Progress 10/01/02 to 09/30/07
Outputs
OUTPUTS: Results of research have been provided in written form through an annual report to the blueberry industry through the lowbush blueberry advisory committee. Research findings have been reported to growers at annual spring lowbush blueberry meetings. A fact sheet entitled, Wild Blueberry Nutrition Series! Leaf and Soil Sampling Procedures was revised. Fertility management for organic production was presented at a special meeting with organic blueberry growers. Information was disseminated as oral presentations at national and international meetings of blueberry growers and researchers and as journal articles associated with those meetings.
PARTICIPANTS: The Wild Blueberry Commission has provided financial support and guidance throughout this period. Individual blueberry growers and blueberry companies have allowed research to be conducted on their land. Numerous undergraduate students have received training in establishing research plots applying treatments and collecting data,as they worked on these projects during summers and during the school year.
TARGET AUDIENCES: Lowbush growers have received basic information at annual spring blueberry meetings about plant nutrition and the value of soil and leaf sampling to determine the fertilizer needs of their blueberry field.
Impacts
Research findings have enabled growers to use leaf tissue analysis to guide fertility management. Results indicated that boron, zinc, iron and copper standards were too high and that fertilizing with these nutrient elements was not necessary for high blueberry productivity. Lowbush blueberry yields have increased with correction of nitrogen and phosphorus deficiency by the proper use of diammonium phosphate fertilizer.
Publications
- Smagula, J. M. 2006. Evaluation of Vaccinium angustifolium Ait. Cu and Fe leaf standards. Acta Horticulturae (in press).
- Smagula, J.M. and D. Yarborough. 2006. The lowbush blueberry, p. 177-181. In: N. F. Childers and P.M. Lyrene (ed.). Blueberries for growers, gardeners, promoters. Dr. Norman F. Childers Horticultural Publications, Gainesville, Florida.
- Smagula J. M., Q. Wang, and L. Kreider. 2007. Manganese accumulation in lowbush blueberry. Annual Meeting of the Northeast Region American Society for Horticultural Science. College Park, Maryland, Jan 4-6.
- Smagula J. M. and L. Kreider. 2007. Comparison of phosphoric acid and phosphite foliar sprays for lowbush blueberry. Annual conference of the American Society for Horticultural Science, Scottsdale, Arizona July 16-19.
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Progress 10/01/05 to 09/30/06
Outputs
Leaf Mn concentrations of lowbush blueberry are usually exceptionally high compared to other non-ericaceous plants, reaching 1200 ppm in some instances. In a commercial field with low leaf Mn concentration(less than 750 ppm), soil-applied Mn at 1 to 3 kg/ha failed to raise soil Mn levels or leaf Mn levels of 7 clones; yet leaf Mn levels varied from 550 to 1164 ppm among the clones, suggesting a genetic variation in absorption ability. A small but positive correlation (pearson correlation, r2 = 0.21 ) was found between clonal leaf Mn concentration and yield. Fruit Mn concentrations ranged from 60 to 136 ppm. The pearson correlation coefficient for clonal leaf Mn and fruit Mn was r2 = 0.74.
Impacts
Studies in which leaf boron concentrations were raised to above 24 ppm did not consistently improve growth and yield indicating that the leaf boron standard of 24 ppm is too high. Lowbush blueberries are a good source of dietary Mn, which has been shown to have health benefits. Several of the antioxidant enzymes are metalloenzymes, which contain trace minerals for which vegetables and fruit are significant sources. Mitochondrial superoxide dismutase is a manganese-containing enzyme.
Publications
- Smagula, J. M. 2006. Evaluation of the leaf Boron Standard for Vaccinium angustifolium Ait. Acta Horticulturae 741:365-370.
- Smagula, J. M. 2006. Effects of raising leaf Cu concentration on growth and yield of lowbush blueberry. Proceedings of 10th North American Blueberry Research & Extension Workers Conference, Tifton, GA,June 4-8, 2006.
- Smagula, J.M. 2006. Tissue culture propagation, p. 55-58. In: N. F. Childers and P.M. Lyrene (ed.). Blueberries for growers, gardeners, promoters. Dr. Norman F. Childers Horticultural Publications, Gainesville, Florida.
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Progress 10/01/04 to 09/30/05
Outputs
The Cu and Fe leaf standards for lowbush blueberry were tested in two experiments and found to be too high as reported by Trevett in 1972 (Cu,7 ppm; Fe, 50 ppm). Cu and Fe foliar treatments were effective in raising leaf nutrient concentrations of these elements. Combining the Cu and Fe in the same spray was more effective than either spray alone in raising leaf Cu and Fe concentrations. This was true for both prune- and crop-year applications. No benefits of raising either leaf Cu or Fe concentrations were found with regard to stem characteristics, such as length or branching, or potential yield (flower bud formation). Berry yield was not increased by prune-year, crop-year or prune plus crop-year applications of Cu and Fe.
Impacts
Growers will be advised not to apply fertilizers containing Cu or Fe if leaf samples indicate Cu is below the current 7 ppm standard or Fe is below the 50 ppm standard.
Publications
- Smagula, J.M. and Fastook, I.W. 2005. Effects of raising lowbush blueberry leaf Cu concentration on growth and yield. HortScience 40(4):1107
- Smagula, J.M. and Fastook, I.W. 2004. Effect of foliar copper and/or iron application on growth and yield of lowbush blueberry. HortScience 39(4):854.
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Progress 10/01/03 to 09/30/04
Outputs
We tested the accuracy of the Cu standard (7 ppm) reported by Trevett (1972) by raising leaf Cu concentrations in fields with concentrations below 7 ppm. Cu Keylate (Stoller Enterprises, Inc.) containing 5% Cu was applied to foliage in mid June at 0.5 lbCu/acre increments from 0.5 to 2 lbs Cu/acre. There was no growth or yield response to raising the leaf Cu concentration from 4 to 12 ppm in a 2001 study, but N and P were deficient and might have been limiting the response to Cu. The study was repeated in 2003 using a split plot design, with Cu treatments as main plots and diammonium phosphate treatments (400 lbs/acre) as subplots. N and P deficiencies were corrected, but raising leaf Cu concentrations from 3.2 to 7.5 ppm, had no effect on growth or yield. We conclude that the Cu standard is too high. In an attempt to raise leaf N in preparation for a comparison of prune- and crop-year fertilization, we tested CoRoN (28% N), a combination of polymethylene urea coupled
with fast-release, low-biuret urea, designed to act as a slow-release foliar fertilizer. When CoRoN was applied at 6 kg N/ha in a citrate/phosphate buffer at pH 5, 6, or 7, and compared to an unbuffered solution of pH 8, the lower pH solutions were not as effective at raising leaf N as the higher pH solutions. Uptake of N from CoRoN was not enhanced by adding it to a foliar spray containing Cu Keylate (5% Cu) and Fe Keylate (5% Fe), with or without ammonium sulfate (at 2.8 lbs/acre). Ammonium sulfate alone was not as effective as CoRoN in raising leaf N concentrations.
Impacts
Growers will be advised to apply monoammonium phosphate (MAP) or diammonium phosphate (DAP) to correct N and P deficiencies under conditions of adequate weed control.
Publications
- Smagula, J.M., W. Litten, and K. Loennecker. 2004. Diammonium phosphate application date affects Vaccinium angustifolium Ait. nutrient uptake and yield. Small Fruit Review 3:87-94.
- Smagula, J.M. and Litten, W. 2003. Can lowbush blueberry soil pH be too low?. Acta Horticulturae 626:317-322.
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Progress 10/01/02 to 09/30/03
Outputs
Foliar application of nutrients to lowbush blueberry fields has advantages over applications of granular fertilizer by conventional tractor spreaders, especially during the crop year. We have successfully raised leaf concentrations of Zn, B, Cu and Fe by foliar sprays with commercial products containing these elements. We attempted to raise leaf N and P in preparation for a comparison of prune year and crop year fertilization in N- and P-deficient fields. For N, a commercial product, N-SURE(28-0-0) (Plant Food Company, Inc. Cranbury, NJ), containing a slow-release nitrogen compound (72%) and urea was applied once in mid June at 3, 4, 5, or 6 qts/acre and compared to a control (no treatment) and preemergent application of DAP (18-46-0) at 400 lbs/acre. Foliar application of N-SURE at rates from 3 to 6 qts/acre did not raise leaf N concentrations as expected. DAP was effective in raising leaf N concentrations and increasing stem length and branching, even though leaf N
concentration was above the satisfactory level in controls. For P, a commercial product, Blueberry Foliar Special (Plant Food Company, Inc. Cranbury, NJ,) with a 4-13-15 analysis plus 10% sulfur was applied in mid June at 1,2, 3, or 4 qts/acre and compared to a control (no treatment) and to preemergent DAP (18-46-0) at 400 lbs/acre. A treatment of 3 qts/acre plus 5 qts/acre of N-SURE(28-0-0) was also included. The June foliar sprays of 4-13-15 or 4-13-15 plus N-SURE had no effect on leaf N or P concentrations, compared to the control; however, preemergent DAP application raised the leaf N and P concentration to above the N (1.6 %)and and P (1.25%)standards. We continue to test other products and adjuvants, timing, and frequency of applications that may improve effectiveness of foliar applications of N and P.
Impacts
Growers will be advised to apply monoammonium phosphate (MAP) or diammonium phosphate (DAP) to correct N and P deficiencies under conditions of adequate weed control.
Publications
- Smagula, J.M. and K. Loennecker. 2003. Can Cu Deficiency be limiting lowbush blueberry yields? HortScience 38:492.
- Smagula, J.M. and K. Loennecker. 2003. Evaluation of the leaf boron standards for Vaccinium angustifolium ait. HortScience 38:659.
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