This dataset contains information on bio-available phosphorus and microbial biomass phosphorus from two UK grassland soils and how this is affected by elevated CO2 (eCO2). The soils are from naturally phosphorus limited grasslands in the Peak District National Park, in northern England. The grasslands were exposed to eCO2 of 600 ppm, and ambient CO2 controls were maintained at ca. 400 ppm for three growing seasons (2018-2020). Soils were sampled once each year in October, and underwent extraction (bio-available phosphorus) or chloroform-fumigation-extraction (microbial biomass phosphorus) with 0.5M NaHCO3. Concentrations of phosphorus in the extracts were determined by ICP-OES.