Nitrogen Dynamics in Three Contrasting Grassland Systems: Implications for Pasture Productivity and the Potential for Environmental Pollution

Nitrogen (N) dynamics were compared in 3 contrasting grassland systems (2 legume-based and I receiving fertiliser N) in a cool temperate region of New Zealand. The study was concentrated on the various N transfers that occurred during and after grazing. Critical periods for N loss by different processes have been identified, allowing a more comprehensive understanding of the role of N in the productivity of different types of pasture, and the potential for environmental pollution, Calculation of N inputs and outputs for the three pastures indicated that the two legume-based systems were more or less in balance, but in the pasture receiving fertiliser N there was an apparent gain of 182 kg N/ha/year, accounted for in the increase of soil total N.