I wanted to share a photo of a bullpen from a field I visited last week.
This bullpen at the University of Indianapolis utilizes 4x4 lumber to edge the bullpen. Consider using this on bullpens for both baseball and softball. It provides a good edge to work off of to keep grass out of bullpen areas. Also, when the time comes to add material to the area, a board can be used to pull along the lumber to ensure a smooth area in a similar fashion as adding materials to baselines as shown below:
Go to j-dturf.com to learn more about J&D Turf.