
Soil texture by feel
Soil texture is determined by the percent of sand, silt and clay in a given soil. Sand particles
range in size from 0.05 mm to 2.0 mm, silt ranges from 0.002 mm to 0.05 mm and clay is any
soil particle less than 0.002 mm. A particle size analysis can be performed to come up with the
percentages of sand, silt and clay. A soil texture triangle gives names associated with the various
combinations of sand, silt and clay known as classes. Alternatively, texture can be determined by
feel by following the page below. This method is not exact but is a great way to come up with a
general sense of soil type.
Comparative size of
sands, silt and clay.
If clay was the size of
a dot on the page, silt
and sands would be
comparative size.
Soil Texture Activity
Follow directions in the diagram below and complete for Soil #1 and Soil #2.
What is the texture of Soil #1?______________________________________
What is the texture of Soil #2?______________________________________

Soil Erosion
Soil erosion is the movement of soil from its place of origin to another location. This is
primarily caused when soils are bare and rainfall splash or water running over the surface of the
ground or strong winds dislodge and relocate it. Often the displaced soil, also known as
sediment enters streams, rivers and lakes causing the water to become turbid. Increased turbidity
is problematic for aquatic organisms, especially for salmon and steelhead species in the Rogue
Valley. Turbid water can be abrasive to the gills of fish, reduces visibility which affects their
ability to feed, and decreases photosynthesis of aquatic plants, increases water temperature and
when the sediment settles it can bury fish eggs.
The amount of turbidity in a waterway is dependent on the texture of the displaced soil entering
into it. Heavier, coarser soil particles like sand are less likely to become displaced compared to
finer soil particles like silt and clay because water is better able to drain into a sandy profile and
not run off. Additionally if sands do enter the water they will settle out more quickly due to their
greater mass, reducing their effect on turbidity levels.
Local stormwater management is based on regulations from the Clean Water Act under the
NPDES Phase II Program. Management programs are designed to meet the six minimum control
measures listed below. Many of the concepts incorporated are based on mimicking or
reestablishing natural functions.
Six minimum control measures:
1.
2.
3.
4.
5.
6.
Public Education and Outreach
Public Involvement and Participation
Illicit Discharge Detection and Elimination
Construction Site Runoff Control (Erosion Prevention and Sediment Control)
Post Construction Runoff Control
Pollution Prevention/Good Housekeeping
Turbidity exceeding 50 NTU’s is considered as water quality impaired. This threshold was
established by OWEB. Turbidity exceeding 50 NTU’s interferes with the sight-feeding of
salmonids and therefore provides a direct indicator of the biological effect.
Turbidity Activity
Place a teaspoon of Soil #1 into Mason Jar #1. Fill the jar with water and shake for 15 seconds.
Repeat this procedure with Soil #2 and Mason Jar #2. Let the soil settle for one minute than
record the turbidity of each sample using the Hach Model YSI 30 Turbidimeter.
What is the turbidity reading for Soil #1?______________
What is the turbidity reading for Soil #2?______________
Explain why the turbidity reading for Soil #1 is higher than Soil #2?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Splash Zone Activity
Activity Procedures
Splash Zone
1. Divide into groups.
2. Give each group a Splash Zone Target, eyedropper, and a small container of water.
3. Put enough soil from Soil #1 (about ½ teaspoon of dry soil) in the center of their target to just
cover the center circle.
4. Fill the eyedropper with water.
5. Hold the eyedropper about 18 inches (or 46 cm) above Soil #1.
6. Drop 5 drops of water directly onto the soil sample. If a drop misses the soil, continue until 5
drops hit the soil.
7. Record the number of water “splashes”---drops containing soil—in each zone.
8. Complete the graph to show your results.
9. Repeat with Soil #2.
Explain why the number of water “splashes”---drops containing soil---in each zone was higher
for Soil #1 compared to soil #2?____________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Soil #1
Soil #2

What can be done to prevent soil erosion
Employ a rain barrel or other form of water catchment system to divert water from entering
storm drains.
Plant trees and shrubbery along slopes.
Plant a rain garden to soak up excess moisture and stop runoff (insert a link).
Use mulch whenever possible.
Build terraces or a retaining wall. Any mid-yard structure will do a good job of stopping water
and soil from leaving your yard.
Plant native plants with absorbent root stuctures.
Contour farming, filter strips and cover crops.
Reduce or eliminate the amount of bare ground.