The data consist of observations of cover of plant species in permanent quadrats in a nitrogen deposition experiment on a peat bog. The experiment was located at Whim Moss in central Scotland, between 2002 and 2016. Recording of cover was by visual assessment in 40 x 40 cm quadrats. The experiment was designed to look at the change in vegetation composition with different rates of deposition of nitrogen in different forms (ammonia, ammonium, and nitrate). This work was supported by the Natural Environment Research Council award number NE/R016429/1 as part of the UK-SCAPE programme delivering National Capability. Full details about this dataset can be found at https://doi.org/10.5285/65ecd65f-e518-4cf5-85bf-7d93e66fdb96