FIBER PROPERTIES OF SAW AND ROLLER GINNED NATURALLY COLORED COTTON

Naturally colored cottons have economic and environmental appeal because they do not require dyeing. Naturally colored cottons do not have the same fiber length and strength as white cotton cultivars. To determine the optimal ginning process for colored fiber two Upland (G. hirsutim) colors were roller and saw ginned following a complete block experimental design. HVI and AFIS analysis favored roller ginning. It resulted in 0.7 mm (1/32 in) greater HVI fiber lengths and 33% fewer AFIS fiber neps compared to saw ginning. This increase in fiber value may justify the higher cost of roller ginning. Introduction Naturally colored cottons have a long history, dating from 3400 to 2300 BC in Mexico, 3100 BC in Peru (with fibers from 12 to 43 mm (0.5 to 1.7 in) length), 2250 BC in Egypt (19 to 22 mm (0.75 to 0.87 in) and sometime before 1200 AD in China. Russian brown cottons from the past century had good strength but lint length averaged only 19.8 mm (0.78 in), with short fiber index a low 31.1%. Colored cottons also have a history of commerce; Peru exported twelve colors from 1865 to 1937, to English manufacturers, who blended them with wool. Russia offered for sale some 700 Mg (770 ton) naturally pigmented fiber in 1945 (Vreeland, 1993). Fiber quality and spinning tests of colored cottons enjoy a bit of history as well, with tests in the 1960s confirming data from the 1940s (Ware and Bennedict, 1962); that naturally colored cotton fibers ranged in length from 15.9 to 26.2 mm (0.63 to 1.03 in). Relative to white cottons, colored cottons were found to be weaker and shorter. Despite greater disease resistance and salt tolerance in some colored varieties, yield and lint content were lower (Conrad and Neely, 1943; Price et al., 2001). Although yields tend to be 50 to 70 percent lower than yields of conventionally grown white cotton, prices for organically grown naturally colored cotton have been higher. In 1996, organic, naturally colored brown commanded $4.06 to 7.39 kg ($1.84 to 3.35 lb) and green cotton ranged from $8.36 to 11.02 kg ($3.79 to 5.00 lb) (Katz et al., 1997). At that time base grade conventional white cottons were selling for $1.48 to 1.74 kg ($0.67 to 0.79 lb). There has been a recent resurgence of commercial interest in naturally colored cotton since it can be made into textiles without dyeing the yarn. Consumers wishing to reduce the environmental impact of clothing are attracted by this feature. Manufacturers are attracted by the savings since dyeing can represent about 15% of the cost of an apparel item (Nimon and Beghin, 1999). To improve colored cotton fiber properties for machine processing, breeding projects are in progress in Brazil, Greece, Israel, Peru, Turkey and the former Soviet Union (Matusiak et al., 2007). Research on spinning colored cottons is being conducted in Poland (Matusiak et al., 2007). This resurgence has, however, been a bumpy road. The production of naturally colored cottons in the United States was an estimated 1575 ha (4,000 acres) in 1992. The eco-fashion market for organic, naturally colored cotton peaked in 1993-1994, and by 1995, when world production had peaked at 11,670 Mg (12,864 tons), with 6,736 Mg (7,425 tons) grown in the U.S., many retailers had withdrawn from the market. By 1996 U.S. planting had fallen to approximately 20 hectares (50 acres) (Katz, et al., 1997). Nonetheless, production of naturally colored cotton that can be machine spun continues. Small quantities are sold to mills in Europe and Japan. The primary difficulty US producers face today is not marketing, but finding a gin willing to process their crop. States have passed legislation to protect white cotton from contamination (California Code of Regulations, 1997; Arizona Department of Agriculture, 2005). Most gin managers feel that the required notification, separation, cleanup and inspection costs far exceed the potential revenue from ginning a small batch of colored cotton. One solution may be to dedicate a gin to processing colored cotton exclusively; this may be feasible now as a number of gins are closing because of consolidations and reduced plantings. 1205 2009 Beltwide Cotton Conferences, San Antonio, Texas, January 5-8, 2009