Last updated 16/07/2016
This work is licensed under a Creative Commons Attribution 4.0 International License.
YOU MUST CITE AS: Rothamsted Research (2016). Park Grass soil pH. Electronic Rothamsted Archive https://doi.org/10.23637/KeyRefOAPGsoilpH.
Click the chart above for a downloadable pdf. Summary data used for this chart is available to download as an Excel Spreadsheet: pH data and treatments.
This data is for selected treatments. The complete data set is available from the e-RA curators.
The pH of the soil (at depth 0-23cm) on Park Grass was approximately 5.5 (in water) when the experiment began. 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. From 1965, the plots were further divided: two quarters of the previously limed half receive amounts of chalk calculated to maintain pH at 7 (sub plot a) and 6 (sub plot b); one part of the formerly un-limed half receives chalk, where necessary, to maintain pH 5 (sub plot c), and the other quarter (sub plot d) remains un-limed.
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.
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 (CaCO3) applied approximately every four years 1903 - 1964 then as required to maintain pH at an appropriate level.
For further information about the experiment, see Park Grass Experiment. For more information about research into Park Grass soil pH refer to Key References below.
Further details can be obtained from the e-RA Curators and the Rothamsted Guide to the Classical Experiments (2006) pp 20-31.