Introduction to Soil

The major components of soil are mineral matter (sand, silt, and clay), organic matter, water, and air. Soil consists of minerals, air, water, and living matter that accumulate in layers and become compacted over time. Dirt is the displaced soil that can’t be easily associated to where it originated.

Soil formation is affected by 5 factors: climate, organisms, topography, parent material, and time. First, parent material is broken down through weathering. Then, biological activities allows for accumulation of organic matter. This process is very slow.

One major factor when examining soil is clay, silt, and sand distributed evenly (loam). Another factor is the size of particles which affects liquid and air flowing through the soil (porosity). Soil color provides important information on many of the chemical characteristics of soil and on the drainage class and general behaviors of water in soil. It may also help soil scientists in classifying the soil. Generally the darker, more moist soils are the more nutritious soils compared to lighter, drier soils because the darker colors usually indicate more humus. Structure can tell you if the soil is strong or weak. If it is strong than it can stay together under stress and allows for better water movement through the soil. If it is weak it will fall apart under stress. Soil pH influences the solubility of nutrients. It also affects the activity of micro-organisms responsible for breaking down organic matter in the soil.

(http://www.oneplan.org/Water/soil-triangle.asp)

This is a soil texture triangle that shows the percentages of the 3 components in different kinds of soils.

Illinois soil is usually dark brown or black. Silt loam (0-50% sand, 0-28% clay, 50-80% silt) and silty clay loam (0-20% sand, 40-70% silt, 28-40% clay) textures are very common in Illinois. This has a fine texture and forms ribbons that breaks into pieces. The pH of Illinois soil is mainly 6.0-6.5 which is slightly acidic.Hawaii soil is usually reddish and has mainly silty clay soil (40-60% silt, 0-20% sand, 40-60%). Georgia soil is also usually red and has clay soil (40-100% clay, 0-40% silt, 0-45% sand). Arizona also has red soil and has a lot of clay (40-100% clay, 0-40% silt, 0-45% sand). Illinois, Hawaii, and Georgia have acid soil while Arizona has more alkaline soil.

(http://www.allposters.com/-sp/Tree-Roots-in-Laterite-Soil-Formed-from-Tropical-Weathering-of-Basaltic-Lava-Flows-Kauai-Hawaii-Posters_i9004690_.htm)
Hawaii Soil

(http://www.uvm.edu/cosmolab/?Page=projects/soil/soil.html)
Georgia Soil

(http://www.ehow.com/about_6577550_type-soil-arizona-have_.html)
Arizona Soil

(http://www.illinoissoils.org)
Illinois Soil

One economic reasons why farmers should be interested in soil analysis is because if a farmer is able to have/create healthy soil with equal amounts of sand, silt, and clay then the farmer will be able to grow more larger, better tasting crops. Another economic reason is that the farmer won’t have to waste money on extra fertilizers and farming products if he/she knows exactly what he soil needs. One social reasons for a farmer to be interested in soil analysis is that if the farmer knows about his/her soil than they can help prevent run-off and thus reduce pollution because the farmer will know what nutrients need to be added and won’t add extra. Another social reason is that the farmer will be able to have healthy soil and know how to take care of the soil which will allow the farmer to not ruin his/her land that he/she can’t use it.

Collecting Our Soil

We collected our soil semi-close to a school but it was by baseball fields and right by plants such as trees. There should be nothing that should affect our test results. Because there should be no one walking on this soil and there are no pavements or building that are relatively close.When we collected the soil the weather, an abiotic factor, was relatively cold and dry. The dirt was surrounded by grass and right by trees. The dirt did contain roots showing there were biotic factors in the soil. Soil is composed of minerals, organic matter and air/water. Therefore there was organic matter present such as the roots and the decaying material such as humus due to decomposition of leaves and other organic materials. The soil is broken up into clumps. Although there are some bigger chunks of soil, for the most part they are small clumps. The soil is clumpy but it is soft. As you can see there are leaves and roots in the soil as well.

The soil in the Ziploc bag. As you can see it has roots and leaves in the soil and is in little clumps

Digging into the soil with our spoons. 

Maddie digging our hole for the soil. As you can see there are plants all around our soil. 

Soil Texture Qualitative Test

     In this experiment, we took a small amount of soil and added a few drops of water to the soil so that it was moist. Once moist, we played with the soil and squeezed it on hands to feel the texture and to find out what our soil is made of. After observing the soil's texture it was clear our soil had a lot of clay in it because the texture was smooth and thick and looked like clay. We believe our soil is mainly clay due to the fact that the moist soil looked like clay and had a thick, sticky texture.

Here you can see the moist clay being squeezed between the fingers. You can see that the soil looks thick.

In this picture you can really see how the soil looks like clay and that it is thick and sticky.

Soil Texture Quantitative Test

     In this experiment, we placed 65mL of our soil into a 100mL graduated cylinder. Then added water until the level got to the 100mL mark. Next, we put our hand over the open end of the graduated cylinder and shook the graduated cylinder until the soil and water was mixed thoroughly. Once the soil and water were completely mixed, the graduated cylinder was placed at our lab table for 24 hours to allow the soil to settle out. Once the soil settled out, we used a yard stick to measure each layer of the soil and the whole soil together. We measured that 12.4 cm was clay, 0.4cm was sand, and 0.3 was silt.

Here we can see the soil being measured to 65mL.

Water was added to the soil until the level was at 100mL, as seen in the picture.

The soil and water was shook until completely mixed.

After being shook the soil and water measured 72mL. You can see that parts of our soil is sticking to the edges of the graduated cylinder which hints towards our soil being clay.

After 24 hours, you can see the clay, sand, and silt settle out. The sand is on the bottom, then the silt, and then the clay on top. You can see a layer of water on top of the clay and a layer of humus on top of the water.

The yard stick was placed next to the graduated cylinder. There was 12.4cm of clay, 0.4cm of sand, and 0.3cm of silt.

Using these measurements, we calculated the percent of sand, clay, and silt in our soil.  We found that there is 81.05% clay, 2.61% sand, and 1.96% silt. 

After looking at our percents, we determined our soil is clay. Our shaded region is a little bigger  because our percents of clay, sand, and silt did not come out to 100% because there was also water and humus in the soil.

     Our qualitative and quantitative results match because they both said that our soil was clay. Even during our quantitative test you could see the moist soil sticking to the graduated cylinder, which was like in he qualitative test of how the soil had clay properties.
   
     Our percolation test and quantitative test results did match because in the percolation test the soil had an elapsed time of 26.5 seconds and a water volume of 71.8mL. these numbers were very similar to the clay's numbers of 29.0 seconds and 63.5mL. This hints that our soil had a lot of clay in it. Our quantitative results also showed that our soil had a lot of clay.

     My group got our soil by the school and our soil was mainly clay. Hannah's group, who got their soil from cuba marsh, had mainly silt soil. Troy's group, who got their soil from his backyard, had an equal amount of all three components. Although they had an equal amount of sand, silt, and clay, on the texture triangle this soil still falls under clay soil. According to the United States Geological Survey, clay deposits can only form under certain geological conditions. The only environments that clay deposits can form under are soil horizons, continental and marine sediments, geothermal fields, volcanic deposits and weathering rock formations. The area around the school that we got our soil could be soil horizon or from sediments. Troy's backyard would also need to have one of these conditions to form clay soil. Silt soil is formed usually in wetlands when rock is eroded by water and ice. As flowing water transports tiny rock fragments, they hit the sides and bottoms of stream beds, which cause them to break off more rock. The particles grind against each other and become smaller and smaller until they are silt-size. The cuba marsh has a wetland in it, which can explain why Hannah's group got silty soil.

Soil Moisture Test

     In this experiment, we weighed a small tray of aluminum foil, then was placed several spoonfuls of our soil on to the tray and weighed the tray with the soil. Next we placed the tray with the soil into a drying oven for 24 hours at a temperature around 90-95 degrees. This allowed the soil to dry and evaporate the water out of the soil. after being dried for 24 hours, the soil was taken out and we let it cool for a couple minutes and then we weighed the tray and soil again. After being dried, the soil lost 19.1 grams, which is most likely all from water.

The aluminum foil weighed 3.3grams.

The moist soil weighed 69.5grams.

The dry soil weighed 50.4 grams.

The percent water, by mass, in our soil was 37.90%.

     Our soil texture test and soil moisture test were similar because both showed the soil was mainly clay. Our soil was able to hold 19.1 grams of water which goes with the idea of our soil being clay, as found in the soil texture test, because the clay has smaller particles which means it holds more water because it has poor drainage.

     

     We learned that sand, the largest particle, has a better drainage system than clay, smallest particle, which meant that the sand held less water than the clay. Silt, the medium size particle, would hold more water than sand but less than clay. This means there is a correlation between texture and moisture because depending on what type of particle the soil contains, the soil will be more moist (hold more water) if the particle is smaller and will be less moist (hold less water) if the particle is larger.

Percent Organic Matter

We put the soil in the drying oven overnight at a temperature of 90-95 degrees Celsius to get rid of the water in our soil. After the soil has been in the drying oven we weighed the crucible, which was 53.1g. We then weighed the crucible with the dried out soil, which was 61.4 . Before we used the bunsen burners we made sure we had our hair pulled back and we had closed toe shoes on. We then placed the crucible on the ring stand in the fume hood. We heated it gently for a few minutes but then we heated it as hot as we could for 30 minutes with a blue flame. We then recorded the mass of the crucible and soil, which was 55.2. Our soil had 6.2 grams of organic matter. It is not necessary to measure the soil alone because the crucibles weight can not change. It is important to have organic materials in soil because it has a nutritional function. This serves nitrogen and phosphorous for plant growth. Organic matter also has a biological importance. This functions in that it profoundly affects the activites of microflora and organisms around it. Organic Matter also physically promotes good soil structure and will increase, buffer and exchange the capacity of soil.

The crucible with the dried out dirt in the busen burner. 

The weight of the soil and the crucible before it went through the busen burner

Soil Porosity Test

     In this experiment, we slowly poured 100mL of water from a 100mL graduated cylinder into a 250mL beaker filled to the 200mL mark with soil. Once water started to build up on top of the soil we stopped and measured that amount of water leftover from the 100mL graduated cylinder to determine the soil porosity.

First, we filled the 250mL beaker to the 200mL mark with our soil and the 100mL graduated cylinder to the 100mL mark with water.

Then, we slowly poured the water into the beaker.

Once the water started to make puddles on top of the soil, like shown in this picture, we stopped pouring the water.

Finally, we measured the leftover water and found there was 10.6mL of water leftover.

The soil porosity of our soil is 44.7%