Agriculture Reference
In-Depth Information
Figure 8.5
Cheto montmorillonite associated with amorphous silica (arrow). (EM by R.C. Jones.)
CONCLUSION
The chemistry and physics of soils depend so much on the nature and extent of surfaces that
renewed research in this area may be worthwhile. Jones et al.Ôs (2000) method for quantifying and
determining the chemical composition of amorphous materials provides that basis for new research
to answer the following questions:
1.
How extensive is the occurrence of amorphous materials in non-Andisols?
2.
Will, for example, 5% to 10% by weight in the clay fraction be common for most soils?
3.
Will knowledge of the amount and chemical composition of amorphous materials in clay fractions
add signiÝcantly to explaining variances in soil behavior and performance?
4.
How important are amorphous coatings on the behavior of coarse-textured soils?
5.
Will the silica-sesquioxide ratio of the amorphous fraction inÞuence its surface charge character-
istics?
6.
Does the amount and composition of the amorphous fraction inÞuence the carbon sequestration
potential of soils?
REFERENCES
Hashimoto, I. and Jackson, M.L. 1958.
Rapid Dissolution of Allophane and Kaolinite-halloysite after Dehy-
dration.
Reprint from 7
National Conference on Clays and Clay Minerals. Pergomon Press, New
th
York, 102Ï113.
Jones, R.C., Babcock, C.J., and Knowlton, W.B. 2000. Estimation of the total amorphous content of Hawaii
soils by the Rietveld Method.
64:1100Ï1108.
Jones, R.C. and Uehara, G. 1973. Amorphous coatings on mineral surfaces.
Soil Sci. Soc. Am. J.
Soil Sci. Soc. Am. Proc.
37:792Ï798.
Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classiÝcation for making and interpreting soil
surveys. 2
Ed. USDA Agric. Handbook 436. U.S. Government Printing OfÝce, Washington, DC.
nd
