The problem being is which will hold more dirt the side with grass or the side with just plane dirt. Abstract Nature at times damages the Earth by erosion.
Erosion is the gradually wearing away of soil by water.
The focus of this experiment is soil erosion. The hypothesis is that the soil with grass roots will have less dirt fall out. Then soil with out will have less dirt. The steps to the project are first it is built. Then to proceed with the experiment you would need to plant grass bed on one side.