Invasive species pose a threat to plant and wildlife communities worldwide and are now considered to be a major detrimental factor of global change (Sakai et al., 2001). Exotic invasive aquatic species negatively impact local biodiversity, nutrients, light and oxygen availability, native shoreline vegetation, and human recreation and activity (Florida Exotic Pest Plant Council, 2017; Reichard and White 2001). Invasive traits include the ability to reproduce asexually, competitive ability, rapid maturity rates, adaption to environmental stresses, and having an additional advantage of being connected to waterways allowing rapid spread after flooding events and/or human activity (Florida Exotic Pest Plant Council, 2013; Sakai et al., 2001). Public and private spending to prevent, control, or eliminate exotic invasive species was estimated to exceed $100 million each year (Masser, 2007; Simberloff, 2003; U.S. Fish and Wildlife Service, 2012).
Indigenous to the New Guinea and Oceania regions, wild taro is an ancient crop used at the time of the earliest agricultural practices (Fullagar et al., 2005; Matthews, 2003). It was first introduced into Florida by the U.S. Department of Agriculture and other southern states as a potential substitute for potato (Solanum tuberosum) in 1910 (Atkins and Williamson, 2008; Langeland and Craddock Burks, 1998). From 1914 to 1924, the Texas Agricultural Experiment Station in Angleton experimented using taro as a potato replacement (Kimmel, 2006). The plant remains a commercially important food crop where the leaves, petioles, and roots are used and prepared in a variety of ways in cultures around the world. Taro is considered a dietary staple by some due to its high nutritional value (Manner and Taylor, 2011).
Ornamental cultivars of wild taro are also a valuable crop in the United States and around the world with species grown in Florida having, in part, an estimated overall horticultural economic value of $45 million (Wirth et al., 2004). New ornamental cultivars and closely related species of plants have been developed, described, used, and bred for the floriculture and nursery trade (Cao and Long, 2003; Pereira et al., 2005). Ornamental propagation of plants is often done using micropropagation (Adelberg and Toler, 2004). However, Manner and Taylor (2011) noted that wild taro was commercially produced in Hawaii “from mature (rhizomes) and consist(ed) of the top 1 cm of the rhizome and about 20 to 50 cm of the petiole.”
In the southeastern United States, as well as in Puerto Rico, Jamaica, and India, wild taro is identified as an invasive exotic ornamental species in freshwater swamps, streambanks, and river bank areas (Atkins and Williamson, 2008; Bindu and Ramasamy, 2008; Early Detection and Distribution Mapping System, 2018; Everitt et al., 2007; Florida Exotic Pest Plant Council, 2017; Kurien and Ramasamy, 2006; Matthews, 2003). Extensive stands of wild taro live in a variety of riparian habitats and are superior competitors against native species (Atkins and Williamson, 2008; Gonzalez and Christoffersen, 2006). Plants prevent light from reaching submerged species below the leaf cover, increase the rates of evapotranspiration, and offer little value to local wildlife (Atkins and Williamson, 2008; Everitt et al., 2007). The presence of crystalized calcium oxalate in the leaves, stems, and root structures allow for no natural predation in the United States, increasing its ability to outcompete native species (Atkins and Williamson, 2008). Wild taro is often dispersed by purposeful or accidental spread of vegetation fragments (Atkins and Williamson, 2008; Gonzalez and Christoffersen, 2006). Chemical treatments currently used to manage wild taro can damage local ecosystems and are potentially less effective when compared with alternative means of management (Atkins and Williamson, 2008; Nelson and Getsinger, 2000).
Atkins and Williamson (2008) assessed four techniques for removal of invasive stands of wild taro to determine which process reduced the most organism biomass and resulted in the highest level of vegetative growth prevention. Methods included the use of glyphosate herbicide, mechanical cutting, manual removal, and a combination of mechanical cutting and herbicide use. Manual removal consisted of “hand pulling the entire plant, including the (rhizome), from the soil” and was the most effective method for wild taro harvesting and growth prevention (Atkins and Williamson, 2008). Proper disposal of harvested invasive plant parts is an important consideration because many invasive plants reproduce easily and successfully both sexually and asexually where any plant propagule could potentially produce new stands of plants (Florida Exotic Pest Plant Council, 2013).
Composting is a biomechanical process during which microorganisms such as bacteria and fungi convert organic matter into a waste-free, soil-like product (Epstein, 1997; Rynk, 1992). The mechanical manipulation increases the rate of decomposition that occurs in natural environments (Pennsylvania State University, 2012) and the process can take as little as 2 weeks to more than 1 year to complete, depending on the amount of human intervention, types of feedstocks used, and weather conditions (Epstein, 1997; Rynk, 1992). In addition, if high enough temperatures of 49 to 82 °C are reached during the active stage and sustained for a period (3 to 7 d), various types of weed seeds and additional propagules are killed (Meier et al., 2014; Montoya et al., 2013). Composting is increasingly used as a waste management method, a technique for pollution diversion, and a means to produce a valuable commodity for agricultural, horticultural, and related users (Walker et al., 2006). Composting is sometimes recommended as a means of managing invasive plant species waste if temperatures achieved in the composting process are hot enough and maintained for long enough periods (Florida Exotic Pest Plant Council, 2013).
The purpose of this study was to evaluate the potential to manage wild taro waste using composting and to test the quality of the resulting compost.
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