Use the Natural Resources Conservation Service web site (Web soil survey http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm) to gather soils data from five (5) different locations across Louisiana. Make sure you sample from across the state.
For each of the sampled associations, record in an Excel spreadsheet the following data (each should be in column, each column should be labeled):
o o o o o
Name of the soil or soil association
Average elevation where soil is found
Average slope where the soil is found
Depth to water table (if it says “more than 80 inches” use 120) Typical soil profile depth (do not include bedrock in the depth)
Hand in your spreadsheet with your observations.
Use your data to make scatter plots of the relationships listed below. Do not
connect your points with a line. Include a best-fit linear regression in all of your plots. Make sure that you also include on the graph the R2 value for the best-fit line. Remember to label your axes (include units). Hand in each of your plots. (14 points)
o Depth to water table (y-axis) vs. average elevation (x-axis) o Depth to water table (y-axis) vs. average slope (x-axis)
o Depth to water table (y-axis) vs. soil profile depth (x-axis) o Soil profile depth (y-axis) vs. average slope (x-axis)
Type your answers to the following questions. Use complete sentences (but you can probably answer all of these in a paragraph or two).
You can answer these in a paragraph or even a few sentences.
1. Which two relationships have the highest R2 values? Do these relationship make physical sense to you? Explain why you think there is a correlation between these variables. (2 points)
2. Which two relationships have the lowest R2 values? Explain why you think there is less
of a correlation between these variables. (2 points)
3. The depth to the water table is important for growing crops. If you were planning to start a farm, what other soil variables would you like to know about that are not included in the spreadsheet you compiled above? Why? (2 points)