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John Smagula* and Ilse Fastook

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.

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John M. Smagula and Ilse Fastook

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.

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John M. Smagula and Ilse W. Fastook

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.

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John M. Smagula and Ilse W. Fastook

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.