Soil nutrient accumulation in alpaca latrine sites

Alpacas establish long-lasting communal latrine sites or dunghills. To quantify the extent of nutrient transfer and accumulation associated with alpaca latrine sites and to provide a three-dimensional assessment of a pasture paddock with 11-year-old latrine sites, three comparisons were made: (a) centres of latrines were compared with non-latrine control sites 20m away; (b) surface soils (0–10 cm) were compared with subsurface soils (10–30 cm); and (c) across cardinal compass directions and regular distances from latrine centres were compared. Accumulation of nutrients was clearly detected, with a significant surface build-up, relative to controls, observed in phosphorus (3 times), nitrate-nitrogen (3.8 times), potassium (3.2 times), sulfur (1.9 times), organic carbon (1.3 times) and electrical conductivity (2.4 times). Soil pH was also significantly decreased in the centre of the latrine sites (pHw 0.6–0.7 units). Across the main axes of the latrines there was a clear trend of decreasing electrical conductivity, organic carbon and nutrients (NO3, P, K, Ca, Mg, Na, and S) away from a peak concentration at or near the centre. Soil pH demonstrated the inverse with a decrease towards the centre. Under set stocking conditions large transfers in nutrients towards latrines could have long-term effects on pasture growth and composition. Some management options are discussed.