Environmental parameters affecting the concentration of iodine in New Zealand pasture
journal contributionposted on 27.08.2019 by Hayley Jensen, Barbara Orth, René Reiser, Diane Bürge, Niklas J. Lehto, Peter Almond, Sally Gaw, Barbara Thomson, Linda Lilburne, Brett Robinson
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Iodine (I) is an essential trace element commonly deficient in agricultural systems. Whereas there is much information on I in food crops, there is a lacuna of knowledge on the environmental factors that affect pasture I concentrations. We aimed to identify the most important environmental factors affecting the concentration of I in New Zealand pastures, and the consequences to agricultural systems. Soil and pastoral samples were collected throughout the country and analyzed for I and other elements. The soils contained 1.1 to 86 mg I kg−1, with 0.005 to 1.4 mg kg−1 in the pasture. In 26% of pastures, I concentrations were insufficient for sheep nutrition, whereas 87% contained insufficient I for cattle nutrition. Pasture I concentrations were negatively correlated with the distance from the sea, and the concentration of oxalate-extractable amorphous Al, Fe, and Si oxides, which immobilize soil I. Soil organic C and clay increased I retention in soil but did not significantly affect pasture I concentrations. Future work should investigate how soil properties affect pasture I uptake in inland areas.