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Title: EVALUATION OF SWEET SORGHUM AS A COMPLEMENTARY BIOENERGY CROP TO SUGARCANE IN LOUISIANA

Author
item Tew, Thomas
item Cobill, Robert

Submitted to: American Society of Sugar Cane Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 5/16/2006
Publication Date: 6/20/2006
Citation: Tew, T.L., Cobill, R.M. 2006. Evaluation of sweet sorghum as a complementary bioenergy crop to sugarcane in Louisiana [abstract]. Journal of the American Society of Sugar Cane Technologists [serial online]. 26:57. Available: http://www.assct.org/journal/journal.htm

Interpretive Summary:

Technical Abstract: The potential of growing sweet sorghum (Sorghum bicolor) as a complementary energy crop in an integrated feedstock production system with sugarcane is being investigated. Sweet sorghum varieties M81E, Theis, and Topper were evaluated during 2002, 2003, and 2005. Seed of the selected varieties were drill-seeded in early May using two drills spaced 16 in. apart on top of a conventional 70-in sugarcane row. Experimental treatments were arranged in a randomized complete block design with four replications and plots consisting of a single row 72 ft. long. Sweet sorghum was sampled four times at 2-week intervals beginning in mid–July and ending in early–September. Each sample consisted of 10 hand-cut stalks with the leaves and, if present, the seed head removed. Estimated yields were calculated based on millable stalk counts made prior to initial July harvest dates. Sucrose, total hexose sugars, and fiber percentages were determined and estimates of total dry matter and ethanol from sugar yields were calculated. The effects of year, crop age, and variety on crop composition and overall yield were all important in this study. Estimated dry matter yield ranged from 4 to 12 tons/acre, and sugar:fiber ratios ranged from 30:70 to 50:50, depending on year, harvest date, and variety. Mean sugar yields of M81E, Theis and Topper were not significantly different from each other at the each harvest date in July, August or September. Average total hexose sugar yields for M81E, Theis and Topper was 3.9 tons/acre/year, enough to produce 500 gal ethanol per acre from sugars alone. We did not observe a yield plateau for sugar at the end of our experiment as expected, suggesting that additional yield can be expected, perhaps with earlier plantings or later harvests in September. The growing season for sugarcane in Louisiana is shorter than in any other cane growing area of the world. As a result, optimum cane sugar yields are generally obtained following late-October through December harvests. Results suggest that it may be possible to plant sweet sorghum during the spring and summer months on fallowed sugarcane fields for use as a complementary bio-fuel’s feedstock. The integration of these two crops should further assure a continuous supply of feedstock to the processor.