Fluoride accumulation in pasture forages and soils following long-term applications of phosphorus fertilisers

Ingestion of soils with high fluoride (F) concentration may cause chronic f luorosis in grazing animals. Analysis of New Zealand pasture soils with lon g-term phosphorus (P) fertilisation histories showed that total surface soi l (0-75 mm depth) F concentration increased up to 217-454 mg kg(-1) with P fertiliser application, One-third to two-thirds of F applied in fertilisers resides in the top 75 mm soil depth. Pasture forage accumulation of F was low, and therefore, F intake by grazing animals through pasture consumption is expected to be much lower than F intake by soil ingestion. Ten annual a pplications of single superphosphate (30 and 60 kg P ha(-1) year(-1)) to a Pallic Soil (Aeric Fragiaqualf) significantly increased total F and labile F (0.01 M CaCl2 extract) concentrations to 200 and 120 mm depths, respectiv ely, of the 300 mm. depth investigated. The mobility of F in the soil profi le was similar to two other elements, P and cadmium derived from the fertil iser. (C) 2001 Elsevier Science Ltd. All rights reserved.