Nitrogen and Phosphorus farm-gate balances of grassland-based dairy production systems on mixed farms in Switzerland

Farm gate balances for nitrogen (N) and phosphorus (P) were calculated for mixed crop-livestock farms in Switzerland for three types of dairy production systems: Partial grazing with indoor feeding of fresh grass with reduced (IF) and increased (IFplus) concentrate supplementation was compared with full-time grazing (FG). The aim was to identify the effects of the different systems on the N/P surplus per hectare and the N/P use efficiency (N/PUE). The mean values of the N surplus were 90.1 kg N ha-1 (FG), 91.8 kg N ha-1 (IF) and 133.6 kg N ha-1 (IFplus). The NUE was highest in IF (53.2%) and comparable for IFplus and FG (46.1 and 44.6%). Phosphorus surpluses were 2.5, 9.6 and 10.8 kg P ha-1 for FG, IF and IFplus, respectively. Some farms showed negative P balances. The PUE was 100.6, 76.5 and 70.0% for FG, IF and IFplus, respectively. Significant relationships were found between the N/P surplus and inputs of fertiliser, manure, concentrate and legume N fixation. NUE on IF and IFplus farms was significantly correlated with the percentage of arable land of the total farm land. An appropriate need-based feeding strateg y and a low-loss use of fertiliser and manure might improve the N/P balances.