Whole Farm Modelling Gross Margin ($/ha) Relative Wind Erosion RiskDifference in SOC Change (t/ha/y) Proportion of Land under Perennial Forage [AD Moore (in press), Animal Production Science]

Why build simulations of farms rather than paddocks? More complicated to obtain insight More time-consuming to get right So why bother? Lateral flows of material or energy Dynamic management of limited resources: land, forage, water, manure, time, money Use of plants or animals across enterprises Livestock!

Features in APSIM v.7 relevant to modelling at the farm scale Multiple paddocks (Val) Land use sequencing The richer syntax for describing management with Manager2 Stock component (Neville)

Land use sequences with APSFarm “State and transition” approach – The current land use in a paddock is a “state” – Transitions between land uses are driven by events and conditions

Handling Collections of Entities

Iterating through Collections of Modules in Manager2 Iteration Indirection

Output Handling The number of potential outputs from a model increases with both: – the number of enterprises, and – the number of paddocks Analyses of whole-farm systems typically have greater dimensionality Need to plan the spatial, as well as the temporal, scale at which outputs are to be stored Aggregation of variables in the model is required: – area-weighted averages for land-based fluxes – number-weighted averages for (e.g.) livestock weights Using Manager2 to iterate → point → select works well when aggregating

Options for Diagnosis, Visualization & Interpretation Supply or allocation of a resource through time Production summaries – Aggregated to farm scale Financial calculations – Within & across enterprises Efficient frontiers – Tradeoffs when the options space being analysed is large Flow analyses – Water-use efficiency framework – Nitrogen budgets