The purpose of this project is the creation of a framework that will allow the prediction of drainage flux and nitrate leaching from a whole farm taking into account a full range of agricultural activities. Ultimately, the simulation framework will be used to provide nitrate and drainage flux input values for a regional groundwater model. In addition, the project aims to provide a highly effective and adaptable farm-scale simulation framework that has application well beyond the scope of nitrate leaching prediction. It is being implemented as a component-based simulation, utilising models produced by research collaborators within the Integrated Research for Aquifer Protection (IRAP) programme and from the public domain. The simulation framework consists of a variable number of individual paddock simulations controlled by a detailed farm-scale management component. When complete, FarmSim will be able to represent a wide range of agricultural activities including pasture-based grazing (sheep and dairy farming) and cropping using a wide range of cropping models applicable in New Zealand. The paddock simulation comprises vadose zone and soil components that represent unique soil and vadose conditions of each individual paddock within the farm. At any time, each paddock contains a particular crop component. The farm management module contains numerous components that enable the farm to be managed as any typical agricultural unit. These components include irrigation, soil fertility and stock management, crop rotation, cultivation and harvest. The farm management module mediates between these components to effect the overall running of the farm, which is subject to climatic inputs that are specific to the subject site. The primary challenge in creating the framework is to ensure that it is able to integrate interchangeable model components from a number of different researchers. This has been achieved utilising modern object-oriented software design techniques and tools. FarmSim runs on the Microsoft .NET Framework and makes extensive use of techniques such as the Model/View/Controller aggregate pattern, generic interfaces to components, and an object-oriented design approach incorporating inheritance, polymorphism and object-oriented design patterns. The representation of data input and outputs, as well as transfer between components, makes extensive use of Extensible Markup Language (XML). This greatly assists interfacing of FarmSim with other applications and the cross platform operation of the product. While the framework has been developed in the Microsoft Visual C#.NET language, components developed in a wide range of other languages can be incorporated. The development of a modelling and simulation framework where the modelling components are drawn from a number of different sources poses a considerable number of challenges, In particular, the componentisation of models to enable the operation of different combinations of components requires careful consideration. This requires the development of agreed interfaces and careful design of components to perform clearly defined roles within the framework. This is achieved by ensuring that the simulation entities closely emulate the functioning of objects in the natural system.
