Phosphorus mass cycling and balance in dairy farms: Case studies in Puerto Rico

•Assessment of whole farm phosphorus (P) balance and internal mass P cycling.•Dietary P concentrations exceeded more than 60% nutritional recommendations of P.•Annual P surplus in the two dairy farms between 54 and 59kgPha−1.•Excess P in the animal diet is associated with high P concentration in the feeds.•Management practices should be implemented to reduce the high on-farm P surplus.