Retrospective analysis of an archived soil collection. I. Metals.

Soil samples collected and stored from the mid-1800s to the present-day have been analysed recently for a number of elements. The samples from long-term experiments under permanent grassland and continuous arable crops at Rothamsted Experimental Station (U.K.) were selected to investigate time trends in elemental composition due either solely to atmospheric deposition or to a combination of atmospheric deposition and various soil treatments.

There was no measurable increase in soil Pb from atmospheric deposition during 100 years in one experiment at Rothamsted, and ∼ 15% increase since the mid/late-1800s in two others. A predicted increase of ∼ 11% in the plough layer Pb burden this century was derived from estimates of Pb deposition between 1900 and the present day.

Treatment effects due to additions of farmyard manure (FYM) (for Cu, Pb and Zn) were also observed, although there were none due to additions of phosphate fertilisers. Soils receiving annual applications of 35t FYM ha−1 now have concentrations of 37 mg Cu kg−, 70 mg Pb kg−1 and 142 mg Zn kg−1 in the plough layer; unmanured plots contain 28 mg Cu kg−1, 40 mg Pb kg−1 and 83 mg Zn kg−1.

Soil Sr has declined from 104 mg kg−1 in 1856 to 66 mg kg−1 in 1980 in neutral or slightly calcareous soils under wheat; no such change was observed in acid soils, relatively high in organic matter and under permanent grassland. The elements Co, Cr, Mo, Ni, Rb, V, Y and Zr showed no consistent changes which could be associated with either atmospheric or treatment inputs.

RESP-09821