Turfgrass species can be classified into two main groups: cool-season and warm-season species. Because of their different physiology, warm-season species need less water to produce the same dry matter weight, thus they are more suited to Mediterranean climates (Croce et al., 2004; Turgeon, 2012; Volterrani and De Bertoldi, 2012) and have superior wear resistance and recovery compared with cool-season turf species (Lulli et al., 2012).
Transplanting single-potted plants is an innovative technique developed in Italy to convert cool-season to warm-season turfgrasses (Volterrani et al., 2008). Transplanting is based on the quick groundcovering capacity by stolons and rhizomes of small turf plants grown in a nursery garden. Transplanting can be accomplished manually or mechanically, in untilled soil, and is significantly cheaper than sodding. Although transplanting is efficient in converting a cool-season turfgrass to a warm-season turfgrass when soil tillage is not performed, the previous turf has to be completely desiccated.
Desiccation is usually achieved with chemical methods, such as herbicides, and the most common active ingredients are glyphosate and glufosinate ammonium (Baldi et al., 2013; Del Viva, 2012; Volterrani et al., 2008). However, clause 16 of EU Directive 2009/128/CE strongly discourages or prohibits the use of chemical herbicides, such as glyphosate, in public gardens, parks, sport turfs, and schoolyards. As a possible alternative, turfgrass can also be desiccated using flaming and steaming as an alternative to chemical weed control in organic/integrated farming and urban hard surfaces (Bàrberi et al., 2009; Peruzzi et al., 2011, 2012; Raffaelli et al., 2013, 2016).
Weeds and turfgrass species respond differently to physical treatments depending on their particular characteristics. Grasses (Gramineae) are monocots. Monocots have evolved to develop meristems protected by several leaf sheets (Baldoin et al., 2010), whereas dicots usually have all their meristems above the ground and widely over the plant. Grass turf species are less sensitive than most dicots to physical desiccation because they grow back from the protected meristems after the treatment unlike many dicots (Melander et al., 2009; Ulloa et al., 2010a). Rask et al. (2012) found that grass turf species, such as perennial ryegrass, are difficult to control with physical methods because the parts affected are mainly above the ground. Several authors have tested the effects on sensitive species of a single treatment with different flaming doses (Ascard, 1995; Ulloa et al., 2010a, 2010b) and steaming doses (Hansson and Ascard, 2002). However, there is still very little understanding concerning the effects of such techniques on less sensitive species such as grass turf species (Rask et al., 2012). Rask and Kristoffersen (2007) suggest that more than one treatment is required to efficiently desiccate grass turf species using flaming and steaming because otherwise they recover. Flaming can also be used as an effective weed control method before turfgrass establishment (Hoyle et al., 2012).
Alternative methods to flaming and steaming have been applied and tested over the years to desiccate vegetation using physical techniques. Hansson and Ascard (2002) experimented with the use of hot water to control weeds growing in hard surfaces. Sartorato et al. (2006) applied microwaves for postemergence weed control. However, flaming is still the most frequently applied physical method to desiccate vegetation. Steaming has been described by various authors as a valid alternative to flaming (Hansson and Ascard, 2002; Kerpauskas et al., 2006) and several agricultural machines for steam application have been developed (Gay et al., 2010a, 2010b; Langshaw, 1995).
The aim of this study was to compare flaming and steaming, performed by dedicated prototype equipment, with a glufosinate-ammonium herbicide treatment to desiccate cool-season turfgrass for conversion to warm-season turfgrass in untilled soil using transplanting.
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