CHANGES IN THE SULFUR STATUS OF BRITISH WHEAT-GRAIN IN THE LAST DECADE, AND ITS GEOGRAPHICAL-DISTRIBUTION

In 1992 and 1993, respectively, 400 and 393 wheat grain samples were c ollected representatively from the major wheat-growing areas in Britai n. Concentrations of S in the grain and the N:S ratios were determined , and the variations due to variety and geographical distribution were analysed. Grain S concentration ranged from 0.54 to 2.09, with a mean of 1.43 mg g(-1) in 1992, and from 0.80 to 1.67, with a mean of 1.26 mg g(-1) in 1993. The ranges of grain N:S ratio were 13.3-29.6, with a mean of 15.8 in 1992, and 11.5-25.9, mean 15.6 in 1993. Breadmaking v arieties contained significantly greater N and S concentrations in the grain than other varieties, but only small differences were found in the N:S ratio in grain. In 1992 and 1993, 7 and 26% of the samples had a S concentration below the critical value of 1.2 mg g(-1), respectiv ely, whereas 10 and 7% of the samples had an N:S ratio greater than th e critical value of 17. In both years 2.5% of the samples satisfied bo th criteria of S deficiency. Comparison of the results of 1992-1993 wi th those of 1981-1982 (Byers et al, J Sci Food Agric 38 (1987) 151-160 ) showed a significant decrease in the S status of British wheat grain during the 10-12 year period. The decrease can be attributed mainly t o decreased S inputs, particularly from atmospheric deposition. The pa ttern of geographical distribution of grain S concentrations was not a s strong as it was in the 1982 survey. However, it was still apparent that grain samples with small S concentrations were located mainly in Scotland, northern England, and the west and southwest of England, whe reas the largest S concentrations occurred mainly in the areas near to or down-wind of the industrial conurbations of central England.