But such fence shall not be removed if it was made of material taken from the land on which it is built, until the party pays or tenders to the owner of the land the value of such material, to be ascertained by the fence viewers; nor shall a fence be removed at a time when the removal will throw open or expose the crops of either party, but it may be removed within a reasonable time after the crops are secured, although the six months above specified have passed.