Where an agreement in writing secures to the tenant to of an agricultural holding for an improvement for which compensation is payable by virtue of either of the two last foregoing sections fair and reasonable compensation, having regard to the circumstances existing at the time of making the agreement, the compensation so secured shall, as respects that improvement, be substituted for compensation under this Act.

The landlord and the tenant of an agricultural holding who have agreed that the holding shall be let or treated as a market garden may by agreement in writing substitute, for the provisions as to compensation which would otherwise be applicable to the holding, the provisions as to compensation set out in subsections (2) and (3) of the last foregoing section.