Florida is one of the leading states for the commercial production of ornamental horticulture in the United States, producing $1.8 billion in crop value per year (U.S. Department of Agriculture, 2015). About 46% of the production area is used for container production (Hodges et al., 2016). In a survey of Florida nurseries, 76% of growers produced plants in containers, which represented 86% of all products sold (Hodges, 2011). In the United States, 65% of ornamental plants sold were grown in containers. Container production is resource intensive (hand labor, fertilizer, herbicide, etc.) and commonly occurs with overhead irrigation that inefficiently applies large volumes of water (Yeager et al., 2010). Although inefficient with regard to plant water use, overhead irrigation is the least expensive and most flexible method of applying water to container crops because spacing configurations change frequently as plants grow in size or are sold. The population of Florida is estimated to increase by 3 million residents by 2025 (University of Florida, 2017). Population growth in Florida will intensify the demand for water in the future. As water becomes more limited because of increased demand and/or periodic drought, container growers may need to justify their use of water.
Ornamental plants have been grown in a multipot box system with a significant reduction of inputs (water and energy) and increased growth parameters (Irmak et al., 2004). This system captures irrigation and rain water into an irrigation reservoir and shields the external sides of containers from solar radiation. However, the multipot box system does not address other factors such as the lack of weed control, the lack of ability to use existing nursery infrastructure, and the possibly prohibitive cost for large-scale adoption. A similar method could be used, without the reservoir, using a plastic mulch system. A plastic mulch system could improve favorably on some of the aforementioned limitations.
Horticultural crops, such as cucumber (Cucumis sativus), eggplant (Solanum melongena), melon (Cucumis melo), pepper (Capsicum annuum), potato (Solanum tuberosum), radish (Raphanus raphanistrum ssp. sativus), squash (Cucurbita pepo), and tomato (Solanum lycopersicum), have benefited from plastic mulch in field production, through water and fertilizer savings, yield increases, earlier fruiting, weed reductions, improved fruit quality, and soil temperature modulation (Lamont, 2005; Locascio et al., 1985; Ramakrishna et al., 2006; Ruidisch et al., 2013; Zhao et al., 2012). We believed that by using a novel method of placing low-density polyethylene mulch over the top of nonspaced (container-tight or pot-to-pot) containers during the beginning phase of the production cycle, similar to vegetable field–grown crops, similar benefits might be attained. The effectiveness of mulch in reducing water loss in container production varies by the study. Altland and Lanthier (2007) demonstrated production with a variety of organic and nonorganic mulch types. Hydrangea (Hydrangea macrophylla) grown with overhead irrigation in a primarily bark substrate had similar water demand to nonmulched control plants. Amoroso et al. (2010) similarly reported water loss from 3-L containers was mainly driven by transpiration of giant arborvitae (Thuja plicata) when mulches were used. By contrast, Argo and Biernbaum (1994) showed in subirrigated easter lily (Lilium longiflorum) grown in peat substrates, covering the surface with a plastic evaporation barrier resulted in 35% fewer irrigation events and 22% to 50% reduction in the amount of water applied compared with nonmulched control plants. Lohr and Pearson-Mims (2001) reported a reduction in frequency of irrigation of 34% with sphagnum moss mulch and a 13% reduction with pine bark (0.2- to 0.4-inch particle size) mulch.
We also believed, similar to other studies, that mulching might cause beneficial temperature modulation (Snyder et al., 2015), which might enhance growth, provide beneficial environmental impacts such as reducing fertilizer leaching (Argo and Biernbaum, 1994), and reduce the need for herbicides (Marble et al., 2017). The mulch might also minimize hand labor to remove weeds and pick up containers that blow over. An important consideration in our study and the use of a mulching method is that growers would have to make minimal costly changes to existing overhead irrigation infrastructure, and there would be no need to buy specialized equipment. The goal of our study was to determine if plastic mulch used over nonspaced containers would provide sustainable benefits (economic, environmental, and quality enhancement) to growers without additional production costs.
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