New Zealand Journal of Agricultural Research abstracts

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Fluoride: A review of its fate, bioavailability, and risks of fluorosis in grazed-pasture systems in New Zealand

S. J. CRONIN
V. MANOHARAN*
M. J. HEDLEY
P. LOGANATHAN

Department of Soil Science and Fertilizer and
Lime Research Centre
Institute of Natural Resources
Massey University
Private Bag 11 222
Palmerston North, New Zealand

*Present address: School of Land and Food Sciences, University of Queensland, St Lucia, Queensland 4072, Australia.

Abstract  Fluoride (F) is an essential element for animal growth, not readily taken up by plants from soils, yet cases of acute fluorosis in grazing animals caused by ingestion of phosphatic fertilisers, volcanic ash, and industrial wastes remind us of its potential hazard. Fluoride concentrations in topsoils slowly increase where annual inputs through atmospheric pollution and phosphatic fertilisers exceed losses. This paper reviews information on the fate of F in grazed pasture systems with the aim of assessing the potential toxicity of accumulating soil F. A preliminary F-cycling model for grazed pastures, based on the review of international literature and F concentrations in selected New Zealand pasture soils, indicated that grazing sheep and cattle obtain over 50% of their dietary F (and this may be >80% during winter) from soil ingestion. The model suggests that at the extremes of the ranges of the measured winter soil ingestion (143-300 g d^-1 for sheep and 900-1600 g d^-1 for cattle) and dietary F absorptivity (bioavailability) of soil F (20-38%), total topsoil F concentrations in the range of 372-1461 ug F g^-1 could cause chronic fluorosis in sheep and 326-1085 ug F g^-1 in cattle. We recommend that research is undertaken to measure F accumulation rates and soil F dietary absorptivity for a range of intensively managed New Zealand pasture soils.

Keywords  cattle; fluoride; pasture; fluoride bioavailability; fluorosis; phosphate fertilisers; sheep; soil ingestion; volcanic ash

New Zealand Journal of Agricultural Research, 2000, Vol 43: 295-321

0028-8233/00/4303-0295 $7.00/0 (c) The Royal Society of New Zealand 2000

PDF file of entire paper: medium quality (2847K); (scanned from paper original: notes about this process)

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