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Sandra B. Wilson, P. Chris Wilson, and Joseph A. Albano

Invasive species have disrupted thousands of acres of natural areas in Florida and appear to have a physiological competitive advantage over native species. The influence of light and temperature on germination was determined for the invasive Mexican petunia (Ruellia tweediana Griseb.) and native wild petunia (Ruellia caroliniensis Steud.). Seeds were collected and germinated in incubators with light or darkness at 15, 24, 33, and 30/20 °C. Light increased germination for each species, except at 15 °C (R. caroliniensis). For R. caroliniensis, highest germination (86% to 94%) occurred at 33 °C and 30/20 °C. Highest germination of R. tweediana (98% to 100%) occurred at 30/20 °C. Studies also were initiated to determine if R. tweediana has a competitive advantage over the native species when grown under wet and dry substrate conditions. Growth and development measurements after 8 weeks under controlled conditions revealed that R. tweediana grown in wet conditions had the greatest dry weight increase as compared to other treatments. Ruellia caroliniensis had higher specific leaf area when grown in wet or dry conditions, as compared to R. tweediana. Throughout the experiment, net CO2 assimilation of R. caroliniensis grown under dry or wet conditions was consistently lower than that of R. tweediana. Shoot nitrogen and phosphorus use efficiencies were generally greatest for R. tweediana plants grown in wet conditions. For shoot nutrient content, significant species × moisture interactions occurred for measured phosphorus (P) and calcium (Ca). When grown in wet conditions, R. tweediana had less shoot P and Ca as compared to dry conditions. For root nutrient content, species × moisture interactions were insignificant for each measured nutrient, with the exception of potassium (K). Potassium use efficiency of R. tweediana roots grown in wet conditions was higher than that of R. tweediana grown in dry conditions and R. caroliniensis grown in wet conditions.

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Joseph P. Albano, William B. Miller, and Mary C. Halbrooks

A specific physiological disorder, bronze speckle (J.P.A.'s nomenclature), was consistently induced in `First Lady' and `Voyager' marigold with Fe-DTPA concentrations greater than 0.018 mm Fe-DTPA (1 ppm) applied to a soilless medium. The disorder was characterized by specific symptomology distinguished visually by speckled patterns of chlorosis and necrosis, and downward curling and cupping of leaves. The percentage of total leaf dry weight affected with symptoms generally increased with increasing Fe-DTPA treatments. Symptomatic leaf tissue had a greater Fe concentration than corresponding asymptomatic leaf tissue. Leaf Mn concentrations in symptomatic and asymptomatic tissue were similar. In `First Lady', older leaf tissue accumulated more total Fe and was associated with more severe symptoms than younger tissue. Media leachate Fe concentrations increased over 6 weeks and were larger at greater Fe-DTPA treatments. Adjustment of nutrient solution pH to 4.0, 5.25, or 6.5 did not alter media pH, nor did it prevent disorder symptoms. Application of Fe-DTPA containing nutrient solution to a soilless medium resulted in leachate Fe levels 3 times greater than for FeSO4 treatments. Chemical names used: ferric diethylenetriaminepentaacetic acid, monosodium salt (Fe-DTPA).

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Julie P. Newman, Joseph P. Albano, Donald J. Merhaut, and Eugene K. Blythe

Release characteristics of four different polymer-coated fertilizers (Multicote, Nutricote, Osmocote, and Polyon) were studied over a 47-week period in a simulated outdoor, containerized plant production system. The 2.4-L containers, filled with high-fertility, neutral-pH substrate, were placed on benches outdoors to simulate the environmental conditions often used for sun-tolerant, woody perennials grown in the southwestern United States. Container leachates were collected weekly and monitored for electrical conductivity, pH, and concentrations of NH4 +N, NO3 N, total P, and total K. Concentrations of most nutrients in leachates were relatively high, but fluctuated frequently during the first third of the study period, and then gradually decreased and stabilized during the last 27 weeks. Osmocote often resulted in greater NH4 + and total inorganic N concentrations in leachates than other fertilizers during weeks 1 through 5, whereas Multicote produced higher NH4 + in leachates than most of the other fertilizer types during weeks 9 through 12. Overall, total P concentrations were greater with Multicote during a third of the experimental period, especially when compared with Osmocote and Polyon. Differences were also observed among treatments for leachate concentrations of K, with Polyon and Multicote fertilizers producing greater K concentrations in leachates compared with Osmocote during several weeks throughout the experimental period. Leachate concentrations of NO3 N and P from all fertilizer types were usually high, especially from week 5 through week 30.

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Joseph P. Albano, Donald J. Merhaut, Eugene K. Blythe, and Julie P. Newman

Nutrient release characteristics of four different controlled-release fertilizers (Osmocote, Nutricote, Polyon, and Multicote) were monitored during an 11-month period in a simulated outdoor nursery production facility. Although no plants were used in the experiment, fertilization rates, irrigation regimes, and cultural practices simulated those typically used to produce fast-growing, high-nutrient-requiring containerized woody ornamentals. Fertilizer prill release characteristics were monitored through analyses of leachates, which were collected weekly. Concentrations of Mg, Mn, Zn, Cu, and Mo were relatively high during the first 5 to 10 weeks of the experiment, then declined and usually stabilized during the remainder of the study. However, Mn and Zn displayed erratic increases in concentrations several times throughout the study. Calcium concentrations did not increase until the fifth week, rapidly peaked to about 300 mg·L–1, and then decreased and leveled off to ≈80 to 100 mg·L–1 during the remainder of the study. Several significant differences were observed between treatments. The Osmocote treatment had significantly greater Ca and Mg concentrations in the leachate than the other fertilizer types during the last 6 weeks of the study, whereas the Nutricote treatment often had significantly greater Fe concentrations than leachates from other treatments, especially during the last 26 to 35 weeks of the study, and significantly greater Zn concentrations than the other CRFs during the last 21 weeks of the study. Based upon U.S. Environmental Protection Agency guidelines, concentrations of Fe were often more than the allowable limit of 0.3 mg·L–1 with all fertilizer types, but especially with Nutricote. Concentrations of Mn and Cu also exceeded federal guidelines, particularly during the first several weeks of the study.

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Joseph P. Albano, James Altland, Donald J. Merhaut, Sandra B. Wilson, and P. Chris Wilson

Liming agents (LAs) in irrigation water, typically associated with carbonates and bicarbonates of calcium (Ca) and magnesium (Mg), contribute to water alkalinity. Repeated application of LA to container crops can cause media-solution pH to rise overtime, that uncorrected, can lead to a nutrient availability imbalance that may be suboptimal for plant-growth due to nutrient disorder(s). To correct high levels of LA in irrigation water, growers can inject acid into their irrigation system to neutralize alkalinity. Therefore, a 52-week study was conducted using irrigation water, substrate, and plants from a commercial nursery in Florida that has a history of poor water quality and plant production problems related to high alkalinity irrigation water. The objectives of the study were to assess substrate pH, electrical conductivity (EC), and nutrients, and plant nutrition and growth for thyrallis (Galphimia gracilis Bartl.) to irrigation water acidification. Treatments consisted of irrigation water acidified with sulfuric acid (H2SO4) to neutralize 0% (control), 40%, or 80% of calcium carbonates (CaCO3) yielding a CaCO3 (meq·L−1)/pH levels of 5 [High Alkalinity (H-A)]/7.37, 3 [Medium Alkalinity (M-A)]//6.37, and 1 [Low Alkalinity (L-A)]//4.79, respectively. Substrate analysis by the 1:2 dilution method at the end of the study was significant (P < 0.05) for pH 6.2, 5.2, and 4.7 for the H-A, M-A, and L-A treatments, respectively, and for nutrients Ca, Mn, and Zn. Foliar nutrient levels were statistically significant (P < 0.05) for alkalinity treatment for Fe, K, Mn, P, and Zn. Alkalinity treatment was significant (P < 0.05) for growth, leaf greenness (by SPAD), and quality (by survey) with the M-A treatment producing more biomass, having greener leaves, and the highest aesthetic quality value than the H-A or L-A treatments. A qualitative survey of root systems at harvest showed that the M-A and L-A treatment root systems were greater than the H-A treatment based on visual side-wall root development. These data demonstrate that irrigation water acidification does alter substrate pH and nutrients and plant tissue nutrient levels and growth over a long-term production cycle typical for nursery crops.

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Donald J. Merhaut, Eugene K. Blythe, Julie P. Newman, and Joseph P. Albano

Release characteristics of four types of controlled-release fertilizers (Osmocote, Nutricote, Polyon, and Multicote) were studied during a 47-week simulated plant production cycle. The 2.4-L containers containing a low-fertility, acid-based substrate were placed in an unheated greenhouse and subjected to environmental conditions often used for production of azaleas and camellias. Leachate from containers was collected weekly and monitored for pH, electrical conductivity, and concentrations of NH4 + N, NO3 N, total P and total K. Leachate concentrations of all nutrients were relatively high during the first 10 to 20 weeks of the study, and then gradually decreased during the remaining portion of the experiment. Differences were observed among fertilizer types, with Multicote often resulting in higher concentrations of N, P, and K in leachates compared to the leachates from the other fertilizer types during the first half of the study. Concentrations of NO3 and P from all fertilizer types were often above permissible levels as cited in the federal Clean Water Act.

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Eugene K. Blythe, Donald J. Merhaut, Julie P. Newman, and Joseph P. Albano

Leachate from containerized substrate containing one of four different controlled-release fertilizers (Osmocote, Nutricote, Polyon, or Multicote) were monitored for concentrations of Ca, Mg, Fe, Mn, Zn, Cu, and Mo during a 47-week period. Environmental and cultural practices simulated an unheated greenhouse production program typically used for low-nutrient-requiring crops such as azalea and camellia. Leachate concentrations of all nutrients were relatively high during the first 10 to 20 weeks of the study, and then gradually decreased during the remaining portion of the experiment. Few differences were observed among fertilizer types. Of the elements monitored, only Fe and Mn leachate concentrations were above critical levels specified in the Clean Water Act by the U.S. EPA.

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Mary Taylor Haque, Joseph P. Albano, William B. Miller, Ted Whitwell, and Kristy Thomason

Student Teaching and Research Initiative through Volunteer Employment (STRIVE) is an innovative new program developed collaboratively by faculty and students to offer students work experience opportunities in the Dept. of Horticulture while assisting with horticultural needs. The program promotes volunteerism and education while strengthening participating faculty, staff, and students in areas of research, teaching, or public service. STRIVE requires a voluntary commitment of 3 h/week in an area agreed on by participants and their supervisors. Participants are formally acknowledged by the department for their contributions after completing the semester-long program. Students participating thus far have assisted in teaching laboratories, program development, and greenhouse management.

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James S. Owen Jr., Stuart L. Warren, Ted E. Bilderback, and Joseph P. Albano

The physical and chemical properties of pine bark yield low water and nutrient efficiency; consequently, an engineered substrate altering the substrate properties may allow greater water and nutrient retention. Past research has focused on controlling the quantity and rate of water and nutrient inputs. In this study, pine bark was amended at 8% (by volume) with a Georgiana palygorksite-bentonite blended industrial mineral aggregate with a particle size of 850 μm-4.75 mm or 300 μm-710 μm to improve water and nutrient efficiency. Each particle size was pretreated at temperatures of ≈140 °C (pasteurized) or ≈390 °C (calcined). The study was a 2 (particle size) × 2 (heat pretreatment) factorial in a randomized complete-block design with four replications. The control was a pine bark substrate amended with 11% sand (by volume). Containers (14 L) were topdressed with 17–5–12 controlled release fertilizer. A 0.2 leaching fraction was maintained by biweekly monitoring container influent from spray stakes and effluent volume measured daily. An aliquot of the daily collected effluent was analyzed for phosphorus (P). After 112 days, tops and roots were harvested, dried, and weighed for dry weight comparisons. Compared to pine bark amended with sand the 300 μm-710 μm particle size mineral decreased mean daily water application by ≈0.4 L/day per container. The calcined mineral reduced P leaching by ≈10 mg of P per container or 60% over the course of the study compared to pine bark: sand. Top and root dry weights were unaffected. These results suggest 300 μm–710 μm calcined mineral provided the most significant decreases in water use and P leaching while growing an equivalent plant.

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James S. Owen Jr, Stuart L. Warren, Ted E. Bilderback, and Joseph P. Albano

Nonpoint source effluent containing nitrate N (NO3-N) and phosphorus (P) from containerized nursery production has garnered local, regional, and national concern. Industrial minerals have long been used as absorbents, agrochemical carriers, and barriers to retain heavy metals. Our objective was to determine the effects of a palygorskite–bentonite industrial mineral aggregate on the physical and chemical properties of a soilless substrate and the resulting impact on water and nutrient efficiency. The mineral aggregate had two particle size ranges (0.25 to 0.85 mm or 0.85 to 4.75 mm) in combination with two temperature pretreatments [low volatile material (LVM) or regular volatile material (RVM)]. A representative substrate (8 pine bark:1 coarse sand) of the southeastern United States nursery industry was also included in the study as a control. Cotoneaster dammeri C.K. Schneid. ‘Skogholm’ was grown in all substrates on collection pads that allowed for the quantification of daily influent and effluent volumes to calculate cumulative NO3-N, ammonium N (NH4-N), and dissolved reactive phosphorus (DRP) loss for 112 days. There was a 13% to 15% decrease in daily water application volume with no effect on Skogholm cotoneaster growth, which equated into a savings of 22 to 26 L per 14-L container in mineral aggregate-amended substrates compared with a sand-amended substrate (control). Mineral aggregate-amended substrates decreased NH4-N and DRP effluent 39% and 34%, respectively, compared with the control. In addition, LVM and particle size 0.25 to 0.85 mm reduced effluent DRP compared with the 0.85 to 4.75-mm RVM aggregate. Plant dry weight was unaffected by any of the treatments. Substantial nutrient content reduction in effluent and reductions in water application were achieved with amending pine bark with 0.25 to 0.85 mm LVM industrial mineral aggregate. A 0.25 to 0.85-mm LVM industrial mineral aggregate pine bark-amended substrate reduced effluent DRP and NH4-N greater than 40% and reduced water application 15% or 26 L when compared with the industry representative substrate.