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Donald J. Merhaut, Eugene K. Blythe, Julie P. Newman, and Joseph P. Albano

1 To whom reprint requests should be addressed; e-mail donald.merhaut@ucr.edu . This research was funded in part by grants from the Hansen Trust Fund and the California Department of Food and Agriculture–Fertilizer and Research and Education

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Peter R. Hicklenton and Kenneth G. Cairns

Abbreviations: CRF, controlled-release fertilizers; EC, electrical conductance. Contribution no. 2083 of Agriculture Canada Research Station, Kentville. The cost of publishing this paper was defrayed in part by the payment of page charges. Under

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Allen D. Owings and Edward W. Bush

A study was initiated at Bracy's Nursery, Amite, La., in Apr. 1997 to evaluate the influence of seven controlled-release fertilizer sources and three top-dressed application rates in production of 4-gal (15.7-L) containers of `LaFeliciana' peach and swamp red maple. The fertilizers tested were Osmocote Plus 15-9-11, Osmocote Plus 16-8-12, Woodace 20-5-10, Woodace 20-4-11, Customblen 24-4-6, Nutricote (Type 270) 17-7-8, and Nutricote (Type 360) 17-6-8. Application rates were 1.75, 2.25, and 2.75 lb N per cubic yard. The experiment was completely randomized within blocks (species) and each treatment was replicated five times. A control treatment was also included. For `LaFeliciana' peach, Nutricote and Osmocote yielded the superior results when shoot height and visual quality ratings were determined in October (6 months after initiation). Increases in application rate did not significantly increase shoot height or visual quality ratings in most cases. For swamp red maple, shoot height was not affected by fertilizer source or application rate. Caliper ranged from 19.2 to 23.0 mm but was only slightly influenced by fertilizer source and application rate. Visual quality ratings were significantly higher for Osmocote Plus 16-8-12 when compared to some of the other fertilizer sources.

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Joseph P. Albano, Donald J. Merhaut, Eugene K. Blythe, and Julie P. Newman

Fertilizer and Research and Education Program (CDFA-FREP). Trade names are mentioned throughout this manuscript, but this does not imply product endorsement by the authors and their associated institutions. Special thanks are given to Shahram Ahmadian and

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Eugene K. Blythe, Donald J. Merhaut, Julie P. Newman, and Joseph P. Albano

1 To whom reprint requests should be addressed; e-mail donald.merhaut@ucr.edu . This research was funded in part by grants from the Hansen Trust Fund and the California Department of Food and Agriculture–Fertilizer and Research and

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Allen D. Owings, Warren A. Meadows, Donald L. Fuller, and Melinda R. Stewart

Recent studies at Louisiana State University evaluated incorporated rates (0.72, 1.08, and 1.44 kg N/m3) of controlled-release fertilizers (Chrysanthemum Mix 12N-4.4P-14.1K, Osmocote 14N-6.1P-11.6K, and Nutricote Type 70 14N-6.1P-11.6K) on vegetative growth and flowering of `Spears' potted chrysanthemums. Data collected included fresh and dry weight, height, width, flower size, flower number, days to first flower color, and days to flower finish.

Flower characteristics were not greatly affected by fertilizer or application rate. Dry weight increased with an increase in application rate from 0.72 kg N/m3 to 1.44 kg N/m3.

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Thomas B. Bruning, Michael H. Chaplin, and Henry G. Taber

Ground water contamination resulting from continuous liquid fertilization technologies is a serious problem facing greenhouse growers in the United States. Rooted Dendranthema grandiflora Tzvelev. cultivar 'Iridon' cuttings were transplanted into 11 cm pots filled with a 50% peatmoss and 50% perlite (v/v) media containing 0.10, 0.21, 0.42, or 0.84 g N from a controlled release 12-10-17 plus minors fertilizer deposited directly below the transplanted cutting. Pots were assigned to a top-water or subirrigation treatment.

Subirrigation reduced the nitrate leachate concentration by as much as 250 ppm as compared with top-watering. Fertilizer N rate linearly decreased plant height in both of the irrigation treatments. Final dry weight of the shoot peaked at the 0.21 g N rate in both the irrigation treatments.

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Allen D. Owings, Warren A. Meadows, Donald L. Fuller, and Melinda R. Stewart

Recent studies at Louisiana State University evaluated incorporated rates (0.72, 1.08, and 1.44 kg N/m3) of controlled-release fertilizers (Chrysanthemum Mix 12N-4.4P-14.1K, Osmocote 14N-6.1P-11.6K, and Nutricote Type 70 14N-6.1P-11.6K) on the foliar nutrient composition of `Spears' potted chrysanthemums. Recently mature leaf tissue was sampled at flowering and analyzed for N, P, K, Ca, Mg, Fe, Zn, Cu, and Mn.

Increasing application rates reduced Ca and M g content in leaf tissue, while N, P, and K increased with an increase in application rates. Chrysanthemum Mix 12N-4.4P-14.1K provided more K to leaf tissue than did Osmocote or Nutricote Type 70 14N-6.1P-11.6K.

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Darren L. Haver and Ursula K. Schuch

The objectives of this study were to determine 1) the minimum controlled-release fertilizer (CRF) rate and the lowest constant medium moisture required to produce the highest quality plants and 2) if this production system affected quality of these plants under two postproduction light levels. Two New Guinea impatiens (Impatiens sp. hybrids) `Illusion' and `Blazon' (Lasting Impressions Series) differing in salt tolerance were grown for 42 days with a CRF at three rates (3.3, 6.6, or 9.9 g/pot) and two medium moisture levels (low or high) without leaching. The high moisture level (tension setpoints of 1 to 3 kPa) and 6.6 g of CRF/pot produced optimum biomass. Low medium moisture (tension setpoints of 4 to 6 kPa) reduced leaf area, leaf number, leaf N content, root, stem, and leaf dry masses as CRF rate increased from low to high for `Illusion'. Similar results in `Blazon' were observed as CRF rates increased from 3.3 to 6.6 g. Biomass decreased no further at the high rate of 9.9 g/pot. Biomass increased in both cultivars under high medium moisture when CRF rates increased from 3.3 to 6.6 g. Biomass of `Illusion' decreased at 9.9 g/pot, although no symptoms of salt sensitivity were observed (i.e., leaf tip burn). `Blazon' maintained a similar biomass when amended with 9.9 or 6.6 g CRF/pot, although electrical conductivity (EC) in the medium was 5.9 dS·m-1 in the upper half and 4.1 dS·m-1 in the lower half of the medium at the end of production. Growth of `Illusion' responded more favorably to postproduction light levels that were similar to those of production regardless of treatment imposed during production. Similar biomass responses occurred for `Blazon' regardless of the postproduction light level.

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Peter Purvis, Calvin Chong, and Glen Lumis

Plug-rooted liners of common ninebark [Physocarpus opulifolius (L.) Maxim.] were grown in 6-L nursery containers filled with 73% composted pine bark, 22% sphagnum peat moss, and 5% pea gravel (by volume). Plants were fertilized with Polyon (Nutryon) 17–5–12 (17N–2P–5K) 6-month controlled-release fertilizer at various rates (2.5, 4.5, 6.5, and 8.5 kg·m-3) pre-incorporated, topdressed, or dibbled (placed under the liner at potting). Plants were trickle-irrigated daily with low (0.4-L), middle (0.8-L), or high (2.0-L) volumes of water to maintain leaching fractions of <0.15, 0.25–0.35, or >0.60, respectively. Regression analysis indicated that growth of ninebark increased from 30 to 109 g/plant with increasing rates of incorporated fertilizer (mean over irrigation volumes), from 27 to 71 g/plant with topdress and from 59 to 103 g/plant with dibble. Electrical conductivity (EC, mean over five dates) of the leachate throughout the season was highest with dibble (0.85 dS·m-3), intermediate with incorporated (0.81 dS·m-3), and least with topdressed (0.76 dS·m-3). With low irrigation volumes, growth of ninebark increased from 42 to 81 g/plant with increasing rates of fertilizer (mean over methods), and from 39 to 105 g/plant with middle or high volumes (common regression curve). With low irrigation volumes, leachate EC increased from 0.74 to 0.94 dS·m-3 with increasing rates of fertilizer, and from 0.75 to 0.81 dS·m-3 with middle or high volumes.