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  • Author or Editor: Timothy J. Smalley x
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Commonly used planting techniques and soil amendments were compared to determine their effect on root growth, shoot growth, and drought tolerance of 2.5 cm caliper Acer rubrum. Study I: Trees were planted on 6 April 1992 into holes backfilled with 1) native soil, 2) 50% aged pine bark: 50% native soil, 3) 50% Mr. Natural™:50% native soil, or 4) 100% Mr. Natural™. Mr. Natural™ consists of granite sand, expanded shale, and composted poultry litter. After two years, no differences in growth or survival existed. Study II: On 8 April 1992, trees were planted in 1) unamended planting holes, 2) tilled planting beds, or 3) tilled and pine bark-amended planting beds. Five months after planting, the root growth in the tilled and tilled-amended beds did not differ, but both had more root growth than planting holes. Amendment-induced nitrogen deficiency reduced shoot growth of the tilled-amended treatment during the first year. After two years, the planting hole treatment exhibited the least shoot growth, while shoot growth of tilled and tilled-amended treatments did not differ. StudyIII: Selected trees in study II were drought stressed for 8 weeks beginning 4 August 1993. No differences in relative leaf water content among treatments were observed Results suggest that native soil should be used as backfill in planting holes; however, tilling a planting bed increases root and shoot growth compared to planting in a hole. Amending beds with pine bark did not increase growth or drought tolerance.

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The Industry Liaison Committee of the American Society for Horticultural Science conducted a survey of the horticulture industry to systematically determine: 1) industry's perception of university training of recent graduates and 2) industry's perception of educational needs for future graduates. A Delphi survey was sent to experts in the fruit, ornamental, greenhouse, turf, and vegetable industry. The respondents expressed dissatisfaction with the level of competence of recent university graduates in personnel management and marketing. The lack of hands-on training in university courses was viewed as a major problem, but the respondents agreed that internships should provide university students with the necessary practical experience and universities should concentrate on the science of horticulture. The respondents indicated that business management and marketing expertise will be more important in the future than knowledge of production techniques; however, they would not be more likely to hire a business major instead of a horticulture major. The following areas of study were ranked for relative importance to be included in the university curriculum (from most important to least): communication skills, horticultural technology, business management, personnel management, plant nutrition and soil fertility, pest control, plant physiology, environmental awareness, plant physiology, plant pathology, accounting, and equipment use and maintenance. A second round of questioning for this Delphi survey is being conducted and results will be presented to verify preliminary results.

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Abstract

Acer rubrum L. ‘October Glory’ cuttings taken on 15 June 1984 were subjected to short-day (SDT) or short-day plus night interruption treatments (NIT) from 25 July until 22 Oct. 1984. Additional cuttings taken on 14 Aug. were subjected to the same photoperiod treatments from 10 Sept. until 22 Oct. The height of the 15 June NIT cuttings was 50 cm greater than that of the 15 June SDT cuttings at the start of the first growing season, but no significant difference in height or caliper existed after two growing seasons of container culture. The greater growth rate of the 15 June SDT cuttings compared to 15 June NIT cuttings is attributed to their greater percentage of root carbohydrate reserves at the start of the first growing season. The initial root carbohydrate reserves and the final height and caliper of the SDT and NIT 14 Aug. cuttings were not significantly different. The 14 Aug. cutting growth results approached those of the 15 June cuttings. This indicated the growth potential of cuttings taken later in the season.

Open Access

This study determined the effect of soil amendments on plant available water (PAW) and readily available water (RAW). Intact soil cores were collected from a Cecil sandy clay loam soil landscape planting beds that had been amended annually for 5 years with 5 cm (25% by volume) of pine bark and broiler litter. Soil cores were also collected from a landscape bed that had been amended once in April 2000 with 5 cm (25% by volume) of Permatill (expanded slate). The results of this study indicated that amending soil with pine bark or broiler litter compost increased soil porosity, drainage, aeration and PAW. The volumetric RAW (cm3·cm-3) did not differ among treatments, but amending the soil with pine bark or broiler litter did increase the gravimetric RAW (g·g-1). Permatill increased drainage and aeration, but did not increase available water to plants.

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This experiment compared the effect of fall fertilization on freeze hardiness of evergreen vs. deciduous azaleas (Rhododendron). Beginning in Spring 2003, a 2 × 3 factorial experiment was conducted in Athens, Ga., on container plants grown outdoors under nursery conditions involving two taxa (R. canescens and R. ×satsuki `Wakaebisu') and three fall fertigation regimes (Aug.–Sept., 75 mg·L-1 of N; Aug.–Nov., 75 mg·L-1 of N; and Aug.–Nov., 125 mg·L-1 of N). On 15 Nov. and 17 Dec. 2003 and 16 Jan., 18 Feb., and 19 Mar. 2004, plant stem tissue was harvested and exposed to 10 progressively lower temperature intervals between –3 °C and –30 °C under laboratory conditions in order to estimate azalea freeze hardiness. Freeze hardiness was affected by fertilizer and taxa treatments, but there were no significant interaction effects in this study. The timing of freeze hardening was not significantly different among the two species over time, and the fall fertilizer treatments did not affect the timing of hardening. Compared to the industry standard (75 mg·L-1 of N, Aug.–Sept.), R. canescens that received extended fertilization at the high rate (125 mg·L-1 of N, Aug.–Nov.) was less freeze hardy in November, December, and January, and R. ×satsuki was less freeze hardy in December. However, when compared to the industry standard, the low rate of extended fertilization (75 mg·L-1 of N, Aug.–Nov.) did not affect azalea freeze hardiness.

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Three biostmulants, Grow-plex (Menefee Mining Corp., Dallas, Texas), Roots 2 (LISA Product Corp., Independence, Mo.), and Root n' Shoot (Natural Organic Products International, Mount Dora, Fla.) were applied to transplanted plugs of Salvia splendens `Empire Red' and Begonia semperflorens-cultorum `Varsity Pink' and `Varsity Brite Scarlet'. Root n' Shoot drench (0.78%) solutions at transplant increased root weight, but a 1.56% solution decreased root weight of salvia; however, shoot growth was unaffected. Root n' Shoot decreased shoot growth of begonia, but did not affect root growth of begonia. Roots 2 treatments (0.25% or 2.00%) increased shoot weight of salvia, but did not affect salvia root growth or root or shoot growth of begonia. Spraying Grow-plex (0.78% or 1.56%) to runoff at transplanting and 2 weeks after transplanting did not affect root or shoot growth of salvia or begonia.

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Three biostimulants, Grow-plex (Menefee Mining Corp., Dallas), Roots 2 (LISA Product Corp., Independence, Mo.), and Root n' Shoot (Natural Organic Products International, Mount Dora, Fla.) were applied to transplanted plugs of Salvia splendens `Empire Red' and Begonia semperflorens `Varsity Pink' and `Varsity Brite Scarlet'. Root n' Shoot drench (0.78%) solutions at transplant increased root weight, but a 1.56% solution decreased root weight of Salvia, although shoot growth was unaffected. Root n' Shoot decreased shoot growth of Begonia, but did not affect root growth. Roots 2 treatments (0.25% or 2.00%) increased shoot weight of Salvia, but did not affect the root growth of Salvia or the root or shoot growth of Begonia. Spraying Grow-plex (0.78% or 1.56%) to runoff at transplanting and 2 weeks after transplanting did not affect root or shoot growth of Salvia or Begonia.

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Container-grown Viburnum plicatum var. tomentosum `Mariesii' were planted in tilled beds and tilled beds amended with aged pine bark. After transplanting, plants were fertilized at three different rates: no fertilizer, 18.4 g of N m-2, and 36.8 g of N m-2. A 31 day drought was begun 73 days after planting. Fertilization of tilled plots induced ammonium toxicity, which caused a linear reduction in leaf area, shoot dry weight, and root dry weight. Fertilization of amended plots had no effect on shoot growth but reduced mot growth by 54%; thus, amendments ameliorated ammonium toxicity. Between 10 and 28 days after beginning the drought, plants in unfertilized-amended plots maintained higher relative leaf water contents (RLWC) and relative leaf expansion rates (RLER) than plants in unfertilized-tilled plots. Amendment induced nitrogen deficiencies contributed to the increased drought tolerance of plants from unfertilized-amended plots. Since fertilized plants developed symptoms of ammonium toxicity, we were unable to determine if increasing fertility would counteract the drought tolerance conferred by pine bark soil amendments.

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Isolite is a ceramic-like, porous soil amendment purported to sustain plant growth under reduced irrigation and increase plant survival during drought. The purpose of this greenhouse experiment was to determine the effect of an Isotite-amended soilless container medium on: (1) growth under reduced irrigation frequency and (2) water stress during drought of Impatiens × hybrids `Accent Red'. On 2 June 1993, seedlings were transplanted into 13.2 liter black plastic pots containing a 4:1 composted pine bark:coarse sand (vol.) medium amended with Isolite CG-1 granules at rates of 0%, 10%, 15%, and 20% (vol.). Study I. Seedlings were. irrigated with 500 ml tap water every two days for two weeks followed by a 4 week schedule of 500 ml tap water every 1, 2, 3, 4, or 5 days. In general, growth parameters were explained by irrigation treatment effects and did not differ with Isolite rate. Growth indices ranged from +54% to + 143%, while final visual quality grades ranged from 2.4 to 5.0 (5-point scale), shoot dry weight from 8.7 to 30.7 g, root dry weight from 2.0 to 7.9 g, and leaf area from 0.14 to 0.48 m2. Study II. Seedlings were irrigated with 500 ml tap water every 2 days for rive weeks followed by a two week drought. Plant water status parameters were similar at all rates of Isolite. Leaf expansion rates ranged from + 89% to +98%, white a final mid-day xylem pressure potential of -0.4 MPa and a final visual quality grade of 2.0 were uniform across all treatments. Under these conditions, Isolite did not limit water stress of container-grown Impatiens `Accent Red'.

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Abstract

Acer rubrum L. ‘October Glory’ cuttings taken on 15 June 1984 were subjected to short day (SDT) (800-1700 HR) or short day plus night interruption treatments (NIT) (800-1700 plus 2200-200 HR) from 25 July until 22 Oct. 1984. Additional cuttings taken on 14 Aug. were subjected to the same photoperiod treatments from 10 Sept, until 22 Oct. For the 15 June cuttings, the NIT treatment induced significantly greater percent budbreak than the SDT, but did not induce significantly greater overwinter survival. Cuttings of 15 June that broke bud under NIT had significantly greater stem length and dry weight than cuttings that broke bud under SDT. SDT and NIT cuttings of 15 June that broke bud had significantly greater percent root carbohydrates, total grams of carbohydrates, and percent overwinter survival then cuttings that did not break bud. For the 14 Aug. cuttings, 1% of the cuttings broke bud, yet 95% (SDT) and 90% (NIT) of the cuttings survived the winter, and no difference in cutting carbohydrate levels, except stem starch, existed between the two treatments.

Open Access