EFFECT OF PHOSPHATE FERTILIZERS AND ATMOSPHERIC DEPOSITION ON LONG-TERM CHANGES IN THE CADMIUM CONTENT OF SOILS AND CROPS

Trends are reported in the Cd content of herbage collected and stored from the Park Grass Experiment at Rothamsted Experimental Station, a semirural location in the U.K. Samples from 1861 to 1992 were bulked for 5-year periods from two phosphate fertilizer-treated plots, now with soil pH 4.9 (unlimed) and 6.5 (limed), respectively. Analysis of Cd was by Zeeman correction GFAAS following a nitric acid digestion. The data are compared with those from control plots which have not received superphosphate. On the unlimed plots, levels of Cd in the herbage from the phosphate-treated plot were very similar to those on the control for the years to 1930; whereas from 1940 to the present, the Cd concentrations in herbage were considerably greater on the phosphate-treated plot. On the limed plots, Cd concentrations in the herbage from both the phosphate-treated and control plots have remained similar to each other, although both plots exhibit a small increase of about 1 mu g of Cd kg(-1) year(-1) since the beginning of the liming treatment in 1903.