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Multiple branched liners of llex vomitoria were greenhouse-grown in 3-liter containers with a common nursery medium and received either 2.5 g N surface-applied in 1 application as Osmocote (18N-2.6P-10K) or a total of 0, 0.5, 1,5 or 2.5 g N per container from a solution that contained N, P and K in a ratio of 6:1:3. The solution fertilizer was applied either 1, 2, 3 or 4 times per week with total N applied per container equally divided among individual applications, After 26 weeks, shoot dry weights were greatest for plants that received 2.5 g of N as either 2 soluble applications per week or as Osmocote applied once at the beginning of the experiment. Plants that received 1.5 g of N applied 4 times per week had similar shoot dry weights. Nitrogen uptake will be calculated to determine if 4 applications par week resulted in greater utilization than 2 applications par week or 1 application of Osmocote during the growing season.

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Multiple branched liners of `Mrs. G. G. Gerbing' azaleas (Rhododendron L.) were greenhouse-grown for 16 weeks in 3-liter containers with a common nursery medium. The growth medium of each plant was amended with either 0.5, 1.5, or 2.5 g N from Osmocote 14N-6P-11.6K and irrigated with either 920 ml water twice a week or evapo-transpiration (ET) plus 10%, 30%, or 50%. Shoot dry weights (35 and 35 g, respectively) for plants irrigated with ET plus 30% or 50% and fertilized with 1.5 g of N were larger than plants fertilized with 0.5 or 2.5 g N and irrigated with ET plus 10%, 30%, or 50%. Shoot dry weights of plants irrigated with ET plus 30% or 50% were similar to plants irrigated with 920 ml twice a week when plants received 1.5 g N. Plants that received 920 ml twice a week and 2.5 g N had larger shoot dry weights than plants irrigated with ET plus 10%, 30%, or 50% and fertilized with 2.5 g N. Shoot dry weights increased from 17 to 46 g for the 0.5 and 2.5 g N treatments, respectively, when plants were irrigated with 920 ml.

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Nursery operations have strategically positioned themselves close to markets and many are now an agricultural entity surrounded by urban encroachment. The environmental pressures of society have mounted at unprecedented rates, resulting in additional regulations for nurseries. Development and implementation of Best Management Practices (BMPs) for the nursery industry allows nurseries to be proactive and not wait for regulations that might harm the industry. Univ. extension personnel with BMP subject matter expertise can play a pivotal role in assisting the industry with development and implementation of proactive BMPs. Important steps that have served as a model for BMP development and implementation include the following. Establish need—the industry leadership must explain to nursery personnel the reasons why BMPs are needed and elicit assistance with BMP development from university personnel. Committee guidance—the industry leadership establishes a steering committee of nursery personnel representing various interests of the industry to work with university and regulatory personnel to conceptualize BMPs and develop objectives. Consensus development—steering committee communicates their objectives to the nursery industry, explains the impacts, and provides a mechanism for feedback to achieve broad-based stakeholder participation. BMPs drafted - steering committee writes a draft BMP manual that is available for industry review. Industry-wide input—steering committee aggressively seeks input from the industry, implements as many suggestions as possible, and informs industry of BMP manual revisions. Educational programs—university extension personnel conduct training for nursery operators implementing BMPs and track the impact of BMPs on nurseries.

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Multiple branched liners of Ilex vomitoria Ait. `Nana' were greenhouse-grown in 3-L containers with a 2 pine bark: 1 Canadian peat: 1 sand substrate. Plants were fertilized weekly with a solution of 50 N, 10 P, and 30 K (mg·L–1) for either 5, 10, or 15 weeks. Then plants for each of the three fertilizer durations were fertilized weekly with a solution of either 50, 150 or 300 N, 10 P, and 30 K (mg·L 1) for an additional 15 weeks, at which time root and shoot dry weights were determined. A control group of plants was fertilized weekly with 300 N (mg·L–1) for 30 weeks. Shoot dry weight increased linearly as fertilizer rate or duration of fertilization increased. Root dry weights increased linearly as fertilizer duration increased while root dry weights were not different due to fertilizer rate. These data indicate that duration of fertilization is important in promoting root and shoot growth; however, the largest amount of root and shoot dry weight resulted from the highest N application rate (300 mg·L–1) for the longest duration (30 weeks).

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Ligustrum japonicum, Rhododendron indica `Southern Charm' and Viburnum odoratissimum in 10-L containers were placed in a square grid pattern and overhead irrigated using impact sprinklers (30.3 L/min). Plants were irrigated with 12.5 mm with containers touching and, at 5 cm spacings, up to 50 cm between containers. Irrigation water reaching container surfaces (percent capture) increased for all species as container spacing increased. However, the increase in percent capture did not increase irrigation application efficiency because the percent of production area covered by the containers declined as spacing increased. Application efficiency declined with each increase in spacing to a low of 7%. The effects of intraand inter-canopy interference are discussed.

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Multiple branched liners of Rhododendron sp. cv. Duc de Rohan were potted in 3-L containers using a 5 pine bark: 5 Florida peat: 1 sand medium (by volume) amended with Prokote Plus (20N–1.3P–8.3K, 9.2 kg·m–3) and placed on one of five treatment platforms (1.2 × 2.4 m) in a commercial nursery in Manatee County, Fla. Treatments were 88 plants per square grid with containers touching (T1), 44 plants per square grid with containers touching (T2), 44 plants per square grid with containers touching in rows and 15 cm between rows (T3), 22 plants per square grid with containers touching (T4), and 22 plants per square grid with 15 cm between containers in rows and 15 cm between rows (T5). Irrigation was applied by overhead impact nozzles (0.13 cm/0.5 h) before collecting runoff. Runoff volume was measured and ppm nitrate N determined on day 6, 23, 38, 63, 92, 161, 189, 217, and 274. Average nitrate N ranged from 97 ppm for T1 to 10 ppm for T5 and corresponded to volumes of 19 and 20 L, respectively. Volumes were not different due to spacing or number of containers; however, nitrate N increased linearly with container number when containers were touching (T1, T2, and T4). Nitrate N in runoff was similar for the same number of containers regardless of spacing.

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In crop models, it is important to determine the leaf area, because the amount of light interception by leaves influences two very important processes in the plant: photosynthesis and evaporation. Leaf area is dependent on leaf appearance and expansion rates. Leaf appearance rate is driven mainly by temperature. Although the influence of temperature on leaf area development is well known for several agronomic crops, there is no information for woody ornamentals. An experiment was conducted to study the relationship between temperature and leaf appearance of container-grown sweet viburnum. Plants were grown in field conditions in Gainesville, Fla., during two growing periods (Apr. to Aug. 2004 and Aug. 2004 to Jan. 2005). Daily maximum and minimum temperature and leaf appearance were recorded. Linear regression equations were fitted to data and maximum and minimum temperature and leaf appearance were recorded. Linear regression equations were fitted to data and base temperature was assumed to be 8 °C. Thermal time (°C d) was calculated as daily average maximum and minimum air temperature minus the base temperature and was regressed against leaf number. The sum of accumulated thermal time was found to be linearly correlated with leaf number. Phyllochron, which is the thermal time between the appearances of successive leaves, was estimated 51 °C per day. The information presented in this study will be useful in modeling water use of sweet viburnum in response to environmental conditions.

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The capacity for container-grown plants to capture sprinkler irrigation water plays a critical role in adjusting irrigation rates to deliver required amounts of water to the container substrate. The capture factor (CF) used to describe this capacity was defined as the amount of water captured with a plant relative to the amount captured without a plant. A wind-sheltered, irrigation test area was established to measure CF as affected by plant species, plant size, container size, container spacing, and sprinkler type. CF values for 11 marketable-sized, commonly grown plant species ranged from 1 to 4 with highest values exhibited by plant species with an upright, spreading growth habit. CF values increased as plant size increased. Close container spacings (less than one container diameter between adjacent containers) reduced CF when the allotted area outside the container limited the potential amount of water that could be captured. Compared with impact sprinklers, wobbler sprinklers increased irrigation capture 7% for Ligustrum japonicum grown in 27-cm-diameter containers but not in 16-cm-diameter containers. Results showed that CF is a dynamic parameter that depends on canopy size, container size, container spacing, and sprinkler type. A working knowledge of CF is crucial for determining irrigation requirements to maximize sprinkler irrigation efficiency in container nurseries.

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Two experiments were conducted to determine if a leaching fraction (LF)-guided irrigation practice with fixed irrigation run times between LF tests (LF_FX) could be improved by making additional adjustments to irrigation run times based on real-time weather information, including rain, using an evapotranspiration-based irrigation scheduling program for container production (LF_ET). The effect of the two irrigation practices on plant growth and water use was tested at three target LF values (10%, 20%, and 40%). For both Viburnum odoratissimum (Expt. 1) and Podocarpus macrophyllus (Expt. 2) grown in 36-cm-diameter containers with spray-stake microirrigation, the change in plant size was unaffected by irrigation treatments. LF_ET reduced water use by 10% compared with LF_FX in Expt. 2 but had no effect (P < 0.05) on water use in Expt. 1. Decreasing the target LF from 40% to 20% reduced water use 28% in both experiments and this effect was similar for both irrigation practices. For the irrigation system and irrigation schedule used in these experiments, we concluded that an LF-guided irrigation schedule with a target LF of 10% resulted in plant growth similar to one with a target LF of 40% and that the addition of a real-time weather adjustment to irrigation run times provided little or no improvement in water conservation compared with a periodic adjustment based solely on LF testing.

Open Access

Abstract

A 2 pine bark : 1 moss peat: 1 sand (by volume) medium (11% volumetric, 20% gravimetric moisture) amended with 4.2 kg m −3 of dolomitic limestone and 3 kg m−3 of 32P-, 35S-superphosphate (8.7% P, 11.7% S) was incubated (25°C) for either 0, 15, or 30 days. Columns (4 × 15 cm) of the medium for each incubation time received 48 ml of deionized water (pH 5.5) in 3 hr on day 1 and 16 ml in 1 hr on days 2-21. Forty-six and 21% of 32P and 35S, respectively, leached on day 1 when the medium was not incubated. Thirty-one percent and 28% of the 32P and 14% and 13% of the 35S leached on day 1 if the medium had been incubated 15 or 30 days, respectively. Eighty-two percent of the 32P and 66% of the 35S amendment leached from the unincubated medium during the 3 week experimental period. A similar leaching experiment, but with superphosphate in absorbent cotton instead of the soilless medium, indicates superphosphate dissolves readily.

Open Access