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

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, K _sat) 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 K _sat, 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.