Impact of agricultural soil management on Earthworm biomass and SOC

Sustainable agricultural management plays a key role in maintaining soil health and associated ecosystem functions. This thesis investigates how long-term agricultural practices influence two major soil health indicators: earthworm biomass and soil organic carbon (SOC). Data from four Swiss long-term field experiments (LTEs) were harmonized using the open-source R package SoilManageR, which standardized management records into comparable indicators such as carbon inputs, soil cover duration, tillage intensity, nitrogen input, and pesticide use. Linear mixed-effects models that account for random effects between the sites were applied to evaluate the effects of management, soil texture, and climate. Earthworm biomass responded strongly to management, with prolonged soil cover and higher carbon inputs increasing abundance, while intensive tillage reduced it. In contrast, SOC levels were mainly governed by inherent soil properties, especially clay content, while management indicators contributed modestly. An alternative SOC-to-clay ratio model revealed additional, though limited, management effects, with carbon input and tillage intensity as the main management drivers of SOC over clay. These findings demonstrate that biological indicators like earthworm biomass are highly sensitive to management and provide early insights into soil health changes, whereas chemical indicators like SOC respond more slowly. The results highlight the importance of harmonized data and standardized indicators when comparing multi-site long term experiments and emphasize the potential of sustainable management strategies that maintain soil cover, reduce disturbance, and enhance organic inputs.