Nitrogen and Phosphorus Levels in the Soil at Lakeshore Park
We tested soil samples at Lakeshore Park at intervals of 1 m from the rocks along the shoreline to determine whether there was a correlation between distance from the rocks and the amount of nutrients in the soil. We collected a total of 100 soil samples from 10 different locations (10 samples per location) along Lake Michigan. Based on the r2 values (Figure 2: 2.636 x 10 ^-1, 9.5 x 10^-3, and 9.4 x 10^-3) and the nitrogen graph (Figure 1: 2.7 x 10^-3) we determined that there was no correlation between distance from the lake and nitrogen and phosphorus levels.
Key Words: Soil, Nutrients, Nitrogen, Phosphorus, Lakeshore State Park
Built in 1991, the island that houses Lakeshore State Park was originally created to protect the shoreline along the Summerfest grounds (Friends of Lakeshore Park, 2012). The base of the island is primarily made of dolomite limestone and other crushed rocks (Friends of Lakeshore Park, 2012). In addition to trails and bike paths, there are small prairies and unfertilized manicured lawns that rest on topsoil placed there by the builders of the island. The location and use of this land determines soil nutrients.
In China researchers found that the land use and the slope of the land can have an effect on the amount of nutrients found in the soil (Wang et.al, 2001). They determined that land use such as grassland versus farmland, has a greater effect on nutrient levels in the soil than does location (Wang et.al, 2001). In another study conducted by Houlahan and Findlay (2004), they found that the farther away the soil is from the wetlands the fewer nutrients there are, suggesting a negative correlation. Although there are no drastic slopes or wetlands in our research area, these experiments show that there are connections between the type of land, its distance from water and soil nutrients.
Determining whether or not there is a correlation between distance from the rocks alone the shoreline and the amount of nitrogen and phosphorus in the soil was the purpose of this experiment. We hypothesized that the amount nitrogen and phosphorus in the soil at Lakeshore State Park would increase as we moved further away from the lake. Our hypothesis would be supported if the data shows that there is positive correlation between distance and the amount of nutrients in the soil. It would be unsupported if the data shows that there is a negative correlation between distance from the lake and soil nutrients or if there is no correlation at all.
Materials and Method
We collected the soil samples from the Lakeshore State Park prairielands on October 12, 2012 between 1200 and 1500 hours. The compass bearing for the location was 255˚ W from the shoreline. We used a plastic shovel to dig up the soil. We labeled 10 ziplock bags 1-10 and used them to hold the soil samples from each of the 10 locations. Other materials include a watch, a sunto compass (model # A-1000), 1 LUFKIN 100 ft measuring tape, and a LAMOTTE combination soil kit (model # STH 14).
In order to collect random samples one group member collected 10 different numbers between 1and 200 from a random number generator. The second group member then counted the large rocks along the edge of the shoreline. Whenever one of the ten numbers was called we measured out 10 m from that rock away from the lake and collected soil samples 1 m apart until we reached 10 m from the rocks. We placed each soil sample in its respective sandwich bag and all ten soil samples from that location in its appropriately marked Ziploc bag. We tested the soil samples for nitrogen and phosphorus using the combination soil kit. We followed the directions located in the kit to determine the nutrient levels in the soil. For the statistical test we used Microsoft Excel (2010) to graph the meters from the rocks (independent variable) against kilograms per hectare (dependent variable) in order to determine whether or not there was a correlation.
There is no correlation between the distance from the lake and the amount of nitrogen and phosphorus found in the soil. The R2 value for the nitrogen Levels graph is 2.7 x 10^-3. The R2 values for the phosphorus levels graph are 2.636 x 10^-3, 9.4 x 10^-3, and 9.5 x 10^-3. There are three R2 values because each value represents one of the three stations. The R2 values for both graphs are closer to 0 than they are to 1.
Figure 1: Levels of nitrogen found in the soil at Lakeshore State Park
Figure 2: Levels of phosphorus in the soil at Lakeshore State Park
In the process of conducting this experiment, we came across some difficulties in finding a location. We originally hypothesized that all nutrients will be higher in wooded areas compared to the lake and we found that there were too many variables. We later decided that we wanted to test nitrogen and phosphorus found in the soil by the lake.
There was no correlation between the distance from the lake and the amount of nutrients in the soil. The R2 value for the nitrogen graph (2.7 x 10^-3) and the R2 values from the phosphorus graph (2.636 x 10^-3, 9.4 x 10^-3, and 9.5 x 10^-3) are all closer to 0 than they are to 1 suggesting that there is no correlation between our two variables. These findings do not support our hypothesis which stated that there would be a positive correlation between the distance from the lake and the amount of nitrogen and phosphorus in the soil.
After testing the phosphorus levels in the soil we observed that there were large amounts of the nutrient in most of the soil samples. This can be a result of the fact that the soil used to cover the rocky core of the island is top soil. Plants use some nutrients more readily than others. Phosphorus is actively used in the plant cycle and is therefore found in greater concentrations in the first 20 cm of the top soil (Jobbagy and Jackson, 2001). Since there are several different plants growing in the prairielands of Lakeshore State Park it is possible that these plants contributed to the phosphorus levels in the soil by keeping it in circulation.
There are many possible sources of error in this experiment. The experiment was completed over several weeks. The soil samples were collected on October 12, 2012, however, we did not test them until October 22, 2012. The ten day difference between the time of collection and the time of test could have had a negative effect on the soil samples which sat in their bags in a car during that entire time. The age of the chemicals we used for nutrient testing could have also been a problem. The combination soil kit contained many different reagents that separated, were discolored, or corroded the opening of the container. Outdated chemicals do not always work properly. This could have altered the color of our final products and thus our final data. Yet another source of error is the condition of the equipment. Although we cleaned the test tubes to the best of our ability, there were still particles on/in the containers that we could not remove effectively. These particles could have contained remnants of other nutrients or contaminates that could have altered the results of the tests.
If we did this experiment again we could improve it in different ways. We could use better soaps and warmer water to clean the test tubes. We could also order new reagents to ensure that they will work as they should. Lastly, we could put more space between samples. Working within a 10 m distance does not allow much space for variation to occur. Testing the samples over a larger distance could yield more consistent results next time.
Lakeshore Park. 2012. Friends of Lakeshore Park history. Retrieved November 5th, 2012, from http://www.friendslsp.org/about-us/history/
Wang, J., Fu, B., Qiu,Y., Chen, L. 2001. Soil Nutrients in Relation to land use and landscape position in the semi-arid small catchment on the Loess Plateau in China. Journal of Arid Environments. 48: 537-550. Retrieved: November 6th, 2012 from Science Direct database
Houlahan, J., Findlay, C. 2004. Estimating the ‘critical distance at which adjacent land-use degrades wetland water and sediment quality. Journal of Landscape Ecology. 19: 677-690.
Jobbagy, E., Jackson, R. 2001. The distribution of soil nutrients with depth: Global patterns and the imprints of plants. Journal of Biogeochemistry. 53: 51-77