DOI: 10.23637/keyrefoapgsoilph
title: Dataset: Park Grass Soil pH 1856-2011 Selected data

description: This dataset shows soil pH on the Park Grass experiment in some of the key plots, with and without chalk, from 1856-2011. 

The pH of the soil (0-23cm) on Park Grass was approximately 5.5 (in water) when the experiment began in 1856. The effects of small amounts of liming with chalk were tested in the 1880s. A regular test of liming began in 1903 with chalk applied every 4 years to the southern half of most plots. In 1965 most plots were divided into four sub-plots. Three subplots receive different amounts of lime as required to maintain pH at 7, 6 and 5 (sub-plots a, b and c, respectively). Sub-plots d receive no lime and pH of these ranges from 3.5 to 5.7, depending on the inputs from the various treatments and the atmosphere.

Except where sodium nitrate (orange line N*) has been applied or where liming with chalk has maintained the pH (dashed lines), soil has acidified slowly through the impact of acid deposition from the atmosphere and rapidly where ammonium fertiliser (blue line N) has been applied. Soil pH (0-23cm) is c 3.5 on the plots given most ammonium sulphate and 5.0-5.3 on the un-limed, unfertilized plots. Sub plot c of most plots is nearest to the original soil pH. Soil pH has slowly recovered by about 0.5 pH units on plot 9/1d (data not shown), more than 25 years after ammonium sulphate was last applied.
description: pH was first measured by Crowther in 1923 using the hydrogen electrode method and a 1:5 soil:water suspension. The next measurements were made on samples from 1959, using a glass electrode and a 1:2.5 soil:water suspension (Warren and Johnston, 1964). The different soil:water ratios had little effect on measured pH (see Warren and Johnston 1963, p 244-245). pH was determined from 1976 onwards by glass electrode in deionised water with a 1:2.5 soil:water suspension, together with archived ground soils from 1876, which were analysed in 1984. pH is measured in air-dried soil, sieved &lt;2mm.
description: Summary data of the soil pH in water, in relation to six treatments on Park Grass: No fertiliser control; nitrogen fertiliser as sodium nitrate; nitrogen as ammonium sulphate (each with and without chalk).
description: Fertiliser treatments since 1856;
No fertiliser - Plot 3: No fertilizer or manure
N/*2PKNaMg - Plot 14: 96kgN as sodium nitrate plus P, K, Na and Mg
N2PKNaMg - Plot 9: 96kgN as ammonium sulphate plus P, K, Na and Mg

Chalk: Ground chalk (CaCO<sub>3</sub>) applied approximately every four years 1903 - 1964 then as required to maintain pH at 7, 6 or 5 for sub-plots a, b and c respectively. 

Soil details:
FAO Classification: Chromic Luvisol (or Alisol); Silty clay loam over clay-with-flints overlying chalk.
description: Older historical information is taken from original raw data sheets and analysis files, held in the archives at Rothamsted Research, and the Annual Rothamsted Yield Books. Data since 1991 is souced from current Rothamsted Analytical Chemistry Unit. All raw data is stored in the e-RA database DET. The data in e-RA are subject to rigorous quality control procedures from the point of collection in the field to entry into the database. All measurements are strictly monitored using certified standards alongside.

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.

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. Johnston et al (1986) predict a pH of 5.6 - 5.8 in 1856. As the site had been grassland many years previously it had not received chalk applications. Some areas have a acidic surface 'mat' due to biological activity being hindered.