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Khin San Wai and Steven E. Newman

Growth chamber studies using elevated root-zone temperatures and greenhouse studies using two root-zone and two night air temperatures were conducted to determine the effects on growth and flowering of two response groups [`Rainier White' (Group II) and `Tampico' (Group III)] of cut-flower snapdragons (Antirrhinum majus L.). Chamber-grown snapdragons with the root zone at 30C had shorter stems and a lower dry weight than those at 20C. Holding the root zone above 26C increased time to flower. Greenhouse-grown `Tampico' and `Rainier White' snapdragon stems were longer with increased root-zone temperature regardless of night air temperature. Time to flower was reduced an average of 6 days with increased root-zone temperature and 12 days when the night air was maintained at 20C. This study demonstrated that the effects of relatively low greenhouse temperatures may be offset by root-zone heat.

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Michael J. Roll and Steven E. Newman

The rooting efficiency of cuttings from three poinsettia cultivars were evaluated after regulating the photoperiod during the stock plant stage. `Freedom Red', `Monet', and `V-17 Angelika Marble' stock plants were exposed to an extended photoperiod and to natural day length during September 1995. `Freedom Red' cuttings rooted more quickly under an extended photoperiod compared to those under natural day length. Furthermore, root dry weight from these cuttings was greater than cuttings from stock plants grown under natural day length. `Monet' cuttings also rooted more quickly when the stock plants were under an extended photoperiod, and showed similar differences in root weight as `Freedom Red'. Cuttings from `V-17 Angelika Marble' were not influenced by photoperiod. Lighting stock plants to block flower initiation produces a higher quality cutting when propagation takes place after the critical day length for flowering has passed.

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Jesse R. Quarrels and Steven E. Newman

Greenhouse studies of cut flower snapdragons (Antirrhinum majus L.) using two night air and two root-zone temperatures were conducted to determine the effects on growth and quality of four cultivars in two response groups [`Cheyenne' and `Rainier White' (group II) and `Tampico' and `Potomac' (group III)]. The group II cultivars were the earliest to harvest, but at the expense of quality. Grades of first, extra, and fancy only were harvested. Group III cultivars were harvested with all grades; first, extra, fancy and special. Group II cultivars generally had weaker stems and were of lower dry weight. Night air temperature had the greatest effect on days to harvest. Harvest date was reduced more than 14 days, but at the expense of quality and dry weight. Root-zone heating decreased quality of the group II cultivars at either night air temperature. but reduced quality of the group Ill cultivars only at high night temperatures. Root-zone heat and high night air temperature reduced the number of days to harvest, also at the expense of quality. The majority of high quality stems were from group Ill cultivars harvested from rooms with low night temperatures without root-zone heat.

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Steven E. Newman and Jesse R. Quarrels

Many nurseries are using the pot-in-pot (PNP) system to grow trees in containers. This system protects the roots from temperature extremes and prevents tipping. PNP is not without problems, trees with vigorous roots may escape the container and root into the external soil making harvest difficult. PNP has no effect on root circling. Our objective was to determine if a polypropylene fabric disk treated with either trifluralin or copper placed in the bottom of a container would prevent root circling. Cercis canadensis and Quercus shumardii seedlings were grown in 19 liter polyethylene containers with eight root control treatments, which included trifluralin or copper impregnated polypropylene fabric disks placed in the bottom of the containers. Ttifluralin treatments, BioBarrier and trifluralin impregnated fabric, had few roots in the bottom of the containers. Of the copper treatments, Spinout® impregnated fabric was the only copper treatment that had any effect on root development in the bottom of the containers.

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Shelly D. Dueitt and Steven E. Newman

Rice hulls, a by-product of the rice milling process, were used at various rates to substitute sphagnum peat moss in greenhouse media. Previous studies demonstrated that media containing rice hulls replacing the vermiculite fraction grew plants equal to or better than traditional peat vermiculite blends. The objective of this study was to determine if rice hulls can replace sphagnum peat moss in a greenhouse medium. Physical properties, including bulk density, total pore space, and water retention were determined in media blended with fresh or aged rice hulls, sphagnum peat moss, and vermiculite. The bulk density of the media increased with increasing levels of fresh rice hulls. The pore space in media containing both fresh and aged rice hulls decreased over time during the crop production cycle and the pH increased.

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Steven E. Newman' and Jesse R. Quarrels

The objective of this study was to determine the influence of uniconazole and calcium applied as a drench or foliar spray to `Gutbier V-14 Glory' poinsettias'. Uniconazole was drenched into half of the plants at 6 mg/pot. Calcium was applied weekly as either a spray, drench, or a combination of both at 350 ppm Ca. Uniconazole reduced plant height, bract dry weight, and plant dry weight. Bract dry weight from plants not treated with uniconazole and received calcium as a spray was less than from those plants that received either no supplemental calcium or calcium as a drench. Calcium improved the appearance of plants treated with uniconazole.

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Steven E. Newman and Jeffrey S. Tant

An experiment was conducted to determine the influence of eight commercial root-zone media (four peat based and four pine bark based) on the effects of paclobutrazol applied to Euphorbia pulcherrima Willd. `Eckespoint Celebrate 2' as an impregnated spike or a drench. Paclobutrazol treatments had the least influence on stem elongation of poinsettias grown in the peat-based medium containing Bacctite, a compressed peat product designed to increase aeration and cation exchange capacity, or composted pine bark ground to a particle size that could pass through an opening 1 cm or smaller. Spikes were more effective at reducing shoot elongation than drenches. Spike treatments also resulted in lower bract dry-matter accumulation than drenches. Paclobutrazol applied as a spike to poinsettias at pinch could combine pinching and chemical growth regulator application into one simultaneous operation. Chemical name used: (±)-(R*,R*)-beta-[(4-chlorophenyl)methyl]-alpha-(1, 1,-dimethyl)-1H-1,2,4,-triazole-1-ethanol (paclobutrazol).

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C. Elizabeth Succop and Steven E. Newman

Fresh-market sweet basil (Ocimum basilicum) is in high demand from specialty produce markets and commercial restauranteurs. Many consumers are also demanding produce that has been organically grown. Three hydroponic media systems were evaluated twice over two years, rockwool slabs, perlite frames, and commercial sphagnum peat/perlite/compost medium, where the bag was laid flat on the bench. Plants grown in these systems were fertilized with nutrient solutions derived from either organic or conventional, saltbased fertilizer sources. Few differences in yield were detected between basil plants grown in the commercial medium with either fertilizer source. Total yield from plants grown in perlite with the organic fertilizer was 22% greater in the first study and 100% greater in the second study than those for plants grown with the conventional fertilizer. Plants grown in rockwool with the conventional fertilizer were 17% more productive in the first study and 46% more productive in the second study than those grown with the organic fertilizer. Taste test panelists (69%) could discern differences between samples from organically and conventionally grown basil plants, yet no preferences were shown.

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Shelly D. Dueitt and Steven E. Newman

Rice hulls, a by-product of rice milling, were used at various rates in greenhouse media. The objective of this study was to determine if rice hulls can replace peat moss. Hulls, aged and fresh, were blended with vermiculite and peat moss from 0 to 50%, by volume replacing peat moss. Physical and chemical properties including bulk density, total pore space, water retention, pH and soluble salt concentrations were determined in the media blends. Marigolds and salvia were transplanted into 13 cm azalea pots containing each media. The bulk density increased with increasing levels of hulls. Total pore space of the media before planting was decreased with increasing levels of aged hulls, but no differences were detected at the termination of the study. Water retention of both fresh and aged hulls at all levels of media were equivalent to the control media. Before planting, the total soluble salts for media containing fresh hulls was greater than with aged hulls. The pH of the media increased with increasing levels of hulls, fresh and aged. The greatest dry weight and plant height was observed when the media contained 10 to 20% aged hulls.

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Steven E. Newman* and Robert O. Miller

Greenhouse and nursery managers rely on testing laboratories with the expectations of accuracy and consistency. The Greenhouse and Nursery Media Analysis Proficiency (GNMAP) Testing program was initiated to provide laboratories servicing greenhouses and nurseries with inter-laboratory quality control. The GNMAP program operational guidelines are based on those outlined under ISO 9000, ISO/IEC Guide 43 and Draft ISO/IEC Guide 24, which describe the requirements for proficiency testing. Nine laboratories enrolled in the program in 2003 and submitted results for root zone media and fertilizer solutions. Data analysis provided the minimum, maximum and median values; median absolute deviation (MAD); overall reproducibility (Rd); individual reported lab values; repeatability (Rp) of lab value (CV for the individual lab); and mean lab value reported. The Rd was calculated from the median of all lab Rp values and is a measure of intra-lab variance. A measure of inter-lab variance was determined by calculating the relative median deviations (RMD = MAD/Median × 100). For one of the media distributed, results for the saturated media extract included median pH values from 4.3 to 6.9 with MAD values averaging 0.1 across the three samples. The electrical conductivity (EC) median values ranged from 0.36 to 4.57 dS/m with RMD averaging 31% of the median. The main variability between laboratories for the majority of the macro cations was closely aligned with measured EC. Cations (K, CA and Mg) concentrations ranged from 17 to 502 mg/L with Ca typically in the greatest concentration. Cation inter-lab precision, based on the RMD ranged from 9-32% across the three substrate samples. The greatest RMD was 31.8% for Ca and 9.2% for K. The Rd values for the cations averaged 5%.