(1) In any proceedings for abatement of fixed money rent on the ground that the area of the holding has decreased by diluvion or by the taking up of land for a public purpose or for a work of public utility, or under the provisions of section 37, or for enhancement on the ground that the area of the holding has increased by alluvion, the court shall abate or enhance the rent with reference to the existing rent and the decrease or increase in the area of the holding.
(2) In any proceedings for enhancement of fixed money rent or the bighori determined under section 151 on the ground that the productive power of the holding has increased by an improvement effected by, or at the expense of, the landholder or for abatement of rent on the ground that such power has decreased by any cause beyond the control of the tenant, the court shall enhance or abate the rent with reference to the existing rent and the increase or decrease of the productive power.
(3) In an application for the determination of the fixed money rent of a portion of a holding under section 157, the court shall determine the rent with reference to the rent payable before ejectment or surrender and the loss of area due to such ejectment or surrender.