Macronutrients and metals released from soils by solutions of naturally occurring phenols. Issue 5 (11th August 2017)

• Record Type: Journal Article
• Authors: Schmidt, Michael A.; Halvorson, Jonathan J.; Hagerman, Ann E.; Gonzalez, Javier M.
• Is Part Of: Journal of plant nutrition and soil science. Volume 180:Issue 5(2017:Oct.)
• Page Start: 544
• Page End: 553
• Publication Date: 2017-08-11
• Subjects: chelation -- nutrient -- metal -- polyphenol -- soil fertility; Plants -- Nutrition -- Periodicals; Soil science -- Periodicals; 630
• DOI: 10.1002/jpln.201700144
• Languages: English
• ISSNs: 1436-8730

Abstract

Abstract: Phenolic compounds produced by plants enter the soil by leaching and litter decomposition. The goal of this work is to determine the effect of phenolic compounds on solubility of plant macronutrients and metals in agroforestry systems. Soils from forest and pasture systems were repeatedly extracted with water (control) or phenolic solutions and then compared to a Mehlich 3 reference. The phenolics were aqueous solutions of tannic acid or β –1, 2, 3, 4, 6‐penta‐ O ‐galloyl‐D‐glucose (PGG) (hydrolyzable tannins), procyanidin (condensed tannin), or small phenolics catechin, gallic acid, or methyl gallate. The concentration of the macronutrients Ca, Mg, K, P, and S, and the metals Fe, Al, Mn, and Zn in the supernatants was determined by inductively‐coupled plasma spectroscopy. Cumulative extraction of macronutrients was generally similar to or less than the amount obtained by the Mehlich 3 extraction with the lowest recoveries obtained with the water control, PGG, and procyanidin. Metals tended to be somewhat more extractable from forest soil, especially with gallic acid, tannic acid or PGG treatments. Three mechanisms affected extraction of analytes by phenol‐containing solutions: (1) pH‐driven dissolution (Ca and Mg), (2) chelation of the metal (Al) by the polyphenol, or (3) reduction of the metal (Fe and Mn). Relatively low extraction of nutrients by some polyphenols is attributed to the tendency of some phenols to sorb to soil. This study demonstrates that tannins and related compounds change the solubility of macronutrients and metals in soils by a complex process that is not easily predictable from simple chemical properties of the phenolics.