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Suat Irmak, Dorota Z. Haman, Ayse Irmak, James W. Jones, Kenneth L. Campbell, and Thomas L. Crisman

Two colors (white and black) of a recently introduced irrigation-plant production system [multi-pot box system (MPBS)] for container-grown nurseries were researched and results were compared with those obtained from the sprinkler-irrigated conventional (control) system (CS). Experiments were carried out in summer and fall of 2001 in Gainesville, Fla. Plant growth [growth index (GI), growth rate (GR), and dry matter] and stress parameters [stomatal resistance (rs), crop water stress index (CWSI), plant water potential (PWP), and substrate temperature (ST)] were measured and analyzed for Viburnum odoratissimum (Ker-gawl). In both seasons, plants grown in the white MPBS had significantly higher GI and GR as compared to the plants in the black MPBS and CS. In summer, plants in the white MPBS reached marketable size about 17 days and 86 days earlier than those in the black MPBS and CS, respectively. In fall, they reached marketable size about 25 and 115 days earlier than those plants in the black MPBS and CS, respectively. Plants in the white and black MPBSs showed exponential growth rate in summer with plants in the white MPBS having significantly higher growth rate (greater slope) than the other two treatments. In both seasons, plants in the white MPBS produced the highest amount of dry matter. In general, plants in the white MPBS had lower rs values to vapor transport compared to the other two treatments, and the black MPBS treatment had lower rs values than the CS in both seasons. The CWSI values of the plants in both white and black MPBSs were significantly lower than the CS. In both seasons, ST in the black MPBS and CS exceeded the critical value of 40 °C several times. The ST of >40 °C is often reported to significantly reduce the plant growth and cause root death and/or injury for container-grown plants. Overall, the white MPBS provided a better environment for root development and plant growth under these experimental conditions. Results strongly suggest that there is a potential opportunity of using MPBS for irrigation and production of nursery plants. These important findings suggest that, in practice, producing nursery plants in a shorter period of time by using white MPBS will result in significant savings of energy, water, chemicals, and other inputs and thereby reducing the costs and increasing profits.

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Richard C. Beeson Jr

1996, plants of Viburnum odoratissimum Ker Gawl (viburnum) grown in 11.4-L black polyethylene containers (1600; Lerio Corp., Kississimee, FL) were transplanted into 26.6-L containers (B7; Lerio Corp.) at the University of Florida's Central Florida

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Suat Irmak, D.Z. Haman, A. Irmak, J.W. Jones, B. Tonkinson, D. Burch, T.H. Yeager, and C. Larsen

This research study evaluates the effectiveness of a recently introduced irrigation-plant production system, multipot box system (MPBS), for moderating root zone temperature (RZT) compared with the conventional nursery containers. The study also deals with the development, calibration, and validation of a series of models that can be used to predict maximum (max) and minimum (min) RZTs using commonly available input variables. The Viburnum odoratissimum (Ker.-gawl.) was used as the test plant. Models were calibrated in the fall growing season and validated during the summer. The RZT was used as the dependent variable while the max and min air temperatures (Tmax and Tmin) and/or incoming solar radiation (Rs) were used as independent variables. The color of the MPBS had an effect on plant growth. Plants grown in the white MPBS had higher growth indices, shoot and root dry weights, and number of stems as compared with the plants in the black MPBS or the conventional (control) system (CS). White MPBS maintained cooler RZTs than the max air temperature during both seasons. Also, white MPBS maintained cooler RZTs than the black MPBS and CS during the two seasons. In both seasons, water temperature in the black MPBS was higher than the temperature in the white MPBS contributing to the high RZTs in the black MPBS. The RZT of the black MPBS and CS exceeded the critical value (40 °C), which is cited in the literatures as negatively impacting root growth, water and nutrient uptake, leaf area, plant survival, root and shoot dry weights, water status, and photosynthesis. The RZT in the CS was above 45 °C for most of the summer season and plants were exposed to this extreme temperature for a few hours a day during most of the summer. The white MPBS provided a better environment and enhanced plant growth. For regions where ambient air temperature ranged from 2 to 41 °C, the white MPBS can provide adequate and effective RZT protection for plants grown in No. 1, 3.8-L standard black conventional containers. Predicted RZT values were well correlated with measured values in all systems. Rs did not have an effect on predicting RZTmax in the MPBS treatments. Wind speed did not contribute to predicting RZT in any production systems. The root mean square error between measured and predicted RZT was relatively low ranging from 0.9 to 2.8 °C. Models were able to explain at least 74% of the variability in RZTs using only Tmax, Tmin, and/or Rs. Models developed in this study should be applicable for estimating RZTs when similar management and cultural practices are present. Models of this study are practical, simple, and applicable to predict RZTs where ambient air temperature ranges from 1.9 to 40 °C. Model results should not be extrapolated beyond these limits.

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Richard C. Beeson*

ng production and in landscapes, woody plants are initially spaced apart to develop to desirable landscape quality. As plants grow and canopies begin to interact, canopies transform from individual isolated canopies to one large, closed canopy system. Changes in individual plant actual evapotranspiration (ETA) during the transitions between isolated and closed canopies are 30% on average. Such changes can have a substantial impact on supplemental irrigation requirements, both decreasing with closure and increasing with random removal of plants from a closed canopy. Data will be presented demonstrating changes in ETA as canopy closure progresses from isolated plants through 33%, 67%, and 100% canopy closure. Concurrent data from plants of marketable size grown in 3.8, 10.4, and 26.6 L containers were used to evaluate effects of canopy vertical thickness, and total canopy height, on the changes in ETA relative to degree of canopy closure. Contributions to ETA at 100% canopy closure and isolated plants from leaves at various depths within a canopy will be discussed.

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A.L. Shober, C. Wiese, G.C. Denny, C.D. Stanley, and B.K. Harbaugh

-sedge peat in container substrate on the growth and quality of walter's viburnum, sandankwa viburnum, and japanese privet and 2) assess the potential for N and P leaching from substrates during production by examining the nutrient content in leachate from

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S.M. Scheiber, E.F. Gilman, D.R. Sandrock, M. Paz, C. Wiese, and Meghan M. Brennan

hill manzanita ( Arctostaphylos densiflora ) and texas sage ( Leucophyllum frutescens )] and two introduced [vanhoutte spirea ( Spiraea vanhouteii ) and laurustinus ( Viburnum tinus )] species with neither native nor nonnative outperforming the other

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Amy L. Shober, Kimberly A. Moore, Nancy G. West, Christine Wiese, Gitta Hasing, Geoffrey Denny, and Gary W. Knox

sacrificing plant growth and quality. Materials and methods Plant materials and experimental design. Three ornamental shrub species (‘Alba’ indian hawthorn, sweet viburnum, and ‘RADrazz’ rose) were selected for evaluation across a range of N fertilization

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Bert M. Cregg and Robert Schutzki

paniculata ‘Tardiva’), Chicago Lustre® arrowwood viburnum ( Viburnum dentatum ‘Synnestvedt’), and cranberrybush viburnum ( Viburnum trilobum ‘Compactum’). One shrub of each taxa was planted in each plot except for ‘Golden Globe’ arborvitae and ‘Runyan’ yew

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Richard C. Beeson Jr.

Viburnum odoratissimum Ker Gawl (viburnum; Beeson, 2010b ). When data from the two species were combined, the correlation was 0.843. Both species are considered upright spreading shrubs ( DACS, 1994 ) and require the same production time of ≈12 months to

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Jeff B. Million and T.H. Yeager

irrigation water. On 4 Dec. 2013, 1280 rooted cuttings of sweet viburnum were transplanted by nursery staff into 10-inch-diameter containers (Classic 1000; Nursery Supplies ® , Kissimmee, FL) filled with a substrate mix comprised by volume of 5.5 pine bark:4