Sediment and runoff water characteristics as influenced by cropping and tillage practices

Rainfall simulation by sprinkler irrigation was used to evaluate the characteristics of sediment and runoff water from erosion plots on a Dark Brown Chernozemic soil near Lethbridge, Alberta. Replicated land treatments consisted of bare fallow, perennial alfalfa/wheat grass forage (Medicago sativa L./Agropyron riparium Scribn. & Smith) planted in rows parallel to the slope, barley (Hordeum vulgare L.) planted in rows parallel to the slope (barley-S) and barley on contour (barley-C). The eroded sediment from all four treatments was generally enriched in organic matter (OM), NH 4 -N, total N (TN), and PO 4 -P, but not in NO 3 -N or total P (TP). The sediment from the bare fallow treatment was enriched in silt-size particles and had the highest OM enrichment. Maximum NH 4 -N and TN enrichment occurred in the sediment from the barley-S treatment, and maximum PO 4 -P in that from the forage treatment. This selective removal of plant nutrients was attributed mainly to erosion processes and to cropping-induced differences in C:N:P ratios of organic complexes. The runoff water from all four treatments was enriched in NO 3 -N, TN, and PO 4 -P. For the three cropping treatments in this experiment, nutrient enrichment of the runoff water decreased from forage > barley-S > barley-C treatment. In general, more NO 3 -N was lost in the runoff water than in the sediment. Key words: Erosion, sediment quality, water quality, nutrient loss, nitrogen forms, phosphorus forms.