WSP07583

• File Number: 8270.200
• Description: Selenium
• State: CO
• Basin: Gunnison
• Water Division: 4
• Date: 1/1/1996
• Author: USGS
• Title: Detailed Study of Selenium and Other Constituents in Water-Bottom Sediment-Soil-Alfalfa and Biota Associated with Irrigation Drainage - Uncompahgre Project Area and in the Grand Valley - 1991-93
• Water Supply Pro - Doc Type: Report/Study

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Figure 6. Distribution 01 soil.sampling sites within townships in Irrigated areas 01 the
Uncompahgre Project.

Soil cores of I m were removed using a
9-cm bucket auger, and the entire core was homoge-
nized by mixing in a plastic container. A I-kg
portion of the I-m core mixture was placed in a paper
bag for transport to the laboratory. The top 20 cm
of several alfalfa plants (Medicago sativa L.) at
lO-percent bloom stage were sampled within a
few meters of the auger bore, composited, placed
in paper bags, and air dried. At several sites,
alfalfa could not be obtained, and only the soil
cores were taken.

Sample Preparation and
Analytical Methods

Soil samples were air dried in the laboratory at
ambient room temperature (about 20oC), disaggre.
gated using a mechanical mortar and pestle, and
sieved to pass a 2-mm screen (10 mesh). A split of
this material was ground to less than 100 mesh using a
ceramic-plate grinder. The split was used for total
analysis; the unground, 2-mm fraction was used for
extractions. Field-dried alfalfa samples were washed

SOILS AND ALFALFA INVESTIGATIONS 17