THE RELEVANCE OF SUBSOIL C AND N FOR THE ASSESSMENT OF CROPPING SYSTEM IMPACT ON SOIL ORGANIC MATTER

The aim of this study was to verify the importance of subsoil SOC and STN amounts in the evaluation of the effects of the tillage treatments on soil organic matter (SOM). The research was carried out in the Organic Arable Farming Experiment Gladbacherhof (OAFEG). It could be observed that tillage does not show any significant effects on SOC and STN in the topsoil, but influences their dynamics in the subsoil. In particular, SOC and STN decreases with all reduced tillage treatments, while FIT had no significant SOC change, and even showed a significant STN increase in the subsoil. The consideration of subsoil SOM changes therefore makes a difference in the interpretation of treatments compared to an evaluation based on topsoil-data.