How can I remove a lot of items through commands when they give me immense lag when I near them?

There is a /fill command, and you can fill in all of the dirt with air. Here is a tutorial I found on it:

If you are referring to dirt block entities, (like when you drop dirt), a very easy way is to just wait for 5 minutes. All of the dirt will despawn after 5 minutes.

You would use something like this: /kill @e[type=item, distance=..15] This will kill all items within 15 blocks of you thus removing lag.