Effects of deer grazing and fence‐line pacing on water and soil quality

Abstract

Abstract. We studied the effects of red deer grazing and fence‐line pacing on soil losses of contaminants (suspended sediment, Escherichia coli, phosphorus) and nitrogen species (ammonia, nitrate) via overland flow and soil physical properties (macroporosity, bulk density, saturated hydraulic conductivity, Ksat) soon after (1 day) and 6 weeks after grazing on a Pallic pastoral soil in southern New Zealand. Fence‐line pacing decreased the soil volume occupied by water, macroporosity and Ksat, while increasing suspended sediment (to 0.226 g 100 mL−1), total P (to 2.0 mg L−1), mainly as particulate P (up to 90% of total P), and E. coli (to 3.52 log10 c.f.u. 100 mL−1) concentrations in overland flow at 1 day after grazing compared with soils from the rest of the paddock (0.148 g 100 mL−1, 0.86 mg L−1 and 2.86 log10 c.f.u. 100 mL−1, respectively). Although concentrations in overland flow were less at 6 weeks after grazing than at 1 day after grazing, losses of P, especially in fence‐line soils, were still above recommended limits for surface water quality. Compared to P, losses of N species would be unlikely to have a significant impact on downstream water quality. Management strategies should be directed towards minimizing the occurrence of fence‐line pacing to prevent contaminant loss and maintain water and soil quality.