MORPHOLOGY & MINERALOGY OF
WATER DISPERSIBLE SAND & SILTS
Materials and Methods
Soil samples were collected from the region based on their utilization for crop production and their likelihood of having water dispersible clay (Table 1). Sands and silt fractions were separated by Dr. R. I. Barnhisel. He sent subsamples of these fractions for examination. Sands had been previously dried and silts were obtained as aqueous suspensions which were oven dried. Grains were sprinkled onto a conducting carbon adhesive tab adhered to a 9.5 mm JEOL type SEM stub. The samples were coated with approximately 10 nm of gold using a sputter coater and examined in a JEOL 6400 scanning electron microscope equipped with a Noran EDS system at 25KeV. Minerals were identified using a combination of morphology and the chemcial analysis as determined using EDS (White and Dixon, 1995).
Grain counts for selected silt samples were performed using a transect where all grains were counted which crossed the center of the viewing screen and were sufficiently separated from surrounding grains to produce a separate EDS pattern. No counts were performed on the sand fraction because there were an insufficient number of grains on the sample stubs.
| Next Section |
Previous Section |
Return to Contents |
Last Modified: November 24, 1998
Document Prepared by:
North Carolina Agricultural Research Service
North Carolina State University