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

Abstract

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.

Simulating cold-region hydrology in an intensively drained agricultural watershed in Manitoba, Canada, using the Cold Regions Hydrological Model

“…Muskingum routing within and between sub-basins of LS-05OG008 was set up according to Fang et al (2013). The storage parameter used in the Muskingum routing module was set to 0, based on the typical pattern observed for regional agricultural runoff monitoring where individual diurnal runoff events at edge-of-field begin as soon as melt starts around noon and stops due to refreezing at night (Tiessen et al, 2010). In-channel storage was calculated as total reach length (calculated in GIS using the drainage network) divided by average flow velocity, which was estimated using measured hydrographs and channel dimensions (i.e.…”

Managing agricultural phosphorus for water quality protection: principles for progress

“…Storm characteristics (intensity, duration) and antecedent conditions (especially soil moisture) all contribute to this variability, sometimes with sufficient regularity to allow meaningful management inferences. For instance, in the province of Manitoba, Canada, 80 to 90% of runoff occurs during spring-time snow-melt over frozen soils (Tiessen et al 2010). Adjusting annual P applications in this region to avoid application to frozen soils minimizes the potential for P wash-off.…”

Engineering solutions for food-energy-water systems: it is more than engineering

“…For example, no-till conservation has dramatically decreased erosion and associated P loss, although the loss of P in dissolved, more immediately reactive form without the incorporation of applied P can reverse total P gains and be sufficient to stimulate algal blooms (Richards et al 2010;Sharpley and Smith 1994;Tiessen et al 2010). Another trade-off resulting from the cultivation of new lands fueled by corn for bioethanol that is facilitated by tile drainage will directly connect new source areas to stream and ditches, indirectly increasing the potential for P loss (Smith et al 2014(Smith et al , 2015.…”