Although biocontainers (i.e., plant material–based containers) have emerged as a response to excessive plastic landfill waste, their adoption in the green industry could significantly increase crop watering requirements. Water availability has traditionally been an issue associated with arid and semiarid production sites (Fereres et al., 2003). However, this issue is quickly becoming a major environmental and economic consideration for all horticultural enterprises, regardless of climate. With demand, regulation, and cost of water all projected to increase (Beeson et al., 2004), growers will be subject to increasing pressure to assess their overall water use and identify areas to improve efficiency and reduce waste.
In their review of irrigation management techniques, Fereres et al. (2003) identified deficit irrigation [i.e., irrigation at a level below the rate of evapotranspiration (ET)], irrigation runoff reclamation, and the reduction of ET as the three main strategies for conserving water in horticultural production. Deficit irrigation is largely limited to field-grown crops and large-container production, given the ability of the plants to draw upon relatively large soil moisture reserves (Fereres and Soriano, 2007; Fereres et al., 2003). Compared with these production systems, the small volumes of pots and trays commonly used to produce floral and foliage crops limit their overall water-holding capacity and the rooting space available to the plant. Moreover, growers use deficit irrigation in times of limited water supplies to maintain survival rather than maximize growth (Fereres and Soriano, 2007). This loss in yield potential (i.e., biomass) is largely unacceptable when producing high-value ornamental greenhouse crops (Fereres et al., 2003).
Although deficit irrigation plays a very limited role in floriculture production, ET reduction and irrigation water reclamation may have important implications for greenhouse growers, especially those intending to adopt biocontainers in their operations. Although not the focus of this work, water reclamation in horticulture can be effectively implemented through the adoption of an ebb-and-flood (subirrigation) system which recirculates water and fertilizer runoff (Dole et al., 1994; Dumroese et al., 2006; Morvant et al., 1998). Ebb-and-flood-irrigated ‘Florida Sun Jade’ coleus (Solenostemon scutellarioides) shoot dry weight remained similar among seven different biocontainers (i.e., bioplastic, coir, manure, paper, peat, straw, and wood fiber) and a conventional petroleum-based plastic control (Koeser et al., 2013). However, the study found that the high rate of fertilization and container wetting–drying pattern associated with subirrigation can cause a significant loss of puncture strength in wood fiber and paper biocontainers over time (Koeser et al., 2013). Despite the reduction in container integrity, the use of ebb-and-flood irrigation may still be a viable option for conserving water in biocontainer greenhouse production, especially if containers are supported in plastic shuttle trays.
Although studies on the effects of reclaimed water on biocontainer greenhouse production are limited, the effects of container on ET, as well as drainage, have been more widely documented (Bilderback, and Fonteno, 1987; Evans and Karcher, 2004; Evans et al., 2010; Spomer, 1974). In comparing horticulture crops grown in peat, feather, and plastic containers watered uniformly across pot type, Evans and Hensley (2004) found that plants grown in plastic containers, which were impervious to water loss, had higher aboveground biomass than those grown in the peat- and feather-derived containers. However, when all container types were irrigated separately based on need, which resulted in more frequent water application to the peat and feather containers, growth in biocontainers was comparable and even superior to growth in a conventional plastic container depending on species grown (Evans and Hensley, 2004). Evans and Karcher (2004) found the volume of water required to grow a variety of crops was significantly lower in the plastic control as compared with those in the feather and peat containers. Similarly, more frequent watering was required for the peat and feather containers. This increased water demand corresponded with higher rates of water loss through the sides of the containers tested (Evans and Karcher, 2004). Evans et al. (2010) tested an expanded array of biocontainers to assess irrigation frequency and cumulative water demand. In doing so, the authors found that, with the exception of a relatively impermeable solid rice hull container, all biocontainer alternatives required more frequent irrigation and more overall water to maintain the minimum moisture level threshold.
Decreases in ET must coincide with unchanged or even increased plant growth to truly reduce water use in horticulture production (Fereres et al., 2003). As such, this project evaluates both plant dry shoot weight and cumulative water use at the end of the 5-week trial period. Our study expands on past efforts to assess water demand in biocontainers through the inclusion of a pair of newly marketed bioplastic alternatives, a bioplastic container, and bioplastic sleeve. In adopting biodegradable, plant-based plastics, container producers hope to emulate the advantages of petroleum-derived products (i.e., durability and imperviousness), whereas appealing to environmentally conscious consumers and growers. The insights gained from this work will better inform growers who need to reduce water use at their facilities and will ultimately contribute to future water-use models.
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