Effect of tillage and irrigation on Southeastern US soils under cellulosic sorghum feedstock production

Sorghum may be a good cellulosic material for bioenergy production because it can be cultivated in current row-crop systems. However, the production of sorghum for bioenergy and its impacts on Southeastern U.S. soils should be investigated to determine the most environmentally sustainable system. The objective of this study was to evaluate tillage (conventional vs. conservation systems), and irrigation effect (irrigated vs. non-irrigated) on soil characteristics when producing cellulosic feedstock from three forage sorghums and one forage corn (control) in 2008 and 2009. Results showed that soil organic carbon (SOC) increased at a depth of 0.10-0.15 m, but decreased at a depth of 0.40-0.45 m with higher losses being found using conventional tillage as opposed to conservation tillage. Total nitrogen (TN) and bulk density (Bd) increased at all evaluated soil depths (0-0.50 m) after 2 years. Conventional tillage plots also showed higher Bd at 0.15-0.30 m. Higher Bd in conventional tillage plots might restrict water drainage which could explain higher volumetric soil water content (SWC) at 0.10, 0.20 and 0.40 m soil depths. Cone Index (CI) values also showed improved soil conditions at in-row positions for conservation plots.