Claudia Larsen’s research while affiliated with University of Florida and other places

A descriptive survey was conducted of container plant growers using reclaimed water (processed sewage) for irrigation of nursery crops and growers whose businesses were located in areas where reclaimed water was available but not used for irrigation. Surveys were completed during site visits except when participants wanted to complete the survey at a later time. Nurseries using reclaimed water produced trees, shrubs, perennials, bedding plants, foliage plants, and potted flowering plants. Average area outdoors or under shade irrigated with overhead sprinklers was 3.5 ha (8.6 A) and 10,777 m2 (116,000 ft2) for greenhouses. Participants responded that reclaimed water quality (67%) and quantity (50%) were consistent over time. All reclaimed water users were satisfied with both quality and quantity of reclaimed water. Most growers (83%) not using reclaimed water were using well water as the primary source of water. Seventy-one percent of non-reclaimed users responded that expense of connection to reclaimed water was a limitation, while 57% indicated that unknown water quality and health or safety concerns were limitations. Results from this survey indicated acceptance of reclaimed water among active users and the need for education about reclaimed water for non-reclaimed users.

Container Crop Resource Optimization Program (CCROP) is an integrative model which simulates the growth and water and nutrient requirements of a woody ornamental shrub grown in small (2.8–11.4L) containers in a field environment with overhead sprinkler irrigation. The model was developed for producers, producer advisers and researchers to support best management practice decision-making in container nursery production. We describe the primary processes simulated by CCROP particularly how they differ from traditional crops grown in-ground and assess the ability of CCROP to simulate measured values for a range of irrigation and fertilizer trials and transplanting dates. Results of model testing with 11 trials indicate that CCROP provided reasonable outcomes for biomass and leaf area growth as well as evapotranspiration, runoff (container drainage plus un-intercepted irrigation and rainfall) and nitrogen loss.

Vinca [Catharanthus roseus (L.) G. Don], salvia (Salvia splendens F. Sellow ex Roem. and Schult.), Dwarf Yaupon holly (Ilex vomitoria Ait. 'Nana'), and 'Helleri' holly (Ilex crenata Thunb. 'Helleri') were grown in 2.3-L containers with soilless substrates in a greenhouse. Irrigation was applied as needed to the substrate surface or applied to the substrate surface and applied over plant foliage. Irrigation for both application methods was composed of 0%, 25%, 50%, 75%, or 100% reclaimed water (processed sewage) with deionized water composing the remainder. Shoot dry weights of marketable-sized plants were either larger or similar when 100% reclaimed water was used compared with 0% reclaimed water (deionized). Root dry weights exhibited a similar response except for salvia roots that were smaller with 100%reclaimed water irrigation regardless of application method. Leachate NO3-N, phosphorus (P), and potassium (K) generally decreased throughout the experiments for vinca and Dwarf Yaupon holly and were highest at experiment midpoint for 'Helleri' holly and lowest for salvia. Leachate electrical conductivities (ECs) were generally highest at experiment termination for vinca and salvia, whereas ECs of Dwarf Yaupon and 'Helleri' holly tended to peak at experimental midpoint and then decrease slightly at termination. ECs were usually less than 2 dSm-1 except at experimental midpoint (4.5 months) for 'Helleri' holly. Based on the response of plants in this research, high-quality reclaimed water is a viable water source for annual and woody container-grown nursery crops.

CCROP (Container Crop Resource Optimization Program) is a web-based decision support tool that simulates growth, nutrient, and irrigation requirements of woody ornamental container-grown crops. CCROP is used to assist growers/managers and other industry stakeholders select best management practices that maximize use of water and fertilizer resources and minimize environmental impact. Inputs for CCROP include daily weather data uploaded from the Florida Automated Weather Network (FAWN) as well as critical management practices (e.g. plant date, container size and spacing, fertilizer, pruning, etc.). Outputs include plant growth, evapotranspiration, irrigation requirement, nutrient uptake, and leaching of applied nutrients. A real-time tool recommends daily water application based on resupplying that which is lost through evapotranspiration. Examples of simulations used to choose the best practices to implement and associated costs will be presented and discussed.

Traditional college students do not fit the demographic profile of people who are driving increased sales in gardening and landscaping or the use of native wildflowers. However, today's college students, especially those in plant-related disciplines, may be making future decisions regarding the use of native wildflowers for various applications. Many college students may be unaware of or disinterested in native wildflowers. We used a web-based survey to gauge awareness and interest of native wildflowers in Florida college students enrolled in plant-related disciplines. While students have a generally low awareness of native wildflowers, they expressed high levels of interest in learning more about the identification or cultivation of these species, seeing wildflowers, particularly on their campuses, and using wildflowers in different settings. Students were also interested in purchasing native wildflower seeds or finished plants from local retailers rather than through the Internet. We used student responses from this study to discuss education and marketing opportunities toward native wildflowers.

Florida container nurseries face the challenge of maintaining profitability while protecting the environment by improving the efficiency of water and fertilizer use. Best management practices (BMPs) provide irrigation and fertilization guidelines for meeting this challenge. BMPs are economically and technologically feasible to implement and they focus on the ground- and surface water quality issues of the state. However, increasing nursery participation in the statewide BMP program is crucial as the industry continues to expand and interface with urbanization.

Controlled-release fertilizers (CRFs) often contain higher than 1.3 % P. Phosphorus applied in excess of plant demand is leached and likely transported in runoff from the nursery site. One approach to achieving a reduction in P loss from the nursery is to reduce the amount of P applied. In our experiments, multiple-branched liners of Ilex cornuta ‘Burfordii Nana’, Ilex crenata ‘Helleri’, and Ilex vomitora ‘Nana’ were potted August 2006 with 10 L of a common nursery substrate. The substrate was amended with 4.2 and 0.9 kg/cubic meter of dolomitic limestone and Micromax® micronutrients, respectively, and amended with 46 g of a CRF that differed in P content [18N-0P-10K, 18N-0.4P-10K, 18N-1.3P-10K, or 18N-2.6P-10K (Harrell’s Inc., Lakeland, Florida)]. Twenty plants were grown with each CRF under natural light and each container was irrigated with approximately 400 ml as needed. After 18 months, shoot and root dry weights of Ilex cornuta ‘Burfordii Nana’ were greatest for plants that received 18N-0.4P-10K and 18N-2.6P-10K, and Ilex crenata ‘Helleri’ responded similarly after 16 months. Shoot and root dry weights were not different after 17 months for Ilex vomitora ‘Nana’ that received P in the CRFs. Substrate pour-through P ranged from a high of 10 mg/L at week 8 for the substrate amended with 18N-1.3P-10K to 0 mg/L at week 24 for substrate amended with 18N-0.4P-10K. These results indicated that CRF with 0.4 % P was adequate for production of the holly species tested and its use in lieu of a CRF with a higher P content would be considered a best management practice.

ENH-1119, an 8-page illustrated fact sheet by Tom Yeager, Claudia Larsen, Joe von Merveldt, and Tracy Irani, informs container nursery producers about irrigating with water processed from municipal sewage wastewater, the results of evaluations of overhead sprinkler irrigation systems, where to get it, and special application procedures and cautions. Includes references and a glossary. Published by the UF Department of Environmental Horticulture, May 2009.

Although research has shown that plants grown with subirrigation systems such as ebb-and-flow and capillary mat require less water and fertilizer inputs than traditional overhead irrigation methods, similar information for capillary wick irrigation has not been available. We compared the growth and water use response of azalea (Rhododendron sp. 'George Tabor') grown in 6.5-inch-diameter "azalea" containers with three irrigation methods [overhead (OVR), subirrigation (SUB), and capillary wick (WCK)] and four fertilizer nitrogen (N) rates 0.5 to 2.0 lb/yard3 supplied by an incorporated, resin-coated, controlled-release fertilizer (Nutricote 17N-3.1 P-6.7K, 180 d at 77 °F). OVR volume was adjusted to deliver 100% of evapotranspiration (ET) loss. For all irrigation treatments, the lowest N rate resulting in maximum plant growth was 1.0 lb/yard3, which was less than the label recommendation of 1.5 lb/yard3. At the N-limiting N rate of 0.5 lb/yard3, irrigation method had no effect (P < 0.05) on azalea growth. At N rates higher than 1.0 lb/yard3, decreased growth was observed for OVR compared with SUB and WCK. This negative effect on plant growth was attributed to salt injury as indicated by excessive pour-through electrical conductivity (EC) levels in OVR containers. At the end of the experiment, substrate EC was highest in the uppermost layer of SUB and WCK containers, reflecting the upward movement of water associated with these two irrigation methods. Water use efficiency, which ranged from 1.9 to 2.8 g shoot dry weight per liter of water lost through ET, was unaffected (P < 0.05) by irrigation method at the N rate of 1.0 lb/yard3. We concluded that the growth response of azalea to fertilizer N rate was similar for WCK and SUB despite periodic pour-through EC tests indicating higher substrate nutrient levels with WCK.

Woven polypropylene groundcloth is used extensively in plant nurseries as a permeable and durable surface for container plant production. To better understand the fate of overhead sprinkler irrigation water, we designed and constructed runoff platforms (2.7 m2) to measure runoff and leachate from single irrigation events as affected by slope and underlay substrates. Groundcloth-covered platforms at slopes of 1.5% and 11% were tested with each of five underlay treatments: no underlay, coarse sand, 50% coarse sand and 50% no underlay (CS50), gravel, and native sandy soil. We applied 0.9 cm of irrigation at 1.8 cm.h(-1) and determined runoff and leachate volumes. Runoff percentage [runoff x 100%/(runoff + leachate)] increased at the 11% slope for each underlay treatment. Mean (n=10) runoff percentages (RP) for the 1.5% and 11% slopes were 0.5% and 15.7%, respectively, for no underlay, 0.1% and 1.1% for coarse sand, 0.1% and 0.7% for CS50, 0.7% and 2.5% for gravel, and 0.1% and 3.1% for native sandy soil. The low RP observed indicate that a high percentage of nutrients and agrichemicals associated with container leachate would move into the underlying substrate or soil rather than directly running off into surface waters.