Soil Texture Lab Name:____________________________
Introduction:
The major component in soils is rock particles: sand, silt & clay. These particles form over time from weathering and erosion. The particles are classified by size: sand is the largest (.05-2.0mm) and the individual grains can be seen by the naked eye; silt is smaller
(.002-.05mm) and the individual grains cannot be seen the naked eye; nor can individual clay particles, the smallest particle (<.002mm). (Anything over 2.0 mm is considered a pebble.)
The composition of these three particles in an area is determined by five factors: parent material of the area, climate, vegetation, time and topography. Because all of these factors vary, soils, even in the same region, also vary. Because two of the particle types are too small to be seen without microscopes, soil scientists have come to rely on different ways to determine particle composition: texture, or the ‘feel’ of the soil, and gravimetric weight, determined by how soils settle in a water column
.
How a soil feels is determined by the composition of particles – sand, silt, and clay - in the soil. Sand feels grainy or gritty; silt feels floury and forms short ribbons (< 2.5 cm long) when squeezed and pushed between and through the thumb and index finger; and clay feels sticky, forms a ribbon more than 2.5cm long, and remains balled up overnight when wet. Soils are rarely composed of only one or the other of these particles, but contain a combination of the three. A perfectly balanced combination is called a‘ loam.’
Most soils are weighted toward one of the particles, which is reflected in the name, such as sandy loam, clay loam, silty clay, etc. For the purposes of this activity, no one is expected to be able to identify soil types with exactitude. The activity is more to provide a general of idea of the different types of particles and soils and to help identify the major particle in each sample.
The three rock particles create the bulk of soil (about 45%). The other components of soil include organic matter (about 5%): micro and macro-organisms, (such as mites, nematodes, and earthworms), vegetation; other organic matter (such as pebbles, and twigs), water (about 25%), and air (about 25%). The particles in a soil determine the amount and types of the other components. Particles determine the type of vegetation and organisms that can be supported, the amount of water and air it can hold, and its suitability for different purposes.
In this activity, we will utilize the Textural Triangle to classify soil by the gravimetric test
(letting it settle in the graduate cylinder after the soil/water mixture is suspended) and by the feel test. The triangle was devised by and for soil scientists in order to separate soils into a number of categories based upon texture and composition. The Texture Guide will assist students in determining into which category the soil samples fall.
Materials: 50 ml graduated cylinder, plastic wrap and rubber band, ruler, water bottle, calculators, and soil samples.

Texture by Feel
Follow the flow chart on how to classify soil texture by feel by using the Guide to
Texture by Feel diagram on the next page for each of your soil samples. Record your determinations below.
Non-forested Soil Texture Classification: ___________________________________
Forested Soil Texture Classification: _______________________________________
Gravimetric Texture Test
Perform this test just like you saw it being done in the video. Show your math work and I should see lines ruler drawn and intersecting on the Texture Triangle, which is located on the last page. Remember divide your sand, silt, and clay volume for each sample by the total volume of sediment in that sample and multiply by a hundred to get a percent.
Non-forested Soil Forested Soil
Sand % __________ Sand % ___________
Silt % ___________ Silt % ____________
Clay % ___________ Clay % ___________
Texture Classification: _______________ Texture Classification: _______________
Data Analysis
1. Do your classification determinations from each different texture test for each soil sample agree with one another? Which test type do you feel more confident about?
Why?
2. Draw your soil profile sketches from our field experience below and identify as forested or non-forested along with showing their different horizons with their measured thickness for each below.

References
- Soil Texture video. http://www.hippocampus.org/Environmental%20Science Accessed
8/25/2010.
- Soil Texture and Composition Lab. http://www.bsu.edu/web/fseec/pie/Lessonplans.htm
Accessed 8/25/2010.