Balancing Production and Environmental Goals in Pasture‐Based Dairy Systems: A Longitudinal Case Study of Transition in a High Performing New Zealand Farm

Production and environmental outputs of intensive pasture‐based dairy systems must be rebalanced to reduce overall environmental footprint. This analysis documents the tactical management changes that enabled Lincoln University Dairy Farm (LUDF) to transition from high nitrogen (N) inputs (345 kg N fertiliser/ha/year) to a lower N input strategy (167 kg N/ha/year) to reduce nitrate leaching. The reduction in N fertiliser was the outcome of 2.4 fewer spreading events/year and 8 kg/ha less N per event. The resultant reduction in herbage accumulation (HA) in the lower input years (1.53 t DM/ha/year) was 0.77 t less than expected based on apparent N response efficiency due to buffering provided by longer regrowth intervals (mean 4 days) and more‐advanced leaf stage at grazing (+0.3). Nonetheless, only 15% of grazing events occurred at or above the optimum plant leaf stage. Post‐grazing herbage mass and pasture utilisation efficiency did not differ between phases. Pasture metabolisable energy content was similar between phases. Lower crude protein and higher water‐soluble carbohydrate:N ratios in the lower input years reduced total N intake, urinary N load and N leaching risk. Thus, while HA and milk production both decreased by 8% in the lower input years, estimated N leaching decreased by 38%.