Do Plant Secondary Metabolite‐Containing Forages Influence Soil Processes in Pasture Systems?

Authors

Andrea K. Clemensen, Utah State UniversityFollow
Juan J. Villalba, Utah State UniversityFollow
George E. Rottinghaus, University of Missouri
Stephen T. Lee, USDA ARS Poisonous Plant Research LaboratoryFollow
Frederick D. Provenza, Utah State UniversityFollow
Jennifer R. Reeve, Utah State UniversityFollow

Document Type

Article

Journal/Book Title/Conference

Agronomy Journal

Publisher

John Wiley & Sons, Inc.

Publication Date

7-17-2020

First Page

1

Last Page

14

Creative Commons License

This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Abstract

Grazed pastures are susceptible to N loss from urine/manure additions, which increases eutrophication, affecting the global N cycle. Plant secondary metabolites (PSM), such as condensed tannins (CT) and terpenes, influence silviculture soil dynamics by generally decreasing N mineralization. We investigated whether cattle‐grazed pastures of non‐traditional grass and legume forage monoculture strips including CT‐containing sainfoin (Onobrychis viciifolia Scop.) and tall fescue (TF) [Schedonorus arundinaceus (Schreb.) Dumort.] influenced soil dynamics compared with traditional grass and legume forage monoculture strips of alfalfa (Medicago sativa L.), without tannins, and TF. Throughout the study, CT in sainfoin averaged 58.9 g kg⁻¹ whereas alfalfa saponins averaged 5.7 g kg⁻¹. We observed greater soil microbial respiration (p = .01) in TF strips than legume strips, indicating greater microbial activity, and between legumes we found greater soil NO₃ (p = .01) in alfalfa than in sainfoin, although aboveground biomass and N differences were negligible. We also conducted a laboratory soil‐feces incubation study to determine if feces from cattle foraging diets of legumes with or without CT influenced soil dynamics. Both feces treatments showed lower NO₃ (p < .001) than without feces, suggesting microbial inhibition. Dehydrogenase activity (DHEA) was lower (p = .03) in sainfoin than alfalfa feces, suggesting CT from sainfoin inhibit DHEA. To our knowledge this study is the first considering whether CT‐containing sainfoin and saponin‐containing alfalfa influence soil dynamics by assessing general differences in soil parameters. More research is needed to determine whether specific PSM mitigate N loss in pasture systems by slowing N mineralization.

Recommended Citation

Clemensen AK, Villalba JJ, Rottinghaus GE, Lee ST, Provenza FD, Reeve JR. Do plant secondary metabolite-containing forages influence soil processes in pasture systems? Agronomy Journal. 2020;1–14. https://doi.org/10.1002/agj2.20361