Environmental concerns with nitrogen and phosphorus use at container nurseries and the subsequent effects of nutrient-laden irrigation effluent prompted this study. Bare root liners of willow oak (Quercus phellos L.) and sweetbay magnolia (Magnolia virginiana L.) were grown in #5 containers during year one and repotted into #15 containers during year two using 100% pine bark or pine bark: peat substrate (4:1 by volume). Two fertilizer sources, Osmocote 19N–2.2P–7.5K (19–5–9) or Harrell's 17N–2.2P–10.0K (17-5-12), were included in the container substrate in a fluoropolymer bag with 17 g N in each #5 container and 63 g N in each #15 container. Using a split plot design with fertilizer and media as subplots, a cyclic irrigation regime consisting of three irrigation applications spaced one hour apart was compared to a traditional irrigation regime with one irrigation application that equaled the total volume applied in the cyclic regime. Fertilizer source influenced cumulative amounts (mg/year) of ammonium-N, nitrate-N and orthophosphate in the container leachate. Nitrate-N and ammonium-N from Harrell's 17N–2.2P–10.0K fertilizer were each ≈20% higher in the container leachate from sweetbay magnolia than Osmocote 19N-2.2P-7.5K fertilizer. In the case of the willow oak, the differences were 32% and 19%, respectively. Orthophosphate averaged about 65% greater in leachate from both sweetbay magnolia and willow oak containers when grown with Osmocote compared to Harrell's fertilizer. At the end of year two, height and caliper growth were similar among treatments with both species.
Donna C. Fare
Yellow-flowering magnolias (Magnolia sp.) were evaluated for flower color, bloom duration, and growth rate in U.S. Department Agriculture (USDA), Hardiness Zone 6b, McMinnville, TN. Of the 30 cultivars evaluated, all were reported to have yellow blooms; however, tepal color ranged from light pink with some yellow coloration, creamy yellow to dark yellow. ‘Daphne’, ‘Judy Zuk’, and ‘Yellow Bird’ had the highest yellow color readings on the outside of the tepal and would often be among the latest cultivars to bloom. Magnolia cultivars Gold Star, Golden Gala, Stellar Acclaim, Sun Spire, and Sundance had the lightest yellow tepal color on the outside of the tepal. ‘Goldfinch’, ‘Butterflies’, and ‘Elizabeth’ were the earliest to bloom; ‘Elizabeth’ had one of the longest flowering periods. ‘Carlos’ and ‘Gold Star’ were two of the tallest cultivars in the test compared with Butterflies, Gold Cup, Golden Gift, Golden Pond, Golden Rain, Green Bee, Honey Liz, Koban Dori, Skyland’s Best, and Sunsation, which had the least height growth. Trunk diameters ranged from 7.4 to 18.4 cm after 9 years in the evaluation. Cultivars Golden Gala and Gold Star had trunk diameters greater than twice the size of Golden Pond, Golden Rain, Green Bee, Honey Liz, and Koban Dori. Powdery mildew (Phyllactinia corylea and Microsphaera alni) was observed on all cultivars; however, Golden Sun, Green Bee, Solar Flair, Stellar Acclaim, Sunburst, and Yellow Bird had greater than 47% of the leaf area affected with powdery mildew. Over 60% of the canopy was affected with powdery mildew on ‘Green Bee’, ‘Stellar Acclaim’, ‘Sunburst’, and ‘Yellow Bird’. Powdery mildew was less than 20% on both the foliage and plant canopy of ‘Banana Split’, ‘Butterflies’, ‘Carlos’, ‘Elizabeth’, and ‘Sun Spire’.
Donna C. Fare and W. Edgar Davis
One component of container production influencing the water quality concerns in the nursery industry is the amount of container effluent leaching from the container substrate. Potential exists for reduced water use, less leachate volume, and improved irrigation efficiency by altering the container design. This research compares the container leachate volume from a standard, 11.31 (# 3) container with seven 1.9-cm-diameter drainage holes to containers with one, three, or five holes with diameters of 1.9, 0.9, and 0.5 cm. Leachate volume was 41% less (312 to 182 mL) when the diameter of the drainage hole was reduced from 1.9 to 0.5 cm. Nitrate-N was 85% less (3093 to 452 mg) when the container drainage holes were reduced to 0.5 cm. Plant growth and quality of Lagerstroemia fauriei X L. indica `Hopi', crapemyrtle, was similar in all container modifications.
Donna C. Fare, Charles H. Gilliam, and Gary J. Keever
Efficient usage of current water supplies is of great concern to container-nursery producers. Improving water management first requires knowledge of current commercial container production practices. In this study, irrigation distribution from overhead sprinklers was monitored at container nurseries to determine the distribution and the amount of irrigation applied during a typical irrigation cycle. Several nurseries surveyed had poorly designed irrigation systems; subsequently, irrigation distribution varied widely at sampling dates and within the growing-container block. Uniform distribution was achieved at some nurseries, but required careful monitoring of the irrigation system. Future water restrictions may force nurseries to improve water usage by changing irrigation delivery methods to minimize water use, resulting in reduced surface runoff and effluent from container nurseries.
Charles H. Gilliam, Donna C. Fare, and Gary J. Keever
Little information is available on herbicide movement in soilless container media and subsequent movement in container leachate and container bed runoff. The objective of this study was to evaluate oxyfluorfen movement in irrigation water following application to container grown nursery crops in a commercial nursery. Oxyfluorfen levels in the container bed runoff were 9 to 27 times higher than those in container leachate during the 3 irrigations following herbicide application. Maximum oxyfluorfen level in the container leachate was 8.3 ppb following the first irrigation but declined to 2.0 ppb by the 12th irrigation. The oxyfluorfen level was still about 2.0 ppb following the 75th irrigation. Oxyfluorfen in the container bed runoff peaked at 99 ppb following the 3rd irrigation before declining to 67 ppb following the 6th irrigation.
Karla M. Addesso, Anthony L. Witcher, and Donna C. Fare
Adoption of biological control tools in woody ornamental nursery production has lagged behind other agriculture fields. One of the major obstacles to adoption is lack of information on the efficacy of various biological control agents in nursery production systems. The predatory mite Amblyseius swirskii, sold commercially as “swirski mite,” is a generalist predatory mite that has recently been adopted as a generalist control for a wide range of mite and insect pests, including thrips (Thripidae), whiteflies (Aleyrodidae), eriophyid mites (Eriophyidae), broad mite (Polyphagotarsonemus latus), and spider mites (Tetranychidae). A controlled-release sachet formulation of swirski mite was evaluated in three experiments to determine whether size of the tree, timing of first application, or sun intensity would affect treatment efficacy. Pest numbers on plants was evaluated biweekly for 12 weeks. The swirski mite sachets controlled broad mite and spider mite outbreaks on red maple trees (Acer rubrum) grown in nos. 3 and 15 nursery containers, respectively. Application at the time of red maple rooted cutting transplant was not necessary to achieve summer-long control of pests. No outbreaks of target pests on flowering dogwood (Cornus florida) in no. 5 containers grown under both full sun and shade, but with low levels of broad mite persisting in the shade treatment and thrips persisting in sun. These results suggest that swirski mite is a promising candidate for biological control in woody ornamental nursery production.
Anthony L. Witcher, Fulya Baysal-Gurel, Eugene K. Blythe, and Donna C. Fare
Flowering dogwood (Cornus florida) is a valuable nursery product typically produced as a field-grown crop. Container-grown flowering dogwood can grow much faster than field-grown plants, thus shortening the production cycle, yet unacceptable crop loss and reduced quality continue to be major issues with container-grown plants. The objective of this research was to evaluate the effects of container size and shade duration on growth of flowering dogwood cultivars Cherokee Brave™ and Cherokee Princess from bare-root liners. In 2015, bare-root liners were transplanted to 23-L (no. 7) containers and placed under shade for 0 months (full sun), 2 months (sun4/shade2), 4 months (sun2/shade4), or 6 months (full shade) during the growing season. In 2016, one-half of the plants remained in no. 7 containers and the other half were transplanted to 50-L (no. 15) containers and assigned to the same four shade treatments. In 2015, plant height was greatest with full shade for both cultivars, whereas stem diameter and shoot dry weight (SDW) were greatest in full shade for Cherokee Brave™. In 2016, both cultivars in no. 15 containers had greater plant height, stem diameter, root dry weight (RDW), and SDW. Full shade resulted in the greatest height, stem diameter, RDW, and SDW for Cherokee Brave™, and improved overall growth for ‘Cherokee Princess’. However, vigorous growth due to container size and shade exposure increased the severity of powdery mildew (Erysiphe pulchra) in both years. Substrate leachate nutrient concentration (nitrate nitrogen and phosphate) was greater in no. 15 containers but shade duration had no effect.
Cecil T. Pounders, Eugene K. Blythe, Donna C. Fare, Gary W. Knox, and Jeff L. Sibley
This study reports on the performance of 34 clones of crapemyrtle (Lagerstroemia indica L., L. fauriei Koehne, and L. indica × L. fauriei hybrids) grown in field plots at four locations representative of different environments in the southeastern United States. Traits evaluated were spring leaf-out and initiation of flowering in the second season after field planting and plant height after 3 years of growth. Cluster analysis (Ward's method) was used for grouping and comparison of means across locations for each trait. Best linear unbiased prediction was used for estimating random effects in linear and generalized linear mixed models to better determine the general performance of the clones under a variety of environmental conditions. Each clone's trait stability was quantified using the regression of an individual genotype's performance for each of the three studied traits on an environmental index based on the trait mean for all genotypes grown in an environment. Sequence of clone leaf-out and size rankings were more stable across the environments than the sequence in which the various clones initiated flowering. L. fauriei clones and clones originating from the initial cross between L. indica and L. fauriei were generally later to leaf out, earlier to flower, and more vigorous growers than L. indica or the complex L. indica × L. fauriei clones that were evaluated. First flowering was affected by environmental variation more with interspecific hybrids than with L. fauriei and L. indica clones. Performance, particularly with respect to plant height, of several clones did not agree with previously published classifications. Information generated by this study will allow crapemyrtle breeders, landscape professionals, and consumers to better select the most appropriate crapemyrtle clone for a particular application.
Donna C. Fare, Charles H. Gilliam, Gary J. Keever, and John W. Olive
Two experiments were conducted to evaluate the effects of cyclic irrigation on leachate NO3-N concentration, container leachate volume, total effluent volume, and growth of Ilex crenata Thunb. `Compacta'. In Expt. 1, container leachate volume was reduced 34% when 13 mm of water was applied in three cycles compared to continuous irrigation of 13 mm per unit time. Forty-nine percent less container leachate volume was collected from a continuous application of 8 mm than from that of 13 mm water. In Expt. 2, container leachate volume was reduced 71% when 6 mm was applied in a single application over 30 minutes compared to 13 mm applied continuously for 1 hour. Total effluent was reduced by 14% and 10% in Expts. 1 and 2, respectively, when 13-mm irrigation was applied in three cycles compared to one continuous irrigation. Container leachate NO3-N concentrations from cyclic irrigation were generally less than leachate NO3-N concentrations from continuous irrigation treatments. The percentage of applied N leached as NO3-N ranged from 46% when 13-mm irrigation was applied in three cycles to 63% when 13-mm irrigation was applied in a single cycle. Leachate NO3-N concentration was reduced as irrigation volume was reduced from 13 to 6 mm in Expt. 2. Percentage of applied N leached as NO3-N was 63%, 56%, and 47% when 13-mm irrigation was applied in one, two, and three cycles, respectively, compared to 19%, 16%, and 15% when 6-mm irrigation was applied in one, two, and three cycles, respectively. `Compacta' holly shoot and root growth were minimally affected by cyclic irrigation or irrigation volume.
Diana L. Berchielli-Robertson, Charles H. Gilliam, and Donna C. Fare
A 2-year study evaluated the effects of three weed species: eclipta [Eclipta alba (L.) Hasskarl], prostrate spurge (Euphorbia supina Raf.), and wood sorrel (Oxalis stricta L.) on growth of container-grown `Gumpo White Sport' azalea (Rhododendron eriocarpum), R. x `Fashion', and Berberis thunbergii DC. var. atropurpurea `Crimson Pigmy'. Competitiveness among weed species as ranked from greatest to least was eclipta, prostrate spurge, and wood sorrel. Greater populations of eclipta and prostrate spurge resulted in decreased shoot dry weight of `Fashion' and `Gumpo White Sport' azalea. Prostrate spurge had a similar effect on `Crimson Pigmy' barberry in both small (3.8-liter) and large (15.2-liter) containers, while eclipta reduced shoot dry weight of barberry only in large containers. Wood sorrel had little effect on shoot dry weight of `Fashion' and `Gumpo White Sport' azalea.