Indicators for the Evaluation of Soil Organic Matter and their Application in Organic and Conventional Farming Systems

Summary

In view of the problems caused by soil degradation, it becomes ever more important to estimate the influence of different management systems on soil organic matter (SOM). In the past, a number of indicators characterizing SOM have been elaborated, which, however, do not allow to draw conclusions on separate management measures or even future development tendencies. A promising approach might be humus balancing, which quantifies and evaluates the humus supply of soils on the basis of crop rotation and fertilization. Comparative studies on adjacent arable sites under both organic and conventional management in different climatic regions of Germany have revealed that the indicator soil organic carbon (SOC) depends mainly on the site conditions, whereas indicators characterizing active SOM like hot water soluble C (Chws), C in microbial biomass (Cmic) and the enzyme activities of β-glucosidase and catalase are stronger related to management methods. It became evident that humus balancing is a good indicator of the active SOM pool and thus also a qualified tool for demonstrating management effects.