Reduction of soluble nitrogen and mobilization of plant nutrients in soils from U.S. northern Great Plains agroecosystems by phenolic compounds

Authors: Halvorson, Jonathan; SCHMIDT, MICHAEL - Wright State University; HAGERMAN, ANN - Miami University - Ohio; Gonzalez, Javier; Liebig, Mark

Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2015
Publication Date: 12/15/2015
Publication URL: http://handle.nal.usda.gov/10113/61875
Citation: Halvorson, J.J., Schmidt, M.A., Hagerman, A.E., Gonzalez, J.M., Liebig, M.A. 2015. Reduction of soluble nitrogen and mobilization of plant nutrients in soils from U.S. northern Great Plains agroecosystems by phenolic compounds. Soil Biology and Biochemistry. 94:211-221.

Interpretive Summary: Phenolic plant secondary metabolites actively participate in a broad range of important reactions that affect livestock, plants and soil. In soil, phenolic compounds can affect nutrient dynamics and mobility of metals but their role in northern Great Plains agroecosystems is largely unknown. We evaluated the effects of three phenolic compounds on plant nutrient extractability in agricultural soil. Soil samples (0-10 cm) from pasture and cropped sites near Mandan, North Dakota, USA were treated with water (control) or aqueous solutions of increasingly complex compounds including benzoic acid (BA), the simplest aromatic carboxylic acid, gallic acid (GA), a simple phenol, and PGG, a well-defined gallotannin at four concentrations. We measured extractable N, P, K, Ca, Mg and Mn in treatment supernatants and after a subsequent incubation in hot water. While significant quantities of nitrogen were extracted with water, each compound reduced N extracted in a concentration dependent manner with greatest response to BA (about 25%). However, PGG reduced the solubility of N only during the hot water incubation, suggesting its effects are mostly on organic forms of N. Unlike N, GA and PGG increased extraction of P, relative to water, while BA had less effect. Extraction of the major cations, K, Ca, and Mg, was strongly increased by BA and GA but unaffected by PGG. Extraction of Mn was increased most strongly by GA followed by BA and PGG. These findings suggest some plant secondary compounds affect nutrient dynamics in soil, and thus may be part of future management strategies to improve nutrient-use efficiency.

Technical Abstract: Phenolic plant secondary metabolites actively participate in a broad range of important reactions that affect livestock, plants and soil. In soil, phenolic compounds can affect nutrient dynamics and mobility of metals but their role in northern Great Plains agroecosystems is largely unknown. We evaluated the effects of three phenolic compounds on plant nutrient extractability in agricultural soil. Soil samples (0-10 cm) from pasture and cropped sites near Mandan, North Dakota, USA were treated with water (control) or aqueous solutions of increasingly complex compounds; benzoic acid (BA), gallic acid (GA), or ß-1,2,3,4,6-penta-O-galloyl-D-glucose (PGG) at four concentrations (1.25, 2.5, 5 or 10 mg compound gram-1 soil). We measured extractable N, P, K, Ca, Mg and Mn in treatment supernatants and after a subsequent incubation in hot water (16 h, 80°C). While significant quantities of nitrogen were extracted with water, each compound reduced N extracted in a concentration dependent manner with greatest response to BA (about 25%). However, PGG reduced the solubility of N only during the hot water incubation, suggesting its effects are mostly on organic forms of N. Unlike N, GA and PGG increased extraction of P, relative to water, while BA had less effect. Extraction of the major cations, K, Ca, and Mg, was strongly increased by BA and GA but unaffected by PGG. Extraction of Mn was increased most with treatments of GA followed by BA and PGG. These findings suggest plant secondary compounds affect nutrient dynamics in soil, and thus may be part of future management strategies to improve nutrient-use efficiency.