DOI: 10.23637/rrn1-hlasoc4814-01
title: Dataset: Highfield Ley-arable experiment soil chemical properties 1948-2014

description: This dataset gives the % soil organic carbon (SOC), % total nitrogen (N) and other assorted soil measurements in the topsoil (0-23cm) of selected plots of Blocks 1-4 of the Highfield Ley-arable Experiment, 1948-2014. Not all plots are sampled on every occasion, particularly in the early years of the experiment. Baseline SOC measurements were taken in December 1948 at the start of the experiment, then the soil was sampled at irregular intervals of several years until 2014. Soil N was measured from 1987 onwards. Total C, Inorganic C, Soil pH, Olsen P and exchangeable cations are measured from 2000 onwards. Originally there were 12 blocks, but blocks 5-12 were discontinued from 1968. See Johnston (1973) for a discussion of the effects of ley and arable cropping on SOC in blocks 5-12, 1949-1972.

Highfield Ley-arable experiment is a comparison to the Fosters Ley-arable experiment. The two sites have the same soil type but very different histories. Fosters was in long-term arable, with little SOC at the start, in contrast to Highfield which was old permanent grass and consequently had more SOC at the start.

This dataset was assembled by Fergus Blyth from September 2022 to August 2023 as part of a year spent on placement for an MSci degree from the University of Glasgow.

This work was supported by the Natural Environment Research Council [NE/S007423/1], through the ENVISION Doctoral Training Partnership, Research Experience Placement scheme.
description: Ley-arable experiments at Rothamsted on Highfield started in Autumn 1948 on a site that was previously in long-term grassland since at least 1838 (Lawes and Gilbert, 1885). Its purpose was to look at the effects of different cropping systems - permanent grass (now grass/clover), permanent arable and alternating ley/arable - on yield and soil organic matter (SOM). The soil is a silty clay loam. Some plots stayed in permanent grass, some were ploughed and immediately re-seeded, some went into continuous arable cropping where 3-yr arable Test crops followed 3-yr arable Treatment crops and other plots alternated between 3-yr leys as the Treatment crop and 3-yr arable Test crops. 
Originally, six blocks, one for each of the six phases of the rotation, were put down in duplicate, making 12 blocks in each field (with 144 main plots). From 1968, only four blocks on each site continued with original treatments (with 48 main plots), and yields have not been taken since 1990. The old grass plots and re-seeded grass plots were grazed until 1961. They were then split to compare grass+N or grass/clover (clover was under-sown in the grass sward); the whole plots have been treated as grass/clover since 1991. Three types of leys were originally tested; 3-yr lucerne, 3-yr grazed ley or 3-yr cut grass. These, and the arable Treatment and Test crops have changed over the duration of the experiment, with major cropping changes being implemented in 1961, 1990 and 2009. See Rothamsted Experimental Station, 1966; 1970; 1978 and Johnston, 1973 for details about the early years of the experiment and Yields of the Experiments, 1990 (and before) for later details. Further details are available through e-RA.
description: An excel file, 01-HLASOC4814.xlsx, contains the soil carbon and other soil chemical information for 1948-2014. Frictionless CSV files are provided for users who prefer CSV over Excel files. A README tab contains extensive metadata information.
description: The taking of yields from Highfield was halted in 1990 but soil chemical properties are still measured. Analysis of soil organic carbon (SOC) was by the Tinsley technique except 2000, 2008 and 2014 which are by combustion (Total C by LECO minus CaCO<sub>3</sub>-C). Analysis of % nitrogen in soil was by Kjeldahl method in 1987 and by combustion by LECO from 2000 onwards. Exchangeable soil potassium, calcium, magnesium and sodium were all measured using ICP-OES (Inductively Coupled Plasma - Optical Emission Spectrometer). Soil pH in water was measured using a 1:2.5 soil:water suspension. Plant-available phosphorous was determined by the Olsen P method. 

For 1948, 1951, 1956, 1961 and 1967 soils were sampled to a depth of 0-5 and 5-10 inches or 0-6 and 6-12 inches; later soils were all sampled to 0-9 inches (0-23cm). A 0-23cm value for the earlier soils has been calculated. 

Soils were sampled in 2000/1 using an open-ended metal box 15cm x 15cm x 23cm deep to measure bulk density and soil weights on the permanent grass (G) and arable plots (A) only. Permanent grass is assumed to be unchanged and to be the starting value for all other plots in 1948. The soil weights for other years have been derived by extrapolation or interpolation.
description: This dataset is derived from measurements made by the Analytical Chemistry Unit, Rothamsted Research, Harpenden. The Analytical Chemistry Unit follows the Joint Code of Practice (JCoPR) and participates in European Quality Assurance programmes. All performance is strictly monitored using certified external standards alongside in-house standard materials. Standards and check samples are monitored and recorded. The data has been cross checked by Andy Gregory. This dataset includes the full compliment of treatments on Highfield Ley-arable, in contrast to the previous Summary Open Access Dataset (SOAD) that includes only the two extreme treatments. It also contains full metadata in contrast to the previous SOAD.

Analytical techniques:
LECO: LECO Corp., St Joseph, Michigan, USA
 - Tinsley, J. (1950) The determination of organic carbon in soils by dichromic mixtures. In: *Transactions of the 4th International Congress of Soil Science,* Vol. 1 (eds F.A. van Baren, * et al *), pp 161-164. Hoitsema Brothers, Amsterdam. 
 - Bremner, J. M. (1965). Total nitrogen. In: Methods of Soil Analysis. Part 2 (ed. C. A. Black), pp. 1149-1178. Madison: American Society of Agronomy
- Olsen S.R., Cole C.V., Watanabe F.S., Dean L.A. (1954) Estimation of available phosphorus in soils by extraction with sodium bicarbonate. USDA Circular 939, US Gov. Print. Office, Washington, D.C