Park Grass

Park Grass Botanical Compostion

Studies have also been made of the botanical composition of the plots both through visual surveys and by looking at the percentage contribution to the hay made by the various species. The most recent comprehensive surveys of botanical composition, PARKCOMPIC, made just before the first cut, were done annually between 1991 and 2000. See 150th Anniversary Publication for soil pH and a summary of those species comprising at least 10% of herbage, and the total number of species identified on each plot (after Crawley et al, 2005). There are many interactions between fertilizer, manure treatment and pH. Without exception, all the original treatments imposed in 1856 have caused a decline in species number compared to the original sward. In most cases, this is due to changes in soil fertility and annual nutrient inputs and perhaps also the way in which the sward was managed. Numbers of species have decreased, even on the plots given no fertilizers or manures, due to acid deposition. Applying nitrogen as sodium nitrate or ammonion sulphate reduces diversity further, and in the ammonium form also rapidly acidifies the soil, reducing the number of species to one or two, Holcus lanatus (Yorkshire Fog) and Anthoxanthum odoratum (Sweet Vernal Grass).

Survey method: From 1991 to 2000, six randomly located quadrats measuring 50cm x 25cm were located within each of the plots in early June, immediately before the first cut. The herbage was cut with scissors to ground level and plant material taken back to the laboratory where it was sorted into species. Samples were oven-dried at 80 °C for 24 hours, after which dry mass was determined for each species. Data in PARKCOMPIC is shown as gm/0.125 m² for each quadrat and as gm/0.75m² for the total (ie 6 quadrats).

Further information is given in the Rothamsted Guide to the Classical Experiments 2018 pages 20-30, in Crawley et. al. (2005) and in the Key References listed below.

The dataset PKMASSEFF is a survey of plant diversity carried out by Kunin (1998) in 1993 and 1994. He measured plant diversity in 54 transects across the plot boundaries of all plots, except 5, 9-1, 14-1, 18-20, mainly sub-plots 'a' (pH = 7) and 'd' (unlimed). Transects were surveyed in May and June 1993 and May 1994, before the first cut of each year. In each surveyed transect the number of reproductive plants of each species was recorded. See Kunin (1998) in Key References below for full details of survey method and description of transects.

Earlier surveys of the botanical composition of Park Grass were carried out from 1862 to 1976. The dataset PARKCOMP consists of complete botanical analyses, carried out in 1862, 1867, 1872 and 1877, and several more times between 1903 and 1948. No analyses were carried out between 1949 and 1972. Further full botanical analyses were carried out on limited plots between 1973 and 1976. Full details are given by Williams 1978. Samples of plant material were taken from each plot, separated into the different species and weighed. The Open University two letter species codes are also included.

The dataset PARKPARTCOMP contains a much simpler partial analysis of the three main groups of plants - grasses, legumes and other species. These were carried out between 1862 and 1976. Again samples were taken from each plot, separated and then weighed to determine the percentage composition.

Except during 1895-1902, either complete or partial analyses were done in all years between 1874 and 1948 for plots 3 (unmanured), 7 (PKNaMg) and 9 (N2PKNaMg). Full details are given by Williams 1978.

Williams (1978) analysed selected plots between 1973 and 1976, after the sub-division of the Limed (L) and Unlimed (U) plots into a, b, c and d sub-plots. Results for 1975 and 1976 in PARKPARTCOMP still refer to L and U half-plots. The L half-plot is equivalent to the a and b sub-plots, the U half-plot is equivalent to the c and d subplots.

Between 1920 and 1990 visual surveys were made twice a year, before the hay was cut in June and again in the autumn (PARKVISUAL).

Grass sorting 1930s

Plots 11-2d and 12d, June 2005

Plots 14.1 and 14.2, May 1990

Key References

Harvesting methods

The plots were originally cut by scythe, then by horse-drawn and then tractor-drawn mowers. The mowing maching 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 Unlimed 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. However, for the first cut the remainder of each plot is still 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. Consequently recorded yields of dry matter are now larger than previously as fewer losses occur. The following correction factor should be used for post-1960 data for cut 1 to give yield values equivalent to pre-1960 values:

Y_{cut 1} = 0.2743 x (Y_F ^1.662 ) (Bowley et al, 2017)

where Y_F = yield collected by forage harvester, t/ha. The correction factor was obtained from the relationship between yields for hay and forage harvested cuts (r² = 0.90) for a selection of plots for 1959 and 1992-1994. For more details, refer to Bowley et al, 2017 (see Key References below).

Since 2021, a new machine has been in use, the 'Amazone Forage Harvester'. It cuts a width of 1.5m rather than the previous 1.1m. The machine is fitted with a bespoke weighing balance which weighs the cut as it goes. Subsequent analyses take this into account and a conversion is already calculated.

Harvesting 1941

Harvesting 1st cut 2005

Harvesting 1st cut 2005

Cutting 2nd cut 2015

Raking 2nd cut 2015

Weighing 2nd cut 2015

Weighing sub-samples for % moisture 2nd cut 2015

Dried samples 2nd cut 2015

Labelled sample tins 2nd cut 2015

Amazone Forage Harvester June 2022 at south side of Park Grass

Park Grass 2022 mowing east end

Mowing Park Grass June 2022

Key References

Links

Park Grass Soils

The Park Grass experiment was started by Lawes and Gilbert in 1856 to look at the effects of applying fertilizers and manures on the yield of hay from permanent grassland. The field had been in permanent pasture for at least 100 years before the experiment began. It is never ploughed or sown. Here, details are given of the site and soil.

Site details

• Location: Rothamsted Research, Harpenden, Herts, AL5 2JQ, UK
• Latitude: 51.804
• Longitude: -0.373
• GB Grid Reference: TL122 129
• Gradient: The site is level
• Irrigation: There is no irrigation

Soil details

• FAO Classification: Chromic Luvisol (or Alisol)
• U.S. Soil Taxonomy: Aquic (or Typic) Paleudalf
• Soil Survey of England & Wales Group: Gleyic argillic brown earths (Hook) and Stagnogleyic paleo-argillic brown earth (batcombe) (Avery, 1980)
• Soil Survey of England & Wales Series: Predominately Hook Series, some also typical Batcombe (Avery & Catt, 1995 - see Soil Map link on the left hand side).

For more details of the Hook and Batcombe soil series, see Cranfield University 2018 Soils Guide.

Soil texture class: Silty clay loam over clay-with-flints overlying chalk. The site is normally well drained (Hook series) or moderately well drained (Batcombe series) (Avery & Catt, 1995).

Soil texture, 0-23cm, 2002 from six sub-plots (Poulton, pers comm):

• Sand (2000 - 63 µm) : 11.6 %
• Silt (63 - 2 µm) : 66.3 %
• Clay (<2 µm) : 22.1 %

Soil structure: The structure of the topsoils are clearly influenced by organic matter content and base status. The calcareous plots have very dark coloured surface horizons, characterized by strongly developed granular or fine subangluar blocky peds. In contrast, the acid plots are more weakly structured and in extreme cases, typified by the unlimed plots which have received regular applications of ammonium sulphate (eg plots 4/2d, 9/2d and 11/2d), organic matter has accumulated at the surface to form a discrete mat or mor layer, and the immediately underlying mineral soil is massive and structureless (Avery & Catt, 1995).

Soil pH: 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-plot d receives no lime and pH of these ranges from 3.5 to 5.7, depending on the fertilizer treatment. See Park Grass Open Access soil pH for selected plots, for more details.

Soil sampling: A few plots were sampled in 1870 but the first major soil sampling was in 1876, 20 years after the experiment started. Soils were taken with an open-ended iron box, 30.5cm x 30.5cm x 22.9cm deep. Just three samples were taken from each plot, as this method was disruptive on grassland. Since 1932, samples have been taken by straight-sided semi-cylindrical auger, bulking a large number of cores for each plot or sub-plot. All samples except in 1932 have been taken to a depth of 23cm, and in some years, deeper samples were also taken (Poulton, 1996).

Soil bulk density: A standard value of 1.1 g cm³ (2500 t ha^-1) should be used as a general indication of soil bulk density. This is the mean of all plots, sampled in 2011, 0-23cm only. Note that if detailed plot calculations are required, eg nutrient content, individual plot data should be used - please contact the e-RA Curators for this. Also, in some plots bulk density varies greatly within the 23cm depth particularly on acidic sub-plots with a 'mat' of semi decomposed organic matter on the surface.

With thanks to Andy Macdonald and Paul Poulton for help with compiling the information and text.

Key References