Not if it is a fine rather than a fee
I think you will find that a fine can only be issued for a breach of the law - not by a landowner for use of his/her land. You cannot charge for trespass. Any charge you make is either a commercial arrangement (contract) or a claim for compensation for loss - such as damage to a crop - which has to be a real loss -you cannot add a penalty element.
Car parking companies are claiming that by parking on 'their' land you have agreed to a contract which may look like a fine etc - but in reality is no different from any other commercial contract.
Once you enter into a contract you may gain responsibilities unless you expressly make exclusions in advance.