12. Organic manure in the form of slurry, poultry manure or liquid digested sewage sludge shall not be applied to any land which has a sandy or shallow soil—
(a)between 1st September and 1st November in any year where the land is in grass or is to be sown with an autumn sown crop;
(b)between 1st August and 1st November in any year in any other case.