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In a commercial lowbush blueberry (Vaccinium angustifolium Ait.) field with low leaf Cu (<7 ppm) and Fe (<50 ppm) concentrations, nine 1.8 m × 15 m treatment plots were established in a randomized complete block design with 6 blocks. Copper Keylate® (Stoller Enterprises, Inc.) containing 5% Cu was used as a foliar spray in a volume of 626 L·ha-1. In a similar volume, the Stoller Enterprises Inc. product Fe Keylate®, containing 5% Fe (5% chelated Iron), was used to provide Fe. Ammonium sulfate (0.7%) was added to the solutions to enhance uptake. Treatment plots received either Cu Keylate® at 0.6 kg·ha-1 Cu or Fe Keylate® at 0.6 kg·ha-1 or a combination of both nutrients in one spray. Treatments included a 19 June prune - or crop-year application of Cu, Fe, or Cu + Fe, and a prune-year Cu + Fe June 7 and June 19. A plot receiving no treatment served as a control. Leaf Cu and Fe concentrations were raised to above satisfactory leaf concentrations (Cu >7 ppm, Fe >50 ppm) by their respective treatments. Concentrations were significantly higher for each element when they were applied together. Two applications were not better than only one. No carry-over effect was seen in the crop year. Crop-year applications of Cu and Fe were effective in raising their respective concentrations. Stem density, length, number of branches or branch length was not affected by treatments at the end of the prune year. Flower bud density and average number of flower buds per stem were not meaningfully affected by prune year Cu or Fe treatments. Berry yield was not influenced by any treatment suggesting that the Cu and Fe standards are too high.
Concentrations of nutrient elements in randomly selected soil samples taken at a 3-inch depth or the depth of the surface organic pad correlated poorly (R2= < 0.34) with leaf nutrient concentrations randomly selected from the same fields. Average leaf N concentrations in 74 of 79 fields sampled were above the 1.6% standard, while leaf P was below the 0.125% standard in 62 of the 79 fields. Leaf K, Ca, and Mg concentrations were above the standards 0.400%, 0.270%, and 0.130%, respectively in all fields. The average depth of the organic pad was 2.23 cm, ranging from 0 to 10.16 cm. Seventy five percent of the fields had organic pads 0.127-2.54 cm thick and 20% greater than 2.54 cm.
In an attempt to improve correlations, leaves within a 0.01M2 quadrat were sampled from 110 clones in 10 commercial blueberry fields and leaf nutrient concentrations compared with nutrient concentrations in 3-inch soil samples taken directly beneath the quadrat. The strongest correlation was between soil Mn and leaf Mn (r2= o.59). Leaf samples, although more expensive than soil samples, appear to be a better indicator of lowbush blueberry fertilizer requirements than soil samples.
Liquid phosphorus (23% phosphoric acid) was applied preemergence at 0, 22.4, 44.8, 67.2, or 89.6 kg·ha-1 to 9 fields: 3 commercial blueberry fields having plants with very low (<.111%), 3 low (.111-.125%), and 3 adequate (>.125%) leaf phosphorus concentrations. Years of application ('89,'89+'91,'89 + '91 + '93) were assigned in a split-block RCB design with 4 replications at each location. A linear increase in leaf phosphorus concentration with increasing rates of P application was found in both 1989 and 1991. Differences in response were found among locations. A second application in 1991 was effective in raising leaf P levels at most locations to higher levels than the application in 1989. Also, there were higher levels of leaf P in treatment plots that only received P fertilizer in 1989 compared to controls, indicating a carry over effect.
Nodal segments containing one axillary bud (1 to 1.5 cm) were disinfected using 10% bleach and were established on a Murashige and Skoog (MS) medium without hormones at 27 °C and with a 16-h photoperiod. The sprouted shoots (≈1.0 cm) were cultured on a MS medium supplemented with 6-benzylaminopurine (BAP), kinetin (KIN), or zeatin (ZT) at 2.3, 4.5, 9.1, or 18.2 μM. After 38 d, ZT and BAP significantly induced multiple shoot formation with multiplication rates of 4 to 6, whereas the multiplication rate of KIN was less than 2. Shoots cultured on ZT grew significantly taller than those on BAP and KIN. The height of the longest shoots treated with ZT was 4.6 cm, which was 1.6 to 2.2 times greater than those treated with BAP or KIN. To induce rooting, shoots (≈2 cm) were subcultured on one-fourth strength MS (1/4 MS) medium containing either 3-indolebutyric acid (IBA) or 1-naphthylacetic acid (NAA) at 2.6, 5.1, or 10.3 μM. Adventitious roots formed in vitro after 2 to 4 weeks. IBA at 10.3 μM produced the best rooting (100%) compared with other treatments after 38 d of culture. The average number of roots per shoot for IBA was ≈15, which was 1.6 to 3.1 times as many as that of other treatments. All rooted plantlets were then transplanted into a mix of peatmoss and perlite (1:1 v/v) and acclimatized in a mist system. Average plantlet survival was 73.6% after 35 d. After acclimatization, they were grown in a pot with Metro-mix under greenhouse conditions for 10 weeks where 95% of plants survived and grew up to 6.8 cm high. The micropropagation procedure, i.e., nodal segments containing one axillary bud proliferated on MS with 4.5 μM ZT followed by in vitro rooting on 1/4 MS plus 10.3 μM IBA, could be used for commercial mass production of new inkberry cultivars.
Four organic fertilizers were evaluated in a commercial lowbush blueberry field with a history of N and P deficiency. In nonorganic production, diammonium phosphate (DAP) is the standard fertilizer for correcting N and P deficiency. Nitrogen a rate of 67 kg·ha-1 [Renaissance (8-2-6), ProHolly (4-6-4), Pro Grow (5-3-4), Nutri-Wave (4-1-2), or DAP (18-46-0)] was applied preemergent to 1.8-m × 15-m treatment plots. Leaf N and P were deficient (<1.6% and 0.125%, for N and P, respectively) in the unfertilized plots that served as controls. DAP and Pro-Holly raised leaf N to satisfactory levels (>1.6%). Only DAP raised leaf P concentrations (0.144%), compared to controls (0.122%). Leaf K was not deficient, but was raised by Pro-Holly. Soil pH was slightly lowered by Renaissance (4.2) and raised by Pro-Holly (4.4), compared to the control (4.3). Soil P concentrations were raised by DAP and soil S by Pro-Holly. Soil K was raised by all fertilizers except DAP, compared to the control. Pro-Holly and DAP were equally effective in increasing stem height, branching, branch length, flower bud formation, and yield, compared to the control and the other organic fertilizers. Pro-Holly could effectively substitute for DAP in organic wild blueberry production.
Acommercial lowbush blueberry field with a history of N and P deficiency was used to study the response to several organic fertilizers. Diammonium phosphate (DAP) is the standard fertilizer for correcting N and P deficiencyin non-organic production. At a rate of 67 kg N/ha Rennaisance (8–2–6), Pro-Holly (4–6–4), Pro Grow (5–3–4), Nutri-Wave (4–1–2), or DAP (18–46–0) was applied preemergent to 1.8 × 15 m treatment plots. An unfertilized plot served as the control. Leaf N and P were deficient in the controls. DAP and Pro-Holly raised leaf N to satisfactory levels (1.6%). Only DAP raised leaf P concentrations (0.144%), compared to controls (0.122%). Leaf K was not deficient but was raised by Pro-Holly. Pro-Holly and DAP were equally effective in increasing stem height, branching, branch length, flower bud formation, and yield. Pro-Holly could effectively substitute for DAP in organic wild blueberry production.
Two experiments evaluated the Trevett (1972) Cu standard of 7 ppm by raising leaf Cu concentrations in a commercial blueberry field having low (∼4 ppm) leaf Cu concentrations. A foliar spray of Cu Keylate (5% Cu) (Stoller Enterprises, Inc.) in a volume of 627 L·ha-1 applied 0, 0.56 1.12, 1.68, or 2.24 kg·ha-1 of Cu. Ammonium sulfate at 3.1 kg·ha-1 was added to the solutions to enhance Cu absorption. A preemergent soil application of Micromate Calcium Fortified Mix (Stoller Enterprises, Inc.), a micronutrient mixture containing Cu (0.3%), was also tested at 14 kg·ha-1. These 6 treatments were replicated 7 times in a randomized complete-block design in 2001. Treatments were reapplied in 2003 in a split-plot design with Cu treatments as the main plots and an application of DAP at 448 kg·ha-1 as the split plots. In 2001, leaf Cu concentrations increased linearly, up to 12 ppm, with increasing rates of Cu, but Micromate had no effect. Leaf N and P concentrations were below the standards of 1.6% and 0.125%, respectively, and could explain why raising leaf Cu concentrations had no effect on growth or yield. In 2003, DAP corrected the N and P deficiency and leaf Cu concentrations were raised to above the 7 ppm standard with 2.24 kg·ha-1 of Cu, but again, no effect on growth or yield was found. The Cu standard appears to be too high.
Foliar sprays of B (400 ppm), Ca (4000 ppm), B (400 ppm) + Ca (4000 ppm), or water (control) were applied in Sept. 1993 to treatment plots of 12 lowbush blueberry (Vaccinium angustifolium) clones having low leaf B concentrations (<20 ppm). Boron concentration was raised in stem and bud tissue 3 months after application, but Ca concentration was unaffected. Twenty randomly selected stems with four flower buds were tagged in each treatment plot in Apr. 1994 to determine treatment effects on fruit set and fruit characteristics. Blossoms on tagged stems were counted in late May and a count of initial fruit was taken in early July. Initial fruit set was reduced slightly by the Ca treatment, which also resulted in a lower number of flowers per bud. Tagged stems were cut before plot harvest and stored at –15C for final fruit set and fruit characteristic measurements (fruit number, diameter, weight, and firmness, and seed number and size). Treated plots were harvested and weighed in August. Boron and Ca treatments did not increase yields averaged across all clones, but some clones showed a positive response. Yield of Ca-treated plots was significantly lower than the plots without Ca treatment. Effect of treatments on final fruit set and fruit characteristics will be presented.
Ten clones of lowbush blueberry (Vaccinium angustifolium) having low leaf boron (B) concentrations (<20 ppm) were selected to receive fall foliar B (400 ppm), Ca (4000 ppm), B (400 ppm) + Ca (4000 ppm), or water (control). B concentration was raised in stem and bud tissue 3 months after application, but Ca concentration was unaffected. Two randomly selected 5-inch sod plugs from treatment plots within each clone were transported to cold storage at 2.7C for 1000 h to satisfy flower bud dormancy, then to a growth chamber at 24C to blossom. Pollen from plants receiving B had lower in vitro germination rates on 5% agar with 12% lactose after 20 h compared to control and Ca treatments. For in vivo germination, 10 blossoms were randomly selected on sod plugs of each treatment plot to receive 15 control-treatment pollen grains, which were allowed to germinate for 3 days. With the aid of fluorescence microscopy, a higher pollen germination percentage was observed in blossoms of plants receiving B, Ca, and B + Ca. B and Ca may have more influence on the ability of the stigma to stimulate pollen germination than on the germinability of pollen grains themselves.
Flail mowing was compared to traditional pruning by oil fire over a 12-year period in two fertility experiments testing interactions with pruning method. In study one (1983–1986), urea at 0, 22.4, 44.8, 67.2, or 89.6 kg·ha–1 was applied preemergent in a split-block design with fertility as the main effect, and pruning method split within six blocks. Study two (1987–1994) continued the pruning and application of fertilizer on the treatment plots with similar rates, but diammonium phosphate (DAP) replaced urea as the fertilizer. Leaf tissue N concentrations were above the 1.6% standard and urea had no effect or decreased yield. There was no interaction of fertility and pruning and no effect of pruning method on yield. No interaction of fertility and pruning was found in study two, but DAP increased leaf P concentrations and yield and, after three cycles of mowing, yields had begun to decline in mowed plots compared to burned plots. No meaningful differences in leaf nutrient concentrations were found between plants in mowed and burned plots.