A lien created under section 52-901 shall not attach to any portion of such crops, in the hands of an innocent purchaser or dealer in the usual course of trade, unless all the notices provided for shall have been given. In the event the fuel or lubricant was furnished to a person on rented or leased land, the lien shall not apply to the landlord's or lessor's share of the crops produced. The lien shall not be assignable.