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

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Abstract

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-Württemberg, SW Germany. This study was conducted to evaluate the effects of plow tillage (PT), reduced tillage (RT), and grassland (GL) on soil organic-C and TN stocks in surface soils. Soils samples from 13 sites of adjacent paired PT, RT, and GL were taken at depths of 0–5, 5–10, and 10–20 cm throughout Baden-Württemberg. 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 5–10 cm 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 RT 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 RT 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 0–20 cm 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 RT 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.

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