Book Description

Studies were conducted to evaluate the potential of sweet sorghum as a fuel ethanol feedstock for the southern coastal plain. Several cultural aspects were studied and a methol for rapid evaluation of the fermentable sugar concentrtions in the stalks was developed. The major findings of the studies were. 1. Wray, M81E, and MN1500 were the highest yielding early, medium, and late-maturing cultivars tested. Because of its high sugar concentration and resistance to lodging, Wray was the best single cultivar. 2. On the better agricultural soils of the area, the yield potential is five to six metric tons of total sugars per hectare. 3. The best planting time is in early May. Yields are reduced in plantings after mid-May because of early maturity and damage from the fall armyworm (Spodoptera frugiperda (J.E. Smith). The best harvest time is at the soft, to hard-dough stages of the seed. To maintain a constant supply of high-yielding sweet sorghum for a fuel ethanol plant, it was demonstrated the combinations of cultivars, planting dates, and harvest stages resulted in 95% of maximum sugar yield over a four-month period. 5. Nutrient requirements for sweet sorghum were low in comparisons to corn. No response to P or K was found when the soil test was high or medium for the elements, respectively. For a medium P soil test, yield responses were obtained to at least 25 kg P/ha. For a low K test, response was obtained to 186 kg K/ha. Response was obtained to about 100 kg N/ha. The N application should be split, with about one-half to two-thirds applied as a sidedressing when the sorghum is 30 to 60 cm high. No response was found to a 10-34-0 starter fertilizer, but the P soil test was high in this study. 6. The actual removal of nutrients by a sweet sorghum crop was determined to be 1,5 kg/MT fresh stalks for N, 0.3 for P, 1.8 for K, 0,6 for Ca and 0,3 for Mg. 7. No yield advantage was found in decreasing the row sapcing from 90 cm nor was there as advantage to increasing the population above 75 thousand plants per hectare. 8. The best control of annual grasses was obtained with a propazine plus metolachlor treatment. 9. No positive responses were found to the application of several growth regulators. 10. As automated analysis for determining the concentrations of total sugars in fresh or frozen sweet sorghum stalks was developed using an AutoAnalyzer II.