Assumption:
A statement assumed to be true within the OVERSEER model.
Block:
The sum of areas of the farm that are managed the same (e.g. irrigated, cropped, effluent applied) and have the same bio-physical attributes (e.g. soil type, topography).
Calibration:
The process of adjusting numerical or physical modelling parameters in the computational model for the purpose of improving agreement with experimental data.
Design criteria:
The explicit goals that have determined the model’s structure.
Evaluation:
All quantitative and qualitative methods for evaluating the degree to which a model corresponds to reality.
Engine:
Calculation model within OVERSEER. This uses inputs from an interface or file and produces the outputs.
Enterprise:
Within OVERSEER enterprise refers to the animal types present on farm, e.g. dairy, dairy replacements, sheep, beef, deer, dairy goats, and others are recognised.
Land use:
The management unit of interest. OVERSEER models pastoral, horticultural, arable and vegetable land uses and these land uses can all be integrated into one OVERSEER nutrient budget if required.
Limitation:
Something that bounds or restricts the models’ use.
Nutrient:
Seven nutrients are modelled in OVERSEER; nitrogen, phosphorus, potassium, sulphur, calcium, magnesium and sodium. Within the pastoral model, change in acidity (H+) is included for the determination of lime maintenance requirements.
Nutrient budget:
Report of net inputs and outputs to a given scale (block, farm), defined system over a fixed period of time.
Nitrogen conversion efficiency or Nitrogen Use efficiency:
product N / N input, where N inputs include fertiliser, supplements and N fixation.
Nitrogen surplus:
The difference between inputs and removals by plants.
Nutrient transfer:
Spatial and temporal movement of nutrients between locations on a farm, e.g. effluent applied to a block, or nutrients being consumed in one place and deposition as excreta in another.
OVERSEER:
the software that comprises the engine plus input data (interface) and data storage systems.
Quasi-equilibrium:
The model assumes that inputs and farm management practices described are in quasi-equilibrium ‘steady-state’ with the farm production.
Relative yield:
Predicted relative pasture yield relating to nutrients applied (fertiliser).
Sub-models:
Sub-models are a combination of science principles and assumptions that are simplified to describe nutrient use and movement. OVERSEER consists of over 20 sub-models (hydrology, climate, animal intake etc.).
Uncertainty:
The potential limitation in some part of the modelling process that is a result of incomplete knowledge.
Validation:
A comparison of model results with numerical data independently derived from experiments or observations of the environment (a part of the wider evaluation)