DOI: 10.23637/rpg5-yields6523-01
title: Dataset: Park Grass Hay Yields, Fertilizer and Lime Treatments 1965-2023

description: In 1965, "Design Period 3", with a new liming regime, was introduced on Park Grass, having four sub-plots per each plot*: a) at pH 7, b) at pH 6, c) at pH 5 and d) un-limed. This dataset contains the yields of hay (t/ha), for both the 1st and 2nd cuts, harvested from Park Grass Hay Experiment from 1965 to 2023 inclusive. Details of the fertilizer, lime treatments and harvest dates are also included. Yields are provided for all fertiliser treatment plots and sub-plots (except for plots 5, and 6c & 6d, which were used for micro-plot experiments). Yields are expressed as t/ha at 100% dry matter. Variations in yield reflect the various fertilizer treatments and liming regimes, as well as the local weather and atmospheric inputs. 

*Plot 12 and 15 did not join this new liming scheme until 1976.
description: This experiment tests the effects of inorganic fertilizers, organic fertilizers and soil pH (which varies on sub-plots as a result of liming) on yields of hay. See Third Design Period 1965- for detail. The yields are estimated from strips cut from the centre of each plot with a forage harvester (since 1960). After the first cut in mid-June the remainder of each plot is mown and made into hay, continuing earlier management and ensuring return of seed. For the second cut, the whole of each plot is cut with a forage harvester.
description: An Excel file, rpg5_yields_1965-2023_01.xlsx, contains Park Grass fertilizer and lime treatments and the yields for the 1st and 2nd cuts. Frictionless CSV files are provided for users who prefer CSV over Excel files.
description: Hay yields have been recorded every year since the Park Grass experiment began, with the first harvest in 1856. Dried samples have also been kept since 1856 and these are preserved in the Rothamsted Sample Archive.
description: Individual plot yields are derived from the PGHAYEQUIV dataset in the e-RA database and were checked with the published yields in the annual Rothamsted Yield Books.

This Frictionless dataset of combined yield and treatment data was compiled by S. Perryman & R. Ostler and checked by M. Glendining September 2021. In accordance with the Joint Code of Practice for Research at Rothamsted, data processing in e-RA follow rigorous standard operating procedures to ensure the quality and correctness of data collected in the field through to depositing in the e-RA database. To ensure quality control during data inputting, the data sets were typed on two separate occasions (double data entry). During the second typing (verification) the data values were compared with those typed on the earlier occasion, and any discrepancies were resolved before verification continued. This procedure also set out how to handle situations where the written records were illegible or ambiguous. This procedure avoided visual checking of data, which can be very inaccurate. Once the data were entered into e-RA, they were independently back-checked against the original data sheets. Park Grass was initiated to investigate the ways of improving the yield of hay by the application of inorganic fertilizers and organic manure. With time, the soil became more acidic and in 1903 plots had been halved and the effects of lime tested. From 1965 a new liming regime was initiated with four sub-plots, three receiving lime to maintain soil pH (0-23cm depth) at pH 7, 6, and 5 on sub-plots a, b and c. Sub-plot d does not receive any lime.

The change in harvest method in 1960 means recorded yields of dry matter are larger than previously as fewer losses occur. The previous harvest method estimated yield by weighing the produce from the whole field. See reference by Bowley et al (2017).