Polyethylene was developed as a film in 1938 and was produced on a commercial scale in 1939 (Lamont, 1993). The use of polyethylene plastic first as a cover for greenhouse structures and later as a mulch film for the production of vegetables was pioneered in the 1950s by the late Dr. Emery Emmert at the University of Kentucky (Emmert, 1957). Commercially, plastic mulches have been used for the production of vegetables since the 1960s (Lamont, 2005). Plastic mulches are an important management tool for modern vegetable production systems. Polyethylene mulches are used for vegetable production because they improve earliness and crop yields through increased soil temperatures, reduced evaporation of soil water, reduced weed pressure, and improved produce quality (Lamont, 1993, 2005).
There are some disadvantages to plastic mulches. Disposal options are limited. Plastic mulches are typically landfilled, burned, or disposed of illegally. Although recycling may be an option, polyethylene mulches used in vegetable production are contaminated with too much dirt and debris to be recycled directly from the field (Hemphill, 1993). Polyethylene mulches contain nearly as much potential energy per unit weight as oil (20,000 Btu/lb) and could be incinerated to produce heat or electricity (American Society for Plasticulture, 1991; Hemphill, 1993; Lamont, 2005). However, most power plants and incinerators are not designed to burn dirt- and debris-covered plastic, and operators are reluctant to make attempts to do so (J. Wilhoit, personal communication). Researchers at The Pennsylvania State University have tested “fuel nuggets” made of compressed plastic mulches to be used as a supplemental fuel in coal fired burners (Garthe et al., 2003). An alternative solution for reducing waste from polyethylene mulches is to develop photodegradable or biodegradable mulches (Sorkin, 2006).
Photodegradable mulch films have been tested intermittently for more than 20 years (Hemphill, 1993). Results have been variable, with many films degrading prematurely (Greer and Dole, 2003; Halley et al., 2001). Furthermore, the ability of photodegradable mulches, which are manufactured with petroleum-based ingredients, to degrade into carbon dioxide and water has been questioned (Zhang et al., 2008).
Paper-based mulches have been used in agriculture since 1914, when paper was used to reduce weed pressure in sugar cane (Saccharum officinarum) fields (Smith, 1931). Asphalt-impregnated paper mulches were successfully used in pineapple (Ananas comosus) production in the 1920s in Hawaii, increasing quality and yields (Smith, 1931). Paper mulches have since been evaluated with varying results. Newspaper mulches represent an available and cost-effective resource and have been frequently trialed (Shogren, 2000). Munn (1992) reported increased yields with shredded newspaper compared with straw mulches in corn (Zea mays) and soybean (Glycine max). Recently, Sanchez et al. (2008) reported success when using shredded newspapers as a weed-suppressing mulch in organic high-tunnel cucumber (Cucumis sativus) production. However, some paper mulches deteriorate rapidly under field conditions, reducing their effectiveness (Shogren, 2000). Several trials have used paper mulches with polyethylene, wax, or vegetable oil coatings used to slow degradation of mulches in the field (Miles et al., 2003; Shogren, 1999; Shogren and David, 2006; Vandenberg and Tiessen, 1972).
Growers interested in using paper mulch on a larger scale may want to lay mulch and drip irrigation tape with a conventional plastic layer and plant using a water wheel transplanter. Miles et al. (2006) used traditional mulch laying equipment, though hand transplanted, to test the performance of several starch- and paper-based mulches for organically managed lettuce (Lactuca sativa), broccoli (Brassica oleracea var. italica), bell pepper (Capsicum annuum), and watermelon (Citrullus lanatus) in the Pacific northwestern United States with variable results. In that trial, plastic-based mulches generally outperformed paper mulches; however, some of the plastic-based biodegradable products took longer to degrade than expected. Performance of paper mulches is likely to vary according to production region and management strategy. This trial was conducted to evaluate the performance of four readily obtainable papers compared with traditional black plastic with a short, warm-season crop (yellow squash) in the midsouthern United States using conventional plastic laying equipment and a water wheel transplanter for two growing seasons.
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