Lab 2: Soil Analysis

ANALYSIS OF THE SOIL COMPOSITION

Sediment Test
The soil is composed of many different sized particles. With this simple experiment you can separate the main components of the soil and evaluate their proportions.
1 - Go into a field an collect a sample of soil. Put it in a jar of water. Stir it well and let it settle. Observe and describe the different layers of materials.
2 - In water, particles settle more quickly the bigger they are. It is possible to use this property to determine the amount of each component of the soil. Put 3 parts water and 1 part of soil in the container (try 1 cup soil and three cups of water in a quart jar); shake the container for 5 minutes and let the material set. With reference to the figure 1, after 40 seconds measure the thickness of sediment. Call this A; after 30 minutes measure again and call this B; after 24 hours measure C. Now, by subtraction, you can determine the thickness of the main layers: C-B = layer of clay, B-A = layer of silt, A = layer of gravel and sand. Using a sieve with 2 mm holes (less than 1/8 inches), you can separate the gravel from the sand and determine their ratio. On the basis of these data, calculate the content (%) of each component of the soil sample.
3 - Repeat the same experiment with soil collected in other places or that have a different geological origin (i.e: meadow, wood, river bank) or anyplace the soil has a different consistency or texture (i.e: muddy, sandy). Describe the composition of each soil and try to explain the differences. You can also apply this technique to evaluate the composition of the soil for a potted plant, and correct it. Example: if water doesn't drain well, would more sand help? If it needs to hold water longer would clay or organic matter be helpful?
4 - With a microscope, measure the size of the particles. With a clock, measure the time to drop to the bottom of a jar of water. time of the particles in water as a verses their size. Then graph with the Y-axis for the size of the particle and X-axis the time to fall.
http://interactive.usask.ca/skinteractive/modules/agriculture/activities/soil.html
pH Test
1. Mix the soil sample with a little bit of water. Use the pH paper to test the pH of the sample.
2. Repeat with all the samples.
3. Record the pH of each sample.
Free Carbonate Test
This test is performed by squirting vinegar on the soil. If free carbonates are present, they will "effervesce" or bubble when the vinegar reacts with them. Record one of the following based on your observation:
None: you observe no reaction (the soil has no free carbonates).
Slight: you observe a slight amount of bubbling (the soil is coated with some carbonates).
Strong: you observe a strong reaction (many bubbles) (the soil has many carbonate coatings present).

QUESTIONS:
1. WHICH SOIL SAMPLE WAS POSITIVE FOR THE CARBONATE TEST? WHAT CAUSES THIS REACTION?
2. WHICH SAMPLES ARE ACIDIC OR BASIC? WHERE WOULD THESE SAMPLES BE FOUND?
3. BASED ON YOUR DATA ON THE SEDIMENTATION TEST, WHAT PARTICLES/SUBSTANCES ARE FOUND THE MOST IN THE SOIL SAMPLES?