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SOIL AGGREGATE PROPERTIES AND ORGANIC CARBON FOR SWITCHGRASS AND TRADITIONAL AGRICULTURAL SYSTEMS IN THE SOUTHEASTERN UNITED STATES

Blanco-Canqui, Humberto1; Lal, Rattan1; Lemus, Roque2

doi: 10.1097/01.ss.0000187342.07331.a6
Technical Articles

Switchgrass (Panicum virgatum L.), a potential biofuel crop, can sequester soil organic carbon (SOC) and improve soil quality. However, its influence on soil aggregate mechanical properties controlling the macro-scale behavior of the whole soil needs to be assessed to understand processes that affect soil quality. This study assessed the impact of long-term (>10 years) switchgrass, row crop, cool season grass pasture, and forest management on properties of soil aggregates for five ecosystems in the southeastern United States, including Blacksburg and Orange (VA), Knoxville (TN), Morgantown (WV), and Raleigh (NC). Relationships among aggregate properties were also determined. Tensile strength (TS), bulk density (ρagg), soil moisture retention (SMR), and SOC concentration of 1- to 8-mm aggregates were determined at the 0-to 10-cm and 10- to 20-cm soil depths. Management significantly affected the aggregate properties (P < 0.05), but the magnitude of the effects was site-dependent. The TS for switchgrass was the lowest (∼271 kPa) at all but the Blacksburg site for the 0- to 10-cm depth. The ρagg for switchgrass was 10% lower at Blacksburg and 20% lower at Orange than that for row crop at the 0- to 10-cm depth. The SOC concentration for switchgrass was 2.5 times higher than that for row crop at Orange but not at Blacksburg. The TS increased with increasing ρagg at Morgantown and Raleigh, but it decreased with increasing aggregate size at all sites. Aggregate size, ρagg, and SOC were significant predictors of TS. Long-term switchgrass systems in the southeastern United States improve the aggregate strength properties, unlike row crop and cool season grass pastures, but their impact on SOC concentration is variable.

1Carbon Management and Sequestration Center, School of Natural Resources, The Ohio State University, 210 Kottman Hall, 2021 Coffey Rd., Columbus, OH 43210-1085. Dr. Blanco-Canqui is corresponding author. E-mail: blanco.16@osu.edu

2Department of Agricultural Sciences, Texas A & M University-Commerce, Commerce, TX 75429-3011.

Received Feb. 25, 2005; accepted June 23, 2005.

© 2005 Lippincott Williams & Wilkins, Inc.