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- Author or Editor: Bernadine Strik x
The effect of early cropping (no removal of fruit buds the first two years) and in-row spacing (0.45 or 1.2 m) on growth and yield of `Duke', `Bluecrop', and `Elliott' northern highbush blueberries (Vaccinium corymbosum L.) was studied. Plants were grown on raised beds for four years. No yield was produced on the control plants in the planting year (year 1) and year 2. Plant growth at the start of year 3 was adversely impacted by early cropping in years 1 and 2. Early cropping reduced the dry weight of the root system, crown, and 1- to 3-year-old wood in all cultivars. `Bluecrop' plants had less total dry weight than those of `Duke' or `Elliott'. Roots accounted for 30% to 45% of the total plant dry weight depending on cultivar. Early-cropped plants had a lower percentage of fruit buds than control plants. Early cropping reduced yield 44%, 24%, and 19% in year 3, compared to control plants, in `Elliott', `Duke', and `Bluecrop', respectively. Cumulative yield (years 1 through 4) was similar between control and early cropped plants in `Bluecrop' and `Duke', whereas early cropping reduced cumulative yield in `Elliott' 20% to 40%, depending on in-row spacing. Plants spaced at 0.45 m produced 62% to 140% more yield per hectare than those spaced at 1.2 m, depending on cultivar. `Elliott' plants seemed less suited to high density planting due to their large root system.
Many growers in the Pacific Northwest are planting blueberry fields at higher densities to improve yields and increase the number of berries harvested per acre in the first few years after planting. The objective of this study was to determine the effect of high-density planting on blueberry water requirements. Although close spacing reduces individual plant size, we expected that plants spaced closer together would require more irrigation per unit land area than those spaced further apart due to increased canopy coverage within rows. The study utilized a 5-year-old planting of highbush blueberry, consisting of three cultivars, `Duke', `Bluecrop', and `Elliott', planted at 0.5- and 1.2-m in-row spacings. Plant water use was calculated from changes in soil water content measured using TDR probes for shallow depths and a neutron probe and access tubes for deeper depths. Stem water potentials were also measured periodically using a pressure chamber to determine how well irrigation was meeting crop water demands throughout the season. Surprisingly, plants spaced 0.5 m apart required only slightly more water than those spaced 1.2 m apart. They did, however, require more frequent irrigations due to their smaller root systems, especially during fruit filling. Water use by each cultivar increased during fruit filling and then rapidly decreased after harvest. `Duke' required the most water among cultivars, using 5–10 mm/day from mid-May to mid-August, while `Elliott' required the least, using 3–5 mm/day.
Primocane-fruiting blackberry (Rubus L. subgenus Rubus, Watson) cultivars, Prime-Jan® and Prime-Jim®, grown only for a primocane crop, were studied for 2 years to evaluate whether this type of blackberry should be sampled at a certain stage of development or time of season to best evaluate plant nutrient status. Leaves were sampled every 2 weeks from a primocane height of ≈0.75 m in spring through fruit harvest in autumn and were analyzed to determine concentration of macro- and micronutrients. Primocanes were summer pruned at 1.4 m, by hedging to a height of 1.0 m, to induce branching, a standard commercial practice. Leaf nutrient concentration was related to stage of primocane growth and development and whether the leaves originated on the main cane or on the branches that resulted from summer pruning. Nutrient concentration of leaves sampled on the main primocane from early growth in spring until early branch growth in summer was significantly affected by cultivar, year, and week for most nutrients. When leaf sampling occurred on the older leaves of the main cane (for 4 weeks after hedging), the concentration of Ca, Mg, B, Fe, Mn, and Al increased, likely a result of the relative immobility of most of these nutrients. When samples were taken on primocane branches, leaf N, Mg, S, B (2009 only), Fe, Mn, Cu (2009 only), Zn, and Al concentrations did not differ between samples taken 6–8 weeks after summer pruning or hedging. Leaf K and Ca were more stable when sampling was done from weeks 8 to 10 (early bloom to green/early red fruit). There was a significant difference in leaf P among all weeks sampled during this period. A sample date corresponding to early green fruit stage (week 8) would thus likely provide the best compromise for assessing plant nutrient status in this crop. During this stage of development the nutrient concentrations measured for both cultivars and years, were within the present recommended nutrient sufficiency levels for other blackberry and raspberry crops for all except leaf K and P which were below current standards. The results suggest leaf sampling primocane-fruiting blackberry at the early green fruit stage (about 8 weeks after summer pruning) rather than a particular calendar date. The present leaf sufficiency range for P and K may need to be lowered for this crop. In addition, sampling cultivars separately for tissue analysis would still be advised to better manage nutrient programs.
All life stages of grape phylloxera [Daktulosphaira vitifoliae (Fitch) (Homoptera: Phylloxeridae)] were eradicated with a hot-water treatment (dip) of 5 minutes at 43 °C (110 °F) to warm roots, followed by a 5-minute dip at 52 °C (125 °F). Neither grafted nor nongrafted dormant grape plants were damaged by the hot-water treatment.
A 4-year trial was established in Oct. 2016 in western Oregon to evaluate the effects of various in-row mulch treatments on yield, fruit quality, and costs of installation and maintenance during establishment of northern highbush blueberry (Vaccinium corymbosum L. ‘Duke’). The treatments included douglas fir [Pseudotsuga menziesii (Mirb.) Franco] sawdust, black weed mat (woven polypropylene groundcover), green weed mat, and sawdust covered with black or green weed mat. Fruit were harvested during 2018–20 (second through fourth growing seasons). Weed mat color had no effect on yield or fruit quality. In 2018, yield was higher with black weed mat over sawdust mulch than with black weed mat alone, whereas mulch had no effects during 2019 and 2020, or on cumulative yield. Percent total soluble solids in the berries was highest with sawdust and weed mat alone compared with weed mat over sawdust mulches, whereas berry weight, diameter, and firmness were unaffected by mulch. Sawdust was the most expensive mulch over the lifespan of the planting because it required replenishment after 2 years. Black weed mat over sawdust resulted in the highest net profit when fruit sales and cost of materials and labor were considered.
`Meeker' red raspberry (Rubus idaeus L.) cane densities of 5, 10, or 15 canes/hill in a hill system, with canes topped at 2 m or the entire cane length retained and looped, were compared with a 15- or 30-cm-wide hedgerow with canes topped at 2 m from 1995 to 1997. Cane density among all treatments ranged from 2.2 to 9.9 canes/m2 during the study. Plots were harvested by machine every 2 days. Within the hill system, total yield increased with cane density in all years. Looped treatments produced a higher yield/plot than did topped ones in all years except 1996, when the yield difference was insignificant because looped canes had greater winter injury. Weight per fruit ranged from 5.4% to 9.7% less on looped than on topped canes. Hedgerow systems had a lower yield than hill systems in 1996, but a higher yield in 1997. Losses due to machine harvest were not affected by pruning (cane density or topping) or production system (hill system or hedgerow) and averaged 16.2% of total yield in 1997. Thirty-five percent of the loss due to machine harvest occurred between harvests.
The following pruning treatments were studied in mature `Bluecrop' (1996-2000) and `Berkeley' (1996-98) plants: 1) “conventional” pruning with removal of unproductive canes, thinning of 1-year-old shoots at the base of the bush, and removal of any unproductive wood or thinning of excessive fruiting wood near the top of the bush, as required; 2) “speed” pruning involving removal of one or two of the most unproductive canes at the base of the bush; and 3) “un-pruned” where no pruning was done for the length of this study. Conventional pruning took an average of 6.4 min/plot, while speed pruning saved 88.8% time. There was no pruning treatment effect on the percentage of fruit buds in `Berkeley' (42%) or `Bluecrop' (34%) or percent fruit set (70% to 90%, depending on cultivar and year) in any year. Un-pruned plants of both cultivars had significantly greater yield than conventionally pruned plants, depending on the year, while speed pruning generally resulted in intermediate yields. Un-pruned and speed-pruned plants produced berries that were 19% to 27% smaller than conventionally pruned plants, depending on year. The fruit harvest season of un-pruned plants began 3 to 5 days later and lasted a week longer than that of conventionally pruned plants. The harvest efficiency of un-pruned plants was reduced as much as 51% in the later years of this study and was most closely correlated with berry weight. Conventionally pruned plants had a significantly higher percentage of the above-ground dry weight allocated to 1-year-old wood and crown than un-pruned plants. In `Bluecrop', N concentration tended to be higher in the crown of conventionally pruned plants than in un-pruned or speed-pruned plants. Conventionally pruned `Bluecrop' plants had significantly higher concentrations of K and P and lower N than un-pruned plants and `Berkeley' had lower concentrations of N, than un-pruned plants. Results indicate that not pruning mature plants may be an option in the short-term, but may have undesirable effects for long-term sustainability.
Summer pruning systems were compared for ‘Prime-Jan’® primocane-fruiting blackberry (Rubus subgenus Rubus) grown in a fully closed, plastic covered tunnel in Aurora, OR. Individual canes were soft-tipped (by removing 0.10 m) or hard-tipped (removing 0.45 m) to a 1-m height on each of four dates in 2008 and 2009. On average, canes that were hard-tipped produced more branches and had more fruit/cane than soft-tipped canes. Canes that were tipped early (22–27 June) produced more fruit/cane than those tipped later (7–24 July). When canes were hard-tipped early in the season, the number of fruit/cane was increased threefold compared with soft-tipping canes early. In contrast, when plots were hedged to 1-m tall lightly (“soft” hedge removing 0.10 m) on 22–27 June or more severely (“hard” hedge, removing 0.45 m) on 29 June–2 July, using shears, there was no significant effect on yield/plot. The hard-hedge treatments may have performed better if they had been done earlier or at the same time as the soft-hedge treatments; this would only have been possible if canes had been cut back (hedged) to a shorter height than 1 m. Hard hedging, done ≈1 week later than soft hedging, delayed the fruiting season by 10–14 days. Fruit harvest continued until early to mid-November. Daily average air temperature in the closed tunnel was 2–7 °F warmer than the outside and fruit were protected from autumn rainfall. Hard-tipping individual canes, by hand, or hedging primocanes mechanically early in the season shows promise in this crop for maximizing economic returns.
Northern highbush blueberry (Vaccinium corymbosum) is well adapted to acidic soils with low nutrient availability, but often requires regular applications of nitrogen (N) and other nutrients for profitable production. Typically, nutrients accumulate in the plant tissues following the same pattern as dry matter and are lost or removed by leaf senescence, pruning, fruit harvest, and root turnover. Leaf tissue testing is a useful tool for monitoring nutrient requirements in northern highbush blueberry, and standards for analysis have been updated for Oregon. Until recently, most commercial plantings of blueberry (Vaccinium sp.) were fertilized using granular fertilizers. However, many new fields are irrigated by drip and fertigated using liquid fertilizers. Suitable sources of liquid N fertilizer for blueberry include ammonium sulfate, ammonium thiosulfate, ammonium phosphate, urea, and urea sulfuric acid. Several growers are also applying humic acids to help improve root growth and are injecting sulfuric acid to reduce carbonates and bicarbonates in the irrigation water. Although only a single line of drip tubing is needed for adequate irrigation of northern highbush blueberry, two lines are often used to encourage a larger root system. The lines are often installed near the base of the plants initially and then repositioned 6–12 inches away once the root system develops. For better efficiency, N should be applied frequently by fertigation (e.g., weekly), beginning at budbreak, but discontinued at least 2 months before the end of the growing season. Applying N in late summer reduces flower bud development in northern highbush blueberry and may lead to late flushes of shoot growth vulnerable to freeze damage. The recommended N rates are higher for fertigation than for granular fertilizers during the first 2 years after planting but are similar to granular rates in the following years. More work is needed to develop fertigation programs for other nutrients and soil supplements in northern highbush blueberry.
Raspberry and blackberry (Rubus sp.) plantings have a relatively low nutrient requirement compared with many other perennial fruit crops. Knowledge of annual accumulation of nutrients and periods of rapid uptake allows for better management of fertilization programs. Annual total nitrogen (N) accumulation in the aboveground plant ranged from 62 to 110 and 33 to 39 lb/acre in field-grown red raspberry (Rubus idaeus) and blackberry (Rubus ssp. rubus), respectively. Research on the fate of applied 15N (a naturally occurring istope of N) has shown that primocanes rely primarily on fertilizer N for growth, whereas floricane growth is highly dependent on stored N in the over-wintering primocanes, crown, and roots; from 30% to 40% of stored N was allocated to new growth. Plants receiving higher rates of N fertilizer took up more N, often leading to higher N concentrations in the tissues, including the fruit. Reallocation of N from senescing floricanes and primocane leaves to canes, crown, and roots has been documented. Accumulation of other macro- and micronutrients in plant parts usually preceded growth. Primocanes generally contained the highest concentration of most nutrients during the growing season, except calcium (Ca), copper (Cu), and zinc (Zn), which often were more concentrated in roots. Roots typically contained the highest concentration of all nutrients during winter dormancy. Nutrient partitioning varied considerably among elements due to different nutrient concentrations and requirements in each raspberry and blackberry plant part. This difference not only affected the proportion of each nutrient allocated to plant parts, but also the relative amount of each nutrient lost or removed during harvest, leaf senescence, and pruning. Macro- and micronutrient concentrations are similar for raspberry and blackberry fruit, resulting in a similar quantity of nutrient removed with each ton of fruit at harvest; however, yield may differ among cultivars and production systems. Nutrient removal in harvested red raspberry and blackberry fruit ranged from 11 to 18 lb/acre N, 10 to 19 lb/acre potassium (K), 2 to 4 lb/acre phosphorus (P), 1 to 2 lb/acre Ca, and 1 to 4 lb/acre magnesium (Mg). Pruning senescing floricanes in August led to greater plant nutrient losses than pruning in autumn. Primocane leaf nutrient status is often used in nutrient management programs. Leaf nutrient concentrations differ with primocane leaf sampling time and cultivar. In Oregon, the present recommended sampling time of late July to early August is acceptable for floricane-fruiting raspberry and blackberry types, and primocane-fruiting raspberry, but not for primocane-fruiting blackberry, where sampling leaves on primocane branches during the green fruit stage is recommended. Presently published leaf tissue standards appear to be too high for K in primocane-fruiting raspberry and blackberry, which is not surprising since the primocanes are producing fruit at the time of sampling and fruit contain a substantial amount of K.