Dataset: Park Grass Soil pH 1856-2011 Selected data

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.