Impact of tillage intensity on carbon and nitrogen pools in surface and sub‐surface soils of three long‐term field experiments |
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| Authors: | M Kaiser C Piegholdt R Andruschkewitsch D Linsler H‐J Koch B Ludwig |
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| Institution: | 1. Department of Environmental Chemistry, University of Kassel, , 37213 Witzenhausen, Germany;2. Institute of Sugar Beet Research, Department of Agronomy, , 37079 G?ttingen, Germany |
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| Abstract: | Management options such as the intensity of tillage are known to influence the turnover dynamics of soil organic matter. However, less information is available about the influence of the tillage intensity on individual soil organic matter pools with different turnover dynamics in surface as compared with sub‐surface soils. This study aimed to analyse the impact of no tillage (NT), reduced tillage (RT) and conventional tillage (CT) on labile, intermediate and stable carbon (C) and nitrogen (N) pools in surface and sub‐surface soils. We took surface and sub‐surface soil samples from the three tillage systems in three long‐term field experiments in Germany. The labile, intermediate and stable C and N pool sizes were determined by using the combined application of a decomposition experiment and a physical‐chemical separation procedure. For the surface soils, we found larger stocks of the labile C and N pool under NT and RT (C, 1.7 and 1.3 t ha?1; N, 180 and 160 kg ha?1) than with CT (C, 0.5 t ha?1; N, 60 kg ha?1). In contrast, we found significantly larger stocks of the labile C pool under CT (2.7 t ha?1) than with NT and RT (2 t ha?1) for the sub‐surface soils. The intermediate pool accounted for 75–84% of the soil organic C and total N stocks. However, the stocks of the intermediate N and C pools were only distinctly larger for NT than for CT in the surface soils. The stocks of the stable C and N pools were not affected by the tillage intensity but were positively correlated with the stocks of the clay‐size fraction and oxalate soluble aluminum, indicating a strong influence of site‐specific mineral characteristics on the size of these pools. Our results indicate soil depth‐specific variations in the response of organic matter pools to tillage of different intensity. This means that the potential benefits of decreasing tillage intensity with respect to soil functions that are closely related to organic matter dynamics have to be evaluated separately for surface and sub‐surface soils. |
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