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  • Author or Editor: Amanda 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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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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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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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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The impact of various production systems on leaf nutrient concentration and soil organic matter, pH, and nutrient status was evaluated from the first growing season (2007) through maturity (2016) in a certified organic planting of northern highbush blueberry (Vaccinium corymbosum L.). Treatments included planting method (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−1 N, respectively, during establishment, increased incrementally as the planting matured to 73 and 140 kg·ha−1 N, respectively), mulch [sawdust, yard-debris compost topped with sawdust (compost + sawdust), or black, woven polyethylene groundcover (weed mat)], and cultivar (Duke or Liberty). Mulches were replenished, as needed, and weeds were controlled throughout the study. The impacts of year, planting method, fertilizer, mulch, and cultivar on leaf and soil nutrient levels over this 10-year study were complex with many interactions among treatments. Soil pH remained within the recommended range for all treatments. Plants fertilized with fish solubles had higher leaf N, P, and K concentrations than those fertilized with feather meal, particularly at the high N rate in both cultivars. By contrast, fertilization with feather meal increased leaf Ca. Compost + sawdust added a cumulative (2007–16) total of 2274, 400, 961, and 2744 kg·ha−1 of N, P, K, and Ca, respectively, over the use of sawdust alone, and increased the concentration of P, K (as much as 90%), Ca, and Mg in the soil relative to other mulches. Soil organic matter content averaged 4.1% under compost + sawdust, 3.3% under sawdust, and 2.9% under weed mat, averaged over the last 5 years. Mulching with weed mat or compost + sawdust increased leaf K compared with sawdust in both cultivars, regardless of fertilizer treatment. Leaf Ca, on the other hand, was highest with sawdust and tended to be lowest with weed mat in both cultivars. Soil nutrient levels were not consistently correlated with leaf nutrient concentrations, other than between soil NO3-N and leaf N (5 years) and between soil and leaf K (4 years). On average, raised beds resulted in higher concentrations of N, P, K, Fe, and Al and lower concentrations of Ca, Mg, and B in the leaves than planting on flat ground. Furthermore, concentrations of N and Ca in recent fully-expanded leaves at standard sampling time was higher in young plants than in mature plants in both cultivars, whereas the opposite was found for leaf P. In ‘Duke’, yield was positively correlated with leaf Ca in 8 out of 9 years and negatively correlated with leaf K and P in 5 and 6 years, respectively. Leaf Ca and Mg were also negatively correlated with leaf K in most years for both cultivars, as was leaf N. Although leaf N concentration was higher with added compost, regardless of fertilizer source in ‘Duke’, and when fertilized with feather meal in ‘Liberty’, this was not correlated with yield. High N rates increased leaf N concentration, but did not result in greater yield. While soil and leaf tissue testing are important to help manage fertilizer programs, the lack of a consistent relationship between soil and plant nutrient status and yield was a reflection of the complicated interactions that occurred among nutrients in these organic production systems. Soil nutrient imbalances and changes in leaf nutrient concentrations associated with extended use of compost + sawdust mulch and fish solubles may lead to growth and yield problems in longer-lived plantings. In addition, the loss of organic matter under weed mat would need to be addressed in long-term plantings for sustainable production.

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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 planting method (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−1 N during establishment, increased incrementally as the planting matured to 73 and 140 kg·ha−1 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 were mature. After 9 years, cumulative yield was 22% greater on raised beds than on flat ground in ‘Liberty’ but was unaffected by planting method 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 weed mat 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 weed mat than with sawdust or compost + sawdust. Soil temperature was warmer under weed mat 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 compared with the low rate in six of the 7 years. The impact of mulch was inconsistent through the study period. On average, ‘Duke’ berries were softest when fertilized with the low (173 g·mm−1 deflection) and high (176 g·mm−1) rates of feather meal and were the firmest with the high rate of fish (182 g·mm−1). In ‘Liberty’, the low rate of feather meal produced softer fruit (157 g·mm−1) than the other fertilizer treatments (162 g·mm−1 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 (2014−16) was the equivalent of 8.9−12.3 t·ha−1 in ‘Duke’ and 11.8−23.7 t·ha−1 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 10.2−19.3 t·ha−1, 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.

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