Sugarcane, banana and grain (cropping) industries
The sugarcane, banana and grain industries are modelled using paddock soil water balance models. These are designed specifically to simulate the effects of management practices such as crop rotations, intensity of tillage or traffic, and the application method, rate and timing of herbicides and fertilisers.
The Agricultural Production Systems sIMulator (APSIM) model is used for the sugarcane industry and the HowLeaky model is used for the banana and grain industry simulations.
The paddock soil water balance model simulations used in P2R Projector are summaries of those generated by the Paddock to Reef – Paddock Modelling Team to support the Reef Water Quality Report Card reporting process. Read more about the Paddock to Reef Integrated Monitoring, Modelling and Reporting Program.
A 20 year daily timestep modelling simulation is conducted for each soil type in each climate zone, for each scenario of management practice. For the sugarcane industry this equates to around 6 million daily modelling simulations.
To prepare the data for use in the P2R Projector, the modelling simulation results are temporally averaged to provide a single long term annual average yield (kg/ha/yr). These yield values are further summarised to provide a single yield for each represented soil type, prevailing climate (wet, medium, dry) and management practice at the sub-catchment scale.
Known limitations for paddock water balance models
- P2R Projector does not directly model management practice on an individual farm.
- The catchment level averaging of soil type/climate/management practice combination means that local subtleties of the position of a farm within the landscape and the effect of slope are not represented in the predictions for each project.
- P2R Projector results represent the ‘average’ water quality improvement for a management practice change and soil type combination within the project catchment. Some projects will be better and some will be worse than the P2R Predictions.