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Retention of tannin-C is associated with decreaesd soluble nitrogen and increased cation exchange capacity in a broad range of soils

Halvorson, Jonathan J., Gonzalez, Javier M., Hagerman, Ann E.
Soil Science Society of America journal 2013 v.77 no.4 pp. 1199
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 plant compounds, called tannins, can be retained by soil and affect nutrient cycling but have been studied in only a few soils. Soils (0-10 cm) from locations across the United States and Canada were treated with water (Control) or solutions containing procyanidin, catechin, tannic acid, ß-1,2,3,4,6-pentagalloyl-O-D-glucose (PGG), gallic acid, or methyl gallate. We measured soluble-C and –N in treatment supernatants and after a subsequent incubation in hot water (16 h, 80 °C) and determined changes to total soil-C and CEC. Final treatment retention, greatest for PGG > tannic acid >procyanidin > catechin > methyl gallate > gallic acid, was supported by net measurements of total soil-C also varied by soil order. Alfisols, Aridisols and Mollisols retained the most treatment-C while Ultisols retained the least. Differences among soil orders were detected only for strongly retained compounds. Generally, cumulative soluble-N was decreased by gallic acid and tannins, especially PGG, but unchanged by methyl gallate or catechin. However, soluble-N was decreased by all treatments in Aridisols and unaffected by treatment in Entisols. In general, non-tannin phenolic compounds had little impact on soil CEC while tannins resulted in net increases. Treatment effects on CEC were small and did not vary in Ultisols. Further, PGG increased CEC more in Aridisols than in Mollisols or Ultisols. This study shows tannins produce effects, associated with soil quality and function, on a broad range of soil types. Their initial retention in the soil, together with associated decreases of soluble-N and increased CEC suggests tannins may be part of management strategies.