Lab 4 Part 1 - Community Garden

For this last lab the class visited a community garden located behind Centenary United Methodist Church. We used a variety of things to analyze the soil including a split-spoon corer, sieves, and a soil composition chart with an associated dichotomous key. We also discussed various issues that arise with urban gardens, mainly relating to soil contamination from elements like lead. The split-spoon corer was used to obtain vertical samples of the soil to see the arrangement of the different layers. The dichotomous key for the general soil categories was used to analyze the topsoil layer, and then the soil composition chart was used to determine what percentage of the soil was clay, how much was sand, and how much was silt. A shovel-full of the soil, containing multiple layers, was also put into the sieves. Each sieve had a different grade mesh, and the sieves were stacked on top of each other in order with coarsest one on top and the finest on the bottom. The soil was poured into the top sieve and the stack was sealed and then shaken. When we opened the lid on the top sieve, it was discovered that the larger particles had stayed on top and smaller ones had continued to fall through the sieves until they could go no further. With the exception of some particles that stuck together because of moisture, this allowed us to separate the materials in the soil by size. A photo of sieves stacked up is shown below.