DOI: 10.23637/rpg5-pgyields1856-1902-1
title: Dataset: Park Grass Fertilizer Treatments and Hay Yields 1856-1902

description: This dataset contains the fertilizer treatments and yields of hay (t/ha), for both the 1st and 2nd cuts, harvested from Park Grass Hay Experiment since its inception in 1856 to 1902, "Design Period 1" (In 1903, "Design Period 2" started on Park Grass when but in 1903, when most plots were split into two to test the effects of liming, as acidity had built up in the soil with fertilizer use during Period 1). The experiment was originally one plot per treatment since 1856 and yields are provided for all fertiliser treatment plots. Yields are expressed as t/ha at 100% dry matter. Variations in yield reflect the various fertilizer treatments and liming regimes (as well as variables such as the weather and atmospheric inputs). This data set is followed by that for Design Period 2, 1903-1964, and so includes plot numbers ("subsequent plots"), and dates of introduction, from that later design-period to provide continuity between datasets. 

Park Grass was initiated to investigate the ways of improving the yield of hay by the application of inorganic fertilizers and organic manure. The fertilizer tests were made of farmyard manure, N, P, K, Mg, Na, Si, as well as sawdust and straw, in various combinations and amounts (fishmeal and poultry manure were not tested until the early 20th century). 

As the experiment progressed, it was observed that the soil became more acidic and in 1903 plots were halved and the effects of lime tested - therefore this dataset ends in 1902. The next dataset is Design Period 2, 1903-1964 (see Related Datasets below). However, note that in 1881 Lawes and gilbert started investigating the effects of lime applications to small parts of the northern edge of some of the plots. In 1883 the west halves of plots received burnt lime, then in 1887 the eastern halves received burnt lime. These early tests of lime on yields are not included in this dataset but are available from the e-RA database. Notes made by Lawes & Gilbert and staff at that time are available in the "Rothamsted White Books". Therefore, note that all parts of every plot, even the un-limed sublots of Design Period 2 and the sub-plot d's of Design Period 3, received lime once in their history, although this was a small amount over &gt;138 years ago.
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. The plots were originally cut by scythe, then by horse-drawn and then tractor-drawn mowers. The mowing machine was first used for the first cut in 1901, though it had been used for the second cut since 1881. The plots were cut each year for hay, usually in June, and a second cut taken in the autumn since 1875. A second cut was not taken every year, and not from every plot each year, if there was insufficient herbage to sample. No second cut taken 1856-1874, 1876, 1884, 1885, 1887, 1899, 1911, 1914, 1921, 1924, 1933 or 2003. In 1903-1917, the second cut was taken from the whole plot, not the Limed and Un-limed halves. The regrowth after the first cut was grazed by sheep 1856-1872, except for 1866, 1870, and 1873 and 1874, when the regrowth was mown but not removed from the plots.

Yields were originally estimated by weighing the produce from the whole plot, either as hay (1st harvest) or green crop (2nd harvest), and dry matter determined. Since 1960, yields of dry matter have been estimated from strips cut with a forage harvester.
description: An Excel file, 1856-1902-rpg5_yields_01.xlsx, contains Park Grass fertilizer and the yields for the 1st and 2nd cuts. This file has selected key columns in the crop_data coloured, and likewise in the fields_metadata, to enable ease of use. Frictionless CSV files are provided for users who prefer CSV over Excel files.
description: <b>Conversion Factor - Change in harvesting method in 1960:</b>
When comparing these plot yields to later yields after 1960 a conversion factor is recommended due to a change in harvesting method in 1960 which has resulted in recorded yields of dry matter being larger than previous harvest method, as fewer losses occur. The previous harvest method to 1959 was estimated yield by weighing the produce from the whole field. Since 1960, the yield of a strip cut by the forage harvester at 100% dry matter (two per plot), weighed immediately in the field, is used for yield value for 1960-64 and post-1965, see next datasets. A conversion equation for 1960-1964, to match pre-1960 yields, is Yield cut 1 = 0.2743 x (YF^1.663) (See references, Bowley et al (2017). 

In 2025 a new convention for plot ID format (new_plot_id) was introduced to enable compatibility of plot names throughout the duration of the Park Grass Experiment datasets. This has been applied retrospectively to plots and more easily communicates plot changes over time and continuity between plots in the published data. It also aims to address the Excel date problem whereby a number of plot names that can be auto-converted to dates by Excel. The new conventions for plots split for fertilizer modifications uses '.' as the division separator. The new conventions for plots divided for new liming treatments uses '\' as the division separator. The traditional format is also kept in the dataset (plot_id).
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. Park Grass data 1856- was entered to the e-RA database by Jackie Potts, this involved the conversion of original records which were in lbs per acre to tonnes per hectare. 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. I thank and acknowledge the many people involved with the ultimate creation of this digital dataset that is available to scientists worldwide; the creators of the experiment, Lawes & Gilbert, the farm staff and technicians who ran the experiment and recorded the results so meticulously in beautiful copperplate handwritten paper records (see media tab for some examples), and the data entry clerks and first e-RA curator Jackie Potts who initially entered the data into the first e-RA database from which this dataset has been derived.