Soil Lab Report

Liberty Middle School

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Madison, Alabama, USA
(256) 430-0001

Mr. Johnston (teacher) & Mrs. Carter (student teacher) carter831@hotmail.com

Primary Authors: Natasha, Danny, Adam, Josh
Contributors: Results contributed by Mr. Johnston's entire 1st block class

"WHAT LIES BENEATH"

Introduction

    Mr. Johnston and student teacher Mrs. Carter's 9th grade biology class did a soil experiment on Liberty Campus in Madison, AL by finding the texture, depth, color, structure, moisture and presence of rocks, roots and free carbonates. The class was characterizing the different horizons in the soil in a deep pit and by using the auger method (a shovel like tool that you force in the ground to retrieve dirt). Soil is very helpful to humans and animals. It contains water and inorganic nutrients, which is provided for the plants. The plants then are able to give off oxygen so plants and animals can breathe.

Materials and Methods

  1. Recording Location and Time: Before our class observed anything in the soil, we had to record our location using the GPS (Global Position System [Global Positioning System]). After turning it on, the screen showed a picture of the earth and marks that represented satellites that could be traced. Below the picture was a row of bars that showed the number of satellites that knew where we were. We had to have four filled in bars for our location to be official. The empty bars represented satellites that were searching for us, but couldn't give us a definite location. Then we pushed the page button which took us to another screen which told us our elevation, our position in latitude and longitude, and the present universal time.
  2. Using the Auger: The auger is a drill shaped structure that is designed to take core samples of the soil. First we set down a tarp so we would have something to put the soil on. Then we set the auger on the dirt and turned it 180º [the auger should be turned 360º. See Auger Technique Step-By-Step Guide.], which drove it into the ground. After that, we carefully moved the auger with the soil over to the tarp and emptied the auger out. Using a meter stick, we then measured the depth of the hole that was made by the auger. Then we set the meter stick down next to the soil on the tarp and smashed the soil [In order to keep the soil structure as intact as possible, the soil should be pushed up gently to the appropriate depth.] down to the same height. We continued putting more soil down and measuring it until we reached 1 meter in depth. The point of measuring the hole and smashing the soil down to match it was so we wouldn't think we were 1 meter deep when we still had a long way to go.
  3. Determining Horizon Change: To determine where a horizon or soil layer changes, we looked at several things. The first thing we looked for is color change. Then, we looked for changes in the substances in the soil, the consistency [consistence], structure, and texture. After we determined where the changes were, we marked them with nails.
  4. Determining Color: To determine the color of the soil, we took a ped, or clump, of soil and compared it to the patches of color in our color book After matching the colors we recorded the number that was under the color.
  5. Determining Consistency [Consistence]: To determine the consistency [consistence] of the soil, we took a ped of soil and placed it in between our fingers. Then we squeezed it. If it took little effort to break the ped, it was considered friable. If it took a lot of effort, it was considered firm, and if it took a hammer to smash the ped it was considered extremely firm. If there was no ped that formed, it was considered loose.
  6. Determining Structure: To determine the structure of the soil, we observed the soil on the tarp. If it had very small peds it was considered granular. If it appeared to be in sheets it was considered platy. If the soil was in large peds, it was considered blocky. If it came in vertical pillars with a flat top, it was considered prismatic, and if it came in vertical pillars with a rounded top, it was considered columnar. Some soil however, didn't have any structure. If it appeared to be sand, for example, it was considered single grained and if it was something like a big boulder, it was considered massive.
  7. Determining Texture: To determine the texture of the soil, we took some in our hand and smashed it. If it felt sticky, it was called clay, and if not, it was called loam. This can be recorded using Textural Triangle 1, which is pictured in the results section. After determining whether the soil is clay or loam, we determined whether it was more like sand (gritty), or silt (smooth). This can be recorded in Textural Triangle 2, which is also pictured in the results section.
  8. Determining pH: To determine the pH of the soil, we filtered 25grams of soil through a sieve and put it in a cup. Then, we added 25grams of [distilled] water to the cup. We stirred it for 30 seconds and let it sit for 3 minutes. We then repeated the stirring and sitting step 4 more times. Then we dipped the pH paper into the water and compared it to the corresponding scale on the pH paper container and recorded the number that was under the matching paper color.

Results

    The results of the GPS were 34 deg. N .037 min. N. and 86 deg W. 46.828 min. W. Our elevation was 730 ft. The universal time was 13:57. We took a pH of only the first horizon, which was 9.0. In the first horizon, which from bottom to top was 24 cm [top depth 0 cm, bottom depth 24 cm] we configured that it was moist, the structure was granular, the color was 10yr 4/3, which means it has red in it. The consistence of the soil ended up being loose [If a horizon has a loose consistence then the structure of that horizon must be single-grained. Conversely, if a horizon has a single-grained structure, the consistence must be loose. It is not possible to have a horizon with granular structure that has a loose consistence.], the texture was clay loam sand [Sandy Clay Loam], and it had no rocks, few roots, and no carbonates.
    From bottom to top the second horizon was 51 cm [top depth 24 cm, bottom depth 51 cm]. The soil was moist. The structure was platy. The color, like the first horizon had a red pigment in it, it was 25yr 4/8 [2.5YR 4/8]. The consistence of the soil was friable. The texture was all clay, and there were many rocks, few roots, and no carbonates in the soil. In the last horizon of the pit, it went 72 cm from bottom to top [top depth 51 cm, bottom depth 72 cm]. The soil was moist, structure was platy, color was 10r and 4/8, the consistence was firm, and texture was clay. The soil had many rocks, no roots, and no carbonates.
    With the auger the GPS readings were the same. We were not able to get a pH reading for any of the horizons. The first horizon from top to bottom was 18 cm [top depth 0 cm, bottom depth 18 cm]. The soil was moist, the color was 10yr 5/3, the consistence was friable, the texture was clay loam, and structure was blocky. The soil had no rocks, few roots, and no carbonates. The second horizon from top to bottom was 28 cm [top depth 18 cm, bottom depth 28 cm]. The soil was dry, the color was split between 10r 3/6 and 10yr 6/3. The consistence was friable, texture was clay, and structure was blocky. The soil had many rocks, no roots and carbonates. The third horizon from top to bottom was 54 cm [top depth 28 cm, bottom depth 54 cm]. The soil was moist, color was 2.5yr 4/6, the consistence was friable, texture was clay, and structure was blocky. The soil had few rocks, and no roots or carbonates. The fourth horizon from top to bottom was 69 cm [top depth 54 cm, bottom depth 69 cm]. The soil was moist, the color was 2.5y 4/8. The consistence was firm, texture was clay, and structure was blocky. The soil had few rocks, and no roots or carbonates. The last horizon from top to bottom was 100 cm [top depth 69 cm, bottom depth 100 cm]. The soil was moist, the color was 2.5y 4/8, the consistence was firm, texture was clay sand, and the structure was blocky. The soil had few rocks, and no roots or carbonates.

Discussion

    When I first observed the pit I assumed that the soil's texture felt like clay and it was moist because the soil appeared damp. I could tell that the first horizon in the pit would be granular because pollution of course lands on the first horizon which would give the first horizon a gritty texture. I could also tell that the 3rd horizon in the pit would be firm because the other 2 horizons on top of it packed the soil together tightly.
    I think that because the auger broke up the layers of soil as it was digging that the structure was not read accurately. I believe that the auger's structure should have been platy. There was also a difference between the horizons in the auger and the pit that was because the auger went deeper and that it was not exactly were the pit had been.
    I have learned some information that I didn't know about soil and how it helps human beings. This lab really helped me to understand more about soil.
***Notes in brackets [ ] are comments from the GLOBE Soils team.***

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