Effects of land application of municipal biosolids on nitrogen-fixing bacteria in agricultural soil

L. M. Holt^1,3, A. E. Laursen1,2, L. H. McCarthy^1,2, I. V. Bostan^1,2 and A. L. Spongberg⁴

Abstract
Effects of municipal biosolids on microbial N₂-fixation in agricultural soil were assessed in a 3-month laboratory study which included analysis of metals, pharmaceuticals, and personal care products. Reference agricultural soil was amended with organic manure or municipal biosolids from a southern Ontario wastewater plant, with a biosolids-only treatment included to evaluate metabolic activity in this inoculum.

Microbial N₂-fixation in reference and manure-amended soils were similar (p=0.144) over 3 months and lower than in biosolids-amended soil (p=0.001); however, differences among soil treatments decreased over time, with no significant difference at test termination. In general, one-time application of biosolids caused short-term stimulation of N₂-fixing activity with a return to reference conditions within 3 months.

Although no residual effects were detected, biosolids introduced elevated levels of metals, pharmaceuticals, personal care products (particularly analgesics), and viable bacteria; long-term effects caused by repeat applications (as commonly practiced) requires further investigation.


Source
Biology and Fertility of Soils (2010) 46: 407-413


Author Locations & Affiliations
(1) Environmental Applied Science and Management Program, Ryerson University, 350 Victoria Street, Toronto, ON, M5B 2K3, Canada
(2) Department of Chemistry and Biology, Ryerson University, 350 Victoria Street, Toronto, ON, M5B 2K3, Canada
(3) Golder Associates Ltd, 220-1755 Springfield Road, Kelowna, BC, V1Y 5V5, Canada
(4) Department of Environmental Sciences, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA


Posted April 2010