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TitleSoil processes mediate nitrogen flux from agricultural lands - evidence from stable isotope studies
AuthorSomers, G S; Savard, M MORCID logo
SourceProceedings of the 7th Canadian River Heritage Conference ; 2013 p. 1-12
Alt SeriesEarth Sciences Sector, Contribution Series 20130058
PublisherCanadian Rivers Heritage
MeetingCanadian Rivers Heritage Conference; Charlottetwon; CA; June 21-26, 2013
File formatpdf
ProvincePrince Edward Island
NTS11L; 21I/08; 21I/09; 21I/16
Lat/Long WENS -64.5000 -62.0000 47.0000 46.0000
Subjectssoils science; soils; soil surveys; soil studies; soil properties; soil morphology; nitrogen
Illustrationslocation maps; tables; plots
ProgramGroundwater Geoscience Program Management - Groundwater Geoscience
Released2013 01 01
AbstractIn Prince Edward Island, the discharge of nitrogen (N) rich groundwater to streams is believed to be largely responsible for the increasing frequency and severity of eutrophic conditions and anoxic events in local estuaries. Stable isotope results show seasonal variations in the provenance of N. They also suggest that mediation through the soil organic matter (SOM) pool (mineralization and nitrification) of N from a variety of sources (fertilizers, manures and crop residues) is the dominant process controlling nongrowing season leaching losses, which comprise the bulk of annual N losses from agricultural lands in the Province. At the watershed scale, nitrate in groundwater retains only slight hints of original N sources (i.e., manure or synthetic fertilizers), with most values falling in the range typically associated with soils. At the experimental scale, nitrate in tile drain effluents carried somewhat distinctive isotope characteristics for plots with fertilizers, manure and check plot treatments immediately following potato harvest, but converged to values characteristic of the SOM pool by the start of the subsequent growing season. Collectively, we suggest that practices that influence the rate of nitrification during the important non-growing season can play a key part in controlling N losses from agricultural sources. Split field trials in the Souris watershed are currently
testing the hypothesis that delaying ploughing of forage crops from fall to spring will reduce over winter nitrification of crop residues and N leaching, and leave more N available for subsequent crops. Preliminary results support the importance of tillage management in the development of strategies to reduce N losses from crop lands.
Summary(Plain Language Summary, not published)
High nitrate concentrations in groundwater unanimously attributed to agricultural activities on Prince-Edward-Island (PEI) represent a key issue for the managers of water resources. How is it possible to ensure the sustainable use of this sole source of drinkable water while agriculture is a key economic driver? This research work conducted by the Government of PEI with support from Agriculture and Agri-Food Canada and the collaboration of the Geological Survey of Canada allowed to highlight the importance of winter transfer of nitrogen excess from soils to aquifers, and the role of soil organic matter as temporary resevoir of nitrogen, in several study cases where the types of agriculture widely vary. Practical recommendations, such as delaying until spring the ploughing that usually takes place during fall, could favour a significant diminution of groundwater contamination in the Province.

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