Dataset: Park Grass Soil Phosphorus and Exchangeable Cations 1856-2023

This dataset consists of the soil Olsen Phosphorus (plant-available P), total P, and the exchangeable cations Calcium (Ex Ca), Magnesium (Ex Mg), Potassium (Ex K) and Sodium (Ex Na), of individual plots of the Park Grass experiment, 1876-2023, and estimated values for when the experiment began in 1856. Olsen P and exchangeable cations were measured 12 times between 1876 and 2023; total soil P was measured three times. Data is given for the 0-23 cm soil depth. Not all plots were sampled on each occasion. Also included are details of the fertilizer and lime treatments applied.

<b>Estimated starting values</b> for when the experiment began in 1856, before the fertilizer and lime treatments were started were 6 mg/kg Olsen P; 60 mg/kg Ex K; 2640 mg/kg Ex Ca; 80 mg/kg Ex Mg and 43 mg/kg Ex Na. These were generally extrapolated back from measured values in the Nil treatment in 1876.

<b>Mats of undecomposed plant material</b>: On many of the very acidic sub-plots, given ammonium salts but no lime, a 2 - 4 cm mat of undecomposed organic plant-material has accumulated. In 1959 and subsequently this was usually sampled separately before sampling the mineral soil down to 23 cm. This is indicated in the dataset.

These soil data are discussed in details by Poulton et al. (2026).