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  • Author or Editor: Amanda J. Vance x
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Northern highbush blueberry (Vaccinium corymbosum L.) cultivars were evaluated for leaf and fruit nutrient concentration at two production sites in 2013–14. The treatments included cultivar (Duke, Bluecrop, Draper, Legacy, Liberty, and Aurora), site [“conventional” (conventionally managed, grower-collaborator site) and “organic” (certified organic research site)], and amendment–mulch [at the organic site only; “organic mulch” (included preplant amendment and a surface mulch of yard debris compost and sawdust); and “weed mat” (no preplant amendments but with a sawdust mulch topped with weed mat)]. Leaf samples were collected every 2 weeks in all treatment plots from late April through early October of each year. Ripe fruit were subsampled from the second harvest for each cultivar. Fruiting season varied from 22 June to 19 Sept. and the highest yielding cultivar, Legacy, had 114% to 330% greater yield than the lowest, Duke, depending on year and site. Cultivar had a significant effect on all fruit nutrients except for phosphorus (P) at the conventional site. Nitrogen (N) and potassium (K) accounted for the largest proportion of nutrient content in the fruit, with 10 to 52 kg·ha–1 and 7 to 34 kg·ha–1 removed in the harvested fruit, respectively, depending on cultivar and site. Fruit carbon concentration ranged from 32% to 44% dry weight with 0.5 to 3.2 t·ha–1 removed in harvested fruit. There were significant year, site, and cultivar effects on leaf nutrient concentrations on many sample dates throughout the season. Despite relatively large differences in management between sites and yield and fruiting season among cultivars, the pattern in leaf nutrient concentration over sampling time was relatively similar between sites and years. Leaf manganese (Mn) and aluminum (Al) concentrations were higher when plants were grown with weed mat as compared with the organic mulch treatment, because soil pH was lower under weed mat than in the organic mulch treatment. ‘Liberty’ had the highest leaf N throughout much of the season at the conventional site. There were relatively large differences among cultivars in leaf magnesium (Mg), calcium (Ca), and K when sampling from mid-July to autumn at both sites. ‘Duke’ and ‘Bluecrop’ tended to have the highest leaf K during this period, whereas ‘Legacy’ and ‘Liberty’ had the lowest. There were greater differences in leaf Ca among cultivars at the conventional site than at the organic site. ‘Draper’ and ‘Legacy’ had higher leaf Ca than ‘Duke’. Leaf nutrient concentrations were within the current published sufficiency levels on many sample dates throughout the season for P, Mg, sulfur (S), Mn, and zinc (Zn), on many dates in midseason for K and Ca, and from mid- to late-season for boron (B) and iron (Fe). However, only when sampled in late July to early August, the current recommended sampling time, was leaf N within sufficiency range. Moreover, there was an effect of cultivar on the concentration of most leaf nutrients at both sites when sampled in late July to early August. The recommended sampling time to determine plant nutrient status in northern highbush blueberry should remain at late July to mid-August, regardless of cultivar, when most nutrients are relatively stable. We recommend lowering the leaf sufficiency range for P and copper (Cu) based on our findings.

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The relationship between individual berry weight and viable seed number of small- (<15 mm), medium- (15–19 mm), and large-diameter (>19 mm) berries was studied over 2 years in nine cultivars (Aurora, Bluecrop, Bluegold, Draper, Duke, Liberty, Legacy, Ozarkblue, and Reka) through their harvest seasons. Plants were grown with two different preplant amendment-mulch treatments, but this treatment had no effect on the variables measured, so data were pooled. The highest average seeds/berry was in ‘Bluecrop’ (55.5) and ‘Duke’ (50.0) and the lowest in ‘Bluegold’ (17.1), ‘Aurora’ (22.5), and ‘Liberty’ (23.5). Average berry weight over the fruiting season ranged from 1.79 and 1.80 g for ‘Liberty’ and ‘Reka’, respectively, to 2.30 and 2.44 g in ‘Ozarkblue’ and ‘Draper’, respectively. The average number of seeds/berry was higher in 2010 than in 2009 for all cultivars, ranging from 14% higher in ‘Reka’ to 96% higher in ‘Liberty’. The flowering period was earlier in 2010 than in 2009, but bloom was concentrated in 2009 (28 days) compared with 2010 (45 days), likely affecting pollinator success. In general, seeds/berry and berry weight declined through the harvest season. Some cultivars had a considerable difference in the number of seeds in large-sized than in small-sized berries (e.g., 89%, 107%, 108%, and 147% more seeds in ‘Aurora’, ‘Reka’, ‘Bluegold’, and ‘Liberty’, respectively), whereas others had relatively little difference (14% and 36% in ‘Draper’ and ‘Bluecrop’, respectively). There was a linear relationship between berry weight and viable seeds/berry. Cultivars did not differ in the berry weight per seed (slope of the line) between the 2 years, except for ‘Draper’ (only significant in 2009), ‘Legacy’, and ‘Reka’. ‘Bluegold’ had the greatest berry weight per seed and ‘Reka’ the lowest. The weakest relationship between berry weight and seed number was in ‘Draper’. Cultivars that produced parthenocarpic fruit of marketable size were ‘Aurora’, ‘Bluegold’, and ‘Liberty’. ‘Duke’, ‘Legacy’, ‘Reka’, and ‘Ozarkblue’ produced commercially acceptable fruit (0.75–1.0 g) with fewer than 7 seeds/berry. By contrast, some cultivars required a relatively large number of seeds to produce a berry including ‘Bluecrop’ (28–40 seeds), ‘Draper’ (15–23 seeds), and ‘Legacy’ in 2010 (20 seeds). The number of seeds per berry accounted for as much as 87% of the variability in berry weight indicating the importance of good pollination and seed set for berry weight and yield in these cultivars.

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Fresh market blueberry (Vaccinium sp.) sales require high-quality, firm fruit with no significant defects. A new phospholipid biofilm product was developed to reduce splitting and increase firmness when applied directly to blueberry fruit. Two trials were undertaken to test the effects of the biofilm using various application timings and methods. In highbush blueberry cultivar Elliott (Vaccinium corymbosum), four treatments included: 1) rate and timing on the current product label (5- to 10-mm berry size, 10% to 20% color change, and between the first and second harvests), 2) addition of a preharvest timing (5- to 10-mm berry size, 10% to 20% color change, and 7 to 10 days preharvest); 3) starting applications later (10% to 20% color change, 7 to 10 days preharvest, and between the first and second harvests), and 4) a water-sprayed control. Biofilm was applied at a rate of 2 qt/acre for all applications. In highbush blueberry cultivar Legacy (Vaccinium corymbosum × Vaccinium sp.), the same volume of biofilm was applied via an airblast sprayer or through an overhead sprinkler system typically used for chemigation and compared with a water-sprayed control. Data collected included yield (in ‘Elliott’), berry weight, firmness, skin toughness, total soluble solids (TSS), weight loss during storage, percent splitting (in ‘Legacy’), and a visual rating, evaluated on the day of harvest and about 14 and 28 days postharvest. There were no visual defects caused by application of biofilm. Compared with the controls in either study, biofilm had no consistent impact on fruit quality, firmness, shelf life, yield in ‘Elliott’, or splitting in ‘Legacy’.

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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, and Mn, 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 in mid 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.

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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 fresh market quality of berries. Products were applied in strawberry (Fragaria ×ananassa 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.

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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, and Aurora), amendment-mulch [“compost + sawdust” (included preplant amendment and a surface mulch of either an agricultural on-farm crop waste compost or yard-debris compost and sawdust), and “weed mat” (no preplant amendments but with a sawdust mulch topped with weed mat)]. 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 treatment was 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 low values (e.g., 22% to 45% in ‘Bluecrop’). The number of flowers per bud was affected only 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 amendment-mulch 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 from plants grown with weed mat were firmer than when compost + sawdust was used. ‘Draper’ fruit were much firmer than those of the other cultivars in all years of the study. The number of flower buds per plant multiplied by the number 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 plants matured 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 grown with weed mat, whereas ‘Bluegold’ and ‘Liberty’ were unaffected by amendment-mulch treatment. Because weeds were managed in all plots, the cultivar response to amendment-mulch was likely a reflection of sensitivity to preplant amendment with on-farm compost 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.

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Vigor and crop level management are important practices for premium wine grape production. The implications of crop thinning ‘Pinot noir’(Vitis vinifera L.) vines of varying vigor were investigated in the Willamette Valley of Oregon in 2011 to 2013 to better understand the relationship between canopy size and yield within the framework of a cool-climate, premium production wine grape vineyard. To manipulate vigor, a competitive grass cover crop (Festuca rubra L.) was grown in both (Grass), alternating (Alternate), or neither side of the flanking alleyways (Tilled). Vines within each vineyard floor treatment had two crop levels applied, including cluster thinning to one cluster per shoot (Half Crop) or no crop thinning (Full Crop). Grass treatment had reduced leaf area and leaf nitrogen (N) concentrations during all years compared with Tilled treatments. Leaf photosynthesis was also lower in Grass treatments despite more light in the canopy interior. Grass treatments had lower yield than Tilled treatments in 2 of 3 years and lower yeast assimilable nitrogen (YAN) concentrations in fruit every year. There was limited impact of floor treatments on total soluble solids (TSS) and pH. Reduced yields through cluster thinning had limited impact on vegetative growth but increased TSS and pH, in 2 of 3 years. There were few floor management by crop level interactions in any year. Grass effectively reduced vegetative growth to moderate vigor levels with cane weights between 20 and 40 g. Using a competitive grass cover crop may be an effective strategy to reduce excessive vine growth and require less labor in canopy management and crop thinning without compromising basic fruit ripeness, although YAN levels need to be monitored.

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Growers of high-end ‘Pinot noir’ wine grapes (Vitis vinifera L.) commonly reduce yield by cluster thinning with the goal of increasing fruit quality; however, there are no objectively defined yield targets to achieve optimum fruit composition. Canopy leaf area relative to fruit yield can affect total soluble solids (TSS), and recommendations have been established for warm wine grape production regions. However, the relationship between leaf area and photoassimilation differs among climates and training systems. Leaf area to yield (LA:Y) ratios developed in warm, arid regions may not be suitable for cool, wet regions such as western Oregon. A 3-year field study was conducted to elucidate relationships between canopy to yield ratios and berry composition for ‘Pinot noir’. Vegetative growth and fruit yield were manipulated through competitive cover cropping and cluster thinning. Growth was manipulated in three ways: perennial red fescue (Festuca rubra L.) was grown in 1) both (Grass), 2) one (Alternate), or 3) neither (Tilled) of the alleyways flanking the vine row. Within each vineyard floor treatment, fruit clusters were thinned to one per shoot (Half Crop) or vines were left unthinned (Full Crop). Floor management influenced both canopy size and yield because of altered vine nitrogen (N) status. Effects of crop load on berry components were not always consistent between the crop load metrics used [yield to pruning weight (Y:PW) ratio or LA:Y]. In 2 years, TSS reached a maximum at similar LA:Y; however, this did not necessarily produce optimum TSS. Yield had the greatest influence on pH and total anthocyanins (ACY) in the highest yielding, coolest year. Crop load metrics were not reliable predictors of TSS because of the dominant effect of seasonal variation. Relationships between canopy to yield metrics and other berry components were partially explained by tissue N, photosynthetic photon flux (PPF) through the cluster zone, and/or yield. Cluster thinning to adjust yields may not alter source to sink relationships or canopy to yield ratios enough to overcome ripening limitations in cool climates. Only one wine vintage had sensory differences with Alternate-Half Crop and Alternate-Full Crop wines ranked high quality and Tilled-Half Crop and Tilled-Full Crop wines ranked low quality by both consumer and winemaker panels. Therefore, cluster thinning may have limited impact on wine sensory properties.

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