IODINE IN THE RECLAIMED UPLAND SOILS OF A FARM IN THE EXMOOR NATIONAL-PARK, DEVON, UK AND ITS IMPACT ON LIVESTOCK HEALTH

Iodine is an essential micronutrient for animals and humans, yet its b ehaviour in the soil environment is not clearly understood. This study centres on one farm in the Exmoor National Park, Southwest England, t ypical of many stock farms in North Devon where livestock grazing upla nd pastures suffer from iodine deficiency disorders. This area is not characteristic of many other recognized areas of endemic iodine defici ency, in that it is: proximal to the ocean; underlain by sandstones; n ot enriched in fluorine, calcium or arsenic; and has not been glaciall y scoured. Iodine deficiency disorders in this area are also a relativ ely recent phenomenon, associated with improved upland grazing. In add ition to the identification of the local sources of iodine, the distri bution of iodine between reclaimed and unreclaimed moorland soils and the differing capacities of reclaimed and unreclaimed soils to retain iodine were also examined. This paper asserts that moorland soil recla mation is an important factor in the aetiology of iodine deficiency di sorders in grazing cattle. The processes of ploughing, drainage and li ming are thought to reduce the capacity of upland soils to retain iodi ne in a bioavailable form.