6SAn undertaking by the tenant, in the event of the destruction by fire of harvested crops grown on the holding for consumption thereon, to return to the holding the full equivalent manurial value of the crops destroyed, in so far as the return thereof is required for the fulfilment of his responsibilities to farm in accordance with the rules of good husbandry, and (except where the interest of the tenant is held for the purposes of a government department or where the tenant has made provision approved by the Secretary of State in lieu of such insurance) an undertaking by the tenant to insure to their full value all dead stock on the holding and all such harvested crops against damage by fire.