Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 21, 2010
Publication Date: January 20, 2011
Repository URL: http://hdl.handle.net/10113/50157
Citation: Glaz, B.S., Shine, J.M., Irey, M.S., Perdomo, R., Powell, G., Comstock, J.C. 2011. Fiber Content of Three Sugarcane Cultivars in Three Crop Cycles on Sand and Muck Soils. Agronomy J. 103:211-220. Interpretive Summary: Florida produces more sugar than any other state in the U.S. A cooperative (USDA-ARS, University of Florida/Institute of Food and Agricultural Sciences, and Florida Sugar Cane League) variety development program in Florida develops more than 90% of the sugarcane varieties used in Florida. Scientists were concerned that, due to limited resources, estimates of fiber content of newly released varieties were inadequate. Fiber estimates have been based on samples taken primarily in February and March from the plant-cane crop cycle on organic (muck) soils. However, in addition to the 80% of sugarcane grown on muck soils, 20% of Florida sugarcane is also grown on sand soils, and expectations are that this percentage will increase. Also, sugarcane is usually harvested as first and second ratoon in addition to plant cane, and the Florida harvest season extends from October through March (recently into April). Because fiber content has major positive and negative economic implications on the sugarcane milling process, accurate estimates are needed for all varieties on both soil types in all crop cycles throughout the harvest season. This 2-year field study tested the effects of sample date and crop cycle on the fiber content of three sugarcane cultivars growing on sand and organic (muck) soils in Florida. From September through February, beginning in September 2007 and ending in February 2009, two stalks were cut from three replications of field plots of sugarcane varieties CP 72-2086, CP 78-1628, and CP 89-2143 in the plant-cane, first-ratoon, and second-ratoon crop cycles at locations with sand and muck soils. The 2-stalk samples were brought to the USDA-ARS Sugarcane Field Station at Canal Point, FL where leaves and foreign materials were removed before the stalks were shredded. Three 100-g samples of shredded cane were washed in a washing machine to remove soluble solids and then dried and weighed to estimate fiber content. Generally, our results corroborated previous results for these three varieties; CP 78-1628 had the highest fiber content, CP 89-2143 was next, and fiber content of CP 72-2086 was the lowest. However, the major finding of this study was that overall mean estimates of fiber contents did not provide sufficient information. Each variety responded differently to crop cycle and sampling date, and results on the sand soil and muck soils differed. Also, there were no clearly identifiable trends that allowed accurate predictions of seasonal fiber content for any of the varieties; rather there were many unexplained changes in relationships among varieties and sample dates. This new information indicates that the Florida variety development program needs a much more robust program to estimate fiber content of its promising varieties as well as for varieties that are used as parents. In addition, it was recommended that commercial sugarcane mills analyze fiber content throughout the harvest season rather than rely on overall mean fiber values provided by the cooperative variety development program when varieties are released.
Technical Abstract: Accurate seasonal estimates of fiber are needed to maximize profits whether producing sugarcane (Saccharum spp.) for sucrose or ethanol. The main purpose of this study was to determine the effects of sample date and crop cycle on fiber content of three sugarcane cultivars growing on sand and organic (muck) soils, and secondarily to determine if useful estimates of fiber could be measured 1 month prior to the beginning of the harvest season. From September through February, from 2007-2009, fiber content was estimated from monthly sampled stripped stalks of cultivars CP 72-2086, CP 78-1628, and CP 89-2143 growing in three replications of field plots in the plant-cane, first-ratoon, and second-ratoon crop cycles on Pompano fine sand (Siliceous, hyperthermic Typic Psammaquent) or Margate sand (Siliceous, hyperthermic Mollic Psammaquent), and Torry muck (euic, hyperthermic Typic Haplosaprist) soils. Fiber content generally had significant linear and/or quadratic responses to sample date. On sand soils, the cultivar rankings were often similar to expectations based on published fiber contents of these cultivars, with fiber content of CP 78-1628 > CP 89-2143 > CP 72-2086. On muck soils, CP 78-1628 fiber content was high, but differences between CP 72-2086 and CP 89-2143 were not consistent. For all soils, overall means were often not indicative of fiber status due to significant, but inconsistent interactions. Researchers should analyze fiber content whenever they analyze sucrose content, and mills should monitor fiber content daily of unique cultivar x crop cycle x soil deliveries.