Evaluation of Mangement Practices for Sweet Sorghum Grown as a Bioenergy Crop.

In recent years, biofuels have become a national priority as demonstrated by the enactment of the Energy Policy Act. In response, significant research has been directed toward identifying high-yielding bioenergy crops, breeding for improved biomass yield and quality, and developing management practices specific to bioenergy crop production. The objective of this project was to investigate management practices for sweet sorghum (Sorghum bicolor (L.) Moench) as a bioenergy crop in Iowa. The effects of planting date, seeding rate, row width, and nitrogen fertility on fermentable substrate yield of “Top 76-6” sweet sorghum were evaluated. Experiment plots were seeded on three dates; late May, early June, and late June, at rates of 4.5, 11.2, and 17.9 kg/ha with row widths of 20, 38, and 76 cm. All treatments were in factorial combination and replicated four times in a RCBD. Nitrogen fertilizer treatments of 84 and 168 kg N/ha were applied as split-plot treatments. Harvested plots were weighed for biomass yield and a subsample was collected for chemical analysis. Our results show that dry matter yields were maximized for the earliest planting date when seeded at 11.2 kg/ha in 20-cm row widths.  Nitrogen fertility had no significant effects on biomass yield. Under these management conditions, dry matter yields of 25.3 Mg/ha and 31.1 Mg/ha were obtained in 2005 and 2006, respectively. Average dry matter yield, for this two-year period, was 28.2 Mg/ha. Given these results, sweet sorghum, when managed as a bioenergy crop, has the potential of producing substantial biomass yields.