The Moorepark grass growth model: application in grazing systems

The Moorepark Grass Growth model (MGGm) is a dynamic model developed in C++ describing the grass biomass evolution of a paddock over time with a daily time step. It is assumed that each urine and faeces deposition affects 2 m2 area of the paddock, with the model describing the different variables and events such as grass growth, mineralisation, immobilisation, leaching and nitrogen (N) uptake by the plant at the 2 m2 level. Different N mineral fertilisations in a grazing context have been simulated, and the impact on grass growth and N content of the grass has been evaluated. The grazing simulations examined, described the effect of N returns on grass growth and N fluxes accurately. The model has been able to react to different weather conditions, and to different levels of N mineral fertilisation. The response of the grass growth, the biomass produced and the grass N content to the N mineral fertilisation level is in line with the literature. In average, the mineral N fertilisation leaded to an increase of grass utilised of 12 and 17 kg of dry matter per kg of N fertilised for the French and Irish simulation respectively