Yes. Just use scissors, or a knife or razor blade. It will not fray the edges or compromise the integrity.
If cutting the silage tarp lengthwise, it's most simple to roll out the tarp to said length and cut across while the tarp still has the factory fold. This way you are cutting a shorter distance over many layers.
When cutting the silage tarp widthwise, you will need to roll out and unfold the entire tarp. Then make a fold at said length and cut on the fold.
This project will definitely be easier on a day without wind.