Soil organic-carbon and total nitrogen stocks as affected by different land uses in Baden-Wurttemberg (southwest Germany)

Regional direct field measurements of potential response of soil organic-carbon (SOC) and total nitrogen (TN) stocks to different land uses is of great importance for the development of best-management practices with respect to SOC and TN accumulation in soils of Baden-Wurttemberg, SW Germany This study was conducted to evaluate the effects of plow tillage (PT), reduced tillage (FIT), and grassland (GL) on soil organic-C and TN stocks in surface soils. Soils samples from 13 sites of adjacent paired PT, FIT, and GL were taken at depths of 0-5, 5-10, and 10-20cm throughout Baden-Wurttemberg. Averaged over the 13 sites, GL had significantly higher SOC concentrations in the 0-5 cm layer and significantly higher TN concentrations in the 0-5 and 5-10cm layers, compared with soils under PT Soils under RT tended to have higher SOC concentrations in the 0-5 and 5-10 cm layers and higher TN concentrations at all the three depths, compared with soils under PT Grassland contained significantly higher SOC and TN stocks than soils under PT in the 0-5 and 5-10 cm layers. Soils under FIT tended to have higher SOC and TN stocks than soils under PT in all the three layers. Grassland contained 44.5% (14.75 Mg C ha(-1)) more SOC and 43.5% (1.58 Mg N ha(-1)) more TN stocks than soils under PT, and soils under FIT contained 7.3% (2.7 Mg C ha(-1)) more SOC and 7.9% (0.29 Mg N ha(-1)) more TN stocks than soils under PT in the 0-20cm depth interval, respectively. We estimated that GL accumulated an average 1.27 Mg C ha-1 y(-1) and 0.129 Mg N ha(-1) y(-1) more than soils under PT over an average period of 11 y, whereas soils under FIT accumulated 0.32 Mg C ha(-1) y(-1) and 0.033 Mg N ha(-1) y(-1) relative to soils under PT in the top 20 cm, respectively. The outcomes of this study are significant for the assessment of C and N sequestration forecasting of land-use management associated with grassland and reduced tillage in SW Germany.