Sward canopy effects on simulated urine events and subsequent urine patch area

Abstract

In this study, we investigated the effects of grazed pasture canopy characteristics on urine patch area. The experiment was conducted during autumn in Canterbury, New Zealand. Warm water was used to simulate urine events, ranging in volume from 1 to 8 L, onto either partially (Lenient, 6-15 cm) or fully (Hard, <6 cm) grazed perennial ryegrass and white clover (PRG) or plantain (PL) pastures. A thermal digital camera and imaging software were used to calculate the wetted area of each urine event. When a mid-range volume (4 L) was poured onto Lenient pastures, PL had a greater wetted area than PRG (0.30±0.11 m² and 0.16±0.08 m², respectively; mean±standard deviation). However, the wetted area was similar for PL and PRG under Hard grazing (0.36±0.16 m² and 0.31±0.13 m², respectively). Irrespective of pasture type and grazing intensity, the relationship between water volume and wetted area was curvilinear, with no significant increase in wetted area for simulated urine events greater than 4 L. Our results indicate that both pasture type and grazing intensity (i.e., residual pasture canopy) affect urination coverage, which could have potential implications for the nitrogen load per urine patch.