Quantification of organic carbon pools for Austria's agricultural soils using a soil information system

Within the framework of the project "Austrian Carbon Balance Model", we estimated soil organic carbon (OC) content for the agricultural land of Austria. The basic chemical and physical data were obtained from the national electronic soil information system BORIS (Boden Rechnergestutztes Informtions System). The latter data were obtained through soil surveys performed over the past 10 yr. The BORIS data were corrected for soil gravel content, bulk densities and differences in chemical analytical methods used for soil OC. Our estimation also showed the following ranking for soil OC content (0-50 cm) under different land use systems: vineyards (57.6 t C ha(-1)) similar to cropland (59.5 t C ha(-1)) < orchards/gardenland (78 t C ha(-1)) similar to intensive grassland (81 t C ha(-1)) < extensive grassland (119 t C ha(-1)). Although the main portion of soil carbon is stored in topsoils (0-20 cm) in all land-use classes, deeper soil layers (20-50 cm) contribute significantly to the overall inventory (between 18.2 and 27.2 t C ha(-1)), but appear to be less influenced by land use. A total OC storage in Austria's agricultural soils of 284 Mt was estimated. A west-east gradient of OC storage in agricultural soils of different Federal Provinces was observed. Under Austrian conditions, extensively used grassland plays an important role for OC-storage. Wide C:N ratios in these soils suggest accumulation of poorly humified organic material and slow OC turnover.