Florida is the second-largest strawberry (Fragaria ×ananassa) producer in the United States. The industry in Florida generally relies on short-day cultivars, planted in early October, and harvested in late November. Strawberry transplants for the winter season are usually grown in northern latitudes and shipped to southern states in late September for planting (Hochmuth et al., 2006a; Hokanson et al., 2004). The most common strawberry transplant in Florida is bare-root (BR) with leaves still attached (Santos et al., 2012). Under the traditional production practices of Florida, BR require between 3500 and 5500 m3·ha−1 per season of continuous sprinkler irrigation during daylight hours to reduce air temperature around the strawberry crown (Bish et al., 1997; Cluever et al., 2016; Forcelini et al., 2017; Santos et al., 2012). Additionally, the BR field-harvesting process reduces the number of functional leaves, creates entry points for pathogen infection, and increases variability in transplant size and flowering pattern (Bish et al., 1997; Hokanson et al., 2004).
Strawberry plug transplants (SP) are an alternative to BR. The active root system and water retention capacity of the SP allows them to establish with minimal sprinkler irrigation (Crawford et al., 2000; Durner et al., 2002; Janisch et al., 2012). In addition to the potential water savings, SP exposed to adequate flower induction conditions in the nursery can produce higher early and total yield than BR (Durner, 2015; Hennion et al., 1997; Lieten, 2012; Treder et al., 2015; Wan et al., 2018).
One limitation of SP is their higher cost ($0.37–$0.38 per transplant), compared with BR ($0.15–$0.16 per transplant), which could increase total production costs in Florida by $3833/acre, assuming a plant density of 17,424 plants/acre (Lareault Inc., unpublished). An alternative to reduce the acquisition cost of SP is the optimization of Florida-produced SP, allowing a reduction of shipping and handling cost of plant material for Florida strawberry growers. Despite the potential benefits of SP transplants, there are still several challenges to overcome for the adoption of Florida-produced SP.
Several studies have evaluated the performance of out-of-state conditioned SP in comparison with BR in Florida (Bish et al., 1997, 2003; Cantliffe et al., 2007; Hochmuth et al., 2006a, 2006b; Southwest Florida Water Management District, 2000). However, few researchers have evaluated the response of unconditioned Florida-produced SP to time in nursery before field transplanting. Across the United States, recommendations for time in nursery before transplanting range from 4 to 7 weeks for SP (Crawford et al., 2000; Takeda et al., 2010). The optimization of production techniques for unconditioned SP is necessary to exploit the potential of Florida-produced SP. Overgrown SP could become rootbound. Conversely, undergrown SP could have reduced early yield.
Similarly, SP are directly rooted into specially designed trays, usually containing peat-based media (Durner et al., 2002). Trays are typically classified by their cell number, varying in the quantity of growing media that can be contained in each cell. Larger cells could allow for a higher volume of growing media and greater root growth but would increase the amount of space needed for SP production, reducing profitability, and could also increase the time for an adequate formed root ball. Conversely, smaller cells could restrain root growth and reduce SP early and total yield.
The primary objectives of this study were to evaluate the effect of time in nursery and tray size on early and total yield for Florida-produced SP, and to compare their performance to BR.
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