Investigation of management strategies for the production of sweet sorghum as a bioenergy crop and preservation of crop residue by the ensiling process

Abstract

In recent years, biofuels have become a national priority as demonstrated by the formation of the Renewable Fuels Standard. 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 in order to meet the mandated production of advanced biofuels. 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 growth, biomass yield, and chemical composition of ‘Top 766’ sweet sorghum were evaluated. 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 in the years 2005 and 2006. All treatments were in factorial combination and replicated four times in a randomized complete block design (RCBD). Nitrogen fertilizer treatments of 84 and 168 kg N/ha were applied as strip-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 second planting date in 20-cm row widths. Seeding rate and nitrogen fertility had no significant effects on biomass yield. Under these management conditions, dry matter yields of 20.9 Mg/ha and 37.1 Mg/ha were obtained in 2005 and 2006, respectively. Average dry matter yield, for this two-year period, was 29.0 Mg/ha. Given these results, sweet sorghum, when managed as a bioenergy crop in Iowa, has the potential of substantial biomass yields.