Section 21. Reduction of rents referred to in the last foregoing section.

When the land, or any part of the land, held by a tenant having a right of occupancy to whom the last foregoing section applies ceases to be irrigated or flooded, the rent payable in respect of the land or part may be reduced to the share or rates, or with reference to the rent in gross, as the case may be, paid by tenants, having a similar right of occupancy for unirrigated or unflooded land of a similar description and with similar advantages.