Modelling the growth and utilisation of kikuyu grass (Pennisetum clandestinum) under grazing. 1. Model definition and parameterisation

This paper describes a Tropical Pasture Simulator. This is a simple mechani stic model representing the growth of vegetative tropical pastures under ro tational or continuous grazing with responses to N fertiliser, temperature and irradiance that can be used as a tool to study management options for t he development of sustainable grazing systems. The model was derived as an adaptation of the 'Hurley pasture models' which were originally designed to simulate the growth of ryegrass. The model incorporates the processes of l ight interception and photosynthesis, leaf area expansion; growth, ageing a nd senescence of plant tissues, recycling of substrates from senescing tiss ues, nitrogen uptake, mineralisation of soil organic N, N leaching and graz ing. The paper discusses the main structure of the model, its components an d the main adaptations required to simulate the growth of tropical pastures . The model was parameterised for kikuyu grass (Pennisetum clandestinum) gr owing in dairy systems in highland regions of Costa Rica. This paper also d iscusses the sensitivity of parameter values and the development of minimum parameter datasets for time and cost-effective implementation of the model . (C) 2000 Elsevier Science Ltd. All rights reserved.