DOI: 10.23637/rpg5-pgsoilpex-01
title: Dataset: Park Grass Soil Phosphorus and Exchangeable Cations 1856-2023

description: 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).
description: <b> Soil sampling. </b> Soil was sampled 12 times between 1876 and 2023 to measure soil P and exchangeable cations. All plots were sampled in 1876 with an open-ended metal box 30.5 x 30.5 cm square by 22.9 cm deep. Just three samples were taken from each plot, as this method was disruptive to grassland soil structure. Since the 1920s soils have mostly been sampled with semi-cylindrical gouge augers, typically, 15-20 cores are taken from each plot or sub-plot with a 2 cm diameter auger; cores are bulked to give one sample per plot/sub-plot. Samples are not taken within 1 m of the plot edges. In some cases, the top 23 cm layer is divided into 0 - 7.6, 7.6 - 15.2 and 15.2 - 22.9 cm layers and occasionally sub-soils (23 - 46 cm, 46 - 69 cm and 69 - 91 cm) are sampled (no sub-soil data is shown in this dataset). All data is expressed on 0 - 23cm basis; however some are weighted means from soils sampled 0 - 7.6 cm, 7.6 - 22.9 cm and some are arithmetic means of 0 - 7. 6cm, 7.6 - 15.2 cm, 15.2 - 22.9 cm samples.

Soils were air-dried, ground and sieved to &lt; 2 mm and routinely analysed for pH in water (published as a separate dataset), exchangeable cations and Olsen P. A sub-sample was more finely ground, &lt; 44 mesh, for organic C, or Total C and inorganic C, Total N (published as a separate dataset), and occasionally for Total P. 

Archived soils from 1876 and 1923 have been sub-sampled and analysed using current analytical techniques in the last 20 years. The analytical data given here is from these later analyses. 

<b> Soil Olsen P (plant-available P)</b> was measured in 1876, 1923, 1959, 1976 and then regularly from 1991 after extraction with 0.5 M NaHCO<sub>3</sub> (Olsen, 1954) using a modified method of Murphy and Riley (1962) on a continuous segmented colourimetric flow analyser (Skalar SANPLUS, Skalar Analytical BV, Breda, Netherlands). 

<b> Soil total Phosphorus (P)</b> was determined in 1959, 2002 and 2017 by fusion with sodium carbonate (Mattingly, 1970) or by aqua regia digestion (Crosland et al., 2008). 

<b>Exchangeable cations (Ca, K, Mg and Na)</b> were leached from soil with N ammonium acetate (Metson, 1956) and determined by Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) (Agilent 5900 SVDV ICP-OES Agilent Technologies 5301 Stevens Creek Blvd. Santa Clara, CA 95051, USA). 

Data for Ex Mg is shown from 1976-2023 only, as analysis of some archived soils has been problematic. Blake et al (2002) reported small increases in Ex Mg on storage over a 16-year period. For this reason, data from earlier re-analysed soils are excluded from this dataset.
description: 1. <b>A FAIR data Excel file</b> data-PG-soilPex-01.xlsx, contains Park Grass soil P and exchangeable cation data for 1856-2023. Frictionless CSV files are also provided.

2. <b>A Simple Excel file</b> simple-data-PG-soilPex-01, that provides the data in a readily readable tabular format, containing separate sheets:
- <b>Olsen P</b> Data table containing soil Olsen P data for Park Grass plots and treatments, 0-23 cm deep, 1876-2023 and estimated value for 1856.
- <b>Total P</b> Data table containing soil Total P data for Park Grass plots and treatments, 0-23 cm deep, 1959-2017. 
- <b>Ex Ca</b> Data table containing soil exchangeable calcium data for Park Grass plots and treatments, 0-23 cm deep, 1876-2023 and estimated value for 1856. 
- <b>Ex K</b> Data table containing soil exchangeable potassium data for Park Grass plots and treatments, 0-23 cm deep, 1876-2023 and estimated value for 1856. 
- <b>Ex Mg</b> Data table containing soil exchangeable magnesium data for Park Grass plots and treatments, 0-23 cm deep, 1976-2023.
- <b>Ex Na</b> Data table containing soil exchangeable sodium data for Park Grass plots and treatments, 0-23 cm deep, 1876-2023 and estimated value for 1856.
description: <b>References for analytical methods:</b> 

- <b>Blake, L., Goulding, K.W.T. 2002</b>. Effects of atmospheric deposition, soil pH and acidification on heavy metal contents in soils and vegetation of semi-natural ecosystems at Rothamsted Experimental Station, UK. Plant and Soil, 240, 235 - 251. https://doi.org/10.1023/A:1015731530498
- <b>Crosland, A.R., Zhao F.J., McGrath S.P., Lane P.W. 2008</b>. Comparison of aqua regia digestion with sodium carbonate fusion for the determination of total phosphorus in soils by inductively coupled plasma atomic emission spectroscopy (ICP). Communications in Soil Science and Plant Analysis, 1357-1368. 
- <b>Mattingly, G.E.G. 1970</b>. Total phosphorus contents of soils by perchloric acid digestion and sodium carbonate fusion. J. Ag. Sci. 74, 79-82.
- <b>Metson, A.J. 1956</b>. Methods of chemical analysis for soil survey samples. New Zealand Soil Bureau, Bulletin 12.
- <b>Murphy, J. Riley, J.P. 1962</b>. A modified single solution method for the determination of phosphate in natural waters. Analytica Chimica Acta 27, 3-36.
- <b>Olsen S.R., Cole C.V., Watanabe F.S., Dean L.A</b>. (1954) Estimation of available phosphorus in soils by extraction with sodium bicarbonate. USDA Circular 939, US Gov. Print. Office, Washington, D.C.
description: This dataset is from measurements led by Andy Gregory, Andy Macdonald, Paul Poulton, and previous scientists, and latterly analysed by the Analytical Chemistry Unit, Rothamsted Research, Harpenden, see list of contributors. The data have been collated into this FAIR dataset by Margaret Glendining and checked by Sarah Perryman. Information on methods of soil sampling and methods of analysis are taken from Poulton et al, 2026. The Analytical Chemistry Unit follows the Joint Code of Practice (JCoPR) and participates in European Quality Assurance programmes. All performance is strictly monitored using certified external standards alongside in-house standard materials. Standards and check samples are monitored and recorded. <b> New plot ids. </b>
From 2025, an additional plot identification number, "new_plot_id" uses a new naming convention assigned retrospectively to all plots since the start of the experiment in 1856. It is intended to show the provenance of the treatments of the plots using ' \ ' and '.' to indicate significant changes, where ' \ ' indicates a liming change and '.' indicates a plot-split for a fertilizer modification. For example, original plot number id., 7\1a now also has the new plot id., 7.1\L\a, where 7.1 indicates it has been split, for a new fertilizer treatment, and \L\a indicates the changes in liming it has undergone (where L a indicates a limed half pre-1964 and a indicating lime to pH 7 from 1965.