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R.C. Beeson Jr.

Three species of woody ornamentals, Viburnum odoratissimum Ker Gawl, Ligustrum japonicum Thunb., and Rhaphiolepis indica Lindl. were transplanted from 3.8-L into 11.4-L containers and grown for 6 months while irrigated with overhead sprinkler irrigation. Irrigation regimes imposed consisted of an 18-mm-daily control and irrigation to saturation based on 20%, 40%, 60%, and 80% deficits in plant available water [management allowed deficits (MAD)]. Based on different evaluation methods, recommendations of 20%, 20%, and 40% MAD are supported for V. odoratissimum, L. japonica, and R. indica, respectively, for commercial production. Comparisons of plant growth rates, supplied water, and conversion of transpiration to shoot biomass are discussed among irrigation regimes within each species. Comparisons of cumulative actual evapotranspiration (ETA) to either shoot dry mass or canopy volume were linear and highly correlated. Results indicated there were minimum cumulative ETA volumes required for plants to obtain a specific size. This suggests that irrigation regimes that restrict daily ETA will prolong production times and may increase supplemental irrigation requirements. Thus the hypothesis that restrictive irrigation regimes will reduce irrigation requirements to produce container plants is false due to the strong relationship between cumulative ETA and plant size.

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Gary R. Bachman and Ted Whitwell

Demand for commercially grown Uniola paniculata L. (southern seaoats) is increasing for use in restoring beaches damaged by tropical storms. Fresh seeds harvested from the Jekyll Island, Ga area (with permission of the Jekyll Island Authority), were planted in 50 peat: 50 perlite and treated with 100 or 500 ppm GA4 for 24 h. Germination was higher for 100 compared to 500 ppm GA4. Liners grown from seed and planted with the crowns even with the surface of the pine bark-sand media, compared to deep planting to simulate burial conditions of beach planting, had the highest shoot and root weights after 100 days. Uniola paniculata liners with the crowns buried had reduced weights due to higher moisture conditions in the bottom of the containers. Uniola paniculata grown without supplemental fertilization had shoot weights similar to those of plants receiving 1.5 lb N/yd3 (0.89 kg N/m3) from both quick or slow release fertilizers. Increasing N to 3 lb/yd3 (1.78 kg N/m3) and/or supplying micronutrients only, reduced shoot weight. Nursery production of Uniola paniculata in pine bark-sand is one way to increase the supply of this important dune plant.

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Ricky M. Bates, James C. Sellmer, Tracey L. Harpster, and Larry J. Kuhns

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D.M. Cole, J.L. Sibley, E.K. Blythe, D.J. Eakes, and K.M. Tilt

`Formosa' azalea (Rhododendron indicum) was grown for 4 months in 7.6-L (2 gal) containers in four substrate blends: 100% pine bark (PB) (by volume), 1 PB: 1 cotton gin compost (CGC), 3 PB: 1 CGC, and 3 PB: 1 peat (PT) at three irrigation levels [600, 1200, and 1800 mL·d-1 (20.3, 40.6, and 60.9 floz/d)] in a polyethylene-covered greenhouse. Plants were evaluated for growth on a biweekly basis using a growth index. Roots were evaluated visually at the end of the study using a 0 (no root growth) to 5 (root bound) scale. Initial physical properties were determined and leachates were collected every 30 days. There was no difference in percent increase in growth across irrigation and substrate treatments. Visual root rating was greatest (4.5) for azaleas grown in 3 PB: 1 PT and least (3.5) in 1 PB: 1 CGC. The two PB/CGC blends improved water-holding capacity (WHC) in comparison to 100% PB, with 1 PB: 1 CGC exhibiting the greatest WHC among all four substrates. Bulk density was greatest with the CGC-amended substrates. Leachate pH tended to increase and electrical conductivity (EC) tended to decrease with increasing irrigation volume. Leachates from the CGC-amended substrates were less acidic and EC tended to be similar or greater than leachates from the 100% PB and 3 PB: 1 PT substrates.

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Gisele Schoene, Thomas Yeager, and Dorota Haman

A survey was conducted of nursery operators participating in workshops in west-central Florida. The purpose of the survey was to identify the irrigation best management practices (BMPs) adopted by container nurseries in west-central Florida and obtain information regarding emphasis of future extension educational programs. Workshops were conducted in Hillsborough County, Fla., and Manatee County, Fla., and participation was voluntary. Respondents were asked about BMPs used in the nurseries according to the irrigation system used and it was found that the majority of the nurseries relied on well water as the primary source for irrigation. While 69% of the nurseries monitored uniformity of microirrigation systems, only 35% monitored uniformity of overhead irrigation systems. Thirty-four percent of the nurseries collected irrigation or rain runoff and 9% knew the water holding capacity of their substrate. Most of the nurseries grouped plants by irrigation requirements (74%) and grouped container sizes by irrigation requirements (69%). The survey indicates that many BMPs are not widely adopted by nurseries in west-central Florida. The information from this survey can be used as a guide to focus the efforts of university extension educational programs to achieve greater adoption of BMPs.

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Calvin Chong

The first weed disc (Weed Guard) was introduced to Ontario in the early 1980s. They were made of semirigid plastic similar to 45-rpm records. Small holes allow water to penetrate but weeds germinating on the substrate often grow through them. In the 1990s, we obtained 85% reduction of container weeds using discs made from geotextile fabric (Mori Guard) or foam (similar to polyfoam used for container winter protection). The foam disc tended to curl upward at the edges, become easily windblown, and tended to partially expose the surface of the container mix. During the past 15 years, we have annually reused the same fabric discs (now unavailable due to high unit cost), and have tested various other weed discs, including several new-generation types and also the Mori Weed Bag. The new-generation discs are fabricated from materials such as fabric (Tex-R Geodisc), pressed peat moss (Biodisc), corrugated cardboard (Corrudisc), and plastic (Enviro LID). Both Tex-R Geodisc and Enviro LID were as effective or better in controlling weeds than weekly hand-weeding, herbicides, or the Mori Guard fabric disc. The Mori Weed Bag, a patented black polyethylene sleeve with prepunched holes fitted around the container like a florist's plant prepared for market, is used effectively and almost exclusively by one Ontario nursery. We also tested two types of insulated blanket covers, which when placed around the ball of above-ground container-grown trees, prevented weed growth during the summer and also protected the root ball against cold during the winter. We introduced the garbage bag sleeve, the ultimate no-weed method for pot-in-pot tree culture, which also reduces water use and frequency of irrigation. Due to factors such as under-performance, insufficient demand, and/or high costs, only certain discs are currently manufactured: Weed Guard, Tex-R Geodisc, Biodisc, and Enviro LID. The Mori Weed Bag is available but not the insulated blankets.

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Hannah M. Mathers

Nursery growers estimate that they spend $500 to $4000/acre ($1235 to $9880/ha) of containers for manual removal of weeds, depending upon weed species being removed. Economic losses due to weed infestations have been estimated at about $7000/acre ($17,290/ha). Herbicide treated bark nuggets were found extremely effective for weed control in studies during 1998, regardless of whether oxyfluorfen, oryzalin, or isoxaben were applied to the bark. A study conducted in 2000 compared 24 treatments of novel nonchemical alternatives, conventional chemical practices and herbicide treated barks. Four of the best treatments were herbicide treated douglas fir bark, specifically, small [<1 inch (2.5 cm) length] douglas fir nuggets treated with oryzalin at the 1× rate, large (>1 inch length) douglas fir nuggets treated with oryzalin at the 0.5× rate, small douglas fir nuggets treated with oryzalin at the 0.5× rate and large douglas fir nuggets treated with flumioxazin at the 1× rate. The four bark treatments indicated above provided equivalent efficacy and phytotoxicity to Geodiscs. Penn Mulch and Wulpack provided poor weed control. Mori Weed Bag, a black polyethylene sleeve, and Enviro LIDs, a plastic lid provided less control than herbicide treated bark. Compared to the bark alone, herbicide treated bark provides a 1.8-fold increase in efficacy and a 2.8-fold extension in duration of efficacy. Compared to the herbicide alone, herbicide treated bark provides a 1.5-fold increase in efficacy and a 2.2-fold reduction in phytotoxicity. Of the innovative weed control products tested herbicide treated bark provided the most promising results. The data support that the bark nuggets are possibly acting as slow release carriers for the herbicides or reducing the leaching potential of the herbicides. Recent studies have indicated that the controlled release of herbicides using lignin as the matrix offers a promising alternative technology for weed control.

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Timothy K. Broschat

Five-gram (0.18 oz) samples of two controlled-release fertilizers (CRFs), Osmocote 15N–3.9P–10K (8–9 month) (OSM) and Nutricote 18N–2.6P–6.7K (type 180) (NUTR), were sealed into polypropylene mesh packets that were placed on the surface of a 5 pine bark: 4 sedge peat: 1 sand (by volume) potting substrate (PS), buried 10 cm (3.9 inches) deep below the surface of PS, buried 10 cm below the surface of saturated silica sand (SS), or in a container of deionized water only. Containers with PS received 120 mL (4.1 floz) of deionized water three times per week, but the containers with SS or water only had no drainage and were sealed to prevent evaporation. Samples were removed after 2, 5, or 7 months of incubation at 23 °C (73.4 °F) and fertilizer prills were crushed, extracted with water, and analyzed for ammonium-nitrogen (NH4-N), nitrate-nitrogen (NO3-N), phosphorus (P), and potassium (K). Release rates of NO3-N were slightly faster than those of NH4-N and both N ions were released from both products much more rapidly than P or K. After 7 months, OSM prills retained only 8% of their NO3-N, 11% of their NH4-N, 25% of their K, and 46% of their P when averaged across all treatments. Nutricote prills retained 21% of their NO3-N, 28% of their NH4-N, 51% of their K, and 65% of their P. Release of all nutrients from both fertilizers was slowest when applied to the surface of PS, while both products released most rapidly in water only. Release rates in water only exceeded those in SS, presumably due to lower rates of mass flow in SS.

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Marta Pardos, Rafael Calama, Gregorio Montero, and José A. Pardos

Four concentrations of paclobutrazol (PBZ) and two application methods (foliar spray–soil drench) were tested on 3-month-old container-grown cork oak (Quercus suber L.) seedlings. Shoot height was affected by PBZ concentration and application technique. Time course of height was modelled by nonlinear mixed model analysis. Reduced shoot height was the result of shortened and fewer internodes. A 25 to 625 ppm soil drench or 625 to 15,000 ppm foliar spray controlled over vegetative growth, resulting in a reduction between 13% and 90% in plant size relative to untreated controls. Seedlings responded to soil drench at a lower PBZ concentration than for a foliar spray, but the danger of irreversible overdosing seems greater for a soil drench. Soil drench—and foliar spray to a lesser extent—also affected other shoot and root growth traits. PBZ dose decreased root volume and dry weights in a quadratic fashion with increasing dose, but decreased diameter and number of leaves linearly.

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John M. Ruter

A study was conducted with Coreopsis verticillata L. `Moonbeam' and Plumbago auriculata Lam. to evaluate the growth of these perennial plants in 2.6-liter (#1) black plastic containers (BPCs) compared to plants grown in fiber containers with Cu(OH)2 (FCs+) impregnated into the container walls. Coreopsis root and shoot dry weight was unaffected by container type, whereas Plumbago root and shoot dry weight was greater (2.2× and 1.6×, respectively) for plants grown in FCs+ compared to BPCs. The root : shoot ratio of Plumbago increased 30% when plants were grown in FCs+ compared to BPCs. Root circling was effectively controlled for both species grown in the FCs+. FCs remained in salable condition for the duration of the study. In contrast to untreated FCs, FCs+ will have to be removed at transplanting to allow for normal root development.