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As a measure of a plants ability to convert solar energy into biomass, radiation use efficiency (RUE) can be used to compare species and genotypes within species. Despite considerable research on RUE of biofuel species, few reports on sweet sorghum ( Sorghum bicolor (L.) Moench.) RUE are available. Radiation use efficiency and biomass yield of four sweet sorghum genotypes (‘Dale’, ‘M 81E’, ‘Topper 76-6’, and ‘Sugar Drip’) was assessed in response to two late planting dates in a two-year study. The late planting dates would coincide with abandoning double-crop plantings of soybean following wheat. Aboveground biomass yield and RUE (g biomass MJ −1 intercepted photosynthetically active radiation (IPAR)) was measured every two weeks beginning four weeks after planting. Two estimates of RUE were calculated differing only in growth periods used (emergence to anthesis [EA] and during rapid linear growth [Max]). Biomass yields, EA, and Max RUE were similar between years and sorghum cultivars, but differed between planting dates. Early-July plantings resulted in greater RUE than mid-July plantings. Averaged across cultivars at the first planting date both years EA and Max RUE were 3.11 and 3.96 g MJ −1 IPAR, respectively, compared to 2.40 (EA RUE) and 2.79 g MJ −1 IPAR (Max RUE) at the second planting date. Mean biomass yield across years and cultivars was 10.67 and 8.63 Mg ha −1 at the first and second planting dates, respectively. These results confirm expected decreases in RUE and biomass production of late-planted sweet sorghum, but also illustrate that, even when planted late, sweet sorghum efficiently converts intercepted PAR to biomass. [ABSTRACT FROM AUTHOR]

Increasing demand for high-yielding, alternative biofuel feedstocks elicits the need to fully understand sweet sorghum ( Sorghum bicolor (L.) Moench) yield response to varying nitrogen (N) fertilization rates in the U.S. Midwest. The objective of this three-year study was to determine the optimum N fertilization rates for the production of two common sweet sorghum cultivars (Dale and Top 76-6) in central Missouri. Five N rates (0, 56, 112, 168, 224 kg N ha −1 ) were imposed and tested for their effects on dry matter yield, stem juice yield, Brix, fermentable sugar yield, theoretical juice ethanol yield, theoretical lignocellulosic ethanol yield, and total theoretical ethanol yield. Except for Brix, N treatment significantly influenced all yield parameters in all three years. The two varieties yielded similarly across most measured parameters. Total dry matter yields averaged 16.8 Mg ha −1 , juice yields averaged 9113 L ha −1 , and fermentable sugar yields averaged 1055 kg ha −1 across years and varieties. Total ethanol yields averaged 7488 L ha −1 and were highest at 168 kg N ha −1 across the three years, indicating that sweet sorghum in Missouri may reach maximum yields near that fertilization rate. Annual precipitation and temperature differences greatly influenced dry matter, stem juice, and sugar yields, thereby affecting theoretical ethanol yields, such that yields were lower in years with less rainfall and lower temperatures, which also limited the N response in these years. [ABSTRACT FROM AUTHOR]

Use of perennial bioenergy grasses would be enhanced if they produced sustainable ratoon crops across a wide geographic region. Our objective was to compare ratoon cold tolerance (defined as shoot emergence during the first-ratoon crop), and plant cane dry mass yield and feedstock quality [acid detergent lignin, cellulose, hemicellulose, total nonstructural carbohydrates (TNC), and combustible energy] of elephantgrass ( Pennisetum purpureum ), Old World Erianthus ( Saccharum arundinaceum , formerly E. arundinaceus , subsequently referred to as Erianthus ), and sugarcane ( Saccharum sp. hybrids). The experiment (Test 1) was conducted near Booneville, Arkansas (35.08°N latitude) and consisted of three varieties of elephantgrass and Erianthus , and six of sugarcane, evaluated in plant cane (first year growth, 2008) and first-ratoon (second year growth, 2009). The experiment was repeated in 2009–2010 (Test 2). Absolute minimum air temperatures were −12.7 and −17.3 °C in Test 1 and 2, respectively. Second-year emergence in Test 1 was in the order sugarcane = Erianthus (92%) > elephantgrass (25%). In Test 2, sugarcane and Erianthus had 63 and 3% second-year emergence, respectively, whereas elephantgrass shoots did not emerge. Elephantgrass had twice the plant cane yield of the other species. Feedstock quality was generally similar among species, although sugarcane had greater TNC (220 g kg −1 ) than other species (≤131 g kg −1 ). Poor ratooning of all 12 varieties would limit their use as perennial bioenergy feedstocks in similar environments, however, breeders using germplasm selected under these conditions could ultimately enhance ratoon cold tolerance of commercial sugarcane varieties for more southerly latitudes. [ABSTRACT FROM AUTHOR]

The U.S. Department of Energy has initiated efforts to decrease the nation’s dependence on imported oil by developing domestic renewable sources. In this study, giant miscanthus ( Miscanthus × giganteus), miscane ( Saccharum hybrid × Miscanthus spp.), and giant reed ( Arundo donax ) were grown on an upland site (35.08°N) to determine the potential of these perennial grasses as bioenergy feedstocks, with or without irrigation. Irrigated and rainfed plots with subplots of each species were planted on a silt loam, and biomass yields were assessed in plant-cane, first ratoon, and second ratoon seasons. In the establishment year, giant reed biomass yield was greater than that of giant miscanthus, but not significantly different from that of miscane. Biomass yields of giant reed continued to increase significantly with every season, while giant miscanthus yields only increased from plant-cane to first ratoon, and miscane yields did not change with season. The miscane clone did not have sufficient cold tolerance to ensure vigorous growth of ratoon crops at this latitude. Giant miscanthus had the smallest stalk diameter each season, and the largest leaf:stem ratio in the plant-cane and first ratoon seasons. Irrigation increased dry matter yield of giant reed in the plant-cane and first ratoon seasons, but not in the second ratoon season. In both ratoon seasons, giant reed produced the tallest stalks, largest stalk diameters, and the greatest stem, leaf, and total dry matter yields. Giant reed was the most productive of the three species despite growing on an upland site away from its usual lowland habitat. [ABSTRACT FROM AUTHOR]