Soil Analysis: Defining Soil and Its Importance in the Environment Liberty Middle School

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Mr. Johnston - teacher Mrs. Carter - student teacher Primary Authors - Stephanie, Kushal, Tim Contributors - Mr. Johnston's 2nd block students Introduction Soil plays an important role in our ecological environment. It provides plants nutrients for growth, earth for cultivation, and it supports the plants that recycle oxygen for our use. In our experiment, we explored the soil at a specific location on our Liberty Middle School campus using two different methods. We were to identify the major characteristics of our soil such as location, soil color, horizons, consistency [consistence], structure, texture, bulk density, pH level, and fertility of through a series of experiments. Many experiments will help us form specific and consistent conclusions about our surroundings. This data will then be posted on the GLOBE web site to share this information internationally. Materials and Methods: Determining Location- We had to use a Global Positioning Satellites [Global Positioning System] (GPS) to determine our exact location using latitude and longitude, elevation, and universal time. We had to first acquire four satellites before anything else could be done. After acquiring the minimum four satellites, we had to get 5 different reading for each minute for five minutes to obtain the average of the location were our auger and pit were located. Breaking Ground- To start our experiment, we had an employee from Madison Excavation Landscape Company come to Liberty with a backhoe to dig a pit. After school on February 1, I helped to clean out the pit dug by the backhoe. On February 2, we had to auger to a depth of 100cm (1m.) After the dirt was augered out each time, we had to place it on a tarp and compact it to equal the depth that we reached after each turn of the auger. Finding Horizons- We had to locate the horizons by looking at the obvious differences of the soil. After we had found each horizon, we then hammered a nail into the spot in which we thought the each horizon started and stopped. We also had to measure the depth of each horizon using the metric system. To do this, we took a meter stick and measured from one horizon to the next horizon. Determining Consistence- To find the consistence of the soil, we had to find a ped and crush it between two fingers. The choices of consistence were: friable, firm, extra firm, and hammer [Choices for Consistence are: Loose, Friable, Firm, Extremely Firm. See Consistence Step-By-Step Guide.]. Determining Color- To determine the color of the soil, we first had to take a ped and wet it. After that, we then broke the ped apart and looked at the color of the soil and tried to match it to that in the Munsell horizon color book. There are only 2 colors per horizon allowed [It is possible to have more than two colors per horizon; however, the data sheet only has room for a primary color and a secondary color. If you find more than two colors in a horizon, note the color that is most prevalent and second most prevalent and note the third color's notation under Comments. See Soil Color Step-By-Step Guide]. The only time you would report two colors in a horizon is when there is a main color with a tint of another color. The person that did this must have clean hands and must be looking at the soil clumps in the sun along with the Munsell horizon color book. Determining Texture- When we had to find a ped and wet it. After wetting the ped, we then felt the ped to determine the texture. Determining Structure- To find the structure, we had to take a ped and then break it apart. The choices we had to determine the structure were: granular, blocky, and platey. [Soil Structure choices are: Granular, Blocky, Platy, Prismatic, Columnar, Single-grained, Massive. See Soil Structure Step-By-Step Guide.] Determining Soil pH- We had to measure out 25g of filtered [sieved] soil and 25g of distilled water in different graduated cylinders. Then you take the initial pH of the water using the pH paper and the colorimetric chart. Then you record this information. Then you must pour the soil into the distilled water. Stir the mixture for 30 seconds timing with a watch. Let the mixture sit undisturbed for three minutes. Repeat steps five and six five more times. After the last time, the supernatant, water on top of graduated cylinder, and the precipitate, the collection of soil on the bottom. Take some pH paper and dip the end of the pH paper into the supernatant. Do not let it touch any of the precipitate. Repeat the process three times per horizon for accuracy. Determining Fertility- First step: Pour 30mL of distilled water into the test tube. Add two Floc Ex tablets. Put the cap back on and shake until the tablets are disintegrated. Add a heaping teaspoon of soil from the horizon you chose. Shake for a minute. Let the test tube stand until the water and other particles settle out. Nitrogen test: Move the clear solution from the large test tube with the soil as the precipitate with a pipette to one of the three smaller test tubes. Fill it to the brim [shoulder]. Add the Nitrate WR CTA tablet to the test tube. Replace the cap and shake until disintegrated. Wait five minutes for the color to change then compare the results to the colorimetric chart. Phosphorus test: Transfer 25 drops of the supernatant from the large tube to another small test tube. Fill the test tube with distilled water. Add a Phosphorus tablet. Place the cap on the top and shake until dissolved. Wait five minutes for the color to change. Compare the results to the colorimetric chart. Potassium test: Transfer 25 drops [The entire test tube should be filled to the shoulder with precipitate. The only test that requires 25 drops is the Phosphorus test. See Soil Fertility Step-By-Step Guide] of the supernatant from the large tube to another small test tube. Fill the test tube with distilled water. Add a Potassium tablet. Place the cap on the top and shake until dissolved. Wait five minutes for the color to change. Compare the results to the colorimetric chart. Results: GPS for Pit and Auger: 34º 43.957' N 86º 46.733' W Elevation: 779 ft. 15.38 UT- Time we began our Experimentation Horizons and their Consistence The Pit In the pit, there were six horizons. The first horizon was 0-14cm. The second one was 14-35cm. The third one was 35-48cm. The fourth was 48-55.5cm. The fifth one was 55.5-63.5cm. And, the sixth one was 63.5cm-70.5cm. The rest data is in the chart below: Moisture Structure Color Consistency [e] Texture Presence [rocks/roots] pH [outside] pH [inside] Moist Granular 5YR 4/6 Friable Sandy loam Few rocks/ many roots Outside- 7.5, 7.5, 7 Inside- 6, 6.5, 6.5 Moist Blocky 10YR 4/4 Firm Clay loam Few rocks/ few roots 8.5, 8, 7.5 Moist Blocky 5YR 4/6 Ex. Firm Sandy clay loam Many rocks/ 0 roots 7.5, 7.5, 7.5 Moist Blocky 10R 4/6 Ex. Firm Clay Few rocks/ 0 roots 8, 8, 8 Dry Platy 7.5yR 6/4 Ex. Firm Clay loam Many rocks/ 0 roots Dry Platy 7.5YR 7/4 Ex. Firm Sandy clay Many rocks/ 0 roots. The fertility level for horizon 1 is Nitrogen- Low Phosphorus- Low Potassium- Medium The fertility level for horizon 3 is Nitrogen- Low Phosphorus- Medium Potassium- not enough samples. No results for bulk density.   The Auger This auger was named Freddie. In this auger method, we could not dig up to a meter. We only reached about half-or 50 cm. We found two horizons in the auger. The details are discussed in the chart below: Moisture Structure Color Consistence Texture Presence [rocks/roots] Moist Granular 7.5YR 4/3 2.5Y 5/4 Friable Sandy clay loam Few rocks/ many roots Moist Blocky 2.5YR 4/8 Firm Clay Many rocks/ no roots Discussion: Pit Results: Other Factors Affecting the Results Time and Mistakes: One of the factors affecting the experiment and tests overall was time. Because we were limited to a certain amount of time, approximately 1 hour and a half, we could not complete all the tests required. Free Carbonates: For example, we did not test for free carbonates in the pit. That is why our result chart shows the absence of free carbonates in the soil. [If you have not completed a test such as carbonates, this does not indicate an absence of free carbonates in the soil. It only indicates that you did not complete the test. Please remember not to put "None" as the carbonate reaction in the data entry pages if you did not complete this test. Leave the answer as unknown and if you ever do complete the carbonate test, you can then re-enter the soil horizon description data. See Free Carbonates Step-By Step Guide.] Bulk Density: In bulk density, we did not have time and forgot to weigh the wet weight of the soil after it was taken. After finding the dry weight, it is impossible to go back and obtain wet weight. This is why we have no result for bulk density. pH level: For pH levels, we did not have time to test more than one horizon completely outside on the site. [Remember, the protocol requires that the soil samples from each horizon be dried and sieved. So, if you took some samples out in the field and let them air-dry for a few days or dried them in a soil soil drying oven, then you would have to sieve your sample, per horizon. At that point, you could complete the pH protocol. See Soil pH Step-By-Step Guide.] The pH tests take at least 30 minutes to accomplish for one horizon, and we did not have enough time. We also forgot to measure the initial pH level of the water before adding soil mixtures for horizons 3 and 4. These were experiments carried out with the dry soil. One mistake we made in the pH level had to do with wrong materials. In the procedure, we had to use distilled water and measure its initial pH. In the 1st horizon pH measurement that was done with the dry soil, we used non-distilled water. This could have an effect on the final pH because the tap water might have had a different pH than that of the distilled water [Excellent observation and it's more than likely true.]. Thus, we will keep the results on the chart for the inside experiment of horizon 1, pH level, but we will note that it is also inconclusive. As for the results of the pH levels, assuming distilled water that had the initial pH the same as that of the water we used for the horizon 1 outside test, we can conclude that the soil is neutral to slightly basic pH levels. 7 is a neutral reading, and we had gotten 7 and above, toward the basic side of the scale. These are the results excluding the inconclusive one with the mistakes. Depth of the Pit: We could not dig the whole to the standard I meter depth because the backhoe and shovels became inadequate appliances after 70.5 cm. The ground became extremely dense and hard to work with, so we could not dig any further. One assumption could be that we hit subsoil. Subsoil is made of tightly packed materials such as rock and inorganic soil materials. This assumption matches our results as well; the 6th horizon in the pit had a presence of many rocks and no roots. Another supporting factor is that most plants' roots do not penetrate past a certain depth. The lower soil horizons are clay particles mostly; clay particles are the most tightly packed particles of soil. Therefore, roots would not be found deeper within the clay soil because of the lack of nutrients and water availability. Consistence, Texture, Structure, and moisture: These four factors coincide with one another accordingly. The surface of the soil is called the humus layer. This is the organic materials layer, usually followed by the topsoil layer, which is made of clay, humus, sand, and minerals. This description fits our results almost exactly. For the top layer, we have a friable consistence and granular structure, meaning it is crumbly, sandy loam texture, loam being the organic materials, and moisture was moist, probably because of the sand retaining water [actually, probably it is the clay particles and the organic material in the soil that were retaining the water]. The humus layer is where most plants grow. Because the roots penetrate here, they need growing space, not compact particles like clay, and moisture [most plants need at least some moisture in the soil in order to grow]. Those descriptions fit our results; the friable particles [Particles are individual particles of soil, and peds are units of Soil Structure. When testing for Consistence you would be using a ped of soil. If all that are available are individual particles of soil {sand, for instance} and no peds at all, then you have a Loose Consistence.] are not hard and they are crumbly so many pockets are available for root growth and storage areas for water and nutrient that the plant needs. The deeper we go, the harder and harder the consistence becomes, going from firm in the 2nd horizon to extra firm from the 3rd horizon to the 6th. The texture goes from loam containing to just sandy clay. This shows that not as much moisture reaches down to that depth. Clay, being the most tightly packed particle, does not allow very much water at all to penetrate. This accounts for the first four horizon's moisture and the last two horizon's dryness. The structure in the second, third, and fourth horizon is blocky. It acts as a transitional soil from granular to the platy structure that lies beneath in the 5th and 6th horizons. One could assume the platy structure is a result of the time and build-up it has to support, therefore it is horizontal and tightly packed. Fertility: Fertility was a simple test of the presence of nitrogen, phosphorus, and potassium in the soil. Our results show that in horizon one, low nitrogen content, low phosphorus content, and medium potassium content. In the 3rd horizon, we have low nitrogen content and medium phosphorus content. We could not test for potassium because we ran out of testing sample. The third horizon is clay-like, and we did not have enough time to have it settle. The particles were too tightly packed, thus, our potassium measurement for the third horizon is inconclusive. One might suggest the need for fertilizer in our soil. Nitrogen, phosphorus, and potassium are essential nutrients required by plants for a healthy life. If we are lacking in them, we need to add something to the soil to maintain our plant life. Auger results: Depth of Auger: The auger that we named "Freddy" was the successful auger of the two. It attained soil from a hole and gave us enough dirt to work with. One reason it didn't get to the standard one-meter measurement was because it hit rock at 50 cm. Once again, because the pit was right next to the auger, there is a correspondence between the soil consistence. The deeper you go, the harder and rockier the horizons will be. The same theory about the roots and clay that applied to the pit applies to the auger method as well, since the locations were less than ten meters apart. Consistence, Texture, Structure, and moisture: The auger came up with similar results as the pit. For the only two horizons that we discovered, they were both moist and the textures were about the same, the first was sandy clay loam and the second clay. The first horizon structure was granular, typical surface soil structure, and the second was blocky. As for the consistence, the first was friable, suitable for plant life, and the second was firm. These results have the same explanations behind them: the first horizon is granular, friable, moist, and has suggestions of humus and topsoil-like qualities, suitable for plant-life. The second horizon is firmer, blocky, moist, and clay-like, harder and less suitable for cultivation. Other: There weren't as many tests for the auger as there were for the pit because an auger gives you less soil to work with, and more often than not, does not have the right conditions for many of the experiments. For example, we have no results for bulk density because an auger already churns the soil and it cannot be measured that way. We did not get a chance to test fertility or pH level; there weren't enough soil samples. We did test for free carbonates and found that there were no traces of them. Both results: Colors of Pit and Auger Horizons: Both the auger and the pit horizons had the same tints: Yellow Red, with the exception of horizon 4 on the pit, which was solid red. Alabama is known for its red clay, so this is not unusual. It merely suggests that we might have hit a completely clay horizon. This is supported by the texture, which is clay and only clay. The auger, however, did not get as deep as the pit, and yet its only two horizon colors match up better with the 5th and 6th horizon colors of the pit. This might suggest that the soil might have been churned up a bit in the area before the school was built [excellent point]. It could be a possibility that a construction company had to test soil in the area before it was built and it was mixed with a machine. Also, Liberty was built on a former swampland. In removing water and replacing it with other soils, the horizons could be very different in any two places, even right beside the other. I think one of the most important lessons we learned was to never dig a hole when it is freezing outside! ***Notes in brackets [ ] are comments from the GLOBE Soils team.*** Back to Liberty Middle School Reports

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