Conventional and Conservation Tillage: Influence on Seasonal Runoff, Sediment, and Nutrient Losses in the Canadian Prairies

• Published in: Journal of environmental quality 2010-05, Vol.39 (3), p.964-980
• Main Authors: Tiessen, K.H.D, Elliott, J.A, Yarotski, J, Lobb, D.A, Flaten, D.N, Glozier, N.E
• Format: Article
• Language: English
• Subjects: Agricultural land; Agricultural practices; agricultural runoff; agricultural watersheds; Agriculture - methods; Canada; Cold; Conservation tillage; conventional tillage; Crop residues; Crops, Agricultural; Dissolution; Environmental Monitoring; Environmental Pollutants; eutrophication; Exports; Geologic Sediments; International trade; losses from soil; nitrogen; Nitrogen - chemistry; Nutrient concentrations; Nutrient loss; Nutrient transport; Nutrients; phosphorus; Phosphorus - chemistry; Prairies; rain; Runoff; seasonal variation; Seasons; sediment transport; sediment yield; Sediments; Snowmelt; Soil conservation; Soil erosion; soil fertility; Soil surfaces; Tillage; Water - chemistry; water erosion; Water Movements; Water quality; Watersheds
• ISSN: 0047-2425; 1537-2537
• DOI: 10.2134/jeq2009.0219

Conservation tillage has been widely promoted to reduce sediment and nutrient transport from agricultural fields. However, the effect of conservation tillage on sediment and nutrient export in snowmelt-dominated climates is not well known. Therefore, a long-term paired watershed study was used to compare sediment and nutrient losses from a conventional and a conservation tillage watershed in the Northern Great Plains region of western Canada. During the treatment period, dissolved nutrient concentrations were typically greater during spring snowmelt than during summer rainfall events, whereas concentrations of sediment and particulate nutrients were greatest during rainfall events. However, because total runoff was dominated by snowmelt, most sediment and nutrient export occurred during snowmelt. Overall, conservation tillage reduced the export of sediment in runoff water by 65%. Similarly, concentrations and export of nitrogen were reduced by 41 and 68%, respectively, relative to conventional tillage. After conversion to conservation tillage, concentrations and exports of phosphorus (P) increased by 42 and 12%, respectively, with soluble P accounting for the majority of the exported P, especially during snowmelt. Our results suggest that management practices designed to improve water quality by reducing sediment and sediment-bound nutrient export from agricultural fields and watersheds can be less effective in cold, dry regions where nutrient export is primarily snowmelt driven and in the dissolved form. In these situations, it may be more appropriate to implement management practices that reduce the accumulation of nutrients in crop residues and the surface soil.