Yes, you can - as long as there are no defects created against any plots within that scheme. You also need to have the ability to delete schemes turned on in your User Profile (an admin can change this under Admin > Your Users)
Within the scheme simply click on Edit on the top left of your scheme view.
Then select the Delete Scheme option on the top right. 
If there are defects against the scheme, and the scheme can't be deleted, the message below will show.
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