Table 1.

Experimental site details

Site, experiment and number	Duration	Clay (%)	Sampling depth (cm)	Crop	Treatments include	Reference
Rothamsteda, Hertfordshire, United Kingdom
Broadbalk (1)	1843—ongoing	20–38	23	W. wheat	Rates of N, FYM, straw	Johnston and Garner (1969), Rothamsted Research (2006)
Hoosfield Barley (2)	1852—ongoing	18–27	”	S. barley	Rates of N, FYM, FYM residues	Jenkinson and Johnston (1977)
Fosters Ley‐arable (3)	1949—ongoing	”	”	Arable crops and leys	All‐arable rotations, 3‐year leys + 3‐year arable rotations, or permanent grass since 1949	Johnston (1973), Johnston et al. (2009)
Highfield Ley‐arable (4)	1949—ongoing	”	”	Arable crops and leys	All‐arable rotations, 3‐year leys + 3‐year arable rotations, or permanent grass since 1838	Johnston (1973), Johnston et al. (2009)
Amounts of Straw (5)	1986–2015	”	”	W. wheat	Wheat straw incorporated since autumn 1986	Powlson, Glendining, Coleman, and Whitmore (2011)
Broadbalk Wilderness (6)	1881—ongoing	20–25	”	Regenerating woodland	None	Poulton et al. (2003)
Geescroft Wilderness (7)	1886—ongoing	”	”	Regenerating woodland	None	Poulton et al. (2003)
Park Grass (8)	1856—ongoing	18–27	”	Permanent pasture	FYM	Warren and Johnston (1964), Fornara et al. (2011)
Exhaustion Land (9)	1852—ongoing	18–27	”	Arable cropsb	FYM, FYM residues	Johnston and Poulton (1977), Johnston et al. (2017)
Woburnc, Bedfordshire, United Kingdom
Amounts of Straw (10)	1986–2015	c. 14	”	W. wheat	Wheat straw incorporated since autumn 1986	Powlson, Glendining, et al. (2011)
Organic Manuring (11)	1965—ongoing	8–13	”	Arable crops and leys	Various organic amendments	Mattingly et al. (1974)
Green Manuring (12)	1936–67	c.13	20	Arable crops	Various organic amendments	Chater and Gasser (1970)
Market Garden (13)	1942—ongoing	10–12	23	Various crops	Various organic amendments from 1942 to 1967	Johnston (1975)
Ley‐arable (14)	1938—ongoing	11–16	25	Arable crops and leys	All‐arable rotations, 3‐ and 8‐year leys + 2‐year arable rotations, FYM every 5 years until mid‐1960s	Johnston et al. (2017)
Saxmundhamd, Suffolk, United Kingdom
Rotation II (15)	1899–1986	c. 25	20	Arable crops	FYM every 4 years	Mattingly, Johnston, and Chater (1969)
Rotation I (16)	1899–2009	”	”	Arable crops	FYM	Williams and Cooke (1971)

^aThe soil at Rothamsted is a flinty silty clay loam over Clay‐with‐flints and is classified as a Chromic Luvisol (IUSS Working Group WRB, 2015).

^bPotatoes were grown continuously from 1876 to 1901; FYM was applied annually during this period.

^cThe soil at Woburn is a sandy loam and is classified as a Cambic Arenosol (IUSS Working Group WRB, 2015).

^dThe soil at Saxmundham is a sandy clay loam derived from boulder clay and is classified as a Eutric Gleysol (IUSS Working Group WRB, 2015).