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Thomas H. Yeager

The nursery industry in Broward County, Fla., had to choose between partaking in the resolution needed to achieve 10 ppb total phosphorus discharged to the Everglades or face regulation. The industry decided to pursue the proactive route and implement best management practices (BMPs). Teams of industry personnel were formed to develop the content of the Florida Container Nursery BMP Guide that contained the following chapters: 1) nursery layout, 2) container substrate and planting practices, 3) fertilization management, 4) container substrate nutrient monitoring, 5) irrigation water quality, 6) irrigation application, 7) irrigation uniformity, 8) erosion control and runoff water management, 9) pesticide management, and 10) waste management. Each team was to determine the content of their chapter, based on cultural practices producers were currently using, or could be using, which would minimize or reduce surface water movement of phosphorus from the nursery to adjacent water. Cultural practices, brought forth after a consensus was achieved by each team in concert with governmental agencies, associations, and allied industries, were meshed with research information, or the “best” information available from academic sources to ensure that the resolutions or BMPs that were written would contribute to resolving the confl ict (i.e., elevated total phosphorus in canal waters). Consensus development is a new challenge for most academicians but it is important because unbiased and science-based knowledge is needed to assist in BMP development. Furthermore, consensus of those directly and indirectly involved in the nursery industry helps facilitate the use of BMPs. Once the Florida Container Nursery BMP Guide is adopted by rule under the statutory authority of the Florida Department of Agriculture and Consumer Services, nursery operators voluntarily using the BMPs and keeping appropriate records will receive a waiver of liability from cleanup costs associated with contaminated ground or surface water, and be presumed to be in compliance with state water quality standards.

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Thomas H. Yeager

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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Thomas H. Yeager

Nursery operators had the opportunity to participate in a process to develop a voluntary incentive-based regulation that consummated the consensus of nursery and regulatory personnel regarding the best fertilization and irrigation cultural practice information available for producing plants in containers. Florida Department of Agriculture and Consumer Services (FDACS), which has statutory authority to develop and adopt practices by administrative rule, administered the process, and they relied on university extension personnel to provide education so nursery operators would be prepared to implement practices consistent with the regulation. Nursery operators who voluntarily implemented these practices received a waiver of liability from the recovery costs associated with the cleanup of groundwater contaminated with nitrate nitrogen if each of the following activities had taken place: 1) a notice of intent was filed with FDACS to implement accepted practices; 2) practices based on consensus of the industry were used and guidelines followed; and 3) fertilization and irrigation records were maintained. Participation in an industry-driven regulatory program where nursery operators agreed to use the best cultural practices available prior to the identification of a specific groundwater issue was a significant proactive step for the industry.

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Thomas H. Yeager

Ilex vomitoria Ait. `Nana' root and-shoot growth increased as rate of fertilizer applied from a 6N-1P-3K solution increased from 0.5 to 2.5 g N/3-liter container during a 26-week experiment. Percentage of applied N, P, and Kin the plant and growth medium decreased as N applied increased. Dividing the fertilizer among one, two, or four applications per week resulted in similar use of applied N, P, and K. Shoot dry weights for the 0.5 g N/container treatment were less than for the Osmocote (18N-2.6P-10K) treatment (2.5 g N/container), but the percentage of applied N, P, and K in the plant and growth medium (55%, 42%, and 75%, respectively) was greater than for the Osmocote treatment (31%, 15%, and 27%, respectively).

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Thomas H. Yeager

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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Thomas H. Yeager

Three-month-old rooted cuttings of Ligustrum japonicum Thunb. were planted in a 2 pine bark: 1 Canadian peat: 1 sand substrate (by volume) in either 0.75- or 2.2-liter containers and grown for 17 weeks in a greenhouse. One-half of the plants grown in 0.75-liter containers were transplanted to 2.2-liter containers after 11 weeks and grown for 6 weeks in 2.2-liter containers. Shoot dry weights were highest for plants grown 17 weeks in 2.2-liter containers and smallest for plants grown 17 weeks in 0.75-liter containers. Root dry weights were similar for plants grown 17 weeks in 0.75-liter containers. The percentage of applied N used by shoots and roots (44% and 8%, respectively) was highest for plants grown 17 weeks in 2.2-liter containers and smallest (30% and 5%, respectively) for plants grown 17 weeks in 0.75-liter containers.

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Jeff B. Million and Thomas H. Yeager

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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Jeff B. Million and Thomas H. Yeager

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.

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Jeff B. Million and Thomas H. Yeager

Irrigation scheduling in container nurseries is challenging due to the wide range of plant production conditions that must be accounted for at any given time. An irrigation scheduling system should also consider weather affecting evapotranspiration to apply proper amounts of water that will ensure optimal growth with minimal runoff (container drainage). We developed an automated system that relies on routine leaching fraction (leachate/water applied) testing and real-time weather recorded on-site to make adjustments to irrigation. A web-based program (CIRRIG) manages irrigation zone inputs [weather and leaching fraction (LF) test results] and outputs irrigation run times that can be implemented automatically with programmable logic controllers. In this study conducted at a nursery in central Florida, we compared the automated technology (CIRRIG) with the nursery’s traditional irrigation practice (TIP) of manually adjusting irrigation based on substrate moisture status of core samples taken twice weekly. Compared with TIP, CIRRIG reduced water use in six of seven unreplicated trials with water savings being greater for microirrigated crops grown in large containers than for sprinkler-irrigated crops in small containers. Reduced pumping cost associated with water savings by CIRRIG was estimated to be $3250 per year, which was insignificant compared with the labor savings of $35,000 to $40,000 anticipated by the nursery using CIRRIG in lieu of TIP. At the end of the project, the necessary hardware was installed to expand CIRRIG nursery-wide and control 156 zones of irrigation.