DOI: 10.23637/wrn3-soc3809-01
title: Dataset: Woburn Ley-arable experiment soil organic carbon, 1938-2009

description: This dataset gives the % soil organic carbon (SOC) and % total nitrogen (N) in the topsoil (0-25cm) of all plots and blocks of the Woburn Ley-arable Experiment, 1938-2009. Baseline measurements were taken in March 1938 at the start of the experiment, then the soil in each block was sampled regularly every five years from 1955, to coincide with the end of the third treatment year or the last year of the eight-year leys. Soil N was measured from 1980 onwards. Also included are estimates of soil bulk density. This dataset must be read in conjunction with **Johnston et al, 2017 **, which gives the full background, summarises the %SOC data (mean of the five blocks), and gives estimates of total organic carbon in t/ha and estimated annual inputs of C from each rotation.
description: The Woburn Ley-arable Experiment, started in 1938, compares the effects of continuous arable rotations and ley-arable rotations on soil organic matter and the yield of two arable test crops, on a sandy loam soil. It consists of 80 main plots, divided over five blocks. Half the plots have been in four continuous five-year arable or ley-arable rotations since 1938: three years of treatment crops followed by two arable test crops. The treatments were: **AB** (all arable rotation); **AF** (arable rotation with roots or fallow); **LN3** (3-year grass ley with fertilizer N); **LC3** (3-year legume or grass/clover ley). 
The other 40 plots were in alternating rotations from 1938 to the mid-1970s: a 20-year cycle of all four arable and ley-arable rotations. These were replaced by eight-year grass or grass/clover leys in the mid-1970s: **LN8** (8-year grass leys with fertilizer N, followed by two arable test crops); **LC8** (8-year grass/clover leys, followed by two arable test crops). The rotations are phased in over a five-year period in the five different blocks, so that each year of the five-year rotation is present each year. The eight-year leys were also phased in, the first cycle starting 1973-77, the second cycle 1978-82.
description: The main plots are in pairs, one of each pair received FYM (farmyard manure) applied every fifth year, to the first test crop, 1941-1967. %SOC and total N in air-dried ground soil (&lt;355 µm), 0-25cm. Organic C by the Tinsley method (Tinsley, 1950) 1938-1979, then by total combustion (LECO). Total soil N by total combustion (LECO). Estimated bulk density from Johnston et al, 2017. Soil samples were taken from the centre of each plot and consisted of 16-25 cores taken with a 2.5cm semi-cylindrical sampler, bulked together. Most samples were taken from the 0-25cm soil layer; for the few samples taken to 23cm, %SOC and %N were adjusted to a 0-25cm depth basis with an appropriate proportion of the %SOC in the subsoil.
description: Materials and methods from Johnston et al, 2017. The %SOC and total soil N data 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. - 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.