Conclusion

Melissa
Throughout this lab, I learned that soil is not only a nuisance. Soil is the basic component of which all life originates. Food chains and ecosystems all start with a base of soil. The bottom and backbone of the food chain, plants, are only able to exist through soil. The different components of soil determine what kind of life can survive there. Soils with little nutrients, such as phosphorus or nitrogen depletion, do not have as high a productivity as soil with high levels of organic matter. Certain plants that can withstand high levels of salt exist in soils with high salinity. In this experience, I learned how to evaluate a soil's composition and use that information to remediate it to create a highly productive sample. If I were to plant a garden, I now know how to test for nutrient levels and which fertilizers (organic, inorganic) would create a desired effect. The lettuce plants grown in the controlled experiment are still young but we are continuing this experiment.


Hannah
This lab has taught me a lot about soil, and that there is a lot more to it than many people, including myself, may have thought. Soil is very different depending on where it's from and has many specific components that make it the way it is. It is the basis of life in any ecosystem. For example, things like soil erosion from invasive species can be very damaging. Also, even minor changes in soil such as the addition of salt, can also be very damaging and people should be aware that their actions have consequences to the soil and life around them. I learned how to evaluate many different aspects of soil such as its composition. I also learned that different kinds of soil hold water differently. Knowing what I do now, I feel as though I could successfully grow plants now that I am aware of what fertilizers and chemicals can do to them. I also learned from our remediation lab that natural soil may be just as good as fertilized soil for some plants. Some plants also require specific levels of pH and nutrients and it is important to retain those levels. Soil is vital to our environment and needs to be protected as much as any animal or plant species.

Controlled Experiment

To have a comparison to our remediated soil we created a controlled experiment. We put 67 grams of soil in the cup and planted 5 seeds. Every other day we watered the plants the same amount at the same time.

Day one of control and remediated soil

Control and remediated soil after a few days. They are growing very similarly.

Both cups after about a week. They still appear the same.


In conclusion, our remediation process was not particularly successful. However, it did not yield any negative results either. Compared to the control they look roughly the same and all 5 seeds grew in both cups. Although in the remediated cup, one plant appears to be dying but it is hard to tell whether that is a result of the soil or some other outside force. Every plant has two leaves and is about the same size and color. If you were to taste them, I assume they would taste the same since the fertilizer had little effect on the remediated soil.

Remediation Process

To remediate our soil we looked at our results from the fertility analysis. Because our soil seemed to have fairly high levels of necessary nutrients, we felt that we didn't need to add very much to fix it. This is likely because that although we could not see any microorganisms in the berlese funnel test, there were many other organisms such as worms that naturally fertilize the soil. This could also be due to the percent organic matter that we found to be about 27%, our soil was naturally a good source of nutrients. The pH was a little over 7 which is roughly the ideal level needed to grow lettuce, so we did not change it. We filed the cup with 67 grams of soil (same as control). Then, we measured 1.9 grams of inorganic soil in proportion with the amount of soil. Next, we added 9.7 grams of organic manure fertilizer. We planted 5 lettuce seeds and watered them both the same amount. We expected that these extra nutrients provided by the fertilizers would result in healthier lettuce plants that grow large and faster than the control soil.

Day one, notice the remediated soil looks finer and richer

Salinization Test

This test was not done on soil, however it showed students how salt levels can effect soil's productivity. Seven different bags were filled with 5 white beans wrapped in a paper towel. Solutions of regular table salt (NaCl) were created so that each solution had a different concentration. They were: 0g NaCl/100mL H2O, .5g NaCl/100mL H2O, 1g NaCl/100mL H2O, 2g NaCl/100mL H2O, 3g NaCl/100mL H2O, 4g NaCl/100mL H2O, and 5g NaCl/100mL H2O. Each bag was given 20mL of the salt solution of varying concentrations.

 

 The bags were sealed to prevent evaporation. After a week, the bags were examined to assess the beans' growth.

0g NaCl showed the most growth

.5g NaCl showed the second most growth

2g NaCl had few sprouting beans

3g NaCl had no growth

4g NaCl had no growth

Not visible, but 5g had no growth

1g NaCl had one sprouting bean

From this test, it can be concluded that high salinity levels halts soil production. To remediate salty soil, calcium ions must be added to balance the sodium ions. A good source of this is gypsum. It is not recommended to water down over salted soil because the salt particles may be carried into runoff and cause the same problem in fields elsewhere.

Potassium Test

Chart for Reference

In order to find the potassium levels of our soil sample, we added 2 grams of soil to a test tube of potassium extracting solution. We shook the mixture for one minute and then let it settle. Then, we extracted the liquid from the test tube and put it into a second test tube. In the second test tube we added one potassium indicating tablet. We mixed the solution until the tablet dissolved and was a purplish color. We continued to add 14 potassium test solution drops until the color changed to blue. Based on the chart provided, our soil sample's potassium level was medium. Although this seemed to result in healthy plants in the area, maybe higher levels would result in even healthier plants.

Finished Experiment

Phosphorus Test

To find the level of phosphorus in our soil, first we mixed the Phosphorus extracting solution with 1.5 grams of soil for one minute. Next, we allowed the soil to settle. After it was setttled, we took the liquid from the top and put it in another test tube with phosphorus indicator reagent. Next we added a phosphorus test tablet and shookthe solution until it dissolved. The solution turned a dark blue color, indicating that phosphorus levels are high. Beause phosphorus is often included in fertilizers, high phosphorus levels are ideal for plants. This is proven with our soil because the plants growing in it were numerous and healthy.

Chart showing phosphorus levels

Finished Solution

Nitrogen Test

In order to test the nitrogen level of our soil, we first filled the test tube to line 7 with nitrogen extracting solution and added 1 gram of soil to it. We mixed it in the test tube for one minute and then let the sample settle to the bottom. We then took a pipette and extracted the solution from the test tube into another test tube and added nitrogen indicator powder to it. We mixed it and after 5 minutes a light pink color started to develop. The Nitrogen color chart told us that our soil's nitrogen levels were on the low side (0-30 lb/acre). Although the plants growing in our soil looked healthy enough for the level to be considered fine, most plants probably would thrive better in soil with slightly higher amounts of nitrogen.

Completed Nitrogen Solution

Nitrogen color chart for comparison

pH Test

Completed pH indicator

To test the pH of our soil, we filled the test tube with the required amount of pH indicator and soil sample. We mixed the solution for one minute and let it sit for another 10 minutes. After that, we matched the color of the solution with the colors on the pH color chart. The chart told us that the pH of our soil was between a 7 or an 8. I think the pH level of the area we collected soil from was good for the plants living there because there was a lot of healthy looking foliage. This is likely because the soil is closer to being neutral than it is to being acidic. Most plants can grow in this level pH, for example, lettuce is best grown in soil with a level of 7.

Chart showing corresponding pH levels

Berlese Funnel Test

The purpose of this is to drive out organisms from the soil sample into the ethanol to be studied. The top of a liter soda bottle was cut off and plastic mesh was taped to the original opening. The remaining part of the bottle's body was filled with 25mL of ethanol. The top was placed upside down in the bottle and filled with soil.

The contraption was placed under a heat lamp for the long weekend.

After the 5 days, the ethanol from the bottom of the big bottle was poured into a Petri dish.

We used magnifying glasses to identify and organisms within the ethanol, but none were visible. Several other groups doing this same experiment were unable to find organisms either. This may be because microscopes were not available or the organisms stayed in the soil. Organisms in soil create the organic component in soil, where the majority of recycled nutrients are to create new life. The complex components of organisms are broken down to simple ones through decomposition and can be used by other plants as building blocks to grow. 

Soil Dry Percolation Rate Test

Soil

In our homemade funnel we made by cutting the the top off of a water bottle and adding filter paper, we filled it with a soil sample 1 cm from the top. We added 50 mL of water to the soil and after 60 seconds, 31 mL of water percolated over 10.21 cubic centimeters. Compared to the later results we found in the sand and clay, the water drained the fastest through the soil by far.

Sand

In the same funnel, we filled it with sand 1 cm from the top. We poured in 50 mL of water and at first it seemed to pool at the top, and did not soak through. After 120 seconds, a measurable amount of 26 mL percolated through the sand over the same surface area of 10.21 cm cubed. The sand took the second longest amount of time to have percolated a measurable amount of water, after soil.

Clay

Lastly, the clay took the longest to percolate through the same 10.21 cm cubed funnel. After 300 seconds only 17 mL of the 50 mL we put in percolated through the dry clay, giving it the slowest rate of all three substances. The fine powdery particles of the clay seemed to trap the water, having it pool on top for a few minutes. 

Soil Porosity Test

This test substituted water for air. To find the amount of air in the soil, we took a 400mL beaker and filled it with 200mL of packed soil and a graduated cylinder was filled with 100mL of water.

Water was continuously added until it began to pool at the surface of the soil sample.

We measured the remaining water in the graduated cylinder. Of the 100mL of water, only 17mL was not used in filling the empty air spaces in the soil sample.

This means that 83mL of the total 200mL of soil was composed of air. Again, water is substituted for soil in this procedure.

83mL water
200mL soil   =   41.5% air

This soil sample is 41.5% air

Percent Organic Matter Test

The dried soil sample from the soil moisture test was used in this test. The soil, 63.0g, was put in a crucible and above a Bunsen burner for 30 minutes. By doing this, the organic matter in the soil is converted to carbon dioxide and water. The difference in soil mass before and after Bunsen burner heating will determine the mass of organic matter.

 

When the crucible was taken off the burner and allowed to cool, the mass of the soil was recorded again (45.7g). By just measuring the mass of the sample after heating, only the remaining soil mass is determined. To find the organic matter is to find the loss of mass before and after heating. This was calculated as follows:

63.0g (before) - 45.7g (after) = 17.3g (organic)

17.3g (organic) / 63.0g (total) = 27.4% organic matter.

17.3g or 27.4% of the soil sample was organic matter.


Organic matter in soil is one of the most important factors of the substance. Organic matter is the main source of nutrients in soil, holds water within the soil to prevent leaching, and contributes to clumping, which prevents erosion.

Soil Moisture Test

The amount of water in the soil was measured in this test. A small boat of aluminum foil was created and several spoonfuls of soil were placed within. This sample, without the foil, was 71g.

This was placed in a drying oven overnight at a temperature of 90-95° F so the water was evaporated out of the sample. The dried mass was weighed again, this time at 63g. From these measurements, it was concluded that 63/71g was soil and 8/71g was water. This means that 88.7% was soil and 11.3% was water.

After discussing with other classmates, we learned that there not a correlation between soil moisture and texture. Clay produced a long ribbon of soil. Another group with soil with a high concentration of clay contained 37.9% water. This most likely came from the high water content.

Soil Texture Test

The texture of the soil was determined through two separate tests.

Qualitative Test
A small hand full of soil was rolled into a ball. Because the sample was drying out, additional water was added to help create the ball. The sample was squeezed between the thumb and forefinger to feel its texture. There was not a very gritty texture to it, yet it was not sticky. When rolled out, a short ribbon was made that soon broke. Based on this, we concluded that the soil was mainly silt or loam.

Rolling the soil into a bal

Squeezing ribbons of soil

Quantitative Test
65 mL of soil was put into a graduated cylinder. Water was added until the container was 100 mL full. We sealed off the opening of the cylinder with a cupped hand and shook it from side to side until the contents were a uniform mixture. This was placed upright and sat overnight. The next day the different layers of sediment were measured.

Water and soil mixture before shaken

Shaken mixture after one day

The next day, the different layers of soil were present. The very bottom of the cylinder was .5cm sand, the middle 10cm silt, and the top 1.5cm clay. The total soil content was 12cm. Percents of each layer were calculated.

These percents were used in a soil triangle to determine the type of soil our sample was. This sample is most likely silty loam.

From the qualitative test, our predictions of a silty or loam soil agrees with the results from the quantitative test. According to the percolation test, this soil type is consistent.

Compared to other soil samples in the class, one sample contained mostly clay and was classified as clay on the soil triangle. Another group found soil at the same site as we did and had soil similar to ours, except with a higher concentration of silt and was classified as silt. One group who got their soil from the school's yard contained much more clay than any other group. This is most likely because different soil horizons and different factors affected how these soils were developed. Although these samples were derived relatively close together, the samples may have had different parent materials.

Collecting Soil

We collected our soil from the side of the path in the woods at Cuba Marsh. We chose that location because it is a forest preserve and would likely be unaffected by inorganic substances and fertilizers.

The ground was relatively damp and easy to dig into. We found a few rocks in the soil and it seemed to clump together, meaning that maybe there was some clay in it. A nearby gravel path may have contributed to the rockiness of the soil. The area was rich in plant life with many diverse species of plants surrounding it. We also found grass, leaves and sticks within the soil. There were also many worms living within it. The soil was a dark brown color, possibly meaning that it is rich in nutrients.