The Pasture Growth Forecaster (PGF) is a statistical mathematical model that calculates pasture growth from the environmental conditions experienced at a site. These environmental conditions include soil temperature, solar radiation, potential evapotranspiration, rainfall, soil water holding capacity and fertility. These climate data are provided by NIWA’s Virtual Climate Network Stations (VCNS).
Virtual Climate Station (VCS) data provide estimates of climate for the whole of New Zealand at a 5km grid scale. These data are run through the Pasture Growth Forecaster to calculate the historical pasture growth rates experienced within each grid.
The model, when provided with measurements of actual cover uses these in a learning algorithm to improve accuracy. This improvement is achieved by adjusting the models mathematical parameters such factors as soil fertility and soil water holding capacity. SPACE provides pasture cover data of good accuracy within the low to medium cover range and this feedback to the model continually improves accuracy over time as the model learns about the paddock.
The LIC SPACE system uses a combination of satellite data and PGF data to produce pasture reports for days where satellite data is not available, and to estimate readings for paddocks with high dry matter that would otherwise be impacted by spectral saturation.
The example is a six day gap between last satellite report and an estimated cover report.
Good pasture management is the key to farm profitability. DairyNZ and B+LNZ are confident that pasture growth forecasts will help farmers make better decisions on supplementary feeding, grazing rotations, silage making and nitrogen management. Funded by DairyNZ, B+LNZ and the Ministry for Primary Industries through the Primary Growth Partnership.