Plant N uptake in the periphery of a bovine urine patch: determining the ‘effective area’

ABSTRACTThe extent to which the wetted soil area of a urine patch influences surrounding pasture is relatively unknown. The study objective was to use 15N tracer to quantify pasture N uptake in the ‘wetted’ and periphery areas of a spring deposited bovine urine patch over 311 days. Ruminant 15N enriched urine was applied to soil creating a circular wetted area, ‘zone A’ (800 kg N ha−1), with and without urea fertiliser (35 kg N ha−1). Pasture yields, 15N recovery and soil inorganic-N dynamics were monitored from zone A and two peripheral zones, B and C. Fertiliser had no effect on cumulative urinary 15N recovery in pasture (50%–52%). Average cumulative pasture 15N recovery in zones A, B and C were 30.6%, 17.3% and 4.2%, respectively. Soil inorganic-15N recovery occurred in zones A and B, declining with distance from the wetted area. The results suggest an effective urine patch area of 0.95 m2 or 3.4 times the wetted area.