STUDIES ON IODINE IN BRITISH SOILS

Abstract

SummaryA method for the determination of iodine in soils and other agricultural materials was developed on the basis of an existing Auto‐analyser procedure for iodine in blood.Using this method, soils from twenty‐three widely separated sites in the U.K. were found to have total iodine contents ranging from 2.7 to 36.9 mg/kg. Total iodine contents were not closely correlated with the distance of the site from the coast or with rainfall, indicating that these factors did not exert major effects on iodine content. When two soils derived from marine alluvium were excluded, total soil iodine contents were positively correlated with aluminium oxide extracted by Tamm's reagent (r= 0.88***), with ferric oxide extracted by citrate‐dithionite (r= 0.64**), and with soil organic matter (r = 0.59**).Analysis of twenty‐two fertilizer materials, and of the faeces and urine from sheep fed diets containing two levels of iodine, indicated that inputs of iodine to the soil from these sources were small.From the correlation between total soil iodine contents and other soil properties, together with the proportions of the total iodine extracted by various reagents including sodium hydroxide and oxalic acid, it is concluded that soil iodine is associated, in part, with sesquioxide material and, in part, with soil organic matter.