Title: Retention of tannin-C is associated with decreased soluble-N and increased cation exchange capacity in a broad range of soils Authors
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 2, 2013
Publication Date: July 15, 2013
Citation: Halvorson, J.J., Gonzalez, J.M., Hagerman, A.E. 2013. Retention of tannin-C is associated with decreased soluble-N and increased cation exchange capacity in a broad range of soils. Soil Science Society of America Journal. 77:1199-1213. Interpretive Summary: Limited studies indicate plant compounds, called tannins, can be retained by soil and affect nutrient cycling and fertility. However, tannin effects have been studied in only a few soils. We added solutions of tannins and related non-tannin phenolic compounds to samples of surface soil gathered from locations through the United States and one Canadian province, and measured how they affected carbon (C) retention, soluble nitrogen (N), and cation exchange capacity (CEC), a common indicator of soil fertility. Meaningful amounts of each phenolic compound were retained by a wide variety of soils, with the amount of retention related the amount of total C in soil. Soils from the central and western U.S. and eastern Canada retained the greatest amount of treatment-C, while soils from the southeast U.S. retained the least. All treatments decreased extraction of soluble-N in soils from arid regions of the western U.S. With the exception of one non-tannin phenolic compound (i.e., gallic acid), reduced N-solubility was linearly related to retention of treatment-C and varied by soil type. In general, non-tannin phenolic compounds had little impact on soil CEC while tannins resulted in net increases. Increases in CEC, which were linearly related to retained treatment-C, were most strongly demonstrated in western U.S. soils. This study showed tannins exhibit short-term effects on soil properties associated with soil quality and function on a broad range of soil types.
Technical Abstract: 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.