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Retention of Tannin-C is Associated with Decreased Soluble Nitrogen and Increased Cation Exchange Capacity in a Broad Range of Soils

Jonathan J. Halvorson, Javier M. Gonzalez, Ann E. Hagerman
Soil Science Society of America journal 2013 v.77 no.4 pp. 1199-1213
Alfisols, Aridisols, Entisols, Mollisols, Ultisols, biogeochemical cycles, catechin, cation exchange capacity, gallic acid, nitrogen, procyanidins, soil organic carbon, soil quality, soil solution, tannins, Canada, United States
Phenolic compounds, called tannins, can be retained by soil and affect soluble N but have been studied in only a few soil types. Surface samples (0–10 cm), collected from the United States and Canada, were treated with water (Control) or solutions containing procyanidin, catechin, ß-1,2,3,4,6-pentagalloyl-O-D-glucose (PGG), tannic acid, gallic acid, or methyl gallate. Soluble C and N in treatment supernatants and after incubation (16 h, 80°C) were measured to determine retention of treatment C and effects on soluble N and cation exchange capacity (CEC). Retention varied significantly with treatment (T) and soil order (S) and was greatest for PGG > tannic acid > procyanidin > catechin > methyl gallate > gallic acid and in Alfisols, Aridisols and Mollisols compared Ultisols. However, differences among soil orders were observed only for strongly retained compounds (T × S, P < 0.001). Extraction of soluble N was decreased by gallic acid and tannins, especially PGG, but unaffected by methyl gallate or catechin. All treatments decreased soluble N from Aridisols while Entisols were less affected by tannins (T × S, P < 0.01). Soil CEC was significantly increased by tannins but unaffected by other compounds. However, CEC increased more in Aridisols than in Mollisols or Ultisols and treatment effects were small and unvarying in Ultisols (T × S, P < 0.001). Changes to both soluble N and CEC were linearly related with retention of treatment C. Tannins produced effects associated with improved soil quality on a broad range of soils and may have a role in land management.