Effects of Nitrogen Fertilization on Biomass Yield and Quality in Large Fields of Established Switchgrass in Southern Iowa, USA

Switchgrass (Panicum virgatum L.) is a potential biofuel crop in the midwestern United States. The objective of this experiment was to test the effect of nitrogen application on biomass dry matter yield and fiber and mineral concentrations in large field plots in Lucas and Wayne counties in southern Iowa. Two established switchgrass fields with a previous history of limited management were evaluated from 1998 through 2002. Nitrogen was applied in the spring at rates of 0, 56, 112, and 224 kg N ha−1, and a single biomass harvest was made in autumn. Biomass production averaged across locations and N levels increased by 3.6 mg ha−1 between 1998 and 2002 to 6.5 mg ha−1. Nitrogen improved yields, with the response declining as N levels increased. The highest yield throughout the experiment was 8.5 mg ha−1 at the Lucas location in 2002. Changes in fiber and mineral concentrations did not follow any trend over years but were likely due to differences in harvest date among years. Nitrogen fertilization had no meaningful effect on the quality of the biofuel produced. This study clearly shows that nitrogen application and proper agronomic management can substantially increase the yield of established switchgrass fields over time without affecting the quality of the feedstock. As this experiment was conducted in large plots using commercial farm machinery, the results should be broadly applicable to real world situations

Munterville: A New Soil Series in Iowa

Before 2009, the Natural Resources Conservation Service (NRCS) staff noticed plant roots and argillans deep within the B horizon of Gosport polypedons (a fine, illitic, mesic Oxyaquic Dystrudept) while updating Major Land Resource Area (MLRA) 108 (Illinois and Iowa deep loess and drift) and 109 (Iowa and Missouri heavy till plain) in the central United States. In 2009, Gosport soils in MLRAs 108 and 109 were remapped and reclassified. Both map unit transects and the relevé method were used to identify pedons for detailed laboratory analyses. Eight pedons representing Gosport soils were collected from eight counties in southern Iowa, USA (Davis, Jefferson, Keokuk, Lucas, Mahaska, Marion, Monroe, and Van Buren). All of the pedons were described, analyzed, and classified. The results revealed two groups of soils, which are different than that of Gosport: Alfisols, newly named as the Munterville series (fine, mixed, smectitic or kaolinitic, active or superactive, mesic Oxyaquic Hapludalfs), and Ultisols (fine, mixed or kaolinitic, active, mesic Oxyaquic Hapludults) that have not yet been assigned a series name. The aims of this work were to reclassify the Gosport soils and detect the lithologic discontinuities within their sola