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Lysimeters filled with Freedom silt loam soil (fine‐silty, mixed, mesic, Xerollic Calciorthids) were irrigated with geothermal well water from south central Idaho. The water contained 7 mg F/L. Alfalfa (Medicago sativa L.) was grown in the lysimeters and the water was applied at a rate to give either a 0.30 or 0.15 leaching fraction. After irrigating the 1.0 m deep soil samples for 600 d, over 98% of the added F remained in the soil. Soil extract and lysimeter leachate analysis showed that fluorite precipitation was occurring in the upper profile, but only after another fluoride adsorption mechanism was saturated and the fluoride and calcium ion activities exceeded the CaF2 ion activity product. The F concentration in the upper profile extracts exceeded 20 mg F/L and with the additional high F water irrigation, the soluble F would be expected to leach deeper in the soil. Under field conditions the F would be expected to eventually move into the groundwater with continued irrigation with high F water.

The extensive loess deposits of southcentral and southeastern Idaho have been delineated and mapped. Depth of the loess over much of this area is between 50 to 100 cm thick. The thickest loess deposits are south and east of the Snake River where depths of loess up to 36 m have been measured. Thickest loess deposits are parallel and immediately adjacent to the Snake River. Loess source in the uplands in southeastern Idaho appears to be the Snake River Plain. No pattern of loess sorting was evident on the Snake River Plain; however, there was sorting in the uplands to the southeast of the plain and perpendicular to the Snake River.

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