Biochar additions to soils can improve soil-water storage capability; however, there is sparse information identifying feedstocks and pyrolysis conditions that maximize this improvement. Nine biochars were pyrolyzed from five feedstocks at two temperatures, and their physical and chemical properties were characterized. Biochars were mixed at 2% wt wt−1 into a Norfolk loamy sand (Fine-loamy, kaolinitic, thermic Typic Kandiudult), a Declo silt loam (Coarse-loamy, mixed, superactive, mesic xeric Haplocalcid), or a Warden silt loam (Coarse-silty, mixed, superactive, mesic xeric Haplocambid). Untreated soils served as controls. Soils were laboratory incubated in pots for 127 days and were leached about every 30 days with deionized water. Soil bulk densities were measured before each leaching event. For 6 days thereafter, pot-holding capacities (PHC) for water were determined gravimetrically and were used as a surrogate for soil-moisture contents. Water tension curves were also measured on the biochar-treated and untreated Norfolk soil. Biochar surface area, surface tension, ash, C, and Si contents, in general, increased when produced under higher pyrolytic temperatures (≥500°C). Both switchgrass biochars caused the most significant water PHC improvements in the Norfolk, Declo, and Warden soils compared with the controls. Norfolk soil-water tension results at 5 and 60 kPa corroborated that biochar from switchgrass caused the most significant moisture storage improvements. Significant correlation occurred between the PHC for water with soil bulk densities. In general, biochar amendments enhanced the moisture storage capacity of Ultisols and Aridisols, but the effect varied with feedstock selection and pyrolysis temperature.
1U.S. Department of Agriculture, Agricultural Research Service, Coastal Plains Research Center, Florence, South Carolina, USA.
2USDOE-Chemical and Materials Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA.
3U.S. Department of Agriculture, Agricultural Research Service, Northwest Irrigation and Soils Research Laboratory, Kimberly, Idaho, USA.
4U.S. Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, Louisana, USA.
5Biological and Agricultural Engineering Department, University of Georgia, Athens, Georgia, USA.
6Interdisciplinary Energy and Environment Program, North Carolina Agriculture and Technical State University, Greensboro, North Carolina, USA.
7U.S. Department of Agriculture, Agricultural Research Service, James P. Campbell Natural Resources Research Center, Watkinsville, Georgia, USA.
Address for correspondence: Dr. Jeffrey M. Novak, U.S. Department of Agriculture, Agricultural Research Service, Coastal Plains Research Center, 2611 W. Lucas Street, Florence, SC, USA. E-mail: firstname.lastname@example.org
Financial Disclosures/Conflicts of Interest: None reported.
Received June 9, 2011.
Accepted for publication January 23, 2012.
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