With 1.34 million hectares, grassland represents the most important land use system in Austria in terms of area. Among important ecological functions, grassland provides the feed basis for approximately 53,000 livestock farms.
Various utilisation intensities caused by different site conditions, small-scaled structure and multiple harvests per growing season are impeding a systematic estimation of yield and quality. Such estimates have so far only been possible by using random samples in statistical models.
The annual and regional yield variations, which are primarily dependent on weather conditions, cannot be pictured sufficiently in such a way. This particularly applies to the quantification of yield reductions and losses due to extreme events such as droughts or hail, which will occur more frequently in the future as a result of climate change.
Yield and quality must be evaluated together in the assessment of grasslands. Harvesting at an early stage of development provides low dry matter yield but high forage quality. With further development of vegetation, biomass increases, but its quality drops sharply. Farmers can directly control the relationship between yield and forage quality by selecting the most appropriate cutting time. An objective assessment of the co-evolution of these two parameters is therefore decisive for the economic success and productivity of a grassland farm.
With the help of earth observation (EO) services such as Copernicus, grasslands and utilisation frequency can be monitored continuously at field level. To derive vegetation dynamics, SatGrass combines remote sensing and weather data into a grassland growth model, which is calibrated and validated with numerous, destructive and spatially distributed yield and quality measurements. The most important goals of Sat-Grass are:
- The identification of harvest dates from Sentinel-1 (S1) and Sentinel-2 (S2) time-series to enable a growth-specific yield determination.
- The estimation of yield and forage quality, as well as their seasonal dynamics, based on remotely estimated harvest dates, satellite-based biophysical vegetation traits, weather conditions and water availability/balance.
At field level, the possibility to determine the ideal cutting time permits the farmer to optimise yield and quality for individual parcels. At the regional level, the results valuably contribute to Austria's Economic Accounts for Agriculture (EAA).
SatGrass moreover contributes to climate change adaptation and mitigation in Austria. Indeed, climate change in grassland areas represents one of the biggest challenges for the maintenance of grassland and livestock farming.
A precise quantification of yield reductions in drought-affected regions - or surpluses in favoured areas - is the basic of fodder balances. The knowledge of such yield distributions constitutes the prerequisite for the planning of climate adaptation concepts and the implementation of measures for an area-wide fodder supply for livestock.
Österreichische Arbeitsgemeinschaft für Grünland und Viehwirtschaft (ÖAG)
- Central Institute for Meteorology and Geodynamics (ZAMG)
- Höhere Bundeslehr- und Foschungsanstalt für Landwirtschaft Raumberg-Gumpenstein
- Vienna University of Technology
- University of Natural Resources and Applied Life Sciences Vienna