Agricultural land management alters the biogeochemical cycling capacity of aquatic and sediment environments

Abstract

Nutrient loading from agricultural landscapes continues to pose a threat to downstream aquatic systems, contributing to degraded water quality and eutrophication. Nutrient loading to adjacent aquatic environments is influenced by the type of applied fertilizer (chemical and manure), field management, and seasonal weather patterns. The risk these nutrients pose to downstream systems may be mitigated by the capacity of the microbial community in receiving water catchments to process those nutrients. This study evaluated the interactive effects of agricultural practices and seasonal weather patterns on nutrient cycling communities in catchment ponds within a long-term Agriculture and Agri-Food Canada research trial, located in the Lake Erie watershed in Ontario, Canada. Microbial nitrogen (N) and P (phosphorus)-cycling functions in water and sediment environments, receiving direct tile drainage and surface runoff flow, were quantified with respect to nutrient loads from liquid cow manure, solid cow manure, inorganic phosphorus, and a control fertilizer treatment, over a full year. High bacterial nitrification potential in the water column coincided with nitrogen loading, which was driven by manure/fertilizer application, tillage practices, and precipitation. The highest overall phosphorus concentrations occurred in the liquid cow manure treatment, but the availability of phosphorus in all treatments was strongly associated with microbial phosphorus mobilization capacity in both aquatic and sediment environments. Seasonality also influenced the aquatic environment, where N and P- cycling potential significantly increased during the winter months. Microbial functional potential in the water column was strongly influenced by the external environment, including season and precipitation, while the functional potential in the sediment was more resistant to environmental fluctuations, and was primarily influenced by long-term management fertilizer/manure practices. Overall, this study provides evidence that agricultural management alters the capacity of the microbial communities in adjacent aquatic environments to process nutrients.