Ca formulations with direct sprays of liquid products applied to developing fruit of strawberry, raspberry, blackberry, and blueberry cultivars and determine the impact on Ca concentrations of fruit and leaves, and fruit quality at harvest and during storage. Two methods of application were compared to assess the impact of spray coverage on

Organic Production Systems in Northern Highbush Blueberry: I. Impact of Planting Method, Cultivar, Fertilizer, and Mulch on Yield and Fruit Quality from Planting through Maturity

Floricane-fruiting blackberry (Rubus L. subgenus Rubus, Watson) cultivars, ‘Marion’, ‘Black Diamond’, ‘Onyx’, ‘Columbia Star’ (early-season trailing types), ‘Ouachita’ (erect, midseason), and ‘Triple Crown’ and ‘Chester Thornless’ (semierect, late season) were studied for 2 years to determine whether these cultivars and types of blackberry should be sampled at a certain stage of development or time of season to best evaluate plant nutrient status. Leaf nutrient standards are based on primocane leaves in most countries, but there is interest in using floricane leaves. Primocane leaves were sampled every 2 weeks from late May through early October, whereas leaves on fruiting laterals (floricane) were sampled every 2 weeks from early May through fruit harvest. Leaves were analyzed to determine the concentration of macronutrients and micronutrients. The pattern of change in primocane leaf nutrient concentration varied between the trailing and the later-fruiting erect and semierect types, particularly for P, K, Ca, Mg, B, andMn, where leaf levels were higher in the late season for the erect and semierect cultivars (except for P and K which were lower). Nutrient concentrations in floricane leaves decreased during growth and development of the lateral and fruiting season for N, P, K, and S, but increased for most other nutrients in all blackberry types. Floricane leaf N and K declined most rapidly during the fruit development period in all cultivars. Sampling of floricane leaves is not recommended, particularly for trailing types, as there are no sufficiency standards. In primocane leaves, the nutrients that did not show significant changes in concentration during the currently recommended sampling period of late July to early August were N, Mg, K, Ca, S, B, Mn, and Zn, but only in 2014. Leaf P, Fe, and Al were stable during this period in both years. In contrast, when sampling inmid to late August, leaf N,Mg, Fe,Mn, and Al were stable in both years and leaf K, Ca, S, B, Cu, and Zn were stable in one of the 2 years. We thus propose changing the recommended sampling time to mid to late August for these diverse blackberry cultivars. The current sufficiency standards for primocanes did not encompass the blackberry types and cultivars studied here, suggesting the standards may need to be revised for this region. About 6000 ha of blackberry (Rubus L. subgenus Rubus, Watson) were harvested in the United States in 2012, with 42% of this production located in Oregon (U.S. Department of Agriculture, 2014). Oregon is the leading producer of trailing blackberry in the United States but also produces erect and semierect types for the fresh market. The growth habit and fruiting season of trailing, erect, and semierect blackberry differ considerably (Strik and Finn, 2012). In Oregon, the fruiting season of trailing cultivars ranges from late June through July with erect and semierect types fruiting from late July through August and early August through early October, respectively. All of these blackberry types produce biennial canes. The primocanes of these floricanefruiting cultivars are vegetative in their first year of growth. In their second year, when they are called floricanes, they flower, fruit, and then senesce. In trailing types, primocanes are not self-supporting and are trained along the ground under the floricane canopy until trained to the trellis after fruit harvest and floricane pruning. By contrast, the primocanes of erect and semierect types are self-supporting and are summer pruned (tipped) to encourage branching. Summer pruning of primocanes affects leaf nutrient levels in primocane-fruiting blackberry (Strik, 2015). Commercial blackberry growers are encouraged to develop fertilization programs based on general guidelines for nitrogen (N) fertilizer, in which rates increase from the planting year to maturity (Hart et al., 2006). Adjustments of fertilizer N and other macronutrients and micronutrients are based on the periodic soil nutrient analysis, observations of plant growth, and annual leaf tissue analysis (Bolda et al., 2012; Bushway et al., 2008; Fernandez and Ballington, 1999; Hart et al., 2006; Krewer et al., 1999). In floricanefruiting blackberry and raspberry, leaf sampling of primocanes in mid to late-season informs growers of plant nutrient requirements for fruit production the following season, when the primocane becomes a floricane. Leaf sampling for tissue nutrient analysis is recommended for primocanes fromMay to August (Bolda et al., 2012), ‘‘following harvest’’ (Fernandez and Ballington, 1999), the first week of August (Bushway et al., 2008), or late July to early August (Hart et al., 2006). The recommended nutrient sufficiency levels are similar among these currently available nutrient management guides and all have the same standards and sampling time recommendations regardless of the blackberry type. Strik (2015) recommended that primocane-fruiting blackberry be sampled at the early green-fruit stage (about 8 weeks after summer pruning) than a particular calendar date and suggested the leaf sufficiency range for phosphorus (P) and potassium (K) may need to be lowered for this crop. Primocane leaf nutrient levels have been shown to vary over the growing season in erect (Clark et al., 1988) and trailing (Mohadjer et al., 2001) floricane-fruiting blackberry, primocane-fruiting blackberry (Strik, 2015), and floricane-fruiting raspberry (Hughes et al., 1979; John and Daubeny, 1972; John et al., 1976; Kowalenko, 1994; Wright and Waister, 1980). Although floricane leaves in blackberry have been shown to change over the fruiting season, standards for this leaf tissue type have only been developed in Brazil (Pereira et al., 2015). Cultivars of blackberry (FernandezSalvador et al., 2015a, 2015b, 2015c; Dixon et al., 2016; Harkins et al., 2014; Strik, 2015) and raspberry (John and Daubeny, 1972; John et al., 1976) differed in primocane leaf nutrient levels when sampled in midseason. By contrast, Clark et al. (1988) found no difference among three erect blackberry cultivars in leaf nutrient levels and speculated that this was because of their similar parentage. The objective of this study was to evaluate the impact of sample date on primocane leaf nutrient concentration in trailing, erect, and semierect blackberry cultivars with a goal of establishing the ideal sampling time for these crops. In addition, we studied the impact of sampling time during fruiting lateral development and fruiting on the nutrient concentration in the floricane to assess whether this might offer an alternative sampling method in these types of blackberry. Received for publication 23 Mar. 2017. Accepted for publication 28 Apr. 2017. The authors appreciate the valuable assistance of Cliff Pereira, Research Associate, Department of Statistics, OSU and funding provided by the Oregon Raspberry and Blackberry Commission. Professor. Faculty Research Assistant. Corresponding author. E-mail: bernadine.strik@ oregonstate.edu. 836 HORTSCIENCE VOL. 52(6) JUNE 2017 Materials and Methods Study site. The study was conducted in 2013 and 2014, in a mature planting at Oregon State University’s North Willamette Research and Extension Center, Aurora, OR [lat. 45 16#47##N, long. 122 45#23

Seasonal Variation in Leaf Nutrient Concentration of Northern Highbush Blueberry Cultivars Grown in Conventional and Organic Production Systems

W; USDA hardiness zone 8b (U.S. Department of Agricultural Research Service, 2014); the weather records for this site can be viewed at U.S. Department of Interior (2014)]. The soil is mapped as a Willamette silt loam, classified as a fine-silty, mixed, superactive, mesic, Pachic, Ultic, and Argixeroll. Plants were established in Spring 2010 except for ‘Triple Crown’ (planted Oct. 2010) and ‘Columbia Star’ (planted Sept. 2011) at 1.5 m in the row with 3 m between rows (2222 plants/ha). A permanent grass cover crop grew between the rows. The inrow area was maintained (bare soil) with preemergent herbicides and hoeing, as needed. Plants were irrigated with a single line of drip tubing (UniRam; Netafim USA, Fresno, CA) containing pressurecompensating emitters (1.9 L·h in-line) spaced every 0.6 m. Soil testing. Soil samples were collected on 12 Nov. 2013 and 21 Oct. 2014 using a 2.4-cm diameter, 0.5-m long, slotted, openside, chrome-plated steel soil probe (Soil Sampler Model Hoffer; JBK Manufacturing, Dayton, OH). Soil was sampled to a depth of 0.3 m at the center of the row, 0.3 m from the crown between plants and within the water emitter drip zone or fertilization area. A pooled sample was collected for the site (not replicated) and was sent for analysis of macronutrient and micronutrient concentration and pH to Brookside Laboratories Inc. (New Bremen, OH) (Table 1). Cultivars. Four trailing blackberry cultivars (‘BlackDiamond’, ‘Columbia Star’, ‘Marion’, and ‘Onyx’), one erect type (‘Ouachita’), and two semierect types (‘Chester Thornless’ and ‘Triple Crown’) were studied. Production system. The trailing cultivars were grown in an alternate year production system (Strik and Finn, 2012), but only plants in the fruiting or ‘‘on year’’ were sampled in 2013 and 2014. Plants were trained on a two-wire vertical trellis system in each row with the wires attached to steel posts at 1.0 and 1.6 m above the ground. New primocanes were trained along the ground in the row, under the floricane canopy during the growing season, per standard practice. In the erect and semierect blackberry cultivars, primocanes were tipped at a height of 1.0–1.5 m per standard practice to encourage branching. Floricanes were removed in autumn (after they had senesced). Primocanes were then trained to the same two-wire vertical trellis system as the trailing cultivars by wrapping and tying as necessary. Primocane branches were pruned to 1 m, in winter, as needed. Fertilizer nutrients were applied per standard recommendations (Hart et al., 2006) and using results from soil analysis (Table 1). In 2013, 79 kg·ha N was applied in a split application with 34 kg·ha on 3 Apr. (8N–7.5P–14K) and 45 kg·ha on

Understanding vine balance : an important concept in vineyard management

A long-term trial was established in Oct. 2006 in western Oregon to identify organic production systems for maximum yield and quality in highbush blueberry (Vaccinium corymbosum L.). The planting was transitional during the first year after planting and was certified organic during fruit production (2008–16). Treatments included plantingmethod (on raised beds or flat ground), fertilizer source (granular feather meal or fish solubles), and rate (‘‘low’’ and ‘‘high’’ rates of 29 and 57 kg·ha N during establishment, increased incrementally as the planting matured to 73 and 140 kg·ha N, respectively), mulch [sawdust, yard debris compost topped with sawdust (compost + sawdust), or black, woven polyethylene groundcover (weed mat)], and cultivar (‘Duke’ and ‘Liberty’). Mulches were replenished, as needed, and weeds were controlled throughout the study. Raised beds resulted in greater yield than flat ground during the establishment years but had less effect on yield once the plants weremature. After 9 years, cumulative yield was 22% greater on raised beds than on flat ground in ‘Liberty’ but was unaffected by plantingmethod in ‘Duke’. Cumulative yield was also 10% greater with feather meal than with fish solubles, on average, and 4% greater with the low rate than with the high rate of fertilizer. ‘Duke’ was particularly sensitive to fertilizer source and produced 35% less yield overall with fish solubles than with feather meal. By contrast, there was relatively little effect of fertilizer source or rate on yield in ‘Liberty’. In five of 9 years, yield was 8% to 20% greater with weedmat than with sawdust or compost + sawdust. Mulch type had no effect on cumulative yield of ‘Duke’, but cumulative yield of ‘Liberty’ was 11% greater with weedmat than with sawdust or compost + sawdust. Soil temperature was warmer under weedmat than under sawdust, and plants on raised beds covered with weed mat required more irrigation than those grown on flat ground mulched with sawdust. ‘Duke’ produced heavier, larger, and firmer berries with lower total soluble solids (TSS) than ‘Liberty’. However, other treatment effects on berry quality were relatively small and inconsistent. For example, berry weight was greater on raised beds than on flat ground, on average, but only by 3% (0.06 g/berry). Plants on raised beds also produced berries with slightly lower TSS than those on flat ground (15.2%and 15.7%, respectively, in ‘Liberty’, and 13.1% and 13.3%, respectively in ‘Duke’). There was no effect of fertilizer source or rate on TSS in ‘Liberty’ (15.5% on average), whereas in ‘Duke’, TSS was highest when fertilized at the high (13.7%) or low (13.4%) rate of fish, and was lower when using feather meal (12.9% and 13.1% for low and high rate, respectively). Plants fertilized with fish produced firmer fruit than with feather meal in five of the 7 years in which the measurements were taken. Also, fertilization with the higher rate of either product increased berry firmness comparedwith the low rate in six of the 7 years. The impact ofmulch was inconsistent through the study period. On average, ‘Duke’ berries were softest when fertilized with the low (173 g·mm deflection) and high (176 g·mm) rates of feathermeal andwere the firmest with the high rate of fish (182 g·mm). In ‘Liberty’, the low rate of feather meal produced softer fruit (157 g·mm) than the other fertilizer treatments (162 g·mm on average).When this study was initiated in 2006, the most common organic production system in this region was raised beds with sawdust mulch and fertilizing with a high rate of fish solubles. For this production system, yield for mature plants in our study (2014L16) was the equivalent of 8.9L12.3 t·ha in ‘Duke’ and 11.8L23.7 t·ha in ‘Liberty’. However, when plants were grown on raised beds with weed mat and fertilized with the high rate of feather meal, yield increased to 10.2L19.3 t·ha, depending on year, in ‘Duke’. By contrast, there was little effect of production system on yield of mature ‘Liberty’ plants. These yields, particularly for the best-performing treatment combination in ‘Duke’, are similar to what are observed in commercial conventional fields or organic farms using similar management practices. Our results showed that choice of organic production system can have significant impact on yield and economic costs and returns. The Pacific northwestern United States is an important growing region for northern highbush blueberry (Vaccinium corymbosum L.). According to recent U.S. surveys, this region accounted for 20% of the total conventional area of highbush blueberry (U.S. Department of Agriculture, 2014) and 49% of the total organic area (U.S. Department of Agriculture, 2010). Organic blueberry production has increased in this region because of strong consumer demand, price premiums of 20% to 200% over conventional fruit, and a dry summer climate, which reduces the potential incidence for weeds, insect pests, and leaf and fruit diseases (DeVetter et al., 2015; FernandezSalvador et al., 2017; Strik, 2014). However, there were some challenges specific to organic production that needed to be addressed, including greater production costs and inputs (particularly for fertilization and weedmanagement), limited Organic Materials Review Institute (OMRI)-approved options for disease and insect control, and potential or perceived reduced yields of organic plantings and associated returns (Strik, 2014). In 2006, the production guides available for organic northern Received for publication 5 June 2017. Accepted for publication 1 July 2017. The authors value the assistance of Gil Buller and Emily Vollmer, former Faculty Research Assistants at the North Willamette Research and Extension Center, OSU and all of the members of our industry advisory board.We appreciate the funding support provided by the Oregon Blueberry Commission, Washington Blueberry Commission, Northwest Center for Small Fruits Research, and the USDA National Institute of Food and Agriculture (Formula Grant no. OREI 2008-04443). Corresponding author. E-mail: bernadine.strik@ oregonstate.edu. HORTSCIENCE VOL. 52(9) SEPTEMBER 2017 1201 highbush blueberry in North America were based on anecdotal information (Krewer and Walker, 2006; Kuepper and Diver, 2004). There was little research at that point comparing organic production strategies in blueberry, and most of the production research done in conventional blueberry systems was not applicable to organic systems. Highbush blueberry is typically planted on raised beds. Raised beds improve soil drainage (Strik, 2007), limit compaction (Magdoff and Van Es, 2010), reduce incidence of root pathogens such as Phytophthora (Bryla and Linderman, 2007), and improve efficiency of machine harvest (Strik and Buller, 2002). However, planting on flat ground can be beneficial to root growth in southern highbush blueberry (complex hybrids based largely on V. corymbosum and V. darrowiiCamp.) likely due to increased soil moisture and reduced soil temperature during the fruiting season (Spiers, 1995). Furthermore, mechanical weed-control methods are more effective on flat ground than on raised beds (Sciarappa et al., 2008; B. Strik, personal observation). Weed management is critical for successful production of blueberries (Pritts et al., 1992; Strik et al., 1993), but chemical herbicide options available for organic systems are expensive and limited and usually are not very effective on established perennial weeds (Julian et al., 2012; Larco et al., 2013a). Other forms of weed control such as organic mulches, propane flaming, string trimming, and hand weeding are often used instead (Burkhard et al., 2009; Granatstein and Mullinix, 2008; Krewer et al., 2009; Sciarappa et al., 2008). Organic mulches provide additional benefits in highbush blueberry, including increased yield and plant growth (Clark and Moore, 1991; Goulart et al., 1997; Karp et al., 2006; Kozinski, 2006; Krewer et al., 2009; Savage, 1942; White, 2006). Douglas fir (Pseudotsuga menziesii M.) sawdust is commonly used to mulch blueberry plantings in Oregon, Washington, and British Columbia, but sawdust has become expensive in the region (Julian et al., 2011a), and it tends to immobilize a considerable amount of the N applied from fertilizers (White, 2006). Some growers are using compost in addition to sawdust to provide additional nutrients and organic matter (Gale et al., 2006; Larco et al., 2014). Municipal yard debris compost is readily available in many production regions and may be suitable for commercial blueberry production (Sullivan et al., 2014). Weed mat (perforated landscape fabric) is approved for use as a weed barrier by the United States Department of Agriculture (USDA) Organic National Program (USDA-AMS-NOP, 2011), and because of economic advantages, it has been adopted by both organic and conventional blueberry growers (Julian et al., 2012; Strik and Vance, 2017). However, increased soil temperature under the weed mat can reduce plant growth (Neilsen et al., 2003;Williamson et al., 2006) and yield (Krewer et al., 2009). Larco et al. (2013a) reported that northern highbush blueberry grew less with weed mat than with sawdust mulch by the end of the first two growing seasons; however, the plants had greater yield with weed mat in the second year, which was the first season of fruit production. In addition to weed management, availability and affordability of fertilizers are of critical importance for the economical production of organic blueberry (Strik, 2014). Fish solubles and feather meal are common fertilizers used by organic blueberry growers. Fish solubles are typically applied by fertigation through the drip irrigation system, especially when weed mat is used and other application methods are less practical or more expensive. Feather meal is a granular product applied to the soil surface. Both fertilizers mineralize readily on application and quickly release N and other nutrients (Bar