Aquic Conditions in Andisols of the Northwest USA
- P. A McDaniel,
- J. H. Huddleston,
- C. L. Ping and
- S. L. McGeehan
The distribution and extent of wet Andisols in the northwest USA have not been well documented; however, it is apparent that field recognition of hydric soil indicators or aquic conditions presents unique problems in these soils. Field data from Andisols of this region suggest that expression of redoximorphic features may be considerably less than would be expected on the basis of duration of saturated conditions and measured oxidation-reduction (Eh) potentials. Aquands from southeastern Alaska exhibit reddish hues and high chromas despite being saturated during the summer. Somewhat poorly drained Andisols in central Oregon have prolonged high water tables during spring and summer months and Eh values fall below 200 mV. These soils contain redoximorphic features, but they are less pronounced than in nonandic soils of the area having similar drainage classes. Studies in Idaho indicate that Fe concentrations are often weakly expressed or absent in wet, ash-influenced soils. Additionally, it appears to be difficult to reduce and solubi-lize Fe contained in the poorly crystalline hydrous oxides that impart reddish hues and high chromas to many Andisols. Concentrations of soluble Fe and Mn in Andisols saturated and reduced under laboratory conditions were as much as 10 times less than those in nonash soils after 20 d. Resistance to reduction may be due to sorption of silicate, organic, and/or amorphous A1 hydroxide phases, thereby inhibiting formation of low chroma Fe depletions. Results suggest that identification of wet Andisols using morphological indicators may require application of different criteria than those used for nonandic soils.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 1997. . Copyright © 1997 by the Soil Science Society of America, Inc., 5585 Guilford Rd., Madison, WI 53711 USA