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Amy L. Shober, Kimberly A. Moore, Gitta S. Hasing, Christine Wiese, Geoffrey C. Denny, and Gary W. Knox

. However, in central Florida annual N applications of 3 to 4 lb/1000 ft 2 N produced acceptable quality plants with ratings of 3 or better in most cases although increasing N fertilization rate did produce higher quality vine and groundcover plants for

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Wagner Vendrame, Kimberly K. Moore, and Timothy K. Broschat

New guinea impatiens (Impatiens hawkeri) (NGI) `Pure Beauty Rose' (PBR) and `Paradise Orchid' (PO) were grown in full sun, 55% shade, or 73% shade and fertilized with a controlled-release fertilizer (CRF) [Nutricote Total 13-13-13 (13N-5.7P-10.8K), type 100] incorporated at rates of 2, 4, 6, 8, 12, 16, 20, 24, 28 and 32 lb/yard3 of growing media (1.2, 2.4, 3.6, 4.7, 7.1, 9.5, 11.9, 14.2, 16.6, and 19.0 kg·m-3). Plant quality rating, shoot dry weight, and flower number were measured at harvest and substrate samples were collected to analyze final substrate pH and electrical conductivity (EC). For both cultivars, light intensity and fertilization rate interactions were different for shoot dry weight and flower number, but there was no difference in plant quality rating between the light levels. Quality ratings of both PBR and PO plants increased as CRF rate increased to 12 to 16 lb/yard3 above these levels quality was not improved. Shoot dry weight of PBR plants grown in full sun increased as CRF rate increased to 28 lb/yard3 and then decreased, while shoot dry weight of plants grown with 55% and 73% shade increased as CRF rate increased to 20 and 16 lb/yard3, respectively, with no further increases. Shoot dry weight of PO plants grown in full sun and 55% shade increased as CRF rate increased to 28 and 24 lb/yard3, respectively, with no further increases, while shoot dry weight of plants grown with 73% shade increased as CRF rate increased to 24 lb/yard3 and then decreased. Flower number of PBR plants grown in full sun, 55% shade, and 73% shade increased as CRF rate increased to 24 lb/yard3 and then decreased. Flower number of PO plants grown in full sun increased as CRF rate increased to 28 lb/yard3 and then decreased, while flower number of plants grown in 55% and 73% shade increased as CRF rate increased to 24 lb/yard3 and then decreased.

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Walter F. Ray, Geno A. Picchioni, Dawn M. VanLeeuwen, and Ryan M. Goss

heights and two fertilization rates under southern New Mexico conditions. Our intent was to focus on main and interactive effects of cultivar, mowing height, and fertilization rate during individual seasons of spring, summer, and fall. Materials and

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A.D. Brede

A field study was conducted to evaluate the effect of tall fescue (Festuca arundinacea Schreb.) cultivar, seeding rate, N fertilization rate, and cutting height on the severity of dollar spot (Lanzia and Moellerodiscus spp.) disease incidence. All possible two-factor interactions among these four management factors were statistically significant when averaged over the 2 years of study. Disease severity tended to be lowest at low fescue seeding rate (2100 pure-live seeds/m*) at the lower (19 mm) height of cut. `Mustang', the turf-type cultivar with improved density, was more susceptible to dollar spot than `Kentucky-31', the common-type cultivar.

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Timothy K. Broschat

Five species of tropical ornamental plants—artillery fern (Pilea serpyllacea), pleomele (Dracaena reflexa), fishtail palm (Caryota mitis), areca palm (Dypsis lutescens), and sunshine palm (Veitchia mcdanielsii)—were grown in containers under full sun, 55% shade, or 73% shade. They were fertilized every 6 months with Osmocote Plus 15-9-12 (15N-4P-10K) at rates of 3, 6, 12, 18, 24, 30, and 36 g/pot (0.1, 0.2, 0.4, 0.6, 0.8, 1.1, and 1.3 oz/pot). For pleomele and the three palm species, optimum shoot dry weights and color ratings were similar among the three light intensities tested. However, artillery fern grown in full sun required fertilizer rates at least 50% higher for optimum shoot dry weight and color than under 55% or 73% shade. Light intensit × fertilizer rate interactions were highly significant for pilea and fishtail palm color and dry weight and sunshine palm and pleomele color.

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Khalid Al-Redhaiman and John M. Swiader

The objective of this study was to investigate the effect of solution \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}concentration (Ns), in a recirculating hydroponic system, on the accumulation and partitioning of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}and reduced N, and its relationship to root and leaf nitrate reductase activity (NRA), in five lettuce (Lactuca sativa L.) cultivars differing in \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}accumulation capacity. Significant interactions between Ns and genotype influenced \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}accumulation, reduced N levels, and NRA in roots and leaves. In two cultivars, leaf \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}concentrations increased with increasing Ns up to 5.0 mM, and then leveled off, while in three other cultivars, leaf \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}levels increased linearly with increasing Ns rate up to 15.0 mM. NRA in leaves was generally highest at 5.0 mM Ns, and tended to decrease at 15.0 mM Ns. In roots, NRA increased with increasing Ns rate up to 1.0 mM, and remained relatively constant as Ns increased to 5.0 and 15.0 mM. In each cultivar, in situ \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}reduction (estimated by the relative concentrations of tissue reduced N to total N) decreased in both roots and shoots as Ns increased. The results suggested that genotypic variation in \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}accumulation in response to increasing Ns was not exclusively a result of cultivar differences in \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}uptake and reduction capacity, but may also involve other factors in relation to \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}accumulation.

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Jorge Arboleya, Claudio Garcia, and Carlos Suarez

National Research Inst. of Agriculture of Uruguay defined garlic as an important crop because its potential for exportation. Plant population and N management have been studied since 1992. Plant population of 112, 250, 333 and 500 thousand plants/ha at rates of N at 0, 75, 150 and 225 kg·ha–1 were tested in 1992, 1993, and 1995. Drip irrigation and plastic mulch with populations from 240 to 960 thousand plants/ha in 1992 and from 236 to 586 plants/ha in 1993 were evaluated. Nitrogen rates of 0, 40, 80 and 120 kg/ha, and application times were also tested with a population of 250 thousand plants/ha, in 1992 and 1993. Plant population of 240, 320 and 560 thousand plants/ha yielded 12,0; 12,4 and 14,2 t·ha–1 respectively. As plant population increased, bulb size decreased. Yield increased up to rate of N at 150 kg·ha–1.

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Bielinski M. Santos and Jose P. Morales-Payan

The effect of varying calcium (Ca), magnesium (Mg), boron (B), and molybdenum (Mo) rates on the growth of young `Cartagena Ombligua' papaya (Carica papaya) plants was studied in experiments conducted in the Dominican Republic. Rates of 0, 3, 6, 9, and 12 g Ca; 0, 0.85, 1.7, 2.55, and 3.4 g Mg; 0, 20, 40, 60, and 80 mg B; and 0, 0.05 0.1,0.15 and 0.2 mg Mo per plant were applied to the soil 20 days after transplanting. Ca did not stimulate plant growth, but instead was toxic at rates of 9-12 g per plant. Mg fertilization significantly stimulated root growth (Y = 2.35 + 0.48X, r 2 = 0.95), but not shoot growth. Mo applications decreased plant growth, whereas B enhanced overall plant growth (Y = 10.64 + 70.5X, r 2 = 0.96).

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Laura Guazzelli, Frederick S. Davies, and James J. Ferguson

Our objectives were to determine if leaf N concentration in citrus nursery trees affected subsequent growth responses to fertilization for the first 2 years after planting and how N fertilizer rate affected soil nitrate-N concentration. `Hamlin' orange [Citrus sinensis (L.) Osb.] trees on `Swingle' citrumelo rootstock [C. paradisi Macf. × P. trifoliata (L.) Raf.] were purchased from commercial nurseries and grown in the greenhouse at differing N rates. Three to five months later trees were separated into three groups (low, medium, high) based on leaf N concentration and planted in the field in Oct. 1992 (Expt. 1) or Apr. 1993 (Expt. 2). Trees were fertilized with granular material (8N–2.6P–6.6K) with N at 0 to 0.34 kg/tree yearly. Soil nitrate-N levels were also determined in Expt. 2. Preplant leaf N concentration in the nursery varied from 1.4% to 4.1% but had no effect on trunk diameter, height, shoot growth, and number or dry weight in year 1 (Expt. 1) or years 1 and 2 (Expt. 2) in the field. Similarly, N fertilizer rate had no effect on growth during year 1 in the field. However, trunk diameter increased with increasing N rate in year 2 and reached a maximum with N at 0.17 kg/tree yearly. Shoot number during the second growth flush in year 2 was much lower for nonfertilized vs. fertilized trees. Leaf N concentrations increased during the season for trees with initially low levels even for trees receiving low fertilizer rates. Soil nitrate-N levels were highest at the 0.34-kg rate, and lowest at the 0.11-kg rate. Nitrate-N levels decreased rapidly in the root zone within 2 to 3 weeks of fertilizing.

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Laura Guazzelli, Frederick S. Davies, and James J. Ferguson

Our objectives were to determine the effects of leaf N concentration in citrus nursery trees on subsequent growth responses to fertilization for the first 2 years after planting and the impact of N fertilizer rate on soil NO3-N concentration. `Hamlin' orange [Citrus sinensis (L.) Osb.] trees on `Swingle' citrumelo rootstock [C. paradisi Macf. × P. trifoliata (L.) Raf.] were purchased from commercial nurseries in Apr. 1992 (Expt. 1) and Jan. 1993 (Expt. 2) and were grown in the greenhouse at differing N rates. Five months later, trees for each experiment were separated into three groups (low, medium, and high) based on leaf N concentration and were planted in the field in Oct. 1992 (Expt. 1) or Apr. 1993 (Expt. 2). Trees were fertilized with granular material (8N-2.6P-6.6K-2Mg-0.2Mn-0.12Cu-0.27Zn-1.78Fe) with N at 0, 0.11, 0.17, 0.23, 0.28, or 0.34 kg/tree per year. Soil NO3-N levels were determined at 0- to 15- and 16- to 30-cm depths for the 0.11-, 0.23-, and 0.34-kg rates over the first two seasons in Expt. 2. Preplant leaf N concentration in the nursery varied from 1.4% (Expt. 1) to 4.1% (Expt. 2) but had no effect on trunk diameter, height, shoot growth and number, or dry weight in year 1 (Expt. 1) or years 1 and 2 (Expt. 2) in the field. Similarly, fertilizer rate in the field had no effect on growth during year 1 in the field. However, trunk diameter increased with increasing N rate in year 2 and reached a maximum with N at 0.17 kg/tree per year but decreased at higher rates. Shoot number during the second growth flush in year 2 was much lower for nonfertilized vs. fertilized trees at all rates, which had similar shoot numbers. Nevertheless, leaf N concentrations increased during the season for trees with initially low levels, even for trees receiving low fertilizer rates. This suggests translocation of N from other organs to leaves. Soil NO3-N levels were highest for the 0.34-kg rate and lowest at the 0.11-kg rate. Within 2 to 3 weeks of fertilizing, NO3-N levels decreased rapidly in the root zone.