Wetlands in Mediterranean climates undergo large fluctuations in water levels that lead to wet-dry cycles in lake beds, with important effects on sediments and water biogeochemistry. Thus, wetland drainage and ploughing have different effects on soil properties that depend on previous waterlogging periods. However, current knowledge of this topic remains scarce. Fifty-six years after drainage of the Antela lake (Galicia, NW Spain) and characterisation of the main soil properties, in 2019 a stratified sampling - using elevation as proxy for waterlogging length - was done. We checked three hypotheses: a) that changes in the soil pH and organic C were higher in the lake core (permanently waterlogged) than in sediment samples representing four different periods of waterlogging; b) that 13C and 15N signatures are useful for tracing differences in the soil C and N dynamics related to the prior duration of waterlogging; and c) that land subsidence in the area previously occupied by peat was higher than predicted immediately after drainage. As hypothesized, we found that drainage and ploughing triggered acidification and C mineralization processes, which were more intense in the previously most waterlogged soils (-0.8 pHH2O units; −0.5 pHKCl units; 20–70% of C lost). In the 2019 samples: a) the highest soil N content (values up to 4-fold higher) and lowest C/N ratio (up to 4 units lower) were recorded in the area that was previously permanently waterlogged; b) soil δ15N increased significantly (around 3‰) with elevation (i.e. shorter waterlogging period), while soil δ13C did not vary; and c) peat subsidence ranged from 17 to 32 cm (3.0–5.7 mm y−1). The main consequence of draining the Antela lake and cultivating the reclaimed land was the opening of water and nutrient cycles, drainage effects being greater than the cultivation ones, and land subsidence 6–8 times higher than initially predicted.