National Soil Inventory (NSI) samples cover England and Wales on a 5 km grid (6127 sites). The original sampling was from around 1980 and there have been partial resamplings in the mid-1990s.
NSI data includes erosion, land use and lithological information. NSI profile information gives a very detailed description including stone abundance, root descriptions and boundary information.
The NSI topsoil data gives detailed measurements of over 20 elements from the soils, in addition to pH. This information is held by Cranfield University in their Landis database.
Archived material was recently re-analysed at the British Geological Survey by X-ray fluorescence spectrometry (XRFS) yielding new analytical results for more than 50 chemical elements.
A similar set of data also referred to as the National Soil Inventory exists for Scotland (James Hutton Institute, formerly until April 2011 the Macaulay Land Use Research Institute) on a 5 km grid (total 3094 sites). Sites on a 10 km grid (770) include chemical analyses.
NSI soil sampling sites were collected at the intersects of a 5 km orthogonal grid (a grid offset 1 km north and east of the British Ordnance Survey National Grid so sites did not fall on the margin of printed map sheets. The principal interest was agricultural land and did not specifically target urban areas. From 6127 sites visited 5691 soil samples were collected between 1978 and 1983.
Soil sampling was restricted to the uppermost 15 cm of mineral soil (less if bedrock was encountered). Twenty-five cores of soil were taken using a mild-steel, screw-type auger at the nodes of a 4 m grid within a 20 m x 20 m square centred on the site location.
These soil cores were bulked and the target sample weight was 450 g. Samples were double-bagged in food-grade polythene bags and refrigerated on the day of sampling. Within two weeks the soils were air dried on Kraft paper, after which each sample was split into two equal portions.
One portion was kept as a reference sample, the other was milled in a mild-steel roller-mill to pass a 2 mm aperture sieve. A further 25g sub-sample was taken from the <2mm air-dry sample by coning and quartering, and ground to <150 micrometres in an all-agate planetary ball mill.
This sample was used for the determination of Al, Ba, Cd, Ca, Cr, Co, Cu, Fe, Pb, Mg, Mn, Ni, P, K, Na, Sr and Zn extracted by aqua regia, and determined by ICP-AES. The unground <2 mm fraction was also determined for pH (soil-water suspension); organic carbon (dichromate oxidation); available K, Mg (1M ammonium nitrate extraction), and P (0.5 M sodium bicarbonate extraction); and extractable Cd, Co, Cu, Pb, Ni, and Zn (0.05 M ammonium-EDTA extraction).
The 2010 BGS XRFS reanalysis was undertaken on a subsample of ground material upon which the original aqua regia digests were undertaken yielded a large number of total element concentrations for: Ag, Al, As, Ba, Bi, Br, Ca, Cd, Ce, Cl, Cl, Co, Cr, Cs, Cu, Fe2O3, Ga, Ge, Hf, I, In, K, La, Mg, Mn, Mo, Na Nb, Nd, Ni, P, Pb, Pd, Rb, S, Sb, Sc, Se, Si, Sm, Sn, S, Sr, Ta, Te, Th, Ti, Ti, Tl, U, V, W, Y, Yb, Zn and Zr.
The new BGS XRFS data will be released as an electronic atlas in October 2011 and the raw data will become freely available from October 2013.
NSI site and sample information availability (England and Wales) is described on the National Soil Resources Institute (Cranfield University) web page Information on NSI data products.
More information on the Scottish NSI can be obtained by contacting MLURI.
James Hutton Institute (formerly Macaulay Land Use Research Institute) Scottish NSI
McGrath, S P, and Loveland, P J. 1992. The Soil Geochemical Atlas of England and Wales, Blackie Academic and Professional, Glasgow.