Conclusion

            In the past weeks of our soil lab and blog, I have learned about the extensiveness of soil and its importance. Throughout the lab we discussed the importance of s healthy and fertile soil in many things like the agriculture industry. Soil is influenced by five factors its parent material, climate, time, biota, and topography. All of these factors influence how fertile the soil is. I not only learned that there are many different types of soil, due to the many variations of each factor, but I also learned that some soil types are far better do growing plants than others. For instance, a soil that is loam, or a proper mixture of silt, clay, and sand, will filter water and hold nutrients for a plant better than a sand heaven soil because the sand heaven soil will experience more salinization. I also learned thy soils that are to as fertile can have components added to them to make them more fertile. If a soil does not have enough nutrients a person can add a fertilizer to help the soil support plants life, but the type of fertilizer is significant depending on your soil. I learned many traits of the ideal soil for plant growing, but different plants need their soil to have different traits. For the most part ideal soils are loam and have a neutral pH, they also are rich in nutrients like nitrogen and phosphorus. Most of all throughout the lab I learned that all soils are different and that they are important to society.

Merrick Howarth

Conclusion

Maddie Currie

       During the making of this blog, the most important thing I learned about soil is that it is very important to the survival of humans and everything else on the planet. It is a home for countless microorganisms and insects. It is what we use to grow our food and without it, humans probably wouldn't survive.
       Soil is not all created equal, either. Some is more fertile than the rest. The soil we tested in these experiments was not very fertile because it had low levels of nutrients. I learned why farmers use fertilizers--to replace those nutrients and make the soil more fertile. This allows them to grow more food more quickly in order to feed our growing population. Before this project, I had no idea how much organic matter soil contained. It surprised me to see that during these tests.
       Soil and dirt are not the same thing. Dirt can be anything from dust to soil, but soil is special. It is made up of sand, silt, clay, and organic matter and soils from different places around the world have different characteristics like texture, porosity, composition, and nutrient content.
       Soil is the living skin of our planet and one of the most important things humans need to survive.

Controlled Experiment: Lettuce Seed Growth

Once our soil was remediated, which you can see in our Soil Remediation post, we added 6 lettuce seeds to each cup and placed them in direct sunlight. 

We watered them on an as needed basis, and the chart below shows how much we gave them each day.

The chart below shows the growth of the lettuce seed over a 10 day period.

       Our control seeds grew much more than our remediated seeds. This may be because we over fertilized the remediated crop or because we buried the seeds to far when planting the remediated crop because the soil was wet and difficult to work with.

       The control crop sprouted 6 stems of lettuce with 2 leaves on them each. The remediated crop sprouted one very small stem, as shown below.

We didn't taste the lettuce ourselves, but a member of another group did and reported that isn't tasted like grass, which may be due to the fact that the lettuce plants are still so small.

Fertility Analysis

To further understand the the composition of our soil, we looked at the pH and the levels of phosphorus, nitrogen, and potassium present in our soil.

For the pH test, we mixed pH indicator solution and soil together then let it settle for 10 minutes.  

The results of the pH test and the color chart. The top part of the liquid with a bluish-greenish color is what is being compared to the chart.

The pH of our soil was about 6.5, which is just slightly acidic. The ideal pH for grass, which is what mainly grows where this soil was taken from, is between 6.5 and 7. The grass growing in this soil looks healthy, as you can see in our Collecting the Soil post, which makes sense because the pH is right on target.

For the phosphorus test, we mixed soil with Phosphorus Extracting Solution and let it settle. We then used a pipettes to take the clear liquid from the top of the test tube and mixed it with Phosphorus Indicator Reagent. Then one Phosphorus Test Tablet was added and mixed in until it had completely dissolved. The result was compared to the color chart to find that our soil's phosphorus content is lower than the ideal range.

The phosphorus results and color chart.

For the nitrogen test, we mixed soil with Nitrogen Extracting Solution and let it settle. We then used a pipettes to extract the clear liquid from the top and mixed that with Nitrogen Indicator Powder. It was then left to settle and develop for 5 minutes. We found that our soil's nitrogen content was low.

The results of the nitrogen test and the color chart.

For the potassium test, we mixed soil with Potassium Extracting Solution and let it settle. We then extracted the clear liquid from the top with a pipette. We had to repeat the first step in order to get enough clear liquid for the test. We added a Potassium Indicator Tablet to the clear solution and mixed until it had completely dissolved to get the initial purplish color.

 

The initial color of the potassium test.

We then added Potassium Test Solution to the test tube two drops at a time and mixing in between until we saw the color change from purple to blue, as shown below.

It took 18 drops to get the color to completely change from purple to blue. This means that our soil has a low potassium content.

Soil Moisture

For this test, we used a piece of aluminum foil, about a square foot in size, to make a small tray by rolling and flattening the sides and folding over the corners. We then weighed this tray and found that it was 2.9 grams. We added several spoonfuls of soil to the tray and weighed it again, finding it to be 86.9 grams. This means that the weight of the soil alone was 84.0 grams initially.

The soil was then placed into a drying oven overnight at 90-95 degrees and retrieved in the morning. The pictures below show the difference in the appearance of the soil. 

Before drying oven:

After drying oven:

The weight of the tray of soil after coming out of the drying oven was 85.2 grams. This means that there was 1.7 grams of water in the soil.

Calculations:

The percent of water by mass for the soil was 2.0% as calculated below.

       This is a relatively low percentage of water content in the soil compared to other groups in the class, who had as much as 12% to 13% water. 

       These values accurately represent our soil because of its composition, which was 40% sand, 50% silt, and 10% clay. The other groups that had higher water percentages had much more clay in their soil and much less sand. Sand doesn't hold water very well and allows it to go right through it, and clay holds water very well.

Berlese Funnel

         In our Berlese Funnel lab we were performing a test to find macro-invertebrates in our soil. To preform this lab we cut the top off of a two liter bottle and placed a filter on the outside of the mouth of the bottle which was then securely taped on. Some ethanol was placed in the bottom portion of the bottle and then the top portion of the bottle was filled with soil, placed on the bottom part, and finally placed under a heating lamp. 

This is our set up Berlese funnel. It has been placed ten centimeters under a heating lamp where it will stay for five days, being under the heat lamp will cause the soil to become dry and macro-invertebrates to fall out of the soil through the filter, and into the ethanol.

       We found that our soil became very dry under the heating lab and that our Berlese funnel produced few organisms. Although we could see some details of the organisms we found they could not be confidently identified. Based off of other information and result of other students, we can assume it is some type of soil mite. Other lab groups that had organisms also found that they had soil mites. We did not have many organisms, but others had no organisms at all, while other lab groups found many organisms. Macro-invertebrates are important to our soil because they make soil more porous and they also assist in the flow of organic matter in an environment.

This is a picture of our petri dish with the ethanol we removed from our Berlese funnel. The small white specks are mites.

Percent Organic Matter

       After we removed the soil from the drying oven we used it to preform our percent organic matter test. The soil had 20.8 grams of organic matter, which is 46.1%. We found this by weighing the recently dried soil and then placing it on a Bunsen burner for thirty minutes. After the thirty minutes we allowed the soil in the crucible to cool and then weighed it again. We then compared the weights to solve for the amount and percent of organic matter. Since we weighed the soil both before the Bunsen burner and after the Bunsen burner in the crucible, we did not need to weigh the soil alone.

This is our crucible filled with soil before it was placed on a Bunsen burner, it had a weight of 45.1 grams.

This was our crucible filled with soil on a Bunsen burner, where is was heated at a high temperature for thirty minutes.

This is our crucible filled with soil after it has been removed from the Bunsen burner, cooled, and placed on the scale, after the heating it weighed 24.3 grams.

 

These were our calculations for total organic material and for the percent organic material.

 

       Organic material is extremely important in soil for many reasons. Some of these reasons are that it helps nourish the soil, it increases a soils ability to hold water, and it gives the soil better structure. It helps nourish the soil by adding many nutrients like nitrogen and phosphorus. Organic mater also assists in soils ability to hold water because it is usually a very absorbent substance. It also helps with soil structure by causing soil to clump more, which is very important in creating space in soil for substances like water and gasses.